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PubMed2003

Intrauterine growth restriction, preeclampsia, and intrauterine mortality at high altitude in Bolivia.

Infant mortality and stillbirth rates in Bolivia are high and birth weights are low compared with other South American countries. Most Bolivians live at altitudes of 2500 m or higher. We sought to determine the impact of high altitude on the frequency of preeclampsia, gestational hypertension, and other pregnancy-related complications in Bolivia. We then asked whether increased preeclampsia and gestational hypertension at high altitude contributed to low birth weight and increased stillbirths. We performed a retrospective cohort study of women receiving prenatal care at low (300 m, Santa Cruz, n = 813) and high altitude (3600 m, La Paz, n = 1607) in Bolivia from 1996 to 1999. Compared with babies born at low altitude, high-altitude babies weighed less (3084 +/- 12 g versus 3366 +/- 18 g, p < 0.01) and had a greater occurrence of intrauterine growth restriction [16.8%; 95% confidence interval (CI): 14.9-18.6 versus 5.9%; 95% CI: 4.2-7.5; p < 0.01]. Preeclampsia and gestational hypertension were 1.7 times (95% CI: 1.3-2.3) more frequent at high altitude and 2.2 times (95% CI: 1.4-3.5) more frequent among primiparous women. Both high altitude and hypertensive complications independently reduced birth weight. All maternal, fetal, and neonatal complications surveyed were more frequent at high than low altitude, including fetal distress (odds ratio, 7.3; 95% CI: 3.9-13.6) and newborn respiratory distress (odds ratio, 7.3; 95% CI: 3.9-13.6; p < 0.01). Hypertensive complications of pregnancy raised the risk of stillbirth at high (odds ratio, 6.0; 95% CI: 2.2-16.2) but not at low altitude (odds ratio, 1.9; 95% CI: 0.2-17.5). These findings suggest that high altitude is an important factor worsening intrauterine mortality and maternal and infant health in Bolivia.

Adult↗
PubMed1985

Standardized hemorrhagic shock in rats after acute and chronic exposure to high altitude.

Acute exposure to high altitude for 1 day in rats caused an increase in hematocrit (Hct) with no change in mean arterial blood pressure (mABP) from the non-altitude control, whereas after prolonged exposure to altitude (5-6 weeks) there were increases in both Hct and mABP. No changes in total plasma protein (TPP) and plasma osmolality (POsm) from control rats were observed in all altitude-exposed animals. The ability of the acutely and chronically altitude and non-altitude exposed rats to resist hemorrhage was studied. Hemorrhage was standardized at mABP in the range of 30-35 mmHg. Chronic exposure to altitude increased the initial and maximum volume of blood withdrawn as well as the oligemic and survival times, whereas acute altitude exposure did not. The higher ability to resist standardized hemorrhagic shock of the chronically altitude exposed rats seemed to result, in part, from their greater hemodilution and better arterial blood pressure regulation. No difference in the rate of hemodilution as well as hemorrhagic tolerance was observed between the 1-day altitude and control rats. The difference in rate of hemodilution between the chronic altitude and control animals could not be due to arterial hyperosmolality since the magnitude of change in POsm during blood loss was the same for all animals groups.

Altitude↗
PubMed2004

[Comparitive [Comparative] study of the indexes of pulmonary arterial pressure of healthy children at different altitudes by Doppler echocardiography].

