The effect of hypobaric pressure exposure on electrogastrogram of pilots

XUXian-rong; ZHAILi-hong; XUHua; LIUYu-hua

Abstract：Objective We aimed to study the effect of hypobaric pressure exposure on the electrogastrogram (EGG) of pilots. Methods A total of 25 helicopter pilots under physical examination for change to new-type of aircraft participated in this study.The examinees were seated in a hypobaric chamber and recorded with EGG for 4 minutes. They then ascended at a speed of 20 m/s,stayed at 1000,2000,3000,4000 m for 10 minutes respectively,and were recorded with EGG for 4 minutes at each stop. The pilots finally descended back to the ground at a speed of 5 m/s. Indices such as the average amplitude,frequency,percentage of dysrhythmia, percentage of normal slow waves,etc.at different heights were observed. Results The effects of hypobaric pressure exposure on pilots' EGG is as follows:①the average amplitude showed a overall trend of decrease with the increase of height,e.g,the average amplitudes at 1000 and 3000 m were 304.2μV and 297.6μV respectively,significantly lower than the average EGG on ground (357.7μV,t=2.69,2.42,P<0.05),though two pilots with mild abdominal distension showed the opposite,as average amplitudes increasing with ascent;②the average frequency generally did not change significantly,but the two cases with mild abdominal distension showed a slightly higher average frequency;③the average percentage of disrhythmia was significantly different only at 3000 m height (24.3%),compared to that on ground (28.2%,t=3.23,P<0.01);however,the two pilots with mild abdominal distension showed increased average percentage of disrhythmia;④the average percentage of normal slow waves showed no significant changes in general. Conclusion The effect of hypobaric pressure exposure (at different heights toward 4000 m) on pilots' EGG varied;however,for pilots with obvious abdominal distension or pain,average amplitude and average percentage of dysrhythmia might provide valuable objective indication. With a more in-depth and meticulous work to control the influential factors,EGG indices might be used to objectively evaluate barometerism.