A prospective randomized study to evaluate the efficacy of pressure support ventilation with and without positive end expiratory pressure for preoxygenation in adult patients.

Abstract

A primary concern for anesthesiologists is the maintenance of oxygenation during general anesthesia. Extending the safe apnea time, which is the time from the onset of apnea until the oxygen saturation concentration reaches 90% or less, increases the margin of safety with tracheal intubation. Preoxygenation before anesthetic induction has been a widely accepted manoeuver to increase oxygen reserves and hence delay the onset of arterial desaturation during apnea. This study aimed to evaluate the efficacy of pressure support ventilation with/without positive end-expiratory pressure (PEEP) for preoxygenation in adult patients. A total of 132 patients, aged 20 to 50 years, scheduled for elective surgery under general anesthesia, requiring endotracheal intubation, were included and randomly divided into three groups (n = 44 per group): spontaneous ventilation (SV), pressure support ventilation without PEEP (PS), and pressure support ventilation with PEEP (PEEP) groups. In the SV group, the patients breathed spontaneously without any support using a face mask; in the PS group, the patients breathed spontaneously with the inspiratory pressure support of 12 cm H2O without PEEP; and in the PEEP group, the patients were subjected to preoxygenation (similar to the PS group) with PEEP at 6 cm H2O. Preoxygenation was terminated when the fraction of expired oxygen reached 90% and the duration was recorded. Time from 90 seconds after administration of rocuronium bromide until oxygen saturation fell to 93% was recorded and taken as safe apnea time. The time taken for preoxygenation (the expired oxygen fraction reaches 90) was significantly shorter in patients of PEEP and PS groups when compared to the SV group. The safe apnea time was significantly longer in patients of PEEP and PS groups compared with the SV group. Application of inspiratory pressure support of 12 cm H2O and PEEP of 6 cm H2O during preoxygenation significantly reduces the preoxygenation time and prolongs the safe apnea time compared with conventional preoxygenation.