958 Different Gas Flow Rates and Effects on Tidal Volume and Mask Leak During Positive Pressure Ventilation

Abstract

Aim: Observing the effects of changing gas flow rates during positive pressure ventilation (PPV) on Peak Inflating Pressure (PIP), Positive End Expiratory Pressure (PEEP), expiratory tidal volume (V) and mask leak.Methods: Twenty neonatal staff members of The Royal Women's Hospital were asked to deliver PPV to a modified manikin. Experiment 1: PPV was delivered for four minutes continuously with a set PIP 30 cm HO and PEEP 5 cm HO. Each minute the gas flow rate was increased from 5 to 8, 10, and 15 L/min. Neither PIP nor PEEP was adjusted during PPV. The same initial settings were used in experiment 2. However, PIP and PEEP were readjusted after each gas flow rate change.Results: Results are given in median (IQR).Experiment 1: with gas flow rate increments of 5, 8, 10 and 15 L/min the Vdecreased significantly from 10.0 (8.5-11.4), 6.3 (3.9-7.4), 3.4 (0.7-5.4) to 0.8 (0-1.7) mL/kg, (p=0,000). Mask leak increased from 14 (5-47)%, 46 (20-79)%, 79 (39-98)% to 98 (91-100)%, (p=0,000).PIP showed a slight increase with the increasing gas flow rates to 35.6 (33.7-37.0) cm HO at 15 L/ min. PEEP increased significantly to 26.4 (24.5- 27.4) cm HO at 15 L/min.Experiment 2: There was no significant difference in delivered V(p=0.42) or mask leak (p=0.51) with changing gas flow rates.Conclusion: Changing gas flow rates during PPV effected Vdelivery, mask leak and airway pressures. It is therefore advisable not to alter the gas flow rate during resuscitation.