High altitude medicine & biology最新文献

Rana, Vipin, Pradeep Kumar, Sandeepan Bandopadhyay, Vijay K. Sharma, Meenu Dangi, Dattakiran Joshi, Sanjay Kumar Mishra, Satyabrat Srikumar, and V.A. Arun. Central retinal artery occlusion in young adults at high altitude: thin air, high stakes. High Alt Med Biol. 00:000-000, 2024.-We present five cases of young security personnel who were posted at high altitude (HA) for a duration of at least 6 months and presented with a sudden decrease of vision in one eye. The diagnosis of central retinal artery occlusion (CRAO) was made in all patients. Fundus fluorescein angiography and optical coherence tomography of the macula supported the diagnosis. None of these cases had any preexisting comorbidities. Erythrocytosis was noticed in all patients, and two of them had hyperhomocysteinemia. Four out of five patients showed either middle cerebral artery or internal carotid artery (ICA) thrombosis on computed tomography angiography. The patients were managed by a team of ophthalmologist, hematologist, vascular surgeon, and neurologist. In cases of incomplete ICA occlusion, patients were managed surgically. However, in the case of complete ICA occlusion, management was conservative with antiplatelet drugs. This case series highlights HA-associated erythrocytosis and hyperhomocysteinemia as important risk factors for CRAO in young individuals stationed at HA.

Ramchandani, Rashi, Ioana Tereza Florica, Zier Zhou, Aziz Alemi, and Adrian Baranchuk. Review of athletic guidelines for high-altitude training and acclimatization. High Alt Med Biol. 00:000-000, 2024. Introduction: Exposure to high altitude results in hypobaric hypoxia with physiological acclimatization changes that are thought to influence athletic performance. This review summarizes existing literature regarding implications of high-altitude training and altitude-related guidelines from major governing bodies of sports. Methods: A nonsystematic review was performed using PubMed and OVID Medline to identify articles regarding altitude training and guidelines from international governing bodies of various sports. Sports inherently involving training or competing at high altitude were excluded. Results: Important physiological compensatory mechanisms to high-altitude environments include elevations in blood pressure, heart rate, red blood cell mass, tidal volume, and respiratory rate. These responses can have varying effects on athletic performance. Governing sport bodies have limited and differing regulations for training and competition at high altitudes with recommended acclimatization periods ranging from 3 days to 3 weeks. Discussion: Physiological changes in response to high terrestrial altitude exposure can have substantial impacts on athletic performance. Major sport governing bodies have limited regulations and recommendations regarding altitude training and competition. Existing guidelines are variable and lack substantial evidence to support recommendations. Additional studies are needed to clarify the implications of high-altitude exposure on athletic ability to optimize training and competition.

Gardner, Laurel, Linda E. Keyes, Caleb Phillips, Elan Small, Tejaswi Adhikari, Nathan Barott, Ken Zafren, Rony Maharjan, and James Marvel. Women at altitude: Menstrual-cycle phase, menopause, and exogenous progesterone are not associated with acute mountain sickness. High Alt Med Biol. 00:000-000, 2024. Background: Elevated progesterone levels in women may protect against acute mountain sickness (AMS). The impact of hormonal contraception (HC) on AMS is unknown. We examined the effect of natural and exogenous progesterone on the occurrence of AMS. Methods: We conducted a prospective observational convenience study of female trekkers in Lobuche (4,940 m) and Manang (3,519 m). We collected data on last menstrual period, use of exogenous hormones, and development of AMS. Results: There were 1,161 trekkers who met inclusion criteria, of whom 307 (26%) had AMS. There was no significant difference in occurrence of AMS between women in the follicular (28%) and the luteal (25%) phases of menstruation (p = 0.48). The proportion of premenopausal (25%) versus postmenopausal women (30%) with AMS did not differ (p = 0.33). The use of HC did not influence the occurrence of AMS (HC 23% vs. no HC 26%, p = 0.47), nor did hormonal replacement therapy (HRT) (HRT 11% vs. no HRT 31%, p = 0.13). Conclusion: We found no relationship between menstrual-cycle phase, menopausal status, or use of exogenous progesterone and the occurrence of AMS in trekkers and conclude that hormonal status is not a risk factor for AMS. Furthermore, women should not be excluded from future AMS studies based on hormonal status.

