High altitude exposure reduces bronchial responsiveness to hypo-osmolar aerosol in lowland asthmatics

An unusually high prevalence of allergic rhinitis at high altitudes in 6-7 year old children - An epidemiological study

Objectives

To compare the epidemiology and disease patterns of allergic rhinitis (AR) at 2 different altitudes in children aged 6-7 years, and subsequently to compare with and augment data from international studies.

Materials and methods

This is a multistage, clustered and stratified random sample study. The study area comprises 2 distinct areas within Yunnan Province, China. Low altitude was represented by Xishuangbanna Prefecture (XB), while high altitude was represented by Diqing Prefecture (DiQ). Each study area was subdivided into 3 sub-areas, and children aged 6-7 years were randomly sampled based on proportion-weighted sampling. The area studied includes the well-known area of Shangri-La city. Questionnaires were distributed and jointly completed by study participants and their parents or guardians, under the guidance of professional medical staff.

Results

2796 valid questionnaires out of 2933 distributed were obtained (survey response rate 95.3%). The prevalence of AR is statistically significantly higher at high altitude (DiQ, 36.0%, 95%CI 33.2-38.8) as compared to low altitude (XB, 19.7%, 95%CI 17.8-21.6) (p < 0.001). Both areas studied had a greater prevalence of AR compared to international data. In both XB and DiQ, male gender, history of early antibiotic use, urban place of birth and place of residence, presence of smokers within the same household, family history of allergic diseases (such as atopic dermatitis), as well as higher parental educational level were all associated with a higher prevalence of AR (p < 0.05). In DiQ, the prevalence of AR in Han ethnicity was greater than that of ethnic minorities (p < 0.05). In XB, being a single child was associated with an increased prevalence of AR compared to those who had siblings (p < 0.05).

Conclusion

Our study found that the prevalence of AR is relatively greater at higher altitudes. Genetic and environmental factors both play an important role in the pathogenesis of AR. While altitude may be an important environmental factor, confounding factors may include humidity, temperature and distribution pattern of common aeroallergens.

Underlying lung disease and exposure to terrestrial moderate and high altitude: personalised risk assessment

Once reserved for the fittest, worldwide altitude travel has become increasingly accessible for ageing and less fit people. As a result, more and more individuals with varying degrees of respiratory conditions wish to travel to altitude destinations. Exposure to a hypobaric hypoxic environment at altitude challenges the human body and leads to a series of physiological adaptive mechanisms. These changes, as well as general altitude related risks have been well described in healthy individuals. However, limited data are available on the risks faced by patients with pre-existing lung disease. A comprehensive literature search was conducted. First, we aimed in this review to evaluate health risks of moderate and high terrestrial altitude travel by patients with pre-existing lung disease, including chronic obstructive pulmonary disease, sleep apnoea syndrome, asthma, bullous or cystic lung disease, pulmonary hypertension and interstitial lung disease. Second, we seek to summarise for each underlying lung disease, a personalized pre-travel assessment as well as measures to prevent, monitor and mitigate worsening of underlying respiratory disease during travel.

Physiological and Biological Responses to Short-Term Intermittent Hypobaric Hypoxia Exposure: From Sports and Mountain Medicine to New Biomedical Applications

In recent years, the altitude acclimatization responses elicited by short-term intermittent exposure to hypoxia have been subject to renewed attention. The main goal of short-term intermittent hypobaric hypoxia exposure programs was originally to improve the aerobic capacity of athletes or to accelerate the altitude acclimatization response in alpinists, since such programs induce an increase in erythrocyte mass. Several model programs of intermittent exposure to hypoxia have presented efficiency with respect to this goal, without any of the inconveniences or negative consequences associated with permanent stays at moderate or high altitudes. Artificial intermittent exposure to normobaric hypoxia systems have seen a rapid rise in popularity among recreational and professional athletes, not only due to their unbeatable cost/efficiency ratio, but also because they help prevent common inconveniences associated with high-altitude stays such as social isolation, nutritional limitations, and other minor health and comfort-related annoyances. Today, intermittent exposure to hypobaric hypoxia is known to elicit other physiological response types in several organs and body systems. These responses range from alterations in the ventilatory pattern to modulation of the mitochondrial function. The central role played by hypoxia-inducible factor (HIF) in activating a signaling molecular cascade after hypoxia exposure is well known. Among these targets, several growth factors that upregulate the capillary bed by inducing angiogenesis and promoting oxidative metabolism merit special attention. Applying intermittent hypobaric hypoxia to promote the action of some molecules, such as angiogenic factors, could improve repair and recovery in many tissue types. This article uses a comprehensive approach to examine data obtained in recent years. We consider evidence collected from different tissues, including myocardial capillarization, skeletal muscle fiber types and fiber size changes induced by intermittent hypoxia exposure, and discuss the evidence that points to beneficial interventions in applied fields such as sport science. Short-term intermittent hypoxia may not only be useful for healthy people, but could also be considered a promising tool to be applied, with due caution, to some pathophysiological states.

