Sildenafil citrate for the prevention of high altitude hypoxic pulmonary hypertension: double blind, randomized, placebo-controlled trial

Exaggerated hypoxic pulmonary vasoconstriction is a key factor in the development of high altitude pulmonary edema (HAPE). Due to its effectiveness as a pulmonary vasodilator, sildenafil has been proposed as a prophylactic agent against HAPE. By conducting a parallel-group double blind, randomized, placebo-controlled trial, we investigated the effect of chronic sildenafil administration on pulmonary artery systolic pressure (PASP) and symptoms of acute mountain sickness (AMS) during acclimatization to high altitude. Sixty-two healthy lowland volunteers (36 male; median age 21 years, range 18 to 31) on the Apex 2 research expedition were flown to La Paz, Bolivia (3650?m), and after 4-5 days acclimatization ascended over 90?min to 5200?m. The treatment group (n=20) received 50?mg sildenafil citrate three times daily. PASP was recorded by echocardiography at sea level and within 6?h, 3 days, and 1 week at 5200?m. AMS was assessed daily using the Lake Louise Consensus symptom score. On intention-to-treat analysis, there was no significant difference in PASP at 5200?m between sildenafil and placebo groups. Median AMS score on Day 2 at 5200?m was significantly higher in the sildenafil group (placebo 4.0, sildenafil 6.5; p=0.004) but there was no difference in prevalence of AMS between groups. Sildenafil administration did not affect PASP in healthy lowland subjects at 5200?m but AMS was significantly more severe on Day 2 at 5200?m with sildenafil. Our data do not support routine prophylactic use of sildenafil to reduce PASP at high altitude in healthy subjects with no history of HAPE. TRIALS REGISTRATION NUMBER: NCT00627965.     

Prediction of acute mountain sickness by monitoring arterial oxygen saturation during ascent

Acute mountain sickness (AMS) is a common problem while ascending at high altitude. AMS may progress rapidly to fatal results if the acclimatization process fails or symptoms are neglected and the ascent continues. Extensively reduced arterial oxygen saturation at rest (R-Spo?) has been proposed as an indicator of inadequate acclimatization and impending AMS. We hypothesized that climbers less likely to develop AMS on further ascent would have higher Spo? immediately after exercise (Ex-Spo?) at high altitudes than their counterparts and that these postexercise measurements would provide additional value for resting measurements to plan safe ascent. The study was conducted during eight expeditions with 83 ascents. We measured R-Spo? and Ex-Spo? after moderate daily exercise [50?m walking, target heart rate (HR) 150?bpm] at altitudes of 2400 to 5300?m during ascent. The Lake Louise Questionnaire was used in the diagnosis of AMS. Ex-Spo? was lower at all altitudes among those climbers suffering from AMS during the expeditions than among those climbers who did not get AMS at any altitude during the expeditions. Reduced R-Spo? and Ex-Spo? measured at altitudes of 3500 and 4300?m seem to predict impending AMS at altitudes of 4300?m (p?相似文献   

Association between physiological responses after exercise at low altitude and acute mountain sickness upon ascent is sex-dependent

Background:Acute mountain sickness (AMS) is the mildest form of acute altitude illnesses,and consists of nonspecific symptoms when unacclimatized persons ascend to elevation of ≥2500 m.Risk factors of AMS include:the altitude,individual susceptibility,ascending rate and degree of pre-acclimatization.In the current study,we examined whether physiological response at low altitude could predict the development of AMS.Methods:A total of 111 healthy adult healthy volunteers participated in this trial;and 99 (67 men and 32 women)completed the entire study protocol.Subjects were asked to complete a 9-min exercise program using a mechanically braked bicycle ergometer at low altitude (500m).Heart rate,blood pressure (BP) and pulse oxygen saturation (SpO2)were recorded prior to and during the last minute of exercise.The ascent from 500m to 4100m was completed in 2 days.AMS was defined as ≥3 points in a 4-item Lake Louise Score,with at least one point from headache wat 6-8 h after the ascent.Results:Among the 99 assessable subjects,47 (23 men and 24 women) developed AMS at 4100 m.In comparison to the subjects without AMS,those who developed AMS had lower proportion of men (48.9％ vs.84.6％,P＜0.001),height(168.4±5.9cm vs.171.3±6.1cm,P=0.019),weight (62.0±10.0kg vs.66.7±8.6kg,P=0.014) and proportion of smokers(23.4％ vs.51.9％,P=0.004).Multivariate regression analysis revealed the following independent risks for AMS:female sex (odds ratio (OR)=6.32,P＜0.001),SpO2 change upon exercise at low altitude (OR=0.63,P=0.002) and systolic BP change after the ascent (OR=0.96,P=0.029).Women had larger reduction in SpO2 after the ascent,higher AMS percentage and absolute AMS score.Larger reduction of SpO2 after exercise was associated with both AMS incidence(P=0.001) and AMS score (P＜0.001) in men but not in women.Conclusions:Larger SpO2 reduction after exercise at low altitude was an independent risk for AMS upon ascent.Such an association was more robust in men than in women.Trial registration:Chinese Clinical Trial Registration,ChiCTR1900025728.Registered 6 September 2019.     

