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At least 685 records · Page 38Linked to original sources
PubMed1988

Mood states at 1600 and 4300 meters terrestrial altitude.

Personal anecdotes suggest that ascent to high altitude can cause mood changes such as depression, apathy, and drowsiness. Observed behaviors at high altitude indicate that people can become more euphoric, irritable, or argumentative. Since there are few systematic and quantitative studies assessing the effects of altitude on mood, this study compared moods measured at two different altitudes and times of day (morning-evening) using a standardized scale. Self-rated moods were determined twice daily in 19 males and 16 females with the Clyde Mood Scale. Baseline values were determined at 200 m; moods were then assessed at 4300 m with one group and at 1600 m with a second group. Friendliness, clear thinking, dizziness, sleepiness, and unhappiness were affected at 4300 m but only sleepiness changed at 1600 m. At 4300 m, the altered moods differed from baseline on the day of arrival (1-4 hours), differed even more after one day (18-28 hours), and returned to baseline by day 2 (42-52 hours). Morning and evening values were similar at each altitude. Therefore, changes in mood states at altitude have a distinct and measurable time course.

Adult↗
PubMed1979

Cardiorespiratory assessment of decongestant-antihistamine effects on altitude, +Gz, and fatigue tolerances.

Decongestants and antihistamines are known to produce effects capable of adversely modifying physiological function and psychomotor task performance. Because of relevance to safe pilot performance, the effects of single doses of two decongestant-antihistamine preparations (Compound A and Compound B), or a placebo on cardiorespiratory responses to two equally spaced +2 Gz tests during separate 2-h exposures at 388 m (1,274 ft MSL) ground level (GL) and 3,810 m (12,500 ft) chamber altitude were assessed. Post-altitude fatigue was assessed by cardiorespiratory responses to submaximal bicycle ergometry. Compound A and Compound B appeared to exert no significant detrimental effects on short-duration post-altitude ergometric fatigue-ability. With two exceptions, all combinations of medication, altitude, and +Gz were well tolerated. Two subjects were clearly incapacitated during the first +2 Gz test under Compound A at 3,810 m (12,500 ft) altitude. It is felt that the +Gz-intolerance resulted mainly from an adverse interactive effect of Compound A and altitude on vasomotor and/or chronotropic mechanisms.

Adult↗
PubMed1979

Effect of physical training at moderate altitude (1850 m) on hypoxic tolerance.

Effect of systematic physical training at moderate altitude (1850 m) on hypoxic tolerance was estimated on a group of young soldiers, by determining the Time of Useful Consciousness (TUC) at a simulated altitude of 7620 m in a hypobaric chamber together with the Critical Flicker Frequency (CFF) test. The subjects, after initial testing at Delhi (near sea level) were taken to an altitude of 1850 m and divided into two groups. One group was given systematic endurance physical training for 8 weeks, while the other group served as control. The subjects were then taken to an altitude of 3500 m and kept at that altitude for 4 weeks, after which they were brought back to Delhi and TUC was estimated again within 2 d. The results indicate that endurance physical training at moderate altitude improved hypoxic tolerance and the central nervous system activity under hypoxia.

Acclimatization↗
PubMedDate not supplied

Alveolar stability of altitude raised rats.

On the lining of alveolar membrane of the lung presence of surfactant, a surface tension lowering agent which is a phospholipid in nature, is well established. A good correlation exists between pulmonary lecithin, the principle constituent of surfactant system and alveolar stability. The production of surface active material in the type II cells is oxygen dependent and is affected by hypoxia. The chemical and physical nature of the surfactant in the lungs of the rats raised at high altitude has been studied in comparison with that of sea level control. Eighteen male adult rats raised at high altitude (3520 m) were used. Phospholipids (Phosphatidyl Choline, Phosphatidyl ethanolamine, Lysophosphatidyl choline, Lysophosphatidyl ethanolamine and Sphingomyelin) were estimated by thin layer chromatography, stability index by Pattle's bubble technique and dynamic surface tension have also been studied to assess the surfactant activity of the lung. The results indicate that there was a decrease in lung surfactant as measured by chemical analysis. However, stability ratio measurements showed that there was very little change in the stability ratio (Sr) as the value of both groups lay in the normal range namely 0.6 to 0.9 hence the lungs of high altitude raised rats had normal alveolar stability. Surface tension values of alveolar lavage in altitude raised animals were also similar to those of normal rats. It is concluded that the rats raised at altitude show a lowering of surfactant as estimated chemically but the stability ratio is not significantly altered to indicate alveolar instability. In the altitude rats lesser quantum of surfactant is adequate to maintain alveolar stability.

