A simple emergency underwater breathing aid for helicopter escape

Experiments were undertaken to determine whether a simple rebreathing system, termed "Air Pocket" (AP), could, when integrated into an immersion dry suit, extend the underwater survival time of individuals when compared with their maximum breath hold time (BHTmax). Eight naive healthy male subjects undertook a series of resting submersions and simulated simple helicopter underwater escapes in water 25 degrees C and 10 degrees C. During the submersions the subjects breath-held maximally and then rebreathed using an otherwise empty AP. the BHTmax times of subjects and the total time they could remain underwater (RBT) were recorded. The results showed that the ability to rebreathe following a BHTmax extended the time all subjects could remain submerged, resting or exercising, in cold water by a factor of at least two. The average BHTmax during simulated helicopter underwater escapes in the cold water was 17.2 s. It is concluded that the ability of subjects to rebreathe immediately following maximum breath holding extends the time they can remain submerged in cold water to as much as 60 s. Further, if used unprimed, a simple rebreathing system will not introduce any additional dangers such as a pulmonary over-pressure accident.