Manual ventilation with and without a flow limiting device during induction of general anesthesia: a randomized...

Poor manual ventilation with a self-inflating resuscitator bag (SIRB) can result in excessive tidal volumes and elevated airway pressures, increasing the risk of gastric insufflation, aspiration and lung injury. This study compared peak airway pressures generated during intentionally forceful manual ventilation using a SIRB with, and without a flow-limiting device in patients undergoing non-emergent surgery.

In this randomized, two-group crossover superiority trial, 30 adult patients undergoing general anesthesia received manual SIRB ventilation with and without the Sotair® inline flow limiting device (FLD) in randomized order (FLD + SIRB followed by SIRB alone vs SIRB alone followed by FLD + SIRB). Following endotracheal intubation, the SIRB, FLD, flow and pressure sensor, and adjustable pressure-limiting valve were connected in series to the endotracheal tube. During each intervention period, five forceful breaths were delivered every 30 s for 3 min. For safety, a pressure-limiting valve was set at 35 cm H₂O. The primary outcome was the mean peak inspiratory pressure across the five forceful breaths.

The mean peak inspiratory pressure across five forceful breaths was 18.4 cm H₂O [95% CI, 17.2-19.6] with FLD + SIRB compared to 29.6 cm H₂O [95% CI, 28.4-30.8] with SIRB ventilation alone, with a mean difference of 11.2 cm H_2O [95% CI, 10.5-11.9], which was above the superiority margin of 7.5 cm H_2O (p < 0.001). Mean peak inspiratory flow (60.1 L/min [95% CI, 55.7-64.6] vs 101.7 L/min [95% CI, 97.2-106.1]) and tidal volume (96.7 mL [95% CI, 77.6-115.9] vs 789.2 mL [95% CI, 770.1-808.3]) were also significantly lower with the FLD + SIRB compared to SIRB alone (p < 0.001). No FLD related malfunction events were observed.

The novel flow-limiting device reduced excessive peak airway pressures, inspiratory flow, and tidal volumes during forceful SIRB ventilation in anesthetized, intubated adults undergoing elective surgery. However, reduced tidal volumes during forceful breaths may cause inadequate alveolar ventilation if not corrected over several breaths, particularly during CPR.