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PubMed1979

New inventory for the assessment of symptom occurrence and severity at high altitude.

A new inventory, called the Environmental Symptoms Questionnaire (ESQ), was devised to provide improved assessment of symptoms occurring during exposure to high altitude. The ESQ was field tested with 12 subjects exposed to 4300 m altitude for 4 d, and was compared with responses to the General High Altitude Questionnaire (GHAQ). Both instruments reflected significant symptom occurrence, but the ESQ was more sensitive on certain items focal to altitude conditions, and showed significant responses to items not contained in the GHAQ. Based on this test, the ESQ was judged easier to use, more sensitive, and more comprehensive for assessing medical symptoms at altitude.

Acute Disease↗
PubMed1982

[Growth of cardiac muscle cells during rat adaptation to altitude hypoxia].

The weight of the right heart ventricle in 1.5-month-old rats kept after birth in the mountains of 3400 m altitude is higher and its muscle cell cytoplasm mass is much larger compared to those in 1.5-month-old animals raised at 800 m altitude. The hypertrophy of cells is not due to their polyploidization. Only a small increase in the relative number of polyploid cells takes place under high altitude hypoxia. The weight of the right ventricle and myocyte mass in 3-month-old rats kept 1.5-3 months after the birth at 3400 m altitude also increases, although this augmentation is significantly less than in the animals grown in the mountains for 1.5 months immediately after the birth. The myocyte ploidy of adult animals adapted to hypoxia does not essentially differ from that of 1.5- and 3-month-old control rats: about 80 per cent of these cells are polyploid. Thus, the growth of cardiac myocytes under the heart hyperfunction in the case of high altitude hypoxia proceeds mainly on the ground of the stable polyploid genome, as well as normal ontogenetic growth of these cells.

Adaptation, Physiological↗
PubMed1978

Changes in EEG pattern during acclimatization to high altitude (3500 m) in man.

This study was conducted on 30 healthy soldiers to observe EEG changes during acclimatization to high altitude. Of these subjects, 10 were lowlanders (LL), 10 were acclimatized low landers (AL), and 10 10 were high-altitude natives (HAN). The EEG was recorded by the 10-20 international system of electrode placement in LL at sea level (SL) during rest and hyperventilation (HV). Then they were air-lifted to an altitude of 3500 m where periodic recordings of EEG were made for 4 weeks. For comparison, the altitude recordings were also made in AL and HAN. The quantitative analysis of EEG (occipital) was done to determine alpha index (AI) and average amplitude. The mean AI was 25.5% at SL in LL, which changed to 45.7%, 15.8%, 28.0%, 30.3%, and 33.2% on days 2, 7, 14, 21, and 28, respectively. The average amplitude was 17.3 microV at SL, which changed to 23.3 microV, 11.8 microV, 16.2 microV, 17.3 microV, and 19.8 microV on days 2, 7, 14, 21, and 28, respectively. In two subjects, spiking was seen along with the desynchronized pattern of EEG on days 7 and 14. The AI and average amplitude of AL and HAN were significantly more than those of LL. The magnitude of buildup during HV was greater at altitude. These results indicate that there is cerebral cortical depression in the initial phase of induction which changes to cortical desyncronization in the latter part of the first week of induction. During acclimatization, there is gradual buildup of EEG waves, as observed in AL and HAN.

Acclimatization↗
PubMed1978

Altitude tolerance of general aviation pilots with normal or partially impaired spirometric function.

The altitude tolerance of 10 spirometrically impaired (SI) general aviation pilots with an average forced midexpiratory flow (FEF25--75%) value of 65.1% was compared to that of 10 spirometrically normal (SN) pilots. Cardiorespiratory parameters assessed at ground level (GL) and at 8,000- and 12,500-ft altitudes were blood pressure, pulmonary ventilation, oxyhemoglobin saturation, temporal artery flow velocity, heart rate, and single-lead electrocardiogram. Although altitude exposure quantitatively displaced the SI group more than the SN group, the differences were not statistically significant at the probability level of 0.05. Unifocal premature ventricular contractions were present at GL in three of the pilots and showed no further changes at altitude. Therefore, the mean FEF25--75%, values of 65% of predicted normal for the SI group becomes a reasonable option as an objective screening norm for acceptable tolerance to general aviation altitudes in the ambient-air-breathing range.

Aerospace Medicine↗
PubMed1995

[Cardiovascular effects of a calcium channel blocker in hypoxia caused by altitude].

