1
Current situation of management of spontaneous pneumothorax in Japan: A crosssectional cohort study
Authors:
Hitoshi Igai1), Noriyoshi Sawabata2), Toshiro Obuchi3), Noriyuki Matsutani4),
Kenji Tsuboshima5), Shouichi Okamoto6), Akihiro Hayashi7)
Institution:1) Department of General Thoracic Surgery, Japanese Red Cross Maebashi Hospital, 3891 Asakura, Maebashi, Gunma 371-0811, Japan
2) Department of Thoracic and Cardio-Vascular Surgery, Nara Medical University School of
Medicine, 840 Shijo-cho, Kashihara, Nara 634-8511, Japan
3) Department of Thoracic Surgery, St. Mary’s Hospital, 422 Tsubukuhonmachi, Kurume,
Fukuoka 830-8543, Japan

4) Department of Surgery, Teikyo University Hospital, Mizonokuchi, 5-1-1 Futago, Takatsu,
Kawasaki, Kanagawa 213-8507, Japan
5) Pneumothorax Research Center and Division of Thoracic Surgery, Nissan Tamagawa
Hospital, 4-8-1 Seta, Setagaya, Tokyo 158-0095, Japan.
6) Department of Respiratory Medicine, Saiseikai Ibaraki Hospital, 2-1-45 Mitsukeyama,
Ibaraki, Osaka 567-0035, Japan27) Department of General Thoracic Surgery, Shin Koga Hospital, 120 Tenjin, Kurume,
Fukuoka, Japan
Corresponding Author: Hitoshi Igai
389-1 Asakura-cho, Maebashi, Gunma 371-0811, Japan
Phone: +81-27-265-3333
FAX: +81-27-225-5250
e-mail: hitoshiigai@gmail.com
Meeting presentation: The abstract will be presented at the 37th Annual Meeting of theEuropean Association for Cardio-Thoracic Surgery, 4-7 October 2023, Vienna.
Word count: 2898 words

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Abstract
Background: Limited epidemiological information is available on spontaneous
pneumothorax. To address this gap, the Japan Society for Pneumothorax and Cystic Lung
Disease (JSPCLD) conducted a nationwide retrospective survey to investigate the current
epidemiology of spontaneous pneumothorax in Japan.
Methods: In this study, we conducted a retrospective cross-sectional cohort study todemonstrate the clinical features of spontaneous pneumothorax in one year from April 2019
to March 2020, compare patient characteristics and treatment outcomes between primary(PSP) and secondary spontaneous pneumothorax (SSP), and investigate the risk factors
associated with in-hospital mortality among patients with SSP.
Results: A total of 1784 patients from 28 institutions were enrolled in the study, with PSP
observed in 956 cases (53.6%) and SSP in 817 cases (45.8%). The age distribution
showed a biphasic peak caused by the different peaks between PSP and SSP. In-hospitalmortality occurred in 42 cases (2.4%) among all patients, with 0 cases (0%) in PSP and 42
cases (5.1%) in SSP. Multivariable analyses revealed that interstitial pneumonia as anunderlying disease (odds ratio: 2.3300, 95% confidence interval: 1.0600 to 5.1100,
p=0.0354), performance status≧3 (odds ratio: 6.8600, 95% confidence interval: 3.0400 to
15.4000, p<0.0001), and lower value of serum albumin on admission (odds ratio: 0.3260,
95% confidence interval: 0.1860 to 0.5710, p<0.0001) were significantly associated with inhospital mortality among patients with SSP.

