Saccadic velocity and pupillary reflexes during acclimatization to altitude (4300 m).
BACKGROUND
Oculometrics have been shown to be responsive to acute hypoxemia. We investigated whether oculometrics could be used as an objective index of a hypoxic effect on the central nervous system (CNS) during 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).


METHODS
After sea-level, baseline (SLB) measurements were obtained, 18 men (19-33 yr) were transported to Pikes Peak, CO (4300 m), where they remained for 14 d. 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).


RESULTS
PD and CL decreased from SLB on days 1-4 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 d. SV increased over days 1-6 then returned toward SLB with continued exposure, similar to changes in urinary catecholamines. With acclimatization, CL correlated with HR and SpO2; SV correlated with PCO2, HR, and SpO2. AMS severity peaked during days 2-4, returned toward SLB over the next 10 d, and correlated only with CL (p = 0.045).


CONCLUSIONS
Oculometrics can be used as an indicator of CNS hypoxia and altitude acclimatization, although there was no strong correlation with AMS severity.
Cymerman
Allen
A
U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA. allen.cymerman@us.army.mil
Muza
Stephen R
SR
Friedlander
Anne L
AL
Fulco
Charles S
CS
Rock
Paul B
PB
D000064:Acclimatization / Q000502:physiology*; D000208:Acute Disease; D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000532:Altitude Sickness / Q000503:physiopathology*; D001274:Atmospheric Pressure; D006801:Humans; D008297:Male; D008889:Military Personnel; D011680:Pupil / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors