Auto-Peep Associated with Excessive Oxygen Flow through Five Manual Resuscitators

Abstract

I undertook this study to confirm or invalidate my observation that health care providers use oxygen flows higher than recommended by the manufacturers of manual resuscitators and to explore possible clinical consequences associated with use of high flows. MATERIALS & METHODS: Part 1. A convenience sample of 7 Registered Respiratory Therapists (RRTs), 3 second-year respiratory therapy students who had completed the cardiopulmonary resuscitation component of their curriculum, 6 critical care registered nurses (CCRNS), 2 emergency room nurses, and 2 registered nurses who were instruc- tors in Advanced Cardiac Life Support were instructed to set the oxygen flow to a Mercury CPR Bag equipped with an oxygen reservoir in a manner con- sistent with their normal practice. Flow output to the resuscitator was mea- sured using a calibrated Timeter RT-200. Part 2. I evaluated the effect of high oxygen flow on the performance of 4 disposable and 1 nondisposable bag-valve manual resuscitator. An oxygen flow of 15 L/min was introduced to each man- ual resuscitator while the resuscitator was connected to the inlet port of a test lung set to simulate normal compliance and airway resistance. The ‘lung’ was ventilated at a rate of 12 breaths/min and a tidal volume of 0.7-0.8 L. Flow was increased in 5 L/min increments and auto-PEEP readings were taken, using the test lung's "Intra-Pulmonary" manometer. Test lung compliance was than reduced and the procedure repeated. The compliance was then returned to normal and the airway resistance increased. The procedure was repeated. RESULTS: Part 1. Flows averaged 36.9 L/min compared to rec- ommended flows of 15 L/min. Part 2 showed that high oxygen flows may result in clinically important levels of auto-PEEP. Auto-PEEP appeared at flows as low as 35 L/min in one resuscitator and at flows of 55 L/min in all resus- citators under conditions of high airway resistance. CONCLUSIONS: Results suggest that even trained health care providers ignore or are unfamiliar with manufacturer recommendations. This disregard could have important clin- ical consequences. Stronger emphasis should be placed on the correct use of manual resuscitators in programs designed to prepare health care providers to provide assisted manual ventilation. [Respir Care 1996;41(11):1009-1012]