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Conclusions: SSP patients with poor baseline conditions are at a higher risk for in-hospitalmortality. It is crucial to provide close and meticulous management for SSP patients withcompromised conditions.
248 words
Keywords: current situation, management, spontaneous pneumothorax, in-hospitalmortality, Japan5
1. Introduction
Pneumothorax is a common condition encountered by pulmonologists and general thoracic
surgeons. It occurs when air or gas from a pulmonary fistula accumulates in the pleuralcavity, leading to lung collapse and impaired respiratory function in affected patients (1,2).
Pneumothorax is typically classified into two types: spontaneous and traumatic. The
spontaneous type can be further categorized as primary spontaneous pneumothorax(PSP), which occurs without underlying lung disease, and secondary spontaneous
pneumothorax (SSP), which occurs in the presence of underlying lung disease. Patientcharacteristics, initial management, and treatment outcomes differ between PSP and SSP(1,2).
Patients with PSP often experience mild symptoms, as subpleural blebs and bullae in anotherwise healthy lung contribute to the lung collapse (3,4). In contrast, patients with SSP
frequently exhibit severe symptoms even with minimal lung collapse due to compromised
pulmonary function resulting from underlying lung disease. SSP is usually associated withhigher morbidity and mortality compared to PSP. The British Thoracic Society (BTS)
guidelines recommend outpatient follow-up for asymptomatic patients with PSP, whileemphasizing that all patients with SSP should be admitted to the hospital for a minimum of
24 hours (5). Regarding surgical intervention, the guidelines suggest discussing cases of

6
SSP with persistent air leak with a thoracic surgeon within 48 hours, while noting limited
effectiveness of thoracoscopic salvage operation after failed chest drainage for PSP.
Despite the differences in clinical features between PSP and SSP, there have been only a
few large-scale nationwide studies describing these characteristics (6-10). Consequently,
the epidemiological information on spontaneous pneumothorax remains limited. To address
this knowledge gap, the Japan Society for Pneumothorax and Cystic Lung Disease(JSPCLD) conducted a nationwide retrospective survey to investigate the epidemiology of
spontaneous pneumothorax in Japan. The specific objectives of this study were to compare
patient characteristics and treatment outcomes between PSP and SSP, as well as to
identify risk factors associated with in-hospital mortality among patients with SSP.

2. Patients and methods
2.1.

Design, setting, and data collection

The study was approved by institutional ethics board of Japanese Red Cross Maebashi
Hospital (approval no. 2021–19, date: 21, June, 2021). For the retrospective observational
study, the requirement for written informed consent was waived owing to the use ofanonymized retrospective data. Additionally, this study adhered to an opt-out consent
model, which allowed participants to withdraw their consent and delete their informationfrom the registry at any point.

7
We conducted a retrospective cohort study to examine the clinical features of spontaneous
pneumothorax, compare patient characteristics and treatment outcomes between PSP and
SSP, and investigate the risk factors associated with in-hospital mortality among patientswith SSP.
Between April 1, 2019, and March 31, 2020, we extracted data on hospitalized cases withthe code number "040200" indicating "pneumothorax" from the Diagnosis Procedure
Combination (DPC) database. The DPC is a nationwide administrative hospital discharge
data in Japan, and it has been widely utilized for large clinical trials in Japan (11,12). Thispatient classification system is linked to a flat-rate payment system for inpatients in acutecare hospitals and was initially developed in Japan in 2002 (13). Cases of traumatic,
iatrogenic, or neonatal pneumothorax were excluded from the extracted data. We included
patients with spontaneous pneumothorax who were originally admitted for other diseases,
and their total hospitalization time encompassed the treatment period for both conditions. It
is important to note that the date of admission could fall within the specified time frame, but
the treatment duration could extend beyond April 1, 2020.
Following the extraction of eligible cases using the DPC data, clinicians at each institution
completed a case report form, providing information on the clinical features, which was thensent to the central coordinating office.
2.2.