OBJECTIVE: Reduced oxygen availability at a high altitude is associated with increased pulmonary arterial pressure (PAP). With the altitude goes up the change of PAP in healthy children is still not clear. The difference of PAP in native Tibetan and Han children at a high altitude are also not clear. Many studies have shown that Doppler echocardiographic estimation of PAP correlates closely to the values obtained with the invasive measurement. Therefore the indexes of PAP in health children living at different altitudes were investigated and the indexes of PAP in Han and Tibetan children at the high altitude were compared by Doppler echocardiography. METHODS: A randomized survey was carried out on the indexes of PAP with Doppler echocardiography (HP-8500 and CAL-163 echocardiographic machine) by two doctors of Qinghai Provincial Women and Children Hospital from June 1998 to July 2002. The survey covering Jiuzhi Qinghai (at 3700 m above the sea level), Xining Qinghai (at 2260 m above the sea level) and Shanghai (at 16 m above the sea level) included a population of 1061 children aged 0 - 14 years. The population of 1061 composed of 218 Han children at Shanghai, 567 Han children at Xining Qinghai and 276 children at Jiuzhi, Qinghai including 118 migrated Han and 148 native Tibetan children. The physical, EKG and chest X-ray examination of each child were carried out to ensure all the subjects were healthy. A pulse oximeter was placed on each child's foot to provide measurements of arterial oxygen saturation (SO2) distal to the ductus arteriosus. The indexes of PAP included right ventricular systolic time interval (RSTI) and mean of pulmonary arterial pressure (mPAP) which was assessed by a multiple regression equation (mPAP=27.79 + 35.42 x PEP/AT-50.85 x AT/ETc). The AT/ETc was that AT/ET was divided by R-R. The RSTI included previous ejection period (PEP), ascending time (AT), ejection time (ET), PEP/AT and AT/ET. All subjects were divided into 7 age groups. The data of PAP indexes were compared among three different altitude groups and age groups. The data of PAP indexes were also compared in Han and Tibetan children living over 3700 m sea level in each age group. RESULTS: With the altitude increase the SO2 of the subjects obviously reduced and the indexes of PAP changed. The SO2 correlated closely with the PEP, AT, PEP/A, AT/ET and mPAP (r = 0.352, 0.144, -0.394, -0.166 and -0.363, respectively; P < 0.01). The AT and AT/ET in the groups of 2260 m and 3700 m were shorter than those in the group of 16 m (P = 0.03-0.000) in each age group. The PEP and PEP/AT in 3700 m group were longer than those in 2260 m and 16 m groups (P=0.006-0.000) in each age group. The mPAP in 3700 m group was higher than that in 2260 m and 16 m groups in each age group (mean [+/-SE] mmHg, 35.23 +/- 8.72 vs 17.99 +/- 8.78 and 15.86 +/- 8.96 aged 0 - 28 d, 32.06 +/- 13.38 vs 20.72 +/- 5.71 and 14.64 +/- 8.19 aged to 6 mo, 31.83 +/- 10.53 vs 20.89 +/- 10.12 and 14.69 +/- 5.89 aged to 1 yr, 27.58 +/- 13.55 vs 19.12 +/- 9.75 and 17.36 +/- 6.71 aged to 3 yr, 24.19 +/- 8.38 vs 19.64 +/- 9.36 and 16.43 +/- 4.68 aged to 6 yr, 23.90 +/- 11.35 vs 16.77 +/- 6.79 and 14.42 +/- 6.50 aged to 10 yr, 23.08 +/- 7.31 vs 18.53 +/- 7.25 and 15.45 +/- 6.12 aged to 14 yr, P=0.000). With the growth of the children the reduction of PAP was remarkable at 3700 m above sea level (F=5.638 P=0.000), the mPAP indexes of the first, second and third age groups were evidently higher than those of the other age groups. The SO2, RSTI and mPAP in the native Tibetan children were not different from those in the migrated Han children (P > 0.05) in each age group. CONCLUSION: The PAP of healthy children at the high altitude was different from that of healthy children at the low altitude. The PAP of the healthy children at 3700 m above sea level was remarkably increased. At 3700 m above sea level the PAP of newborns and infants increased much more compared with that of juvenile. The race may not significantly affect the PAP at the high altitude. The high altitude hypoxic environment might play a major role in the increase of PAP.

Adolescent↗
PubMedDate not supplied

[Ecological study of Pyroglyphides mites in house dust in the Grenoble area. A qualitative approach and incidence of various parameters: seasons, altitude, temperature and relative dampness in their multiplication].

