<figure><img src="image_20.png" /><figcaption>**FIGURE 3** Frequency of mask-related dyspnoea. a) Comparison of respiratory healthy and respiratory disease populations (answer no or yes, respectively, to "treated for chronic respiratory disease or congestive heart failure" question). b) Comparison of respiratory healthy (RH-family*) and RH-family~ populations (answer no or yes, respectively, to "close relatives treated for chronic respiratory disease or congestive heart failure" question). Note that during intense effort, 55.5% of the respondents reported never wearing a mask; among the 44.5% who wore a mask during intense effort, 59.0% reported mask-related dyspnoea. Horizontal bars represent the mean value in the whole study sample. *: p<0.05; **: p<0.01; ***: p<0.001.</figcaption></figure>

0.25–0.75) (figure 4). The only variable associated with the intensity of mask-related dyspnoea at rest was “air hunger” (OR 2.82, 95% CI 1.74–4.53) (figure 4). For mask-related dyspnoea intensity during moderate effort, independently associated variables were age <65 years (OR 1.62, 95% CI 1.02–2.56), active smoking (OR 1.66, 95% CI 1.01–2.75), removing the mask to breathe more easily (OR 2.62, 95%

<table><caption>**TABLE 2** Dyspnoea ratings according to circumstances and respondent categories (for a better apprehension of the differences, the corresponding distributions are provided in supplementary figure S1)</caption><thead><tr><th></th><th>Whole population</th><th>Respiratory healthy group*</th><th>Respiratory disease group*</th><th>p-value*</th><th>Respiratory healthy group</th><th>RH-family<sup>**</sup></th><th>RH-family<sup>**</sup></th><th>p-value*</th></tr></thead><tbody><tr><td>Subjects</td><td>1012</td><td>860 (85)</td><td>152 (15)</td><td></td><td>846<sup>**</sup></td><td>726 (86)</td><td>120 (14)</td><td></td></tr><tr><td>Dyspnoea rating at rest</td><td>7.00 (2.00–10.00)</td><td>7.00 (2.00–10.00)</td><td>8.00 (2.00–10.00)</td><td>0.035</td><td>7.00 (2.00–10.00)</td><td>7.00 (2.00–10.00)</td><td>7.50 (3.00–10.00)</td><td>0.285</td></tr><tr><td>Dyspnoea rating during moderate exertion</td><td>7.00 (1.00–10.00)</td><td>7.00 (1.00–10.00)</td><td>8.00 (2.00–10.00)</td><td>0.020</td><td>7.00 (1.00–10.00)</td><td>7.00 (1.00–10.00)</td><td>7.50 (3.00–10.00)</td><td>0.111</td></tr><tr><td>Dyspnoea rating during sport<sup>**</sup></td><td>8.00 (1.00–10.00)</td><td>8.00 (1.00–10.00)</td><td>8.00 (5.00–10.00)</td><td>0.481</td><td>8.00 (1.00–10.00)</td><td>8.00 (1.00–10.00)</td><td>9.00 (3.00–10.00)</td><td>0.054</td></tr></tbody></table>

Data are presented as n, n (%) or median (range), unless otherwise stated. Bold type represents statistical significance. #: answered “no” to “treated for chronic respiratory disease or congestive heart failure”; *: answered “yes” to “treated for chronic respiratory disease or congestive heart failure”; #: corrected for multiple comparisons (n=69); #: answered “no” to “close family members treated for chronic respiratory disease or congestive heart failure”; #: answered “yes” to “close family members treated for chronic respiratory disease or congestive heart failure”; #: n=553 declared never wearing a face mask during this type of activity; #: n=14 declared never wearing a mask.
a) Reporting mask-induced dyspnoea at rest or during moderate effort

<figure><img src="image_21.png" /></figure>

b) Dyspnoea intensity at rest

<figure><img src="image_22.png" /></figure>

c) Dyspnoea intensity during moderate effort

<figure><img src="image_23.png" /></figure>

**FIGURE 4** Variables independently associated with reporting a) mask-related dyspnoea at rest or during moderate effort, and dyspnoea intensity b) at rest or c) during moderate effort, according to multivariate analysis. a) Relative being treated for respiratory disease p=0.008, facial mask as protection for others p=0.002, removing face mask p<0.001; b) best sensory descriptor p<0.001; c) age p=0.041, smoking p=0.041, removing face mask p<0.001, best sensory descriptor p<0.001, best affective descriptor p=0.044.

CI 1.52–4.51) and using air hunger (OR 2.03, 95% CI 1.38–2.97) and anxiety (OR 1.59, 95% CI 1–2.53) as descriptors (figure 4). The results of the Lasso regressions were consistent with those provided by the stepwise regressions in terms of the variables and the coefficients (supplementary table S5).

Attitude changes

In the respiratory healthy population, 46.9% of respondents answered “more than before” to “have you become more aware of the importance of your breathing”; 51.2% to “the privilege of not having to worry about one’s breathing”; and 30.4% to “fearing a respiratory illness”. These changes were significantly associated with being female, reporting dyspnoea at rest and considering face masks effectively protective
(supplementary figure S3 and supplementary table S5). 41% of respiratory healthy respondents answered "more than before" to "have you become more aware of what people with respiratory illnesses may experience" (see associated variables in supplementary figure S3 and supplementary table S5).

Discussion

Main findings

As hypothesised, this study shows that wearing a face mask as a barrier measure is frequently associated with dyspnoea, and that this depends on activity level and health status (respiratory disease respondents experienced dyspnoea more often). The term “dyspnoea” is appropriate: dyspnoea is defined as “breathing discomfort” [1], or the conscious perception of an abnormal breathing activity associated with a negative emotional charge, which is precisely what the survey respondents reported. Indeed, they predominantly chose “air hunger” to characterise mask-related breathing difficulties. This is the main descriptor used by dyspnoeic patients [23–25] and the most strongly associated with anxiety or fear [2, 26, 27]. However, contrary to patients, the respondents did not rank anxiety first, but favoured “anger” and “frustration”. This may relate to the knowledge that mask-related dyspnoea is transitory, is not a marker of disease and is possible to control through mask removal. Dyspnoeic patients lack such control.

The respondents ranked breathing difficulties first among mask-related inconveniencies (on a par with “glasses steaming up”, the importance of which probably reflects the general public’s concern for vision health [28]) and the “respiratory connotation” semantic cluster was the most prevalent. Nevertheless, mask-related dyspnoea did not negatively impact reported compliance with mask-wearing recommendations, which was extremely high, noting that at the time of the study masks were legally prescribed in public places in the country. The proportion of respondents reporting removing their mask to breathe more easily (75.4%) was less than the proportion reporting wearing a mask (94.7%). Positive mask-wearing drivers (compliance with rules, belief in protective value) were thus more potent than negative ones. Notably, believing that face masks effectively protect others from contamination was negatively associated with reporting mask-related dyspnoea. This observation suggests that positive messages about the efficacy of face masks should effectively overcome putative dyspnoea-driven reluctance.

Strength and weaknesses

The study followed state-of-the-art polling methodology, under the auspices of an internationally renowned
specialised organisation (IFOP). The quota sampling method ensured demographic representativeness [29],
which was further confirmed by the 15% proportion of respondents reporting being treated for a chronic
respiratory disease or cardiac insufficiency (and the repartition of the corresponding diseases (table 1)).
Indeed, this figure does correspond to French epidemiological data ("Comparison of the frequency of
chronic respiratory diseases reported by respondents to the survey with French epidemiological data" in the
supplementary material). In the same vein, the 95% proportion of our respondents reporting wearing a face
mask "always" or "often" when mandatory may seem high, but it is only slightly higher than the
nationwide proportion recorded at the same time by the French national institute for public health
(COVIPREV programme, www.santepubliquefrance.fr/). This suggests behavioural representativeness as
well as demographic representativeness. Of note, given recently voiced concerns about stepwise regressions
[30], we corroborated this approach by using a Lasso penalised regression. The coherence of the
corresponding two sets of coefficients lends credibility to the results. Nevertheless, we acknowledge that
the study has limitations. Some are inherent to its unsupervised and self-declarative nature. For example,
we did not seek any form of corroboration of the diagnostic of chronic respiratory diseases. We did not
determine the proportion of respondents who had suffered from COVID-19 (this should have been ~10%,
including asymptomatic forms, at the time of the survey [31]), and we did not ask any questions about
mental health, in general or in relation to mask wearing. Furthermore, the study does not describe the
impact of masks on activity, particularly in the respiratory disease population, and no information was
gathered to evaluate mask misuse (e.g. not covering the nose).

Meaning

This study provides insights into dyspnoea invisibility. Firstly, as hypothesised, dyspnoea was described as
very intense by healthy individuals. Ratings reported by respiratory healthy respondents for dyspnoea at
rest (median 7) are higher than those considered intolerable by hospitalised dyspnoeic patients (ratings of
≥4 are unacceptable for 54% of hospitalised dyspnoeic patients) [25]. Yet several studies showed that
masks do not impair laboratory-evaluated cardiorespiratory performance [12, 32]. We believe that the very
high dyspnoea ratings provided by "respiratory healthy" people illustrate an incapacity to imagine what
"the worst possible breathing difficulties" could be, namely what disease-related dyspnoea truly represents
for afflicted patients. We also believe that this incapacity relates to the lack of previous dyspnoeic
experiential baggage. The contrast between physiological data (insignificant impact of face masks on exercise [32–34]) and psychophysiological data (intense mask-related dyspnoea in this study) exemplifies the rift between “measurement” and “experience” that contributes to dyspnoea invisibility [35]. Secondly, as hypothesised, our data indicate that having a close relative treated for a chronic respiratory disease can influence one’s relationship to breathing. Likewise, the RH-family⁻ group was better aligned with the respiratory disease group than with the RH-family⁻ group regarding dyspnoea frequency. RH-family⁺ respondents more frequently chose “fear” to describe mask-related dyspnoea than RH-family⁻ respondents (16.8 versus 7.6%; p=0.012). In addition, belonging to the RH-family⁻ group was independently associated with reporting dyspnoea at rest and during moderate effort. These findings are consistent with experimental data indicating that seeing someone experience dyspnoea induces dyspnoea and malaise [36, 37], and with clinical data indicating that seeing a relative die with respiratory difficulties is associated with delayed and difficult grieving [38]. By symmetry, this illustrates the rarity of direct or indirect exposure to dyspnoea in the general population. Thirdly, in line with our predictions [14], a large number of respondents answered that wearing a mask had made them aware of the good fortune of not ordinarily being continually preoccupied by their own breathing and had changed both their degree of preoccupation with their own breathing and their perception of the experience of patients with chronic respiratory disease. We acknowledge that we cannot exclude that fear of the disease also had a role in the reported attitude changes, keeping in mind that our questions were carefully phrased to relate putative attitude changes to the wearing of face masks.

### Conclusions and perspectives

From an immediately practical point of view, the frequency and the characteristics of face mask-related dyspnoea call for specific communication actions that should primarily target patients suffering from cardiorespiratory illnesses. For these patients, it should be made clear that face masks can worsen dyspnoea, but that this phenomenon is not threatening and can be controlled: it therefore should not cause people to deprive themselves of an effective protection. Of note, patients suffering from cardiorespiratory illnesses could also be the primary focus of studies evaluating masks designed to make breathing easier. The same message (possibility of breathing discomfort but not threatening and controllable and not worth risking catching or disseminating the virus) should be addressed to the general population.

The survey shows that mask removal is commonly used to relieve dyspnoea. To reduce misuse (e.g. not covering the nose), brief temporary mask removal should be promoted as a guilt-free action, provided recommendations similar to those regarding coughing and sneezing (for example, something like “in the event of breathlessness, find an isolated location in a well-ventilated environment or outside and remove the mask briefly”).

Most importantly, 95% of the respondents reported wearing masks, and 70% reported mask-related dyspnoea. This equates to ~35 million French adults discovering what it means to be bothered by one's breathing because of a constraint. This represents a mass experiential discovery of dyspnoea with the positive consequence of making dyspnoea more visible to those free of respiratory diseases. We believe that this provides the respiratory health community with leverage to sensitise the public to respiratory health better and that face mask-related dyspnoea could and should be used positively as a “respiratory communication” tool.

**Acknowledgements:** The authors are indebted to Andrew Lane (Lane Medical Writing, Lyon, France), for his help with the manuscript. They thank Elizabeth Hewes (Lyon, France) for producing the English translation of the questionnaire (supplementary material). Both were funded by Sorbonne Université, Paris, France. The authors also thank the French "Fondation du Souffle" for its interest in and support for the study.

Data from the survey and the corresponding dictionary will be made available to researchers presenting a research project reasonably in phase with the content of the study.

**Conflict of interest:** L. Serresse has nothing to disclose. N. Simon-Tillaux has nothing to disclose. M. Decavèle has nothing to disclose. F. Gay has nothing to disclose. N. Nion has nothing to disclose. S. Lavault has nothing to disclose. A. Guerder has nothing to disclose. A. Châtelet is an employee of the IFOP polling institute. F. Dabi is an employee of the IFOP polling institute. A. Demoule reports grants, personal fees and non-financial support from Philips, Respinor and Lungpacer, personal fees from Baxter, Getinge, Lowenstein and Gilead, personal fees and non-financial support from Fisher & Paykel, grants from French Ministry of Health, outside the submitted work. C. Morélot-Panzini reports personal fees for lectures and board membership from AstraZeneca, GSK, SOS Oxygène, ADEP, ISIS, Resmed, Chiesi, Menarini, Vivisol, Air Liquide, Lowenstein, Fisher & Paykel, outside the submitted work.
C. Moricot has nothing to disclose. T. Similowski reports personal fees from AstraZeneca France, Boehringer Ingelheim France, TEVA France, Chiesi France, Lungpacer Inc. and ADEP Assistance, personal fees and non-financial support from Novartis France, grants from Air Liquide Medical Systems, outside the submitted work.

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« Involve me and I learn »

À partir du constat de l'efficacité expérientielle d'une dyspnée « subie » issu du travail précédent, nous avons voulu évaluer la portée pédagogique d'une expérience de dyspnée « choisie », dans le but de l'utiliser pour sensibiliser de futurs soignants à la réalité de l'expérience vécue par les patients dyspnéiques.

Cette démarche s'inscrit dans une perspective de soins plus large sous-tendue par l'hypothèse qu'une meilleure compréhension de la dyspnée chez les soignants permettrait de réduire l'invisibilité de la dyspnée et d'améliorer la prise en charge des patients qui en souffrent.

Dans ce projet expérientiel à visée pédagogique, nous avons testé l'hypothèse plus spécifique qu'exposer des étudiants en médecine à une dyspnée améliorerait leur compréhension de la dyspnée ainsi que la manière dont elle peut être vécue par les patients.

Cette étude avait également comme objectif d'évaluer la faisabilité et l'appréciation par les étudiants d'un apprentissage expérientiel de la dyspnée.

Pour ce faire, nous nous sommes appuyés sur les principes à l'origine de l'apprentissage expérientiel.

Selon Dewey, psychologue et philosophe américain très investi dans la pédagogie, l'apprentissage est un processus continu et profondément ancré dans l'expérience de l'être humain au cours sa vie.

C'est aussi un mode d'adaptation de l'individu à son environnement et un instrument de développement de sa personnalité. L'expérience fait donc pleinement partie du mécanisme d'apprentissage et l'enseignement devrait s'appuyer davantage dessus [169].

Schön poursuit cette même analyse, en se focalisant sur la formation professionnelle, en explorant ce qui est parfois qualifié de formation « sur le tas ». Dans son ouvrage *Le praticien réflexif. À la recherche du savoir caché dans l'agir professionnel* », il souligne l'importance voire le caractère indispensable du « savoir d'expérience ».

Les apprentissages théoriques, s'ils restent évidemment nécessaires, ne suffisent pas pour acquérir l'ensemble des savoirs professionnels nécessaires [170].

Même si les médecins ne figurent pas dans les professions étudiées dans son ouvrage, on peut supposer que ses conclusions restent pertinentes pour toute formation aux métiers de la santé.
Ce rôle prédominant que joue l'expérience dans le processus d'apprentissage bénéficie aujourd'hui d'une reconnaissance forte grâce aux travaux de Kolb. Ce pédagogue, qui a fait de l'apprentissage expérientiel le sujet principal de ses travaux, écrivait déjà en 1975 :

> « The experiential learning model, however, emphasizes that learning and change result from the integration of concrete emotional experiences with cognitive processes: conceptual analysis and understanding. Thus, learning involves the labelling or relabelling of immediate existential experience. [...]. The experiential learning model depicts learning as a process of conflict confrontation and resolution among four basic adaptative modes or ways of relating to the world. Concrete experience vs abstract conceptualization and active experimentation vs reflective observation» [171].