Altitude↗
PubMed1982

Pituitary response to luteinizing hormone-releasing hormone analog at sea level and high altitudes.

Two groups of subjects living at different altitudes were stimulated with synthetic luteinizing hormone-releasing hormone (LH-RH) or with an LH-RH analog. One hundred micrograms LH-RH was given subcutaneously to 19 men and 19 women, all normal, of reproductive age, and living at sea level, and to 19 men and 20 women living at a high altitude (2940 m). In neither sex, however, were the differences in peak responses for both gonadotropins significantly different between the sea level and high-altitude groups. Plasma levels of LH and follicle-stimulating hormone (FSH) were also measured after administration of [D-Leu6, des Gly-NH2(10)]-LH-RH ethylamide (25 micrograms subcutaneously) in 32 men and 37 women living at sea level and at high altitude. The analog induced a powerful and protracted stimulation of the release of LH and FSH irrespective of altitude and sex. The responses of men and women to the LH-RH analog, both for LH as well as for FSH, were significantly greater at sea level than at high altitudes.

Adolescent↗
PubMed1980

[Oxygen affinity of haemoglobin 3 hours after passive increase in altitude from 400 to 1800 metres (author's transl)].

An investigation was undertaken in 9 male subjects of the effect of short exposure to moderate altitude on the oxygen affinity of haemoglobin and other parameters. Initial measurements were performed at 425 m and repeated 3 hours after ascent by cable car to an altitude of 1800 m (Untersberg, Salzburg), no muscular activity being allowed (first period). The same protocol was repeated 3 days subsequently except that after ascent the individuals were exercised on an ergometer bicycle (second part). Altitude exposure without exercise leads to a small, but significant increase in the pH corrected P50 value (= half-saturation tension), whereas the non-corrected P50 value showed no significant change. In the second part of the study the corrected and non-corrected P50 values both increased significantly. The whole body pH and the intraerythrocytic pH rose, whereas PCO2 decreased significantly. The intraerythrocytic 2,3-DPG concentration showed a significant increase (1.2 mumol/gHb) after 3 hours of altitude exposure with and without muscular exercise. The prealtitude DPG concentration and the P50 values in the second period were higher than the first control values. The red blood count and sodium and chloride concentration showed no changes. Potassium rose in both experimental periods, whereas inorganic plasma phosphates decreased. These findings show that 3 hours after cable-car ascent to a medium altitude a DPG increase occurs which is able to counteract the Bohr effect. This means that the expected impairment of tissue oxygenation, caused by the alkalosis-induced shift of the dissociation curve to the left, is prevented. These findings also indicate that a repeated "passive" ascent to moderate altitude can lead to an increased oxygen delivery to the tissue.

Adult↗
PubMed1995

[Lung problems in acute to subacute exposure to medium altitudes].

The hypobaric hypoxia of moderate altitude elicits various mechanisms of acute to subacute physiologic adaptations of the healthy lung: First of all it causes a hyperventilation, which increases the diminished arterial pO2. Because of hypoxemia-induced vasoconstriction, pulmonary arterial hypertension develops. The adrenergic stimulation of the cardiac output also increases the pulmonary perfusion. Most likely because of the diminished density of ambient air there is a measurable increase of exspiratory bronchial flow or, respectively, a diminution of the peripheral airway resistance. In higher altitudes, limitation of oxygen-diffusion under physical exertion is observed. The consequences of acute hypobaric hypoxia for diseased lungs depend on preexisting ventilation/perfusion mismatch or diffusion impairment. Arterial hypoxemia and hence also pulmonary arterial hypertension are increased. In the presence of normal chemoreceptor sensitivity (type pink puffer), a hyperventilation, which is often perceived as dyspnea by the patient, is induced. Mostly patients with chronic obstructive pulmonary disease adapt, however, surprisingly well to moderate altitude. Bronchial asthma improves frequently because allergen concentrations are low and air density is diminished. On the other hand, physical exertion in dry and cold ambient air may also elicit acute asthmatic exacerbations. The assessment of moderate altitude tolerance by patients with chronic lung diseases and prophylactic precautions before the ascent are discussed. The only altitude-specific disease of the healthy lung is the so-called high-altitude pulmonary edema. The major pathogenetic factor for its development is an inadequate or overshooting response to hypobaric hypoxia (nonuniform pulmonary arterial vasoconstriction, diminished hypoxic ventilatory drive, retention of fluid, centralization of blood volume and capillary leak). Prophylactic and therapeutic implications are discussed.

