A Randomized Controlled Trial to Test a Novel Negative Pressure Isolation Device During Aerosol Generating Procedures in the Operating Room
Phase: NA
Conditions: Aerosol Containment, Aerosol Generating Procedure
Sponsor: John Shin

A Novel Negative Pressure Isolation 
Device Reduces Aerosol Exposure: A 
Randomized Controlled Trial 
 
Study Protocol and Statistical Analysis Plan 
 
 
 
 
Trial Registration: ClinicalTrials.gov, NCT 04864236 
 
June 28, 2021 
 
 
 
Principal Investigator:  
John Shin, MD 
JShin@mednet.ucla.edu 
UCLA Department of Anesthesiology and Perioperative Medicine, 757 Westwood 
Plaza, Suite 3325, Los Angeles, CA 90095 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Inclusion criteria: 
Adult patients (age>18) undergoing elective surgery requiring general endotracheal anesthesia 
 
Exclusion criteria: 
Patients with BMI > 40 kg/m2, or 
Patients predicted to be difficult mask ventilation or intubation (as determined by 
anesthesiologist), or 
Patients refusing to consent for any reason (ie. claustrophobia or inability to cooperate). 
 
Preoperative: 
Patients will be screened and identified by the study team and allocated to each group via simple 
randomization (1:1), which will occur as soon as the OR schedule is available for viewing. 
 
Patients will be randomized to either device or no device. The study investigator will obtain 
consent the day of surgery. Also at the time of randomization, the anesthesia providers involved 
will be informed and asked to review the study protocol. Only the study investigators will be 
involved in the use of the device during patient care. 
 
On the day of surgery, the primary anesthesia provider will be provided with the unassembled 
device (if assigned to the device group) and be asked to assemble it. This process will be 
observed and timed by a study coordinator.  
 
 
Intubation: 
For device group: one of the study investigators will place the device around the patient’s head. 
At this time, one particle counter will be positioned on an IV pole next to the study investigator 
at the level of his/her nose. A second particle counter will be positioned next to the patient’s head 
in order to take measurements from inside of the device. The study team will obtain baseline 
measurements from both inside and outside the device simultaneously. At the start of 
preoxygenation (routine part of anesthesia), the study team will begin nebulizing 5ml of saline 
using a standard nebulizer at 5 liters per minute of oxygen flow. A study team member will be 
holding the nebulizer close to the patient’s nose and mouth. This will simulate airborne 
contamination that is generated by the patient. During this process, the patient will be instructed 
to breathe normally for 1 minute, then breathe deeply for 1 minute, and then breathe normally 
again for 1 minute. During intubation (routine part of anesthesia), the nebulizer will be placed 
next to the patient’s head and it will be kept on until after the patient has been intubated. 
Concurrent with the start of preoxygenation, the particle counter will start measuring particle 
counts. 1 minute after the endotracheal tube or laryngeal mask airway is secured, the anesthesia 
provider will be instructed to remove the device. A study coordinator will record particle counts 
continuously until 2 minutes after the device is removed from around the patient’s head.  
 
For no device group: exactly the same except no device will be placed around patient’s head.  
 
Digital recordings of the particle counts and distribution of particle sizes will be recorded during 
the conduct of the study in the operating room. These recordings will not be stored with any 
personally identifiable information. These recordings will be stored on a secure laptop 

(university-owned and encrypted) that is accessible only to the study investigators. If the 
participant decides to withdraw from the study, the study investigators will destroy the 
recordings immediately. 
 
Statistical Methods: 
Primary outcome: particle count measurements during intubation 
 
Statistical analysis plan: 
Particle counts will be compared between groups (device vs no device) using an independent 
samples t-test (or Wilcoxon Rank Sum Test if distributional assumptions are violated). 
 
Power/sample size: 
1)      From a statistical perspective, a sample size of 10 per group allows us to detect an effect 
size as small as 1.35  between  groups  (using  a  t-test,  >80%  power,  two  sided  alpha  0.05).  
A similar study (17) exploring the effectiveness of several different containment devices on 
airborne particles in similar settings mentioned an effect size of 1.0 (20,000 particles vs 12,000, 
SD of 8,000). We hypothesize that our device will be more effective than any device tested in 
this previous study at reducing airborne contamination so this is a conservative estimate of what 
we expect to see with our device. 
2)      Ultimately, we envision a final sample size of 50 per group to better assess both efficacy of 
the primary outcome as well as increase reliability in our secondary outcomes. This sample size 
will allow us to detect effect sizes as low as 0.57 between groups (using a t-test, >80% power, 
two sided alpha 0.05) and gives us a measure of precision of a confidence interval for the mean 
on our primary outcome of within +/-2,273 particles assuming the box group is 12,000 with a SD 
of 8,000.(17) 
 
Secondary outcomes:  
time to intubation (defined as time from the first entry of laryngoscope into pt's oropharynx to 
the time of confirmed successful tracheal intubation),  
total number of intubation attempts,  
pre-op airway assessment (Mallampati score and thyromental distance),  
laryngoscopy grade view (Cormack-Lehane) obtained during intubation 
 
Analysis plan: 
Secondary outcomes will be compared between groups (where possible) using an independent 
samples t-test (or chi-square test) as appropriate.