Trial Outcomes & Findings for Pre-oxygenation With Real Time End-tidal Oxygen Measurements Versus Single Breath Measurements (NCT NCT03840486)

Results Overview

Real-time end-tidal oxygen measurements as measured with a nasal cannula (NC) and single-breath (SB) end-tidal oxygen measurements across increasing oxygen concentrations and flow rates for the non-invasive ventilation (NIV) and non-rebreather mask (NRBM) study arms.

Recruitment status

COMPLETED

Study phase

PHASE4

Target enrollment

105 participants

Primary outcome timeframe

After each 3 minute treatment level

Results posted on

2025-06-13

Participant Flow

Participants were enrolled at Grady Memorial Hospital and Emory University Hospital Midtown in Atlanta, Georgia, USA. Participant enrollment began September 24, 2019 and the final study assessment occurred on October 20, 2023.

Participant milestones

Participant milestones
Measure	NIV With Delivery Sequence of NIV at 40% FiO2, NIV at 70% FiO2, and NIV at 100% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 40% fraction of inspired oxygen (FiO2), followed by NIV at 70% FiO2 , and lastly NIV at 100% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement. Non-invasive ventilator mask (NIV): The NIV is a non-invasive face (nasal) mask for oxygen delivery. Nasal cannula EtO2 sensor: The nasal cannula EtO2 sensor was placed on the participant's face under the mask to detect the EtO2 levels. Oxygen (NIV): Oxygen was delivered via the NIV mask. Participants received oxygen at 40% FiO2, 70% FiO2 or 100% FiO2 for 3 minutes each.	NIV With Delivery Sequence of NIV at 70% FiO2, 40% FiO2, and 100% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 70% fraction of inspired oxygen (FiO2), followed by NIV at 40% FiO2, and lastly NIV at 100% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 100% FiO2, NIV at 70% FiO2, and NIV at 40% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 100% fraction of inspired oxygen (FiO2), followed by NIV at 70% FiO2, and lastly NIV at 40% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 40% FiO2, NIV at 100% FiO2, and NIV at 70% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 40% fraction of inspired oxygen (FiO2), followed by NIV at 100% FiO2, and lastly NIV at 70% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 70% FiO2, NIV at 100% FiO2, and NIV at 40% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 70% fraction of inspired oxygen (FiO2), followed by NIV at 100% FiO2, and lastly NIV at 40% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 100% FiO2, NIV at 40% FiO2, and NIV at 70% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 100% fraction of inspired oxygen (FiO2), followed by NIV at 40% FiO2, and lastly NIV at 70% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 15 LPM, 35 LPM, and 55 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 15 liters per minute (LPM) for 3 minutes, at 35 LPM for 3 minutes, or at 55 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement. Non-rebreather mask (NRBM): The non-rebreather mask (NRBM) was used to assist in the delivery of oxygen. Nasal cannula EtO2 sensor: The nasal cannula EtO2 sensor was placed on the participant's face under the mask to detect the EtO2 levels.	NRBM With Delivery Sequence of Oxygen at 15 LPM, 55 LPM, and 35 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 15 liters per minute (LPM) for 3 minutes, at 55 LPM for 3 minutes, or at 35 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 35 LPM, 55 LPM, and 15 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 35 liters per minute (LPM) for 3 minutes, at 55 LPM for 3 minutes, or at 15 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 35 LPM, 15 LPM, and 55 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 35 liters per minute (LPM) for 3 minutes, at 15 LPM for 3 minutes, or at 55 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 55 LPM, 35 LPM, and 15 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 55 liters per minute (LPM) for 3 minutes, at 35 LPM for 3 minutes, or at 15 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 55 LPM, 15 LPM, and 35 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 55 liters per minute (LPM) for 3 minutes, at 15 LPM for 3 minutes, or at 35 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.
Overall Study STARTED	7	11	10	9	8	8	8	9	8	9	9	9
Overall Study Completed Sequence 1	7	10	10	9	8	8	8	9	8	9	9	9
Overall Study Completed Sequence 2	7	10	10	9	8	8	8	9	8	9	9	9
Overall Study COMPLETED	7	10	10	9	8	8	8	9	8	9	9	9
Overall Study NOT COMPLETED	0	1	0	0	0	0	0	0	0	0	0	0

