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[Who gets altitude sickness?].
The author discusses factors promoting the occurrence of acute mountain sickness and high altitude pulmonary edema. The level of altitude as well as the speed of ascent are important determinants and can be influenced by behaviour. A low hypoxic ventilatory drive presents a constitutional factor predisposing to acute mountain sickness and high altitude pulmonary edema. Individuals susceptible to high altitude pulmonary edema also show increased hypoxia vasoconstriction of pulmonary arterioles. The importance of an exaggerated hypoxic pulmonary vascular response for the pathogenesis of high altitude pulmonary edema is demonstrated by the observation that this illness can be treated or prevented by lowering pulmonary artery pressure with nifedipine. In most cases, however, acute mountain sickness and high altitude pulmonary edema can be prevented without the help of drugs, by adjusting the speed of ascent to the degree of susceptibility to these illnesses.
Altitude sickness.
Ten climbers were studied trekking from 1,950 to 4,650 m (6,500 ft to 15,500 ft) in the Nanda Devi Sanctuary of the Garwhal Himalaya. All developed altitude sickness, one seriously. Pulse, blood pressure, and peak flow rate were monitored daily in an attempt to predict the onset of altitude sickness. Prediction was uncertain though the one climber who became seriously cyanosed at 4,200 m (14,000 ft) had a consistently higher blood pressure than his colleagues.
[Advantages of delayed-action Pervincamine Forte in the prevention of altitude sickness].
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[Pathophysiology and therapy of altitude sickness].
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[Altitude sickness].
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[Prevention of altitude sickness].
In experimental and clinical studies the effect of Acetazolamide (Diamox) on acute mountain sickness was investigated. It could be established that Acetazolamide does influence the symptoms, the man effect seems to be a reduction of the respiratory alkalosis, which is found in control persons in high altitudes. Observations made with a group of 25 tourists mountaineering in the Cordilleras (South America) over 24 days in altitudes between 3200 and 6000 m are described. In accordance with other published data the favorable influence of Acetazolamide on acute mountain sickness could be confirmed. Persons taking Acetazolamide were more efficient and better prepared to cope with the extreme situations in high altitude. They also showed to be more resistent to other diseases, which are following the stress in high altitude and are caused by the different climate and food.
Altitude decompression sickness: hyperbaric therapy results in 145 cases.
Most cases of decompression sickness that occur at altitude resolve upon descent to lower altitudes. Before the use of hyperbaric therapy, cases that did not resolve accounted for some of the most difficult medical management problems in military aerospace medicine. On 27 March, 1941, the U.S. Navy Diving School successfully used hyperbaric therapy for a case of altitude-induced decompression sickness that did not resolve on return to ground level. Since then, over 145 such cases have been treated by hyperbaric therapy. At first, treatments involved using compressed air, with varying success. Current medical management of altitude-induced decompression sickness requires immediate compression to 2.8 ATA, equivalent to 60 ft of sea water (FSW) pressure, and a series of intermittent oxygen and air breathing periods during the subsequent slow decompression to surface. This report confirms the treatment recommendations set forth by Behnke and Downey, and crystallized by Goodman in 1964. Conclusions are based on treatment experience in the management of 120 cases in U.S. Air Force hyperbaric chambers, and a survey of hyperbaric facilities which have treated 25 other cases.
[Prevention of altitude decompression sickness during short flights in a depressurized cabin at high altitudes].
Forty altitude chamber experiments were carried out in which 18 test subjects participated. The purpose of the experiments was to prevent decompression sickness in a pilot using an altitude compensatory suit and oxygen mask. It was demonstrated that oxygen breathing on the ground and at an altitude of 8 km for 20 and 50-60 min eliminated severe symptoms and lowered the frequency of occurrence of mild symptoms of decompression sickness during the subsequent 10-20 and 60-120 min exposures to altitudes of 40,000 and 11,000 m respectively. An increase in the absolute pressure to 240-290 mm Hg in the altitude garment prevented decompression sickness of altitudes of 11,000-15,000 m and eliminated it if it occurred at lower barometric pressure.
Time to detection of circulating microbubbles as a risk factor for symptoms of altitude decompression sickness.
