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Bronchial asthma and airway hyperresponsiveness at high altitude

The mountain climate can modify respiratory function and bronchial responsiveness of asthmatic subjects. Hypoxia, hyperventilation of cold and dry air and physical exertion may worsen asthma or enhance bronchial hyperresponsiveness while a reduction in pollen and pollution may play an important role in reducing bronchial inflammation. At moderate altitude (1,500-2,500 m), the main effect is the absence of allergen and pollutants. We studied bronchial hyperresponsiveness to both hyposmolar aerosol and methacholine at sea level (SL) and at high altitude (HA; 5,050 m) in 11 adult subjects (23-48 years old, 8 atopic, 3 nonatopic) affected by mild asthma. Basal FEV1 at SL and HA were not different (p = 0.09), whereas the decrease in FEV1 induced by the challenge was significantly higher at SL than at HA. (1) Hyposmolar aerosol: at SL the mean FEV1 decreased by 28% from 4.32 to 3.11 liters; at 5,050 m by 7.2% from 4.41 to 4.1 liters (p < 0.001). (2) Methacholine challenge: at SL PD20-FEV1 was 700 micrograms and at HA > 1,600 micrograms (p < 0.005). In 3 asthmatic and 5 nonasthmatic subjects plasma levels of cortisol were also measured. The mean value at SL was 265 nmol and 601 nmol at HA (p < 0.005). We suppose that the reduction in bronchial response might be mainly related to the protective role carried out by the higher levels of cortisol and, as already known, catecholamines.

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High-altitude exposure reduces inspiratory muscle strength.

It was the aim of the study to assess the maximal pressure generated by the inspiratory muscles (MIP) during exposure to different levels of altitude (i.e., hypobaric hypoxia). Eight lowlanders (2 females and 6 males), aged 27 - 46 years, participated in the study. After being evaluated at sea level, the subjects spent seven days at altitudes of more than 3000 metres. On the first day, they rode in a cable car from 1200 to 3200 metres and performed the first test after 45 - 60 minutes rest; they then walked for two hours to a mountain refuge at 3600 metres, where they spent three nights (days 2 - 3); on day 4, they walked for four hours over a glacier to reach Capanna Regina Margherita (4559 m), where they spent days 5 - 7. MIP, flow-volume curve and SpO (2) % were measured at each altitude, and acute mountain sickness (Lake Louise score) was recorded. Increasing altitude led to a significant decrease in resting SpO (2) % (from 98 % to 80 %) and MIP (from 134 to 111 cmH (2)O) (baseline to day 4: p < 0.05); there was an improvement in SpO (2) % and a slight increase in MIP during the subsequent days at the same altitude. Expiratory (but not inspiratory) flows increased, and forced vital capacity and FEF (75) decreased at higher altitudes. We conclude that exposure to high altitude hypoxia reduces the strength of the respiratory muscles, as demonstrated by the reduction in MIP and the lack of an increase in peak inspiratory flows. This reduction is more marked during the first days of exposure to the same altitude, and tends to recover during the acclimatisation process.

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Growth and nutritional status of Tibetan children at high altitude

Growth and development are clearly affected by high-altitude exposure to hypoxia, nutritional stress, cold or a combination of these factors. Very little research has been conducted on the growth and nutritional status of children living on the Tibetan Plateau. The present study evaluated the environmental impact on human growth by analyzing anthropometric characteristics of Tibetan children aged 8-14, born and raised above 4000 m altitude on the Himalayan massif in the prefecture of Shegar in Tibet Autonomous Region. Data on anthropometric traits, never measured in this population, were collected and the nutritional status was assessed. A reference data set is provided for this population. There was no evidence of wasting but stunting was detected (28.3%). Children permanently exposed to the high-altitude environment above 4000 m present a phenotypic form of adaptation and a moderate reduction in linear growth. However, it is also necessary to consider the effects of socioeconomic deprivation.

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Relationship between individual ventilatory response and acute renal water excretion at high altitude.

