Effect of nitrate supplementation on oxygen saturation levels for acute mountain sickness prevention: A systematic review and meta-analysis.

PURPOSE: This study aimed to systematically review the effect of nitrate supplementation on blood oxygen saturation. METHODS: We searched PubMed, Scopus, and Cochrane Library databases from their inception up to October 2022. Two reviewers independently conducted two stages of the screening process to include a randomized controlled trial with nitrate supplementation versus placebo intervention assessing oxygen saturation among lowlanders going to either real or simulated high altitude environments. We used the Cochrane Risk of Bias 2.0 tool to assess the risk of bias in the included studies. Fixed-effect model meta-analyses were conducted for laboratory-based studies. Random-effect meta-analyses were conducted for real-world studies. RESULTS: We found 7 trials that met the eligibility criteria. A meta-analysis of studies with some bias concerns showed an increase of 1.26 % in the SpO2 with 44 % I2 during submaximal exercise at simulated high altitudes (GRADE: low). On the contrary, a meta-analysis of studies without heterogeneity showed that nitrate supplementation aggravated oxygen saturation decline (-2.64 %, p = 0.03, GRADE: high) during rest in real high-altitude environments. A meta-analysis also showed that nitrate supplementation did not affect Acute Mountain Sickness (AMS) symptoms (GRADE: high). CONCLUSION: Our results suggest that nitrate supplementation did not provide benefits for AMS prevention during rest at high altitudes. The low-quality evidence showing small beneficial effects of nitrate supplementation during exercise calls for further studies.

Contributions of Griffith Pugh to Success on Mt. Everest and His Impact on the Advancement of Altitude and Environmental Physiology.

Griffith Pugh, MD (1909-1994), was a pioneer in altitude physiology. During World War II, he developed training protocols in Lebanon to improve soldier performance at altitude and in the cold. In 1951 he was chosen to join the British Everest team as a scientist. In preparation, he developed strategies for success on a training expedition on Cho Oyu in 1952. Results from Cho Oyu led to the use of supplemental oxygen at higher flow rates during ascent than used previously (4 L/min vs 2 L/min) and continued use (at a reduced rate of 2 L/min) during descent, enabling increased performance and improved mental acuity. Oxygen was also used during sleep, leading to improved sleep and warmth. Adequate hydration (∼3 L/day) was also stressed, and a more appealing diet led to improved nutrition and condition of the climbers. Improved hygiene practices and acclimatization protocols were also developed. These strategies contributed to the first successful summiting of Mount Everest in 1953. Pugh was then appointed as the lead scientist for a ground-breaking eight-and-a-half-month research expedition where the team was the first to overwinter at high altitude (5800 m) in the Himalayas. This current work summarizes Pugh's scientific contributions as they relate to success on Mount Everest and in inspiring future altitude research by generations of successful researchers.

Continuous Positive Airway Pressure in the Treatment of Pediatric High Altitude Pulmonary Edema: A Case Study.

Treatment of high altitude pulmonary edema (HAPE) can be challenging and is further complicated in the pediatric patient in the prehospital environment. The following case presents a decompensating pediatric patient with HAPE in the prehospital aeromedical environment. It illustrates the potential benefit of continuous positive airway pressure (CPAP) as a treatment modality in the treatment of HAPE.

Possibility for Children with Medical Complexities to Reach a 3000-m Peak: A Report of 2 Cases.

With the recent development of neonatal medicine, the number of children with medical complexities (CMCs) is increasing. Outdoor activities are important for their psychosocial development, and the principles of accessibility should be addressed. We report the experience of 2 CMCs' high-altitude mountaineering with the necessary support. The participants were a 3-y-old girl with cerebral palsy, symptomatic epilepsy, and a ventriculoperitoneal shunt (Child A) and a 6-y-old girl who underwent bilateral Glenn operations at 11 mo for hypoplastic left heart syndrome (Child B). The support staff consisted of 4 doctors, 1 nurse, 5 nonmedical staff , 3 members from a mountaineering association, and 2 people from an oxygen company. The climbing schedule was 2 days. On the first day, we took a bus to a hut at an altitude of 2450 m and stayed overnight to acclimatize to the altitude. On the second day, we took the beginner's route, which took 3 h to climb 500 m, and our team made an attempt on the summit. During the attempt, Child B panicked. Although her lung sounds did not raise suspicions of pulmonary edema, we decided to leave the mountain with her because her transcutaneous oxygen saturation decreased. Child A had no apparent health problems and made it to the summit. Although CMCs' alpine climbing requires careful planning and staffing considering the risk of high-altitude sickness, our case suggests the feasibility of such activities with CMCs as part of accessibility.