This study concerns the analysis of 70 samples of dust mites taken periodically from 13 sample areas or mattresses at different altitudes. It shows the presence of Pyroglyphid mites in all the mattresses studied. Four species were found: Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei and Dermatophagoides evansi. From a quantitative point of view, the statistical analysis of the results obtained allows the following conclusions to be drawn: -- All the Pyroglyphids (adults and young) undergo seasonal fluctuations at low, middle and high altitude. In the plains and at middle altitude these mites have a seasonal maximum and minimum. At high altitude only the seasonal maximum can be determined. -- The number of Pyroglyphids found is much higher in the plaine than at middle altitude and at middle altitude than at high altitude. The influence of altitude can be demonstrated with certitude. -- The conditions of temperature and relative dampness most favourable to the multiplication of mites are found in the plaine. At middle and high altitude these conditions are only met in summer. In flat country the statistical analysis allows us to show the existance of a correlation between the rate of dampness and the number of Pyroglyphids, and more specially, between the dampness rate and Dermatophagoides farinae, a predominant species at this sampling area. At middle and high altitude such a correlation cannot be shown clearly. At the three altitudes considered, no correlation can be established between the temperature and the number of Pyroglyphid mites found.

Altitude↗
PubMed2001

Effects of high-altitude exposure on vascular endothelial growth factor levels in man.

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen and permeability factor that is inducible by hypoxia. Its contribution to high-altitude illness in man is unknown. We measured VEGF levels in 14 mountaineers at low altitude (490 m) and 24 h after their arrival at high altitude (4,559 m). At high altitude, VEGF increased from [mean (SEM)] 32.5 (9.2) to 60.9 (18.5) pg.ml(-1) (P < 0.004) in the arterial blood, and from 15.9 (2.9) to 49.3 (15.9) pg.ml(-1) (P= 0.0001) in the mixed venous blood. Whereas at low altitude venous and arterial VEGF levels were not statistically different from each other (P= 0.065), the VEGF concentration was significantly lower in venous than in arterial blood samples at high altitude (P=0.004). The pulmonary capillary VEGF concentration remained unchanged at high altitude [14.8 (2.5) vs 17.1 (5.4) pg.ml(-1), P=0.85]. VEGF levels in the nine mountaineers who developed symptoms of acute mountain sickness (AMS), and in the six subjects who had radiographic evidence of high-altitude pulmonary edema were similar to those in subjects without symptoms. VEGF was not correlated with either AMS scores, mean pulmonary arterial pressures, arterial partial pressure of O2, or alveolar-arterial O2 gradients. We conclude that VEGF release is stimulated at high altitude, but that VEGF is probably not related to high-altitude illness.

Adult↗
PubMed2004

Increased oxidative stress following acute and chronic high altitude exposure.

The generation of reactive oxygen species is typically associated with hyperoxia and ischemia reperfusion. Recent evidence has suggested that increased oxidative stress may occur with hypoxia. We hypothesized that oxidative stress would be increased in subjects exposed to high altitude hypoxia. We studied 28 control subjects living in Lima, Peru (sea level), at baseline and following 48 h exposure to high altitude (4300 m). To assess the effects of chronic altitude exposure, we studied 25 adult males resident in Cerro de Pasco, Peru (altitude 4300 m). We also studied 27 subjects living in Cerro de Pasco who develop excessive erythrocytosis (hematocrit > 65%) and chronic mountain sickness. Acute high altitude exposure led to increased urinary F(2)-isoprostane, 8-iso PGF(2 alpha) (1.31 +/- 0.8 microg/g creatinine versus 2.15 +/- 1.1, p = 0.001) and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.37 +/- 0.09, p = 0.002), with a trend to increased plasma thiobarbituric acid reactive substance (TBARS) (59.7 +/- 36 pmol/mg protein versus 63.8 +/- 27, p = NS). High altitude residents had significantly elevated levels of urinary 8-iso PGF(2 alpha) (1.3 +/- 0.8 microg/g creatinine versus 4.1 +/- 3.4, p = 0.007), plasma TBARS (59.7 +/- 36 pmol/mg protein versus 85 +/- 28, p = 0.008), and plasma total glutathione (1.29 +/- 0.10 micromol versus 1.55 +/- 0.19, p < 0.0001) compared to sea level. High altitude residents with excessive erythrocytosis had higher levels of oxidative stress compared to high altitude residents with normal hematological adaptation. In conclusion, oxidative stress is increased following both acute exposure to high altitude without exercise and with chronic residence at high altitude.

Acclimatization↗
PubMed2006

Cardiopulmonary pathology among children resident at high altitude in Tintaya, Peru: a cross-sectional study.