We tested the hypothesis that the individual ventilatory adaptation to high altitude (HA, 5050 m) may influence renal water excretion in response to water loading. In 8 healthy humans (33+/-4 S.D. years) we studied, at sea level (SL) and at HA, resting ventilation (VE), arterial oxygen saturation (SpO2), urinary output after water loading (WL, 20 mL/kg), and total body water (TBW). Ventilatory response to HA was defined as the difference in resting VE over SpO2 (DeltaVE/DeltaSpO2) from SL to HA. At HA, a significant increase in urinary volume after the first hour from WL (%WLt0-60) was observed. Significant correlations were found between DeltaVE/DeltaSpO2 versus %WLt0-60 at HA and versus changes in TBW, from SL to HA. In conclusion, in healthy subjects the ventilatory response to HA influences water balance and correlates with kidney response to WL. A higher ventilatory response at HA, allowing a more efficient water renal handling, is likely to be a protective mechanisms from altitude illness.

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Bronchial asthma and airway hyperresponsiveness at high altitude

The mountain climate can modify respiratory function and bronchial responsiveness of asthmatic subjects. Hypoxia, hyperventilation of cold and dry air and physical exertion may worsen asthma or enhance bronchial hyperresponsiveness while a reduction in pollen and pollution may play an important role in reducing bronchial inflammation. At moderate altitude (1,500-2,500 m), the main effect is the absence of allergen and pollutants. We studied bronchial hyperresponsiveness to both hyposmolar aerosol and methacholine at sea level (SL) and at high altitude (HA; 5,050 m) in 11 adult subjects (23-48 years old, 8 atopic, 3 nonatopic) affected by mild asthma. Basal FEV1 at SL and HA were not different (p = 0.09), whereas the decrease in FEV1 induced by the challenge was significantly higher at SL than at HA. (1) Hyposmolar aerosol: at SL the mean FEV1 decreased by 28% from 4.32 to 3.11 liters; at 5,050 m by 7.2% from 4.41 to 4.1 liters (p < 0.001). (2) Methacholine challenge: at SL PD20-FEV1 was 700 micrograms and at HA > 1,600 micrograms (p < 0.005). In 3 asthmatic and 5 nonasthmatic subjects plasma levels of cortisol were also measured. The mean value at SL was 265 nmol and 601 nmol at HA (p < 0.005). We suppose that the reduction in bronchial response might be mainly related to the protective role carried out by the higher levels of cortisol and, as already known, catecholamines.

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Efficacy and tolerability of yoga breathing in patients with chronic obstructive pulmonary disease: a pilot study

Yoga-derived breathing has been reported to improve gas exchange in patients with chronic heart failure and in participants exposed to high-altitude hypoxia. We investigated the tolerability and effect of yoga breathing on ventilatory pattern and oxygenation in patients with chronic obstructive pulmonary disease (COPD). METHODS: Patients with COPD (N = 11, 3 women) without previous yoga practice and taking only short-acting ß2-adrenergic blocking drugs were enrolled. Ventilatory pattern and oxygen saturation were monitored by means of inductive plethysmography during 30-minute spontaneous breathing at rest (sb) and during a 30-minute yoga lesson (y). During the yoga lesson, the patients were requested to mobilize in sequence the diaphragm, lower chest, and upper chest adopting a slower and deeper breathing. We evaluated oxygen saturation (SaO2%), tidal volume (VT), minute ventilation (E), respiratory rate (i>f), inspiratory time, total breath time, fractional inspiratory time, an index of thoracoabdominal coordination, and an index of rapid shallow breathing. Changes in dyspnea during the yoga lesson were assessed with the Borg scale.

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Respiratory function at different altitudes

For the evaluation of a respiratory test at high altitude, several factors must be taken into account: the decreased barometric pressure, the decreased density of air and the degree of acclimatization which is related to the altitude and to the length of exposure. Several studies have shown a reduction in forced vital capacity (FVC) at high altitude and using simulated conditions, mainly related to an increase in pulmonary blood volume and development of interstitial edema. To assess the daily spirometric patterns during ascending to high altitudes we studied 17 healthy subjects at both Capanna Regina Margherita on the Italian Alps (4,559 m) and the Pyramid Laboratory in Nepal (5,050 m). Respiratory function tests were performed every day. Peak expiratory flow values significantly increased. The mean percent increase was 15% at 3,200 and 3,600 m and 26% at 4,559 m. FVC and MEF25 values showed a significant decrease (p < 0.005) during the first days above 3,500 m and improved only after several days spent above this altitude. For each subject the maximal reductions in FVC and maximal expiratory flow (MEF) at 25% of FVC however were found on different days. In our opinion, these data support the hypothesis that at high altitude the respiratory function can be affected by the presence of an increased pulmonary blood volume and/or the development of interstitial edema. The observed changes in forced expiration curves at high altitude seem to reflect the degree of acclimatization that is related to the individual susceptibility, to the altitude reached and to the duration of the exposure. These changes are transient and resolve after returning to sea level.