Respiratory Health Benefits and Risks of Living at Moderate Altitude

Grissom, Colin K., and Barbara E. Jones. Respiratory health benefits and risks of living at moderate altitude. High Alt Med Biol 19:109-115, 2018.-The respiratory system plays a critical role in the series of physiologic responses that occur at high altitude and allows individuals to adapt to and tolerate hypobaric hypoxia. Persons with underlying lung disease may have complications, but sometimes derive benefits, related to residence at high altitude. This review will focus on health benefits and risks of patients with underlying asthma, chronic obstructive pulmonary disease, pulmonary hypertension, or obstructive sleep apnea, who live at altitudes of 1500 to 4500 m. We will also discuss maladaptive responses of the respiratory system at high altitude in previously healthy persons, including development of pulmonary hypertension and sleep-disordered breathing.

High-altitude alpine therapy and lung function in asthma: systematic review and meta-analysis

We used meta-analysis to measure the effect of high-altitude climate therapy (HACT) on lung function outcomes in asthma, and systematically searched PubMed, Embase and www.elibrary.ru for publications appearing from 1970 to mid-2015. We included studies carried out with children or adults with an exposure of up to 12 weeks at an altitude of ≥1500 m above sea level. Changes in forced expiratory volume in 1 s (FEV₁), FEV₁/vital capacity ratio or peak expiratory flow rate as the HACT intervention outcomes were analysed. We included data for 907 participants (age range 4–58 years) from 21 studies, altogether including 28 substrata based on asthma type or severity. Only three of 21 included studies had high quality, whereas 93% of substudies reported lung function improvement with an overall pooled standardised mean difference (SMD) of 0.53 (95% CI 0.43–0.62). The measured effect of HACT was greater in adults (SMD 0.75, 95% CI 0.63–0.88, n=14) than in children (SMD 0.24, 95% CI 0.09–0.38, n=14). Studies at altitude >2000 m above sea level yielded the same effect as those at lower altitude. Based on a cut-point of a 0.50 change in SMD to define a meaningful clinical difference, HACT appears to have efficacy as an intervention. This extent of benefit appears to be limited to adults with asthma.

High-altitude alpine therapy may be an effective intervention to improve lung function in patients with asthmahttp://ow.ly/u3i23008vU5

Wilderness and adventure travel with underlying asthma

Given the high prevalence of asthma, it is likely that providers working in a pretravel setting will be asked to provide guidance for asthma patients about how to manage their disease before and during wilderness or adventure travel, while providers working in the field setting may need to address asthma-related issues that arise during such excursions. This review aims to provide information to assist providers facing these issues. Relevant literature was identified through the MEDLINE database using a key word search of the English-language literature from 1980 to 2013 using the term "asthma" cross-referenced with "adventure travel," "trekking," "exercise," "exercise-induced bronchoconstriction," "high-altitude," "scuba," and "diving." We review data on the frequency of worsening asthma control during wilderness or adventure travel and discuss the unique aspects of wilderness travel that may affect asthma patients in the field. We then provide a general approach to evaluation and management of asthma before and during a planned sojourn and address 2 particular situations, activities at high altitude and scuba diving, which pose unique risks to asthma patients and warrant additional attention. Although wilderness and adventure travel should be avoided in individuals with poorly controlled disease or worsening control at the time of a planned trip, individuals with well-controlled asthma who undergo appropriate pretravel assessment and planning can safely engage in a wide range of wilderness and adventure-related activities.

Effects of high altitude and cold air exposure on airway inflammation in patients with asthma

AIMS

Eighteen patients with asthma were evaluated during preparation to climb to extreme altitude in order to study the effects of low fractional inspired oxygen (FiO(2)), prolonged exposure to cold air and high altitude on lung function, asthma control and airway inflammation.