Reasons for withdrawal

Reasons for withdrawal
Measure	NIV With Delivery Sequence of NIV at 40% FiO2, NIV at 70% FiO2, and NIV at 100% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 40% fraction of inspired oxygen (FiO2), followed by NIV at 70% FiO2 , and lastly NIV at 100% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement. Non-invasive ventilator mask (NIV): The NIV is a non-invasive face (nasal) mask for oxygen delivery. Nasal cannula EtO2 sensor: The nasal cannula EtO2 sensor was placed on the participant's face under the mask to detect the EtO2 levels. Oxygen (NIV): Oxygen was delivered via the NIV mask. Participants received oxygen at 40% FiO2, 70% FiO2 or 100% FiO2 for 3 minutes each.	NIV With Delivery Sequence of NIV at 70% FiO2, 40% FiO2, and 100% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 70% fraction of inspired oxygen (FiO2), followed by NIV at 40% FiO2, and lastly NIV at 100% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 100% FiO2, NIV at 70% FiO2, and NIV at 40% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 100% fraction of inspired oxygen (FiO2), followed by NIV at 70% FiO2, and lastly NIV at 40% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 40% FiO2, NIV at 100% FiO2, and NIV at 70% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 40% fraction of inspired oxygen (FiO2), followed by NIV at 100% FiO2, and lastly NIV at 70% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 70% FiO2, NIV at 100% FiO2, and NIV at 40% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 70% fraction of inspired oxygen (FiO2), followed by NIV at 100% FiO2, and lastly NIV at 40% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NIV With Delivery Sequence of NIV at 100% FiO2, NIV at 40% FiO2, and NIV at 70% FiO2 Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations. Participants in this study arm received NIV at 100% fraction of inspired oxygen (FiO2), followed by NIV at 40% FiO2, and lastly NIV at 70% FiO2. Each trial was 3 minutes and a maximal reading at the end of this trial was recorded. Study participants rested until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, were allowed to rise to the maximal reading of the previous step, then did a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 15 LPM, 35 LPM, and 55 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 15 liters per minute (LPM) for 3 minutes, at 35 LPM for 3 minutes, or at 55 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement. Non-rebreather mask (NRBM): The non-rebreather mask (NRBM) was used to assist in the delivery of oxygen. Nasal cannula EtO2 sensor: The nasal cannula EtO2 sensor was placed on the participant's face under the mask to detect the EtO2 levels.	NRBM With Delivery Sequence of Oxygen at 15 LPM, 55 LPM, and 35 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 15 liters per minute (LPM) for 3 minutes, at 55 LPM for 3 minutes, or at 35 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 35 LPM, 55 LPM, and 15 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 35 liters per minute (LPM) for 3 minutes, at 55 LPM for 3 minutes, or at 15 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 35 LPM, 15 LPM, and 55 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 35 liters per minute (LPM) for 3 minutes, at 15 LPM for 3 minutes, or at 55 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 55 LPM, 35 LPM, and 15 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 55 liters per minute (LPM) for 3 minutes, at 35 LPM for 3 minutes, or at 15 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	NRBM With Delivery Sequence of Oxygen at 55 LPM, 15 LPM, and 35 LPM Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence in one of 6 possibilities. Participants in this study arm received oxygen at 55 liters per minute (LPM) for 3 minutes, at 15 LPM for 3 minutes, or at 35 LPM for 3 minutes. All trials were 3 minutes in duration and the maximal reading at the end of each trial was recorded, then the study participants were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate (55 LPM), allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.
Overall Study Withdrawal by Subject	0	1	0	0	0	0	0	0	0	0	0	0

Baseline Characteristics

Race and Ethnicity were not collected from any participant.