Acute mountain sickness; prophylactic benefits of antioxidant vitamin supplementation at high altitude

Acute mountain sickness; prophylactic benefits of Free-radical-mediated damage to the blood-brain barrier may be implicated in the pathophysiology of acute mountain sickness (AMS). To indirectly examine this, we conducted a randomized double-blind placebo-controlled trial to assess the potentially prophylactic benefits of enteral antioxidant vitamin supplementation during ascent to high altitude. Eighteen subjects aged 35 +/- 10 years old were randomly assigned double-blind to either an antioxidant (n = 9) or placebo group (n = 9). The antioxidant group ingested 4 capsules/day(-1) (2 after breakfast/2 after evening meal) that each contained 250 mg of L-ascorbic acid, 100 IU of dl-a-tocopherol acetate and 150 mg of alpha-lipoic acid. The placebo group ingested 4 capsules of identical external appearance, taste, and smell. Supplementation was enforced for 3 weeks at sea level and during a 10-day ascent to Mt. Everest base camp (approximately 5,180 m). Antioxidant supplementation resulted in a comparatively lower Lake Louise AMS score at high altitude relative to the placebo group (2.8 +/- 0.8 points versus 4.0 +/- 0.4 points, P = 0.036), higher resting arterial oxygen saturation (89 +/- 5% versus 85 +/- 5%, P = 0.042), and total caloric intake (13.2 +/- 0.6 MJ/day(-1) versus 10.1 +/- 0.7 MJ/day(-1), P = 0.001); the latter is attributable to a lower satiety rating following a standardized meal. These findings indicate that the exogenous provision of water and lipid-soluble antioxidant vitamins at the prescribed doses is an apparently safe and potentially effective intervention that can attenuate AMS and improve the physiological profile of mountaineers at high altitude.     

黄芩苷与红景天胶囊对急性高原病预防作用比较

 目的 探讨黄芩苷胶囊对急性高原病(acute mountain sickness, AMS)的预防作用。方法 采用随机对照的研究方法, 80名急进高原健康男性青年随机分为3组, 黄芩苷组(n=32)、红景天组(n=24)和安慰剂组(n=24)。3组在进入高原前2 d、进入高原后连续3 d分别服用黄芩苷胶囊(0.5 g, 2次/d)、红景天胶囊(0.76 g, 2次/d)和安慰剂(2粒, 2次/d)。检测急进高原前(海拔397 m)和急进高原后(3658 m)受试者氧饱和度、心率、收缩压、舒张压, 彩色多普勒超声测量肺动脉收缩压(pulmonary artery systolic pressure, PASP)和平均肺动脉压(mean pulmonary arterial pressure, MPAP), 统计急进高原后各组的AMS发病率。结果 急进高原后安慰剂组、黄芩苷组和红景天组的AMS发病率分别为58.3%(14/24)、25.0%(8/32)和29.2%(7/24), 与安慰剂组比较, 黄芩苷组及红景天组AMS发病率明显降低, 差异有统计学意义(P<0.05)。与急进高原前比较, 各组受试者急进高原后心率、血压及肺动脉压均升高, 氧饱和度降低(P<0.05);与安慰剂组比较, 黄芩苷组血压及心率明显降低(P<0.05), 红景天组急进高原后氧饱和度升高、肺动脉压降低(P<0.05)。结论 黄芩苷组可能通过降低血压及心率预防AMS的发生, 红景天胶囊可能通过升高氧饱和度, 降低PASP、MPAP预防AMS的发生。     

