[abstract] A SYSTEM FOR OXYGEN REMOVAL FROM HYPERBARIC ATMOSPHERES USING A DIFFERENTIAL PERMIABILITY GAS SEPARATION DEVICE.

Abstract

BACKGROUND: Oxygen accumulation in hyperbaric chambers during clinical treatments presents an increased fire hazard. Nitrogen-oxygen saturation diving, in excess of 2.5 ATA, requires that the chamber atmosphere contains less oxygen than air to prevent pulmonary oxygen toxicity. The closed loop system described here provides a method to reduce and control the oxygen content of hyperbaric environments with small, simple equipment and low energy requirements. MATERIALS AND METHODS: A samll oil-free, low pressure compressor removes gas from the hyperbaric chamber and compresses it to a pressure 1-5 ATA greater than the chamber pressure. The gas then passes through a differential permeability gas seapration device and is returned to the chamber. A single valve on the gas separator controls the differential pressure across the separator membrane and the flow rate of gas through the device. Gas was sampled for 02 and CO2 content as it leaves and returns to the chamber, and at the permeate (discard) exit of the separator. RESULTS: The O2 content of the gas returned to the chamber can be regulated to contain from 25-85percent of that leaving the chamber. CO2 is more permeable than O2 and the return levels can be reduced to less than 10percent of that in the chamber. Over 80percent of water vapor is removed. CONCLUSIONS: This system provides a simple means to reduce and control the O2 content of hyperbaric atmospheres initially composed of compressed air or nitrox. Since the intake gas is already pressurized, energy requirements are low.