OBJECTIVE: High altitude pulmonary oedema can be successfully treated and prevented by calcium channel blockers. Moreover, calcium entering in the cells could explain the congestive phenomena of acute mountain sickness (AMS). These findings led us to study the action of a calcium channel blocker, isradipine, in the prevention of non-complicated AMS. METHODS: In a double blind randomized study, 20 healthy volunteers received 5 mg of isradipine (n = 6) or placebo (n = 6) for 8 days. After 5 days of treatment in normoxia, the subjects were rapidly transported to an altitude of 4350 m. The efficiency of the treatment was then estimated by the AMS symptom score, haemodynamic parameters and renal function. RESULTS: The administration of isradipine did not significantly modify AMS symptom score nor most of other parameters measured in high altitude hypoxia. Heart rate was an average of 15 b/min lower in the isradipine group, probably because of a direct action of isradipine on the sinus node. Otherwise, the effects of hypoxia were similar in both groups and were in accordance with the literature. There was no clear explanation for the increase in cardiac output and stroke volume when the subjects moved from supine to standing position. Renal blood flow, measured by Doppler or para-aminohippuric acid clearance was not modified by hypoxia. Cerebral blood flow was elevated, due to the direct vasodilator effect of hypoxia. However this increase did not seem to be the main mechanism responsible for the congestive phenomena. On the other hand, the increase in capillary permeability (demonstrated by the increased transcapillary escape rate of albumin, and albuminuria) appeared to play a major role in the pathogenesis of AMS and high altitude cerebral oedema. Isradipine had no protective effect on these phenomena and its use should be restricted to the treatment of high altitude pulmonary oedema.

Adult↗
PubMedDate not supplied

Physiologic and electrocardiographic changes occurring in broilers reared at simulated high altitude.

An experiment was conducted to determine whether differences in the electrocardiograms (EKGs) of broilers reared at simulated high altitude from the day of hatch can be used to predict which birds are developing ascites. In three replicate experiments, conducted with 100 broilers per replicate, birds were reared at a simulated altitude of 3000 meters or at ambient atmospheric pressure. Lead I, II, and III EKGs were obtained from all birds on days 0, 14, 28, and 42. No consistent significant differences were seen on day 0 in the amplitude of the R or S wave or total amplitude of the QRS complex when broilers that developed ascites while being reared at simulated high altitude were compared with unaffected birds reared at simulated high altitude and with birds reared at ambient atmospheric pressure. On days 14 and 28, the average amplitude of the S wave and the total amplitude of the QRS complex were significantly higher in the ascites group than in the two other groups. Packed cell volumes were significantly higher in birds reared at simulated high altitude at all sampling days (days 14, 28, and 42) than in those reared at ambient atmospheric pressure, and they were significantly higher in the ascites group on day 28 than in the two other groups. Birds in the ascites group weighed significantly less than the two other groups by day 14, and this trend persisted.

Altitude↗
PubMed1994

Effect of low dose sedation with diazepam on ventilatory response at moderate altitude.

UNLABELLED: Benzodiazepines are in wide use in out of hospital emergency medicine in at sea level, as well as in alpine rescue services. Ventilatory depression is a common side effect of high dose intravenous benzodiazepines. The objective of our study was to evaluate the effect of low dose benzodiazepines on ventilation at moderate altitude. DESIGN: Randomized, double blind, placebo controlled crossover trial. Blood gas analysis of 8 healthy subjects was performed before and one hour after 5 mg of oral diazepam or placebo at 171 m and at 3,000 m altitude. PaO2 and PaCO2 before and after diazepam or placebo medication at 171 m did not change significantly. At 3,000 m altitude. PaO2 decreased and PaCO2 increased significantly one hour after 5 mg of oral diazepam (PaO2 64.7 +/- 3.4 vs. 60.0 +/- 1.5 mmHg, PaCO2 28.3 +/- 2.3 vs. 33.3 +/- 1.8 mmHg, p < 0.05). Placebo did not influence PaO2 and PaCO2. CONCLUSION: Low dose diazepam inhibits ventilatory adaptation to mild hypoxia at moderate altitude. Caution in benzodiazepine use in moderate altitude is therefore necessary.

Adult↗
PubMed1994

Altitude correction for hemoglobin.