Study variables

8
The following variables were collected using a case report form: mode of onset (first,
recurrence, unknown), type of pneumothorax (primary, secondary, unknown), underlying
pulmonary disease in SSP (chronic obstructive pulmonary disease, interstitial pneumonia,
combined pulmonary fibrosis and emphysema, pulmonary malignancy, pulmonary infection,
catamenial, others), home oxygen therapy (+, -), comorbidities except for pulmonary
disease (impaired liver function; Child-Turcotte classification≥B, hemodialysis, ischemic
heart disease, malignancy treated within 5 years, cerebrovascular disease, diabetes
mellitus, anemia; hemoglobin value ≤ 8g/dL, autoimmune disorder, arrhythmia,
hypertension, others), administration of steroid on admission (+, -), affected side (left, right,
bilateral), age (years), gender (female, male), performance status (0, 1, 2, 3, 4, unknown),body mass index (BMI), smoking index (pack-years), serum C-reactive protein (CRP) on
admission (g/dL), serum albumin on admission (g/dL), degree of lung collapse (mild,moderate, severe, unknown), thoracography (+, -), chest tube drainage (+, -), pleurodesis(+, -), administrative agents used in pleurodesis (OK-432, Minocycline, autoblood, talc,
glucose solution, others), trans-airway procedure (+, -), surgical intervention (+, -), surgicalapproach (thoracoscopy, thoracotomy, unknown), treatment in the intensive care unit (+, -,unknown), total hospitalization time (days), and discharge outcome (home, transferred toanother hospital, death).

9
Underlying pulmonary disease was decided by each institution based on the radiographic
findings and the medical record.
The degree of lung collapse was defined as follows：
1. Mild: Air space was seen only in the apex of the lung on chest X-ray.
2. Moderate: The lung was collapsed to a degree between mild and severe on chest X-ray.
3. Severe: The lung was completely collapsed on chest X-ray.
Performance status was determined according to the criteria published by the Eastern
Cooperative Oncology Group (14).
2.3.

Statistical analysis

Initially, the characteristics, treatments, and outcomes of all enrolled patients withspontaneous pneumothorax were summarized. In addition, the age distribution of theenrolled spontaneous pneumothorax patients was evaluated. Subsequently, all patientswere classified into two groups: PSP and SSP. We compared the clinical features between
the two groups using univariate analyses. Moreover, the underlying pulmonary diseases inpatients with SSP were listed. Next, patients with SSP were classified into two groups:
those receiving surgical intervention and those not receiving surgical intervention. We
compared the clinical features between the two groups using univariate analyses. Finally,
we used multivariate analysis to identify the factors associated with in-hospital mortality.

10
We analyzed continuous variables using the Mann-Whitney U test and categorical variables
using Fisher’s exact test. Multivariate analyses were performed using a logistic regression
model. Results were considered significant at p < 0.05. Calculations and statistical tests
were performed using the EZR graphical user interface (Saitama Medical Centre, Jichi
Medical University, Saitama, Japan).

3. Results
3.1.

Study population

The JSPCLD invited 63 institutions in Japan to participate in this retrospective multiinstitutional study, and 28 institutions (44.4%) agreed to participate. The 28 institutions
provided completed case report forms for 1784 patients who were diagnosed with"pneumothorax" during hospitalization between April 1st, 2019 and March 31st, 2020.
Ultimately, data from the 1784 patients were analyzed. Figure 1 illustrates the patient
enrollment process.
3.2.

Characteristics, treatments, and outcomes of patients with spontaneous
pneumothorax

Table 1 presents the characteristics, treatments, and outcomes of all enrolled patients withspontaneous pneumothorax during the study period (n=1784). Among them, 956 cases(53.6%) were PSP and 817 cases (45.8%) were SSP. The male-to-female ratio was11approximately 4:1. Surgical intervention was performed for 1149 cases (66.5%), and 96.8%of these cases received a thoracoscopic approach. In-hospital mortality occurred in 42
cases (2.4%) among all patients.
3.3.

Age distribution of spontaneous pneumothorax

Figure 2 shows the age distribution of the enrolled all 1784 spontaneous pneumothorax
patients. The gray bars represent the number of PSP patients, showing a monophasic trendwith a peak observed between the ages of 20 and 29 years. The orange bars represent the
number of SSP patients, also exhibiting a monophasic trend with a peak observed between
the ages of 70 and 79 years. The dotted line represents the overall trend of all spontaneous
pneumothorax cases, including both PSP and SSP. It shows a biphasic pattern, resulting
from the different peak ages between PSP and SSP.
3.4.

