The quality of sleep and periodic breathing in healthy subjects at an altitude of 3,200 m

The medical risks of travel and stay at high altitude are well known. Many more people travel for recreation to lower but still significant altitudes. To investigate the quality of sleep and sleep-related breathing disorders (SRBD) at that altitude we performed full polysomnography in nine young volunteers at lowland (760 m above sea level) on the first and sixth night after ascent to 3,200 m. There have been few studies on such populations. The subjects were nonsmoking healthy males aged 20.3 +/- 3.5 years with normal spirometry and arterial blood gas measurements performed at low altitude. Although there was no statistically significant difference in the duration of stages and sleep quality between low altitude night and both nights at high altitude as assessed by percent of sleep spent in stage 1, 2, 3+4 NREM, and REM sleep, total sleep time (TST), and sleep efficiency; the number of arousals and awakenings doubled at high altitude. There was no periodic breathing (PB) during sleep, except in isolated central events of SRBD, at low altitude. PB appeared at altitude mostly during NREM sleep and its intensity remained stable throughout the study period. Individual variations of PB intensity were high, ranging from 0.1 to 24% of TST. There were also some episodes of obstructive apnea and hypopnea during sleep at high altitude (p < 0.001). Mean SaO2 was lower during the study nights at high altitude when compared with low altitude. There were some signs of ventilatory acclimatization as shown by a higher mean SaO2 during the sixth compared with the first night at altitude (p < 0.001). We conclude that the sleep quality at the altitude of 3,200 m remains satisfactory when compared to low altitude. There is high individual variability in intensity of PB at that altitude.     

Physiologic response to moderate altitude exposure among infants and young children

Substantial numbers of children are exposed to moderate altitude while traveling to mountain resorts with their families. Although there has been extensive study of the adult physiologic response to altitude exposure, few studies of infants and young children exist. This investigation examines the acute physiologic responses to moderate altitude exposure among young children and the relationship of these responses to the development of acute mountain sickness (AMS). Children 3 to 36 months old participated in the prospective observational study, which included baseline measurements at 1610 m and measurements after a 24-h exposure to 3109 m. Measurements included pulse and respiratory rate, end-tidal CO(2), arterial oxygen saturation (pulse oximetry), cerebral tissue oxygenation (St(O2)) by near-infrared spectroscopy, middle cerebral artery resistive index by transcranial Doppler, lateral ventricle volumes (ultrasound), and clinical evaluation for the presence of acute mountain sickness (Children's Lake Louise Score). Twenty-four children (13 girls and 11 boys, age 14.5 +/- 10.2 months) participated. After acute exposure to 3109 m, these children showed an increase in respiratory rate from 45 +/- 13 to 51.9 +/- 15 breaths/min (p < 0.008), accompanied by a decrease of end-tidal CO(2) from 31 +/- 3 to 28 +/- 2 mm Hg (p < 0.001) and a reduction of arterial oxygen saturation from 95 +/- 2 to 91 +/- 2% (p < 0.001). St(O2) also decreased from 78 +/- 8 to 67 +/- 13% (p < 0.001), and this reduction appeared to be related to age (r = 0.58, p < 0.05), with lower saturations found in younger children. No evidence of increased intracranial pressure, as assessed by middle cerebral artery resistive index, was seen during ascent. Seven subjects developed symptoms of AMS; however, no relationship was found between the physiologic changes observed and the presence of symptoms. Ascent from 1610 to 3109 m resulted in tachypnea, relative hypoxia, hypocapnia, and a reduction in cerebral tissue oxygenation (St(O2)). The reduction in St(O2) appeared to be related to age, with infants appearing to be the most susceptible to cerebral tissue oxygen desaturation at high altitude. No relationship appears to exist between the presence of AMS and the physiologic measurements.     

