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At least 145 records · Page 8Linked to original sources
PubMed2006

Outcome after femoral shaft fractures in the elderly: the effects of altitude.

BACKGROUND: A paucity of knowledge currently exists surrounding the effects of altitude on femur fracture outcomes. The purpose of this study was to determine if altitude plays a significant role in determining the outcome of femoral shaft fractures in the elderly. The authors hypothesized that the additional cardiopulmonary stress of altitude would promote poorer outcomes of those individuals treated at high altitude, especially those individuals whose home residence was located at low altitude. METHODS: Medicare part A claims data between 1996 and 2000 were searched and patients with open or closed femoral shaft fractures were identified for the study. The treatment altitude and home residence altitude for each patient was recorded by cross-matching Zip Code information provided in the Medicare part A database with a database providing altitude data by Zip Code. The patients were grouped both by the altitude of treatment and by the difference between the altitude of residence and the altitude of treatment. The data was analyzed for outcome measurements. RESULTS: The claims data search identified 30,168 patients for the study. For the entire sample, the in-hospital mortality was 4.2%, 30-day mortality was 8.3%, 1-year mortality was 26.3%, and complication rate was 5.7%. Length of stay results demonstrated that patients treated at medium or high altitude had statistically shorter lengths of stay than those treated at low altitude (p < 0.01). Mortality rates and complications were not statistically different for those treated at high, medium, or low altitude with the exception of a slightly lower in-hospital mortality in the medium treatment altitude group (p = 0.04). Additionally, those patients who resided more than 1000 ft below the treatment altitude had shorter lengths of stay than those who resided more than 1000 ft above the treatment altitude (p < 0.01). Those patients who lived within 1000 ft of the treatment hospital or more than 1000 ft below the treatment hospital had fewer days in the intensive care unit (p < 0.01, p = 0.01; respectively). CONCLUSIONS: Femoral shaft fractures treated at altitude were not associated with increased morbidity and mortality as compared to femoral shaft fractures treated at low altitude. Additionally, patients residing at low altitude and treated at high altitude did not suffer increased morbidity or mortality.

Aged↗
PubMed2002

Adrenopause or decline of serum adrenal androgens with age in women living at sea level or at high altitude.

The present study aimed to determine adrenopause or reduction of serum adrenal androgens with age at high altitude and at sea level. It was a cross-sectional study performed in 210 women resident at high altitude (4340 m) and 123 women living in Lima (150 m), aged 20-70 years. Fasting early morning blood samples were obtained. Serum dehydroepiandrosterone (DHEA), DHEA sulphate (DHEAS), androstenedione, testosterone and estradiol were measured by radioimmunoassay. Serum testosterone concentrations were greater in women living at high altitude than in those resident at sea level. Serum concentrations of DHEA, DHEAS and androstenedione were lower in women living at high altitude than in those living at sea level. The DHEAS/DHEA ratio was significantly greater, and the androstenedione/testosterone ratio was lower in samples from women living at high altitude. Among women older than 50 years of age, a greater decline in serum concentrations of DHEA was observed in those living at high altitude than in those living at sea level. Among women 60-70 years of age, serum concentrations of DHEA at high altitude were 46.9% of those in women of the same age living at sea level. Decay of DHEAS at sea level and at high altitude occurred from the age of 40 years. The decline was faster at high altitude than at sea level, and in women aged 60-70 years serum values of DHEAS at high altitude were 56% of those at sea level. In the same age group, serum concentrations of androstenedione among those native to high altitudes were 27.34% of the value at sea level. At sea level, serum testosterone concentrations did not change with age from 20 to 70 years. In women aged 20-39 years and 50-59 years, serum testosterone concentrations were greater at high altitude than at sea level (P<0.05). In those aged 60-70 years, the concentrations were similar in those living at sea level and at high altitude. At sea level and at high altitude, the serum testosterone/estradiol ratio increased with age (P<0.0034 and P<0.0001 respectively). This ratio increased at an earlier age among those living at high altitude (40-49 years) than among those living at sea level (50-59 years). Multivariate analysis showed that altitude (P<0.0001) and greater chronological age (P<0.001) were associated with lower serum DHEAS concentrations. DHEAS was related to chronological age (P<0.0001). Low serum androstenedione concentrations were related to living at high altitude at birth and greater chronological age (P<0.0001). In conclusion, adrenopause is attained earlier and is of greater magnitude at high altitude than at sea level.

