Operation Everest II: Spirometric and Radiographic Changes in Acclimatized Humans at Simulated High Altitudes

Welsh, Carolyn H.; Wagner, Peter D.; Reeves, John Τ.; Lynch, David A.; Cink, Thomas M.; Armstrong, John D.; Malconian, M. K.; Rock, Paul; Houston, C. Stuart

doi:10.1164/ajrccm/147.5.1239

Cited by 66 publications

(47 citation statements)

References 20 publications

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“…These findings can be explained by reduced air density, and are in agreement with the results of previous studies [5,13,33,43]. Despite normal Reff and sRaw and FEV1, both were improved somewhat by salbutamol, but this improvement was below that considered to be a significant bronchodilator response and was independent of altitude and preceding exercise.…”

Section: Lung Volumessupporting

confidence: 92%

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

Dehnert¹,

Luks²,

Schendler

et al. 2009

Eur Respir J

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The aim of the present study was to better understand previously reported changes in lung function at high altitude.Comprehensive pulmonary function testing utilising body plethysmography and assessment of changes in closing volume were carried out at sea level and repeatedly over 2 days at high altitude (4,559 m) in 34 mountaineers.In subjects without high-altitude pulmonary oedema (HAPE), there was no significant difference in total lung capacity, forced vital capacity, closing volume and lung compliance between low and high altitude, whereas lung diffusing capacity for carbon monoxide increased at high altitude. Bronchoconstriction at high altitude could be excluded as the cause of changes in closing volume because there was no difference in airway resistance and bronchodilator responsiveness to salbutamol. There were no significant differences in these parameters between mountaineers with and without acute mountain sickness. Mild alveolar oedema on radiographs in HAPE was associated only with minor decreases in forced vital capacity, diffusing capacity and lung compliance and minor increases in closing volume.Comprehensive lung function testing provided no evidence of interstitial pulmonary oedema in mountaineers without HAPE during the first 2 days at 4,559 m. Data obtained in mountaineers with early mild HAPE suggest that these methods may not be sensitive enough for the detection of interstitial pulmonary fluid accumulation.

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Section: Lung Volumessupporting

confidence: 92%

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

Dehnert¹,

Luks²,

Schendler

et al. 2009

Eur Respir J

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show abstract

“…In contrast to others, an increase in FEV1 and FVC was found in the present subjects [11,12,20,25,26]. This could be due to the relatively short duration of stay at high altitude, as the typical reduction in FEV1 or FVC is seen in subjects with exposure to severe hypoxia (Pa,O 2 ,6.6 kPa) for more than a few hours or with additional strenuous exercise [27].…”

Section: Discussioncontrasting

confidence: 94%

“…In accordance with previously published results in healthy subjects, an increase in TLC, RV and ITGV, along with an increase in expiratory flow rates, was found [20][21][22][23]. This increase is probably due to the reduced gas density at 2,650 m compared to baseline [22,24].…”

Section: Discussionsupporting

confidence: 92%

Lung function in adults with cystic fibrosis at altitude: impact on air travel

Fischer

Sm²,

K³

et al. 2005

Eur Respir J

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Current guidelines for air travel state that patients with chronic respiratory diseases are required to use oxygen if their in-flight arterial oxygen tensions (Pa,O 2 ) drop below 6.6 kPa. This recommendation may not be strictly applicable to cystic fibrosis patients, who may tolerate lower Pa,O 2 for several hours without clinical symptoms.Lung function, symptoms, blood gas levels and signs of pulmonary hypertension were studied in 36 cystic fibrosis patients at altitudes of 530 m and, after 7 h, 2,650 m. A hypoxia inhalation test (inspiratory oxygen fraction 0.15) was performed at low altitude in order to predict high-altitude hypoxaemia.Median Pa,O 2 dropped from 9.8 kPa at low altitude to 7.0 kPa at high altitude. Mild exercise at a workload of 30 W further decreased Pa,O 2 . Two-thirds of all patients exhibited Pa,O 2 of ,6.6 kPa during exercise and, except for one patient, were asymptomatic. Patients were significantly less obstructed at an altitude of 2,650 m. Low forced expiratory volume in one second at baseline was associated with a low Pa,O 2 at altitude.It is concluded that cystic fibrosis patients with baseline arterial oxygen tensions of .8.0 kPa safely tolerate an altitude of 2,650 m for several hours under resting conditions. The risk assessment of low in-flight oxygenation should encompass the whole clinical situation of cystic fibrosis patients, with special attention being paid to the presence of severe airway obstruction.

