High Flow Nasal Cannula in Patients Undergoing Colonoscopy

During colonoscopy, the insertion of the fiberscope and colon distension required to perform the examination may induce modifications to respiratory mechanics, respiratory effort and breathing pattern.High-flow nasal cannula (HFNC) therapy is a mixed air-oxygen supply system able to deliver heated humidified gas up to 60 L/min of flow rate, with an inspiratory oxygen fraction (FiO2) ranging from 21% to 100%. Increasing evidence supports the use of HFNC in several clinical conditions and settings. When compared to standard therapy (ST), HFNC results in enhanced gas exchange and improved comfort.No studies have yet assessed the benefits of HFNC versus ST during and after colonoscopy. The investigators designed this unblinded randomized controlled trial to assess whether HFNC, compared to ST, improves oxygenation at the end of the procedure (primary endpoint). Additional endpoints were: 1) the lowest peripheral saturation of oxygen (SpO2) and the number of oxygen desaturations; 2) the changes of end-expiratory lung impedance and tidal impedance assessed by Electrical Impedance Tomography (EIT); 3) the effects on diaphragm function assessed by ultrasound (DUS).

Inclusion Criteria:outpatients with the indication to diagnostic colonoscopyExclusion Criteria:life-threatening cardiac aritmia or acute miocardical infarction within 6 weeksneed for invasive or non invasive ventilationpresence of pneumothorax or pulmonary enphisema or bullaerecent (within 1 week) thoracic surgerypresence of chest burnspresence of tracheostomypregnancynasal or nasopharyngeal diseasesdementialack of consent or its withdrawal