A Randomized Phase 2 Study to Evaluate Efficacy and Safety of AR36 for Prevention of Acute Mountain Sickness.

INTRODUCTION: AR36 is a pharmaceutical-grade plant extract used to support cardiovascular health in traditional Chinese medicine. Studies suggest that AR36 may prevent acute mountain sickness (AMS) during gradual ascent to high altitude. This randomized, placebo-controlled Phase 2 trial aimed to evaluate dosing regimens and assess efficacy and safety of AR36 for AMS prevention during rapid ascent. METHODS: Participants received placebo, low-dose AR36 (225 mg twice daily for 14 d prior and 5 d at altitude), or high-dose AR36 (12 d placebo, 300 mg twice daily for 2 d prior and 5 d at altitude). The primary efficacy outcome was 1993 Lake Louise Scoring System (LLSS) score on the morning after ascent. Safety was assessed through the proportion of treatment-emergent adverse events (TEAEs). RESULTS: One hundred thirty-two participants were randomized. Mean±SD age was 31.4±8.6 (range, 19-54) y. Baseline characteristics did not differ across groups. Lake Louise Scoring System scores on Day 16 in the placebo, low-dose, and high-dose groups were 4.03 (2.88), 4.42 (3.17), and 3.5 (2.31), respectively (placebo versus low-dose, P=0.462; placebo versus high-dose, P=0.574; n=110). The incidence of AMS on Day 16 was 66.7% in the placebo, 61.1% in the low-dose, and 55.3% in the high-dose group (P=0.66). The proportion of TEAEs in the placebo, low-dose, and high-dose groups was 38.4% (81), 28.4% (60), and 33.2% (70), respectively (P=0.205; n=127). There was no statistical difference between groups in LLSS, incidence of AMS, or TEAEs. CONCLUSIONS: AR36 did not improve LLSS or AMS incidence using the current regimens. AR36 was well tolerated.

[Establishment and Evaluation of a Mice Model of High-Altitude Cerebral Edema]. / é«˜åŽŸè„‘æ°´è‚¿å°é¼ æ¨¡åž‹çš„å»ºç«‹ä¸Žé‰´å®š.

Objective: To establish an animal model of high-altitude cerebral edema (HACE), to explore the altitude and oxygen partial pressure conditions that can lead to obvious clinical manifestations of HACE, and to lay the foundation for further research of the pathogenic mechanisms and intervention strategies of HACE. Methods: Male BALB/c mice of 8 weeks old were randomly assigned to Control and HACE groups. The Control group (n=10) was treated with normobaric and normoxic conditions, while the HACE groups were placed in hypobaric hypoxic (HH) chambers for the durations of 6 h, 12 h, 24 h, 48 h and 72 h, respectively, receiving treatments of simulated HH conditions at the altitudes of 4000 m (n=10 for each group receiving different durations of HH treatment), 5000 m (n=10 for each group receiving different durations of HH treatment), and 6000 m (n=10 for each group receiving different durations of HH treatment). HE staining was performed to observe the morphological changes of the brain tissue and the appropriate simulated altitude conditions were selected accordingly for the construction and evaluation of the best HACE model. The HACE model was evaluated in the following ways, the mouse brain was weighed and the cerebral edema was measured accordingly, Evans blue (EB) was injected to determine the permeability of the blood-brain barrier (BBB), and the cell apoptosis was determined by immunofluorescence staining. Results: There were no deaths in the groups treated with the HH conditions of the altitudes of 4000 m and 5000 m, while the mortality in the 6000 m altitude treatment groups was 12.2%. HE staining showed no significant changes in brain morphology or structure in the group receiving HH treatment for the altitude of 4000 m. A small amount of brain cell edema was observed in the groups receiving 48 h and 72 h of HH treatment for the altitude of 5000 m. The groups receiving HH treatment for the altitude of 6000 m demonstrated the most prominent modeling effect. HE staining showed increased volume and swelling of brain cells in all the 6000 m groups, especially in the 24 h, 48 h and 72 h treatment groups. In all the 6000 m groups, cell arrangement disorder, gap enlargement, and nuclear contraction were observed. Evaluation of the modeling effect demonstrated that, in the HACE mice model constructed with the HH conditions for the altitude of 6000 m, cerebral edema and EB permeability increased after 12 h HH treatment and there was no obvious apoptosis in the modeling groups receiving different durations of treatment. Conclusion: The HACE model can be established effectively by simulating conditions at the altitude of 6000 m (the atmospheric pressure being 47.19 kPa and the oxygen partial pressure being 9.73 kPa) with a HH chamber.