Language used in Lake Louise Scoring System underestimates symptoms of acute mountain sickness in 4- to 11-year-old children

The Lake Louise Scoring System (LLSS) was designed to evaluate adults for symptoms of acute mountain sickness (AMS). The language used in the LLSS may be too complex for young children to comprehend. This study evaluates if age-appropriate language alters the results of AMS diagnostic scores in 4- to 11-yr-old children. With parental help, subjects completed the LLSS and an equivalent Lake Louise Age-Adjusted Symptom Score (LLAASS) daily for 3 days. Measurements were made at 1605 m, in the subjects' homes, without any altitude change. Equivalent questions between the two surveys were assessed for agreement on the day when the most symptoms were recorded for each question. Thirty-seven children (19 girls), ages 4 to 11 yr (mean age 7.4 +/- 2.3 yr) completed the study. Kappa values: headache (kappa = 0.22), gastrointestinal (kappa = 0.34), fatigue (kappa = 0.88), dizziness (kappa = 0.65), and sleep (kappa = 0.88) ranged from fair to very good. The LLAASS resulted in higher mean symptom scores (1.14 +/- 0.98) compared to LLSS questions (0.61 +/- 0.82) (p < 0.01). The AMS diagnostic threshold was reached in 9% (95% CI, 4-16) of measurements using the LLAASS and 4.5% (95% CI, 1.5-10) with the LLSS. The LLSS results in reporting of fewer AMS symptoms in this population when compared with a diagnostic tool using age-appropriate language and/or visual representations. Age-appropriate communication must be used to assess AMS, particularly for headache (the key symptom of AMS) and gastrointestinal symptoms. Young children report symptoms of AMS at baseline without altitude gain; therefore, the AMS diagnostic threshold in this population may require modification.     

Dexamethasone improves maximal exercise capacity of individuals susceptible to high altitude pulmonary edema at 4559 m

We have previously demonstrated that prophylactic intake of dexamethasone improves maximal oxygen uptake (Vo(2)max) in high altitude pulmonary edema (HAPE) susceptible subjects 4 to 6 h after a 2-day climb to 4559 m. However, since with this ascent protocol HAPE usually develops after the first night at 4559 m or later, we hypothesized that a continued dexamethasone prophylaxis would result in an even more pronounced improvement of Vo(2)max after an additional night at high altitude. Vo(2)max of 24 HAPE susceptibles was evaluated on a bicycle ergometer at an altitude of 490 m and at 24 h after rapid ascent to 4559 m. Subjects were divided into two groups: The control group (n=14) performed both tests without dexamethasone, whereas the dexamethasone group (n=10) received dexamethasone 8 mg twice a day (b.i.d), starting 24 h prior to ascent. At 4559 m, Vo(2)max was 61% ± 6% of the baseline value in the control group and 70% ± 9% in the dexamethasone group (p=0.025). Similarly, O(2) pulse (Vo(2)/heart rate) was 68% ± 7% and 77% ± 11% of baseline, respectively (p=0.043). Arterial O(2) saturation at maximal exercise did not differ between groups, whereas at rest it was 83% ± 10% in the control group and 91% ± 4% in the dexamethasone group (p=0.009). Dexamethasone prophylaxis increased Vo(2)max of HAPE-susceptible individuals after the first night at 4559 m without affecting arterial O(2) saturation at maximal exercise. This might be explained by a sustained effect of dexamethasone on maximal cardiac output and pulmonary O(2) diffusion, both resulting in enhanced convectional O(2) transport to the locomotor muscles.     