Pour Kolb, l'apprentissage est donc un processus dynamique et cyclique qui implique quatre fonctions principales : sentir, percevoir, penser et agir.

Il a ainsi développé, dans les années 80, un modèle du cycle d'apprentissage expérientiel (« Experiential Learning Model ») composé de quatre temps, correspondant chacun à une manière distincte d'utiliser son expérience. Il considère qu'un apprentissage n'est complet que lorsque ces quatre phases sont vécues [172].

Ce modèle a continué d'évoluer et schématisé de la façon suivante dans une de ses publications récentes [173].

<figure><img src="image_24.png" /></figure>

Extrait: Kolb et al. Experiential Learning Theory: A Dynamic, Holistic Approach to Management Learning, Education and Development. Handbook of Management Learning, Education and Development (2008).
L'application de ce cycle d'apprentissage expérientiel à notre problématique de l'invisibilité de la dyspnée pourrait se traduire comme suit :

<figure><img src="image_25.png" /></figure>

Nous avons donc conçu une session d'enseignement selon le cycle d'apprentissage expérientiel de Kolb pour tester notre hypothèse selon laquelle, la mise en place d'un cours sur la dyspnée comprenant une exposition personnelle à une dyspnée expérimentale permettrait aux étudiants d'associer leur conception abstraite de la dyspnée à une représentation sensorielle et émotionnelle propre.

L'influence sur les processus cognitifs de cette expérience de dyspnée, vécue « dans son propre corps », pourrait modifier leur perception de celle vécue par les patients dyspnéiques.

Cette hypothèse s'appuie sur la théorie de la cognition incarnée, ou « embodiment », né au début des années 1980 en tant que programme de recherche en sciences cognitives visant à réévaluer la place du corps dans l'ensemble des phénomènes cognitifs (perception, action, émotion, sentiment, langage, conceptualisation, mémoire, etc.).

Dans cette théorie, dont l'un des sources d'inspiration est la phénoménologie, la cognition n'est pas considéré de façon isolée, mais toujours à la fois « embodied », à savoir inscrite dans un corps et influencée par lui, et « embedded », c'est-à-dire située dans un environnement (notamment culturel et social) dont elle dépend significativement [174].

Après l'avis favorable d'un comité d'éthique de la recherche, 55 internes de médecine d'urgence ont participé à cette étude.
Le déroulement de l'enseignement comportait les séquences suivantes :

1) Introduction, présentation du cours et de l'étude, recueil de la non-opposition après remise d'une note d'information écrite.

2) Passation des questionnaires (caractéristiques individuelles, formation universitaire, antécédents personnels, attitudes et croyances concernant la dyspnée et la douleur, auto-évaluation de leur degré d'empathie, satisfaction à l'égard de l'enseignement antérieur sur la dyspnée).

3) Présentation des trois dispositifs expérimentaux d'auto-induction de la dyspnée.

<figure><img src="image_26.png" /></figure>

4) Démonstration de l'auto-induction de la dyspnée expérimentale par l'enseignant à l'aide d'une poche de réinspiration de CO2 avec affichage continu et visible des étudiants de la concentration en CO2 dans l'air inspiré et expiré à l'aide d'un capnomètre infrarouge.

5) Réaction psychophysologique à la dyspnée de l'enseignant.

6) Auto-induction de la dyspnée expérimentale par les participants, assignés au hasard à l'une des trois modalités d'auto-induction de la dyspnée :

a) Réinspiration de CO2 : les participants, munis d'un pince-nez, devaient respirer dans une poche de réinspiration de 2 L directement reliée à la bouche.

b) Charge de seuil inspiratoire : les participants, munis d'un pince-nez, étaient reliés à une valve de seuil à ressort (charge de 50 cmH20) équipée d'une valve à 2 voies pour laisser l'expiration libre.

c) Respiration à la paille : les participants, munis d'un pince-nez, devaient respirer à l'aide d'un tube en plastique de 3mm de diamètre intérieur directement relié à leur bouche et fournissant une résistance inspiratoire et expiratoire.
7) Réactions psychophysio logiques à la dyspnée expérimentale.

8) Cours théorique sur la physiopathologie de la dyspnée, son impact clinique et sa prise en charge.

9) Évaluation immédiate et à un an.

Dans ce groupe de participants, la médiane d'âge était de 26 ans (IQ [26-27]) et le sex-ratio équilibré (47% d'hommes). La fréquence d'une expérience antérieure de douleur était significativement supérieure à celle de dyspnée (85% vs 31%, p<0.001). Le degré d'empathie déclaré était significativement plus important chez les femmes que chez les hommes (8 [7-8] vs 7 [6-8], p=0.032).

Leurs attitudes et croyances face à la douleur et la dyspnée sont en adéquation avec les données de la littérature présentées au début de ce travail. Chez nos participants, la prise en charge à visée symptomatique de la dyspnée (notamment par la prescription d'opioïdes) est plus rare que celle de la douleur.

Toujours en adéquation avec la littérature, ils sont 82% à avoir ressenti un malaise et une sensation de dyspnée en observant la dyspnée de l'enseignant. Cette « vicarious dyspnea » était d'autant plus fréquente et intense que l'empathie déclarée était élevée.

<table><thead><tr><th>« vicarious dyspnea »</th><th>Empathie élevée</th><th>Empathie faible ou modérée</th><th></th></tr></thead><tbody><tr><th>Fréquence</th><td>88%</td><td>62%</td><td>p=0.030</td></tr><tr><th>Intensité</th><td>4 [3-5]</td><td>2 [0-5]</td><td>p=0.049</td></tr></tbody></table>

Une auto-induction de dyspnée a ensuite été réalisée par 53 étudiants (2 refus de participation). L'intensité de la dyspnée induite a été évaluée à 6 ([5-8]) sur une échelle allant de 0 à 10. Le caractère désagréable de l'expérience de dyspnée a été évalué à 8 ([6-9]).

Les qualificatifs sensoriels le plus fréquemment ou le plus intensément rapportés étaient la « sensation d'effort pour respirer » et de « soif d'air ». Les descripteurs émotionnels les plus fréquents étaient l'anxiété et la frustration.

Nous pouvons donc affirmer l'existence d'une véritable expérience de dyspnée, même si celle-ci n'a pas l'ensemble des caractéristiques d'une dyspnée pathologique au premier plan desquelles figure le caractère incontrôlable.
Malgré tout, cette expérience permet, d'après les participants de cette étude, de mieux se représenter ce qu'est la dyspnée et de mieux comprendre les patients qui en souffrent.

Ces résultats semblent perdurer dans le temps comme le suggère l'évaluation à un an à laquelle ont répondu 28 des 53 participants de l'étude.

Des résultats similaires ont été retrouvés dans un second groupe de 50 étudiants l'année suivante, ce qui nous permet de renforcer la validité de nos conclusions.

L'expérience d'un symptôme ou d'un trouble rencontré par les patients, grâce à des moyens simples (comme c'est le cas ici) ou plus complexes (outils de simulation) apparaît de plus en plus comme une manière efficace d'améliorer la compréhension du vécu des patients par les professionnels de santé. Le champ d'application est large et des résultats préliminaires existent par exemple pour les hallucinations auditives ou les troubles visuels.

C'est dans cette perspective que nous avons exploré la faisabilité, l'acceptabilité et l'efficacité de ce modèle pédagogique à notre problématique de la dyspnée et de son invisibilité.

Les résultats sont encourageants et appellent à poursuivre dans cette voie.

Un des mécanismes sous-jacents de l'efficience de cette approche expérientielle semble être l'influence de l'expérience de la dyspnée sur l'empathie des (futurs) soignants face à un patient dyspnéique.

Reste donc à confirmer et estimer cet impact sur l'empathie et à évaluer l'effet de la sollicitude empathique sur le vécu des patients souffrant de dyspnée.

En tout état de cause, cette approche pédagogique expérientielle nous parait être une réelle opportunité pour améliorer la qualité de la relation médecin-malade, de manière générale et dans le cadre particulier de la dyspnée.

Cette étude a fait l'objet d'une publication dans la revue *Medical Education Online* <fnref n="13" />.

<footnote n="13">¹³ Decavèle M, Serresse L, Gay F, Nion N, Lavault S, Freund Y, Niérat MC, Steichen O, Demoule A, Morélot-Panzini C, Similowski T. 'Involve me and I learn': an experiential teaching approach to improve dyspnea awareness in medical residents. Med Educ Online. 2022 Dec;27(1):2133588. doi: 10.1080/10872981.2022.2133588.</footnote>
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# 'Involve me and I learn': an experiential teaching approach to improve dyspnea awareness in medical residents

Maxens Decavèlea,b, Laure Serresse a,c,*, Frédérick Gayd, Nathalie Nione, Sophie Lavaulte, Yonathan Freunde,*, Marie-Cécile Niérat a, Olivier Steichenh,j,1, Alexandre Demoulea,b, Capucine Morélot-Panzinia,j,# and Thomas Similowski a,e,#

aSorbonne Université, INSERM, UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France; bAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service de Médecine Intensive, Réanimation, Département R3S, Paris, France; cAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Unité Mobile de Soins Palliatifs, Paris, France; dAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Laboratoire de parasitologie-mycologie, Paris, France; eAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Département R3S, Paris, France; fAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service d'accueil des urgences, Paris, France; gSorbonne Université, INSERM, UMRS 1166, IHU ICAN, Paris, France; hAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Tenon, Service de médecine interne, Paris, France; iSorbonne Université, INSERM, UMRS 1142 LIMICS, Paris, France; jAP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service de Pneumologie, Département R3S, Paris, France

## ABSTRACT

**Background:** Dyspnea is a frightening and debilitating experience. It attracts less attention than pain ('dyspnea invisibility'), possibly because of its non-universal nature. We tested the impact of self-induced experimental dyspnea on medical residents.

**Materials and Methods:** During a teaching session following the principles of experiential learning, emergency medicine residents were taught about dyspnea theoretically, observed experimental dyspnea in their teacher, and personally experienced self-induced dyspnea. The corresponding psychophysiological reactions were described. Immediate and 1-year evaluations were conducted to assess course satisfaction (overall 0–20 grade) and the effect on the understanding of what dyspnea represents for patients.

**Results:** Overall, 55 emergency medicine residents participated in the study (26 men, median age 26 years). They were moderately satisfied with previous dyspnea teaching (6 [5–7] on a 0–10 numerical rating scale [NRS]) and expressed a desire for an improvement in the teaching (8 [7–9]). Immediately after the course they reported improved understanding of patients’ experience (7 [6–8]), which persisted at 1 year (8 [7–9], 28 respondents). Overall course grade was 17/20 [15–18], and there were significant correlations with experimental dyspnea ratings (intensity: r = 0.318 [0.001–0.576], p = 0.043; unpleasantness: r = 0.492 [0.208–0.699], p = 0.001). In multivariate analysis, the only factor independently associated with the overall course grade was 'experiential understanding' (the experimental dyspnea-related improvement in the understanding of dyspneic patients' experience). A separate similar experiment conducted in 50 respiratory medicine residents yielded identical results.

**Conclusions:** This study suggests that, in advanced medical residents, the personal discovery of dyspnea can have a positive impact on the understanding of what dyspnea represents for patients. This could help fight dyspnea invisibility.

## ARTICLE HISTORY

Received 20 July 2022
Revised 30 September 2022
Accepted 5 October 2022

## KEYWORDS

Experiential learning;
dyspnea; experimental
dyspnea; personal
experience; medical trainees;
medical residents;
symptoms experience;
respiratory suffering;
empathy enhancing

## Introduction

Dyspnea is a ubiquitous symptom of cardiac or respiratory dysfunction and of many other disorders. It stems from an upsetting or distressing awareness of breathing sensations [1] that has been defined as 'a subjective experience of breathing discomfort made of various sensations that can vary in intensity' [1]. Acute dyspnea is a frightening experience that is very common, being reported by more than 15% of patients at hospital admission [2], 50% of patients seen in the emergency room [2],

and up to 50% of critically ill mechanically ventilated patients [3,4]. It independently predicts hospital death [5] and post-intensive care stress disorders [3]. Chronic dyspnea, in turn, shapes the lives of affected patients, for whom it represents a major physical, psychological, and social burden. Given the epidemiology of chronic respiratory diseases, congestive heart failure and neuromuscular disorders, chronic dyspnea affects millions worldwide.

Dyspnea, however, attracts much less attention from professional caregivers than, for example, pain

CONTACT Thomas Similowski

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thomas.similowski@upmc.fr

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Département R3S, Hôpital Pitié-Salpêtrière, 47-83 boulevard de l'Hôpital, Paris

Maxens Decavèle and Laure Serresse are co-first authors
Capucine Morélot-Panzini and Thomas Similowski are co-last authors

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Supplemental data for this article can be accessed online at https://doi.org/10.1080/10872981.2022.2133588

© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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[6,7]. Dyspneic patients report an insufficient understanding of their experience by others that aggravates their suffering [8]. For their part, caregivers find it difficult to talk with their patients about dyspnea [9]. This defines ‘dyspnea invisibility’ [10], which limits access to due care [11] and therefore raises human rights issues [12]. Among many factors, the lack of universality of dyspnea can contribute to dyspnea invisibility. ‘Pathological breathlessness’[13], i.e., the anxiogenic breathing difficulties due to a constraint that cannot be controlled, as opposed to the non-threatening ‘healthy breathlessness’ that occurs during sport, is a far less common experience than pain. The absence of a personal reference system can make it difficult to understand the suffering associated with dyspnea and could lead to empathic distress and avoidance behaviors [14]. Furthermore, it has been reported that caregivers who witness troubled breathing can themselves experience so-called ‘vicarious dyspnea’ and malaise [15,16]. In the case of medical or paramedical trainees, insufficient dyspnea-targeted teaching is another factor that can play a role in dyspnea invisibility.

We hypothesized that the implementation of a dyspnea course for medical residents, designed according to Kolb's experiential learning cycle [17] and including personal exposure to experimental dyspnea, would make them associate the concept of dyspnea with precise sensory and emotional mental imagery (embodied cognition [18]) and, therefore, would change their perception of the lived experience of dyspneic patients. This hypothesis was based on anecdotal observations of the impact of laboratory dyspnea on medical personnel (after his first personal

encounter with air hunger, a young intensivist from our group once said that he would ‘never again tell an agitated [dyspneic] mechanically ventilated patient to calm down’ [19]). A population survey also demonstrated that the breathing discomfort associated with COVID-19 face masks can enhance the general public understanding of the lived experience of chronic respiratory disease patients [20]. More generally, the exposure of medical trainees to symptoms leads to improved empathy toward patient experiences experiential learning, see [21–23].

To test this hypothesis, we designed a teaching session (Figure 1), during which residents were taught about dyspnea from a theoretical point of view (‘tell me’), confronted by the experimental dyspnea of a healthy subject (‘show me’), and were themselves exposed to short bouts of dyspnea induced by different means (‘involve me’).

## Materials and methods

### Design and setting

This pilot study was designed by an intensivist (MD), a palliative care specialist (LS), a psychologist (SL), and two respiratory physicians (CMP, TS), all of whom were engaged in academic teaching and involved in clinical and experimental dyspnea research, and three of whom (MD, LS and CMP) were qualified in medical pedagogy. The two main investigators (MD and LS) conducted the study at the Faculty of Medicine, Sorbonne Université, Paris, France, in the form of a 90 minute session with a follow-up at 1 year. The study was first conducted in a homogeneous group of residents in the

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**Figure 1.** Course sequence. The design of the course was based on the four-stage process of Kolb's experiential learning cycle [17], the students' knowledge about dyspnea being enriched through personal experience of dyspnea. After being engaged in an actual dyspnea experience (step 1: concrete experience), students were invited to reflect on what happened to them during this experience (step 2: reflection/observation). A theoretical course then intended to help the students amalgamate their personal experience and theoretical concepts (step 3: conceptualization/explanation). Finally, immediate, and delayed evaluations assessed the change in the students' beliefs and attitudes about dyspnea (step 4: active experimentation/projection).
emergency medicine specialization cursus who had completed 8 years of medical studies and were entering their ninth and final year. Corroboration of the results was then sought for in a second group of respiratory medicine residents. The first group was included in January 2020 and the second group was in April 2022, the 2-year period between groups being due to the COVID-19 pandemic.

