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PubMed2005

Sleep disturbance at simulated altitude indicated by stratified respiratory disturbance index but not hypoxic ventilatory response.

At high altitudes, the clinically defined respiratory disturbance index (RDI) and high hypoxic ventilatory response (HVR) have been associated with diminished sleep quality. Increased RDI has also been observed in some athletes sleeping at simulated moderate altitude. In this study, we investigated relationships between the HVR of 14 trained male endurance cyclists with variable RDI and sleep quality responses to simulated moderate altitude. Blood oxygen saturation (SpO2%), heart rate, RDI, arousal rate, awakenings, sleep efficiency, rapid eye movement (REM) sleep, non-REM sleep stages 1, 2 and slow wave sleep as percentages of total sleep time (%TST) were measured for two nights at normoxia of 600 m and one night at a simulated altitude of 2,650 m. HVR and RDI were not significantly correlated with sleep stage, arousal rate or awakening response to nocturnal simulated altitude. SpO2 was inversely correlated with total RDI (r = -0.69, P = 0.004) at simulated altitude and with the change in arousal rate from normoxia (r = -0.65, P = 0.02). REM sleep response to simulated altitude correlated with the change, relative to normoxia, in arousal (r = -0.63, P = 0.04) and heart rate (r = -0.61, P = 0.04). When stratified, those athletes at altitude with RDI >20 h(-1) (n = 4) and those with <10 h(-1) (n = 10) exhibited no difference in HVR but the former had larger falls in SpO2 (P = 0.05) and more arousals (P = 0.03). Neither RDI (without stratification) nor HVR were sufficiently sensitive to explain any deterioration in REM sleep or arousal increase. However, the stratified RDI provides a basis for determining potential sleep disturbance in athletes at simulated moderate altitude.

Adult↗
PubMed2000

Comparative human ventilatory adaptation to high altitude.

Studies of ventilatory response to high altitudes have occupied an important position in respiratory physiology. This review summarizes recent studies in Tibetan high-altitude residents that collectively challenge the prior consensus that lifelong high-altitude residents ventilate less than acclimatized newcomers do as the result of acquired 'blunting' of hypoxic ventilatory responsiveness. These studies indicate that Tibetans ventilate more than Andean high-altitude natives residing at the same or similar altitudes (PET[CO(2)]) in Tibetans=29.6+/-0.8 vs. Andeans=31.0+/-1.0, P<0.0002 at approximately 4200 m), a difference which approximates the change that occurs between the time of acute hypoxic exposure to once ventilatory acclimatization has been achieved. Tibetans ventilate as much as acclimatized newcomers whereas Andeans ventilate less. However, the extent to which differences in hypoxic ventilatory response (HVR) are responsible is uncertain from existing data. Tibetans have an HVR as high as those of acclimatized newcomers whereas Andeans generally do not, but HVR is not consistently greater in comparisons of Tibetan versus Andean highland residents. Human and experimental animal studies demonstrate that inter-individual and genetic factors affect acute HVR and likely modify acclimatization and hyperventilatory response to high altitude. But the mechanisms responsible for ventilatory roll-off, hyperoxic hyperventilation, and acquired blunting of HVR are poorly understood, especially as they pertain to high-altitude residents. Developmental factors affecting neonatal arterial oxygenation are likely important and may vary between populations. Functional significance has been investigated with respect to the occurrence of chronic mountain sickness and intrauterine growth restriction for which, in both cases, low HVR seems disadvantageous. Additional studies are needed to address the various components of ventilatory control in native Tibetan, Andean and other lifelong high-altitude residents to decide the factors responsible for blunting HVR and diminishing ventilation in some native high-altitude residents.

Acclimatization↗
PubMed2001

Safe upper limits for oxygen enrichment of room air at high altitude.

Oxygen enrichment of room air at high altitude has been shown to improve mental performance, sleep quality, and work capacity. Until now, the usual strategy has been to use an oxygen concentration that reduces the equivalent altitude to about 3,000 m, where the equivalent altitude is that which gives the same inspired PO2 during air breathing. However, standards adopted by the National Fire Protection Association allow considerably higher oxygen concentrations without introducing a fire hazard. For example, by raising the oxygen concentration to 31.5% at an altitude of 5,000 m, the equivalent altitude can be safely reduced to less than 2,000 m. At the extreme altitude of 8,000 m, the equivalent altitude can be reduced to less than 4,000 m without increasing the fire hazard. These increased levels of oxygen enrichment are feasible in practice using oxygen concentrators. They may be useful if lowlanders need to ascend rapidly and stay at high altitude, or for treating people with high altitude illnesses.

