Summerfield, Doug

Background Whether lung fluid accumulates in acclimating individuals at high altitude (HA) remains controversial. Purpose To assess the effect of HA on lung fluid regulation. Methods/Results Systolic pulmonary artery pressure (sPAP) (echo), lung diffusing capacity for CO (DLCO), pulmonary capillary blood volume (Vc), alveolar‐capillary conductance (Dm) (single breath method), ultrasound lung comets (ULCs) and pulmonary function (PFTs) were assessed in 8 healthy adults at sea‐level and after 1 and 9 days at Mt. Everest Base Camp (EBC), Nepal (5150 m). Also, after 5 days at EBC, DLCO and PFTs were assessed in 5 subjects pre‐and post‐acute albuterol administration. EBC was reached after an 8 d hike at progressively increasing altitudes starting at 2800 m. Altitude exposure increased sPAP, had no effect on DLCO, increased Dm and decreased Vc with a subsequent increase in Dm/Vc, and decreased the number of ULCs (Table 1). There was no change in FVC or FEV 1 but an increase in MEF 50 . Albuterol administration increased PEF (11.85±1.52 vs. 12.40±1.45 L/s) and MEF 50 (4.85±0.77 vs. 6.00±1.30 L/s) but had no effect on DLCO, Dm or Dm/Vc. Conclusion These data suggest that lung fluid is decreased in acclimating healthy humans at high altitude. Funding: Mayo Clinic & The North Face.

BACKGROUND Exposure to high altitude (HA) results in sympathetic nervous system (SNS) activation. This might interact with HA related illness. HRV is a technique to quantify SNS and parasympathetic nervous system (PNS) interactions and thus offers a noninvasive index in extreme environments. OBJECTIVE To quantify the changes in HRV in elite athletes (AT), acclimatized for 2 mo. at Everest base camp (BC) prior to summiting, relative to a control group (CT) (climbing and acclimatizing to BC in 3 wks). METHODS AT (N=4, Age=35±10 y, BMI=22±2, M/F ratio 2/2) and CT (N=8, Age=35±10 y, BMI=26±2, M/F ratio 8/0) performed autonomic tests consisting of quiet breathing, paced breathing prior to, mid‐way at BC and at 2 wks post expedition. RESULTS At BC, AT had (compared to CT) higher HR (p=0.07) and reduced HRV (SDNN, p=0.09). For AT and CT combined: measures of HRV were reduced at BC (SDNN, p=0.05, Poincare length, p=0.05) and remained below baseline 2 wks post climb (SDNN, p=0.01; PCL, p=0.01). CONCULSION HRV is reduced with HA exposure in both AT and CT and remains reduced 2 wks post exposure, suggesting either SNS activation and/or PNS withdrawal. FUNDING : Mayo Clinic & The North Face.

Background It is documented that cognitive performance can diminish with altitude, but the sensitivity of specific tests have not been investigated. Our objective was to assess and compare cognitive performance from several tests and relate this to quality of sleep and acute mountain sickness (AMS). Methods During an Everest expedition, 3 cognitive tests (Stroop, Trail Making, and a proprietary motor accuracy test) were used along with a questionnaire to assess sleep and AMS. Six athlete climbers and 9 core team members were assessed pre and post‐expedition and at several time points during the expedition (up to 17,500 ft). Results To normalize for individual differences, scores were assessed as % change from baseline. There was no difference in the variation between repeated attempts in a single testing session (0.19<p<0.87), demonstrating that each test was reproducible. There was no decrement in test scores with altitude, nor was there an association with reported sleep quality. The Stroop performance was associated with AMS (p<0.05) and trending with headache (p< 0.15). The in‐house motor test trended towards an association with AMS and headache (p<0.15). However, the trail making test was not associated with AMS/headache. Conclusion With appropriate acclimatization, cognitive performance is maintained at altitude but is linked to presence of headache and AMS. Mayo Clinic and TNF.