Norberto, Matheus S., João Victor G. Torini, Matheus S. Firmino, and Marcelo Papoti. Validation of air storage system for hypoxia exposure during exercise. High Alt Med Biol. 00:000-000, 2024.-Considering the importance of optimizing normobaric hypoxia exposure (i.e., higher delivery capacity), the current study aims to validate a hypoxic air storage system. The study has a cross-over, one-blind randomized design. The air storage is composed of a piping system that directs hypoxic air from a hypoxia generator into nylon bags. Sixteen men (age, 25.4 ± 4.8 years; height, 174.9 ± 9.4 cm; weight, 77.1 ± 17.2 kg) performed three incremental treadmill tests until exhaustion on different days. For test-retest, the subjects repeated two tests in similar hypoxia conditions (H1 and H2; fraction of inspired O₂ [F_IO₂] = ∼0.13; reliability analysis), and one time in normoxia (F_IO₂ = ∼0.20; condition comparison). Subjects' performance, blood lactate concentration ([La^-]), arterial oxygen saturation (SpO₂), oxygen consumption (VO₂), heart rate (HR), and several respiratory-derived variables were evaluated. A comparison was made between the rest, moderate intensity, and exhaustion stages. All variables were compared using the Friedman test with Durbin-Conover post hoc (p < 0.05). The hypoxia test-retest showed no statistical differences for any variable. Time analysis showed similar behavior for SpO₂, HR, and cardiorespiratory variables (p < 0.01) for both conditions. The mean F_IO₂ at rest and during the incremental treadmill test was higher for normoxia (20.6 ± 0.2%) than for H1 (13.8 ± 0.8%) and H2 (13.7 ± 0.3%) (p < 0.001). The VO₂ response was higher in normoxia than during hypoxia exposure at moderate intensity (Normoxia = 43.1 ± 8.1; H1 = 38.7 ± 5.7; H2 = 35.8 ± 8.8 ml.kg^-1.min^-1) and at the exhaustion stage (Normoxia = 52.7 ± 12.5; H1 = 41.9 ± 8.8; H2 = 40.5 ± 8.9 ml.kg^-1.min^-1) (p < 0.01). SpO₂ and HR showed excellent intraclass correlation coefficient (ICC) during all moments, whereas VO₂, SpO₂, ratio between ventilation and CO₂ production (V_E/V_CO2), ratio between oxygen consumption and ventilation (V_E/V_O2), and HR showed moderate or good ICC and coefficient of variation <9% during hypoxia test-retest exercises. Thus, the air storage system showed validity for its application and reliability in the measurements associated.

Lin, Tian, Huaping Jia, Yunming Li, Yongxing Xu, Bei Zhao, Dong Zheng, Hongfeng Yan, Meihui Zhao, Yanlei Li, Liping Xia, Fengxia Zhou, Cuiping Liu, Ke Ma, Ma Mi, and Jianwen Gu. Epidemiological survey of congenital heart disease among children aged from 2 to 18 in Suo County, Nagqu, Tibet. High Alt Med Biol. 00:000-000, 2024. Background: Studies have reported the prevalence of congenital heart disease (CHD) in parts of Tibet, but relative epidemiological surveys are rare. We aimed to explore the prevalence of CHD in children and its relationship with family history in Suo County, Nagqu, Tibet, an altitude of 3,980 meters. Methods: We recruited 4,002 children aged 2-18 years. Subjects underwent a family history investigation, cardiac auscultation, and clinical manifestation examination and then received echocardiographic screening. Results: The prevalence of CHD among children in Suo County was 0.97% (39 cases), much higher than the prevalence at sea level. The most common subtype was atrial septal defect, accounting for 53.9% of CHD, followed by patent ductus arteriosus (33.3%) and ventricular septal defect (12.8%). We also found that children whose mothers had previously borne children with CHD had a higher risk of CHD than those without (p = 0.002); other factors related to CHD during pregnancy, such as smoking, drinking, drug use, and viral infection, showed no statistical differences between children with and without CHD. Conclusions: The prevalence of CHD in children in Suo County is much higher than at low altitude, consisting mostly of simple forms with left-to-right shunt, with rare complex CHD. These results support implementing diagnostic and treatment plans to prevent CHD in Suo County.

