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.

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