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Comparison of a Visual Analogue Scale and Lake Louise Symptom Scores for Acute Mountain Sickness

Assessment of the presence and severity of acute mountain sickness (AMS) is based on subjective reporting of the sensation of symptoms. The Lake Louise symptom scoring system (LLS) uses categorical variables to rate the intensity of AMS-related symptoms (headache, gastrointestinal distress, dizziness, fatigue, sleep quality) on 4-point ordinal scales; the sum of the answers is the LLS self-score (range 0–15). Recent publications indicate a potential for a visual analogue scale (VAS) to quantify AMS. We tested the hypothesis that overall and single-item VAS and LLS scores scale linearly. We asked 14 unacclimatized male subjects [age 41 (14), mean (SD) yr; height 176 (3)?cm; weight 75 (9)?kg] who spent 2 days at 3647?m and 4 days at 4560?m to fill out LLS questionnaires, with a VAS for each item (i) and a VAS for the overall (o) sensation of AMS, twice a day (n?=?172). Even though correlated (r?=?0.84), the relationship between LLS(o) and VAS(o) was distorted, showing a threshold effect for LLS(o) scores below 5, with most VAS(o) scores on one side of the identity line. Similar threshold effects were seen for the LLS(i) and VAS(i) scores. These findings indicate nonlinear scaling characteristics that render difficult a direct comparison of studies done with either VAS or LLS alone

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Bronchial asthma and airway hyperresponsiveness at high altitude

The mountain climate can modify respiratory function and bronchial responsiveness of asthmatic subjects. Hypoxia, hyperventilation of cold and dry air and physical exertion may worsen asthma or enhance bronchial hyperresponsiveness while a reduction in pollen and pollution may play an important role in reducing bronchial inflammation. At moderate altitude (1,500-2,500 m), the main effect is the absence of allergen and pollutants. We studied bronchial hyperresponsiveness to both hyposmolar aerosol and methacholine at sea level (SL) and at high altitude (HA; 5,050 m) in 11 adult subjects (23-48 years old, 8 atopic, 3 nonatopic) affected by mild asthma. Basal FEV1 at SL and HA were not different (p = 0.09), whereas the decrease in FEV1 induced by the challenge was significantly higher at SL than at HA. (1) Hyposmolar aerosol: at SL the mean FEV1 decreased by 28% from 4.32 to 3.11 liters; at 5,050 m by 7.2% from 4.41 to 4.1 liters (p < 0.001). (2) Methacholine challenge: at SL PD20-FEV1 was 700 micrograms and at HA > 1,600 micrograms (p < 0.005). In 3 asthmatic and 5 nonasthmatic subjects plasma levels of cortisol were also measured. The mean value at SL was 265 nmol and 601 nmol at HA (p < 0.005). We suppose that the reduction in bronchial response might be mainly related to the protective role carried out by the higher levels of cortisol and, as already known, catecholamines.

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Problems of High Altitude Medicine and Biology

This book is directly derived from a NATO-sponsored international meeting on problems of high altitude medicine and biology, which was held on the shores of lake of Issyk-Kul, in Kyrghyzstan, in June 5-6, 2006. The meeting was remarkable by several aspects. The participants enjoyed the beauty of the blue waters of this 1610 m high sacred lake, with stunning view on the Tien Shan mountain range at a distance, and, most of all, the wonderful Kyrghyz hospitality and friendship. It was a surprise for several European and North and South-American scientists to discover the still on-going momentum high level altitude physiology research, which was extremely active but insufficiently acknowledged in this remote Central Asian country at the time of the USSR. Accordingly, the setting was perfect for numerous positive scientific interactions, exchanges of ideas, and structuring of new international collaborations. Overall, the meeting was an ideal mix of cell biology, integrative physiology and medical applications. Thanks to the efforts of both English and Russian speaking scientist participants, this comes out very well in this book. Hypoxia is and remains a major public health issue in many populated mountainous areas all over the world. We are sure that this book will be become a long-lasting essential reference.

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