Incidence and Symptoms of High Altitude Illness in South Pole Workers: Antarctic Study of Altitude Physiology (ASAP)

Introduction Each year, the US Antarctic Program rapidly transports scientists and support personnel from sea level (SL) to the South Pole (SP, 2835 m) providing a unique natural laboratory to quantify the incidence of acute mountain sickness (AMS), patterns of altitude related symptoms and the field effectiveness of acetazolamide in a highly controlled setting. We hypothesized that the combination of rapid ascent (3 hr), accentuated hypobarism (relative to altitude), cold, and immediate exertion would increase altitude illness risk. Methods Medically screened adults (N = 246, age = 37 ± 11 yr, 30% female, BMI = 26 ± 4 kg/m 2 ) were recruited. All underwent SL and SP physiological evaluation, completed Lake Louise symptom questionnaires (LLSQ, to define AMS), and answered additional symptom related questions (eg, exertional dyspnea, mental status, cough, edema and general health), during the 1st week at altitude. Acetazolamide, while not mandatory, was used by 40% of participants. Results At SP, the barometric pressure resulted in physiological altitudes that approached 3400 m, while T ° C averaged -42, humidity 0.03%. Arterial oxygen saturation averaged 89% ± 3%. Overall, 52% developed LLSQ defined AMS. The most common symptoms reported were exertional dyspnea-(87%), sleeping difficulty-(74%), headache-(66%), fatigue-(65%), and dizziness/lightheadedness-(46%). Symptom severity peaked on days 1-2, yet in >20% exertional dyspnea, fatigue and sleep problems persisted through day 7. AMS incidence was similar between those using acetazolamide and those abstaining (51 vs. 52%, P = 0.87). Those who used acetazolamide tended to be older, have less altitude experience, worse symptoms on previous exposures, and less SP experience. Conclusion The incidence of AMS at SP tended to be higher than previously reports in other geographic locations at similar altitudes. Thus, the SP constitutes a more intense altitude exposure than might be expected considering physical altitude alone. Many symptoms persist, possibly due to extremely cold, arid conditions and the benefits of acetazolamide appeared negligible, though it may have prevented more severe symptoms in higher risk subjects

Exercise-related change in airway blood flow in humans: Relationship to changes in cardiac output and ventilation

This study examined the relationship between airway blood flow (Q˙aw), ventilation (V˙E) and cardiac output (Q˙tot) during exercise in healthy humans (n=12, mean age 34±11 yr). Q˙aw was estimated from the uptake of the soluble gas dimethyl ether while V˙E and Q˙tot were measured using open circuit spirometry. Measurements were made prior to and during exercise at 34±5W (Load 1) and 68±10W (Load 2) and following the cessation of exercise (recovery). Q˙aw increased in a stepwise fashion (P<0.05) from rest (52.8±19.5μlmin−1ml−1) to exercise at Load 1 (67.0±20.3μlmin−1ml−1) and Load 2 (84.0±22.9μlmin−1ml−1) before returning to pre-exercise levels in recovery (51.7±13.2μlmin−1ml−1). Q˙aw was positively correlated with both Q˙tot (r=0.58, P<0.01) and V˙E (r=0.50, P<0.01). These results demonstrate that the increase in Q˙aw is linked to an exercise related increase in both Q˙tot and V˙E and may be necessary to prevent excessive airway cooling and drying