The study was approved by the university ethical committee (Comité d'Éthique de la Recherche, Sorbonne Université, Paris, France, # CER 2020-2). Regarding information, the participants were provided with a detailed description of the study. Its background and design were first explained orally, after which the residents were given a printed information leaflet. They were clearly informed that the experiential part of the course involved enduring some degree of physical and psychological discomfort (e.g., transient headache or anxiety), that no residual untoward effects were to be expected, and that they would have full control of their dyspnea through the possibility of stopping the experiment at any moment without any justification. They were also informed that, in the event of abnormally strong or residual psychological reactions, they could contact the investigators or a psychologist (contact information provided in the leaflet), for access to support at any time. Regarding consent, the participants were told orally and in writing that they were free not to participate in any part of the course (with no questions asked) and, in this case, to either observe or

leave (without any consequence on their marks or graduation). Taking part to the course in general and its experiential part in particular was therefore considered as explicit consent.

## Teaching sequence

The course was organized as follows (Figure 1):

1) Introductory remarks, including the terms of the upcoming course (5 minutes);

2) Completion of a generic questionnaire exploring individual characteristics, academic training, personal history, attitudes, and beliefs regarding dyspnea and pain, and satisfaction with previous dyspnea teaching; (5 minutes; Table 1 and electronic supplement ES1); the participants were also asked to evaluate their self-perceived degree of empathy on a 10 cm visual analogue scale (from 'not empathetic at all' to 'extremely empathetic'); participants who rated their self-perceived level of empathy 7 or more were allocated to a 'high empathy' group, those who gave a rating of 6 or less were allocated to a 'low empathy' group;

3) Presentation of the experimental devices (3 minutes; see below);

4) Demonstration of self-induction of experimental dyspnea by the teacher using a CO₂ rebreathing bag (2 minutes); the end-tidal partial pressure of CO₂ was measured continuously using an infrared

<table><caption>Table 1. Data collected at the different time points of the dyspnea course.</caption><thead><tr><th colspan="2">Before the beginning of the dyspnea course</th></tr></thead><tbody><tr><td colspan="2"><strong>Generic student questionnaire (electronic supplement ES1)</strong></td></tr><tr><td colspan="2">Age, gender, personal medical history</td></tr><tr><td>Personal experience of pain</td><td>• yes/no; if yes 0-10 NRS</td></tr><tr><td>Personal experience of 'pathological breathlessness'</td><td>• yes/no; if yes 0-10 NRS</td></tr><tr><td>Self-perceived degree of empathy</td><td>• 0-10 NRS <sup>(1)</sup></td></tr><tr><td>Dyspnea teaching received during medical studies</td><td>• number of courses<br>• 0-10 NRS rating of overall satisfaction<br>• 0-10 NRS rating of desire for more teaching</td></tr><tr><td>Self-perceived confidence in managing pain<br>upon emergency room admission</td><td>• 0-10 NRS</td></tr><tr><td>Self-perceived confidence in managing dyspnea<br>upon emergency room admission</td><td>• 0-10 NRS</td></tr><tr><td>Attitudes and habits regarding the management of dyspnea and pain in clinical practice</td><td>See details in ES1</td></tr><tr><td colspan="2"><strong>Psychophysiological reactions to the teacher's dyspnea (electronic supplement ES2)</strong></td></tr><tr><td>Intensity of the teacher's dyspnea?</td><td>• 0-10 NRS</td></tr><tr><td>Did you experience dyspnea yourself<br>while watching the teacher's dyspnea?</td><td>• yes/no<br>• if yes, 0-10 NRS</td></tr><tr><td colspan="2"><strong>Psychophysiological reactions to experimental dyspnea (electronic supplement ES3)</strong></td></tr><tr><td>Intensity of your dyspnea?</td><td>• 0-10 NRS</td></tr><tr><td>Multidimensional Dyspnea Profile <sup>(2)</sup> (French version) <sup>35</sup></td><td>• see details in ES3</td></tr><tr><td>Verbatim (write two sentences summarizing your experience)</td><td>• lexicometric analysis</td></tr><tr><td colspan="2"><strong>At the end of the teaching session (electronic supplement ES4)</strong></td></tr><tr><td>To what extent did your personal experience of dyspnea make you better understand what dyspneic patients feel?</td><td>• 0-10 NRS</td></tr><tr><td>Grade the course in general</td><td>• 0-20 mark</td></tr><tr><td colspan="2"><strong>One year after the teaching session (electronic supplement ES5)</strong></td></tr><tr><td>Online 4 questions survey</td><td>• see details in ES5</td></tr><tr><td>Three-word verbatim to describe the impact of the course</td><td></td></tr></tbody></table>

NRS, numerical rating scale

<footnote><sup>(1)</sup> participants who rated their self-perceived level of empathy 7 or more were allocated to a 'high empathy' group, those who gave a rating of 6 or less to a 'low empathy' group.</footnote>

<footnote><sup>(2)</sup> a multidimensional instrument measuring the intensity of dyspnea unpleasantness (A1) and the sensory (SQ) and affective (A2) dimensions of dyspnea; (electronic supplement, ES3).</footnote>
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capnometer (MicroStream®, Medtronic, Dublin, Ireland) with the display permanently visible to the participants;

5) Psychophysiological reaction to the teacher's dyspnea (1 minute, Table 1 and electronic supplement ES2);

6) Self-induction of experimental dyspnea by the participants (2 minutes; a large screen stopwatch visible to the participants was placed on the teacher's desk); the participants were randomly assigned to one of three modalities to self-induce dyspnea (we only had a stock of ten ITL);

a) CO₂ rebreathing: the participants were asked to breathe in a 2 L rebreathing bag (single-use reservoir bag, Intersurgical, Wokingham, Berkshire, UK) directly connected to the mouth, with a nose clip on;

b) *Inspiratory threshold loading*: the participants were connected to a spring-loaded threshold valve (50 cmH₂o load) fitted with a 2-way valve to leave expiration free, with a nose clip on;

c) *Straw breathing*: the participants, wearing a nose clip, were asked to breathe using plastic tubing (8 cm extension tubing with a 3 mm inner diameter, Asept Inmed, Quint-Fonsegrives, France) directly connected to their mouth and providing both inspiratory and expiratory resistance.

7) Psychophysiological reactions to experimental dyspnea (Table 1 and electronic supplement ES3) (5 minutes, see details below);

8) Theoretical course on the pathophysiology of dyspnea, its clinical impact and its treatment (40 minutes);

9) Immediate completion of a satisfaction questionnaire evaluating the course (5 minutes, Table 1 and electronic supplement ES4), including an overall rating (from 0 to 20).

10) 1-year evaluation (Table 1 and electronic supplement ES5) (available only in the first group).

The design of the course respected the four-stage process of Kolb's experiential learning cycle, the students' knowledge about dyspnea being enriched through the transformation of an experience of dyspnea (Figure 1). After being engaged in an actual dyspnea experience (step 1: concrete experience), students were invited to reflect on what happened to them during this experience (step 2: reflection/observation). A theoretical course then intended to help the students amalgamate their personal experience and theoretical concepts (step 3: conceptualization/explanation). Finally, immediate and delayed evaluations assessed the change in the students' beliefs and attitudes about dyspnea (step 4. Active experimentation/projection) [17].

## Collected variables and empathy assessment

Table 1 summarizes the data collected at the different time points.

## Statistical analysis

The data analysis followed a 3-part statistical plan: 1) the psychophysiological reactions to the observation of the teacher's demonstration of dyspnea and to the personal experience of dyspnea were described and compared between the 'low empathy' and 'high empathy' participants, 2) the psychophysiological reactions to the personal experience of dyspnea were described and compared between modalities of self-induced dyspnea, 3) factors associated with the overall grade given to the course were identified.

For these analyses, continuous variables are described with median and interquartile range and compared with nonparametric tests (Mann-Whitney for comparisons between two groups [e.g., dyspnea ratings between high- and low-empathy participants], Kruskall-Wallis for comparisons between more than two groups [e.g., dyspnea ratings across experimental devices]). Categorical variables are described as percentages and compared using the Chi [2]-test or Fisher's exact test as appropriate. Correlations (Spearman) were calculated between the overall grade given to the course by the participants and variables considered likely to be related to this grade. The subset of these variables with a corrected p-value below 0.2 was retained for inclusion in multivariate analysis, and tested with three different approaches, namely multiple linear regression, stepwise multivariate regression and partial least square (PLS) regression. Based on the root mean square error (RMSE) and on the adjusted R², multiple linear regression was retained as the best approach. P-values below 0.05 were considered statistically significant.

A lexicometric analysis was performed on the verbatim of the participants immediately after their exposure to dyspnea. Details are reported in the electronic supplement (ES6). A word cloud was generated to represent the 3-word verbatim collected at 1-year (for the first group only).

Analyses were performed using R version 3.6.1.

## Results

### Participants

Fifty-five emergency medicine residents, representing the first group, participated in the study (median age 26, interquartile range [26–27] years; 26 men [47%]) (Table 2).

### Personal history and characteristics

Table 2 provides the participant characteristics overall and for the 'low empathy' and 'high empathy' groups. Eighty-five percent (n = 47) answered 'yes' to the question regarding personal experience of pain, provided a description (mostly bone fractures, n = 17, and menstrual pain, n = 5), and provided the
<figure><img src="image_36.png" /><figcaption>Table 2. Participant characteristics.</figcaption></figure>

<table><thead><tr><th>Variables</th><th>Whole n = 55</th><th>Low-<br>empathyn = 13</th><th>High-<br>empathyn = 42</th><th>P</th></tr></thead><tbody><tr><td>General characteristics</td><td></td><td></td><td></td><td></td></tr><tr><td>Age, years</td><td>26 (26–27)</td><td>26 (26–28)</td><td>26 (25–27)</td><td>0.113</td></tr><tr><td>Gender (male), n (%)</td><td>26 (47)</td><td>9 (69)</td><td>17 (40)</td><td>0.069</td></tr><tr><td>Level of self-reported empathy, NRS</td><td>7 (7–8)</td><td>4 (4–5)</td><td>7 (7–8)</td><td><strong>&lt;0.001</strong></td></tr><tr><td>Personal experience of pain*, n (%)</td><td>47 (85)</td><td>10 (77)</td><td>37 (88)</td><td>0.318</td></tr><tr><td>Rating of past experience of pain, NRS</td><td>8 (7–8)</td><td>8 (7–8)</td><td>7 (7–8)</td><td>0.713</td></tr><tr><td>Personal history of dyspnea* (pathological breathlessness), n (%)</td><td>17 (31)</td><td>2 (15)</td><td>15 (36)</td><td>0.303</td></tr><tr><td>• asthma attacks, n (%)</td><td>11 (20)</td><td>2 (15)</td><td>9 (21)</td><td>1.000</td></tr><tr><td>• fear of drowning, n (%)</td><td>3 (6)</td><td>0 (0)</td><td>3 (7)</td><td>1.000</td></tr><tr><td>• miscellaneous, n (%)</td><td>3 (27)</td><td>1 (8)</td><td>2 (5)</td><td>0.562</td></tr><tr><td>Personal history of healthy breathlessness (sport), n (%)</td><td>4 (7)</td><td>2 (15)</td><td>2 (5)</td><td>0.234</td></tr><tr><td>Rating of past experience of pathological breathlessness, NRS</td><td>6 (5–6)</td><td>6 (6–8)</td><td>6 (4–6)</td><td>0.232</td></tr></tbody></table>

Continuous variables are expressed as median (interquartile range) and categorical variables are expressed as number (%).

NRS, numerical rating scale (from 0 minimal value to 10 maximal value)

* Participants who answered 'yes' to the 'did you previously experience pain or dyspnea', and provided both a description of the associated circumstance and a NRS rating.

'Pathological breathlessness' [14] is defined as an experience of anxiogenic breathing difficulties due to a constraint that cannot be controlled, and correspond to the medical term 'dyspnea'. 'Healthy breathlessness' is the non-threatening sensation that occurs in response to intense activities in normal individuals (e.g., sports, or sexual intercourse).

corresponding NRS rating (8 [7–8]; scale 0 [minimal]-10 [maximal]). Regarding previous experience of dyspnea ('pathological breathlessness'), 17 participants (31%) answered 'yes', provided a description (asthma attacks, n = 11; fear of drowning at the swimming pool or in the sea, n = 3; miscellaneous, n = 3 [exercise during pregnancy, acute exposure to smoke, pneumonia]), and provided an NRS rating (6 [5–6]). Of note, 4 participants reported episodes of 'healthy breathlessness' during sport, which was not considered as dyspnea. Past experience of pain was significantly more frequently reported than past experience of dyspnea (p < 0.001), and the intensity of recalled pain was significantly greater than the intensity of recalled dyspnea (p < 0.001). Overall, the participants self-rated their empathy level 7 [7–8], with a significant difference between men and women (7 [6–8] vs. 8 [7–8], respectively, p = 0.032).

## Knowledge about dyspnea

Among the 55 participants, 18% had no recollection of participating in any course regarding dyspnea, 21%

recalled one course and 21% recalled two courses. Forty percent reported 3 or more courses. Those who reported one or more courses rated the quality of the dyspnea-related academic teaching received at 6 [5–7], and their wish to see improvement in this teaching at 8 [7–9].

## Attitudes and beliefs towards dyspnea

Table 3 summarizes attitudes and beliefs toward pain and dyspnea management in patients on emergency room admission. The participants rated their self-confidence in dealing with dyspneic and painful patients at 6 [5–7] and 7 [5–8], respectively, (p = 0.445). As depicted in Figure S1 (electronic supplement ES7), the two main reasons for not using morphine significantly differed for the relief of pain (fear of negative effects on ventilatory control and fear of delirium) or dyspnea (priority given to other treatments aimed at correcting the causative phenomena, and the belief that the use of morphine for dyspnea is restricted to end-of-life care).

<table><caption>Table 3. Attitudes and beliefs toward pain and dyspnea management in patients on emergency room admission.</caption><thead><tr><th>Variables</th><th>Pain</th><th>Dyspnea</th><th>P</th></tr></thead><tbody><tr><td>Confidence with the management of the considered symptom, NRS</td><td>7 [5–8]</td><td>6 [5–7]</td><td>0.445</td></tr><tr><td>Propensity to systematically look for the symptom in patients on emergency room admission, NRS</td><td>9 [8–10]</td><td>8 [7–9]</td><td><strong>0.016</strong></td></tr><tr><td>How often do you prescribe morphine for symptom relief?</td><td>0 (0)</td><td>10 (18)</td><td><strong>&lt;0.001</strong></td></tr><tr><td>Never</td><td>1 (2)</td><td>24 (44)</td><td></td></tr><tr><td>Very rarely (1/year)</td><td>9 (16)</td><td>16 (29)</td><td></td></tr><tr><td>Sometimes (1/month)</td><td>45 (82)</td><td>5 (9)</td><td></td></tr><tr><td>More than sometimes (&gt;1/month)</td><td></td><td></td><td></td></tr><tr><td>The right to symptom relief is part of the public health code*, n (%)</td><td>55 (100)</td><td>29 (53)</td><td><strong>&lt;0.001</strong></td></tr><tr><td>Notion that a clinically important threshold exists for the considered symptom, n (%)</td><td>48 (87)</td><td>11 (20)</td><td><strong>&lt;0.001</strong></td></tr><tr><td>What is the proposed clinically important threshold for the considered symptom<sup>§</sup></td><td>5 (3–6)</td><td>4 (3–5)</td><td>0.090</td></tr><tr><td>A symptom intensity rated ≥8 on NRS required immediate symptomatic relief, n (%)</td><td>52 (100)</td><td>50 (96)</td><td>0.879</td></tr><tr><td>Propensity to use morphine if symptom intensity ≥8, NRS</td><td>8 [7–9]</td><td>4 [2–6]</td><td><strong>&lt;0.001</strong></td></tr></tbody></table>

Continuous variables are expressed as median (interquartile range) and categorical variables are expressed as number (%).

NRS, numerical rating scale (from 0 minimal value to 10 maximal value)

* The 2016 version of the French public health code (article L1110-5) states that everyone has the right to the relief of his/her 'suffering'. This term replaces the word 'pain' that appeared in the 2002 version.