Comparison of characteristics, treatments, and outcomes between patients withPSP (n=956) and SSP (n=817)

Since the subtype of pneumothorax was unknown in 11 cases, a total of 1773 cases wereanalyzed. Table 2 presents a comparison of the characteristics, treatments, and outcomes
between patients with PSP (n=956) and SSP (n=817). Significant differences wereobserved between the two groups in most of the variables. SSP patients generally had
more compromised backgrounds compared to PSP patients. Surgical intervention was
more frequently performed in PSP, whereas pleurodesis was more commonly performed in12
SSP (PSP: 79.1%, SSP: 52.5%, p<0.0001). Furthermore, a higher proportion of SSP
patients underwent thoracotomy approach compared to PSP (PSP: 1.2%, SSP: 5.6%,
p<0.0001). The length of hospital stay was significantly longer in SSP (PSP: 8 days, SSP:
13 days, p<0.0001). In-hospital mortality occurred in 0 cases (0%) in PSP and 42 cases(5.1%) in SSP (p<0.0001).
3.5.

Underlying pulmonary disease

Supplementary table 1 lists the underlying pulmonary diseases in patients with SSP(n=817). The highest proportion of patients had COPD (53.6%), followed by interstitial
pneumonia (15.5%) and lung cancer (11.8%).
3.6.

Comparison of clinical features between SSP patients with (n=429) and without
surgical intervention (n=388)

The characteristics, treatments, and outcomes of SSP patients with (n=429) and without
surgical intervention (n=388) were compared in Supplementary table 2. The proportion ofunderlying lung diseases, including interstitial pneumonia (surgical group: 10%, nonsurgical group: 21.6%, p<0.0001), and pulmonary infection (surgical group: 4.9%, nonsurgical group: 16.5%, p<0.0001), was significantly higher in the non-surgical group.
Additionally, the non-surgical group had a significantly higher proportion of patients withcoexisting impaired liver function (surgical group: 0.2%, non-surgical group: 2.3%,
p=0.0083), ischemic heart disease (surgical group: 6.5%, non-surgical group: 11.3%,

13
p=0.0185), malignancy (surgical group: 11.2%, non-surgical group: 16.2%, p=0.0407),
cerebrovascular disease (surgical group: 6.1%, non-surgical group: 15.5%, p<0.0001),
arrhythmia (surgical group: 6.3%, non-surgical group: 10.6%, p=0.0310), and hypertension(surgical group: 23.5%, non-surgical group: 36.9%, p<0.0001). Furthermore, the nonsurgical group had lower BMI (surgical group: 19.8, non-surgical group: 19, p=0.0001),
higher CRP on admission (surgical group: 0.3 g/dl, non-surgical group: 0.8 g/dl, p<0.0001),
and lower serum albumin on admission (surgical group: 4 g/dl, non-surgical group: 3.7 g/dl,
p<0.0001). In-hospital mortality was 8.2% in the non-surgical group compared to 2.3% in
the surgical group (p<0.0001).
3.7.

Risk factor associated with in-hospital mortality among the patients with SSP

Supplementary table 3 demonstrates univariable and multivariable analyses to identify
factors associated with in-hospital mortality in patients with SSP. In the multivariable
analyses, interstitial pneumonia as an underlying disease (odds ratio: 2.3300, 95%
confidence interval: 1.0600 to 5.1100, p=0.0354), performance status≥3 (odds ratio: 6.8600,
95% confidence interval: 3.0400 to 15.4000, p<0.0001), and lower serum albumin levels on
admission (odds ratio: 0.3260, 95% confidence interval: 0.1860 to 0.5710, p<0.0001) weresignificantly associated with in-hospital mortality among patients with SSP.

