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Abstract
BackgroundObesity is a risk factor for airway-related incidents during anaesthesia. High-flow nasal oxygen has been advocated to improve safety in high-risk groups, but its effectiveness in the obese population is uncertain. This study compared the effect of high-flow nasal oxygen and low-flow facemask oxygen delivery on duration of apnoea in morbidly obese patients. MethodsMorbidly obese patients undergoing bariatric surgery were randomly allocated to receive either high-flow nasal (70 L min−1) or facemask (15 L min−1) oxygen. After induction of anaesthesia, the patients were apnoeic for 18 min or until peripheral oxygen saturation decreased to 92%. ResultsEighty patients were studied (41 High-Flow Nasal Oxygen, 39 Facemask). The median apnoea time was 18 min in both the High-Flow Nasal Oxygen (IQR 18–18 min) and the Facemask (inter-quartile range [IQR], 4.1–18 min) groups. Five patients in the High-Flow Nasal Oxygen group and 14 patients in the Facemask group desaturated to 92% within 18 min. The risk of desaturation was significantly lower in the High-Flow Nasal Oxygen group (hazard ratio=0.27; 95% confidence interval [CI], 0.11–0.65; P=0.007). ConclusionsIn experienced hands, apnoeic oxygenation is possible in morbidly obese patients, and oxygen desaturation did not occur for 18 min in the majority of patients, whether oxygen delivery was high-flow nasal or low-flow facemask. High-flow nasal oxygen may reduce desaturation risk compared with facemask oxygen. Desaturation risk is a more clinically relevant outcome than duration of apnoea. Individual physiological factors are likely to be the primary determinant of risk rather than method of oxygen delivery. Clinical trial registrationNCT03428256.
Highlights
Obesity is a risk factor for airway-related incidents during anaesthesia
In experienced hands, apnoeic oxygenation is possible in morbidly obese patients, and oxygen desaturation did not occur for 18 min in the majority of patients, whether oxygen delivery was high-flow nasal or low-flow facemask
Ten participants in each group were using continuous positive airway pressure (CPAP) and baseline characteristics were similar in both groups (Table 1)
Summary
This study was registered with ClinicalTrials.gov (NCT03428256), approved by the Bloomsbury Research and Ethics Committee (17/LO/0742) and was conducted in a tertiary centre between October 2018 and September 2019. Participants were positioned at 45 mid-thoracic incline.[6] In addition to standard monitoring,[11] bispectral index (BISTM; Medtronic Limited, Boulder, CO, USA) and invasive arterial blood pressure were monitored throughout the study period In both groups, preoxygenation was provided for 3 min. Arterial blood gas samples were taken at baseline (before preoxygenation), at the end of preoxygenation, at the onset of apnoea (TA), and at 2, 4, 6, 9, 12, and 18 min (TAþ2, 4, ..., 18) min thereafter if arterial oxygen saturation (SaO2) remained >92%; or when SaO2 reached 92% if this occurred before TAþ18 These samples were immediately refrigerated and processed sequentially at the end of the study (GEM Premier 4000; IL GmbH, Berlin, Germany). Data and documentation would be securely stored for 10 yr after the completion of the study
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