High-flow nasal oxygenation or standard oxygenation for gastrointestinal endoscopy with sedation in patients at risk of hypoxaemia: a multicentre randomised controlled trial (ODEPHI trial).

BACKGROUND: We aimed to determine whether high-flow nasal oxygen could reduce the incidence of decreased peripheral oxygen saturation (SpO2) compared with standard oxygen in patients at risk of hypoxaemia undergoing gastrointestinal endoscopy under deep sedation. METHODS: This was a multicentre, randomised controlled trial with blinded assessment of the primary outcome evaluating high-flow nasal oxygen (gas flow 70 L min-1, inspired oxygen fraction 0.50) or standard oxygen delivered via nasal cannula or face mask (6 L min-1) or nasopharyngeal tube (5 L min-1) in patients at risk of hypoxaemia (i.e. >60 yr old, or with underlying cardiac or respiratory disease, or with ASA physical status >1, or with obesity or sleep apnoea syndrome) undergoing gastrointestinal endoscopy. The primary endpoint was the incidence of SpO2 ≤92%. Secondary outcomes included prolonged or severe desaturations, need for manoeuvres to maintain free upper airways, and other adverse events. RESULTS: In 379 patients, a decrease in SpO2 ≤92% occurred in 9.4% (18/191) for the high-flow nasal oxygen group, and 33.5% (63/188) for the standard oxygen groups (adjusted absolute risk difference, -23.4% [95% confidence interval (CI), -28.9 to -16.7]; P<0.001). Prolonged desaturation (>1 min) and manoeuvres to maintain free upper airways were less frequent in the high-flow nasal oxygen group than in the standard oxygen group (7.3% vs 14.9%, P=.02, and 11.1% vs 32.4%, P<0.001). CONCLUSIONS: In patients at risk of hypoxaemia undergoing gastrointestinal endoscopy under deep sedation, use of high-flow nasal oxygen significantly reduced the incidence of peripheral oxygen desaturation. CLINICAL TRIAL REGISTRATION: NCT03829293.

High-flow nasal oxygenation versus standard oxygenation for gastrointestinal endoscopy with sedation. The prospective multicentre randomised controlled ODEPHI study protocol.

INTRODUCTION: Hypoxaemia is a major complication during gastrointestinal endoscopy (GIE) procedures (upper/lower) when performed under deep sedation in the procedure room. Standard oxygen therapy (SOT) is used to prevent hypoxaemia. Data suggest that risk factors for hypoxaemia under deep sedation during GIE are obstructive sleep apnoea syndrome, a body mass index above 30 kg/m², high blood pressure, diabetes, heart disease, age over 60 years old, high American Society of Anesthesiologists physical status class and the association of upper and lower GIE. High-flow nasal oxygenation (HFNO) may potentially improve oxygenation during GIE under deep sedation. We hypothesised that HFNO could decrease the incidence of hypoxaemia in comparison with SOT. METHODS AND ANALYSIS: The ODEPHI (High-flow nasal oxygenation versus standard oxygenation for gastrointestinal endoscopy with sedation. The prospective multicentre randomised controlled) study is a multicentre randomised controlled trial comparing HFNO to SOT during GIE (upper and/or lower) under deep sedation administered by anaesthesiologists in the procedure room. Three hundred and eighty patients will be randomised with a 1:1 ratio in two parallel groups.The primary outcome is the occurrence of hypoxaemia, defined by a pulse oximetry measurement of peripheral capillary oxygen saturation (SpO2) below or equal to 92% during the GIE procedure. Secondary outcomes include prolonged hypoxaemia, severe hypoxaemia, need for manoeuvres to maintain upper airway patency and other adverse events. ETHICS AND DISSEMINATION: This study has been approved by the ethics committee (CPP Sud Est Paris V, France), and patients are included after informed consent. The results will be submitted for publication in peer-reviewed journals. As provided for by French law, patients participating in the study are informed that they have the possibility to ask the investigators, once the study is completed, to be informed of the overall results of the study. Thus, a summary of the results will be sent by post to the participants on request. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT03829293).

Stabilization of cyclohexanone monooxygenase by a computationally designed disulfide bond spanning only one residue.

Enzyme stability is an important parameter in biocatalytic applications, and there is a strong need for efficient methods to generate robust enzymes. We investigated whether stabilizing disulfide bonds can be computationally designed based on a model structure. In our approach, unlike in previous disulfide engineering studies, short bonds spanning only a few residues were included. We used cyclohexanone monooxygenase (CHMO), a Baeyer-Villiger monooxygenase (BVMO) from Acinetobacter sp. NCIMB9871 as the target enzyme. This enzyme has been the prototype BVMO for many biocatalytic studies even though it is notoriously labile. After creating a small library of mutant enzymes with introduced cysteine pairs and subsequent screening for improved thermostability, three stabilizing disulfide bonds were identified. The introduced disulfide bonds are all within 12 Å of each other, suggesting this particular region is critical for unfolding. This study shows that stabilizing disulfide bonds do not have to span many residues, as the most stabilizing disulfide bond, L323C-A325C, spans only one residue while it stabilizes the enzyme, as shown by a 6 °C increase in its apparent melting temperature.