4. Discussion

14
In the present study, we investigated the epidemiology of spontaneous pneumothorax inJapan, the differences in clinical features between PSP and SSP, and the risk factors
associated with in-hospital mortality among SSP patients. In Japan, almost 80% of all
spontaneous pneumothorax were male, which is consistent with other previous nationwide
reports (Korean report: 81.5%, French report: 76.6%, and previous Japanese report:
82.4%)6)7)10). The ratio between PSP and SSP was described only in the French report, inwhich SSP occupied only 15% of all patients with spontaneous pneumothorax, while it was
45.8% in our study6). As the registered cases were extracted from DPC, cases in which
pneumothorax occurred as a secondary condition to other diseases were also included,
which might be the cause of the difference. In our study, 66.5% of the patients underwent
surgical intervention, 96.8% of which were thoracoscopic procedures. In contrast, only 24%of the patients underwent surgery in the French report, which collected data between 2008
and 2011 (6). We speculate that the difference might be due to the variation in those study
periods. Compared to the last decade, most surgical interventions for patients withspontaneous pneumothorax are now performed using thoracoscopic approaches due totechnological advancements and improved technical skills (15,16).
Regarding the comparison of clinical features between patients with PSP and SSP, mostof the variables were significantly different between PSP and SSP, indicating that theclinical conditions were markedly distinct between the two conditions. Specifically, patient

15
backgrounds were more compromised and clinical outcomes were worse in SSP than inPSP. This might explain why the rate of patients with SSP receiving surgical intervention
was lower than that of PSP, and the rate of patients with SSP receiving pleurodesis washigher. Moreover, the rate of patients with PSP receiving surgical intervention differedconsiderably from the French epidemiological report of 2015 (6). While 79.1% of PSP
received surgical intervention in this study, only 23% of PSP did so in the French report. In
European countries, observation is often preferred for PSP, as recommended by BTS
guidelines (5). In contrast, surgical intervention is more commonly selected for PSP in
Japan based on the excellent intra- and postoperative outcomes for PSP after the
emergence of less invasive thoracoscopic approaches (17-19).
Among patients with SSP, the most frequent underlying pulmonary disease was COPD,
which is consistent with many previous publications (6,7,20,21). The second most frequent
underlying pulmonary disease was interstitial pneumonia, which is consistent with previous
Japanese studies but differs from results in other countries. For example, Kim et al.
reported that the second most frequent underlying pulmonary disease was pneumonia, andasthma ranked third in a Korean nationwide study (7). In their report, only 0.7% of patientswith spontaneous pneumothorax had interstitial pneumonia as an underlying pulmonary
disease. Wang et al. demonstrated that the second most frequent underlying pulmonary
disease was lung malignancy among SSP patients, while interstitial pneumonia ranked third16
in a United States nationwide study (22). The discrepancy between these previous reports
and ours indicates that the frequency of underlying pulmonary disease varies, and this may
depend on cultural, social, and other factors in each country.
In the BTS guideline, patients with a persistent air leak should consult a thoracic surgeon
to plan surgical intervention (5). However, in our cross-sectional nationwide study, surgicalintervention was performed only for 52.6% of all SSP patients. SSP patients without
surgical intervention were older, received more home oxygen therapy, had lower albuminvalues, higher CRP values, and lower BMI. This indicates that conservative treatment
tended to be selected for compromised SSP patients. This tendency was consistent with
Wang’s previous report (22). Although they described that same-admission pneumothorax
recurrence prophylaxis including surgical intervention was associated with lower odds of inhospital mortality, the prophylaxis was performed for only 33.73% of all SSP patients.
Patients without prophylaxis were older and more compromised than those who received it.
Moreover, the group without surgical intervention in our study included significantly morepatients with interstitial pneumonia than the group that received surgical intervention.
Previous reports revealed that perioperative outcomes in patients with interstitial
pneumonia as an underlying disease were worse than those with other diseases, whichmight lead to avoiding surgical intervention in more patients with interstitial pneumonia (21).