Air↗
PubMed2005

Consensus statement on chronic and subacute high altitude diseases.

This is an international consensus statement of an ad hoc committee formed by the International Society for Mountain Medicine (ISMM) at the VI World Congress on Mountain Medicine and High Altitude Physiology (Xining, China; 2004) and represents the committee's interpretation of the current knowledge with regard to the most common chronic and subacute high altitude diseases. It has been developed by medical and scientific authorities from the committee experienced in the recognition and prevention of high altitude diseases and is based mainly on published, peer-reviewed articles. It is intended to include all legitimate criteria for choosing to use a specific method or procedure to diagnose or manage high altitude diseases. However, the ISMM recognizes that specific patient care decisions depend on the different geographic circumstances involved in the development of each chronic high altitude disease. These guidelines are established to inform the medical services on site who are directed to solve high altitude health problems about the definition, diagnosis, treatment, and prevention of the most common chronic high altitude diseases. The health problems associated with life at high altitude are well documented, but health policies and procedures often do not reflect current state-of-the-art knowledge. Most of the cases of high altitude diseases are preventable if on-site personnel identify the condition and implement appropriate care.

Acclimatization↗
PubMed2006

Ataxia: an early indicator in high altitude cerebral edema.

Wu, Tianyi, Shouquan Ding, Jinliang Liu, Jianhou Jia, Ruichen Dai, Baozhu Liang, Jizhui Zhao, and Detang Qi. Ataxia: an early indicator in high altitude cerebral edema. High Alt. Med. Biol. 7:275-280, 2006.--As a result of industrial development in the western region of China, in 2001 the Chinese government decided to build Qinghai-Tibetan Railway. The new railroad stretches 1118 km from Golmud (2808 m) to Lhasa (3658 m), with more than three-quarter of the distance above 4000 m, through the Mt. Kun Lun and Tanggula ranges. From the beginning of the project on June, 29, 2001, to the end of the year of 2003, about 74,735 construction workers worked in the harsh climate, in adverse circumstances and a low-barometric-pressure environment. The construction provided an opportunity for the investigation and study of acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE). These altitude illnesses were very common in the construction workers. From July 1, 2001, to October 31, 2003, the overall incidence of AMS, HAPE, and HACE in the total workers was approximately 45%-95%, 0.49%, and 0.26%, respectively. Altitude illnesses were studied at two hospitals near the construction site. One hospital is located on the Fenghuoshan (Mt. Wind-gap) at an altitude of 4779 m (PB 428 torr), and the second hospital is situated in the Kekexili area at an altitude of 4505 m (PB 440 torr). Kekexili is a sparsely populated zone because the weather conditions are very bad all year round. These two hospitals received patients from the construction sites, where workers were working at altitudes between 4464 and 4905 m. A total of 8014 workers were treated at Fenghuoshan and 5488 were in Kekexili over the past 3 years. According to local guidance about proper medical care, workers ascending to high altitude should be examined physically, complete an AMS questionnaire, and be monitored for ataxia as an early warning sign of the impending, more serious aspects of HACE. The onset of HACE is frequently characterized by an ataxic gait, as reported since the middle of the 20th century (Gray et al., 1971; Wilson, 1973; Houston and Dickinson, 1975; Dickinson, 1979; Clarke, 1988; Hackett and Oelz, 1992; Hackett, 2002; Hackett and Roach, 2004). However, there are no detailed analyses of ataxia in HACE. This paper considers the relation between ataxia and HACE and its frequency, significance, and importance.

Altitude↗
PubMed1997

Effect of high-altitude exposure in the elderly: the Tenth Mountain Division study.