Evaluation of the Balance Error Scoring System (BESS) in the diagnosis of acute mountain sickness at 4380 m

Ascent to altitude is associated with a decrease in balance; however, the effect of acute mountain sickness (AMS) status on balance is variable depending on the test used and the altitude at which the test is performed. Here, we report preliminary findings on the relationship between the balance error scoring system (BESS) and AMS at the 2010 Janai Purnima festival at Gosainkunda, Nepal (4380?m). All subjects (n=37) completed a shortened BESS test (mBESS) while a subset completed the full BESS test (n=27). Pulse oximetry was used to measure heart rate and oxygen saturation, and blood pressure was measured by sphygmomanometer. Balance test scores (BESS and mBESS) and physiological measurements were compared between groups with AMS (AMS?) and without AMS (AMS?). Receiver-operator characteristic (ROC) curves were used to compare the abilities of the BESS and mBESS tests to correctly identify the AMS status of subjects. The AMS? group had significantly higher Lake Louise scores than the AMS? group (mean=4.0 (standard deviation=1.3) vs. 0.3 (0.6), p<0.001). The AMS? group also scored significantly higher on both the mBESS (6.6 (3.5) vs. 2.7 (1.7) errors, p=0.018) and the BESS tests (19.2 (8.8) vs. 10.4 (6.0) errors, p=0.001) compared to the AMS? group, indicating inferior balance in the AMS? group. The area under the ROC curve was significantly greater for the BESS test (0.895) compared to the mBESS test (0.690, p=0.02), implying that the full BESS test more accurately identified a subject's AMS status. Additional studies are needed to determine if BESS could be a useful adjunct to the clinical diagnosis of AMS.     

Improvement in hypoxemia at 4600 meters of simulated altitude with carbohydrate ingestion.

BACKGROUND: Carbohydrate ingestion increases the relative production of carbon dioxide which results in an increase in ventilation in normal individuals. An increase in ventilation at altitude can result in improvement of altitude-induced hypoxemia. HYPOTHESIS: Carbohydrate ingestion will increase the arterial blood oxygen tension and oxyhemoglobin saturation during acute high altitude simulation. METHODS: There were 15 healthy volunteers, aged 18-33 yr, who were given a 4 kcal x kg(-1) oral carbohydrate beverage administered 2.5 h into an exposure to 15,000 ft (4600 m) of simulated altitude (5.5 h after the last meal). Altitude was simulated by having subjects breath a 12% oxygen/balance nitrogen mixture while remaining at sea level. Arterial blood gas samples were drawn at baseline and at regular intervals up to 210 min after carbohydrate ingestion. Subjects were evaluated for AMS by use of the Environmental Symptoms Questionnaire (ESQ) and a weighted average of cerebral symptom score (AMS-C). RESULTS: Baseline PaO2 increased significantly (p < 0.01) from 43.0 +/- 3.0 mmHg at 4600 m before carbohydrate ingestion to 46.8 +/- 6.2 mmHg at 60 min after carbohydrate ingestion. Arterial oxygen saturation rose significantly (p < 0.01) from a baseline of 79.5% +/- 5.1 to 83.8% +/- 6.42 at 60 min. CONCLUSIONS: Carbohydrate consumption significantly increased oxygen tension and oxyhemoglobin saturation in arterial blood of normal subjects during simulated altitude. Effects reached statistical significance across all subjects at 60 min. There was no significant difference in arterial oxygen levels or arterial oxygen saturation in subjects who developed AMS vs. those who did not develop AMS.     