OBJECTIVE: To propose a correction for the hemoglobin (Hb) increase induced by altitude-associated hypoxia. DESIGN: Part of a national study of nutrition and health of preschool children (0-59 months), based on a stratified, probabilistic, cluster sample. SETTING: Coastal and Andean regions of Ecuador, comprising about 97% of the population, living at altitudes ranging from sea level to 3400 m. SUBJECTS: Subsample of 469 girls and boys, 6-59 months old, with normal iron (Fe) status parameters, i.e serum ferritin > or = 10 micrograms/l, transferrin saturation > or = 12%, zinc protoporphyrin < or = 2.8 micrograms/g Hb. RESULTS: Exponential regression curves are adapted through the Hb values of the children, grouped by altitude ranges, and through the data reported by Hurtado in 1945 for male adults. From these exponential curves, correction factors for Hb are derived for altitudes ranging from sea level to 3400 m. CONCLUSION: The striking parallelism between the hypoxia-induced hemoglobin increase with altitude in young children (girls and boys) and that in male adults strongly suggests that the proposed correction factors for Hb are applicable for all ages and possibly both genders, at least in the Andes.

Adult↗
PubMed1993

Study of acute mountain sickness during "rapid ascent" trekking to extreme altitude.

Acute mountain sickness (AMS) is an important cause of morbidity and mortality following acute exposure to high altitude. Several clinical variables were evaluated during the 1990 Trans-Kalindi Exploration to extreme altitude (5949 m) in 10 healthy adult lowlanders (age 31.7 +/- 6.4 yrs) who undertook a relatively rapid ascent from sea level to 5949 m with short periods of acclimatisation at 4393 m, 4898 m and 5700 m. 40% of the subjects had definite AMS. Only one subject had features of early cerebral oedema at 4393 m and had to be brought down temporarily to 3878 m. All subjects completed the trek without needing medication. Proper acclimatisation was characterised by absence of significant symptoms of AMS above 4500 m, absence of sustained tachycardia, fall in daily positive fluid balance from 1.7 +/- 0.9 (sea level) liters to 0.7 +/- 0.3 litres (at 5700 m) (p < 0.05), increase in 24 hours urinary sodium excretion from 174 +/- 78 mmol to 344 +/- 145 mmol (p < 0.01) and an increase in the ratio of urinary excretion of sodium and potassium from 3.1 (sea level) to 3.6 (5700 m). We conclude that the incidence of AMS at extreme altitude is similar to that at lower altitude. Reasonable acclimatisation is possible during the climb to extreme altitude.

Acclimatization↗
PubMed1993

[The effect of high-altitude ecological and experimental stresses on the thrombocyte-vascular wall system].

Experiments in animals (rats) and examinations of the population of high-altitude shepherds were used to study the functional system "Thrombocytes-Vessel Wall" (STVW) for evaluation of the organism ecological adaptation to "pure" high-altitude stress, with and without combination with experimental-adrenergic cardionecrosogenic stress (ACNS, in rats). The adaptive increase of antiaggregation prostacyclin activity of the aorta in rats and PGI2 reaction of vessels in human population of high-altitude in mountains (2000, 3000-3500 m) were found to be a common biologist regularity. The adaptive increase of coronary reserve of the heart and vasodilatator-antiaggregation status in high-altitude shepherds correlated with an increase of antiaggregation activity of the aorta and decrease of spontaneous aggregation of the thrombocytes in rats under conditions of more prolonged adaptation to high-altitude ecological stress.

Adaptation, Physiological↗
PubMed1993

[Prevention and therapy of altitude sickness].

Climbing in the Alps and trekking in the Andes or in the Himalayas became more and more popular in the last years. This is the reason why more and more tourists develop symptoms of acute mountain sickness (AMS) at an altitude higher than 2500 m a.s.l. To avoid an unpleasant stay at altitude, an accurate acclimatization is necessary. This can be achieved by a slow ascent at a climbing rate of 300 to 600 m in one day. If that is not possible, climbers should spend at least nine or more nights at an altitude higher than 2500 m a.s.l. in the last 30 days before ascent. This would improve performance at high altitude and significantly decrease symptoms of AMS. If acclimatization for one or another reason may not be possible or if somebody is still susceptible to AMS, pharmacological prophylaxis and treatment can be used. Drug of first choice for AMS prophylaxis is acetazolamide, a carboanhydrase inhibitor who increases ventilation. Acetazolamide has been used in a dosage of 250 to 500 mg 12 to 24 h. before ascent. If climbers have a history of high-altitude pulmonary edema (HAPE), nifedipine, a potent vasodilator which decreases pulmonary artery pressure, is the drug of the first choice and should be taken in a dosage of 3 x 20 mg, beginning one day before climbing and continuing during climbing. Prophylactic administration of nifedipine has no effect on symptoms of AMS in subjects who are not susceptible to HAPE.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1995

The association between strenuous physical activity and obesity in a high and low altitude populations in southern Saudi Arabia.

