Effects of flying time on the cerebral hemodynamics of pilots

Objective To investigate the effects of flying time on the cerebral hemodynamics of pilots.Methods Ninety-nine active pilots,including fighter and helicopter pilots,were divided into flying time ≤600 h group (aged 27.9±4.3 yr,n=42) and flying time ＞600 h group (aged 32.5±5.9 yr,n=57).Sixty-nine healthy volunteers (age 26.6±4.5 yr) were selected as the control group.The systolic velocity (Vs),diastolic velocity (Vd),mean velocity(Vm) and pulsatility index (PI) of anterior cerebral artery,vertebral artery and the basilar artery of subjects were measured by tanscranial Doppler sonography technique.The data were processed by the covariance analysis with age covariate.Results Compared with the control group,the flying time ≤600 h group showed significantly increased PI of basilar artery and right posterior cerebral artery (t =2.27,2.11,P＜0.05),while flying time ＞600 h group had significantly lower PI of right anterior cerebral artery (t=2.07,P＜0.05).Compared with those of flying time ≤600 h group,Vs of left posterior cerebral artery and Vd of right middle cerebral artery of flying time ＞ 600 h group increased significantly (t=2.00,2.07,P＜0.05),and PI of right postcrior cerebral artery was significantly low (t=2.51,P＜0.05).Other hemodynamic parameters had no statistically changes.Conclusions The durable flight training has certain effects on improving pilot's regulation,vasodilatation and complaisance of cerebral arteries. Key words: Brain;  Blood flow velocity;  Pulsatility flow;  Ultrasonography, Doppler, transcranial