BACKGROUND: More than 5 million people/year over age 60 visit high altitude, which may exacerbate underlying cardiac or pulmonary disease. We hypothesized that the elderly would exhibit an impaired functional capacity at altitude, with increased myocardial ischemia compared with sea level (SL). METHODS AND RESULTS: Twenty veterans (68+/-3 years) were studied at (1) SL, (2) acute simulated altitude to 2500 m, and (3) after 5 days of acclimatization to 2500 m. With acute altitude, PaO2 and oxyhemoglobin saturation decreased and pulmonary artery pressure increased 43%, associated with sympathetic activation. VO2peak decreased 12% acutely but normalized after acclimatization. The best predictor of VO2peak with acute altitude was VO2peak at SL (r=.94). The double product that induced 1-mm ST depression during exercise with acute altitude was 5% less than SL but normalized after acclimatization. One patient with severe coronary disease sustained a myocardial infarction after an exercise test. CONCLUSIONS: Moderate altitude exposure in the elderly is associated with hypoxemia, sympathetic activation, and pulmonary hypertension resulting in a reduced exercise capacity that is predictable based on exercise performance at SL. Patients with coronary artery disease who are well compensated at SL do well at moderate altitude, although acutely ischemia may be provoked at modestly lower myocardial and systemic work rates. The elderly acclimatize well with normalization of SL performance after 5 days. A prudent policy would be for elderly individuals, particularly those with coronary artery disease, to limit their activity during the first few days at altitude to allow this acclimatization process to occur.

Age Factors↗
PubMed2004

High altitude impairs nasal transepithelial sodium transport in HAPE-prone subjects.

High-altitude pulmonary oedema (HAPE) occurs in predisposed individuals at altitudes >2,500 m. Defective alveolar fluid clearance secondary to a constitutive impairment of the respiratory transepithelial sodium transport contributes to its pathogenesis. Hypoxia impairs the transepithelial sodium transport in alveolar epithelial type II cells in vitro. If this impairment is also present in vivo, high-altitude exposure could aggravate the constitutive defect in sodium transport in HAPE-prone subjects, and thereby further facilitate pulmonary oedema. Therefore, the aim of the current study was to measure the nasal potential difference (PD) in 21 HAPE-prone and 29 HAPE-resistant subjects at low altitude and 30 h after arrival at high altitude (4,559 m). High-altitude exposure significantly decreased the mean +/- SD nasal PD in HAPE-prone (18.0 +/- 6.2 versus 12.5 +/- 6.8 mV) but not in HAPE-resistant subjects (25.6 +/- 9.4 versus 22.9 +/- 9.2 mV). This altitude-induced decrease was not associated with an altered amiloride-sensitive fraction, but was associated with a significantly lower amiloride-insensitive fraction of the nasal PD. These findings provide evidence in vivo that an environmental factor may impair respiratory transepithelial sodium transport in humans. They are consistent with the concept that in high-altitude pulmonary oedema-susceptible subjects, the combination of a constitutive and an acquired defect in this transport mechanism facilitates the development of pulmonary oedema during high-altitude exposure.

Adult↗
PubMed2003

Brief altitude exposure in New Zealand white rabbits (Oryctolagus cuniculus) does not produce elevated intracranial pressure.

OBJECTIVE: Our intent was to observe the effect of simulated altitude exposure on the intracranial pressure (ICP) of New Zealand white rabbits. It is theorized that the hypoxia of high altitude causes a rise in ICP, which may play a role in the pathogenesis of acute mountain sickness (AMS). Dexamethasone is a medication used to treat AMS, but its mechanism of action in this disease is unknown. It is believed that dexamethasone may lower ICP and thereby relieve the symptoms of AMS, but to our knowledge no study has demonstrated the effect dexamethasone has on ICP during altitude exposure. METHODS: We placed subdural ICP catheters in 10 rabbits and then placed the rabbits in an altitude chamber at simulated 5000 m for 6 hours. Each rabbit was exposed to simulated altitude twice, once after several doses of dexamethasone and once after several doses of saline (placebo). We followed ICP measurements throughout the altitude chamber flights, comparing baseline with 6-hour ICP levels. RESULTS: After 6 hours of altitude exposure, there was no significant change in the ICP of rabbits with either saline or dexamethasone administration. We were unable to replicate the altitude-induced rise in ICP observed in other animal studies. CONCLUSIONS: Intracranial pressure does not rise within the subdural space in rabbits during altitude exposures of 6 hours or less. Further, we are unable to draw conclusions regarding the mechanism of action of dexamethasone in the cerebral dynamics of AMS.

Altitude↗
PubMed2004

[A study of high altitude environment affecting on worker's health during the constructing Qinghai-Xizang railway].

