Smoking, acute mountain sickness and altitude acclimatisation: a cohort study.

RATIONALE: The relationship between cigarette smoking and acute mountain sickness (AMS) is not clear. OBJECTIVE: To assess AMS risk and altitude acclimatisation in relation to smoking. METHODS: 200 healthy non-smokers and 182 cigarette smokers were recruited from Han lowland workers. These were men without prior altitude exposure, matched for age, health status and occupation, who were transported to an altitude of 4525 masl. MEASUREMENTS: AMS, smoking habits, arterial saturation (SpO2), haemoglobin (Hb), lung function and mean pulmonary artery pressure (PAPm) were assessed upon arrival and after 3 and 6 months. MAIN RESULTS: Compared with non-smokers, smokers had a lower incidence of AMS and lower AMS scores than non-smokers upon arrival; higher Hb and PAPm associated with lower SpO2 at 3 and 6 months at altitude; and lower forced expiratory volume in 1 s and maximal voluntary ventilation at 3 and 6 months. CONCLUSIONS: Smoking slightly decreases the risk of AMS but impairs long-term altitude acclimatisation and lung function during a prolonged stay at high altitude.

Who are more at risk for acute mountain sickness: a prospective study in Qinghai-Tibet railroad construction workers on Mt. Tanggula.

BACKGROUND: It is important to determine the incidence of acute mountain sickness (AMS) among workers at altitudes between 3500 m and 5000 m on Mt. Tanggula during the construction of the Qinghai-Tibet railroad. This study explored the risk factors predisposing workers to developing AMS and attempted to develop more effective ways of preventing and treating AMS. METHODS: A total of 11,182 workers were surveyed by completing twice daily a Lake Louise questionnaire, and a score ≥ 3 indicated AMS. The contributing risk factors were assessed for at least 2 months for the duration of the study in the years from 2001 to 2003. A risk model was developed by multiple Logistic regression. Standard statistical methods were used to analyze data. RESULTS: AMS occurred in 56% of workers working at high altitudes on Mt. Tanggula. The incidence of AMS increased with increasing altitude. Rapid ascent to an altitude above 3500 m, sea-level or lowland newcomers, young people under 25 years of age, heavy physical exertion, obese person, and arterial oxygen saturation (SaO2) below 80% were independent AMS risk factors. No significant association was found between AMS and sex or taking Rhodiola. Medical education contributed to an early diagnosis of AMS. CONCLUSIONS: This study used the Lake Louise scoring system suggesting that it is a well-validated standard for field evaluation of AMS and for making an early diagnosis. These studies have described many variables regarding risk factors for the development of AMS. Risk factors which can be modified should be attended to, and the physicians should carry out check-ups and tests to identify subjects who are more at risk. Prevention consists in continuous gradual ascent, medical education, and prompt descent to avoid progression in patients with serious AMS. It is most important to effectively control the risk factors of AMS.

Reduced incidence and severity of acute mountain sickness in Qinghai-Tibet railroad construction workers after repeated 7-month exposures despite 5-month low altitude periods.

The construction of the Qinghai-Tibet railroad provided a unique opportunity to study the relation between intermittent altitude exposure and acute mountain sickness (AMS). For 5 yr, workers spent 7-month periods at altitude interspaced with 5-month periods at sea level; the incidence, severity, and risk factors of AMS were prospectively investigated. Six hundred lowlanders commuted for 5 yr between near sea level and approximately 4500 m and were compared to 600 other lowland workers, recruited each year upon their first ascent to high altitude as newcomers, and to 200 Tibetan workers native to approximately 4500 m. AMS was assessed with the Lake Louise Scoring System. The incidence and severity of AMS in commuters were lower upon each subsequent exposure, whereas they remained similar in newcomers each year. AMS susceptibility was thus lowered by repeated exposure to altitude. Repeated exposure increased resting Sao(2) and decreased resting heart rate. Tibetans had no AMS, higher Sao(2), and lower heart rates. In conclusion, repetitive 7-month exposures increasingly protect lowlanders against AMS, even when interspaced with 5-month periods spent at low altitude, but do not allow attaining the level of adaptation of altitude natives.

Who should not go high: chronic disease and work at altitude during construction of the Qinghai-Tibet railroad.

From 2001 to 2005, a new railroad linking Beijing with Lhasa was built by more than 100,000 workers, of whom 80% traveled from their lowland habitat to altitudes up to 5000 m to work on the railroad. We report on the medical conditions of 14,050 of these altitude workers, specifically with regard to preexisting illness. All subjects were seen at low and high altitude. Average age was 29.5 +/- 7.4 (SD) yr, range 20 to 62 yr; 98.8% of the subjects were men and 1.2% were women. Overall incidence of AMS upon first-time exposure was 51%, that of HACE 0.28%, and that of HAPE 0.49%. About 1% of the subjects were hypertensive before altitude exposure. Those with blood pressure >or=160/95 were excluded from employment at altitude. Altitude exposure led to a greater increase of blood pressure in hypertensives compared to normotensives. On prealtitude screening prevalence of cardiac arrhythmias was 0.33%. Since the majority of these were rather benign and occurring in young and otherwise healthy subjects, we allowed altitude employment. Follow-up at altitude was uneventful. Subjects with coronary heart disease and diabetes were excluded from altitude employment. Obesity was a risk factor for acute mountain sickness and for reduced work performance at altitude. Overweight subjects lost more weight during their altitude stay than subjects with normal weight. Altitude exposure was a risk factor for upper gastrointestinal tract bleeding, especially in combination with alcohol, aspirin, and dexamethasone intake. Asthmatic subjects generally did better at altitude compared to low altitude, with the exception of one subject who experienced an asthma episode from pollen exposure. In conclusion, careful evaluation of preexisting chronic illness and risk factors allowed prevention of altitude deterioration of a preexisting health condition, all the while allowing subjects with some specific conditions to work and live at altitude without problems.

High-altitude gastrointestinal bleeding: an observation in Qinghai-Tibetan railroad construction workers on Mountain Tanggula.

AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis. METHODS: From 2001 to October 2003, we studied GIB in 13502 workers constructing the railroad on Mountain Tanggula which is 4905 m above the sea level. The incidence of GIB in workers at different altitudes was recorded. Endoscopy was performed when the workers evacuated to Golmud (2808 m) and Xining (2261 m). The available data on altitude GIB were analyzed. RESULTS: The overall incidence of GIB was 0.49% in 13502 workers. The incidence increased with increasing altitude. The onset of symptoms in most patients was within three weeks after arrival at high altitude. Bleeding manifested as hematemesis, melaena or hematochezia, and might be occult. Endoscopic examination showed that the causes of altitude GIB included hemorrhage gastritis, gastric ulcer, duodenal ulcer, and gastric erosion. Experimental studies suggested that acute gastric mucosal lesion (AGML) could be induced by hypoxic and cold stress, which might be the pathogenesis of altitude GIB. Those who consumed large amount of alcohol, aspirin or dexamethasone were at a higher risk of developing GIB. Persons who previously suffered from peptic ulcer or high-altitude polycythemia were also at risk of developing GIB. Early diagnosis, evacuation, and treatment led to early recovery. CONCLUSION: GIB is a potentially life threatening disease, if it is not treated promptly and effectively. Early diagnosis, treatment and evacuation lead to an early recovery. Death due to altitude GIB can be avoided if early symptoms and signs are recognized.