The Effect of Nasal Continuous Positive Airway Pressure on Oxygenation in High-risk Patients Having Gastrointestinal Endoscopy Under Deep Sedation
Phase: NA
Conditions: Continuous Positive Airway Pressure, Endoscopy, Oxygenation, Obesity
Sponsor: Universitätsklinikum Hamburg-Eppendorf

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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Study protocol 
 
 
The effect of nasal continuous positive airway pressure on oxygenation in 
high-risk patients having gastrointestinal endoscopy under deep sedation  
 
 
Responsible:  
Dr. med. Malte Issleib1  
Dr. med. Karlo Hünerbein1 
Prof. Dr. med Thomas Rösch2 
 
1Klinik und Poliklinik für Anästhesiologie, Zentrum für Anästhesie und 
Intensivmedizin, Universitätsklinikum Hamburg-Eppendorf  
2Klinik und Poliklinik für interdisziplinäre Endoskopie, Zentrum für Radiologie und 
Endoskopie, Universitätsklinikum Hamburg-Eppendorf  
 

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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1. 
Backround 
Deep sedation during gastrointestinal endoscopy in patients with cardiopulmonary risk 
factors such as respective co-morbidities or also morbid obesity is challenging. Those 
high-risk patients are at risk of upper airway obstruction and hypoxemia. Nasal 
continuous positive airway pressure may help to decrease the incidence of peri-
interventional hypoxemia. However, data on nasal continuous positive airway pressure 
in high-risk patients having gastrointestinal endoscopy are scarce; only one 
randomized trial on gastroscopy in obese patients is available (Kang et al. J Anesth 
2021). In a very high-risk group, namely patients assessed for heart or lung 
transplantation in our hospital, the risk was especially high (unpublished data)  
 
2. 
Objective 
We aim to investigate the effect of nasal continuous positive airway pressure – 
compared to nasal oxygen insufflation – on the incidence of hypoxemia in high-risk 
patients having gastrointestinal endoscopy in deep sedation. 
 
3. 
Hypothesis 
We hypothesize that nasal continuous positive airway pressure – compared to nasal 
oxygen insufflation – reduces the incidence of hypoxemia in high-risk patients having 
gastrointestinal endoscopy in deep sedation. 
 
4. 
Setting 
Single-centre prospective randomised trial in the Department of Interdisciplinary 
Endoscopy and the Department of Anesthesiology of a German university medical 
center.  
 

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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5. 
Patients  
Inclusion criteria 
 
• Adult and obese high-risk patients (ASA class ≥3 and/or BMI ≥30 kg/m², in 
accordance with the current WHO definition of obesity) scheduled for elective 
gastrointestinal endoscopy with deep sedation. 
 
Exclusion criteria 
• Age < 18 years 
• Pregnancy 
• Cognitive impairment, that makes consent to study impossible 
• Known but untreated heart disease (e.g. PFO, recent congestive heart failure), 
complicating comparability within groups 
 
Outcome 
Primary outcome:  
• The incidence of hypoxemia defined as a peripheral oxygen saturation of ≤90% 
registered with the monitoring system of our working station (Phillips IntelliVue 
and Massimo Rad-97) after inducing deep sedation while unter endoscopy 
intervention. 
Secondary outcomes:  
• Duration of intervention (absolute) 
• Duration of hypoxemia/Time until recovery (>90%) (absolute) 
• Hypoxemic events per intervention 
• Ratio of hypoxemia duration compared to procedure duration (relatively) 
• Incidence of need for airway intervention (mask ventilation, intubation, interruption) 
• Comparison between subgroups BMI 30+; 35+; 40+ kg/m² 

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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• Sedation score (Modified Observer Assessment of Alertness/Sedation) 
• Continuous measurement of endtidal CO2 via the mask 
 
