Investigator-initiated, multicentre, open-label, two-arm, randomised controlled trial comparing intubating conditions in 25° head-up position and supine: the InSize25 study protocol

INTRODUCTION: Difficult airway management during tracheal intubation can lead to severe hypoxic sequelae. Routine intubation practice is to use a strict supine position, whereas a 25° head-up or reverse Trendelenburg position increases efficacy of preoxygenation, seems more comfortable for the anaesthetist and may also provide better intubation conditions in direct laryngoscopy. The 25° head-up position could be used for the whole population rather than only for obese patients, but there is no prospective randomised controlled trial with a robust design and large number of patients comparing strict supine against 25° intubation in operating room. The objective of the InSize25 study is to test the effect of these two patient positions on intubation conditions during laryngoscopy in scheduled surgery on non-obese patients. METHODS AND ANALYSIS: InSize25 is an investigator-initiated, multicentre, open-label, two-arm, randomised controlled trial. The InSize25 study will randomise 1000 adult patients scheduled for surgery under general anaesthesia requiring intubation with neuromuscular-blocking drugs, candidates for direct laryngoscopy. The primary outcome variable is the view obtained during the first laryngoscopy without any external manipulation assessed using percentage of glottic opening. Important secondary outcomes are: Cormack-Lehane classification, number of attempts at laryngoscopy and at tracheal intubation, use of ancillary equipment (eg, bougies, alternative laryngoscope blades, videolaryngoscope) and manoeuvres (eg, laryngeal manipulation), comfort score for the anaesthetist, episodes of postinduction hypotension or desaturation and mechanical complications of intubation. ETHICS AND DISSEMINATION: The trial received appropriate approval from the ‘CPP Sud-Est II’ ethical review board. Informed consent is required. If the 25° head-up position proves superior for tracheal intubation without more complications, it may become the routine-standard intubation position rather than only for use with obese patients. The final results will be published in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: Clinicaltrials.gov identifier (NCT03339141).