Effect of Head Rotation on Efficiency of Face Mask Ventilation in Anesthetized Apneic Adults

When apnea is achieved after induction, face mask ventilation is started in either a neutral head position or a head position axially rotated 45 degrees to the right. Mask ventilation will be carried out for 1 minute (Step 1) with pressure control ventilation of an anesthesia machine at peak inspiratory pressure 15 cmH2O, 10 breaths per minute, inspiration time to expiration time ratio 1:2 and no positive end-expiratory pressure. Then, mask ventilation will continue but head position will be crossed over (Step 2) and Step 1 will be repeated (Step 3). Expiratory tidal volume (VTE) will be measured by using respiratory inductive plethysmograph.

Inclusion criteria

• Patients with body mass index in the range of 18.5 to 35.0 kg/m2, who meet American society of anesthesiologists physical status classification I to III and require general anesthesia with tracheal intubation.

Exclusion criteria

• Patients with limited head rotation/extension, gastro-esophageal reflux or a full stomach, known sleep apnea in continuous positive airway pressure therapy and any anticipated difficult airway likely requiring awake intubation.