Adrenal Glands↗
PubMed1997

Physiological implications of altitude training for endurance performance at sea level: a review.

Acclimatisation to environmental hypoxia initiates a series of metabolic and musculocardio-respiratory adaptations that influence oxygen transport and utilisation, or better still, being born and raised at altitude, is necessary to achieve optimal physical performance at altitude, scientific evidence to support the potentiating effects after return to sea level is at present equivocal. Despite this, elite athletes continue to spend considerable time and resources training at altitude, misled by subjective coaching opinion and the inconclusive findings of a large number of uncontrolled studies. Scientific investigation has focused on the optimisation of the theoretically beneficial aspects of altitude acclimatisation, which include increases in blood haemoglobin concentration, elevated buffering capacity, and improvements in the structural and biochemical properties of skeletal muscle. However, not all aspects of altitude acclimatisation are beneficial; cardiac output and blood flow to skeletal muscles decrease, and preliminary evidence has shown that hypoxia in itself is responsible for a depression of immune function and increased tissue damage mediated by oxidative stress. Future research needs to focus on these less beneficial aspects of altitude training, the implications of which pose a threat to both the fitness and the health of the elite competitor. Paul Bert was the first investigator to show that acclimatisation to a chronically reduced inspiratory partial pressure of oxygen (P1O2) invoked a series of central and peripheral adaptations that served to maintain adequate tissue oxygenation in healthy skeletal muscle, physiological adaptations that have been subsequently implicated in the improvement in exercise performance during altitude acclimatisation. However, it was not until half a century later that scientists suggested that the additive stimulus of environmental hypoxia could potentially compound the normal physiological adaptations to endurance training and accelerate performance improvements after return to sea level. This has stimulated an exponential increase in scientific research, and, since 1984, 22 major reviews have summarised the physiological implications of altitude training for both aerobic and anaerobic performance at altitude and after return to sea level. Of these reviews, only eight have specifically focused on physical performance changes after return to sea level, the most comprehensive of which was recently written by Wolski et al. Few reviews have considered the potentially less favourable physiological responses to moderate altitude exposure, which include decreases in absolute training intensity, decreased plasma volume, depression of haemopoiesis and increased haemolysis, increases in sympathetically mediated glycogen depletion at altitude, and increased respiratory muscle work after return to sea level. In addition, there is a risk of developing more serious medical complications at altitude, which include acute mountain sickness, pulmonary oedema, cardiac arrhythmias, and cerebral hypoxia. The possible implications of changes in immune function at altitude have also been largely ignored, despite accumulating evidence of hypoxia mediated immunosuppression. In general, altitude training has been shown to improve performance at altitude, whereas no unequivocal evidence exists to support the claim that performance at sea level is improved. Table 1 summarises the theoretical advantages and disadvantages of altitude training for sea level performance. This review summarises the physiological rationale for altitude training as a means of enhancing endurance performance after return to sea level. Factors that have been shown to affect the acclimatisation process and the subsequent implications for exercise performance at sea level will also be discussed. Studies were located using five major database searches, which included Medline, Embase, Science Citation Index, Sports Discus, and Sport, in

Acclimatization↗
PubMed2000

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.

Acclimatization↗
PubMedDate not supplied

Growth of Han migrants at high altitude in central Asia.

Han Chinese of low-altitude descent have been living in Qinghai Province of Western China for at least two millennia. For most of this time they have lived at elevations under 2,500 m. However, during the last four decades an increasing number of Han have moved into high-altitude towns at elevations over 3,000 m, and some above 4,000 m. There are now sufficient numbers of Han descendants who have been born and raised at high altitude to allow a comparison of their morphological and physiological growth patterns with low-altitude Han to detect the effect of hypoxia. The field study reported here was conducted by collaborating Chinese and American researchers over a 6-year period, and included 1,227 Han living at high altitude in Qinghai and at low altitude near Beijing. This study demonstrates that Han born and raised at high altitude are smaller and lighter than those at low altitude-particularly as children and adolescents. Slower growth at high altitude may be a consequence of hypoxia, but it also corresponds to poorer economic conditions in rural Qinghai Province, and thus may reflect nutritional inadequacies. Differences in altitude and/or nutrition do not seem to affect thorax dimensions, since, relative to stature, chest dimensions are similar at both high and low altitudes. Nevertheless, lung volumes are higher among Han at high altitude, possibly reflecting the influence of hypoxia on alveolar growth. The hematological values of Han growing up at 3,200 m are not different from those at low altitude-an unusual finding relative to other low-altitude groups that may reflect population differences in response to hypoxia. At 3,800 m and 4,300 m, however, Han show elevated hemoglobin relative to Han at low altitude.

