Efficient oxygen mask for patients undergoing hyperbaric oxygen therapy.

Hyperbaric oxygen (HBO) is established therapy for various disorders, but its effectiveness depends on the efficiency of the oxygen delivery system. A mask oxygen delivery system, consisting of the standard USAF aviator's A-14 regulator and the MBU-5/P oxygen mask, is installed in all USAF hyperbaric chambers. The efficiency of the mask oxygen delivery system at the USAF Hyperbaric Center, Brooks AFB, Tx, was evaluated breath-by-breath at sea level and 2.4 ATA via two different measuring techniques. Three groups of subjects were evaluated. Four subjects in Group I and seven subjects in Group II were randomly selected to use a single instrumented mask which was improperly fitted. The result was variable inspired oxygen levels from 64% to 100%. Six subjects in Group III wore properly fitted masks and achieved end-inspired oxygen levels ranging from 96% to 99%, for a mean of 97.8 +/- 0.5 (S.E.)%. A mean end-inspired oxygen level of 88,5 +/- 3,5 (S.E.)% was achieved within 5 min of mask donning. Inspiratory gas analyses indicate that the USAF aviator MBU-5/P mask and the A-14 regulator as used at the USAF Hyperbaric Center constitute a highly efficient oxygen delivery system for HBO therapy. This view has been refleced in arterial blood gas measurements and in preliminary data from tissue oxygen measurements in a gas gangrene patient. Future improvements in patient therapy masks are recommended.