Horiuchi, Masahiro, Satomi Mitsui, and Tadashi Uno. Influence of smoking and alcohol habits on symptoms of acute mountain sickness on Mount Fuji: a questionnaire survey-based pilot study. High Alt Med Biol 00:000-000, 2024. Background: Acute cigarette smoking or alcohol intake would cause opposing vasculature effects that may influence acute mountain sickness (AMS). The present study aimed to investigate the effects of smoking and alcohol consumption behaviors, and acute smoking and consuming alcohol during ascent on AMS on Mount Fuji. Methods: This questionnaire survey study included 887 participants who climbed Mount Fuji and obtained information regarding sex, age, and smoking and alcohol habits, including behavior during ascent. Results: AMS prevalence was 45% for all participants. A univariate analysis revealed that younger participants (20-29 years) were associated with increased AMS prevalence (effect size [ES] = 0.102, p = 0.057) and severity (ES = 0.18, p = 0.01). A prediction model using multiple logistic regression indicated that several factors influenced AMS risk: younger age (p = 0.001), daily smoking habits (p = 0.021), no smoking (p = 0.033), or alcohol consumption during ascent (p = 0.096). Alcohol consumption during ascent had no effect on the increased AMS risk in younger participants (20-29 years), while alcohol consumption during ascent increased AMS risk for middle-age participants (50-59 years). Conclusion: Younger individuals are more likely to experience AMS. Smoking habits are associated with an increased AMS risk. It may be recommended that middle-aged climbers should ascend without consuming alcohol.

Wang, Si-Yang, Jun Liang, and Jing-Hong Zhao. A Case of High-Altitude Renal Syndrome. High Alt Med Biol. 00:000-000, 2024.-Epidemiological studies have confirmed that high-altitude exposure increases the risk of proteinuria. The concept of high-altitude renal syndrome (HARS) was proposed in 2011. HARS is a group of clinical syndromes consisting of high-altitude polycythemia, hyperuricemia, systemic hypertension, and microalbuminuria. At present, no standardized and unified treatment methods of HARS have been proposed. We report a case of HARS without other organ involvement in a young man exposed to high altitude. Decreasing the red blood cell count and hemodynamic changes as soon as possible may be of great importance for reducing proteinuria. In addition, angiotensin receptor blockers are effective in the treatment of HARS.

Poudel, Sangeeta, Sandesh Gautam, Purushottam Adhikari, and Ken Zafren. Physiological effects of sildenafil versus placebo at high altitude: a systematic review. High Alt Med Biol. 25:16-25, 2024. Introduction: High altitude pulmonary edema (HAPE), a life-threatening condition that affects individuals ascending to high altitude, requires the development of pulmonary hypertension. Sildenafil can be used to prevent and treat HAPE, presumably by decreasing pulmonary artery pressure (PaP). We compared the physiological effects of sildenafil versus placebo at high altitude (above 2,500 m), including the effects on PaP. Methods: We performed a systematic search of PubMed, EMBASE, and Cochrane CENTRAL for randomized controlled studies of the physiological effects of sildenafil in hypoxia in healthy individuals. We conducted a systematic review of all studies meeting our criteria. Results: Of the 14 studies that met the inclusion criteria, 8 were hypobaric hypoxia studies. Six studies reported data at rest at altitudes from 3,650 to 5,245 m. Two were simulations reporting exercise data at equivalent altitudes of 2,750-5,000 m. Nine studies used normobaric hypoxia corresponding to altitudes between 2,500 and 6,400 m. One reported only rest data, two reported rest and exercise data, and the others reported only exercise data. Sildenafil significantly reduced PaP at rest and exercise in hypobaric or normobaric hypoxia. There were no significant differences between arterial oxygen saturation (SpO₂) with sildenafil in hypobaric or normobaric hypoxia at rest or exercise. There were no significant differences in heart rate or mean arterial pressure (MAP) at rest or exercise and cardiac output during exercise in hypobaric or normobaric hypoxia. Conclusions: Sildenafil significantly reduces PaP at rest and exercise in normobaric or hypobaric hypoxia. Sildenafil has no significant effects on SpO₂, heart rate, cardiac output (during exercise), or MAP at rest or exercise in hypobaric or normobaric hypoxia.