Preparation for football competition at moderate to high altitude

Analysis of ∼100 years of home-and-away South American World Cup matches illustrate that football competition at moderate/high altitude (>2000 m) favors the home team, although this is more than compensated by the likelihood of sea-level teams winning at home against the same opponents who have descended from altitude. Nevertheless, the home team advantage at altitudes above ∼2000 m may reflect that traditionally, teams from sea level or low altitude have not spent 1–2 weeks acclimatizing at altitude. Despite large differences between individuals, in the first few days at high altitude (e.g. La Paz, 3600 m) some players experience symptoms of acute mountain sickness (AMS) such as headache and disrupted sleep, and their maximum aerobic power (VO_2max) is ∼25% reduced while their ventilation, heart rate and blood lactate during submaximal exercise are elevated. Simulated altitude for a few weeks before competition at altitude can be used to attain partial ventilatory acclimation and ameliorated symptoms of AMS. The variety of simulated altitude exposures usually created with enriched nitrogen mixtures of air include resting or exercising for a few hours per day or sleeping ∼8 h/night in hypoxia. Preparation for competition at moderate/high altitude by training at altitude is probably superior to simulated exposure; however, the optimal duration at moderate/high altitude is unclear. Preparing for 1–2 weeks at moderate/high altitude is a reasonable compromise between the benefits associated with overcoming AMS and partial restoration of VO_2max vs the likelihood of detraining.     

药物对进驻高原青年睡眠剥夺及力竭运动时肺通气功能的影响

目的 :探讨红景天与乙酰唑胺对进驻高原青年睡眠剥夺及力竭运动时肺通气量的影响。方法 :将进驻海拔 370 0m 1个月的 2 4名健康青年随机分为 3组 ,每组 8人。受试者用EGM型踏车功量机做坐位踏车运动。初始负荷功率 2 5W ,每 3min递增 2 5W ,直至力竭。计算每位受试者的每分通气量 (VE)。第二次实验为 2 4h睡眠剥夺后 ;第三次实验为 3组受试者分别口服红景天、乙酰唑胺和安慰剂 2 0d后 ;第四次实验为服药后 2 4h睡眠剥夺后 ,实验方法与第一次相同。结果 :红景天组和乙酰唑胺组服药后与服药后睡眠剥夺后VE较服药前、睡眠剥夺后及对照组明显降低 ,差异非常显著 (P <0 .0 1 )。结论 :红景天和乙酰唑胺均能改善高原移居青年的肺通气及提高做功效率     

Short‐term cardiorespiratory adaptation to high altitude in children compared with adults

As short‐term cardiorespiratory adaptation to high altitude (HA) exposure has not yet been studied in children, we assessed acute mountain sickness (AMS), hypoxic ventilatory response (HVR) at rest and maximal exercise capacity (CPET) at low altitude (LA) and HA in pre‐pubertal children and their fathers. Twenty father–child pairs (11 ± 1 years and 44 ± 4 years) were tested at LA (450 m) and HA (3450 m) at days 1, 2, and 3 after fast ascent (HA1/2/3). HVR was measured at rest and CPET was performed on a cycle ergometer. AMS severity was mild to moderate with no differences between generations. HVR was higher in children than adults at LA and increased at HA similarly in both groups. Peak oxygen uptake (VO₂peak) relative to body weight was similar in children and adults at LA and decreased significantly by 20% in both groups at HA; maximal heart rate did not change at HA in children while it decreased by 16% in adults (P < 0.001). Changes in HVR and VO₂peak from LA to HA were correlated among the biological child–father pairs. In conclusion, cardiorespiratory adaptation to altitude seems to be at least partly hereditary. Even though children and their fathers lose similar fractions of aerobic capacity going to high altitude, the mechanisms might be different.     

Chronic intermittent hypoxia at high altitude exposure for over 12 years: assessment of hematological, cardiovascular, and renal effects

