Aerosol Particle Concentrations Among Different Oxygen Devices for Spontaneous Breathing Patients With Tracheostomy: a Randomized Cross-over Trial
Phase: NA
Conditions: Transmission, Patient-Professional
Sponsor: Jie Li

Aerosol particle concentrations among different oxygen devices for spontaneous breathing 
patients with tracheostomy: a randomized cross-over trial
Jie Li1, PhD, RRT, RRT-ACCS, RRT-NPS; James B Fink1, PhD, RRT; Ahmad A Elshafei1, MS, 
RRT, RRT-ACCS; Amnah Alolaiwat1, MS, RRT; Lauren J Harnois1, MS, RRT; David Vines1, 
PhD, RRT.
1 Department of Cardiopulmonary Sciences, Division of Respiratory Care, Rush University 
Medical Center, Chicago, IL.
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

Introduction
The transmission route of the SARS-CoV-2 virus remains controversial,1,2 and concerns 
persist of potentially increased virus transmission and aerosol dispersion when utilizing high-
flow devices and aerosol devices among COVID-19 patients.2-5 For spontaneous breathing 
patients with tracheostomy, whose lower airway more directly communicates to the room air, the 
aerosol particles generated by these patients would be directly dispersed into the room air, which 
might be an direct resource of virus transmission.6 Thus tracheostomy procedure is considered as 
a high-risk aerosol generating procedure and high-level personal protection equipment is 
recommended when the procedure is performed for COVID-19 patients. 7 However, the 
transmission risk of tracheostomy during spontaneous breathing has not been evaluated and the 
impact of appropriate humidification therapy is unknown. 
Heat-moisture exchange filter (HMEF) should be an ideal humidification modality for 
those patients, as it can provide heat and humidification for patients and more importantly, it can 
filter the exhaled gas from patients.6,8 However, this device should be used for long periods of 
time and could not be used for patients who had copious or thick secretions, due to the low 
efficiency of humidification. More importantly, it can be easily occluded by patients’ secretion, 
resulting in dyspnea. Large volume nebulization, also named as cool aerosol, is commonly used 
for spontaneous breathing patients with tracheostomy. However, it can be easily contaminated by 
patients’ secretions, resulting in generation of bio-aerosol that carries virus into the room air. 
Thus, nebulization should be avoided for COVID-19 patients.5 Lastly, high-flow high humidity 
device that provides heated and humidified gas has been shown to improve comfort and secretion 
management in tracheostomy patients,9,10 it has also been shown to have similar aerosol particle 
concentrations as conventional oxygen devices,11,12  which might be used for spontaneous 
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

breathing patients with tracheostomy. However, since it still keeps airway open, the aerosol 
particle concentrations generated by patients via tracheostomy stoma as well as the virus load in 
the room air is still unknown. Thus this study is aimed to investigate the aerosol particle 
concentrations among different oxygen and humidification devices for spontaneous breathing 
patients with tracheostomy, in order to reflect the transmission risk.
Furthermore, our previous study found that wearing a surgical mask over high-flow nasal 
cannula can significantly reduce aerosol particle concentrations for COVID-19 patients,13 thus 
we also aim to explore the effects of wearing a surgical mask or using a scavenger tent over the 
high-flow device for tracheostomy patients can reduce the aerosol particle concentrations. 
Methods
1. Study design: a randomized cross-over trial
1) Inclusion criteria: (1) adults; (2) tracheostomy; (3) able to spontaneous breathing 
without ventilator support.
2) Exclusion criteria: (1) confirmed diagnosis of COVID-19 within recent two weeks; 
(2) non-English speaking; (3) refuse to participate in the study; (4) palliative care; (5) 
receiving ECMO; (6) unable to connect with tracheostomy adapter, such as 
laryngectomy tube. 
3) Reason for excluding COVID-19 patients in this trial is: the transmission risk of using 
different devices especially large volume nebulizer is still unknown, to protect the 
study investigators and other clinicians who might enter into the room with patients’ 
airway open, we would not keep anyone inside the room with patient’s airway open. 
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

2. Comparisons: 1) high-flow high humidity device with tracheostomy adapter; 2) large-volume 
nebulizer (cool aerosol) with trach collar; 3) Venturi-adapter with trach collar; 4) large-
volume nebulizer (cool aerosol) with T-piece and a filter; 5) high-flow high humidity device 
with tracheostomy adapter and a scavenger or a surgical mask over the adapter.
3. Sample size: This study is a superiority study. From our previous clinical study, wearing a 
surgical mask significantly reduced aerosol particle concentrations,13 particularly in 
proximity, the use of HMEF would reduce the aerosol particle concentrations even more, 
thus we expect the treatment effect would be medium to large as 0.1.14 Using G-power 
software15 to calculate the sample size in repeated ANOVA measures, with confidence level 
(α) of 95%, power (1-ß) of 80%, the number of patients that need to be enrolled is 12.
4. Study process: after consent, respiratory therapist assesses patient to see if patient needs 
suctioning. If needed, suction patient. Place HMEF on patient for 10 mins in order to 
measure the baseline data. Then use different devices in a pre-determined random order 
(prepared in an opaque envelope) for 5 mins, followed by 10 mins HMEF for the baseline 
data (figure 1). Aerosol particle sizes (Model 3889, Kanomax, Andover, NJ) will be placed at 
1 and 3 feet from the patient airway measure aerosol particle concentrations. Patient’s 
comfort will be self-evaluated using an visual numerical scale (VNS) ranging between 1 
(very uncomfortable) and 5 (very comfortable) (Figure 2).16
5. Data collection: age, gender, ethnicity, diagnosis, tracheostomy placement duration, 
tracheostomy tube size, cuff inflation, secretion amount and color, aerosol particle 
concentrations and patient comfort at baseline and during the use of different humidification 
devices
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

6. Outcome: 1) aerosol particle concentrations at baseline and during the use of different 
humidification devices; 2) patient comfort with different devices
7. Statistical analysis: Kolmogorov-Smirnov will be used to test normality of distribution for 
considered variables. Continuous variables will be expressed as mean (standard deviation [SD]) or 
median (Inter-Quartile Range [IQR]), depending on the normality of distribution. Friedman test will 
be used to compare the aerosol particle concentrations among five devices. A p-value of < 0.05 was 
considered statistically significant for all tests. Data analysis was conducted with SPSS statistical 
software (SPSS 26.0; SPSS; Chicago, IL).
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

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ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

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ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

Figure 1. Study process (total duration: 90 mins for one patient)
Figure 2. Patient’s comfort visual numerical scale (VNS)
Consented 
HMEF for 10 mins 
Assess patient, suction if needed  
Device 1 for 5 mins 
HMEF for 10 mins 
Device 3 for 5 mins 
HMEF for 10 mins 
Device 4 for 5 mins 
Trial completed
HMEF for 10 mins 
Device 5 for 5 mins 
HMEF for 10 mins 
Device 2 for 5 mins 
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020

Scale 
Explanation 
1
Very uncomfortable
2
Uncomfortable 
3
Neutral 
4
Comfortable 
5
Very comfortable 
ORA: 20112506-IRB01   Date IRB Approved: 12/13/2020