Adolescent↗
PubMed1995

Developmental, genetic, and environmental components of aerobic capacity at high altitude.

The aerobic capacity of 268 subjects (158 males and 110 females) was evaluated in La Paz, Bolivia situated at 3,750 m. The sample included 1) 39 high altitude rural natives (all male); 2) 67 high altitude urban natives (32 male, 35 female); 3) 69 Bolivians of foreign ancestry acclimatized to high altitude since birth (37 male, 32 female); 4) 50 Bolivians of foreign ancestry acclimatized to high altitude during growth (25 male, 25 female); and 5) 42 non-Bolivians of either European or North American ancestry acclimatized to high altitude during adulthood (25 male, 18 female). Data analyses indicate that 1) high altitude urban natives, acclimatized to high altitude since birth or during growth, attained higher aerobic capacity than subjects acclimatized to high altitude during adulthood; 2) age at arrival to high altitude is inversely related to maximum oxygen consumption (VO2 max) expressed in terms L/min or ml/min/kg of lean body mass, but not in terms of ml/min/kg of body weight; 3) among subjects acclimatized to high altitude during growth, approximately 25% of the variability in aerobic capacity can be explained by developmental factors; 4) as inferred from evaluations of skin color reflectance and sibling similarities, approximately 20 to 25% of the variability in aerobic capacity at high altitude can be explained by genetic factors; 5) except among the non-Bolivians acclimatized to high altitude during adulthood, the aerobic capacity of individuals with high occupational activity level is equal to the aerobic capacity of high altitude rural natives; and 6) the relationship between occupational activity level and aerobic capacity is much greater among subjects acclimatized to high altitude before the age of 10 years than afterwards. Together these data suggest that the attainment of normal aerobic capacity at high altitude is related to both developmental acclimatization and genetic factors but its expression is highly mediated by environmental factors, such as occupational activity level and body composition.

Acclimatization↗
PubMed2000

Effect of altitude training on serum creatine kinase activity and serum cortisol concentration in triathletes.

In this investigation we evaluated the effect of a 5-week training program at 1860 m on serum creatine kinase (CK) activity and serum cortisol concentration in national-caliber triathletes for the purpose of monitoring the response to training in a hypobaric hypoxic environment. Subjects included 16 junior-level female (n = 8) and male (n = 8) triathletes who were training for the International Triathlon Union (ITU) World Championships. After an initial acclimatization period, training intensity and/or volume were increased progressively during the 5-week altitude training camp. Resting venous blood samples were drawn at 0700 hours following a 12-h overnight fast and were analyzed for serum CK activity and serum cortisol concentration. Subjects were evaluated before [7-10 days pre-altitude (SL 1)] and after [7-10 days post-altitude (SL 2)] the 5-week training camp at 1860 m. At altitude, subjects were evaluated within 24-36 h after arrival (ALT 1), 7 days after arrival (ALT 2), 18 days after arrival (ALT 3), and 24-36 h prior to leaving the altitude training camp (ALT 4). A repeated-measures analysis of variance was used to evaluate differences over time from SL 1 to SL 2. Compared to SL 1, serum CK activity increased approximately threefold (P < 0.05) within the initial 24-36 h at altitude (ALT 1), and increased by an additional 70% (P < 0.05) after the 1st week of altitude training (ALT 2). Serum CK activity remained significantly elevated over the duration of the experimental period compared to pre-altitude baseline levels. Serum cortisol concentration was increased (P < 0.05) at the end of the 5-week altitude training period (ALT 4) relative to SL 1, ALT 1 and ALT 3. These data suggest that: (1) the initial increase in serum CK activity observed in the first 24-36 h at altitude was due primarily to acute altitude exposure and was independent of increased training intensity and/or training volume, (2) the subsequent increases in serum CK activity observed over the duration of the 5-week altitude camp were probably due to the combined effects of altitude exposure and increased training load, and (3) the increase in serum cortisol concentration observed at the end of the altitude training camp reflects the additive effect of 5 weeks of altitude exposure in combination with a progressively increased training intensity and/or volume.