The aim of this cross-sectional study was to assess the health status of subjects weekly commuting between sea level and 3550-m altitude for at least 12 yr (average 22.1 +/- 5.8). We studied 50 healthy army men (aged 48.7 +/- 2.0) working 4 days in Putre at 3550-m altitude, with 3 days rest at sea level (SL) at Arica, Chile. Blood pressure, heart rate, Sa(O(2) ), and altitude symptoms (AMS score and sleep status) were measured at altitude (days 1, 2, and 4) and at SL (days 1, 2, and 3). Hematological parameters, lipid profile, renal function, and echocardiography were performed at SL on day 1. The results showed signs of acute exposure to hypoxia (tachycardia, high blood pressure, low Sa(O(2) )), AMS symptoms, and sleep disturbances on day 1, which rapidly decreased on day 2. In addition, echocardiographic findings showed pulmonary hypertension (PAPm > 25 mmHg, RV and RA enlargement) in 2 subjects (4%), a PAPm > 20 mmHg in 14%, and a right ventricle thickness >40 mm in 12%. Hematocrit (45 +/- 2.7) and hemoglobin (15 +/- 1.0) were elevated, but lower than in permanent residents. There was a remarkably high triglyceride level (238 +/- 162) and a mild decrease of glomerular filtration rate (34% under 90 mL/min and 8% under 80 mL/min of creatinine clearance). In conclusion, in these preliminary results, in chronic intermittent hypoxia exposure even over longer periods, most subjects still show symptoms of acute altitude illnesses, but a faster recovery. Findings in triglycerides, in the pulmonary circulation and in renal function, are also a matter of concern.     

Do changes in lung function predict high-altitude pulmonary edema at an early stage?

PURPOSE: Ascent to high altitude is associated with alterations in lung function. The mechanisms of these changes and whether they reflect early stages of high-altitude pulmonary edema (HAPE) has been debated. Therefore, we investigated the time course of pulmonary function in relation to hemodynamics and clinical symptoms in mountaineers ascending rapidly to high altitude. METHODS: In 26 unacclimatized subjects we assessed spirometry, single-breath nitrogen washout, diffusing capacity (DLCO), and Doppler echocardiography in Zurich, 490 m, after climbing within 24 h to Monte Rosa, 4559 m, and after one night at 4559 m. RESULTS: Mean (+/- SD) FVC fell from 103 +/- 9% predicted in Zurich to 96 +/- 10% predicted at 4559 m, FEV1/FVC increased from 0.82 +/- 0.06 to 0.84 +/- 0.08, and closing volume increased from 0.35 +/- 0.14 to 0.44 +/- 0.11 L above residual volume (P < 0.05, all changes). On the following day at 4559 m, closing volume remained elevated in 9 of 21 subjects who had a lower DLCO but similar pulmonary artery systolic pressures compared with the remaining 12 subjects (40 +/- 8 vs 43 +/- 7 mm Hg, P = NS). None of the subjects had overt HAPE. CONCLUSION: We conclude that changes in pulmonary function after rapid ascent to high altitude were consistent with interstitial fluid accumulation, but they were not related to changes in pulmonary artery pressure. Individual lung function responses to high-altitude exposure varied largely and did not predict subsequent HAPE.     

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.     

Kinematics of stair descent in young and older adults and the impact of exercise training

Stair descent is a challenging task in old age. This study firstly investigated lower extremity kinematics during stair descent in young (YOU) and healthy, community dwelling older adults (OLD). Secondly, the impact of an exercise training intervention on age-related differences in stair descent was assessed. At baseline, a motion analysis system was used to determine spatio-temporal gait variables and lower extremity kinematics as YOU (n=23, age=27+/-3 years) and OLD (n=34, age=73+/-4 years) descended a three step staircase. The older adults were then divided into training (TRA) and control (CON) groups. For 12 months, TRA performed resistance, aerobic, balance, and flexibility exercises under supervision in a class environment (twice per week) and unsupervised at home (once per week). CON carried on with normal daily activities. Following the intervention, baseline measurements were repeated in TRA and CON. At baseline, total descent, stride cycle, and single support times were longer in OLD than in YOU. In addition, sagittal plane knee motion was lower in OLD whilst frontal and transverse plane pelvis and hip motion were higher in OLD. Exercise training did not reduce the age-related differences observed. In conclusion healthy older adults perform stair descent at a slower speed and with greater motion outside the plane of progression than young adults. We found no evidence that these differences are reduced by generic exercise training, at least in non-frail older adults.     