§ The cut-off for clinically important pain that required prompt initiation of analgesic is 4 on a numerical rating scale<sup>36</sup>

There are no guidelines on the clinically important threshold of dyspnea. A cutoff of 4 has been proposed<sup>37</sup>, but there is evidence that at least one third of patient rating their dyspnea '3' consider this clinically intolerable<sup>38</sup>.
<figure><img src="image_37.png" /></figure>

## Psychophysiological reactions to the teacher's dyspnea

Observing dyspnea elicited dyspnea (vicarious dyspnea) in 45 of the 55 participants (82%), rated 4 [2–5]. The participants rated the dyspnea of their teacher 6 [5–7], for a self-rating of 6 by the teacher. Participants in the ‘high empathy’ group reported vicarious dyspnea more frequently (88% vs. 62%, p = 0.030) and more intensely (4 [3–5] vs. 2 [0–5], p = 0.049) than those in the ‘low empathy’ group. Those in the ‘high empathy’ group also provided significantly higher estimates of the teacher’s dyspnea intensity (6 [5–7] vs. 5 [4–6], p = 0.046). Gender and personal history had no significant impact on observed dyspnea outcomes.

## Psychophysiological reactions to experimental dyspnea

Overall, 2/55 participants (4%) decided not to participate in the ‘experimental dyspnea’ phase of the course. Among the 53 remaining participants, 31 (59%) were randomized to straw breathing, 16 (30%) to CO₂ rebreathing (30%), and 6 (11%) to inspiratory threshold loading. Fifty-two (98%) of those reported dyspnea in response to the stimulus, and 1 participant did not report dyspnea (straw breathing). Overall, participants were exposed to the stimulus for 60s [40–120 s] without any between-methods differences. The participants rated breathing discomfort intensity 6 [5–8] and breathing discomfort unpleasantness (A1 scale of the MDP) 8 [6–9]) (p < 0.001). A1 ratings were inversely correlated with the duration of exposure to the dyspnoogenic stimulus: the more intense the dyspnea, the shorter the exposure (r = -0.533, 95% confidence interval (CI) [-0.701–-0.294], p < 0.001). ‘My breathing requires muscle work or effort’ and ‘I am breathing a lot’ were the two sensory descriptors the most frequently reported whereas “I am not getting enough air or I am suffocating or ‘I feel hunger for air’ was the most intensely reported. Anxiety and frustration were the two most frequently and intensely reported emotional descriptors. Overall MDP results are depicted in Figure S2 (ES8). Table S1 (ES9) and Figure S3 (ES10) provide MDP ratings according to the stimulus used. MDP ratings did not differ significantly between participants from the high or low empathy groups or according to gender.

## Evaluation of the course

### Immediate evaluation

The participants rated the experimental dyspnea-related improvement in the understanding of dyspneic patients’ experience (‘experiential

understanding’ variable) at 7 [6–8]. They rated the course at 17 [15–18] out of 20, with a significant positive correlation between these two ratings (r = 0.704 95%CI [0.598–0.875], p < 0.001). Statistically significant correlations were also shown between the overall course rating and the intensity of breathing discomfort in response to self-induced dyspnea (r = 0.318 95%CI [0.001–0.576], p = 0.043), dyspnea unpleasantness (MDP A1, r = 0.492 95%CI [0.208–0.699], p = 0.001); MDP A2 (r = 0.324 95%CI [0.198–0.612], p = 0.039); MDP affective domain (r = 0.363 95%CI [0.212–0.636], p = 0.020); and MDP immediate perception domain (r = 0.342 95% CI [0.245–0.634], p = 0.029). Among these variables, only ‘dyspnea experience’ was retained as independently correlated with the overall course rating in the multivariate analysis.

### One-year evaluation

Fifty-three percent (28/53) of the participants having participated in the dyspnea course answered the one-year follow-up questionnaire. All of them considered that the course had been useful to better apprehend what dyspneic patients experience. They rated ‘do you regard yourself more attuned than before to what acute dyspnea represents for the patients’ at 8 [7–9], ‘do you feel more confident than before when managing acute dyspnea in the ER context?’ at 7 [6–8], and ‘do you experience less anxiety than before when managing a dyspneic patient in the ER context?’ at 7 [5–8].

## Corroboration group

Fifty participants were included in the corroboration group (median age 27, interquartile range [26–28] years, 42% men). The prevalence of personal history of pain, dyspnea, or healthy breathlessness was 100%, 34%, and 12%, respectively. The participants self-rated their empathy level at 7 [7–8], and 28 (56%) were classified high-empathy. Vicarious dyspnea was reported by 38 participants (76%) and rated at 4 [2–5]; this was rated 5 [4–6] in the high empathy group and 3 [2–5] in the low empathy group (p = 0.054). Twenty-one participants (42%) were randomized to straw breathing, 24 (48%) to CO₂ rebreathing (30%), and 5 (10%) to inspiratory threshold loading. MDP A1 ratings were inversely correlated with the duration of exposure to the dyspnoogenic stimulus (r = -0.560 [-0.732–-0.320], p = <0.001). The ‘experiential understanding’ of dyspnea was rated at 7 [6–8] with an overall course grade of 18 [17–19], and there was a significant positive correlation between these two ratings (r = 0.512 [0.262–0.698] p < 0.001). There were also statistically significant correlations between the overall course rating and the intensity self-
<figure><img src="image_38.png" /></figure>

induced dyspnea (r = 0.456 [0.189–0.660], p = 0.001) and MDP A1 (r = 0.433 [0.161–0.644], p = 0.002). One-year assessment was not available for this group.

## Discussion

Before taking the dyspnea course described in this study, the participating emergency medicine residents considered that their prior training about dyspnea could be improved and expressed a desire for more advanced training. Immediately after the course and 1 year later, the participants reported an improved understanding of the experiences of dyspneic patients. The level of overall satisfaction with the course was high. Several arguments suggest that the personal experience of induced dyspnea was an essential driver of the positive reaction to the course.

## Use of the personal experience of dyspnea as a teaching tool

We incorporated experimental dyspnea in our teaching approach as an extension of Kolb's experiential learning cycle that places personal implication at the heart of the learning process with the aim of connecting theory to reality [17,24] (Figure 1). The advent of simulation in medical education and its success with medical trainees [25,26] has heavily relied upon this type of approach. Similarly, educational interventions requiring healthcare providers to 'become' a patient (namely to live the patients' symptoms, like visual impairment or auditory hallucinations [21–23]) appear particularly successful at increasing the understanding and recognition of the patient's experience [27]. Our study seems to be the first to test this type of approach in the respiratory domain. Indeed, existing dyspnea-oriented teaching instruments and courses (like the educational dimension of the 'Breathing, Thinking, Functioning' clinical model [28,29]; see also [30,31]) can change participants' previous beliefs and attitudes, but they do not involve experiential aspects. One could argue that inducing respiratory suffering for pedagogic purposes is ethically disputable. Yet, other potentially stressful experiences like simulated blindness or auditory hallucinations have been used [21–23]. We took extensive precautions to limit any untoward consequences of the dyspneic experience (participation strictly on a voluntary basis; detailed advance explanations on what to expect; the possibility to quit at any moment; the offer of psychological support on an as-needed basis). In the end, none of the participants reported regretting having participated in the course. Of note, the straw breathing challenge, one of the dyspnea induction techniques that we used, is often proposed to help the general public understand breathing difficulties, e.g., pediatric asthma) or to test anxiety sensitivity and reactivity to asthma-like

sensations [32]. Although we did not collect explicit data about changes in empathy levels at one year, there are implicit indications that the experiential course may have positively influenced the participants' propensity to empathetic solicitude towards dyspneic patients. Likewise, all of the participants considered that the experiential component of the course had been 'useful to better apprehend what dyspneic patients experience' (rated 7 [6–8] on a 0–10 numerical scale); they considered themselves 'more attuned than before to what acute dyspnea represents for the patients' (rated 8 [7–9]); they reported substantial increase in confidence and decrease in anxiety when managing dyspneic patients.

## Contribution of the personal dyspnea experience to course appraisal by the residents

Any of the course components (observation, personal experience, theory) could have contributed to our participants' reactions and satisfaction with the course. Nevertheless, the personal experience of dyspnea seems to have played a particularly important role. Firstly, despite one or more previous theoretical courses on the topic, our participants mentioned incomplete satisfaction with their prior training on dyspnea. Secondly, we found statistically significant correlations between the overall course rating and several psychophysiological measures (intensity of breathing discomfort, dyspnea unpleasantness, MDP domains). This was not the case regarding the observation of the teacher's dyspnea. Thirdly, the 'experiential understanding' variable (experimental dyspnea-related improvement in understanding dyspneic patients' experience) was the only variable that remained significantly associated with the overall course rating in multivariate analysis. The apparent importance of 'experiential understanding' in changing the participants' perspective is consistent with observations showing that breathing discomfort linked to the use of COVID-19 face masks relates to improved perception of the lived experience of patients with chronic respiratory disease [20].

## Consistency and discrepancies with the experimental dyspnea literature

Our data indicate that the experience of pain is more frequent than the experience of dyspnea in healthy young subjects, with pain remembered as more intense. Observing dyspnea in another person induced dyspnea in our participants, as reported previously [15], with a statistically significant correlation between vicarious dyspnea ratings and the ratings of self-perceived empathy [15]. Self-induced dyspnea was predominantly described as 'air hunger' in the sensory domain and associated with anxiety/
<figure><img src="image_39.png" /></figure>

frustration in the emotional domain. Ratings were particularly high, notably regarding dyspnea unpleasantness (median of 8). This observation is reminiscent of the high ratings associated, in the general public, with COVID-19 face mask-induced breathing discomfort, previously interpreted as illustrating the impossibility of imagining the intensity of a characteristic of which an individual has no direct experience [20]. We did not find differences according to the method used to self-induce dyspnea, in contrast with literature data differentiating inspiratory threshold loading and CO₂ stimulation [33]. We do not have specific explanations for these observations.

## Strengths and limitations

The strengths of our study include its innovative design and the clear and reproducible results across two groups of residents from different specialties and separated temporally. The results demonstrate the feasibility of inducing experimental dyspnea in a large number of residents simultaneously using simple and transportable tools, making implementation in medical and nursing school programs realistic. However, the study also has several limitations. First, as in many studies of this type, changes in attitudes and beliefs could only be evaluated in a declarative manner, as well as empathy level, which leaves the possibility of bias. Second, there was a 50% attrition in the number of respondents at 1 year, so the long-term results should be interpreted with caution. Third, the study pertained to acute dyspnea and cannot readily be extrapolated to persistent dyspnea. Fourth, vicarious pain was not induced or assessed and could have been interesting to contextualize the residents' reactions to observed dyspnea with respect to the corresponding reactions to pain. Finally, specific studies would be needed to assess the respective influences of the course components, and, importantly, to compare the experiential intervention to other types of intervention. We cannot rule out that other approaches like watching testimonials of dyspneic patients or expert-patients teaching could also be effective.

## Conclusions

In conclusion, the results of this pilot study support the pedagogical interest of dyspnea-targeted teaching programs incorporating an experiential element. This approach could help healthcare professionals better address the currently largely unmet patients' dyspnea-related expectations [34].

## Availability of data and materials

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

## Disclosure statement

Maxens Decavèle reports personal fees (for congress registration) from ISIS Medical.

## Funding

The author(s) reported there is no funding associated with the work featured in this article.

## Ethics approval and consent to participate

The study was approved by the university ethical committee (Comité d'Éthique de la Recherche, Sorbonne Université, Paris, France, # CER 2020-2). Oral information about the study was given to patients or their families prior enrolment.

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Electronic Supplement to

"Involve me and I learn": personal experience and dyspnea awareness in
medical residents

ES1. Generic participants questionnaire

ES2. Psychophysiological reaction to the teacher's dyspnea

ES3. Multidimensional Dyspnea Profile ³⁵

ES4. Immediate course evaluation questionnaire

ES5. One-year course evaluation questionnaire

ES6. Lexicometric analysis

ES7. Figure S1. First (panel A) and second (panel B) reasons advanced by the participants to not using morphine for the symptomatic relief of severe (NRS ≥ 8) pain or dyspnea

ES8. Figure S2. Distribution and intensity of the Multidimensional Dyspnea Profile sensory (upper panels) and emotional (lower panels) descriptors among the 53 participants who accepted to participate in the "experimental dyspnea" part of the study, immediately after being exposed to dyspnea.

ES9. Table S1. Comparison of the multidimensional dyspnea profile (MDP) scores between the three different dyspnea experimental devices

ES10. Figure S3. Distribution and intensity of the multidimensional dyspnea profile sensory (upper panels) and emotional (lower panels) descriptors among the 53 participants immediately after self-induced experimental dyspnea according to the type of dyspnea induction method.
# ES1. Generic participants questionnaire (5 minutes)

## General characteristics

* How old are you?

* What is your gender?

## Personal history

* During your life, have you ever felt pain (physical, not moral)? (Yes or No)

If Yes, on what occasion and what was the maximum intensity in your memory from 1: very low intensity to 10 extremely high intensity?

* During your life, have you ever felt dyspnea? (Yes or No)

If Yes, on what occasion and what was the maximum intensity in your memory from 1: very low intensity to 10 extremely high intensity?

* In general, regarding your personality, how would you rate your level of empathy from 0: no empathetic at all to 10: extremely empathetic?

## Academic formation

* During your medical studies (second and third cycle of French medical studies) how many academic courses dedicated to dyspnea (e.g. pathophysiology, measurement, treatment) did you have to attend, before this experiential teaching course?

* In general, how would you rate, on a visual analog scale (VAS) from 0: not satisfied at all to 10: fully satisfied, the quality of the academic education (second and third cycle included) of dyspnea that you received during your medical studies (before this experiential teaching)?

* In general, would you like an improvement in the academic teaching of dyspnea during your medical studies (second and third cycle of French medical studies), VAS from 0: not motivated at all for an improvement to 10: fully motivated?

* At your current level of medical education (and before this experiential teaching), how would you rate your level of confidence in your ability to manage pain in a patient upon emergency room admission, VAS from 0: no confident at all, to 10: fully confident?

* At your current level of medical education (and before this experiential course), how would you rate your level of confidence in your ability to manage dyspnea in a patient upon emergency room admission, VAS from 0: no confident at all, to 10: fully confident?

## Attitudes and beliefs regarding pain and dyspnea

* In your activity as a medical doctor, how do you quantify your propensity to look for pain in patients upon emergency room admission from 0: very low propensity to 10: very high propensity?

* In your activity as a medical doctor, how do you quantify your propensity to look for dyspnea in patients upon emergency room admission from 0: very low propensity to 10: very high propensity?

* In your activity as a medical doctor, how often do you prescribe morphine for severe pain relief?

- Never

- Very rarely (1/year)

- Sometimes (1/month)

- More than sometimes (>1/month)

* In your activity as a medical doctor, how often do you prescribe morphine for severe dyspnea relief?

- Never

- Very rarely (1/year)

- Sometimes (1/month)
- More than sometimes (>1/month)

* In your opinion, the right to pain relief is part of the French public health code? (Yes or No)

* In your opinion, the right to dyspnea relief is part of the French public health code? (Yes or No)

* Do you have an idea of the cut-off value that is considered clinically significant regarding pain (pain intensity that should require immediate relief) on a numerical rating scale from 0 to 10 (maximum intensity)?
If yes, what do you believe this cut-off is?

* Do you have an idea of the cut-off value that is considered clinically significant regarding dyspnea (dyspnea intensity that should require immediate relief) on a numerical rating scale from 0 to 10 (maximum intensity),
If yes, what is this cut-off?

* If your patient has pain rated 8/10 on the numerical rating scale:

* Are you initiating any specific treatments intended to relieve this pain? (Yes or No)

* What is your propensity to initiate an emergency morphine titration from 0: very low propensity to 10: very high propensity?

* Choose 2 factors that would contribute to not using morphine (score 1 and 2 from most to least important) among the following sentences:

1-Pain usually goes away by itself and does not need to be treated

2-Pain usually achieves adequate relief with other treatments

3-There is a lack of evidence for morphine efficacy in pain relief

4-Guidelines on morphine use for pain relief are inexistent or inappropriate for the emergency room setting

5- I have previous clinical experience that opioids for pain relief induced clinical deterioration

6-I only use morphine for pain relief in more advanced disease for end-of-life care settings

7-I am concerned by the risk of addiction/substance abuse

8-I am concerned by the potential negative side effects of morphine on breathing

9-I am concerned by the risk of confusion/delirium induced by morphine

10-I am afraid morphine will speed up the onset of death

* If your patient has dyspnea rated 8/10 on the numerical rating scale,

* Are you initiating any specific treatments intended to relieve this dyspnea? (Yes or No)

* What is your propensity to initiate an emergency morphine titration from 0: very low propensity to 10: very high propensity?