Carbohydrate supplementation and exercise performance at high altitude: a randomized controlled trial

Acute carbohydrate supplementation decreases effort perception and increases endurance exercise capacity at sea level. It also improves laboratory-based endurance performance at altitude. However, the effect of chronic carbohydrate supplementation at altitude, when acclimatization may attenuate carbohydrate effects, achieved doses are lower and metabolic effects may be different, is unknown and was therefore focused on in the present study. Forty-one members of a 22-day high altitude expedition were randomized in a double-blind design to receive either placebo or carbohydrate supplementation. Diet was manipulated with commercially available energy drinks consumed ad libitum throughout the expedition. Participants performed a mountaineering time trial at 5192?m, completed submaximal incremental exercise step tests to assess cardiovascular parameters before, during, and after the expedition, and recorded spontaneous physical activity by accelerometer on rest days. Compared to placebo, compliant individuals of the carbohydrate-supplemented group received daily an additional 3.5±1.4?g carbohydrate·kg body mass(-1). Compliant individuals of the carbohydrate supplemented group reported 18% lower ratings of perceived exertion during the time trial at altitude, and completed it 17% faster than the placebo group (both p<0.05 by t-test). However, cardiovascular parameters obtained during submaximal exercise and spontaneous physical activity on rest days were similar between the two groups (all p>0.05 by analysis of variance). This study utilized testing protocols of specific relevance to high altitude sojourners, including the highest mountaineering time trial completed to date at altitude. Chronic carbohydrate supplementation reduced ratings of perceived exertion and improved physical performance, especially during prolonged and higher intensity exercise tasks.     

Pulse oximetry in the diagnosis of acute mountain sickness

Acute mountain sickness (AMS) is a common condition in individuals who travel to altitudes over 2000 m. While AMS is an important public health problem, no measurements can reliably support or predict the diagnosis with any degree of confidence. We therefore set out to study whether pulse oximetry data are associated with AMS. We studied 169 subjects who had recently arrived by foot at 3080 m. Subjects completed a demographic survey, which collected data on ascent profiles and AMS symptoms. Resting arterial oxygen saturation and pulse rate were then measured using finger pulse oximetry. Forty-six subjects (27%) had AMS, using the Lake Louise score. Only pulse rate was significantly associated with the presence of AMS (OR: 1.4; 95% CI, 1.1 to 1.9; p < 0.05, backwards stepwise logistical regression). A trend showed worse AMS diagnoses were associated with higher mean pulse rates (p < 0.05, ANOVA linear weighted analysis). While some previous studies have shown an association between decreased oxygen saturation and acute mountain sickness at altitude, our results did not demonstrate such an association. The utility of pulse oximetry remains limited in the diagnosis of AMS. We recommend further study to determine the possible utility of pulse rate in the diagnosis and prediction of AMS.     

Efficacy of low-dose acetazolamide (125 mg BID) for the prophylaxis of acute mountain sickness: a prospective,double-blind,randomized, placebo-controlled trial

The objective of this study was to determine the efficacy of low-dose acetazolamide (125 mg twice daily) for the prevention of acute mountain sickness (AMS). The design was a prospective, double-blind, randomized, placebo-controlled trial in the Mt. Everest region of Nepal between Pheriche (4243 m), the study enrollment site, and Lobuje (4937 m), the study endpoint. The participants were 197 healthy male and female trekkers of diverse background, and they were evaluated with the Lake Louise Acute Mountain Sickness Scoring System and pulse oximetry. The main outcome measures were incidence and severity of AMS as judged by the Lake Louise Questionnaire score at Lobuje. Of the 197 participants enrolled, 155 returned their data sheets at Lobuje. In the treatment group there was a statistically significant reduction in incidence of AMS (placebo group, 24.7%, 20 out of 81 subjects; acetazolamide group, 12.2%, 9 out of 74 subjects). Prophylaxis with acetazolamide conferred a 50.6% relative risk reduction, and the number needed to treat in order to prevent one instance of AMS was 8. Of those with AMS, 30% in the placebo group (6 of 20) versus 0% in the acetazolamide group (0 of 9) experienced a more severe degree of AMS as defined by a Lake Louise Questionnaire score of 5 or greater (p = 0.14). Secondary outcome measures associated with statistically significant findings favoring the treatment group included decrease in headache and a greater increase in final oxygen saturation at Lobuje. We concluded that acetazolamide 125 mg twice daily was effective in decreasing the incidence of AMS in this Himalayan trekking population.     