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“…In patients with chronic obstructive pulmonary disease, theophylline was shown to improve oxygenation as well as the forced expiratory volume in one second [15,22]. Similar effects can be expected in subjects acutely exposed to hypobaric hypoxia [23]. Furthermore, theophylline is able to improve central respiratory drive and, therefore, to stimulate a blunted hypoxic ventilatory response in AMS-susceptible subjects [24].…”

Section: Discussionmentioning

confidence: 74%

Theophylline improves acute mountain sickness

et al. 2000

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A randomized two-part study was conducted in order to determine the efficacy of theophylline in the treatment of acute mountain sickness during fast ascent to altitudes >2,500 m.Fourteen healthy male subjects participated in a randomized single-blind placebocontrolled crossover study carried out in a decompression chamber (simulated altitude 4,500 m). A second randomized single-blind, placebo-controlled study was conducted at a high-altitude research laboratory (3,454 m) and included 21 healthy male subjects. The study medication was either 375 mg oral slow-release theophylline (250 mg if <70 kg) or a matched placebo tablet taken twice daily. The acute mountain sickness score (AMSS) was assessed three times a day, beginning 18 h prior to altitude exposure and continuing for 18 h after altitude exposure. In addition, measurements of respiratory frequency, pulse rate, oxygen saturation and arterial blood gas levels were performed.Acute mountain sickness was significantly reduced by theophylline during the decompression chamber study (mean SD 1.2 0.9) with placebo versus 3.6 0.8 with theophylline; p=0.03). During the high-altitude study, subjects with theophylline showed a significantly lower AMSS on arrival and after 18 h at altitude (0.6 versus 2.3, p=0.03). Oxygenation was improved in both parts of the study.In conclusion, oral slow-release theophylline improves acute mountain sickness. Eur Respir J 2000; 15: 123±127. This study was supported, in part, by Byk Gulden, Constance, Germany.Acute mountain sickness (AMS) is a frequent medical disorder in travellers who rapidly ascend to altitudes >2,500 m [1]. When altitudes >4,000 m are reached within hours, only few do not have at least mild symptoms. The symptoms of mild AMS include headache, dizziness, fatigue, gastrointestinal symptoms and sleep disturbance. During prolonged stay at high altitude, symptoms improve usually within 24±48 h.The pathogenesis of AMS is not fully understood, but it is generally agreed that the main underlying cause is hypoxia, which initiates the pathogenetic processes leading to AMS. Hypoxia is thought to cause water retention or a shift of water from intracellular to extracellular compartments [2], increase microvascular permeability [3] and increase cerebral blood flow [4]. All of these factors may contribute to AMS, although the role of enhanced cerebral blood flow remains controversial [5].AMS is normally best prevented by ascending slowly to high altitude. However, when rapid ascent is necessary (i.e. during rescue operations or passive transportation to high altitude), medical prophylaxis may be indicated. Acetazolamide at a dose of 250 mg twice daily and dexamethasone at doses of >4 mg twice daily have been reported effective in the preventive treatment of AMS [6,7].The effects of theophylline on AMS have not been studied, although its pharmacological profile would seem to predispose this substance to the treatment of AMS. The multiple pharmacological effects of theophylline (a phosphodiesterase inhibitor) are well cha...

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Operation Everest II: Spirometric and Radiographic Changes in Acclimatized Humans at Simulated High Altitudes

Cited by 66 publications

References 20 publications

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

Lung function in adults with cystic fibrosis at altitude: impact on air travel

Theophylline improves acute mountain sickness

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