Point-of-Care Ultrasound Diagnosis of Community-Acquired Pneumonia in a High-Altitude, Resource-Poor Setting.

Objective: Point-of-care ultrasound (POCUS) for the evaluation of patients with suspected high-altitude pulmonary edema can be a useful tool in remote, high-altitude areas. The same technique can also yield high differential diagnostic accuracy for other relevant causes of acute respiratory distress at high altitude. With the recent development of high-quality, hand-held ultrasound devices, POCUS can be used with increasing reliability in such environments. We present a case of severe respiratory disease in a young, otherwise healthy patient during a trek at high altitude in the Khumbu valley of Nepal. Methods: By using POCUS, we were able to exclude several important differential diagnoses and diagnose the patient with community-acquired pneumonia. Results: Our findings allowed us to start early on-site treatment and positively influenced shared decision-making with the patient, which led to a helicopter evacuation. Conclusions: This case illustrates that POCUS can be a valuable tool in remote, high-altitude regions and could allow healthcare providers to diagnose and follow-up with patients exhibiting acute respiratory symptoms when other radiological imaging modalities are not available.

A Case of High Altitude Cerebral Edema With a Prolonged Motivational Deficit.

We report a case of prolonged motivational deficit as a sequela of high altitude cerebral edema (HACE), the most severe form of neuropsychiatric dysfunction arising from traveling to high altitude. Magnetic resonance imaging of the brain showed hyperintense lesions in the globi pallidi bilaterally on T2-weighted images. Single-photon emission computed tomography showed hypoperfusion in dorsolateral and orbital prefrontal cortices bilaterally and in the anterior cingulate cortex. This case suggests that a prolonged motivational deficit can occur in patients with HACE. The case may also suggest that HACE can cause network disturbances between the prefrontal cortex and the globi pallidi.

Evaluation of High Altitude Interstitial Pulmonary Edema in Healthy Participants Using Rapid 4-View Lung Ultrasound Protocol During Staged Ascent to Everest Base Camp.

INTRODUCTION: Prior research identified possible interstitial pulmonary fluid, concerning for early high altitude pulmonary edema (HAPE), in a large percentage of trekkers above 3000 m using a comprehensive 28-view pulmonary ultrasound protocol. These trekkers had no clinical symptoms of HAPE despite these ultrasound findings. The more common 4-view lung ultrasound protocol (LUP) is accurate in rapidly detecting interstitial edema during resource-rich care. The objective of this study was to evaluate whether the 4-view LUP detects interstitial fluid in trekkers ascending to Everest Base Camp. METHODS: Serial 4-view LUP was performed on 15 healthy trekkers during a 9-d ascent from Kathmandu to Everest Base Camp. Ascent protocols complied with Wilderness Medical Society guidelines for staged ascent. A 4-view LUP was performed in accordance with the published 2012 international consensus protocols on lung ultrasound. Symptom assessment and 4-view LUP were obtained at 6 waypoints along the staged ascent. A 4-view LUP was positive for interstitial edema if ≥3 B-lines were detected in 2 ultrasound windows. RESULTS: A single participant had evidence of interstitial lung fluid at 5380 m as defined by the 4-view LUP. There was no evidence of interstitial fluid in any participant below 5380 m. One participant was evacuated for acute altitude sickness at 4000 m but showed no preceding sonographic evidence of interstitial fluid. CONCLUSIONS: In this small study, sonographic detection of interstitial fluid, suggestive of early HAPE, was not identified by the 4-view LUP protocol.