OBJECTIVE: To study high altitude environment affecting on worker's health METHODS: Using the cohort study, the altitude reaction was investigated and the WBC, RBC, Hb and oxygenation indexes were measured on workers in several periods, namely, acclimatization period, initially arrived high altitude and resident 90 days. RESULTS: The 83.3% of men had altitude reactions with different kinds at initially arrived high altitude. The headache was the most. The rate of abnormal blood pressure increased with altitude and resident time (P < 0.01). The rate of 90 day's group was 41.7%. The rise of diastole pressure was obvious (P < 0.01). As the beginning of arrived highland, the increase of WBC, RBC were significant (P < 0.01). The increase of Hb appeared only in 90 day's group. The level of malondialdehyde (MDA) obviously increased during acclimatization period and increased with altitude and resident time (P < 0.01). The activity of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) increased significantly in 90 day's group [(222.36 +/- 36.52) x 10(3) U/L, (158.49 +/- 14.42) U/L, (45.74 +/- 8.31) NU/ml respectively] (P < 0.01). CONCLUSION: The high altitude environment may result in the abnormal blood pressure, the rise of diastolic pressure was important. It lead to the increase of WBC, RBC, Hb. It initiated activity of oxygenation reaction. The symptoms of headache, dizziness, loss of appetite and insomnia appeared as working in high altitude environment.

Acclimatization↗
PubMed1995

Diving at altitude: a review of decompression strategies.

Diving at altitude requires different tables from those at sea level due to the reduction in surface ambient pressure. Several algorithms extrapolating sea-level diving experimental data have been proposed to construct altitude diving tables. The rationale for these algorithms is reviewed together with the conservatism of the resulting tables and decompression computer outputs. All algorithms are based on the adaptation of critical tissue tensions to altitude. These are linear extrapolation (LEM), constant ratio translation (CRT), and constant ratio extrapolation (CRE) of maximum permissible tissue tensions (M values). Either new tables using the altitude-adapted M values were put forward or sea-level tables are to be used through an operation called correction. In this review it is shown that for a given set of M values, CRT and CRE give the same result for no-decompression-stop dives; they always yield more conservative results than LEM. When decompression stops are used, CRT is more conservative than CRE. When applied to different sets of M values, the conservatism becomes a function of bottom time, depth, and altitude. The analysis shows that the tables derived using CRT of U.S. Navy (USN) schedules and CRE Boni et al. tables give more conservative results than LEM Bühlmann tables for higher altitude, longer bottom time, and deeper dives. Aviation altitude exposure decompression sickness (DCS) data are also addressed to compare different model outputs. When applied to USN and Royal Navy tables, LEM yields an altitude DCS limit of 8,581 and 8,977 m, respectively. On the other hand, the altitude limit calculated using CRE applied to USN M values and LEM Bühlmann tables is found to be below 6,000 m.

Aerospace Medicine↗
PubMed1999

Developmental components of resting ventilation among high- and low-altitude Andean children and adults.

This paper evaluates the age-associated changes of resting ventilation of 115 high- and low-altitude Aymara subjects, of whom 61 were from the rural Aymara village of Ventilla situated at an average altitude of 4,200 m and 54 from the rural village of Caranavi situated at an average altitude of 900 m. Comparison of the age patterns of resting ventilation suggests the following conclusions: 1) the resting ventilation (ml/kg/min) of high-altitude natives is markedly higher than that of low-altitude natives; 2) the age decline of ventilation is similar in both lowlanders and highlanders, but the starting point and therefore the age decline are much higher at high altitude; 3) the resting ventilation that characterizes high-altitude Andean natives is developmentally expressed in the same manner as it is at low altitude; and 4) the resting ventilation (ml/kg/min) of Aymara high-altitude natives is between 40-80% lower than that of Tibetans.

Adaptation, Physiological↗
PubMed1984

The physical growth of urban children at high altitude.

The physical growth of urban Aymara children residing in La Paz, Bolivia (3,600 m) is described and compared with Amerindian children residing at low and high altitudes and with low-altitude U.S. children. The sample consists of 227 males (10.6-19.7 yr) and 219 females (11.2-19.8 yr). The urban La Paz children were taller at all ages than rural high altitude Amerindian children but similar in stature to urban high altitude children from Peru. The variation in stature among the high altitude populations was considerable, amounting to average differences between the tallest and shortest samples of about 10 cm in males and 8 cm in females. In addition, stature in the two urban high altitude samples was similar to that of rural low-altitude Amerindians. This overlapping of the distributions of stature in high- and low-altitude populations could easily confound comparisons designed to determine the effects of hypoxia on physical growth. La Paz Aymara children had considerably smaller chest sizes relative to stature than high-altitude Quechua children. However, the available data indicates that relative chest sizes are similar in Aymara and Quechua adults, suggesting that the process by which large chests are achieved may differ between these Andean populations.

