TECHNIQUES OF EMERGENCY VENTILATION - A MODEL TO EVALUATE TIDAL VOLUME, AIRWAY PRESSURE, AND GASTRIC INSUFFLATION

We designed a model to evaluate the effectiveness of various noninvasive methods of ventilation. The upper airway was simulated with the head of a Resusci-Annie which was attached to a test lung. The esophagus and stomach were simulated with a Penrose drain connected to a rolling seal spirometer via a PEEP valve. Fifteen paramedic volunteers ventilated the model utilizing mouth-to-mouth, mouth-to-mask, bag-valve-mask, or portable field ventilator (Impact or HARV). Recording of tidal volume, gastric volume, and proximal and distal airway pressure was completed at three different levels of compliance. At normal compliance, all methods except the HARV met or exceeded American Heart Association standards. As compliance decreased, tidal volume fell and gastric insufflation increased. At a compliance of 0.02 L/cm H2O all methods failed to meet AHA standards and gastric insufflation volume equalled delivered tidal volumes for mouth-to-mouth and mouth-to-mask techniques. Mouth-to-mouth and mouth-to-mask techniques generated the largest tidal volumes but also created the largest volume of gastric insufflation. The Impact ventilator provided an acceptable tidal volume with minimal gastric insufflation. Our results suggest that mouth-to-mask ventilation with supplemental oxygen enrichment is the most efficient technique for non-invasive airway management.