Body position and the effectiveness of mask ventilation in anaesthetised paralysed obese patients

Airway management is more challenging in the obese. Compared with the supine position, the sitting position can decrease the collapsibility of the upper airway and improve respiratory mechanics.The aim of this study was to evaluate the 25° semisitting position on the effectiveness of mask ventilation in anaesthetised paralysed obese patients.A randomised, cross-over study.Medical centre managed by a university tertiary hospital.Thirty-eight obese adults scheduled for general anaesthesia.After anaesthesia and paralysis, two-handed mask ventilation was performed in the supine and 25° semi-sitting positions with a cross-over, in a randomised order. During mask ventilation, mechanical ventilation was delivered with a pressure-controlled mode with a peak inspiratory pressure of 15 cmH2O, a respiratory rate of 15 bpm, and no positive end-expiratory pressure. Ventilatory outcomes were based upon lean body weight.Exhaled tidal volume (ml kg-1), respiratory minute volume (ml kg-1 min-1), and the occurrence of inadequate ventilation, defined as an exhaled tidal volume less than 4 ml kg-1, or absence of end-tidal CO2 recording.Exhaled tidal volume (mean ± SD) in the 25° semi-sitting position was higher than in the supine position, 9.3 ± 2.7 vs. 7.6 ± 2.4 ml kg-1; P less than 0.001. Respiratory minute volume was improved in the 25° semisitting position compared with that in the supine position, 139.6 ± 40.7 vs. 113.4 ± 35.7 ml kg-1 min-1; P less than 0.001.The 25° semisitting position improved mask ventilation compared with the supine position in anaesthetised paralysed obese patients.ClinicalTrials.gov (NCT03996161).