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In this Japanese epidemiological study, the in-hospital mortality of patients with SSP was
5.1%. Although the treatment for SSP is considered challenging due to underlying
pulmonary disease or patient compromised condition, there have been only a few studies
describing the in-hospital mortality rate (20,21). Onuki et al. identified that emergency
transportation was significantly associated with in-hospital mortality (odds ratio: 16.37, pvalue<0.001) in a single-center retrospective study, and they concluded that patients with
SSP receiving emergency transportation should be carefully managed (20). Ichinose et al.
reported a hospital mortality rate of 3% in patients with SSP; however, their study included
only patients undergoing surgical intervention, which was different from our study (21).
Furthermore, the hospital mortality rate in patients with interstitial pneumonia as anunderlying disease was 15%, which was much higher than that in patients with COPD. Our
study also revealed that interstitial pneumonia as an underlying disease was significantly
associated with in-hospital mortality in multivariable analysis. Moreover, we found that alower performance status and serum albumin on admission might serve as indicators for inhospital mortality among SSP patients.
Although it is well known that the treatment of patients with SSP can be difficult, there
have been no nationwide studies that have addressed the rate of in-hospital mortality.
Additionally, in this study, cases were extracted from the DPC data, which allowed for the
inclusion of cases in which pneumothorax occurred while other diseases were primarily

18treated on admission. This selection method allowed for a non-biased representation ofenrolled patients. Furthermore, the study period was limited to a year, which minimized
bias. As a result, this study provides valuable insights into the current state ofpneumothorax in Japan.
The current study has several limitations. First, the study design was retrospective innature, although multiple institutions participated. Second, the database did not include
outpatient data because all the data were extracted from the DPC, which might haveaffected the clinical features of PSP and SSP. Third, the present study did not include all
spontaneous pneumothorax data in our country, although many institutions joined. This isbecause invitations to participate in the study were not sent to facilities that did not have a
JSPLCD council member on staff, which may have introduced selection bias. Fourth, theseverity of COPD or interstitial pneumonia, the dose of steroids administered, and thedetails of the lung infection were not assessed, although these may affect prognosis. Fifth,
the type of background disease was defined by each participating institution. For example,
the odds ratio in CPFE was better than that in interstitial pneumonia, although the prognosis
of CPFE was considered worse than that of interstitial pneumonia, indicating that the
number of CPFE might be underestimated.
5. Conclusion

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The present study provides valuable insights into the characteristics, management, andoutcomes of pneumothorax patients in Japan, with a particular focus on in-hospital mortality
in patients with SSP, which was found to be 5.1%. Multivariable analyses revealed thatinterstitial pneumonia as an underlying disease, performance status of 3 or higher, andlower serum albumin levels on admission were significantly associated with in-hospitalmortality among patients with SSP. These findings suggest that SSP patients with poor
baseline conditions are at a higher risk for in-hospital mortality, and that the above threevariables are important prognostic indicators.

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Conflicts of Interest
The authors have no conflicts of interest.
Acknowledgements
We would like to express our sincere gratitude to the following medical institutions for theirinvaluable support throughout this research: Seirei Mikatahara General Hospital, Tokyo
Teishin Hospital, Japanese Red Cross Okayama Hospital, Japanese Red Cross Maebashi
Hospital, Nissan Tamagawa Hospital, Tokyo Women's Medical University, Nara Medical
University, Kimitsu Chuo Hospital, Sapporo City General Hospital, Showa University
Northern Yokohama Hospital, New Tokyo Hospital, Juntendo University, Fukushima
Medical University, St. Mary's Hospital, Teikyo University Hospital Mizonokuchi, Nakagami
Hospital, Kansai Medical University Medical Center, Fukuoka Higashi Medical Center,
Kenkoukai Sogo Tokyo Hospital, Bell Land General Hospital, Kansai Medical University,
Hokkaido University, National Hospital Organization Himeji Medical Center, Toho
University, Shin Koga Hospital, National Hospital Organization Higashi-Ohmi General
Medical Center, Dokkyo Medical University, and Yodogawa Christian Hospital. Additionally,
we would like to thank (http://www.textcheck.com/jp/text/page/index) for revising the English
language.
Author contributions

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Hitoshi Igai: Conceptualization, formal analysis, investigation, and writing of the originaldraft. Noryoshi Sawabata: Conceptualization, writing, review, and editing. Toshiro
Obuchi: Writing, review, and editing. Noriyuki Matsutani: Writing, review, and editing.
Kenji Tsuboshima: Writing, review, and editing. Shouichi Okamoto: Writing, review, andediting. Akihiro Hayashi: Project administration

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Figure legends
Figure 1: The patient enrollment process in this retrospective study.
Figure 2: Age distribution of the patients with spontaneous pneumothorax in Japan.