OBJECTIVES: To assess the relationship between obesity and strenuous physical activity in Saudi nationals living at high and low altitude. DESIGN: Cross-sectional randomized study. SUBJECTS: A total of 437 healthy adult Saudi nationals born and living permanently at high altitude (3150 m) and 468 healthy adult Saudi nationals born and living permanently at relatively low altitude 500 m). MEASUREMENTS: Body Mass Index (Weight (kg)/height (m2)) strenuous activity scores using Lipid Research Clinic Questionnaire. Resting radial pulse rate (beats/min). RESULTS: Strenuous physical activity was significantly and inversely associated with obesity in men at both high (chi 2 = 7.13, P < 0.05) and low (chi 2 = 6.14, P < 0.05) altitude but there was no clear trend for women at either altitude. The lack of association between strenuous physical activity and obesity in women was attributed to the low and homogeneous levels of strenuous physical activity. CONCLUSION: Strenuous physical activity should be encouraged as strategy directed towards weight reduction in obese as well as prevention of obesity in Saudi high and lowlanders.

Adolescent↗
PubMed1977

Altitude and hypertension.

In order to study the prevalence of hypertension and some of the factors relevant to its natural history, cross-sectional surveys were performed during the period 1967 to 1973 in five small Peruvian communities, two located at sea level and three above 13,000 feet of altitude. In total, 4,359 persons were studied at sea level (1,970 males and 2,389 females) and 3,055 at high altitude 2,189 males and 866 females). At high altitude, the age-adjusted prevalence of hypertension (particularly systolic) was definitely low; diastolic hypertension was more frequent in men than in women, and it was commoner than systolic hypertension. The reverse was observed in communities at sea level. Long-term blood pressure changes observed in natives accustomed to high altitudes but living at sea level, as well as in white persons usually living at sea level but residing at high altitude, appear to indicate that environmental forces are more important than genetic predispositions in determing the rarity of hypertension in the highlands. Among the environmental forces, chronic hypoxia seems to play an important causal role.

Adolescent↗
PubMed1996

The effects of moderate altitude on circulating thyroid hormones and thyrotropin in training athletes.

OBJECTIVE: To study the effect of moderate altitude on thyroid hormones among training athletes. EXPERIMENTAL DESIGN: Serum total and free triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH) concentrations were measured among eight training athletes at sea level and subsequently during training for 12 days at the altitude of 1100-2700 m. SETTING: Deaconess Institute of Oulu, and Division of Sports Medicine, Department of Physiology, University of Oulu, Finland. PARTICIPANTS: National top class skiers who normally live at sea level. RESULTS: Serum concentrations of TSH, total and free T4, and reverse T3 did not change significantly. A significant decrease in serum total T3 levels from 1.9 nmol*1-1 on days 1-3 to 1.6-1.7 nmol*l-1 on days and 5-6 (p < 0.05) was observed. Serum albumin decreased (p < 0.05) on days 1-8 at altitude and correlated to serum total T3 (R = 0.36, p = 0.013). Serum free T3 increased steadily at moderate altitude and reached a significantly higher level (p < 0.05) at the end of the training period than before. CONCLUSIONS: The serum free T3 increases when unacclimatized sea level skiers move to train at moderate altitude.

Adult↗
PubMed1996

Left ventricular gas emboli in six cases of altitude-induced decompression sickness.

BACKGROUND: Ultrasonic techniques have demonstrated venous gas emboli (VGE) during exposure to high altitude. VGE per se have not been considered clinically hazardous. Arterial gas emboli (AGE), however, are viewed with great concern. The crossing-over of venous gas to the arterial circulation has not previously been seen in human subjects at altitude. This transfer may occur via either intracardiac defects, pulmonary shunts, or the pulmonary microcirculation. METHODS: A non-invasive ultrasonic echo imaging Doppler system was used to monitor volunteer human subjects for gas emboli simultaneously in the right and left sides of the heart at simulated altitude in a chamber. Subjects found to have gas cross-over were evaluated for septal defects with either transthoracic or transesophageal echocardiography. RESULTS: Previously unreported left ventricular gas emboli were observed with echo imaging in six subjects at altitude. In all six cases, at the time of AGE onset, the VGE scores were high from all monitored sites. Three subjects had no septal defect, another had a small sinus venosus defect, a third had a patent foramen ovale, and one was not available for evaluation. Five of the cases became symptomatic at the time of AGE onset. CONCLUSIONS: Operational altitude exposures known to elicit high VGE counts in the majority of people should be avoided because of an increased risk of right-to-left gas cross-over and resulting potential for severe cerebral symptomatology.