METHODS

Spirometry and airway inflammation (fractional exhaled nitric oxide (FeNO) and induced sputum) were studied under different test conditions: hypoxic (FiO(2)=11%) exercise test, 24-hour cold exposure (-5°C) and before, during and after an expedition that involved climbing the Aconcagua mountain (6965 m).

RESULTS

Forced expiratory volume in 1 s (FEV(1)) and FeNO values were slightly lower (p<0.04) after 1 h of normobaric hypoxia. FEV(1) decreased (p=0.009) after 24-hour cold exposure, accompanied by increased sputum neutrophilia (p<0.01). During the expedition FEV(1) and forced vital capacity decreased (maximum FEV(1) decrease of 12.3% at 4300 m) and asthma symptoms slightly increased. After the expedition the Asthma Control Test score and prebronchodilator FEV(1) were reduced (p<0.02), sputum neutrophil count was increased (p=0.04) and sputum myeloperoxidase levels, sputum interleukin 17 mRNA, serum and sputum vascular endothelial growth factor A levels were significantly higher compared with baseline. Patients with asthma with the lowest oxygen saturation during the hypoxic exercise test were more prone to develop acute mountain sickness.

CONCLUSIONS

Exposure to environmental conditions at high altitude (hypoxia, exercise, cold) was associated with a moderate loss of asthma control, increased airway obstruction and neutrophilic airway inflammation. The cold temperature is probably the most important contributing factor as 24-hour cold exposure by itself induced similar effects.

Basic medical advice for travelers to high altitudes

BACKGROUND

High-altitude travel, for mountain climbing, trekking, or sightseeing, has become very popular. Therefore, the awareness of its dangers has increased, and many prospective travelers seek medical advice before setting forth on their trip.

METHODS

We selectively searched the literature for relevant original articles and reviews about acclimatization to high altitude and about high-altitude-related illnesses, including acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) (search in Medline for articles published from 1960-2010).

RESULTS

High-altitude-related illnesses are caused by hypoxia and the resulting hypoxemia in otherwise healthy persons who travel too high too fast, with too little time to become acclimatized. The individual susceptibility to high-altitude-related illness is a further risk factor that can only be recognized in persons who have traveled to high altitudes in the past. In an unselected group of mountain climbers, 50% had AMS at 4500 meters, while 0.5-1% had HACE and 6% had HAPE at the same altitude. Persons with preexisting illnesses, particularly of the heart and lungs, can develop symptoms of their underlying disease at high altitudes because of hypoxia. Thus, medical advice is based on an assessment of the risk of illness in relation to the intended altitude profile of the trip, in consideration of the prospective traveler's suitability for high altitudes (cardiopulmonary performance status, exercise capacity) and individual susceptibility to high-altitude-related illnesses, as judged from previous exposures. The symptoms and treatment of high-altitude-related illnesses should be thoroughly explained.

CONCLUSION

An understanding of the physiology of adaptation to high altitudes and of the pathophysiology and clinical manifestations of high-altitude-related illnesses provides a basis for the proper counseling of prospective travelers, through which life-threatening conditions can be prevented.

Lung disease at high altitude

Large numbers of people travel to high altitudes, entering an environment of hypobaric hypoxia. Exposure to low oxygen tension leads to a series of important physiologic responses that allow individuals to tolerate these hypoxic conditions. However, in some cases hypoxia triggers maladaptive responses that lead to various forms of acute and chronic high altitude illness, such as high-altitude pulmonary edema or chronic mountain sickness. Because the respiratory system plays a critical role in these adaptive and maladaptive responses, patients with underlying lung disease may be at increased risk for complications in this environment and warrant careful evaluation before any planned sojourn to higher altitudes. In this review, we describe respiratory disorders that occur with both acute and chronic exposures to high altitudes. These disorders may occur in any individual who ascends to high altitude, regardless of his/her baseline pulmonary status. We then consider the safety of high-altitude travel in patients with various forms of underlying lung disease. The available data regarding how these patients fare in hypoxic conditions are reviewed, and recommendations are provided for management prior to and during the planned sojourn.

Short-term exposure to hypoxia for work and leisure activities in health and disease: which level of hypoxia is safe?