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Non-invasive Ventilator Mask (NIV) n=52 Participants Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-invasive ventilator mask (NIV) overlying the sensor. Participants were randomized to the order of their treatment sequence to one of six combinations of NIV at 40% fraction of inspired oxygen (FiO2) for 3 minutes, NIV at 70% FiO2 for 3 minutes, NIV at 100% FiO2 for 3 minutes. The maximal reading at the end of each trial was recorded. The study participants were allowed to rest until their EtO2 returned to their baseline, then they were placed back on NIV at 100% FiO2, allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	Non-rebreather Mask (NRBM) n=52 Participants Prior to the start of the study procedure, a nasal cannula end-tidal oxygen (EtO2) sensor was placed on the participant's face with the non-rebreather mask (NRBM) overlying the sensor. The participants were randomized to the order of their treatment sequence to one of six combinations of oxygen at 15 liters per minute (LPM) for 3 minutes, at 35 LPM for 3 minutes, or at flush rate (55 LPM) for 3 minutes. The maximal reading at the end of each trial was recorded, then the study subjects were allowed to rest until their EtO2 returned to their baseline. They were then placed back on NRBM at flush rate, allowed to rise to the maximal reading of the previous step, then do a single breath exhaled EtO2 measurement.	Total n=104 Participants Total of all reporting groups
Age, Continuous	28 years n=52 Participants	27 years n=52 Participants	28 years n=104 Participants
Sex: Female, Male Female	30 Participants n=52 Participants	37 Participants n=52 Participants	67 Participants n=104 Participants
Sex: Female, Male Male	22 Participants n=52 Participants	15 Participants n=52 Participants	37 Participants n=104 Participants
Race and Ethnicity Not Collected	—	—	0 Participants Race and Ethnicity were not collected from any participant.
Region of Enrollment United States	52 participants n=52 Participants	52 participants n=52 Participants	104 participants n=104 Participants
Body Mass Index (BMI)	24.7 kg/m^2 n=52 Participants	24.9 kg/m^2 n=52 Participants	24.8 kg/m^2 n=104 Participants
Baseline Single Breath End Tidal Oxygen (EtO2%)	16.8 percent of oxygenation n=52 Participants	16.8 percent of oxygenation n=52 Participants	16.8 percent of oxygenation n=104 Participants

PRIMARY outcome

Timeframe: After each 3 minute treatment level

Population: This analysis includes participants who completed all three intervention levels.

Real-time end-tidal oxygen measurements as measured with a nasal cannula (NC) and single-breath (SB) end-tidal oxygen measurements across increasing oxygen concentrations and flow rates for the non-invasive ventilation (NIV) and non-rebreather mask (NRBM) study arms.

Outcome measures

Outcome measures
Measure	NIV at 40% FiO2 n=52 Participants Participants receiving non-invasive ventilator mask (NIV) at 40% fraction of inspired oxygen (FiO2) for 3 minutes.	NIV at 70% FiO2 n=52 Participants Participants receiving non-invasive ventilator mask (NIV) at 70% fraction of inspired oxygen (FiO2) for 3 minutes.	NIV at 100% FiO2 n=52 Participants Participants receiving non-invasive ventilator mask (NIV) at 100% fraction of inspired oxygen (FiO2) for 3 minutes.	NRBM at 15 LPM n=52 Participants Participants receiving non-rebreather Mask (NRBM) at 15 liters per minute (LPM) for 3 minutes.	NRBM at 35 LPM n=52 Participants Participants receiving non-rebreather Mask (NRBM) at 35 liters per minute (LPM) for 3 minutes.	NRBM at 55 LPM n=52 Participants Participants receiving non-rebreather Mask (NRBM) at 55 liters per minute (LPM) for 3 minutes.
Real Time and Single Breath End-tidal (EtO2) Measurements Nasal cannula end-tidal oxygen measurement	34 percentage of end-tidal oxygen Interval 33.0 to 35.8	63 percentage of end-tidal oxygen Interval 61.0 to 64.0	92 percentage of end-tidal oxygen Interval 91.0 to 93.0	58.5 percentage of end-tidal oxygen Interval 48.3 to 66.0	79 percentage of end-tidal oxygen Interval 72.3 to 84.8	87.5 percentage of end-tidal oxygen Interval 83.0 to 91.0
Real Time and Single Breath End-tidal (EtO2) Measurements Single-breath end-tidal oxygen measurement	33.1 percentage of end-tidal oxygen Interval 29.9 to 34.6	58.4 percentage of end-tidal oxygen Interval 52.2 to 61.5	84.6 percentage of end-tidal oxygen Interval 73.7 to 88.1	44.9 percentage of end-tidal oxygen Interval 38.7 to 50.1	60.8 percentage of end-tidal oxygen Interval 51.4 to 69.4	70.5 percentage of end-tidal oxygen Interval 60.3 to 82.1

SECONDARY outcome

Timeframe: Up to 3 minutes

Population: This analysis includes participants who completed all three intervention levels.

Time required to reach 3-minute nasal cannula end-tidal oxygen (EtO2) reading for the single-breath (SB) EtO2 measurement at TmaxNC for the non-invasive ventilation (NIV) and non-rebreather mask (NRBM) arms.