Protective effects of active compounds from on heart and brain of mice at simulated high altitude.

To investigate the active compounds from on the heart and brain of mice at simulated high altitude.Fifty healthy male adult BALB/c mice were randomly divided into normal control group, hypoxic model group, acetazolamide group, petroleum ether extract of (PESI) group and octacosan group with 10 mice in each group. Acetazolamide group, PESI group and octacosan group were treated with acetazolamide PESI (200 mg/kg) or octacosan by single tail vein injection, respectively. Except normal control group, the mice were exposed to a simulated high altitude of for in an animal decompression chamber. After the mice were sacrificed by cervical dislocation, the heart and brain were histologically observed by HE staining; superoxide dismutase (SOD) activity, total anti-oxidant capacity (T-AOC) and the content of malondialdehyde (MDA) in plasma, heart and brain tissues were detected by WST-1 method, ABTS method and TBA method, respectively; lactic acid and lactate dehydrogenase (LDH) activity in plasma, heart and brain tissues were detected by colorimetric method and microwell plate method, respectively; ATP content and ATPase activity in heart and brain tissues were detected by colorimetric method. PESI and octacosane significantly attenuated the pathological damages of heart and brain tissue at simulated high altitude; increased SOD activity, T-AOC and LDH activity, and decreased the contents of MDA and lactic acid in plasma, heart and brain tissues; increased the content of ATP in heart and brain tissues; increased the activities of Na-K ATPase, Mg ATPase, Ca ATPase and Ca-Mg ATPase in myocardial tissue; and increased the activities of Mg ATPase, Ca-Mg ATPase in brain tissue. PESI and octacosan exert anti-hypoxic activity by improving the antioxidant capacity, reducing the free radical levels, promoting the anaerobic fermentation, and alleviating the energy deficiency and metabolic disorders caused by hypoxia in mice.

Influence of methazolamide on the human control of breathing: A comparison to acetazolamide.

NEW FINDINGS: What is the central question of this study? Acetazolamide and methazolamide both reduce hypoxic pulmonary vasoconstriction equally, but methazolamide does not impair skeletal muscle function. The effect of methazolamide on respiratory control in humans is not yet known. What is the main finding and its importance? Similar to acetazolamide after chronic oral administration, methazolamide causes a metabolic acidosis and shifts the ventilatory CO2 response curve leftwards without reducing O2 sensitivity. The change in ventilation over the change in log PO2 provides a more accurate measure of hypoxic sensitivity than the change in ventilation over the change in arterial oxyhaemoglobin saturation. ABSTRACT: Acetazolamide is used to prevent/treat acute mountain sickness and both central and obstructive sleep apnoea. Methazolamide, like acetazolamide, reduces hypoxic pulmonary vasoconstriction, but has fewer side-effects, including less impairment of skeletal muscle function. Given that the effects of methazolamide on respiratory control in humans are unknown, we compared the effects of oral methazolamide and acetazolamide on ventilatory control and determined the ventilation-log  PO2 relationship in humans. In a double-blind, placebo-controlled, randomized cross-over design, we studied the effects of acetazolamide (250 mg three times daily), methazolamide (100 mg twice daily) and placebo in 14 young male subjects who were exposed to 7 min of normoxic hypercapnia and to three levels of eucapnia and hypercapnic hypoxia. With placebo, methazolamide and acetazolamide, the CO2 sensitivities were 2.39 ± 1.29, 3.27 ± 1.82 and 2.62 ± 1.79 l min-1  mmHg-1 (n.s.) and estimated apnoeic thresholds 32 ± 3, 28 ± 3 and 26 ± 3 mmHg, respectively (P < 0.001, placebo versus methazolamide and acetazolamide). The relationship between ventilation ( V̇I ) and log  PO2 (using arterialized venous PO2 in hypoxia) was linear, and neither agent influenced the relationship between hypoxic sensitivity ( ΔV̇I/ΔlogPO2 ) and arterial [H+ ]. Using ΔV̇I/ΔlogPO2 rather than Δ V̇I /Δ arterial oxyhaemoglobin saturation enables a more accurate estimation of oxygenation and ventilatory control in metabolic acidosis/alkalosis when right- or leftward shifts of the oxyhaemoglobin saturation curve occur. Given that acetazolamide and methazolamide have similar effects on ventilatory control, methazolamide might be preferred for indications requiring the use of a carbonic anhydrase inhibitor, avoiding some of the negative side-effects of acetazolamide.