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Table 1: Clinical features of patients with spontaneous pneumothorax.
Variables

Cases (n=1784)

Mode of onset
first/recurrence/unknown

1031 (57.8)/748 (41.9)/5 (0.3)

Type of pneumothorax
primary/secondary/unknown

956 (53.6)/817 (45.8)/11 (0.6)

Home oxygen therapy+/Comorbidities except for pulmonary disease+/-/unknown
Details of comorbidities except for pulmonary
diseaseImpaired liver function（Child-Turcotte classification≧B）
Hemodialysis
Ischemic heart disease
Malignancy（treated within 5 years）
Cerebrovascular disease
Diabetes mellitus
Anemia（Hb≦8g/dl）
Autoimmune disorder
Arrhythmia
Hypertension
Others91 (5.1)/1693 (94.9)

660 (37)/1120 (62.8)/4 (0.2)

13 (0)
9 (0.5)80 (4.5)
122 (6.8)
94 (5.2)
116 (6.5)
11 (0.6)
41 (2.3)77(4.3)281 (15.8)
368 (20.6)

Administration of steroid on admission+/-

91 (5.1)/1693 (94.9)

Affected side
left/right/bilateral

822 (46.1)/921 (51.6)/41 (2.3)

Age, median (IQR), years

40 (22-70)

GenderFemale/Male351 (19.7)/1433 (80.3)

28
Performance Status
0/1/2/3/4/unknown

1188 (66.6)/321 (18)/134 (7.5)/77 (4.3)/41 (2.3)/23 (1.3)

BMI, median (IQR),

19.2(17.4-21.2)

Smoking index, median (IQR), pack x year

0 (0-30)

Serum CRP on admission, median (IQR), g/dl

0.1 (0-0.7)

Serum albumin on admission, median (IQR), g/dl 4.3 (3.8-4.7)
Degree of the collapsed lung
mild/moderate/severe/unknown

394 (22.1)/900 (50.1)/446 (25)/44 (2.5)

Thoracography+/-

77 (4.3)/1707 (95.7)

Chest tube drainage+/-

1369 (76.7)/415 (23.3)

Pleurodesis+/-

167 (9.4)/1617 (90.1)

Administrative agents in the pleurodesis
OK-432
Minocycline
Autoblood
Talc
Glucose solution
Others64 (3.6)
46 (2.6)
42 (2.4)
14(0.8)108 (6.1)
18 (1)

Trans-airway procedure+/-

23 (1.3)/1761 (98.7)

Surgical intervention+/-

1187 (66.5)/597 (33.5)

29Surgical approach
thoracoscopy/thoracotomy/unknown

1149 (64.4)/33 (1.9)/5 (0.3)

Treatment in intensive care unit+/-/unknown

175 (9.8)/1606 (90)/3 (0.2)

Total hospitalization, median (IQR), days

9 (6-15)

Outcome at discharge
home/transferred to other hospital/death

1651 (92.5)/91 (5.1)/42 (2.4)

Hb: hemoglobin, IQR: interquartile range, BMI: body mass index, CRP: c-reactive protein

30
Table 2: Clinical features between patients with PSP (n=956) and SSP (n=817).
Variables
Mode of onset
first/recurrence/
unknown
Home oxygen therapy+/Comorbidities except for
pulmonary disease+/-/
unknown
Details of comorbidities
except for pulmonary disease

PSP (n=956)

SSP (n=817)

p-value
0.5220540 (56.5)/413(43.2)/
3 (0.3)483 (59.1)/332(40.6)/
2 (0.2)<0.00010 (0)/956 (100)91 (11.1)/726 (88.9)<0.0001112 (11.7)/841 (88)/
3 (0.3)542 (66.3)/274 (33.5)/
1 (0.1)

Impaired liver function（Child-Turcotteclassification≧B）

3 (0.3)10 (1.2)

0.0463

Hemodialysis
Ischemic heart disease
Malignancy（treated within
5 years）

2 (0.2)7 (0.7)10 (1)