Adolescent↗
PubMed1996

Hormone profile during the menstrual cycle at high altitude.

OBJECTIVES: To determine the hormone profile during the menstrual cycle in women at sea level and at high altitude, and whether the time between the gonadotropin peak and ovulation is different at high altitude from that at sea level. METHODS: The study was carried out in Lima (150 m) and Cerro de Pasco (4340 m), Peru. The hormone profile of 10 adult regularly menstruating women at sea level and 10 women at high altitude was assessed. Ovulation was identified by vaginal ultrasonography. RESULTS: The pre-ovulatory follicle diameter was lower (P < 0.001) at high altitude than at sea level. Ovulation after LH peak occurred earlier at high altitude than at sea level. Serum FSH levels were higher at late luteal phase and early follicular phase at high altitude than at sea level (P < 0.05). The serum LH and FSH peaks were similar in women at sea level and at high altitude. During the early follicular phase serum estradiol levels were significantly higher at high altitude than at sea level (P < 0.05). During the late follicular phase the production of estradiol was higher at sea level than at high altitude (P < 0.05). The peak of serum estradiol was at day -1 in Lima and in day 0 at high altitude. At ovulation, the serum estradiol levels in women at sea level were 55.1% of the peak, but remained at high levels (80% of the peak) in women at high altitude (P < 0.05). The second increase of serum estradiol occurred earlier at sea level than at high altitude. From days +12 to +15, there was a significant decline in serum estradiol levels in women at sea level (P < 0.05) but not in those from high altitude (P > 0.05). Serum progesterone levels at days +5, and +8 to +12 were significantly higher at sea level than at high altitude. CONCLUSION: Our data suggest that hormone profile during menstrual cycle is different at high altitude than at sea level, probably as an effect of low barometric pressure.

Altitude↗
PubMed1995

Selenium levels and glutathione peroxidase activities in blood in an andean high-altitude population.

Selenium (Se) levels in blood (whole blood, erythrocytes and serum) and blood glutathione peroxidase (GSH-Px) activity were investigated in people living at high altitude in Bolivia (4,000 m above sea level). These parameters were compared to those of people living at low altitude (300 m above sea level). The Se levels in whole blood of the high-altitude subjects did not differ significantly from those of the low-altitude subjects. However, the Se levels in erythrocytes were significantly lower in the high-altitude subjects than in the low-altitude subjects, whereas serum Se levels were higher in the high-altitude subjects than in the low-altitude subjects. GSH-Px activity (Unit/g Hb) was significantly lower in the high-altitude subjects than in the low-altitude subjects. The mean corpuscular Hb concentration (MCHC), an indicator of the age of erythrocytes, in the high-altitude subjects was significantly higher than in the low-altitude subjects. These results show that the GSH-Px activity in the blood of the high-altitude subjects is relatively low. This may be due to their aged erythrocytes and/or to relatively low Se intake in the high-altitude population compared with low-altitude population.

Adolescent↗
PubMed1990

Perception of near earth altitudes by pilots: ascending vs. descending over both a land and water surface.

Thirteen experienced HH-3 pilots were tested on their ability to obtain four target altitudes between 25 and 200 ft. The target altitudes were attempted by both ascending from 0 ft and descending from 500 ft. Subjects were tested both over a land and water surface for a total of 16 recorded achieved altitudes per pilot. The pilots had full aircraft control but were without use of altimeters. Subjects showed wide variation for each test situation with some achieved altitudes exceeding the target altitude by 100% while others were below the target altitude. The predominant error was an achieved altitude greater than the target altitude. The mean achieved altitude when descending to a given target altitude exceeded the mean achieved altitude when ascending to the same target altitude. There was no statistically significant difference in mean achieved altitude between land and water surfaces. In conclusion, this study revealed that even experienced pilots may not estimate with good accuracy their altitude in the near Earth environment. The error in altitude perception is of concern for safe ground clearance.