6. Protocol 
Patients will be randomized to nasal continuous positive airway pressure or nasal 
oxygen insufflation.  
Patients randomized to nasal continuous positive airway pressure will receive a 
positive pressure between 3 and 10cm H2O depending on the type of endoscopy, and 
an oxygen flow rate of 6l/min. Patients randomized to nasal oxygen insufflation nasal 
oxygen will be started with a flow of 6L/min. 
Deep sedation will be performed under surveillance of an anaesthesia-team (physician 
and nurse) using a propofol bolus of 1 mg/kg adjusted body weight, followed by a 
continuous propofol infusion of 4mg/kg/h (adjusted to lean body weight) (MacDonald 
JJ, Moore J, Davey V, Pickering S, Dunne T. The weight debate. J Intensive Care Soc. 
2015 Aug;16(3):234-238. doi: 10.1177/1751143714565059), until a MOAA/S Score of 
1-2 is reached (Kowalski R, Mahon P, Boylan G, et al. Validity of the modified 
observer’s assessment of alertness/sedation scale (MOAA/S) during low dose propofol 
sedation: 3AP6-3. Eur J Anaesthesiol. 2007;24:26–27, DOI:10.1097/00003643-
200706001-00097). If necessary, additional boluses of 20mg Propofol will be 
administered until the desired sedation depth is achieved. SpO2 and heart rate will be 
monitored continuously. Blood pressure will be monitored using upper-arm cuff 
oscillometry (3-minute intervals). Additional data collected from the medical record will 
include baseline SpO2, post-interventional SpO2, procedure length, and length of stay 
in the post anesthetic care unit (PACU). 
 
7. Statistics  

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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Descriptive analysis will be performed to describe patient characteristics and clinical 
data. The primary and secondary outcomes will be analysed according to the intention-
to-treat principle. The primary outcome and dichotomous secondary outcomes of 
treatment arms will be compared by means of Chi-squared tests and odds ratios with 
95% confidence intervals. Secondary outcomes measured on interval scales will be 
compared by means of t-tests, Welch-tests or Mann-Whitney test as appropriate, 
depending on whether test assumptions (particularly normal distribution and variance 
homogeneity) are met. Data will be checked for normal distribution and variance 
homogeneity prior to these analyses. Secondary outcomes measured on ordinal 
scales will be compared by means of Mann-Whitney U-tests. Reporting will be 
consistent with CONSORT guidelines. Statistical analyses will be performed with 
standard statistical software such as SPSS (IBM Corp., Armonk, NY), SAS (SAS 
Institute Inc., Cary NC) or R (R Core Team, 2017). 
 
Sample size:  
The sample size calculation is based on the primary outcome of the incidence of 
hypoxemia defined as a peripheral oxygen saturation of ≤90% after inducing deep 
sedation while performing endoscopy. 
The incidence of the primary outcome was assumed to be 30% in nasal oxygen 
insufflation group and 10% in the nasal continuous positive airway pressure group. A 
total sample size of 158, i.e., 79 patients per group, is required to achieve 90% power 
in the detection of a difference of 20% between the group incidences at a significance 
level of 0.05 using a two-sided test of proportions. It is assumed that all patients stay 
within their treatment group within the observational period.  
The randomization and division in subgroup “nasal continuous positive airway 
pressure” and “nasal oxygen insufflation” will occur prior to study entry. The entire 

Studienprotokoll Version 3.0; NCT06168682 (clinicaltrials.gov registered); 01.10.2023 
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collective will be divided into 2 populations and the allocation sealed in envelopes. The 
envelope will only be opened directly before the study so that investigator bias can be 
minimized. 
 
8. Abbreviations 
ASA 
American Society of Anaesthesiology 
BMI 
Body Mass Index 
WHO 
World Health Organisation 
MOAA/S 
Modified 
Observer 
Assessment 
of 
Alertness/Sedation 
PBW  
Predicted Body Weight 
males (kg) = 50 + [0.91 ×(Height in cm − 
152.4)] 
females (kg) = 45.5 + [0.91 ×(Height in 
cm − 152.4)] 
IBW 
Ideal Body Weight 
Male (kg): 50,0 kg+2,3kg*(cm-60) 
Female (kg): 45,5 kg+2,3kg*(cm-60) 
ABW 
Adjusted Body Weight 
IBW+0,4*(actual body weight-IBW) 
LBW 
Lean Body Weight 
males 
(kg) = (9270 × 
TBW)/ 
[6680 + (216 × BMI)] 
females 
(kg) = 
(9270 × TBW)/ 
[8780 + (244 × BMI)]