Adolescent↗
PubMed1991

Maximal oxygen uptake and erythropoietic responses after training at moderate altitude.

Six well-trained male cross-county skiers trained for 7 days at 2700 m above sea level, their accommodation being at 1695 m. Blood samples for haemoglobin concentration [Hb], erythropoietin concentration [EPO] and reticulocyte count were collected before, during and after altitude exposure. Packed cell volume (PCV), red blood cell count (RBC), transferrin-iron saturation, mean red cell volume (MCV), mean corpuscular haemoglobin concentration (MCHC), maximal oxygen uptake, maximal achieved ventilation and heart rate were determined pre- and postaltitude exposure. The [EPO] increased significantly from pre-altitude (mean 36 mU.ml-1, SD 5) to maximal altitude values (mean 47 mU.ml-1, SD 3). The [Hb] had increased significantly above pre-altitude values (mean 8.8 mmol.l-1, SD 0.5) on day 2 (mean 9.1 mmol.l-1, SD 0.4) and day 7 (mean 9.4 mmol.l-1, SD 0.4) at altitude and on day 4 postaltitutde (mean 9.2 mmol.l-1, SD 0.4). The reticulocyte counts had increased significantly above pre-altitude values (mean 6%, SD 3%) on day 3 at altitude (mean 12%, SD 8%) and day 4 postaltitude (mean 10%, SD 5%). The RBC counts had increased on the 4th postaltitude day. The transferrin-iron saturation had decreased below pre-altitude values (mean 23%, SD 4%) on day 4 postaltitude (mean 14%, SD 5%) and had increased on day 11 postaltitude (mean 22%, SD 7%). There were no significant changes in MCV, MCHC, PCV, maximal oxygen uptake and maximal achieved ventilation, and heart rate pre- to postaltitude. These observations demonstrated an erythropoietic response to the altitude training which was not sufficient to increase the postaltitude maximal oxygen uptake.

Adolescent↗
PubMed1990

Studies on organ weights in naproxen treated rats after intermittent exposure to simulated high altitude.

Rats were exposed intermittently for 8 h per day over 6 days at simulated high altitude of 20,000 feet. One group of altitude-exposed animals was treated with naproxen, a prostaglandin inhibiting drug. Significant reduction in body weight gain was observed in both altitude-exposed and drug-treated altitude-exposed animals compared to the control group. Right and left ventricular weights and weights of the adrenal glands were increased significantly in altitude-exposed and altitude-exposed drug-treated animals. The weight of the spleen was increased significantly in altitude-exposed animals whereas no such increase of splenic weight was observed in drug-treated altitude-exposed group of animals. On the other hand, the weight of the liver was decreased significantly in both cases. In drug-treated altitude-exposed animals, the unaltered splenic weight was thought to be due to inhibition of the erythropoietic activity.

Acclimatization↗
PubMed1995

Free and total thyroid hormones in humans at extreme altitude.

Alterations in circulatory levels of total T4 (TT4), total T3 (TT3), free T4 (FT4), free T3 (FT3), thyrotropin (TSH) and T3 uptake (T3U) were studied in male and female sea-level residents (SLR) at sea level, in Armed forces personnel staying at high altitude (3750 m) for prolonged duration (acclimatized low-landers, ALL) and in high-altitude natives (HAN). Identical studies were also performed on male ALL who trekked to an extreme altitude of 5080 m and stayed at an altitude of more than 6300 m for about 6 months. The total as well as free thyroid hormones were found to be significantly higher in ALL and HAN as compared to SLR values. Both male as well as female HAN had higher levels of thyroid hormones. The rise in hormone levels in different ALL ethnic groups drawn from amongst the southern and northern parts of the country was more or less identical. In both HAN and ALL a decline in FT3 and FT4 occurred when these subjects trekked at subzero temperatures to extreme altitude of 5080 m but the levels were found to be higher in ALL who stayed at 6300 m for a prolonged duration. Plasma TSH did not show any appreciable change at lower altitudes but was found to be decreased at extreme altitude. The increase in thyroid hormones at high altitude was not due to an increase in hormone binding proteins, since T3U was found to be higher at high altitudes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed2003

Altitude is a phenotypic modifier in hereditary paraganglioma type 1: evidence for an oxygen-sensing defect.