Altitude↗
PubMed1994

[High altitude lung edema in the East Alps].

We present a case of high-altitude pulmonary edema in a trained skier who undertook a three-day tour in the eastern Alps. This clinical condition can occur in hitherto healthy, predisposed persons at a critical altitude of 2500-3000 m and has to be differentiated above all from pneumonia. Extreme physical exertion, especially at low temperatures, the intake of alcohol or hypnotics and, presumably, preceding infection of the respiratory tract favor the occurrence of high-altitude pulmonary edema. The history of having spent the night at or above the critical altitude and the spontaneous restitutio ad integrum with rapid clinical recovery and dissolution of the radiographic pulmonary infiltrates within a few days after evacuation to lower altitudes are decisive features in establishing the diagnosis. Without therapy or evacuation the mortality rate is 50%. In spite of the low incidence in the eastern Alps, as opposed to the western Alpine countries, the potentially fatal course of high-altitude pulmonary edema should make it mandatory to equip huts and refuges above 3000 m even in the eastern Alps with the first-aid medicament nifedipine and therapeutic oxygen.

Adult↗
PubMed1994

[Physical activity at intermediate altitude by healthy probands and patients with coronary sclerosis].

For the majority of the population, exposure to altitudes higher than 2000 m above sea level constitutes a situation of pronounced stimulation of the organism. The question comes in of the health relevance of physical activity at intermediate altitudes for the healthy subjects, but above all for people with heart problems. At first, there is an acute adaption on the cardiovascular and the respiration system as well as the system of oxygen carriage, until the chronic adaption processes of the same systems are completed. Doubtlessly, these adaption processes at intermediate altitudes and in particular training in such regions considerably improve the endurance capacity under conditions of the kind mentioned. However there is little evidence, for an absolute improvement of the maximal aerobic capacity. As a rule, the effects of adaption to higher altitudes can also be expected in patients with coronary sclerosis. But a lowered level of capacity must be taken into account in these cases. Accordingly, the medication as well as the intensity of stress should be adapted to altered conditions of this kind. Training intensity must be reduced according to altitude, and any treatment for angina, must be intensified. It may be necessary to re-determine the appropriate training intensity as well as the dosage in pharmacotherapy by ergometric methods to match the new requirements. However, when a comparison is tried to kinetotherapy under normal conditions, an immediate therapeutical effect of exposition to higher altitudes appears to be at least doubtful.

Acclimatization↗
PubMed1994

[Etiology, clinical aspects and therapy of altitude sickness].

Experimental and clinical tests carried out over the last few years have brought many new and important insights into the pathophysiology of the so-called high-altitude sickness. Overall, new, scientifically proven methods for the acute therapy of various forms of high-altitude sickness have been made, which can be used for medical practice. Azetazolamide: The clinical effectiveness and the improvement of the exchange of body gases seem to be, to a large extent, scientifically proven. Dexamethasone: Several scientifically controlled studies have proven the effectiveness of dexamethasone regarding the relief of symptoms mainly concerning cerebral high-altitude oedema. Controlled studies confirm a significant reduction of symptoms, compared to placebo methods, the effects vanishing after a 12-hour therapy. Nifedipine: The prescription of nifedipine for radiologically proven high-altitude oedema often leads to a clinical improvement, to an improved oxygenation, to a reduction of the alveolar-arterial oxygen gradient, as well as the pulmonary-arterial pressure and, thus, to a great extent, leads to progrediental oedema dissolution. However, in the practice of high-altitude hiking, this therapy has its natural limits and therefore must not lead to the neglection of prophylactics, which means, consistent acclimatisation regarding the classical rules of high-altitude hiking.

Acclimatization↗
PubMed1976

Interaction between marihuana and altitude on a complex behavioral task in baboons.