Hypoxic ventilatory response,ventilation, gas exchange,and fluid balance in acute mountain sickness

To examine whether sea-level hypoxic ventilatory responses (HVR) predict acute mountain sickness (AMS) and document temporal changes in ventilation, HVR, gas exchange, and fluid balance, we measured these parameters at low altitude (100 m) and daily during 3 days at high altitude (4559 m). At low altitude, there were no significant differences in rest or exercise isocapnic HVR, poikilocapnic HVR at rest, and hypercapnic ventilatory response between 12 subjects without significant AMS and 11 subjects who fell sick. No low altitude ventilatory responses correlated with AMS or fluid balance at high altitude. On day 1, isocapnic HVR was significantly lower in the AMS group [0.86 +/- 0.43 (SD) vs. 1.43 +/- 0.63 L/min/% Sa(O2), p < 0.05). AMS was associated with higher AaD(O2), lower Pa(O2), and Sa(O2), while Pa(CO2) was not different between subjects with and without AMS. Both groups showed equivalent reductions in urine volume, sodium output, and gain in body weight on day 1 while climbing to 4559 m, but on day 2 only subjects without AMS had diuresis, natriuresis, and weight loss. We conclude that (1) susceptibility to AMS, fluid balance, and ventilation at high altitude cannot be predicted by low altitude HVR testing and (2) that the failure to increase HVR on arrival at high altitude and impaired gas exchange, possibly due to interstitial edema, may account for the more severe hypoxemia in AMS.     

肺弥散量测定方法评估急进高原后高山反应

27名健康者从海拔2260m快速进入海拔4700m高原进行了肺CO弥散量的测定，显示肺CO弥散量与急性高山病有某种程度相关。反应组10例和对照组17例相比，肺CO弥散量均随海拔的增高而增加，增加的幅度反应明显小于对照组。因此，认为人体进入高原后肺CO弥散代偿能力不足是发生急性高山病重要原因之一，利用肺DL-CO量测定评估人体对高原的适应性可作为预测急性高山病发生的一项客观指标。     

Visual analogue scores in assessment of acute mountain sickness

Acute mountain sickness (AMS) is common on ascent to high altitude, with self assessment being the current method used to assess symptoms. The Lake Louise Self-Report Score (LLSRS) and the Environmental Symptoms Questionnaire (ESQ) are widely used and validated. A Visual Analogue Scale (VAS) may be used as a simpler alternative for AMS assessment. Our aims were to compare a VAS using lines of length 100 mm, for both individual symptoms of AMS and self-assessed overall AMS with both LLSRS and a shortened Environmental Symptoms Questionnaire (ESQc) on ascent to 4392 m. We set out to suggest a specific score as a cut off point for diagnosis of AMS when using the VAS. There were significant positive correlations (p<0.01), between VAS and both LLSRS and ESQc scores for overall AMS and a composite AMS score derived from the individual symptom scores at 4392 m. The sensitivity and specificity of the VAS were calculated as 0.67 and 0.98, respectively, when using the LLSRS as the standard test for comparison, and 0.91 and 0.96, respectively, when using the ESQc for comparison. The cut off point for diagnosis of AMS was calculated to be 22 mm or above when using a VAS for overall AMS or 15 mm or above when using the VAS composite score, when using LLSRS as the comparative test. Our results show significant correlations between the VAS and the LLSRS and ESQc, when assessing AMS at 4392 m. Our study suggests that a VAS could provide a simple alternative method of assessing AMS at high altitude.     

沙美特罗替卡松吸入剂预防急性高原反应的效果观察

目的：观察沙美特罗替卡松粉吸入荆预防急性高原反应的效果。方法：55名青年随机分为沙美特罗组（n=31）和安慰剂组（n=24），自海拔1400m历时4天进入5200m，第2天开始，沙美特罗组每天早晚各吸入沙美特罗替卡松粉一个剂量（沙美特罗50μg，丙酸氟替卡松100μg），连续7天；安慰荆组用同样方法吸入少量生理盐水。以军用卫生标准GJB1098-91《急性高原反应的诊断和处理原则》随访观察第2天、4天、7天急性高原反应的严重程度、SaO2和脉率。结果：进入海拔5200m第7天安慰剂组急性高原反应症状较沙美特罗组严重（P〈0．05），第2天、4天安慰剂组脉率较沙美特罗组减慢（P〈0．05），SaO2两组无显著性意义（P〉0．05）。随访期间沙美特罗组发生一例高原脑水肿，安慰剂组发生一例高原肺水肿。结论：沙美特罗替卡松粉吸入剂预防急性高原反应无确切效果。     