* Choose 2 factors that would contribute to not using morphine (score 1 and 2 from most to least important) among the following sentences:

1-Dyspnea usually goes away by itself and does not need to be treated

2-Dyspnea usually achieves adequate relief with other treatments

3-There is a lack of evidence for morphine efficacy in dyspnea relief

4-Guidelines on dyspnea use for dyspnea relief are inexistent or inappropriate for the emergency room setting

5- I have previous clinical experience that opioids in dyspnea relief induced clinical deterioration

6-I only use morphine for dyspnea relief in more advanced disease for end-of-life care settings

7-I am concerned by the risk of addiction/substance abuse

8-I am concerned by the potential negative side effects of morphine on breathing

9-I am concerned by the risk of confusion/delirium induced by morphine

10-I am afraid morphine will speed up the onset of death
## ES2. Psychophysiological reactions to the teacher's dyspnea

* How much do you rate the teacher's dyspnea intensity on a numerical rating scale (NRS) from 0: very low to 10: extremely high?

* Have you experienced dyspnea yourself while watching the teacher? (Yes or No)

* If Yes, how do you quantify the dyspnea you felt on a NRS from 0: very low intensity to 10: extremely high intensity?

## ES3. The Multidimensional Dyspnea Profile (MDP)³³.

The MDP consists of eleven items evaluating both the sensory and affective dimensions of dyspnea. It can generally be completed in 3 minutes or less. Before completing the questionnaires, participants are presented with a musical analogy to explain the difference between "sensory" and "affective", using the following script:

> On this page we ask you to tell us how unpleasant your breathing feels. On a later page, we will ask you about the intensity or strength of your breathing sensations. The distinction between these two aspects of breathing sensation might be made clearer if you think of listening to a sound, such as a radio. As the volume of the sound increases, I can ask you how loud it sounds or how unpleasant it is to hear it. For example, music that you hate can be unpleasant even when the volume is low, and will become more unpleasant as the volume increases; music that you like will not be unpleasant, even when the volume increases.

One item (A1) assesses the unpleasantness of dyspnea on a 0-10 numerical scale anchored by "neutral" (0) and "unbearable" (10).

To assess the sensory dimension of dyspnea (SQ), participants are asked to report which of five items apply to their experience, which one of the five best apply to describe this experience, and to rate the five items on a 0-10 numerical rating scale from "none" to "as intense as I can imagine". These 5 items are listed below.

To assess the affective dimension of dyspnea (A2), participants are asked to rate five items qualifying the feelings associated to their perceived breathing difficulties, on a 0-10 numerical rating scale from "none" to "the most I can imagine". These 5 items are listed below.

<table><thead><tr><th>Label</th><th>French sentences</th><th>English sentences</th><th>Coded variables</th></tr></thead><tbody><tr><td>A1</td><td>Désagrément, caractère désagréable de vos sensations respiratoires</td><td>Unpleasantness or discomfort of your breathing sensations, how bad your breathing feels</td><td><strong>Intensity of the unpleasantness related to dyspnea</strong></td></tr><tr><td rowspan="6">SQ</td><td>Je dois fournir un travail ou un effort musculaire pour respirer</td><td>My breathing requires muscle work or effort</td><td><strong>Breathing-related sensations</strong><br>Muscle work</td></tr><tr><td>Je manque d'air ou j'étouffe ou je sens que j'ai besoin d'air</td><td>I am not getting enough air or I am suffocating, or I feel hunger for air</td><td>Air hunger</td></tr><tr><td>J'ai la sensation que ma poitrine et mes poumons sont serrés ou comprimés</td><td>My chest and lungs feel tight or constricted</td><td>Chest tightness</td></tr><tr><td>Je dois me concentrer ou faire un effort mental pour respirer</td><td>My breath requires mental effort or concentration</td><td>Mental effort</td></tr><tr><td>Je respire fort</td><td>I am breathing a lot, rapidly, deeply, heavily</td><td>Breathing a lot</td></tr><tr><td>Ma respiration me déprime</td><td>My breathing makes me feel depressed</td><td><strong>Breathing-related emotions</strong><br>Depression</td></tr><tr><td rowspan="2">A2</td><td>Ma respiration me rend anxieux(se)</td><td>My breathing makes me feel anxious</td><td>Anxiety</td></tr><tr><td>Ma respiration me frustre</td><td>My breathing makes me feel frustrated</td><td>Frustration</td></tr></tbody></table>
<table><tr><td>My respiration me rend en colère</td><td>My breathing makes me feel angry</td><td>Anger</td></tr><tr><td>My respiration m'effraie</td><td>My breathing makes me feel afraid</td><td>Fear</td></tr></table>

Several scores can be calculated from the above answers:

- sensory dimension: SQ obtained by summing the 5 sensory descriptors

- affective dimension: A1+A2

- immediate perception domain: SQ+A1

- emotional response domain: A2 obtained by summing the 5 emotional descriptors

## ES4. Immediate course evaluation questionnaire

- To what extent did your personal experience of dyspnea change your understanding of this symptom?

- Not at all

- A little

- A lot

- Totally

- To what extent did your personal experience of dyspnea make you better understand what dyspneic patients feel?

NRS from 0: absolutely not to 10: considerably?

- Finally, please give a grade from 0 to 20 for the course!

## ES5. One-year course evaluation questionnaire

- Do you think that the type of experiential teaching to which you were exposed in November 2019, is a good method to become familiar with dyspnea and thus be able to better understand what acute dyspnea represents for the patient? (Yes or No)

- Since the experiential teaching of dyspnea that you received in November 2019, do you consider yourself (VAS from 0: not at all, to 10: totally) more aware of the patients' suffering that represents dyspnea and more prone to looking for dyspnea in these patients?

- Since the experiential teaching of dyspnea that you received in November 2019, to what extent, VAS from 0: not at all to 10: very much, do you feel more confident in the management of acute dyspnea in the emergency room?

- Since the experiential teaching of dyspnea that you received in November 2019, to what extent, VAS from 0: not changed, 10 greatly reduced, do you have the impression that the management of acute dyspnea in an emergency room patient causes you less anxiety than before?

- One year after this experiential teaching of dyspnea, give us the 3 words that you think best describe the impact it has had on you and your practice.
## ES6. Lexicometric analysis (Methods, Results, Figure)

### Methods

Words or expressions chosen by each participant after their self-induced dyspnea experience were lemmatized and merged as individual verbatims to perform a correspondence factorial analysis followed by descending hierarchical classification. The creation of a paired binary variable (e.g. men and high empathy) was necessary to enter these binary variables in correspondence factorial analysis. These paired binary variables had therefore four possible issues depending on the presence or absence of each component.

### Results

The lexicometric analysis of the participants’ verbatim identified three semantic classes (Figure). Class 1 had a "unpleasant" connotation ("unpleasant", "adaptation", "limitation"), class 2 had a more "emotional" connotation ("anxiety", "frustration"), class 3 was more neutral ("die", "air", "miss") and class 4 was more "sensory" connotation ("keep calm", "discomfort"). There was no statistically significant association between these classes and other variables. Nevertheless, words from class 2 and 4 were more frequent in high empathy group, while words from class 3 were more frequent in the low empathy group. Class 3 and class 4 were diametrically opposed regarding the estimation of the teacher’s dyspnea intensity (low intensity for class 3 and high intensity for class 4).

**Figure.** Illustration of the results of the lexicometric analysis performed on the verbatim collected immediately after exposure to self-induced dyspnea. Four semantic classes were identified.

<figure><img src="image_41.png" /></figure>
<figure><img src="image_42.png" /><figcaption>ES7. Figure S1. First (panel A) and second (panel B) reasons advanced by the participants for not using morphine for the symptomatic relief of severe (NRS ≥ 8) pain or dyspnea</figcaption></figure>

* p<0.05

NRS, numerical rating scale (from 0: minimal to 10: maximal intensity)
<figure><img src="image_43.png" /><figcaption>ES8. Figure S2. Distribution and intensity of the Multidimensional Dyspnea Profile sensory (upper panels) and emotional (lower panels) descriptors among the 53 participants who accepted to participate in the "experimental dyspnea" part of the study, immediately after being exposed to dyspnea.</figcaption></figure>

Grey bars indicate the proportion (%) of subjects that chose the sensation or emotion. White boxes represent the median and the interquartile interval, whiskers the 95% confidence interval.
<table><caption>ES9. Table S1. Comparison of the multidimensional dyspnea profile (MDP) scores between the three different dyspnea experimental devices</caption><thead><tr><th>MDP scores</th><th>All<br>n = 53</th><th>Inspiratory<br>resistance<br>n = 31</th><th>CO<sub>2</sub><br>rebreathing<br>n = 16</th><th>Inspiratory<br>threshold loading<br>n= 6</th><th>P<br>(KW)</th></tr></thead><tbody><tr><td>A1 (unpleasantness intensity), NRS</td><td>8 [6-9]</td><td>8 [6-9]</td><td>8 [6-10]</td><td>9 [6-9]</td><td>0.559</td></tr><tr><td>A2 (emotional descriptors NRS sum)</td><td>16 [8-22]</td><td>13 [7-22]</td><td>18 [8-24]</td><td>22 [17-28]</td><td>0.189</td></tr><tr><td>Affective dimension (A1+A2)</td><td>23 [14-31]</td><td>21 [13-31]</td><td>26 [13-31]</td><td>30 [27-37]</td><td>0.225</td></tr><tr><td>SQ (sensory descriptors NRS sum)</td><td>33 [25-29]</td><td>30 [24-38]</td><td>35 [24-40]</td><td>37 [29-44]</td><td>0.311</td></tr><tr><td>Immediate perception domain (SQ+A1)</td><td>41 [32-46]</td><td>39 [30-46]</td><td>43 [29-48]</td><td>44 [36-54]</td><td>0.316</td></tr></tbody></table>

Continuous variables are expressed as median (interquartile range)

NRS, numerical rating scale (from 0 minimal value to 10 maximal value); KW, Kruskal-Wallis test.
# Approche expérimentale

## Étude « Empadys »

Comme nous l'avons évoqué précédemment, divers arguments suggèrent que le simple fait de rendre la dyspnée visible peut contribuer à la soulager.

L'étude d'Herzog et al. précédemment citée a montré que la simple présence, comportementalement neutre, d'autres humains aux côtés d'un humain qui fait l'expérience d'une dyspnée aiguë suffit à atténuer l'intensité de cette dernière [151].

Nous avons voulu approfondir ce travail en évaluant l'effet de la sollicitude empathique sur le vécu d'une dyspnée induite expérimentalement chez des volontaires sains, préalablement à la mise en place d'une étude clinique auprès de patients souffrant de dyspnée.

Pour cela, il est nécessaire que l'observateur appréhende non seulement la dyspnée de l'autre, mais aussi que celui-ci ait conscience de la visibilité de sa dyspnée pour l'observateur.

Il est aussi nécessaire que la réaction de l'observateur, en réponse à l'identification de la souffrance du volontaire sain, soit assortie d'une attitude et d'un comportement adéquats, débouchant sur ce qu'il est convenu d'appeler la "sollicitude empathique".

Pour ce faire, nous avons choisi de comparer le vécu de deux épisodes successifs de dyspnée expérimentale dans deux groupes de volontaires sains. L'ensemble des étapes de l'étude est identique dans les deux groupes, seule l'attitude des intervenants change en fonction du groupe. Elle est qualifiée de « neutre » dans un groupe et de « sollicitude empathique » dans l'autre.

L'objectif principal de cette étude est d'évaluer l'impact de la sollicitude empathique d'un intervenant par rapport à un comportement neutre sur le vécu affectif d'une dyspnée induite chez le volontaire sain, avec pour hypothèse primaire une réponse affective moins intense lorsque l'expérience s'effectue en présence d'un intervenant adoptant un comportement de sollicitude empathique (verbal et/ou non verbal) que lorsqu'elle s'effectue en présence d'un intervenant adoptant un comportement neutre. L'impact sur la dimension sensorielle, l'anxiété, le profil végétatif et l'appréhension à l'idée de vivre, ou de revivre, une expérience de dyspnée expérimentale font partie des objectifs secondaires.

Est définie comme sollicitude empathique toute attitude verbale ou comportementale témoignant de l'attention au sujet et à son vécu (notamment contact visuel ou physique, questions ouvertes incitant à l'échange, vigilance aux manifestations du sujet, posture d'écoute). Ainsi, dans le Groupe Empathie (GE) : tout au long de l'expérience de dyspnée, l'intervenant professionnel est assis en face du sujet, légèrement sur le côté, de façon à entrer
en relation avec le volontaire sain. Il témoigne envers le volontaire sain une sollicitude
empathique par ses gestes et/ou ses paroles. Il fait preuve d'une attention importante envers
le volontaire sain et adapte son attitude aux besoins perçus (silence ou parole). L'attitude
empathique n'est pas stéréotypée mais se décline au cas par cas pour s'ajuster au volontaire
sain. Le seul critère exigé est la manifestation d'une réelle sollicitude envers le volontaire sain.

Est définie comme neutre toute attitude verbale ou comportementale témoignant d'une
indifférence relative au patient (notamment absence de contact visuel ou physique, posture
en retrait, absence de question posée, réponses factuelles aux questions du volontaire,
absence de réaction aux manifestations du sujet). Ainsi, dans le Groupe Neutre (GN) : tout au
long de l'expérience de dyspnée, l'intervenant est silencieux. Il reste positionné en retrait,
derrière ou à côté du volontaire sain.

L'expérience est reproduite par le même intervenant trois à cinq jours plus tard dans les mêmes conditions pour un participant donné, dans le but de vérifier si l'effet observé au décours immédiat de la dyspnée induite persiste dans le temps (effet rémanent).

Pour s'affranchir d'un possible phénomène d'habituation lié à la répétition d'expériences de dyspnée, la méthodologie retenue est celle d'une étude en « bras parallèles ».

Compte tenu du nombre de volontaires inclus dans l'étude, plusieurs intervenants sont nécessaires. Néanmoins, afin de limiter les biais de reproductibilité, le nombre d'intervenants a été limité à quatre professionnels de santé. L'empathie pouvant être influencée par la profession, la spécialité et le genre, nous avons choisi une répartition prenant en compte ces critères. Le groupe d'intervenants est donc composé d'une femme infirmière travaillant en pneumologie, d'une femme médecin travaillant en équipe de soins palliatifs, d'un homme médecin travaillant en pneumologie et d'un homme infirmier travaillant en équipe de soins palliatifs.

La perception par les volontaires sains du degré d'empathie de l'intervenant ainsi que le degré de résonance empathique ressenti par l'intervenant avec le volontaire sain au cours des expériences de dyspnées induites ont également été recueillis après chaque visite et dans chaque groupe.

Cette étude monocentrique, randomisée, contrôlée, en groupes parallèles et en simple
aveugle prévoit d'inclure 80 volontaires sains, au terme d'un calcul d'effectif effectué par
l'Unité de Recherche Clinique de la Pitié-Salpêtrière (Dr Noémie Simon-Tillaux).

Ce calcul a été fait sur la base de données recueillies au sein du laboratoire dans le cadre
d'autres études qui ont permis de constater que l'échelle visuelle analogique (EVA) affective
de la dyspnée avait une distribution bimodale, avec une distribution de Poisson (pour les
valeurs d'EVA comprise entre 0 et 9) et une composante binomiale (quand l'EVA prend la valeur 10).

Pour estimer la puissance associée à une taille d'échantillon donnée et la différence entre l'EVA affective en présence d'un soignant manifestant de la sollicitude empathique ou non, nous avons utilisé des simulations (10000 itérations). Nous avons simulé la distribution de ces deux EVA avec une distribution bimodale. Nous avons supposé que les EVA étaient différentes, en changeant à la fois la moyenne de la composante de Poisson et de la composante binomiale. Nous avons testé la différence entre les deux distributions d'EVA avec un modèle Hurdle, qui estime la différence entre les moyennes des deux distributions de Poisson et des deux distributions binomiales respectivement. Nous avons testé si ces deux différences étaient différentes de zéro par le test du rapport de vraisemblance (LRT) au niveau d'erreur de type 1 de 5% (bilatéral).

Un changement de -1.5 cm de la moyenne de la composante de Poisson de la distribution et une baisse absolue de 20% de la proportion d'EVA à 10 (soit une différence de moyenne apparente de -2.36 cm pour l'EVA entre 0 et 10), pour une puissance de 82.6 % et une erreur de type 1 de 5 % (bilatérale) nécessite une taille d'échantillon de 40 participants par bras.

