Modulação autonômica em pilotos militares de combate e transporte da Força Aérea Brasileira: um estudo caso-controle

Abstract

Introduction: Fighter pilots are exposed during flight to high levels of acceleration (G-force), which requires the action of neurocardiovascular mechanisms for homeostasis maintenance. However, there is still no consensus in the literature regarding the chronic effects of regular exposure to such forces on the neurocardiovascular system. Objective: This case-control study compared autonomic modulation in combat pilots, transport pilots and non-pilots, testing the hypothesis that there would be differences between these groups. Additionally, autonomic indices were correlated with the level of cardiorespiratory fitness and experience in terms of flight hours. Methods: Fighter pilots (PC; n = 21), transport pilots (PT; n = 8) and non-pilots (NP; n = 20) performed the Tilt Test (TT). The protocol included 15 min of resting in the supine position, followed by three 1-min stimuli with passive tilt at 70° (T1, T2 and T3), followed by 5-min recovery after each stimulus (R1, R2 and R3). During TT, heart rate was recorded beat-to-beat using a cardiotachometer (Polar® S810i, Polar Electro OY, Kempele, Finland) for heart rate variability (HRV) analysis. Results: No differences were detected between groups or times for changes (Δ) in HRV indices during TT. However, analysis of the areas under the curves revealed a greater reduction in indices reflecting vagal modulation in PT vs. PC and NP in response to TT (rMSSD, pNN50 and SDNN; P < 0.05), as well as a greater increase in sympathovagal balance in PT vs. other groups (LF/HF; P < 0.05). VO2max showed a strong inverse relationship with PC vagal reserve (r = - 0.74; P = 0.01). Furthermore, PC flight hours were positively correlated with HFnu (r = 0.47; P = 0.02), and inversely with LFnu (r = -0.55; P = 0.01) and LF/HF ( r = -0.46; P = 0.03) at rest. Conclusion: TT-induced vagal withdrawal responses and increased sympathovagal balance were attenuated in PC vs. PT, and similar between PC and NP