Physiological Variables Associated with the Development of Acute Mountain Sickness.

Objective To identify the physiological variables associated with the development of acute mountain sickness (AMS).Methods Eighty four young Chinese men residing at low altitude were taken to an altitude of 4000 m within 40 hours. At sea level and at high altitude, we measured the heart rate, blood pressure, and peripheral oxygen saturation (SpO2) respectively. We also collect blood samples from each participants before and after the altitude elevation. The blood routine and biochemical examinations were performed for all blood samples. The revised Lake Louise Criteria was adopted to diagnose AMS after the subjects arrived at the target high altitude. The association between the presence of AMS and subjects' physiological variables were analysed statistically.Results Of 84 participants, 34 (40.5%) developed AMS. Compared with non AMS group, in the AMS group, the percentage of neutrophils was significantly higher (64.5%±11.2% vs. 58.1%±8.8%, P =0.014), while the level of SpO2 was significantly lower (79.4%±5.4% vs. 82.7%±5.6, P=0.008). Binary logistic regression analyses emphasized the association of neutrophils (OR: 1.06, 95% CI: 1.01-1.12, P=0.034) and SpO2 level (OR: 0.87, 95% CI : 0.79-0.95, P=0.004) with the development of AMS.Conclusion The ability to sustain SpO2 after altitude elevation and the increase of neutrophils were associated with the development of AMS in young males.

Electrocardiographic changes during exercise in acute hypoxia and susceptibility to severe high-altitude illnesses.

BACKGROUND: The goals of this study were to compare ECG at moderate exercise in normoxia and hypoxia at the same heart rate, to provide evidence of independent predictors of hypoxia-induced ECG changes, and to evaluate ECG risk factors of severe high-altitude illness. METHODS AND RESULTS: A total of 456 subjects performed a 20-minute hypoxia exercise test with continuous recording of ECG and physiological measurements before a sojourn above 4000 m. Hypoxia did not induce any conduction disorder, arrhythmias, or change in QRS axis. The amplitude of the P wave in V1 was lower in hypoxia than in normoxia. The amplitudes of the R, S, and T waves and the Sokolow index decreased in hypoxia. Under hypoxia, the amplitude of the ST segment decreased in II and V6 and increased in V1, the ST slope rose in V5 and V6, and the J point was lower in II, V5, and V6. Multivariate regression of hypoxic/normoxic ratios of electrophysiological parameters and clinical characteristics showed a correlation between the decrease in Sokolow index and T-wave amplitude in V5 with desaturation at exercise. Trained status and low body mass index were associated with a smaller decrease in T-wave amplitude in V5 and V6. Comparison of ECG between subjects suffering or not suffering from severe high-altitude illness failed to show any difference. CONCLUSIONS: During a hypoxia exercise test, a dose-dependent hypoxia-induced decrease in the amplitude of the P/QRS/T waves was observed. No standard ECG characteristic predicted the risk of developing severe high-altitude illness. Further studies are required to clarify the cause of these electric changes and their potential predictive role in cardiac events.

Risk Determinants of Acute Mountain Sickness and Summit Success on a 6-Day Ascent of Mount Kilimanjaro (5895 m).

OBJECTIVE: The aims of this study were to assess incidence of acute mountain sickness (AMS) and summit success on a 6-day ascent profile of Mt. Kilimanjaro and evaluate potential risk factors for these outcomes. METHODS: All trekkers through a single Australian tour company between August 2012 and July 2014 were included. Participants ascended via the Rongai route and attempted the summit on day 6. Daily assessments were made using the self-reported Lake Louise score (LLS) questionnaire. Two different AMS diagnostic criteria (LLS ≥ 3 and LLS ≥ 5) were used for data analysis. Risk factors for development of AMS and summit success were analyzed. RESULTS: Over the 24-month period a total of 175 participants undertook the trek. Incidence of AMS was 52.6% (LLS ≥ 3) and 22.9% (LLS ≥ 5). Summit success was 88%. Age, sex, body mass index, and acetazolamide use were not associated with risk of AMS development. Age ≥ 40 years (P = .0002) and female sex (P = .0004) were both significantly associated with reduced summit success rate. CONCLUSIONS: Our cohort found a lower incidence of AMS and better summit success on a 6-day ascent of Mt Kilimanjaro than previously described in other groups on 4- and 5-day ascents. Female sex and age ≥ 40 years both predicted failure to summit, but did not increase risk of developing AMS. AMS is a common cause of morbidity on Mt. Kilimanjaro, and although the risk can be mitigated by a slower ascent, there is an ongoing need for education of individual trekkers, tour companies, and local authorities.