Symptomatic high-altitude pulmonary hypertension and structural cardiac abnormalities related to high altitude have been reported previously. However, their true prevalence has not been systematically determined. We assessed clinical indicators of cardiovascular health or disease and correlated them with anatomic and physiologic cardiovascular features in preschool and schoolchildren living at 4000 m. We also estimated the prevalence of cardiovascular problems in the population, with emphasis on symptomatic high altitude pulmonary hypertension and structural cardiopathies. Three hundred and twenty-six children residents of Tintaya, Peru, were cross-sectionally studied. Methods included structured interviews, anthropometry and physical examination, arterial oxygen saturation, hemoglobin determination, electrocardiography, and echocardiography. The prevalence of structural cardiac problems was 1.5%, with less than 1% possibly attributable to high altitude. All children with structural cardiac abnormalities were identified by a focused physical exam prior to echocardiography. None were identified by the health interview. No symptomatic high altitude pulmonary hypertension was identified in the absence of underlying structural anomalies. The prevalence of structural cardiac problems was consistent with data from sea level. Active monitoring of the health status of a pediatric population at high altitude is valuable in the timely detection of cardiac abnormalities. Although our study children enjoyed generally excellent health, comparative, longitudinal studies are warranted to determine the incidence of high altitude cardiopulmonary problems and to identify risk factors and early markers for later disorders associated to life at high altitude. Our findings are applicable to children with some degree of high altitude genetic background and high mobility patterns to lower altitudes and living in comparatively good nutritional and socioeconomic conditions.

Adolescent↗
PubMedDate not supplied

Ophthalmological effects of high altitude.

High altitude has various effects on human beings. Altitude-related illnesses are a frequent cause of morbidity and occasional mortality in travelers to high altitudes throughout the world. The mountaineers all around the world are familiar with this condition, which is called acute mountain sickness (AMS). The primary altitude illnesses are AMS, high-altitude pulmonary edema and high-altitude cerebral edema. Altitude has potential undesired ophthalmological effects. The pathogenesis of these syndromes remains unclear despite considerable research in this field. Most of these problems are primarily preventable with an adequate level of information before and during travel. Further studies are needed to reveal the exact relationship between high altitude and ophthalmological findings. In this article, ophthalmological effects of high altitude, likely to be encountered by mountaineers as well as other enthusiasts of high altitude sports are reviewed. Emphasis on aviation and aerospace medicine is briefly given under related SUB_TITLEs.

Aerospace Medicine↗
PubMed1995

Endothelin-1 in pulmonary hypertension associated with high-altitude exposure.

BACKGROUND: Endothelin-1 is involved in chronic pulmonary hypertension. Its role in acute pulmonary hypertension due to hypoxia in humans is not clear. We therefore studied the influence of hypoxia caused by exposure to high altitude on plasma endothelin-1 levels, arterial blood gases, and pulmonary arterial pressure in subjects taking nifedipine or placebo. METHODS AND RESULTS: Twenty-two healthy volunteers were investigated at low altitude (490 m) and high altitude (4559 m). Arterial blood gases were analyzed immediately, endothelin-1 was measured by radioimmunoassay, and pulmonary artery pressure was assessed by Doppler echocardiography. After baseline investigations, the mountaineers were allocated in a randomized double-blind fashion to receive either placebo or nifedipine (20 mg TID) during rapid ascent to high altitude within 22 hours. Tests were repeated at the high-altitude research laboratories located in the Capanna "Regina Margherita" (Italy, 4559 m). Plasma endothelin-1 was increased twofold at high altitude (5.9 +/- 2.2 pg/mL compared with 2.9 +/- 1.1 pg/mL, P < .05), was inversely related to arterial PO2 (r = -.46, P < .001), and correlated with pulmonary artery pressure (r = .52, P < .002). At high altitude, arterial endothelin-1 was lower (4.3 +/- 1.6 pg/mL) than venous endothelin-1 (5.9 +/= 2.2 pg/mL, P < .001), indicating either predominant production in the venous vasculature or pronounced clearance in the pulmonary circulation. The calcium antagonist nifedipine, which lowered pulmonary artery pressure at high altitude (32 +/- 5 versus 42 +/- 11 mm Hg, P < .05), had no influence on plasma endothelin-1 levels. The administration of 35% O2 at high altitude normalized arterial PO2, tended to decrease endothelin-1, and decreased pulmonary artery pressure accordingly. CONCLUSIONS: We conclude that plasma endothelin-1 is increased at high altitude, but whether or not it represents an important pathogenetic factor for pulmonary hypertension remains to be investigated.

