A comparison of controlled ventilation with a noninvasive ventilator versus traditional mask ventilation

After induction, but before intubation, many general anesthesia patients are manually bag-mask ventilated. The objective of this study was to determine the efficacy of bag-mask ventilation (MkV) of an anesthetized patient versus mask ventilation using a noninvasive ventilator (NIV). We hypothesized that feedback-controlled, mask ventilation via NIV is more efficacious and safer. This critical short period of time in the operating room was chosen to compare MkV versus NIV. 30 ASA I-III patients, aged 18-74, presenting for elective surgery under general anesthesia were enrolled in the study. Patients were ventilated first with MkV and then with NIV. One minute of ventilation data was collected for each method. Respiratory inductance plethysmography (RIP) bands around the chest and abdomen were used to measure tidal volumes and breath rates for each method of ventilation. The NIV was set to deliver 10 breaths per minute with 12 cmH₂O of pressure support. A non-inferiority test was used to compare MkV and NIV. MkV breaths had an average of 13 breaths and tidal volume of 364 mL (SD 145 mL). NIV resulted in an average of 10 breaths and tidal volume of 552 mL, i.e., 188 mL more than MkV (lower bound of the 95% confidence interval equal to 120 mL). The hypothesis of non-inferiority at the - 100 mL level and the superiority hypothesis at the + 100 mL level was accepted. NIV also resulted in much more consistent ventilation rates (zero variation since it is controlled by the ventilator) when compared to manual ventilation while maintaining safe airway pressures (8 cmH₂O EPAP and 20 cmH₂O IPAP). Feedback controlled mask ventilation via a NIV is a viable alternative to MkV. It can deliver more optimal tidal volumes with the operator utilizing only one hand. The airway pressures are fixed at safe limits during a period where the goal is to reach a maximal level of oxygenation prior to intubation. Over-ventilation or over-pressurization of the airway is not a concern with NIV since the pressures are maintained well within safe thresholds to avoid injury.