Myopic Changes in a Climber after Taking Acetazolamide and the Use of Corrective Lenses to Temporize Symptoms: A Case Report from Mount Kilimanjaro.

When performing detailed tasks related to climbing or hiking, accurate vision is important for safety. Acetazolamide is a medication commonly used to prevent acute mountain sickness, but it has an uncommon side effect of transient myopia. Reports of this side effect are mainly associated with its use in obstetrics, where it is often prescribed in higher doses than used in acute mountain sickness prophylaxis. We describe the case of a climber taking low-dose acetazolamide who developed transient myopia. We further describe potential mechanisms of this rare side effect as well as a novel approach of field management utilizing possible materials at hand.

Acute Mountain Sickness (AMS) Knowledge Among High Altitude Marathon Runners Competing in the Everest Marathon.

OBJECTIVE: Although there are a number of studies on trekkers' knowledge of acute mountain sickness (AMS), there is little current literature on other groups at altitude, for example, marathon runners. Increased knowledge of AMS is associated with a lower incidence of AMS. The purpose of this study was to determine AMS knowledge of marathon runners with an aim to improve AMS information distribution. Incidence of AMS was also determined. METHODS: Participants completed a self-assessment AMS knowledge questionnaire in Kathmandu before starting the acclimatization trek for the Tenzing Hillary Everest Marathon in Nepal. Lake Louise Scoring questionnaires were completed every day of the 12-day acclimatization trek. RESULTS: The majority (86%; 43 of 50) of participants obtained information about AMS before the marathon, with the Internet providing the most common source (50%; 25 of 50). Ninety-two percent (46 of 50) of participants rated their knowledge as average or above, and self-assessment correlated with knowledge questionnaire scores (r = .479, P < .001). However, 48% (24 of 50) did not know it was unsafe to ascend with mild AMS symptoms, and 66% (33 of 50) thought it was safe to go higher with symptoms relieved by medication. Only 50% (25 of 50) knew AMS could occur from 2500 m. Thirty-eight percent (19 of 50) of participants had AMS during the acclimatization trek, and 6% (3 of 50) experienced it during the race. CONCLUSIONS: This study adds to previous literature regarding knowledge and incidence of AMS. It further highlights that more needs to be done to improve knowledge through better information dissemination, with inclusion of scenario-based information to aid application of this knowledge to practical situations.

The 6-Minute Walk Test as a Predictor of Summit Success on Denali.

OBJECTIVE: To test whether the 6-minute walk test (6MWT), including postexercise vital sign measurements and distance walked, predicts summit success on Denali, AK. METHODS: This was a prospective observational study of healthy volunteers between the ages of 18 and 65 years who had been at 4267 m for less than 24 hours on Denali. Physiologic measurements were made after the 6MWT. Subjects then attempted to summit at their own pace and, at the time of descent, completed a Lake Louise Acute Mountain Sickness Questionnaire and reported maximum elevation reached. RESULTS: One hundred twenty-one participants enrolled in the study. Data were collected on 111 subjects (92% response rate), of whom 60% summited. On univariate analysis, there was no association between any postexercise vital sign and summit success. Specifically, there was no significant difference in the mean postexercise peripheral oxygen saturation (Spo2) between summiters (75%) and nonsummiters (74%; 95% CI, -3 to 1; P = .37). The distance a subject walked in 6 minutes (6MWTD) was longer in summiters (617 m) compared with nonsummiters (560 m; 95% CI, 7.6 to 106; P = .02). However, this significance was not maintained on a multivariate analysis performed to control for age, sex, and guide status (P = .08), leading to the conclusion that 6MWTD was not a robust predictor of summit success. CONCLUSIONS: This study did not show a correlation between postexercise oxygen saturation or 6MWTD and summit success on Denali.