Adult↗
PubMedDate not supplied

Tibetan protection from intrauterine growth restriction (IUGR) and reproductive loss at high altitude.

Chronic hypoxia at high altitude restricts fetal growth, reducing birth weight and increasing infant mortality. We asked whether Tibetans, a long-resident high-altitude population, exhibit less altitude-associated intrauterine growth restriction (IUGR) and prenatal or postnatal reproductive loss than Han (ethnic Chinese), a group that has lived there for a shorter period of time. A population sample was obtained, comprising 485 deliveries to Tibetan or Han women over an 18-month period at 8 general hospitals or clinics located at 2,700-4,700 m in the Tibet Autonomous Region, China. Birth weight, gestational age, and other information were recorded for each delivery. Prenatal and postnatal mortality were calculated using information obtained from all pregnancies or babies born to study participants. Tibetan babies weighed more than the Han, averaging 310 g heavier at altitudes 2,700-3,000 m (95% CI = 126, 494 g; P < 0.01) and 530 g heavier at 3,000-3,800 m (210, 750 g; P < 0.01). More Han than Tibetan babies were born prematurely. Prenatal and postnatal mortality rose with increasing elevation and were 3-fold higher across all altitudes in the Han than the Tibetans (P < 0.05). Tibetans experience less altitude-associated IUGR than Han and have lower levels of prenatal and postnatal mortality. When the relationships between birth weight and altitude are compared among these and other high-altitude populations, those living at high altitude the longest have the least altitude-associated IUGR. This may suggest the occurrence of an evolutionary adaptation.

Adult↗
PubMedDate not supplied

Cross-sectional study of echocardiographic characteristics in healthy children living at high altitude.

Non-echocardiographic studies in healthy high altitude children have shown right ventricle predominance during infancy and childhood, associated to asymptomatic pulmonary hypertension and an increased pulmonary artery pressure. Systematic studies on echocardiography in such children have not been performed. In a cross-sectional study, we measured right and left heart morphologic and functional parameters, through M-mode, two-dimensional Doppler, and color Doppler echocardiographies, in a population of 321 healthy children ranging in age from 2 months to 19 years and living at high altitude (Tintaya, Peru, 4,100 m). Structured ad-hoc interviews were done to obtain information on medical history, patterns of exposure to high altitude of children and their parents and grandparents, place and altitude of pregnancy and birth, and housing conditions. A complete physical examination was performed before echocardiography. Hemoglobin concentration, pulse oximetry, and anthropometry were measured in all participating children. The right and left heart morphologic and functional echocardiographic measurements expressed by age and by body surface area were generally similar to sea-level reference populations. They were not consistently influenced by sex, nutritional status, chest dimensions, pulse oximetry, hemoglobin concentration, ethnicity, length of residence at high altitude, or parental history of exposure to high altitude. Most children had at least some degree of high-altitude ancestry as assessed by ethnicity and history of parental exposure to altitude. The cardiovascular development at high altitude in children with some degree of high-altitude ancestry seems to follow a pattern similar to sea-level children. The results can be used as reference values to interpret individual echocardiographic studies in comparable children living in similar settings.

Adolescent↗
PubMed1993

The effect of ski training at altitude and racing on pituitary, adrenal and testicular function in men.

The effect of similar prolonged exercise on hormonal changes was studied at sea level and at moderate altitude. Four cross-country skiers participated in a 30-km race and five biathlonists in a 20-km race at sea level in Finland and during altitude training and racing at 1650 m in Les Saisies, France. Venous blood samples were taken at both altitudes before the race between 0800 and 0900 hours and 25-35 min after the race. Resting blood samples were also taken before and after the altitude training and the period of racing. Serum testosterone concentration was higher before the race at altitude than at sea level (19%, P < 0.02), and 30 min after the race growth hormone (GH) concentration was higher at sea level than at moderate altitude (P < 0.002). There were not significant differences in serum luteinising hormone between the altitudes. Serum cortisol concentration was higher after the altitude training and the period of racing than before (P < 0.02) but no difference was observed in testosterone. We concluded, that since the profiles of the anabolic-catabolic hormone concentrations measured are indicators of the performance level of athletes, our data indicated that to follow them during altitude training could be beneficial in optimizing training programme for individual athletes. We also concluded, that the lower GH concentration after racing at moderate altitude may have been a consequence of decreased racing speed and/or increased physical performance.