Accidents, Aviation↗
PubMed1997

[Sleep and respiration at an altitude of 6,400 m (Aconcagua, Argentina].

UNLABELLED: Persons at extreme altitudes are known to experience disturbances in the regulation of ventilation and sleep structure. However, except for simulated studies using the decompression chamber, only single events of sleep or ventilation were measured so far in field studies up to an altitude of 5800 m. Modifying a portable sleep lab (Vitalog HMS 5000), we were able to conduct 7 channel polygraphy on our ascent to the Aconcagua up to an altitude of 6400 m. METHODS: In 6 climbers (age 38-62 y, 1 f, 6 m), ECG, EOG, SaO2, chest and abdominal movements, breathing and snoring sounds, body position, nasal and oral airflow were measured 4 weeks prior to the expedition at an altitude of 500 m, at base camp (4200 m) and in 3 climbers at 6400 m (2nd base camp) at the Aconcagua mountain. All participants had a repeat study at 500 m altitude 4 weeks after the expedition. RESULTS: The total number of obstructive apnoeas and hypopnoeas (OA/H) at night increased at an altitude of 4200 m in the mean of all 6 climbers from 36 to 67.7 compared to 500 m altitude, Central Apneas and Cheyne stokes (CA/CS) increased from 6.7 to 45.2. At 6400 m altitude the OA/H fell to 3 and 4 respectively in 2 climbers and CA to 1 and 2 respectively. In one climber, suffering from recurrent snoring with oxygen desaturation at 500 m altitude level, the number of OA/H and CA/CS increased further to 201 and 322, respectively, at 6400 m. Total sleep time including the REM position increased in all 6 climbers by 10% at base camp in comparison to an altitude of 500 m. Whereas the total sleep time remained constant in the 3 climbers at 6400 m altitude, the REM position declined by 10% in comparison to base camp (4200 m). However, significant fluctuations between individuals were noticed. CONCLUSION: Although significant alterations in sleep and breathing are noticeable at altitudes above 300 m, the respiratory drive in healthy subjects provides for a regular ventilation at high frequency at the extreme altitude above 6000 m. Sleep-related breathing disturbances at low altitude appear to be amplified at high altitudes.

Adult↗
PubMed1997

Full-term birth weight and placental morphology at high and low altitude.

OBJECTIVE: To study the association between placental morphology and full-term birth weight at high and low altitude. SUBJECTS: Twenty normal pregnant women living permanently at high altitude (3100 m) and 20 normal pregnant women living permanently at low altitude (500 m) in Southern Saudi Arabia. METHOD: For each subject in the two groups the mean hemoglobin concentration and hematocrit values throughout pregnancy were estimated and these were used as indices for maternal hypoxia. After delivery, the birth weight of each fetus was determined together with the placental weight. Placentas were then examined histologically using sections stained by periodic acid-Schiff and hematoxylin-eosin. The mean percentages of villi with syncytial knots, cytotrophoblastic cells and fetal capillaries were determined. RESULTS: The mean hemoglobin concentration and hematocrit values were significantly greater at high altitude than at low altitude (P < 0.001 for both). The mean birth weight and placental weight were significantly greater at low altitude compared to high altitude (P < 0.025 and 0.001, respectively). The placentas from high altitude showed histological changes suggestive of placental hypoxia i.e. significant increase in the incidence of syncytial knots, cytotrophoblastic cells and fetal capillaries at high altitude compared to low altitude (P < 0.005, 0.001 and < 0.05, respectively). At both high and low altitude the incidences of syncytial knots and cytotrophoblastic cells showed positive and significant correlations with mean maternal hemoglobin (r = 0.5 and 0.6, P < 0.01 and < 0.001, respectively) and hematocrit (r = 0.5 and 0.6, P < 0.01 and 0.001, respectively) during pregnancy and negative and significant correlations with fetal birth weight (r = -0.4 and -0.6, P < 0.01 and P < 0.001, respectively). CONCLUSION: The low birth weight observed at high altitude compared to low altitude appeared to be mainly secondary to placental hypoxia resulting from maternal hypoxia which in turn was caused by high altitude hypoxia.

Altitude↗