This study investigated the association between time at onset of circulating microbubbles (CMB) and symptoms of altitude decompression sickness (DCS), using Cox proportional hazard regression models. The study population consisted of 125 individuals who participated in direct ascent, simulated extravehicular activities profiles. Using individual CMB status as a time-dependent variable, we found that the hazard for symptoms increased significantly (at the end of 180 min at altitude) in the presence of CMB (Hazard Ratio = 29.59; 95% confidence interval [95% CI] = 7.66-114.27), compared to no CMB. Further examination was conducted on the subgroup of individuals who developed microbubbles during the test (n = 49), by using Cox regression. Individuals with late onset of CMB (> 60 min at altitude) showed a significantly reduced risk of symptoms (hazard ratio = 0.92; 95% CI = 0.89-0.95), compared to those with early onset (< or = 60 min), while controlling for other risk factors. We conclude that time to detection of circulating microbubbles is an independent determinant of symptoms of DCS.
[Hypobaric nitrogen-oxygen atmosphere as a method of preventing altitude decompression sickness].
It has been shown experimentally that the development of altitude decompression disease at 250 and 180 mm Hg can be prevented by preliminary desaturation in the nitrogen-oxygen hypobaric atmosphere (60% N2 and 40% O2 at 550 mm Hg). This has been demonstrated in 38 experiments on 21 test subjects. The use of this atmosphere in space cabin prevents the development of decompression disease upon a decrease of the cabin pressure to 250 mm Hg and upon extravehicular activity in a space suit with 180--200 mm Hg.
The causes of death among trekkers in Nepal.
A review of trekking deaths from 1984 to mid-1987 showed a death rate of 15/100,000 trekkers. Altitude sickness deaths accounted for 3/23 (13%) of these deaths. Recently, we followed up on our original study by compiling the number and causes of trekking deaths in Nepal from mid-1987 through 1991. The overall number of deaths was 40, out of 275,950 trekkers (death rate 14/100,000). Illness accounted for 14 deaths, trauma was the cause of 12 deaths, altitude sickness was the cause of 10 deaths, 3 people were found dead after being reported missing, and one person is still missing and presumed dead. Eight out of 10 altitude sickness deaths occurred in organized trekking groups, even though only 40% of trekkers trek in organized groups. Four people were reported to have died from heart attacks, and 3 people died from apparent diabetic ketoacidosis above 4000 meters in altitude. Trekking in Nepal is a relatively safe holiday that currently attracts more than 60,000 people each year. Monitoring the causes of death among trekkers can help generate advice that could make trekking even safer.
[Prevention of altitude decompression sickness in flights in a depressurized cabin].
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[Probability of altitude decompression sickness during a suited exit from a space ship having a near-Earth atmosphere].
A large number (550) pressure chamber experiments in which 200 suited subjects simulated an egress from the spacecraft (decompression from 760 to 20--10 mm Hg) showed a relationship between decompression sickness frequency and severity, space suit absolute pressure (160--310 mm Hg), time of the exposure (1--10 hours) and desaturation (15--60 min), and exercise load (150--400 Cal/hr). Without desaturation there were no decompression sickness symptoms at a suit pressure of 270--310 mm Hg. An egress into space in a suit at a pressure of 160--230 mm Hg after 15--60 min desaturation induced bends of different severity. Less frequent cases of decompression sickness in our experiments as compared with the literature data (obtained on unsuited subjects) can be attributed to the peculiar kinematics of movements and excessive pressure in the suit.
The relationship between acute mountain sickness and pulmonary ventilation at 2,835 meters (9,300 ft).
We have demonstrated a small but statistically significant decrease in forced vital capacity and in pulmonary flow rates among 126 persons studied daily for the first three days after arrival at an altitude of 2,835 meters (9,300 ft). Nearly half of these individuals had symptoms attributable to altitude sickness, and those with the most dyspnea and worst headache also showed the greatest changes in pulmonary function studied. We suggest that there is a relationship between the symptoms of altitude sickness and pulmonary function consistent with the appearance of early interstitial or alveolar edema.
[Incidence of acute mountain sickness at intermediate altitude in the Austrian alps].
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[Acute mountain sickness and high altitude edema (author's transl)].
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