Hereditary paraganglioma type 1 (PGL1) is characterized by slow-growing and vascularized tumors that often develop in the carotid body (CB) and is caused by mutations in the gene for succinate dehydrogenase D ( SDHD) of mitochondrial complex II. The mechanisms of tumorigenesis and the factors affecting penetrance and expressivity are unknown. Because chronic hypoxic stimulation at high altitudes causes sporadic CB paragangliomas, it has been hypothesized that the SDHD gene product may be involved in oxygen sensing. On this background, we examined genotype-phenotype-environment relationships and tested whether higher altitudes adversely affect the phenotype in PGL1. An analysis of 58 subjects from 23 families revealed that nonsense/splicing mutation carriers developed symptoms 8.5 years earlier than missense mutation carriers ( P<0.012). We also found that subjects who were diagnosed with single tumors at their first clinical evaluation lived at lower average altitudes and were exposed to lower altitude-years than those with multiple tumors ( P<0.012). Pheochromocytomas developed in six subjects (approximately 10%), five of whom had nonsense mutations ( P=0.052). Subjects with pheochromocytomas also lived at higher average altitudes and were exposed to higher altitude-years than those without them ( P=0.026). To test whether altitude is also associated with the more frequent detection of germ-line founder mutations among sporadic cases in The Netherlands than in the USA ( P=0.00033), we calculated population-weighted elevations of the two countries. We found that the population-weighted elevations were approximately 260 m for the US and 2 m for the central-western Netherlands ( P~0), where three Dutch founder mutations were discovered. This finding suggests that low altitudes in The Netherlands reduce penetrance and relax the natural selection on SDHD mutations. Collectively, these data suggest that higher altitudes and nonsense/splicing mutations are associated with phenotypic severity in PGL1 and support the hypothesis that SDHD mutations impair oxygen sensing.

Adrenal Gland Neoplasms↗
PubMed2003

Association of high-altitude systemic hypertension with the deletion allele-of the angiotensin-converting enzyme (ACE) gene.

People who visit high-altitude areas are exposed to a stressful environment and a good percentage of them suffer from high-altitude-induced diseases, including systemic hypertension. Identification of genetic markers for high-altitude-induced diseases would help to reduce the rate of morbidity/mortality from such diseases. The development of systemic hypertension on exposure to high altitude (3,500 m) for 30 days in otherwise normotensive natives of low-altitudes was investigated. The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) genotypes and renin-angiotensin-aldosterone system were simultaneously studied. In the hypertensives during their stay at high altitude, the ACE D allele frequency was significantly higher than in the normotensives (0.67 versus 0.32 chi(2)(1) = 10.6, P < 0.05). In the normotensives during their stay at high altitude, there was no significant increase in plasma aldosterone levels despite increased plasma renin activity. Results of the present study suggest that environmental changes and pre-existing genetic factors, namely the ACE D allele, might be two of the factors predisposing natives of low altitudes to systemic hypertension, a polygenic disease, at high altitude.

Adaptation, Physiological↗
PubMed1986

Hematologic evidence of fetal hypoxia among newborn infants at high altitude in Bolivia.

The reduced birth weight widely reported for high-altitude infants has been attributed to intrauterine hypoxia. This assertion may be tested by comparing hematologic values of high-altitude and low-altitude newborn infants, since the human fetus can respond to intrauterine hypoxia with enhanced erythropoiesis. This report presents cord blood values of term Bolivian infants classified by altitude, ethnic group, and parity: 105 from La Paz (3600 m) and 46 from Santa Cruz (400 m). Hematocrit, hemoglobin concentration, and the proportion of hemoglobin F are higher among newborn infants at high altitude. Ethnic group and parity interact with altitude in effect on hematocrit and hemoglobin concentration. Gestational age, birth weight, maternal hematologic variables, and socioeconomic indicators are not significantly associated with cord blood values. The high-altitude newborn infant displays evidence of enhanced erythropoiesis, which supports the suggestion that the high-altitude fetus experiences a greater degree of hypoxia in utero than does the low-altitude fetus.

Altitude↗