Statistical models of acute mountain sickness

Acute mountain sickness (AMS) is caused by exposure to altitudes exceeding 2500 m and often resolves by acclimatization without further ascent. Statistical models of AMS score and the probability of an AMS diagnosis were developed to allow the combination of dissimilar exposures for simultaneous analysis. The study population was 302 trekkers from a previous investigation who provided self-reported symptoms upon arrival at 3840 m during hikes through altitudes of 1500 to 6200 m. AMS score (Hackett scale) was estimated by linear regression and the probability of an AMS diagnosis (Lake Louise criteria) by logistic regression. AMS score or probability was significantly associated with exposure day and altitude. Increased altitude over the prior 3 days resulted in higher estimated AMS score or probability and decreased altitude in lower score or probability. The odds ratio (OR) of AMS was 3.6 if not on acetazolamide. Females appeared slightly more susceptible than males (1.5 OR). The approach offers the advantages of (1) improved statistical power by combining exposures, (2) insight into the dose-response relationship of altitude exposure and AMS risk, (3) quantitative tests for the significance of factors that might affect AMS susceptibility, and (4) practical tools to track individual climbers and plan operational ascents.     

Survey of acute mountain sickness on Mauna Kea

Although thousands of people ascend 4205 m to visit the summit of Mauna Kea each year, there has been no information on the rate of altitude illness triggered by such visits. Two surveys were used: one for tourists driving up to the summit and the other for summit astronomy workers staying at lodging facilities at intermediate altitude. The surveys included the standardized Lake Louise Self-report Acute Mountain Sickness (AMS) Questionnaire that, when scored, gave the Lake Louise Symptoms Score (LLSS). Thirty percent of surveyed day visitors and 69% of surveyed professional astronomy staff had AMS, defined as a LLSS score of 3 or greater, with headache. Nine participants reported "disorientation/confusion" or greater consciousness changes. A majority of astronomy professionals reported fatigue, disturbed sleep, reduced activity, and mental status changes. Few took any AMS medications. The incidence of AMS in visitors to Mauna Kea's summit warrants increased education and increased availability of supplemental oxygen at the summit. The absence of reported serious altitude illness in the community is probably due to the rapid descent available on Mauna Kea, with prompt reversibility of adverse effects.     

A potential role for free radical-mediated skeletal muscle soreness in the pathophysiology of acute mountain sickness

BACKGROUND: It has been suggested that free radicals may be implicated in the pathophysiology of acute mountain sickness (AMS) due to their ability to initiate and propagate cell membrane damage (3). Therefore, the present study was designed to: a) investigate the effects of an expedition to high altitude on metabolic indices of free radical-mediated oxidative stress and assess subsequent implications for skeletal/cardiac muscle damage; and b) determine whether these parameters were different in subjects who developed AMS after gradual ascent to 5100 m (base camp, BC) compared with those who remained healthy. METHODS: There were 19 male volunteers who were examined at rest and after a standardized maximal exercise test at sea level before and after an expedition (SL1/SL2) and during the first morning of arrival at BC. The trek to BC lasted 20+/-5 d. RESULTS: A mild increase in the Lake Louise AMS score was observed by the end of day 1 at BC (p < 0.05 vs. SL1/SL2). Four subjects developed AMS, which in one subject later progressed to high altitude pulmonary and cerebral edema. The serum concentration of lipid hydroperoxides (LH) increased markedly at rest and after maximal exercise at BC (p < 0.05 vs. SL1/SL2) whereas no changes were observed for plasma malondialdehyde (MDA). Resting serum total phosphocreatine kinase activity (CPK) and myoglobin also increased at BC (p < 0.05 vs. SL1/SL2) whereas cardiac troponin I (cTnI) remained stable. The resting pain threshold decreased and exercise-induced muscle soreness subsequently increased at BC (p < 0.05 vs. SL1/SL2). An association was observed between resting LH and myoglobin at BC (r = 0.45, p < 0.05) and the increase in LH was related to the increase in exercise-induced muscle soreness at BC (r = 0.96, p < 0.05). Further correlations were identified between the AMS score on day 1 at BC and: a) resting/exercise LH (r = 0.63, p < 0.05/r = 0.51, p < 0.05); and b) resting pain threshold at BC (r = -0.58, p < 0.05). Furthermore, subjects with AMS on day 1 at BC were characterized by a greater decrease in the resting pain threshold and greater increase in resting LH, CPK and myoglobin compared with subjects without AMS (p < 0.05). Headache, fatigue, insomnia and general apathy were the most frequently reported symptoms of AMS. CONCLUSIONS: Localized free radical-mediated vascular damage of the blood-brain barrier in addition to systemic tissue damage causing overt skeletal muscle soreness may have contributed to the pathophysiology of AMS, the latter through its indirect effects on other non-specific constitutional symptoms such as fatigue and insomnia causing a deterioration in physical performance.     

