Inverse ratio ventilation(IRV) can produce mean airway pressure(Pmean)similar to external positive end expiratory pressure(Peep) by increasing inspiratory time. Moreover, the increase of Pmean was not accompanied by the further increase of peak airway pressure (Ppeak) and airway plateau pressure (Pplat), while the application of external peep accompanied with the increase of Pplat increased the risk of barotrauma . High level of Peep increased cardiac load and decreased cardiac output. A number of studies have found that the hemodynamic stability of patients can be achieved when IRV regulates the inspiratory / expiratory ratio in an appropriate range (I: E < 2:1). Therefore, the inverse ratio is considered to be superior to Peep in terms of gas exchange and respiratory mechanics.
The purpose of this study is to investigate the clinical application value of inverse ratio ventilation in obese patients during induction of general anesthesia by studying the effect of inverse ratio ventilation on the safe apnea time.