Marihuana, or its principal active ingredient, delta-9-tetra-hydrocannabinal (delta9-THC), impairs performance on complex behavioral tasks in animals and man. Although there exists some evidence that altitude-induced hypoxia potentiates the physiological effects of marihuana, the interaction between altitude and marihuana on behavioral tasks has not been established. In the absence of evidence that use of marihuana is less frequent among members of the aviation community than among the general population, it was necessary to evaluate the effects on performance of any interaction between hypoxia and marihuana. Two baboons were trained to perform on a delayed matching-to-sample task at ground level and altitudes of 2438 and 3658 m (8000 and 12000 ft). The animals were orally administered doses of delta9-THC, ranging from 0.25 to 2.0 mg/kg, 2 h prior to experimental sessions at each altitude. No effects on accuracy of matching performance were observed for any of the drug doses or altitudes used. Amount of work output, as measured by number of trials completed and speed of responding, was not affected by delta9-THC at ground level but was markedly reduced by the higher drug doses at the 2438- and 3658-m altitudes. This interaction suggests that the behavioral impairment produced by marihuana can be potentiated by hypoxia.

Aerospace Medicine↗
PubMedDate not supplied

Oxygen saturation in children living at moderate altitude.

BACKGROUND: Physicians caring for newborns and infants residing at or traveling to moderate altitude have little information available about the normal range for arterial oxygen saturation (SaO2) measured by pulse oximetry. To aid clinicians in making rational decisions about the oxygen status of children at moderate altitude, we measured SaO2 in newborns and infants who came to two family practice offices located at an altitude of 2800 meters (9000 feet) to obtain normal values for both well-child and illness visits. METHODS: SaO2 measured by pulse oximetry was recorded for children younger than 2 years seen consecutively in a family practice clinic for care for any reason. The children all resided at an altitude of 2800 m (9000 ft). RESULTS: The mean SaO2 for healthy awake infants was 91.7 percent, significantly lower than the reported normal ranges for either sea level or Denver. Saturation levels in infants with minor acute illnesses did not differ from saturation levels in healthy infants, while infants with lower respiratory tract infections had significantly lower SaO2 measurements. CONCLUSIONS: SaO2 levels are significantly lower in newborns and infants living at moderate altitude. Measurement of SaO2 at moderate altitude can be helpful in the care of both healthy and ill newborns or infants.

Altitude↗
PubMed1993

[High altitude sojourn in pregnancy and childhood].

Knowledge about the safety of travel to high or moderate altitude during pregnancy or with small children is limited. Previous recommendations restricting travel during pregnancy to an altitude of 2133 m a.s.l. may be too cautious; however, not enough research has been done to allow any recommendation based on scientific evidence. Infants and children generally do well at moderate altitude (< 3000 m a.s.l.), if ascent is gradual and if the child is watched closely for any developing signs or symptoms of acute mountain sickness or high-altitude pulmonary edema. Infants of residents of low altitude may develop right-heart failure due to excessive pulmonary artery hypertension when exposed to altitudes more than 3500 m a.s.l. over several months (subacute mountain sickness).

Acclimatization↗
PubMed1993

Effects of simulated high altitude exposure on long-latency event-related brain potentials and performance.

The N100, P200, N200 and P300 components of the auditory event-related potential were recorded from 10 male subjects at 0900, 1600, and 1830 hours at sea level and again following a rapid ascent to simulated 4300 m altitude. Amplitude and latency of components, ear oximetry, and concurrent performance measures (reaction time and counting errors) were assessed. Amplitude of P300 decreased, while P300 latency and reaction time increased, following ascent to altitude. However, the time course of altitude effects differed for amplitude versus latency. Components N100, P200, N200, and counting errors were unaffected by altitude. The results indicate that central measures of cognitive capacities are differentially sensitive to high altitude. The time course of altitude effects on P300 amplitude versus P300 latency suggests that the two measures reflect different aspects of a response to hypobaric hypoxia exposure.

Adult↗
PubMed1993

Hematocrit levels in children at sea level and at high altitude: effect of adrenal androgens.

