Nutritional physiology and body composition changes during a rapid ascent to high altitude.

Exposure to high altitude might cause the body to adapt with negative energy and fluid balance that compromise body composition and physical performance. In this field study involving 12 healthy adults, sex-balanced, and aged 29 ± 4 years with a body mass index of 21.6 ± 1.8 kg/m2, we investigated the effects of a 4-day trekking up to 4556 m a.s.l. on Monte Rosa (Alps, Italy). The food intake was recorded using food diaries and nutrient averages were calculated. The bio-impedance analysis was performed at low and high altitudes, and a wearable biosensor (Swemax) was used to track hydro-saline losses in two participants. Daily total energy intake was 3348 ± 386 kcal for males and 2804 ± 415 kcal for females (13%-14% protein, 35% fat, 44%-46% carbohydrates). Although there was a significant body weight loss (65.0 ± 9.3 vs. 64.2 ± 9.10 kg, p < 0.001, d = 1.398), no significant changes in body composition parameter were found but a trend in the increase of the bioelectrical phase angle in males (p = 0.059, d = -0.991). Body water percentage significantly changed (p = 0.026, η2 p = 0.440), but the absolute water did not, suggesting that the weight loss was not due to water loss. Salivary and urinary osmolality did not change. A reduction in sweat rate at higher altitudes was observed in both participants. Interestingly, salivary leptin increased (p = 0.014, η2 p = 0.510), and salivary ghrelin decreased (p = 0.036, η2 p  = 0.403). Therefore, the 4-day trekking at altitude of hypoxia exposure induced changes in satiety and appetite hormones. High altitude expeditions require more specific nutritional guidance, and using multiplex analysis could help in monitoring fluid balance and body composition.

Ventilatory function and oxygen delivery at high altitude in the Himalayas.

This study aimed to evaluate changes in lung function assessed by spirometry and blood gas content in healthy high-altitude sojourners during a trek in the Himalayas. A group of 19 Italian adults (11 males and 8 females, mean age 43 ± 15 years, and BMI 24.2 ± 3.7 kg/m2) were evaluated as part of a Mount Everest expedition in Nepal. Spirometry and arterial blood gas content were evaluated at baseline in Kathmandu (≈1400 m), at the Pyramid Laboratory - Observatory (peak altitude of ≈5000 m), and on return to Kathmandu 2-3 days after arrival at each site. All participants took 250 mg of acetazolamide per os once daily during the ascent. We found that arterial hemoglobin saturation, O2 and CO2 partial pressures, and the bicarbonate level all decreased (in all cases, p < 0.001 with R2 =0.70-0.90), while pHa was maintained stable at the peak altitude. Forced vital capacity (FVC) remained stable, while forced expiratory volume in 1 s (FEV1) decreased (p = 0.010, n2p =0.228), resulting in a lower FEV1/FVC ratio (p < 0.001, n2p =0.380). The best predictor for acute mountain sickness was the O2 partial pressure at the peak altitude (p = 0.004, R2 =0.39). Finger pulse oximetry overestimated peripheral saturation relative to arterial saturation. We conclude that high-altitude hypoxia alters the respiratory function and the oxygen saturation of the arterial blood hemoglobin. Additionally, air rarefaction and temperature reduction, favoring hypoxic bronchoconstriction, could affect respiration. Pulse oximetry seems not enough to assist medical decisions at high altitudes.

Clinical features and health-threatening conditions of the trek to Capanna Margherita.

BACKGROUND: Since trips to high altitude have become popular, reports on clinical and environmental characteristics during expeditions to popular destinations are needed. METHODS: A group of 15 healthy adults was monitored during a trek to Capanna Margherita (4556 m). A hypoxic stress test was applied before the expedition started. Environmental characteristics were acquired with a portable device. Vital signs were compared at low and high altitude, and altitude sickness was diagnosed by the Lake Louise scoring system. Ocular symptoms and intraocular pressure were recorded. RESULTS: Temperature ranged from -3.5 to 31.3 °C and relative humidity from 36 to 95% during the trek. Acute mountain sickness was diagnosed in 40% of participants, more frequently in women, and slightly associated with a greater drop in SpO2. Heart rate and blood pressure increased, while peripheral saturation and intraocular pressure decreased, in response to altitude hypoxia. CONCLUSIONS: Rapid ascents, as in the most common expedition plans, should be carefully supervised because of the common occurrence of AMS, especially in women. Among organ districts, the eye should deserve more attention in high-altitude medicine. Analyses of environmental conditions, together with predictive methods and early identification of health-threatening conditions, are of great value in supporting further recreational, professional and scientific expeditions to the most intriguing altitude sites.