Adrenal Glands↗
PubMed1988

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists.

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.

Adolescent↗
PubMed1997

[High altitude training: sense, nonsense, trends].

Athletes who need high endurance capacity often use training at moderately high altitude (1500-3000 m) to improve oxygen delivery and utilization because of a hypoxia-induced increase of the red blood cell volume and adaptations at the muscular level. As maximal heart rates decrease at high altitude and plasma lactate levels for a given workload change during prolonged exposure to high altitude, it can be difficult to control and adapt the intensity and duration of the work-outs. Furthermore, maximal performance capacity decreases and therefore training intensity at high altitude is usually reduced compared to training at sea level. To avoid these disadvantages at high altitude a concept of living at moderately high altitude and training at lower elevations, termed "live high-train low" evolved, opposing the conventional concept of "live high-train high". A third option using a hypobaric chamber ("live low-train low") is hardly used anymore for training athletes. Studies on the effects of conventional high-altitude training for the improvement of athletic performance often lack a rigorous controlled design and yield controversial results. Regarding the new concept of "live high-train low" there is only one controlled study on college athletes and it shows a minor advantage of this new approach compared to conventional high-altitude training. However, training concepts are especially important for elite competitive athletes, and controlled studies with such individuals are very difficult to perform. Therefore, it appears that today we cannot answer the question of whether altitude-specific physiologic factors or non-altitude-related benefits of training camps account for the success of individual athletes.

Altitude↗
PubMed2006

Maternal oxygen administration and fetal cerebral oxygenation: studies on near-term fetal lambs at both low and high altitude.

OBJECTIVE: We tested the hypothesis that O2 administration to the mother would increase arterial O2 tension (PaO2) and cortical tissue O2 tension (tPO2) in both the normoxic control fetus and that acclimatized to high altitude, and that this effect might be greater in the high altitude fetus than that at sea level. STUDY DESIGN: Pregnant ewes were divided into either low-altitude group or high-altitude group (3820 m; maintained from day 30 of gestation to near-term, term = 145 days; n = 6 each). In near-term fetuses we instrumented the cerebral cortex with tissue PO2-laser Doppler flow probes, and placed arterial catheters. With the ewe breathing either air or 50% O2, we measured fetal arterial and brain tissue PO2 and cerebral blood flow (CBF). RESULTS: In response to maternal O2 administration, in both low- and high-altitude fetuses, PaO2, O2 content, and brain tissue PO2 increased significantly. Nonetheless, the fetuses at high altitude showed significantly greater increase in both PaO2 and cerebral tPO2, than that seen in fetuses at low altitude. In neither group was there a change in CBF or cerebral metabolic rate for O2. CONCLUSION: Maternal O2 administration significantly increased PaO2 and cerebral tPO2 of the fetus both at low altitude and at high altitude, with this increase being greater in the high altitude animals. We suggest that maternal O2 administration can have an important effect in ameliorating nonreassuring fetal status, and perhaps be of value in instances of mothers who smoke heavily or with cardiopulmonary disease.

Acclimatization↗
PubMedDate not supplied

High-altitude-related disorders--Part I: Pathophysiology, differential diagnosis, and treatment.

As increasing numbers of people choose to sojourn or retire to the mountains, high-altitude illness is becoming a pathological phenomenon about which healthcare providers should have greater awareness. Hypoxia is the primary cause of high-altitude illness, but other stressors on the sympathetic nervous system, such as cold and exertion, also contribute to disease development and progression. Although variable across persons, symptoms of high-altitude disorders usually occur at altitudes over 7000 feet, and typically in 1 of 3 forms: acute mountain sickness (AMS), high-altitude cerebral edema (HACE), or high-altitude pulmonary edema (HAPE). Major symptoms include nausea, poor sleep, headache, lassitude, cough, dyspnea on exertion and at rest, ataxia, and mental status changes. As a rule, illness occurring at high altitude should be attributed to the altitude until proven otherwise. Treatment is best accomplished by descent and by oxygen or pharmacologic intervention if necessary. Under no circumstances should a person with worsening symptoms of high-altitude illness delay descent. As will be discussed in part II of this article, gradual ascent and subsequent acclimatization to altitude is the most effective prevention, though acetazolamide (Diamox) may be a useful prophylactic measure in some.

