Comparative analysis on data of ear baric function by hypobaric chamber test between helicopter and fighter pilots

Objective To compare the ear baric function of helicopter pilots and fighter pilots and to investigate the aeromedical support on helicopter pilots' ear baric function. Methods One hundred and thirty helicopter pilots and 90 fighter pilots were inquired about their health history and examined by electric otoscopy (EOS), pure tone audiometry (PTA), acoustic immitance measurement (AIM), rhinoscopy (RS) and nasal endoscopy (NES). Those who were without contraindication to hypobaric chamber test (HCT) were subjected to HCT as follows: ①both helicopter and fighter pilots were asked to sit in the chamber and climbed up to 4000 m with the velocity of 15-20 m/s, remained for 5 min and then declined to ground level with the velocity of 5 m/s; ②fighter pilots were climbed to 4 000 m with the velocity of 20-30 m/s, stayed for 5 min and declined to the ground level with the velocity of 20-25 m/s. After HCT, they were re-examined by EOS, PTA and AIM. The incidence of ear baric dysfunction (EBDF) was compared between helicopter and fighter pilots. Results ①One helicopter pilot did not undergo HCT due to cold-induced grade II eardrum congestion diagnosed by EOS, mild conductive hearing loss by PTA and C-shaped curve by AIM. ②The incidence of EBDF was 6.20% in helicopter pilots when they were declining with slow rate (5 m/s), significantly higher than that in fighter pilots (0.00%) (χ2=4.16, P 0.05). Conclusions It should take different climbing and descending rates in the HCT ear baric function evaluation or aeromedical training for different aircraft pilots. Key words: Ear, middle; Barotrauma; Hypobaric chamber; Pilots