Aerospace Medicine↗
PubMed1996

[Effect of altitude on blood oxygenation during sleep in patients with bronchial asthma].

The aim of our study was to investigate the severity of overnight arterial blood desaturations in patients with asthma at the altitude of 3200 meters above sea level. 12 asthmatics and 12 healthy controls were investigated. Three overnight pulsoximetries were performed in all subjects, one at the lowland and on the 1st and 5th night at the altitude. Mean SaO2 at the lowland was significantly lower in asthmatics than in the controls (p < 0.01). After the ascent to high altitude severe fall in mean SaO2 was noted in both groups (from 94.3% to 85.8% in asthmatics and from 97.1% to 88.7% in controls) (p < 0.001 for both groups). After few days of acclimatization mean SaO2 rose to 88.8% in asthmatics and to 91.3% in controls, but was still significantly lower than at the lowland (p < 0.001 for both groups). At the altitude differences in mean SaO2 between two groups were not statistically significant. We conclude that severity of overnight desaturations at high altitude do not vary between asthmatics with impaired respiratory function and healthy subjects.

Adolescent↗
PubMed1997

Involvement of nitric oxide and N-methyl-D-aspartate in acute hypoxic altitude convulsion in mice.

BACKGROUND: Altitude convulsion is a rather specific form of experimental convulsion which is induced by acute exposure to a hypobaric hypoxic condition. Several neurotransmitters have been shown to be involved in the mechanisms of altitude convulsions. However, their roles and interaction were not clear. HYPOTHESIS: The novel neurotransmitter nitric oxide (NO) may be involved in the mechanisms of altitude convulsion through its neuronal signalling roles in relation to the NMDA receptor. METHODS: There were 177 mice intraperitoneally administrated (i.p.) with several drugs. The altitude convulsion threshold (ACT) was used as an index to evaluate the acute hypoxic tolerance. RESULTS: NO synthesis precursor, L-arginine (20, 40, 200, 800 mg/kg), resulted in a dose-dependent decrease in the ACT in mice, while the NO synthase (NOS) inhibitor, NG-nitro-L-arginine-methyl ester (L-NAME, 1.25, 2.50, 5.00 mg/kg, i.p.) increased the ACT. Pretreatment with L-NAME (5.0 mg/kg) prior to L-arginine (200 mg/kg) administration prevented the effect of decreasing ACT caused by L-arginine. Similarly, N-methyl-D-aspartate (NMDA, 2.5, 10.0, 20.0 mg/kg, i.p.) yielded a decrease in the ACT in mice and this decrease in hypoxic tolerance caused by NMDA can be prevented by pretreatment with either NMDA receptor antagonist 2-amino-5-phosphovalerate (AP-5, 20.0 mg/kg, i.p.) or NOS inhibitor L-NAME (5.0 mg/kg, i.p.). CONCLUSIONS: These findings suggest an important signalling role for nitric oxide and NMDA in the development of altitude convulsion and further support the hypothesized relationship between NMDA-receptor mediated neurotoxicity and nitric oxide.

Acute Disease↗
PubMed1997

Visual system effects of exercise on Mauna Kea at 2,200 and 4,200 meters altitude.

Field exercise studies were performed at two altitudes (2,200 and 4,200 m) in 2 successive years using different sets of young male volunteers. Visual function indices were measured both at sea level and during a strenuous exercise regime at altitude. Volunteers were grouped in the first study by initial rest period (2 days vs. no rest) and in the second by diet (supplemental carbohydrates vs. Meals Ready to Eat rations only). Overall results showed no effect according to grouping, a decrease in average visual acuity at the higher altitude overall, and a decrease in electroretinographic (ERG) photopic flicker responses at moderate altitude. It is concluded that heavy exercise at these altitudes may not have operationally significant effects on ground troops in night vision or target recognition, although the change in ERG parameters does indicate a shift in retinal cone physiology that may have subtler effects.

Adaptation, Physiological↗