Acute mountain sickness at 4500 m is not altered by repeated eight-hour exposures to 3200-3550 m normobaric hypoxic equivalent

A lightweight device, designed to supply inspired air at 12.8% O2 concentration (PO2 equivalent to 3960 m altitude) by recirculating a portion of each expired breath after CO2 removal, was tested at sea-level for its ability to induce altitude acclimation. Twelve young men (experimental group) breathed from the device for 7.5-8 h each day for 10 successive days. On the morning of day 1, inspired O2 concentrations averaged 12.8%, as intended, but increased by noontime and remained elevated thereafter. This raised the average hypoxic stimulus to 13.8 +/- 0.9% (PO2 equivalent to 3370 +/- 517 m altitude) for the entire 10-d period. Ten other young men (control group) breathed normoxic air from a placebo device of identical appearance on the same schedule. On day 10, both groups were exposed for the next 2 d to 4500 m altitude in a hypobaric chamber to assess the effect of the treatment on acute mountain sickness (AMS). After the sea level treatment, the experimental group showed no significant differences from control in resting ventilatory rate, respiratory frequency or end tidal PO2, but end-tidal PCO2 was lower; there was no indication of hemoconcentration. At altitude, both groups showed the expected decreases in end-tidal PO2 and PCO2, and increases in hemoglobin concentration and hematocrit indicative of hemoconcentration, with no differences between them. Neither incidence nor severity of AMS differed significantly between groups, but the experimental group had a lower incidence rate than historical controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma nitrite/nitrate and erythropoietin levels in cross-country skiers during altitude training

BACKGROUND: The aim of this study was to evaluate the effects of training at altitude on plasma nitrite/nitrate and erythropoietin levels since previously it has been reported an interaction of the NO/cGMP system in erythropoietin production. METHODS: Nine physically trained cross-country male skiers, usually living at 800-1200 m altitude, underwent 6 days of intensive training at a moderate altitude of 3100 m preceeded by 2 days of acclimatisation. Six team-managers, selected as controls, did not undergo any regular physical activity in the last 5 years and during the altitude period. Haematological parameters, erythropoietin and nitrite/nitrate were measured prior to reach the place at altitude, at the end of the period at moderate altitude and 7 days after returning at home. RESULTS: Haematocrit significantly increased in controls after 8 days at altitude. Erythropoietin levels significantly increased after the intensive altitude training only in trained subjects (13.1+/-1.7 vs 6.7+/-1.7 mU x ml-1, p<0.001). Nitrite/nitrate baseline values were significantly higher in trained subjects compared to untrained (49.9+/-17.9 vs 25.4+/-2.8 micromol x l(-1), p<0.01); the altitude period significantly increased nitrite/nitrate levels, in untrained subjects, to the same values observed in trained subjects under control conditions (47.0+/-10.3 micromol x l(-1)). CONCLUSIONS: In our experimental conditions we demonstrated the influence of hypoxia on Epo levels in athletes sustaining a short-term training and the role of a regular physical activity (partly independent from altitude hypoxia) on NO production.     

Residence at moderate altitude improves ventilatory response to high altitude

BACKGROUND: This study compared the distribution of arterial oxygen saturation (SaO2) and susceptibility to Acute Mountain Sickness (AMS) in moderate altitude residents (MAR) and low altitude residents (LAR) following rapid ascent to 4056 m. METHODS: Resting PETCO2 and SaO2 were measured in 38 subjects residing for > 3 mo near Colorado Springs, CO (MAR group), at 1940 m (USAF Academy), and after approximately 1 h at 4056 m on the summit of Pikes Peak, CO, following ascent by car. SaO2 was also measured at 610-m elevation intervals during the ascent. Of the LAR (50 m) group, 39 subjects were exposed to a similar ascent profile in a hypobaric chamber. RESULTS: At 1940 m the MAR SaO2 and PETCO2 were 94 +/- 1% (X +/- SD) and 33.6 +/- 2.8 mmHg, respectively. At 3048 m and higher, MAR SaO2 decreased, reaching 86 +/- 2% (p < 0.001) at 4056 m, and PETCO2 (32.1 +/- 4.5 mmHg) decreased (p < 0.05). At 50 m the LAR SaO2 and PETCO2 were 98 +/- 1% and 38.7 +/- 2.7 mmHg, respectively. At 1940 m and higher, LAR SaO2 decreased (p < 0.001), reaching 82 +/- 5% at 4056 m, and PETCO2 (36.4 +/- 3.5 mmHg) decreased (p < 0.05). Above 2438 m, the MAR SaO2 was higher (p < 0.001) than the LAR. Only one MAR subject, but nine LAR subjects reported AMS symptoms. CONCLUSIONS: Ventilatory acclimatization developed during moderate altitude residence substantially enhances arterial oxygenation during rapid ascents to higher altitudes. Compared with prior studies, the level of ventilatory acclimatization achieved at moderate altitude is similar to residing at 4056 m for approximately 5-9 d.     