7 (0.9)72 (8.8)111 (13.6)

0.0897<0.0001<0.0001

Cerebrovascular disease
Diabetes mellitus
Anemia（Hb≦8g/dl）

6 (0.6)
11 (1.2)
2 (0.2)5 (0.5)9 (0.9)34 (3.6)
89 (9.3)

86 (10.5)105 (12.9)
9 (1.1)36 (4.4)
68 (8.3)
244 (29.9)274 (33.5)<0.0001<0.0001
0.0289<0.0001<0.0001<0.0001<0.0001<0.0001

6 (0.6)/950 (99.4)

85 (10.4)/732 (89.6)

Autoimmune disorder
Arrhythmia
Hypertension
OthersAdministration of steroid on
admission+/Affected side
left/right/
bilateral
Age, median (IQR), years
GenderFemale/Male<0.0001502 (52.5)/440(46)/
14 (1.5)316 (38.7)/475(58.1)/
26 (3.2)

23 (12-94)

70 (13-96)<0.0001<0.0001133 (13.9)/823 (86.1)

210 (25.7)/607 (74.3)

31
Performance Status
0
1
2
3
4
unknown

825 (86.3)
108 (11.3)
16 (1.7)
2 (0.2)2 (0.2)3 (0.3)358 (43.8)
211 (25.8)
116 (14.2)
73 (8.9)39 (4.8)
20 (2.4)<0.0001<0.0001<0.0001<0.0001<0.0001<0.0001

BMI, median (IQR),

19 (11.9-32.6)

19.5 (10-33.9)

0.0178

Smoking index, median(IQR), pack x year
Serum CRP on admission,
median (IQR), g/dl
Serum albumin on admission,
median (IQR), g/dl
Degree of the collapsed lung
mild/moderate/severe/unknown

0 (0-150)

30.5 (0-175)<0.00010.1 (0-35.1)

0.44 (0-29.9)<0.0001

4.6 (2-7.3)

3.9 (1.6-5.2)<0.0001

Thoracography+/Chest tube drainage+/-

0.1140230 (24.1)/458 (47.9)/244 (25.5)/24 (2.5)

163 (20)/434 (53.1)/200 (24.5)/20 (2.4)<0.000112 (1.3)/944 (98.7)

65 (8)/752 (92)<0.0001688 (72)/268 (28)671 (82.1)/146 (17.9)

Pleurodesis+/-

27 (2.8)/929 (97.2)

139 (17)/678 (83)Administrative agents in thepleurodesis
OK-432
Minocycline
Autoblood
Talk
Glucose solution
Others12 (1.3)
5 (0.5)3 (0.3)0 (0)57 (6)
1 (0.1)51 (6.2)
41 (5)
39 (4.8)
14 (1.7)
50 (6.1)
17 (2.1)

Trans-airway procedure+/Surgical intervention+/-<0.0001<0.0001<0.0001<0.0001<0.0001
0.9200<0.0001<0.00010 (0)/956 (100)

23 (2.8)/794 (97.2)<0.0001756 (79.1)/200 (20.9)

429 (52.5)/388 (47.5)

32
Surgical approach
thoracoscopy/thoracotomy/
unknown
Treatment in intensive care
unit
+/-/
unknown
Total hospitalization, median(IQR), days
Outcome at discharge
home/transferred to otherhospital/death<0.0001
747 (98.8)/9 (1.2)/0 (0)400 (93.2)/24 (5.6)/
5 (1.2)0.000273 (7.6)/883 (92.4)/0 (0)102 (12.5)/712 (87.1)/
3 (0.4)8 (0-63)

13 (0-234)<0.0001<0.0001951 (99.5)/5 (0.5)/0 (0)690 (84.5)/85 (10.4)/
42 (5.1)

Hb: hemoglobin, IQR: interquartile range, BMI: body mass index, CRP: c-reactive protein
PSP: primary spontaneous pneumothorax, SSP: secondary spontaneous pneumothorax
Eleven cases with unknown subtype of pneumothorax were excluded.