Primary Care in Extreme Environments: Medical Clinic Utilization at Antarctic Stations, 2013-2014.

OBJECTIVES: The unique challenges posed by the Antarctic environment include both physiological and psychological stressors to the individual as well as the limited onsite medical capabilities available to address them. This report compares medical clinic utilization among 3 US Antarctic stations to identify differences in diagnostic frequency and utilization of clinic resources under current medical prescreening regimes for summer and winter seasons. METHODS: Clinic data from 3 Antarctic locations (McMurdo Station, Amundsen-Scott South Pole Station, and Palmer Station) for the 2013-2014 Antarctic year were reviewed for patient encounter frequency by season, and provider-assigned visit diagnostic category. Differences between relative diagnosis frequencies among stations were analyzed, and per-capita clinic utilization was compared. RESULTS: The McMurdo clinic recorded 1555 patient encounters, with South Pole Station reporting 744 and Palmer with 128 encounters over the year. The most frequent reasons for clinic visits were orthopedic and dermatologic, with increased visits at McMurdo for respiratory illness and at the more remote locations for neurologic complaints and insomnia. Altitude-related visits were reported only at McMurdo and South Pole stations. CONCLUSIONS: The clinic volume predictably correlated with station population. Insomnia and headache complaints, reported only at the South Pole Station, are likely associated with the increased elevation at that site, although they could be attributable to psychological stress from the isolated environment. Although the majority of cases could not be prevented with current screening, we suggest several changes to the current concept of operations that may decrease medical utilization and provide significant improvements to health care delivery on the ice.

Subtle Cognitive Dysfunction in Resolving High Altitude Cerebral Edema Revealed by a Clock Drawing Test.

High altitude cerebral edema (HACE) is a life-threatening condition that can affect people who ascend to altitudes above 2500 m. Altered mental status and the presence of ataxia distinguishes HACE from acute mountain sickness (AMS). We describe a patient with subtle cognitive dysfunction, likely due to HACE that had not fully resolved. When he initially presented, the patient appeared to have normal mental status and was not ataxic. The diagnosis of HACE was missed initially but was made when further history became available. Cognitive dysfunction was then diagnosed based on abnormal performance of a clock drawing test. A formal mental status examination, using a clock drawing test, may be helpful in assessing whether a patient at high altitude with apparently normal mental status and with normal gait has HACE.

Inhaled budesonide prevents acute mountain sickness in young Chinese men.

BACKGROUND: Oral glucocorticoids can prevent acute mountain sickness (AMS). Whether inhaled budesonide (BUD) can prevent AMS remains unknown. OBJECTIVE: Our aim was to investigate the effectiveness of BUD in AMS prevention. METHODS: Eighty subjects were randomly assigned to receive budesonide (BUD, inhaled), procaterol tablet (PT), budesonide/formoterol (BUD/FM, inhaled), or placebo tablet (n = 20 in each group). Subjects were treated for 3 days before ascending from 500 m to 3700 m within 2.5 h by air. Lake Louis AMS questionnaire, blood pressure, heart rate, and oxygen saturation (SpO2) were examined at 20, 72, and 120 h after high-altitude exposure. Pulmonary function was measured at 20 h after exposure. RESULTS: Compared with placebo, BUD significantly reduced the incidence of AMS (70% vs. 25% at 20 h, p < 0.05; both 10% vs. 5% at 72 and 120 h, both p > 0.05) without side effects. The relative risk was 0.357, and the risk difference was 0.45. Mean SpO2 was higher in BUD, BUD/FM, and PT groups than in the placebo group at 20 h (p < 0.05). SpO2 in all 80 subjects dropped after ascent (98.1% to 88.12%, p < 0.01) and increased gradually, but it was still lower at 120 h than at baseline (92.04% vs. 98.1%, p < 0.01). Pulmonary function did not differ among the four groups at 20 h. CONCLUSION: BUD can prevent AMS without side effects. The alleviation of AMS may be related to increased blood oxygen levels rather than pulmonary function.