Oral contraceptives, exercise, and acute mountain sickness in women

BACKGROUND: Previous research has found that exercise exacerbated acute mountain sickness (AMS) in men. PURPOSE: The current study tested this relationship in women taking oral contraceptives. METHODS: We studied seven women at 428 mmHg for 10 h; once while at rest (R) and once while performing intermittent exercise (EX). RESULTS: AMS scores had a slight increase at 9 vs. 0 h at altitude in both trials (p < 0.05). Resting measurements of ventilation (VE), arterial oxygen saturation (SPO2), end tidal O2 (PETO2), and end tidal CO2 (PETCO2) were not different over time or between trials (p > 0.05). While fluid intake did not change, urine output increased during the 0-3 h period, regardless of trial, and returned to baseline values by the 6-9 h period (218 +/- 37 vs. 121 +/- 22 ml x h(-1); p < 0.05). During exercise, SPO2 significantly dropped compared with similar time points in R (73.1 +/- 1.1 vs. 85.7 +/- 1.8%; p < 0.05). Despite exercise-induced desaturation, the AMS scores were not significantly different between R and EX. CONCULSION: These results suggest that oral contraceptives may cause a compensation for the physiological responses to exercise critical for the development of AMS.     

Irregular nocturnal breathing patterns high altitude in subjects susceptible to high-altitude pulmonary edema (HAPE): a preliminary study

We studied nocturnal breathing patterns and symptoms of acute mountain sickness (AMS) during trekking in the Japanese Alps (altitude: 2,760-2,920 m) for 4 d in five subjects susceptible to high-altitude pulmonary edema (HAPE-S-S) and five control volunteers. Breathing patterns were evaluated with the impedance plethysmograph, and symptoms of AMS were evaluated by the environmental symptoms questionnaire-III score for AMS of cerebral type (AMS-C score). In both groups, the percentage of time with periodic breathing significantly increased at high altitude and the percentage in controls was significantly higher than in HAPE-S-S on the second night. In four HAPE-S-S, other disordered breathing patterns, termed "irregular breathing," were observed frequently by night at high altitude. Irregular breathing patterns were characterized by irregularly repeated oscillatory or nonoscillatory clusters of breaths with augmented tidal volume, followed by expiratory pause, apnea, or hypoventilation of various durations. All controls did not show significant changes in AMS-C score, but four HAPE-S-S showed the increase in AMS-C score on the next morning after frequent irregular nocturnal breathing. There was significant correlation between the percentage of time with irregular nocturnal breathing and AMS-C score on the next morning. These results suggest that HAPE-S-S are prone to irregular nocturnal breathing patterns at high altitude, which is associated with the development of AMS, but it was not possible to determine whether these abnormal breathing patterns are a cause or an effect of AMS.     

Ataxia in acute mountain sickness does not improve with short-term oxygen inhalation

Stability of stance declines at high altitude in subjects with and without acute mountain sickness (AMS), suggesting that postural ataxia might result from different hypoxia-related mechanisms than those causing the signs and symptoms of AMS. The aim of this study was to determine whether short-term oxygen inhalation improves stability of stance assessed by static posturography and/or the symptoms of AMS. Twenty male volunteers with cerebral AMS scores above 0.70 were investigated the first or second morning of their stay at an altitude of 4559 m. Posturographic parameters remained unchanged, whereas cerebral AMS scores decreased (p < 0.001) after inhalation of 3 L/min of oxygen for at least 10 min. We conclude that ataxia of stance assessed by posturography may result from different hypoxia-triggered mechanisms that need more time for recovery than those causing AMS.