Hematocrit values are normally higher in natives living at high altitude than in natives living at sea level. Here, we have determined the hematocrit levels in relation to adrenal androgens in children living at altitudes of 150 m and 3400 m above sea level. The data demonstrate no association between serum adrenal androgens levels and hematocrit values. For all ages studied, hematocrit levels were higher in children at high altitude than in children at low altitude. Higher hematocrit values (> or = 54%) were observed in 15% of native boys at 3400 m. These data suggest that the higher hematocrit levels observed normally in children at high altitude are mainly related to altitude hypoxia and not to adrenal androgens.

Age Factors↗
PubMed1996

Changes in plasma electrolytes during acclimatization at high altitude.

The effects on plasma electrolytes and related hormones were determined in non-acclimatized low lander males, exposed for 96 hours to an altitude of 4424 meters. Twenty healthy soldiers aged 18-34 years travelled by road from an altitude of 2303 meters to 4424 meters over a period of 10 hours. Plasma sodium levels (142.09 +/- 1.14 mmol/1) and aldosterone (16.61 +/- 5.70 ng/ml) decreased to 139.69 mmol/1 and 11.6 +/- 4.60 ug/ml respectively after 96 hours of acute exposure to high altitude (p < 0.05). The plasma potassium and chloride levels did not show significant change, while, plasma HCO3 decreased gradually from 21.06 +/- 1.38 mmol/1 to 18.55 +/- 0.82 mmol/1 after 96 hours exposure to this altitude (p < 0.01). The plasma ionized calcium and plasma phosphate concentration decreased from 1.32 +/- 0.11 mmol/1 and 1.58 +/- 1.3 mmol/1 to 1.20 +/- 0.05 mmol/1 and 1.47 +/- 0.99 mmol/1 respectively (p < 0.05). Plasma parathyroid hormone (PTH) level increased from 4.54 +/- 2.1 ng/ml to 11.19 +/- 4.31 ng/ml after 48 hours with subsequent decline to 2.52 +/- 1.7 ng/ml after 96 hours exposure to high altitude. It may be concluded that the process of acclimatization to sudden exposure to high altitude is characterised by fall in plasma aldosterone and PTH with subsequent decrease of related electrolytes.

Acclimatization↗
PubMed1998

An abrupt zero-preoxygenation altitude threshold for decompression sickness symptoms.

INTRODUCTION: The altitude threshold for decompression sickness (DCS) symptoms has been variously described as being 18,000 ft (5,487 m) to above 25,000 ft (7,620 m). Safety and efficiency of aerospace operations require more precise determination of the DCS threshold. METHODS: Subjects were 124 males who were exposed to simulated altitudes (11 at 11,500 ft; 10 at 15,000 ft; 8 at 16,500 ft; 10 at 18,100 ft; 10 at 19,800 ft; 20 at 21,200 ft; 20 at 22,500 ft; 10 at 23,800 ft, and 25 at 25,000 ft) for 4 to 8 h. All breathed 100% oxygen beginning with ascent. Subjects were monitored for precordial venous gas emboli (VGE) and DCS symptoms. Probit curves representing altitude vs. incidence of DCS symptoms and VGE allowed estimation of respective risk. RESULTS: VGE were first observed at 15,000 ft with increasing incidence at higher altitudes; over 50% at 21,200 ft and 70% or higher at 22,500 ft and above. The lowest altitude occurrence of DCS was a 5% incidence at 21,200 ft. At 22,500 ft, the DCS incidence abruptly climbed to 55%. CONCLUSION: A 5% threshold for DCS symptoms was concluded to be 20,500 ft under the conditions of this study. The abrupt increase in DCS symptoms, with zero-preoxygenation exposure above 21,200 ft implies a need for reconsideration of current USAF and FAA altitude exposure guidance.

Aerospace Medicine↗
PubMed1998

High-altitude medicine.

As more people enjoy the outdoors, high-altitude illness is increasingly becoming a problem that family physicians across the country must treat. High-altitude illness, which usually occurs at altitudes of over 1,500 m (4,921 ft), is caused primarily by hypoxia but is compounded by cold and exposure. It presents as one of three forms: acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). But high-altitude illness can have many other manifestations. Cardinal symptoms include dyspnea on exertion and at rest, cough, nausea, difficulty sleeping, headache and mental status changes. Treatment requires descent, and gradual acclimatization provides the most effective prevention. Acetazolimide is an effective preventive aid and can be used in certain conditions as treatment.

Acute Disease↗