The Impact of High Levels of Nitrogen in the Breathing Gas and In-Flight Denitrogenation on the Risk of Decompression Sickness (DCS) During Simulated Altitude Exposure

Abstract

Abstract : Military aircraft oxygen systems may not always deliver 100% O2. Nitrogen and argon are present to various levels. Determining the effect of these inert gas levels on denitrogenation and decompression sickness (DCS) risk was needed to better manage the operational incidence of DCS. The partial pressure gradient of nitrogen partly determines the extent and rate of denitrogenation during altitude exposure, not the percentage of N2 in the mixture. The degree of denitrogenation influences the extent of bubble formation and DCS incidence. It was found that the increased nitrogen levels in the breathing gas while at altitudes of 18,000 to 25,000 ft did not increase DCS risk. Contrary to the results above 18,000 ft, the use of a high N2 breathing gas at 16,000 ft increased DCS incidence when compared to exposures with 100% O2. It was also found that stage prebreathing, or in-flight denitrogenation, at 16,000 ft prior to ascent to 25,000 ft is effective in reducing the DCS risk when compared to zero prebreathe exposures.