Saccadic Velocity and Pupillary Reflexes During Acclimatization to Altitude (4300m)

摘要

Oculometrics have been shown to be responsive to hypoxemia. We investigated whether oculometrics could be used as an objective index of a hypoxic effect on the central nervous system (CNS) and altitude acclimatization. We hypothesized that oculomotor reflexes (pupil diameter (PD), constriction amplitude (CA), constriction latency (CL), and saccadic velocity (SV)) changed in concert with a select number of accepted acclimatization variables and that these changes correlated with the severity of acute mountain sickness (AMS). After sea-level, baseline (SLB) measurements were obtained, 18 men (19-33 yrs) were transported to Pikes Peak, CO (4,300 m) where they remained for 14 days. Periodic measurements (days 1-4, 6, 7, 9, 10, and 12) were made of PD, CA, CL, and SV in addition to heart rate (HR), pulse oximetry (SpO2), end-tidal PO2 and PCO2, 24-h urinary catecholamine concentrations, and AMS severity (environmental symptoms questionnaire, ESQ). PD and CL decreased from SLB for first 1-4 days and subsequently returned toward SLB; these changes paralleled changes in ventilatory and circulatory variables. CA decreased on days 1 and 2 and remained decreased for 12 days. SV increased over the first 6 days then returned toward SLB with continued exposure, similar to the changes in urinary catecholamines. With acclimatization, CL con-elated with HR and SpO2; SV correlated with PCO2, HR, and SpO2. AMS severity peaked during days 2-4, followed by a return toward SLB over the next 10 days. Oculometrics did not correlate with the severity of AMS. Oculometrics can be used as an indicator of CNS hypoxia and altitude acclimatization, although there was no strong correlation with AMS severity.