Hypoxia Conditioning for High-Altitude Pre-acclimatization

Purpose Main purposes of pre-acclimatization by hypoxia conditioning (HC) are the prevention of high-altitude illnesses and maintenance of aerobic exercise performance. However, robust evidence for those effects or evidence-based guidelines for exposure strategies, including recommendations to ensure safety, are largely lacking. Therefore, we summarize the current knowledge on the physiology of acclimatization to hypoxia and HC with the aim to derive implications for pre-acclimatization strategies before going on high-altitude treks and expeditions. Methods Based on the literature search and personal experience, core studies and important observations have been selected in order to present a balanced view on the current knowledge of high-altitude illnesses and the acclimatization process, specifically focusing on pre-acclimatization strategies by HC. Results and Conclusions It may be concluded that in certain cases even short periods (e.g., 7 h) of pre-acclimatization by HC are effective, but longer periods (e.g., > 60 h) are needed to elicit more robust effects. About 300 h of HC (intermittently applied) may be the optimal preparation for extreme altitude sojourns, although every additional hour spent in hypoxia may confer further benefits. The inclusion of hypobaric exposures (i.e., real altitude) in pre-acclimatization protocols could further increase their efficacy. The level of simulated altitude is progressively increased or individually adjusted ideally. HC should not be terminated earlier than 1–2 weeks before altitude sojourn. Medical monitoring of the pre-acclimatization program is strongly recommended.

Reevaluation of excessive erythrocytosis in diagnosing chronic mountain sickness in men from the world’s highest city

The diagnosis of chronic mountain sickness (CMS) is based on a score including 7 clinical features (breathlessness, sleep disturbance, cyanosis, venous dilatation, paresthesia, headache, and tinnitus) in the setting of extreme erythrocytosis. Examining individuals in La Rinconada, Peru, the highest city in the world, the authors demonstrated that CMS at extreme altitude is not linked to elevation of hemoglobin, since CMS+ and CMS− individuals had similar levels of erythrocytosis.

New Guinea highland wild dogs are the original New Guinea singing dogs

New Guinea singing dogs (NGSD) are identifiable by their namesake vocalizations, which are unlike any other canid population. Their novel behaviors and potential singular origin during dog domestication make them an attractive, but elusive, subject for evolutionary and conservation study. Although once plentiful on the island of New Guinea (NG), they were presumed to currently exist only in captivity. This conclusion was based on the lack of sightings in the lowlands of the island and the concurrent expansion of European- and Asian-derived dogs. We have analyzed the first nuclear genomes from a canid population discovered during a recent expedition to the highlands of NG. The extreme altitude (>4,000 m) of the highland wild dogs’ (HWD) observed range and confirmed vocalizations indicate their potential to be a wild NGSD population. Comparison of single-nucleotide polymorphism genotypes shows strong similarity between HWD and the homogeneous captive NGSD, with the HWD showing significantly higher genetic diversity. Admixture analyses and estimation of shared haplotypes with phylogenetically diverse populations also indicates the HWD is a novel population within the distinct evolutionary lineage of Oceanic canids. Taken together, these data indicate the HWD possesses a distinct potential to aid in the conservation of NGSD both in the wild and under human care.

Knowledge, Attitude and Practices Regarding Extreme Environments and Cold Adaptation at Extreme Altitudes on the Himalayan Ranges

Introduction: Extreme-altitudes (5500 m/18045 ft and higher) pose environmental, psychophysiological, infrastructural, logistic, and ergonomic challenges that question explorer’s adaptability and mission-efficiency due to isolation, monotony, intimidating environment and terse health conditions. The assessment of an explorer’s comprehensive adaptability in extreme-altitudes is of paramount importance in ensuring mission-preparedness. Knowledge, attitude, and practices (KAP) of explorers staying on extreme-altitudes was assessed through personal interview technique. Methods: 125 healthy, acclimatized, mountain-trained explorers staying above 4570 m/15000 ft in winter-season for at least 30 days on extreme-altitudes were assessed by a single cross-sectional study through personal interviews on KAP related to extreme-altitude and cold-adaptation. Results: Mean duration of stay on extreme-altitude was 55.7 days. All explorers knew about difficulties and health-problems at extremealtitude. All explorers felt that mountain-training and acclimatization were beneficial. 92% felt that mission tenure of 90 days on the extreme-altitude was adequate. 92.8% felt they were adequately trained for the extreme-altitude; however, only 52% felt confident about health-training. 66.4% did preventive rewarming of extremities. 66.4% regularly smoked/chewed tobacco. 57.6% had sleep problems and 64% had altered appetite. 26.4% felt difficulties related to living conditions, infrastructure, and logistics. Conclusion: Explorers at extreme-altitude exhibited adequate knowledge and performed activities with progressive attitude and healthy practices. Explorers endured altered psychophysiology at extreme-altitude and regarded the utility of training and acclimatization programs. Knowledge-practice gap existed towards tobacco consumption. There was a felt need for the improvement of living conditions, infrastructure, logistics, and health-related training.

Regulation and adaptation of endocrine axes at high altitude

As a model of extreme conditions, eight healthy women, part of a 40-member Nepal mountain-climbing expedition, were monitored for dynamic endocrine adaptations. Endocrine measurements were made at frequent intervals over a 6–10-h period at four altitudes: 450 m, 4,800 m (base camp), 6,050 m, and again at 4,800 m (on descent) after an acclimatization (A) period (4,800 mA). Quantified hormones were growth hormone (GH), prolactin (PROL), cortisol (Cort), thyroid-stimulating hormone (TSH), and free thyroxine. These hormones are important to the anabolic/catabolic balance of the body, and are vital to growth, homeostasis, hypothalamic inhibition, regulation of stress, and metabolism. A key secondary question was the degree to which acclimatization can stabilize hormonal disruption. On the basis of statistical false discovery rates, the present analyses unveil marked adaptive changes in the thyroid axis at the level of pulsatile secretion of the pituitary hormone TSH and its downstream product, free thyroxine; strong effects on the mass of GH, TSH, Cort, and PROL secretion per burst; and prominent pulsatile frequency disruption and recovery for PROL and Cort. Because pulsatility changes reflect de facto perturbations in hypothalamo-pituitary control mechanisms, the present data introduce the concept of both frequency- and amplitude-dependent adaptive control of brain-pituitary neuroendocrine signals under conditions of extreme altitude exertion and exposure.