Performance of the Volumetric Diffusive Respirator at Altitude
Special rept. Jul 2012-Dec 2013
SCHOOL OF AEROSPACE MEDICINE WRIGHT-PATTERSON AFB OH AEROMEDICAL RESEARCH DEPT
Pagination or Media Count:
Aeromedical transport of ventilated patients requires continued performance of equipment at altitude. Changes in barometric pressure with increasing altitude are associated with alterations in gas density, which can affect ventilator performance. The volumetric diffusive respirator is a pneumatic ventilator used by the U.S. Army Burn Team and the U.S. Air Force Lung Team for patients with hypoxemic respiratory failure. The volumetric diffusive respirator was tested in a man-rated altitude chamber at sea level, 8,000, and 16,000 feet corresponding to barometric pressures of 760, 564, and 412 mmHg. Airway pressures, flow, and volume were continuously measured with a pneumotachograph and differential pressure transducer during ventilation of a test lung. Data were recorded for later analysis. Mean measured values at each altitude were compared to sea level data using analysis of variance. At each increase in altitude, positive end expiratory pressure and peak inspiratory pressure were increased by 30-40. Tidal volume remained within 15 of sea level values. Respiratory rate fell, while inspiratory time increased and high frequency pulse rate fell. At altitude, positive end expiratory pressure and peak inspiratory pressure increase while pulse frequency diminishes. These increases can result in high airway pressures and should be corrected to prevent untoward events.
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