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。     

Evidence for exercise-induced bone formation in premature infants

We assessed the effect of a four weeks exercise training intervention on bone turnover markers in premature infants. Twenty-four very low birth weight premature infants were matched for gestational age, birth weight, gender, as well as for corrected age and weight at initiation of the study. Then the subjects were randomly divided into an exercise (n = 12) and a control group (n = 12). Exercise consisted of passive range of motion exercise with gentle compression of both the upper and lower extremities lasting 5 - 10 minutes each day, 5 days per week for 4 weeks. This protocol has been shown to increase bone mineral density in premature infants. Bone formation was assessed by measurements of circulating bone specific alkaline phosphatase (BSAP) and the C-terminal procollagen peptide (PICP). Bone resorption was determined by serum measurements of C- terminal cross-links telopeptide of type-I collagen (ICTP). Training led to a significant (P < 0.05) increase in weight gain (767 +/- 49 versus 586 +/- 24 gr in trained and control premature infants, respectively); and to a significant increase in BSAP (37.2 +/- 14.6 versus 4.1 +/- 8.4 % in trained and control premature infants, respectively). PICP increased also following exercise (34.6 +/- 18.9 versus 5.4 +/- 9.1 % in trained and control subjects, respectively), however, this increase was not statistically significant. Exercise led to a significant decrease in ICTP (-24.7 +/- 3.1 versus -5.5 +/- 5.4 % in trained and control subjects, respectively). A relatively brief exercise intervention was associated with a biochemical evidence of bone formation in very low birth weight premature infants.     

Oxygen saturation course and altitude symptomatology during an expedition to broad peak (8047 m)

Thirteen healthy European mountaineers (11 male, 2 female) participated in the 62-day German-Pakistani Research Expedition to Broad Peak (8047 m) in the Karakorum, Pakistan. During ascent, base camp stay and approach to the summit, oxygen saturation was measured by pulse oximetry at rest, during exercise and during sleep; in addition, questionnaires on high altitude symptomatic had to be answered. We found a dramatic decrease in oxygen saturation especially at extreme altitudes (7100 m: Median 63%, Min 59%, Max 65%) and a long time required for real acclimatization. The lowest figures at 4850 m were found during maximal exercise, 77.5% (69 - 85%) and during sleep, 81% (73 - 88%), the highest ones at rest, 86.5% (77 - 89%). There was a significant correlation (Spearman rank correlation coefficient with ties) between measured oxygen saturation during the ascent to/stay at base camp and high altitude illness (p = 0.005 - 0.05), as well as with high altitude performance (p = 0.025 - 0.01). The limiting values of "no high altitude symptomatic", "high altitude discomfort", AMS and the malignant forms could be estimated for acclimatized (>90%/>80%/>70%/<70%) and unacclimatized (>80%/>70%/>65%/<65%) condition. Pulse oximetry is an objective non-invasive method of measurement that is easy to handle. It is a suitable device besides clinical examination and questionnaire-test in the diagnosis of high altitude illness even in the hands of non-professionals. The measurement at sleep can possibly explain present high altitude symptomatic despite of (nearly) normal oxygen saturation values at rest.     