En estimant un taux de perdus de vue à 10%, le nombre total de patients à inclure dans cette étude de 44 participants par bras.

Les critères d'inclusion de cette étude sont les suivants :

* Volontaire sain

* Majeur de 18 à 65 ans

* Non-fumeur ou sevré depuis au moins un an avec nombre paquet-année <5

* Ayant été informé sur l'étude et ayant donné son consentement écrit et éclairé

* Recruté spécifiquement pour cette étude

Les critères de non-inclusion de cette étude sont les suivants :

* Femme enceinte (déclaratif), majeur protégé, personne privée de liberté

* Existence de pathologie respiratoire, cardiaque, neuromusculaire ou antécédent d'épisode dyspnéique aigu

* Obésité $\ge$ 35Kg/m2

* Pratique intensive d'une activité nécessitant un contrôle ou la prise de conscience volontaire de la respiration (méditation, yoga, plongée, pratique d'un instrument à vent...)

* Volontaire ayant déjà participé à une étude impliquant une dyspnée expérimentale

* Existence de toute pathologie chronique identifiée et relevant d'un traitement, y compris psychiatrique

* Non affiliation à la sécurité sociale
L'objectif principal de cette étude est d'évaluer l'impact de la sollicitude empathique d'un intervenant par rapport à un comportement neutre sur le vécu affectif d'une dyspnée induite chez le volontaire sain. L'impact sur la dimension sensorielle, l'anxiété, le profil végétatif et l'appréhension à l'idée de vivre, ou de revivre, une expérience de dyspnée expérimentale font partie de nos objectifs secondaires.

L'induction dyspnée expérimentale est réalisée par l'exposition des volontaires sains à un test de réinspiration de CO2. Cette méthode, décrite initialement par Read, et réalisée en routine dans le cadre des explorations fonctionnelles respiratoires pour évaluer la chémosensibilité du système nerveux central au CO2.

Pour ces inductions, les volontaires sains sont installés confortablement sur un fauteuil en position assise. Ils respirent par la bouche, avec un embout buccal et en portant un pince-nez, à travers un appareil muni d'un dispositif de mesure de la ventilation, du taux de CO2 inspiré et expiré, et d'un sac rempli d'un mélange gazeux contenant 7% de CO2 et 93% d'O2.

Au début du test, les volontaires sains respirent l'air ambiant et leur ventilation est mesurée. Puis, ils sont connectés au sac dans lequel ils respirent en circuit fermé. Le taux de CO2 inspiré augmente donc progressivement, au fur et à mesure que le contenu du sac est alimenté par le CO2 produit. Chez les sujets normaux, la ventilation augmente proportionnellement au taux de CO2. Le test est interrompu à la demande du participant.

Il n'y a pas de danger d'hypoxie pour les volontaires sains qui respirent un mélange hyperoxique puisqu'il contenait au départ 93% d'O2. L'hypercapnie ne présente pas de danger particulier. Elle peut parfois causer des céphalées passagères et spontanément résolutes dès l'arrêt de l'exposition.

Au cours des inductions, des mesures physiologiques sont réalisées en continu (Pression télé-expiratoire en CO2 (PETCO2), ventilation, pression d'occlusion ; saturation pulsée en O2 (SpO2), fréquence respiratoire (FR), et fréquence cardiaque (FC) à l'aide d'un saturomètre).

Les inclusions ont commencé en mars 2022 après l'obtention d'un avis favorable d'un comité de protection des personnes en janvier 2022. Les inclusions sont toujours en cours. Plus de cinquante volontaires sains ont été inclus.

Une analyse préliminaire a été réalisée après l'inclusion de la moitié de l'effectif total de l'étude. Pour cette analyse, les variables continues sont décrites à l'aide de la médiane et de l'écart interquartile et comparées à l'aide de tests non paramétriques (Mann-Whitney pour les comparaisons entre deux groupes (ici les évaluations de l'EVA affective de la dyspnée dans les 30 dernières secondes de l'expérimentation entre les deux groupes).
Une différence significative entre les deux groupes sur le vécu affectif, c'est-à-dire le caractère désagréable, de la dyspnée a ainsi pu être observée.

<table><thead><tr><td>EVA affective de la dyspnée</td><td>Groupe « Neutre »</td><td>Groupe « Empathique »</td><td></td></tr></thead><tbody><tr><td>Visite 1</td><td>8 [6-9.25]</td><td>5[3-7]</td><td>p=0,0028</td></tr><tr><td>Visite 2</td><td>7 [7-8]</td><td>5[3-8]</td><td>p=0.03</td></tr></tbody></table>

L'étude « Empadys » est également une composante de la thèse de Nathalie Nion dont nous sommes co-premières investigatrices. Nous prévoyons de compléter les inclusions d'ici février 2022. L'objectif est de faire les analyses, de rédiger et de soumettre l'article avant juillet 2022.

Le dossier complet de l'étude, tel qu'approuvé par le Comité de Protection des Personnes ILE DE FRANCE X (décision n° 2021-A02813-38 du 19 janvier 2022) figure en Annexe 2.
## CONCLUSIONS ET PERSPECTIVES

Ce travail donne à l'expérience vécue une place centrale et prédominante. Ce faisant, il défend l'idée d'une médecine en tant qu'art au moins en tant que science.

La médecine dite scientifique considère le corps humain comme un mécanisme dont le fonctionnement s'appuie sur l'anatomie, la physiologie ou tout autre approche lui permettant de l'objectiver ou de le traduire en données factuelles, quantitatives ou conceptuelles.

L'expérience ou le vécu, subjectif par définition, n'entre pas dans ce processus et le corps semble être en dehors du « Je ».

La séparation du corps et de l'esprit est l'héritage de Descartes. Celui-ci explique dans sa sixième méditation [15].

> « Il suffit que je puisse concevoir clairement et distinctement une chose sans une autre, pour être certain que l'une est distincte ou différente de l'autre [...] j'ai une idée claire et distincte de moi-même, en tant que je suis seulement une chose qui pense et non étendue, et que d'un autre j'ai une idée distincte du corps, en tant qu'il est seulement une chose étendue et qui ne pense point, il est certain que ce moi, c'est-à-dire mon âme, par laquelle je suis ce que je suis, est entièrement et véritablement distincte de mon corps, et qu'elle peut être, ou exister sans lui ».

Bien qu'interactionniste, c'est-à-dire considérant le corps comme « étroitement conjoint » à l'esprit, ce dualisme cartésien montre quelques limites. Le propos n'est évidemment pas de nier ou de minimiser l'intérêt de cette approche naturaliste de la médecine scientifique mais de montrer dans quelle mesure elle est parfois insuffisante et comment elle peut complétée, voire potentialisée, par d'autres approches.

L'intérêt d'une approche phénoménologique avait déjà été mise en évidence dans le champ de la douleur. Selon Le Breton, que nous avons précédemment cité, « l'anthropologie écarte le paradigme biologique de la biomédecine (un système symbolique qui s'ignore lui-même) pour un paradigme centré sur les individus en relation. Elle fait sa matière première des significations qui alimentent leur ressenti et leur réflexivité. Avancer l'expérience de la douleur, sa phénoménologie, n'est pas un désaveu opposé à la médecine mais constitue le rappel de ce qu'elle perd quand elle ne s'intéresse qu'aux indicateurs anatomo-physiologiques, à l'organisme, en oubliant de prendre en compte le sujet souffrant. À travers des études sur la douleur, l'anthropologie restaure l'expérience du patient et rend sans doute le médecin plus attentif à sa plainte, à son histoire de vie, non sans bénéfice thérapeutique pour le patient, ne serait-ce que par le sentiment qu'il éprouve d'être pris en considération » [46].
Canguilhem disait d'ailleurs que « L'homme fait sa douleur – comme il fait une maladie, ou comme il fait son deuil – bien plutôt qu'il ne la reçoit ou ne la subit »<fnref n="14" />.

Appliquée à la question de la dyspnée et de son invisibilité, cette approche nous a permis de mieux appréhender notre problématique et de mieux concevoir les pistes d'amélioration.

Ainsi, dans la première partie de ce travail de thèse, nous avons conceptualisé et structuré, à partir de la littérature existante, les différents facteurs impliqués en cascade dans la genèse de l'invisibilité de la dyspnée.

Nous en avons fait la synthèse sous la forme du schéma suivant :

<figure><img src="image_44.png" /></figure>

Cette partie du travail avait, initialement, comme seul objectif de mieux comprendre les déterminants de l'invisibilité de la dyspnée et de constituer un argumentaire solide pour l'élaboration ou la confirmation des hypothèses que nous voulions tester.

Nous en voyons maintenant une nouvelle utilité dans la mesure où ces facteurs impliqués dans l'invisibilité de la dyspnée ont, en plus de leur portée compréhensive, une portée préventive. Les concevoir, non seulement comme des causes, mais aussi comme des points de vigilance pouvant servir de leviers pour éviter l'invisibilité de la dyspnée, nous apparaît aujourd'hui comme fondamental.

De notre approche initialement exclusivement « palliative » de l'invisibilité de la dyspnée émergent, finalement, des pistes « préventives ». Nous aurions cependant pu anticiper ce résultat tant la question de la prévention est un élément central de la démarche palliative <fnref n="15" />.

<footnote n="14">¹⁴ Canguilhem G., 1966, Le normal et le pathologique. Paris, Presses universitaires de France.</footnote>

<footnote n="15">¹⁵ « Palliative care is preventative care ». Hui D. Cancer J Clin, 2018</footnote>
Des mesures de prévention, primaires, secondaires ou tertiaires peuvent donc être
envisagées. Elles impliquent plusieurs acteurs dont les pouvoirs publics (pollution, tabagisme,
sensibilisation du grand public...), l'enseignement (formation initiale et continue des
soignants), le soin (approche holistique de la dyspnée) et la recherche (fondamentale,
translationnelle, clinique).

Par exemple, lors des campagnes institutionnelles de sensibilisation, il apparaît
particulièrement important de décrire ce que sont les connaissances et les représentations du
grand public quant au souffle et aux maladies respiratoires. C'est l'objectif d'un projet intitulé
« *Connaissance du souffle* » qui utilise la même méthodologie que celle que nous avons
utilisée dans « *Lifting dyspnoea invisibility* ». Ce projet, en gestation au moment du dépôt du
présent manuscrit de thèse et qui fait l'objet d'un soutien de la Fondation du Souffle, s'inscrit
dans la continuité de l'approche phénoménologique de l'invisibilité de la dyspnée que nous
avons amorcée. Il y est fait l'hypothèse que des croyances répandues dans la population
générale, comme celle "qu'il est normal de devenir essoufflé avec l'âge", pourraient expliquer
certaines des attitudes que nous avons identifiées dans « *You can't feel what we feel* » et qui
sont connues pour être caractéristiques des maladies respiratoires chroniques. Ces croyances
expliquent, par exemple, les retards à la consultation qui sont et que nous avons identifiés
comme l'une des sources de l'invisibilité de la dyspnée. Il est aisé de voir comment un tel
résultat permettrait d'orienter une campagne de prévention primaire de l'invisibilité de la
dyspnée.

Nos travaux de recherche, présentés dans la seconde partie de cette thèse, ont permis de vérifier certaines de nos hypothèses et peuvent être articulés ainsi :

<figure><img src="image_45.png" /></figure>
L'étude « You can't feel what we feel » confirme que l'approche phénoménologique permet de mieux appréhender le vécu des patients souffrant de dyspnée persistante. Cette étude montre, d'une part, que nous pouvons déjà transformer l'invisible en dicible. Ce faisant, l'invisibilité de la dyspnée résultant du comportement des autres face à l'expérience du patient s'atténue. En effet, cette étude montre qu'une partie de l'invisibilité de la dyspnée est liée au manque de considération des vécus expérientiels et au manque de sollicitude empathique qui en est le corollaire. Or ce qui est dicible est représentable et ce qui est représentable est visible.

Ainsi, le simple fait d'adopter cette posture phénoménologique et d'accueillir la dyspnée du patient pour ce qu'elle est, à savoir une expérience subjective au sens philosophique du terme, est source d'un autre regard. On retrouve ce lien entre visible et dicible dans *Naissance de la clinique* où Foucault fait le postulat « que tout le visible est énonçable et qu'il est tout entier visible parce que tout entier énonçable » [175].

Dans le chapitre *Le Visible et l'invisible*, Foucault fait référence aux travaux de Merleau-Ponty sur la problématique du « voir » et du « dire ». Le vécu est du « vécu parlé » et la vision est « structurée comme un langage » ainsi la « distribution du visible et de l'invisible » renvoie là « où s'appartiennent encore, au ras du langage, manière de voir et manière de dire ».

Pour autant, et comme l'illustre le thème « An unshareable life experience » mis en évidence par l'analyse du discours de nos patients, notre étude soulève malgré tout l'existence d'une limite irréductible, celle de ce qui est intrinsèquement, et au moins en partie, indicible, irreprésentable et donc invisible dans l'expérience de la dyspnée. Cet « incommunicable » est lié aux limites de la pensée et du langage qui dénaturent fatalement l'expérience. Comme le dit Wittgenstein « *Les limites de mon langage signifient les limites de mon propre monde* » [176]. Certaines des choses qui se vivent ne peuvent se dire et il importe de reconnaitre cet ineffable comme tel. Dans toute expérience vécue demeure un insaisissable, un imperceptible, une tache aveugle.

Si se trouve bien là une des limites de l'approche phénoménologique, il n'en demeure pas moins qu'elle permet de confirmer qu'une partie du vécu des patients peut être « voyant ». Il s'agit donc maintenant de le rendre visible.

Pour cela nous devons considérer cette question au-delà des qualités de ce qui doit être « vu » et indépendamment des aspects biologiques ou technique de la vision. Nous abordons cette question sous l'angle du « regard » qui sous-tend la possibilité d'un choix, conscient ou inconscient, entre le « vu » et le « non-vu » et qui relèverait de l'ordre du social ou du culturel.

Ici encore, l'expérience joue un rôle central. Cette fois-ci, il ne s'agit pas de se pencher sur celle de celui qui souffre de dyspnée, mais celle de celui qui est supposé la voir. Nous avions formulé l'hypothèse que l'absence d'universalité de l'expérience de dyspnée était un des
déterminants de son invisibilité. Ainsi, en toute logique, avoir vécu personnellement une
expérience de dyspnée permet de mieux voir la dyspnée de l'autre.

Les deux études menées pour vérifier cette hypothèse l'ont confirmée mais chacune d'elle
soulève de nouvelles questions.

Dans « *Lifting dyspnoea invisibility* », nous avons constaté une différence dans le vécu de la dyspnée induite par le port du masque facial entre les deux sous-groupes de répondeurs considérés comme « en bonne santé », définis selon l'existence ou non d'un proche souffrant d'une maladie respiratoire chronique. Cette différence se retrouve principalement dans la réponse émotionnelle à la dyspnée qui, de manière significative, relève plus souvent de la peur chez les répondeurs considérés comme « en bonne santé » avec un proche suivi pour une pathologie respiratoire que chez ceux n'ayant pas de proche suivi pour une pathologie respiratoire. Or nous avons vu tout au long de ce travail de thèse le lien étroit qui existe entre la dyspnée, notamment pathologique, et la peur. Le fait d'avoir un proche suivi pour une pathologie respiratoire semble influencer le vécu de la dyspnée induite par le port du masque et le « rapprocher » de celui de la dyspnée consécutive à une maladie respiratoire.

Une des façons d'analyser ce résultat est de supposer que l'expérience des patients dyspnéiques n'est pas si invisible que ça pour leur(s) proche(s) et qu'une partie, au moins, est « vue », au moins de façon implicite voire subliminale. L'articulation de cette hypothèse d'explication avec les résultats de « You can't feel what we feel » permet de comprendre ce caractère partiel de la visibilité de la dyspnée. Il y a l'invisibilité qui peut être levée et à celle-ci correspondent plusieurs degrés de visibilité. En termes plus simples, ce qui peut être visible est plus ou moins vu. Cette articulation avec « You can't feel what we feel » soulève aussi de nouvelles questions. Ils suggèrent que les patients peuvent être « vus » sans se « sentir vus ». Ainsi la question de l'invisibilité de la dyspnée dépasserait la question du « voyant », du « visible » et du « vu ». Se « sentir vu » implique nécessairement une relation interpersonnelle qui se traduit en acte par ce qu'on appelle la sollicitude empathique. Nous pouvons illustrer cela avec l'exemple d'un groupe social également confronté à l'invisibilité, les sans-abris. Un sans-abri dans la rue est « voyant », « visible » et souvent « vu », mais si nous continuons notre chemin, ignorant sa présence, il ne peut se « sentir vu ». Il apparaît donc absolument crucial qu'une fois un message émis, implicitement ou explicitement, la réception de ce message soit, elle, explicite. Le « récepteur » du message doit devenir un « contre-émetteur » pour que l'échange puisse avoir lieu, pour que l'action de rendre la dyspnée visible puisse prendre toute sa valeur thérapeutique.