INTRODUCTION

Exposures to natural and simulated altitudes entail reduced oxygen availability and thus hypoxia. Depending on the level of hypoxia, the duration of exposure, the individual susceptibility, and preexisting diseases, health problems of variable severity may arise. Although millions of people are regularly or occasionally performing mountain sport activities, are transported by airplanes, and are more and more frequently exposed to short-term hypoxia in athletic training facilities or at their workplace, e.g., with fire control systems, there is no clear consensus on the level of hypoxia which is generally well tolerated by human beings when acutely exposed for short durations (hours to several days).

CONCLUSIONS

Available data from peer-reviewed literature report adaptive responses even to altitudes below 2,000 m or corresponding normobaric hypoxia (F(i)O(2) > 16.4%), but they also suggest that most of exposed subjects without severe preexisting diseases can tolerate altitudes up to 3,000 m (F(i)O(2) > 14.5%) well. However, physical activity and unusual environmental conditions may increase the risk to get sick. Large interindividual variations of responses to hypoxia have to be expected, especially in persons with preexisting diseases. Thus, the assessment of those responses by hypoxic challenge testing may be helpful whenever possible.

Fit for high altitude: are hypoxic challenge tests useful?

Altitude travel results in acute variations of barometric pressure, which induce different degrees of hypoxia, changing the gas contents in body tissues and cavities. Non ventilated air containing cavities may induce barotraumas of the lung (pneumothorax), sinuses and middle ear, with pain, vertigo and hearing loss. Commercial air planes keep their cabin pressure at an equivalent altitude of about 2,500 m. This leads to an increased respiratory drive which may also result in symptoms of emotional hyperventilation. In patients with preexisting respiratory pathology due to lung, cardiovascular, pleural, thoracic neuromuscular or obesity-related diseases (i.e. obstructive sleep apnea) an additional hypoxic stress may induce respiratory pump and/or heart failure. Clinical pre-altitude assessment must be disease-specific and it includes spirometry, pulsoximetry, ECG, pulmonary and systemic hypertension assessment. In patients with abnormal values we need, in addition, measurements of hemoglobin, pH, base excess, PaO₂, and PaCO₂ to evaluate whether O₂- and CO₂-transport is sufficient.

Instead of the hypoxia altitude simulation test (HAST), which is not without danger for patients with respiratory insufficiency, we prefer primarily a hyperoxic challenge. The supplementation of normobaric O₂ gives us information on the acute reversibility of the arterial hypoxemia and the reduction of ventilation and pulmonary hypertension, as well as about the efficiency of the additional O₂-flow needed during altitude exposure. For difficult judgements the performance of the test in a hypobaric chamber with and without supplemental O₂-breathing remains the gold standard. The increasing numbers of drugs to treat acute pulmonary hypertension due to altitude exposure (acetazolamide, dexamethasone, nifedipine, sildenafil) or to other etiologies (anticoagulants, prostanoids, phosphodiesterase-5-inhibitors, endothelin receptor antagonists) including mechanical aids to reduce periodical or insufficient ventilation during altitude exposure (added dead space, continuous or bilevel positive airway pressure, non-invasive ventilation) call for further randomized controlled trials of combined applications.

Asthma in patients climbing to high and extreme altitudes in the Tibetan Everest region

OBJECTIVES

The aim of this study was to investigate the behavior of asthma in patients traveling to high and extreme altitudes.

METHODS

Twenty-four Dutch patients with mild asthma did a trekking at high and extreme altitudes (up to 6410 m = 21030 ft) in the Tibetan Everest region. Asthma symptoms, use of asthma medication, symptoms of acute mountain sickness, spirometry, peripheral oxygen saturation, and heart rate were measured at 1300 m (baseline), and at 3875, 4310, 5175, and 6410 m. Asthma symptoms were assessed by means of a modified version of the Asthma Control Test. Symptoms of acute mountain sickness were scored by the Lake Louise self-report questionnaire. The expedition staff, consisting of seven healthy persons, acted as a control group.

RESULTS

In both asthmatics and controls, forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) decreased with increasing altitude, whereas FEV1 as percent of FVC (FEV1%FVC) did not change. In both groups, peak expiratory flow (PEF) increased with increasing altitude. In general, differences in spirometric values between asthmatics and controls were not significant. Asthma symptoms did not change with increasing altitude. During ascent, less than half of the asthma patients increased their medication use. According to the Lake Louise score, no acute mountain sickness occurred, except for in the asthma group at 6410 m, which showed mild acute mountain sickness at that altitude. As expected, peripheral oxygen saturation decreased with increasing altitude in asthmatics and controls, differences between the two groups not being significant. In general, heart rate (at rest) did not change with altitude, except for an increase in asthmatics at 6410 m.