高原OSAHS患者睡眠呼吸参数与体重指数、颈围测量的关系

目的：探讨高原阻塞性睡眠呼吸暂停低通气综合征（OSAHS）患者的体重指数（BMI）,颈围（NC）与睡眠呼吸参数之间的关系。方法：对海拔2300m～3700m经睡眠多导仪（PSG）监测确诊为OSAHS：病人30例与29例正常人进行身高、体重、颈围指标测量对照分析。结果：正常组与OSAHS组BMI、NC的均值间差别有显著性意义（P〈0．001）,正常组与OSAHS组的平均呼吸暂停时商（秒）,睡眠呼吸暂停低通气指数（AHI,次／h）,动脉血氧饱和度（SaO2％）及醒觉次数／h的均值间差别均有显著性意义（P〈0．001）。结论：OSAHS患者夜间AHI与SaO2有较好的相关性,BMI、NC与OSAHS及其严重程度有关,常发生在肥胖的中老年男性中。     

Effects of different stay durations on attentional performance during two mountain expeditions

BACKGROUND: Hypoxia-induced deficits in intellectual performance are linked to the altitude level reached, the speed of the ascent and the time spent at high altitude. This study analyzes attentional changes during adaptation to two different types of stay at high altitude on two different expeditions: one involving a 16-d trip between 2,000 m and 5,600 m, followed by a 2-d ascent to 6,440 m and back again; the other, a 21-d stay at 6,542 m. We tested the hypothesis that, at similar high altitudes, decrements in attentional performance would only occur during a long duration stay. METHODS: Indexes for attentional performance were calculated for two experimental groups under normoxia before the climb, under acute and chronic hypoxia during the climb, and under normoxia after the climb. They were compared for two control groups tested only under normoxia. RESULTS: The altitude stay was found to have an effect on the 6,542 m group when compared with the controls. Group performance differed at 2 d and 21 d after their arrival at 6,542 m and after their return to normoxia. When all the test administrations were pooled together for this expedition we noted an interaction between the level of difficulty of the task and the experimental and control groups: namely the difference between the groups was greater for the difficult task than it was for the easy task. No effect was found for the other expedition (at 5,600 m) when the group tested was compared with the controls. CONCLUSION: For a 21-d stay at an altitude of 6,542 m with the same ascent protocol as a group climbing to a lower altitude (16 d between 2,000 m and 5,600 m followed by a 2 d ascent to 6,440 m and back again), subjects appeared to suffer from attentional performance deficits which persisted for several days after the subjects returned to normoxic conditions.     

Effects of one night of sleep deprivation on hormone profiles and performance efficiency

This study examined the effects of one night of sleep deprivation on melatonin and cortisol profiles, as well as performance efficiency of military service members. Sleep intervention consisted of total lack of sleep (N = 7) or 8 hours of sleep (control group; N = 7) during the night. All parameters were measured at selected time intervals before (day 1), during (only in sleep-deprived individuals), and after (day 2) sleep intervention. Rotary pursuit scores and handgrip strength data were used as indices of psychomotor and physical performance, respectively. In sleep-deprived individuals, more salivary melatonin, but not cortisol, was secreted than in subjects who slept adequately. Significant increases in melatonin and cortisol were noted, especially at 1:30 p.m. on the day after nighttime sleep deprivation. In contrast, the tracking scores for rotary pursuit and grip strength among sleep-deprived and rested individuals were comparable. Across a normal working day (day 1), all parameters studied revealed time-specific fluctuations in both control and sleep-deprived groups. Irrespective of nighttime sleep schedule, the patterns of performance on day 2 differed from those on day 1. The tracking performance improved on day 2, whereas grip strength worsened, which may reflect inherent learning and muscle fatigue, respectively. During the night of sleep deprivation, performance declined. In conclusion, the present study showed that one night of sleep deprivation (8 hours) resulted in significant hormonal changes on the next afternoon but did not modify tracking and muscular strength performance.