Pour revenir à l'étude « *Lifting dyspnoea invisibility* », nous pouvons également suggérer que la découverte de l'expérience de la dyspnée par les répondeurs considérés comme « en bonne santé » avec un proche suivi pour une pathologie respiratoire, induite ici par le port du masque, permet non seulement de mieux comprendre le vécu de la dyspnée « des autres »
en général mais aussi de cet « autre » particulier qu'est leur proche. Ainsi, l'impact de l'expérience serait « potentialisé » par des aspects affectifs relationnels. La « cognition incarnée » que permet l'expérience se matérialise d'emblée dans la réalité de « son monde ».

Malheureusement, nous ne pouvons approfondir ces réflexions à partir des résultats de « *Lifting dyspnoea invisibility* » dont ce n'était pas l'objectif.

L'étude « *Involve me and I learn* » ne nous permet pas non plus d'analyser plus finement cette question dans la mesure où, pour des questions de rigueur méthodologique, nous avons restreint le concept de « cognition incarnée » ou « embodiment » à sa perspective cognitiviste.

En effet, si nous reprenons les étapes du cycle d'apprentissage expérientiel selon Kolb, la phase d'expérimentation active se caractérise par le réinvestissement de nouvelles conceptualisations dans la réalité dans le but d'identifier une possible transformation de l'action future. L'apprenant se remet en interaction avec l'environnement, non pas de manière réelle, mais sous la forme d'un fonctionnement cognitif impliquant une planification hypothétique de l'action résultant d'une décision prise à la lumière des conceptualisations qui ont émergé de l'expérience [173].

Ici, l'expérience est un point de départ de l'apprentissage. Ce modèle implique une réflexion sur cette expérience, l'apprentissage se fait par prise de conscience où l'implicite est rendu explicite.

Pour autant, la mise en perspective de ces deux études suggère que l'expérience peut être source de connaissance indépendamment de toute abstraction de l'expérience et de conceptualisation de la connaissance qui en découle. Le lien entre expérience et connaissance n'est ni prédéterminé ni fixe. Ce lien est dynamique, la connaissance est le produit d'un ancrage expérientiel subjectif d'un être qui a produit l'ensemble de ses connaissances à travers le prisme de son rapport au monde.

Ainsi, nous avons vu avec « *Involve me and I learn* » que la cognition était « embodied » et « embedded ». « *Lifting dyspnoea invisibility* » nous rappelle qu'elle est aussi « enacted ».

Ce concept d'énaction développé par Varela, neurobiologiste et chercheur en sciences cognitives, suppose une autonomie du sujet sur le plan cognitif. Le monde extérieur n'est pas un « donné » indépendant du sujet. Il est un monde créé par le sujet à partir de ce qu'il en a perçu par ses actions passées. Ce monde perçu guide ses actions futures par un mécanisme que Varela appelle « *action perceptivement guidée* » [177].

Dans cette théorie, le sujet est certes autonome mais pas indépendant puisqu'il y a une co-détermination du sujet et du monde. C'est par l'expérience que le sujet et le monde se rencontrent. De la relation complexe qui nait entre eux émergent le sens du monde, les
affects qui y sont associés ainsi que la disposition à agir liée au caractère motivationnel de l'émotion.

Pour certains auteurs, cette « action perceptivement guidée » est le signe d'un engagement du sujet envers le monde et la co-émergence du sujet et du monde sous-tend une altérité fondatrice qui vient faire résonner les concepts d'énaction et d'empathie [178,179]. Certains vont même jusqu'à dire que l'énaction est au cœur de l'empathie [180].

Ce lien entre expérience, cognition, action, sollicitude empathique et invisibilité de la dyspnée qui avait été partiellement pressenti comme en témoigne l'étude « Empadys » en cours.

Cette étude a pour hypothèse explicite que la sollicitude empathique a une valeur thérapeutique intrinsèque et « de première ligne » au regard de la dyspnée. Par ailleurs, et en écho avec le principe « émission, réception, contre-émission » énoncé plus haut, l'étude « Empadys » teste, de fait, l'hypothèse qu'il ne suffit pas que la dyspnée soit « vue », mais qu'il faut aussi que cette visibilité soit visible, notamment au travers de la manifestation de sollicitude.

Au terme de ces réflexions, il apparaît que les différents travaux menés dans le cadre de cette thèse ne sont pas une simple accumulation de résultats. Ils interagissent entre eux, complexifient les équations de départ et finissent par poser plus de questions qu'ils n'amènent de réponse.

Comment savoir si le patient estime que sa dyspnée est suffisamment vue ?
L'expérience améliore-t-elle l'empathie de tous les soignants vis-à-vis de la dyspnée ?
Comment cette empathie se transforme-t-elle « en acte » sous la forme de la sollicitude empathique ?
Cette sollicitude soulage-t-elle les patients ? De quoi ? Comment ? Est-ce suffisant ?

Dès le départ, nous nous inscrivions dans un projet si vaste qu'il doit être considéré comme une visée. Ainsi, les travaux de cette thèse sont les étapes préliminaires, mais indispensables, à une nouvelle appréhension de la dyspnée et à sa prise en considération dans le soin et dans la société. Ils ouvrent plusieurs perspectives, pragmatiques, cliniques et théoriques.

Ainsi, plusieurs voies de recherche sont d'ores et déjà envisagées pour poursuivre ce qu'il est justifié d'appeler la lutte contre l'invisibilité de la souffrance respiratoire et de son symptôme, la dyspnée. Dans ce cadre, si la poursuite d'actions de nature « cognitive » est nécessaire (comme le projet « Connaissance du souffle » évoqué plus haut), il apparaît indispensable de mener des actions de nature « opérationnelle », visant à ce que les connaissances acquises sur un plan théorique puissent se traduire par une amélioration de la prise en charge des patients, et une amélioration de leur vécu.
Pour cela, nous envisageons le développement d'un outil spécifique d'identification de l'invisibilité de la dyspnée à l'échelon individuel, chez un patient donné. Cet outil, revêtant la forme d'un questionnaire, servirait de support à l'ouverture d'un dialogue entre patient et soignant sur le thème de la dyspnée, première étape de la levée de l'invisibilité. L'élaboration de ce questionnaire suivra les principes en vigueur dans le domaine. Une première étape consistera en la constitution d'un groupe de travail réunissant des professionnels de santé issus de diverses disciplines et des patients, avec l'objectif de constituer une liste d'items pertinents à l'exploration de l'invisibilité de la dyspnée. Une seconde étape consistera en la validation psychométrique du questionnaire « prototype » ainsi élaboré. Pour réaliser cette validation, il est prévu de mettre en place une collaboration avec une ou plusieurs équipes spécialisées dans ce type d'approche, équipes parmi lesquelles celle dirigée par le Dr Elke Vlemincx à l'université de Leuven est pressentie. Cette équipe est en effet à la fois spécialisée dans l'étude de la dyspnée, et compétente dans le domaine de la validation de questionnaires, comme en atteste un récent travail décrivant un nouveau questionnaire d'évaluation des compétences intéroceptives [181]. La troisième étape consistera en une validation linguistique en anglais du questionnaire français obtenu. Il conviendra alors de tester l'hypothèse qu'il est possible, à partir d'une analyse individuelle du sentiment d'invisibilité de la dyspnée, de mettre en place des mesures personnalisées bénéfiques pour le vécu du patient.

À plus court terme, nous envisageons de donner un prolongement clinique à l'étude « Empadys » qui forme la partie expérimentale de cette thèse. Ainsi, une étude reposant sur la « levée active » de l'invisibilité de la dyspnée au cours de l'interaction soignant-soigné est actuellement en préparation. Cette étude, « Empadys-Hosp », qui se déroulera chez des patients hospitalisés dans un service de pneumologie et identifiés comme souffrant de dyspnée persistante, consistera en la comparaison des effets sur la dyspnée, et plus particulièrement de sa composante affective, d'une interaction soignante dite « technique » (administration d'un flux d'air sur le visage, sans intervention d'aucune sorte sur le comportement du soignant) et d'une interaction soignante dite « empathique » (combinaison de l'administration d'un flux d'air sur le visage et d'un dialogue ciblé et « scripté » entre le soignant et le patient). L'hypothèse qui sous-tend « Empadys-Hosp » est celle d'une efficacité intrinsèque de la séquence « réception contre-émission » évoquée plus haut sur le vécu de la souffrance respiratoire par les patients. La vérification de cette hypothèse servirait de justification scientifique à des actions de formation des soignants au concept « d'empathie dirigée » comme posture de soins. Ce type de pédagogie comportementale est couramment utilisé dans d'autres contextes que le soin, et commence à l'être en direction des soignants. C'est par exemple le cas des formations à la « communication non violente », désormais implémentées au sein de la faculté de médecine Sorbonne Université <fnref n="16" />.

<footnote n="16">¹⁶ https://fc.sorbonne-universite.fr/nos-offres/du-de-communication-non-violente-pour-les-professionnels-de-la-sante/</footnote>
Préalablement à l'étude « Empadys-Hosp », il nous paraît important de rendre visible un autre phénomène, celui de la détresse empathique induite par la dyspnée de l'autre chez les soignants. Nous avons vu à plusieurs reprises dans cette thèse que l'exposition à la dyspnée de l'autre était source de malaise, et que ce malaise pouvait passer au moins en partie par l'apparition d'une dyspnée « par procuration » (« vicarious dyspnea »). Nous avons évoqué également la possibilité que l'absence de compréhension de ce qui lui arrive par celui qui « subit » ainsi la dyspnée de l'autre, cumulée à l'absence de moyens d'action clairement identifiés pour venir au secours de celui qui souffre, soit une source d'évitement, voire de maltraitance si l'évitement n'est pas possible. Ce sujet n'a, à notre connaissance, fait l'objet d'aucune étude jusqu'à présent, un manque qui pourrait procéder d'une forme de tabou. Démontrer que des soignants peuvent être amenés à fuir le contact avec leurs patients parce qu'ils ne savent ni reconnaître ni gérer le caractère négatif de la résonance empathique induite par la dyspnée implique de formuler cette hypothèse. C'est en ce sens que nous avons aussi pour objectif le développement d'une enquête auprès de soignants issus des diverses professions et de diverses disciplines (médecine interne, pneumologie, soins palliatifs, réanimation) visant à identifier l'existence de la détresse empathique induite par la dyspnée de l'autre, à la quantifier en fréquence et en intensité, et à en évaluer les déterminants (personnalité des soignants, expérience, parcours professionnel...). Si cette étude, dénommée « DyspneaDystress », montre, comme nous en faisons l'hypothèse, que la détresse empathique liée à la dyspnée existe et est relativement fréquente, se conjuguera à « Empadys-Hosp » pour justifier des actions pédagogiques ciblées en direction des soignants impliqués dans la prise en charge des patients dyspnéiques, quelle que soit la forme de la dyspnée concernée.

En parallèle avec ces trois études qualifiées « d'opérationnelles », nous avons également le projet d'approfondir la réflexion théorique visant à caractériser la dyspnée en tant qu'expérience individuelle et collective au travers de sa comparaison avec la douleur. Il n'existe en effet pas véritablement de document comparant en profondeur dyspnée et douleur sur des plans qui soient à la fois physiologiques, cliniques, phénoménologiques, sociétaux et évolutifs.

Nous allons donc poursuivre sur ce chemin et chercher à répondre aux nouvelles questions posées. Ce travail nécessitera de pouvoir articuler neurophysiologie, sciences cognitives et phénoménologie autour de l'expérience de la dyspnée, notamment en explorant le concept de neurophénoménologie expérientielle utilisé par certains pour comprendre l'analgésie obtenue par l'hypnose [182,183]. Il faudra aussi probablement en accepter les limites liées au caractère partiellement irréductible de cette expérience. De la même façon qu'on ne saura jamais « quel effet cela fait-il d'être une chauve-souris »<fnref n="17" />, on ne saura jamais vraiment l'effet que cela fait d'être malade à cause du souffle à moins de le devenir soi-même.

<footnote n="17">¹⁷ "What is it like to be a bat?". Thomas Nagel dans The Philosophical Review, 1974.</footnote>
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# ANNEXE 1

## Title

Dyspnea invisibility in advanced chronic obstructive pulmonary disease: a quantitative linguistic analysis of patients' discourses

## Authors

Jonathan DEDONDER, PhD (1) [jonathan.dedonder@uclouvain.be]

Antoine GUERDER, MD (2) [antoine.guerder@aphp.fr]

Nathalie NION, MSc (3,4) [nathalie.nion@aphp.fr]

Sophie LAVAULT, PhD (3) [sophie.lavault@aphp.fr]

Capucine MORÉLOT-PANZINI (4,5) [capucine.morelot@aphp.fr]

Jésus GONZALEZ-BERMEJO (2,4) [jesus.gonzalez@aphp.fr]

Laelia BENOIT, MD, PhD (6,7) [laelia.benoit@yale.edu]

Thomas SIMILOWSKI (3,4) [thomas.s similowski@upmc.fr]

Laure SERRESSE, MD (4,8) [laure.serresse@aphp.fr]

## Affiliations

(1) Institute for the Analysis of Change in Contemporary and Historical Societies (IACS), KU Leuven, Leuven, Belgium

(2) AP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service de Médecine de Réadaptation Respiratoire, Département R3S, F-75013 Paris, France.

(3) AP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Département R3S, F-75013 Paris, France.

(4) Sorbonne Université, INSERM, UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, F-75005 Paris, France.

(5) AP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Service de Pneumologie, Département R3S, F-75013 Paris, France.

(6) Yale School of Medicine, Child Study Center, QUALab qualitative and mixed methods lab, New Haven, CT, USA

(7) Inserm U1018, Team DevPsy, Maison de Solenn, Hôpital Cochin, AP-HP, Paris, France.

(8) AP-HP, Groupe Hospitalier Universitaire APHP-Sorbonne Université, Fédération "Soins Palliatifs, Accompagnement et Soins de Support" F-75013 Paris, France.

## Corresponding author

Dr Laure Serresse, MD

Fédération "Soins Palliatifs, Accompagnement et Soins de Support"

Groupe Hospitalier Universitaire APHP-Sorbonne Université,

Hôpital Pitié-Salpêtrière

47-83 Bd de l'Hôpital, 75651 Paris Cedex 13, France

Telephone +33 1 42167565

E-mail: laure.serresse@aphp.fr

## Manuscript metrics

Abstract word count: 273

Manuscript word count: 2802

References: 36

Table: 1

Figures: 3 (all in color)

Electronic supplement: one color figure (ES1); additional text (ES2)
**Abstract**

**Background:** Dyspnea invisibility, namely the insufficient appreciation by others of the existential experience of those afflicted, constitutes a barrier between patients with chronic respiratory diseases and the level of care they require. Applying an interpretative phenomenological analysis (IPA) approach to the discourses of patients with severe chronic obstructive pulmonary disease (COPD), we recently introduced the notion of several dyspnea invisibilities depending on temporality, disease severity, the nature of the interlocutors, and the drivers involved, including the difficulty of sharing the dyspneic experience, insufficient awareness, and inadequate solicitude (Serresse et al., Palliative medicine 2022). Here, we aimed to corroborate this concept through a complementary methodology.

**Methods:** Quantitative lexicometric analysis (lemmatization, descending hierarchical classification, multicomponent analysis, similarity analysis) of previously gathered patients' discourses (6 men, 5 women; severe COPD–GOLD 3 and 4–; hospitalized for immediate post-exacerbation rehabilitation). Confrontation of the derived semantic classes and communities with IPA-derived themes (e.g. "envisioning one's death by suffocation"; "losing autonomy and hope"; "coping strategies"; "others' lack of awareness"; "an unshareable life experience"; "others' lack of empathetic concern").

**Results:** Four distinct semantic classes were identified (Class#1, "experience and need for understanding"; 38.9% of the semantic forms; half of the patients; Class#2, "limitations"; 28.7% of the forms; Class#3, "management"; 13.1%; Class#4, "hospitalisation"; 18.2%). These four classes explained 73% of the variance of the lexical corpus. Fourteen semantic communities were also identified, of which six represented 70.31% of the corpus. A high level of concordance between semantic classes and communities and IPA-identified themes was observed.