Acetazolamide↗
PubMed1996

Physical activity at altitude in pregnancy.

Advice to pregnant women wishing to exercise at altitude is based only on isolated observations and a handful of systematic studies, none of which have explored the limits of combined exercise and altitude exposure in human pregnancy (ie, at maximal exercise and maximal altitude). Guidelines must therefore be based on a variety of sources, including the physiology of permanent residence at high altitude, in particular the degree of (and hence requirement for) adaptations specific to pregnancy over and above simple altitude acclimatization, and data from the few systematic studies in human pregnancy under conditions of short-term altitude exposure with or without exercise. Because the effects of altitude and exercise may be synergistic rather than additive, and because individual altitude tolerance and exercise capacity cannot be reliably determined at sea level, advice should err on the side of caution by not allowing for the substantial safety margins by which pregnancies are probably protected. An altitude of 2,500 m (8,250 ft) should not be exceeded in the first 4 to 5 days of short-term exposure. If exercise is performed directly after exposure, this should take place at correspondingly lower altitude, especially in the first few days. Compounding risks, eg, maternal smoking, anemia or fetal growth retardation, must be carefully excluded.

Adaptation, Physiological↗
PubMed2005

Chronoecological health watch of arterial stiffness and neuro-cardio-pulmonary function in elderly community at high altitude (3524 m), compared with Japanese town.

Effects of high altitude on arterial stiffness and neuro-cardio-pulmonary function were studied. Blood pressure (BP) and heart rate (HR) were measured in a sitting position on resting Ladakhis, living at an altitude of 3250-4647 m (Phey village, 3250 m: 17 men and 55 women; Chumathang village, 4193 m: 29 men and 47 women; Sumdo village, 4540 m: 38 men and 57 women; and Korzok village, 4647 m: 84 men and 70 women). The neuro-cardio-pulmonary function, including the Kohs block design test, the Up and Go, the Functional Reach and the Button tests, was examined in 40 elderly subjects (19 men and 21 women, mean age: 74.7 +/- 3.3 years) in Leh, Ladakh (altitude: 3524 m), for comparison with 324 elderly citizens (97 men and 227 women, mean age: 80.7 +/- 4.7 years) of Tosa, Japan (altitude: 250 m). Cardio-Ankle Vascular Index (CAVI) was measured as the heart-ankle pulse wave velocity (PWV) in these subjects using a VaSera CAVI instrument (Fukuda Denshi, Tokyo). SpO(2) decreased while Hb and diastolic BP increased with increasing altitude. At higher altitude, residents were younger and leaner. Women in Leh vs. Tosa had a poorer cognitive function, estimated by the Kohs block design test (3.7 +/- 3.6 vs. 16.4 +/- 9.6 points, P < 0.0001) and poorer ADL functions (Functional Reach: 13.7 +/- 7.0 cm vs. 25.3 +/- 8.7 cm, P < 0.0001; Button test: 22.5 +/- 4.8 vs. 14.8 +/- 5.7 s, P < 0.0001). Time estimation was shorter at high altitude (60-s estimation with counting: 41.1% shorter in men and 23.0% shorter in women). A higher voltage of the QRS complex was observed in the ECG of Leh residents, but two times measurement of CAVI showed no statistically significant differences between Leh and Tosa (two times of CAVI measures; 9.49 vs. 10.01 m/s and 9.41 vs. 10.05 m/s, respectively), suggesting that most residents succeed to adapt sufficiently to the high-altitude environment. However, correlation of CAVI with age shows several cases who show an extreme increase in CAVI. Thus, for the prevention of stroke and other adverse cardiovascular outcomes, including dementia, CAVI may be very useful, especially at high altitude. In conclusion, elderly people living at high altitude have a higher risk of cardiovascular disease than low-latitude peers. To determine how these indices are associated with maintained cognitive function deserves further study by the longitudinal follow-up of these communities in terms of longevity and aging in relation to their neuro-cardio-pulmonary function.

Adolescent↗