**Conclusions:** An independent, quantitative methodology confirms the pleomorphic nature of dyspnea invisibility, strengthening the idea that there are multiple ways to correct the corresponding injustice.

**Clinical Trial Registration:** not applicable.

**Key words**

Dyspnea; breathlessness; persistent breathlessness; chronic obstructive pulmonary disease; rehabilitation; integrative medicine; palliative medicine; lexicometry.
Introduction

Dyspnea, defined as a 'subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity' [1]), is the heavier of the many burdens that patients with chronic respiratory diseases carry. Arising from an upsetting or distressing awareness of breathing, dyspnea is indeed among the worst human sufferings. Beyond a symptom alerting on impaired cardiorespiratory function, it constitutes an afflictive existential experience in itself [2, 3]. This becomes particularly true when etiopathogenic treatments fail to relieve it, which defines persistent dyspnea [4, 5]). Persistent dyspnea is associated with anxiety, fear, and depression. Aggravated by sentiments of helplessness and unworthiness [6, 7], it leads to social isolation, delineating the narrowing perimeter of patients' thoughts and lives.

The burden of persistent dyspnea is also worsened by its invisibility, namely the
insufficient appreciation by others of what dyspnea represents for those afflicted [2, 3]. Patients
with persistent dyspnea complain of poor understanding from others and generally report a
lack of solicitude, particularly from healthcare professionals [8]. Dyspnea invisibility leads to
injustice by depriving patients of access to adequate care [9], and, more generally, raises
human rights issues [10]. Increasing awareness of the impact of persistent dyspnea is,
therefore, a fundamental clinical and societal issue.

In a qualitative study conducted on patients with severe chronic obstructive pulmonary
disease (COPD), we previously characterized the nature of dyspnea invisibility as pleiomorphic
and depending on temporality and interlocutors [11]. We observed that dyspnea could be
invisible as a symptom to the patients themselves and their entourage, mainly through
rationalization mechanisms. We also observed that dyspnea could be invisible as an
experience, being impossible to share, detached from objective lung function measurements,
and that does not generate empathic concern. We concluded that there were not one but
several dyspnea invisibilities, opening several avenues to address the issue. We conducted
this study using an interpretative phenomenological analysis approach (IPA) [11], a research
method focused on exploring someone's inner world to gain a deeper understanding of a
particular aspect of human experience [12]. From the contents of semi-structured interviews,
common patterns are delineated, and themes are created that capture the participants' shared
experiences. Our study [11] identified four themes pertaining to living with COPD-related
dyspnea (envisioning one's death by suffocation; losing autonomy and hope; coping strategies;
being exhausted by a long-lasting burden) and five themes pertaining to dyspnea invisibility
(having been fooled by the insidious nature of dyspnea as a warning sign; others' lack of
awareness; an unshareable life experience; suffering that cannot be objectively measured;
others' lack of empathetic concern).
The present ancillary study reports a quantitative lexicometric analysis of the semi-
structured interviews conducted before [11], performed to corroborate the results of the
previously published interpretative phenomenological analysis. Quantitative lexicometry is a
heuristic approach that complements qualitative hermeneutic methods. It consists of a corpus-
driven approach that deploys computer-assisted linguistic methods and specialized algorithms
(including correspondence analysis, descending hierarchical classification, and other
methods) to analyze a given corpus's content exhaustively. It does so by formally reorganizing
text sequences to explore lexicosemantic macro-structures and contrast different parts of the
corpus [13]. Lexicometric analysis allows researchers to examine the content of participants'
discourse and their wording [14], resting upon the notion that recurrences are highly pertinent
to identify consistent notions across individuals' discourses. In this study, we hypothesized that
quantitative lexicometry would identify semantic classes and communities corresponding to
the themes previously retained by the IPA [11].

Methods

General methodology.

The detailed methodology followed to gather the patients' interviews appears in the
original publication [11]. In summary, we performed the study in the pulmonary rehabilitation
division of the *Department of Respiratory Medicine* at the Pitié-Salpêtrière Hospital, a 1600-
bed university hospital in Paris, France. Inclusion criteria were 1) age 18 or more; 2) severe
COPD (GOLD classification stage 3 or 4 [15]); 3) rehabilitation immediately after severe COPD
exacerbation; 4) no known or obvious cognitive deficiencies; 5) adequate command of French.
The participants were informed of the purpose and methods of the study. They provided written
consent to participate. The study was approved by the ethical committee of Sorbonne
University (*Comité d'Éthique de la Recherche*, decision #19-621). Face-to-face semi-
structured interviews were conducted between September 2019 and May 2020 in 11
consecutive patients (6 men, 5 women; age 71 [64.5-73], forced expiratory volume in 1 s –
FEV1– 30%[19.5-36.5])[see Table 1 in11]. The median interview duration was 48 minutes
(interquartile range 34.5-51). The interviews were recorded and transcribed verbatim for the
purpose of the IPA [11] and the lexicometric analysis (this study).

Lexicometric analysis.

The lexicometric analysis was conducted by one of the investigators (JD), who
specializes in this field of research. The lexical corpus was first expunged from the interviewer's
interventions. It was then lemmatized, a process that reduces the different forms of a word to
a single one (the "lemma") by removing inflectional differences (e.g., "talks", "talking", "talked"
are reduced to "talk"). The resulting output was automatically divided into units of context
based on the number of occurrences and punctuation [16]. Next, matrices crossing individuals
and units of context/lemmas (grammatical words such as articles and pronouns excluded)
were constituted and explored with descending hierarchical classification and multiple
component analysis [16, 17]. Finally, similarity analysis was performed by generating a list of
co-occurrences and creating a network to detect semantic communities [18]. The analysis was
performed with the IRaMuTeQ 0.7 alpha 2 R-based software (French dictionary; Laboratoire
d'Études et de Recherches Appliquées en Sciences Sociales, Université de Toulouse 3,
France) and the UCLouvain community detection algorithm [18].

Concordance between interpretative phenomenological analysis and lexicometry

The IPA and the lexicometric analysis results were reviewed by three researchers (LS,
who had conducted the interviews and led the IPA process; JD, who conducted the
lexicometric analysis; TS) and tabulated against each other according to thematic
concordance.

Results

Structure of the corpus

A first analysis of the lemmatized corpus showed that one patient's dataset stood out in
a self-contained semantic class that did not intersect with the others. The corresponding patient
had a correct mastery of French but was not a native French speaker and appeared to use a
limited vocabulary and many generic items. This dataset was therefore removed from the initial
corpus. The final corpus, from 10 interviews with ten patients, comprised 41475 words (3488
unique forms or lemmas). It was decomposed into 1157 segments of 35.85 forms on average.

Hierarchical descending classification

Hierarchical descending classification allocated 90.92% of the segments (n = 1052) to 4 distinct classes (Figure 1). In class 1 ("experience and need for understanding"; 38.9% of the segments; half of the patients), the most important terms were "patient", "thinking", "understanding", "caregiver", "life"; "breathlessness", "suffering". This class also importantly relates to patient's needs and their difficulties in having their illness understood and accepted, in particular by the medical profession ("question", "talk", "difficulty"). Words in class 2 ("limitations"; 28.7% of the text segments; strongly driven by two patients) revolved around the daily limitations in performing basic activities ("go", "walk", "fall", "lose", "problem", "breathlessness", "die"). Class#3 ("management", 13.1% of the text segments) was organized around disease management and the importance of taking charge and regaining by accepting or adapting to the constraints of the disease ("take", as in "take a drug", or "take charge", "antibiotic"; "learn," consistent with a rehabilitation context involving therapeutic education).
Class#4 ("hospitalization"; 18.2% of the segments) was centered on the concrete experience of the exacerbation-related.

### Multicomponent factorial analysis.

In multicomponent factorial analysis, the projection of the four semantic classes on two axes explained 73% of the variance of the corpus (41.04% on the horizontal axis, 32.13% on the vertical axis; Figure 2). On the horizontal axis (41.04%), Class#1 ("experience and need for understanding") is opposed to the three other classes ("limitations", "management", "hospitalization"). On the vertical axis (32.13%), Class#2 ("limitations") and 3 ("management") largely overlap, while Class#2 and 3 appear opposed to class 4, indicating that the experience of hospitalization has a specific place in the patients' discourse.

### Similarity analysis

Similarity analysis detected 14 semantic communities (see word cloud in electronic supplement ES1) with overall modularity of 0.838, indicating strong connections between within-community terms and weaker connections between between-community terms. Six communities represented 70.31% of the corpus. A detailed interpretation is provided in the electronic supplement (ES2). In summary, a "seeing" community (20.53%), corresponding to the "invisibilities" IPA themes, was centered on "seeing" and involved terms such as "doctor", "patient", "people", "need", "think" and "talk". A "Take" community (13.5%) was articulated with the notions of "care", "management", "self-care", "learning" and corresponded to the "coping strategies" IPA theme. A "Thing" community (11.95%) was associated with "breathing", "happening", "understanding", "feeling", "life" and "death", and was therefore reminiscent of the "envisioning one's death by suffocation" IPA theme. A "Disease" community (9.42 %), also consistent with the invisibilities IPA theme, concentrated on COPD as an entity, with emphasis on the need for better "knowledge" from "the doctors" and "society". A "hospitalization" community (8.44%) concentrated on stories of hospitalizations, with emphasis on the "first time" and "intensive care". Finally, a "Feel" semantic community (6.47%) related to the existential experience of dyspnea, associated with suffering (pain/dyspnea, life/death, in coherence with the "envisioning one's death by suffocation" IPA theme). This community is also related to the impossibility of being able to share the experience with others, in coherence with the "unshareable life experience" IPA theme.

### IPA-lexicometry concordance

Table 1 summarizes the concordance between the IPA themes and the semantic classes and community. Of note, words pertaining to dyspnea invisibilities were found in all the four semantic classes, and semantic Class#1, while mostly revolving around IPA theme #6
(others' lack of awareness), contained words and notions related to all five IPA invisibility themes.

# Discussion

## Summary of findings.

The results of this quantitative linguistic analysis corroborate the conclusions previously derived from the qualitative IPA approach conducted on the same dataset [11]. Indeed, these results emphasize the two central notions identified by the IPA, namely that 1) living with COPD-related persistent dyspnea is a deteriorative existential experience imprisonment patients in the threatening obsession of breathing; 2) the various facets of dyspnea invisibility worsen the burden of the disease. In addition to its corroborating value, the lexicometric analysis brings some complementary information. It sheds light on dyspnea invisibility as a separate concern, distinct from the matters related to the disease's experience. It also points to hospitalization as a specific issue not readily identified by the IPA.

## Existing literature.

Simple quantitative textual analysis is not uncommonly used as an adjunct to qualitative studies relying on grounded theory, IPA, or other approaches, to help researchers select relevant discourse themes. Studies relying on the more sophisticated lexicometric analysis used here as their principal methodology are rare. We have been unable to identify any such study addressing COPD, or, more generally, chronic respiratory diseases, even though qualitative studies are becoming more common in this field [to quote a few examples: 6, 19-22]. Examples of lexicometric studies exist in various domains (the experience of families of people with diabetes [23]; fathers' role in supporting breastfeeding in preterm infants [24]; women's participation in human immunodeficiency virus clinical trials [25]; patients' experience after the onset of dialysis [26], etc.). Some of these studies include various degrees of assessment of the complementarity between quantitative lexicometry and qualitative analyses. Likewise, Montalescot et al. [26], investigating patients' experiences one year after dialysis initiation, confronted their lexicometric results with an inductive analysis and had them assessed and discussed from the perspective of the raw interviews to strengthen the interpretation of the identified semantic classes. In this regard, the results of the present lexicometric analysis cannot be dissociated from those of the previously published IPA [11] and will be examined through this prism.

## Comparison between present and previous results [11]

In the present study, the hierarchical descending classification and the similarity analysis strengthen the conclusions of the IPA. Regarding the experience of living with COPD-related persistent dyspnea, the semantic Class#1 ("experience and need for understanding") and the
semantic community #3 ("thing", i.e. "the disease"), and to a lesser extent, Class#4 ("hospitalization") and communities #5 ("hospitalization") and #6 ("feel") overlapped with IPA theme #1 ("envisioning one's death by suffocation"). Class#2 ("limitations") and Class#3 ("management") were very close to theme #2 ("losing autonomy and hope") and #3 ("coping strategy"), respectively. Interestingly, Class#4 appeared centered on hospitalization ("hospital", "there" -about the respiratory medicine wards where the patients came from), the related fear, or the relations with the different actors such as the physiotherapists during the current rehabilitation stay. As such, Class#4 ("hospitalization") relates with IPA theme #1 ("envisioning one's death by suffocation"), but the IPA did not isolate hospital stays as specific concerns. Yet, in multicomponent analysis, Class#4 was opposed to Class#2 and Class#3, indicating that hospital stays have a specific place in the patient's discourse. This dimension of the patients' experience was not as clear in the IPA results. Of note, the large overlap of Class#2 ("limitations") and Class#33 ("management") (Figure 2) suggests concomitant discourses and possibly the difficulty of differentiating between the expression of a problem and its resolution. In other words, when talking about disease-related difficulties, patients also discuss coping means.

Regarding dyspnea invisibilities, all classes contained somewhat relevant forms. Yet, Class#1 ("experience and need for understanding"), comprising 38.03% of the forms in the corpus and explaining 41.04% of the variance in multicomponent analysis, tightly covered IPA theme #6 ("others' lack of awareness"). This class emphasizes the need for understanding and the patients' difficulties in having their illness understood and accepted, in particular by the medical profession ("question", "talk", "difficulty"). Of importance, the multicomponent analysis clearly shows (Figure 2) that, on the horizontal axis, Class#1 is opposed to the three other classes ("limitations", "management", "hospitalization"). This pattern shows that the patients place the need for understanding on a separate plane. In that, the lexicometric analysis does justify the identification of dyspnea invisibility as a specific and self-contained worry of the patients. Five of the six main semantic communities identified (ES1, ES2) bore a close relationship to the five invisibility-related IPA themes (Table 1). The notion of invisibility was particularly present in the "seeing" community (20.53% of the lexical corpus). The notion of unshareability was well reflected in the "feeling" semantic community. Of note, IPA theme #8 ("a suffering that cannot be objectively measured"), which was present in the discourse of 6 out of 11 patients [11] and is considered an important driver of dyspnea invisibility [3, 27], was not clearly visible within the descending hierarchical classification and did not appear as such within the 6 main semantic communities. This appears to be the only important divergence between the present and the previous results [11].

## *Study limitations.*

The size of our study population (n=10) is small in comparison to other studies having used similar lexicometric approaches [23, 25, 26, 28-32] where the number of participants ranged from
17 to more than 100. This prevented us from testing for statistical associations between semantic
outputs and patients' characteristics. Despite this, the size of our corpus (41475 words and 3488
unique forms in 10 patients) is of the same order of magnitude that of some of these other studies
(62467 words in 22 patients in a rather comparable study in chronic renal failure patients [26]).
Also, more than 90% of the corpus was allocated in the four classes defined by the hierarchical
descending classification process. In a study of patients with chronic renal failure requiring
dialysis, Montalescot et al. [26] reported a 84% such repartition, considering it "very satisfying"
compared with the 60-75% figures reported in similar studies. We believe this is a reflection of the
very homogeneous nature of our patients (advanced COPD in the very specific context of early
post-exacerbation rehabilitation). Still, we acknowledge that this limits the generalisability of the
results. We acknowledge that because of the exclusion of one patient due to limited vocabulary,
the corpus used for the lexicometric analysis is not the same as the corpus used for the IPA. We
also acknowledge that we did not formally assess the semantic language abilities of our patients.
Yet language dysfunction has been identified in COPD patients and correlated with hypoxemia
[33], which could have interfered with our results.

Conclusions

Dyspnea invisibility constitutes a major barrier between patients and the adequate care they require [9, 19, 34]. Although put in the spotlight in recent years [2, 3, 35, 36], the amount of corresponding data remains scarce. Our previously published study [11] introduced the notion of several dyspnea invisibilities depending on temporality, disease severity, the nature of the interlocutors, and the drivers involved, including the difficulty of sharing the dyspneic experience, insufficient awareness, and inadequate solicitude. From this, we proposed that these elements constituted as many avenues for devising interventions to lift dyspnea invisibility and remedy the corresponding injustice. It is, therefore, reassuring to see the present analysis comforting these conclusions and propositions.

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