CONCLUSIONS

These results suggest that traveling to high and extreme altitudes is safe for patients with mild asthma.

Mechanisms for lung function impairment and airway hyperresponsiveness following chronic hypoxia in rats

Although chronic normobaric hypoxia (CH) alters lung function, its potential to induce bronchial hyperreactivity (BHR) is still controversial. Thus the effects of CH on airway and tissue mechanics separately and changes in lung responsiveness to methacholine (MCh) were investigated. To clarify the mechanisms, mechanical changes were related to end-expiratory lung volume (EELV), in vivo results were compared with those in vitro, and lung histology was assessed. EELV was measured plethysmographically in two groups of rats exposed to 21 days of CH (11% O(2)) or to normoxia. Total respiratory impedance was measured under baseline conditions and following intravenous MCh challenges (2-18 microg x kg(-1) x min(-1)). The lungs were then excised and perfused, and the pulmonary input impedance was measured, while MCh provocations were repeated under a pulmonary capillary pressure of 5, 10, and 15 mmHg. Airway resistance, tissue damping, and elastance were extracted from the respiratory impedance and pulmonary input impedance spectra. The increases in EELV following CH were associated with decreases in airway resistance, whereas tissue damping and elastance remained unaffected. CH led to the development of severe BHR to MCh (206 +/- 30 vs. 95 +/- 24%, P < 0.001), which was not detectable when the same lungs were studied in vitro at any pulmonary capillary pressure levels maintained. Histology revealed pulmonary arterial vascular remodeling with overexpression of alpha-smooth muscle actin antibody in the bronchial wall. These findings suggest that, despite the counterbalancing effect of the increased EELV, BHR develops following CH, only in the presence of intact autonomous nervous system. Thus neural control plays a major role in the changes in the basal lung mechanics and responsiveness following CH.

Airway responses to methacholine and exercise at high altitude in healthy lowlanders

Peribronchial edema has been proposed as a mechanism enhancing airway responses to constrictor stimuli. Acute exposure to altitude in nonacclimatized lowlanders leads to subclinical interstitial pulmonary edema that lasts for several days after ascent, as suggested by changes in lung mechanics. We, therefore, investigated whether changes in lung mechanics consistent with fluid accumulation at high altitude within the lungs are associated with changes in airway responses to methacholine or exercise. Fourteen healthy subjects were studied at 4,559 and at 120 m above sea level. At high altitude, both static and dynamic lung compliances and respiratory reactance at 5 Hz significantly decreased, suggestive of interstitial pulmonary edema. Resting minute ventilation significantly increased by ∼30%. Compared with sea level, inhalation of methacholine at high altitude caused a similar reduction of partial forced expiratory flow but less reduction of maximal forced expiratory flow, less increments of pulmonary resistance and respiratory resistance at 5 Hz, and similar effects of deep breath on pulmonary and respiratory resistance. During maximal incremental exercise at high altitude, partial forced expiratory flow gradually increased with the increase in minute ventilation similarly to sea level but both achieved higher values at peak exercise. In conclusion, airway responsiveness to methacholine at high altitude is well preserved despite the occurrence of interstitial pulmonary edema. We suggest that this may be the result of the increase in resting minute ventilation opposing the effects and/or the development of airway smooth muscle force, reduced gas density, and well preserved airway-to-parenchyma interdependence.

Bronchial asthma: advice for patients traveling to high altitude

This article examines the possibility of traveling to altitude for patients suffering from bronchial asthma. The mountain environment, the adaptations of the respiratory system to high altitude, the underlying patho-physiologies of asthma, and the recommendations for patients, according to altitude, are discussed. In summary, staying at low altitude has a significant beneficial effect for asthmatic patients, due to the reduction of airway inflammation and the lower response to bronchoconstrictor stimuli; for staying at moderate altitude, there is conflicting information and no clinical data; at high altitude, the environment seems beneficial for well-controlled asthmatics, but intense exercise and upper airway infections (frequent during trekking) can be additional risks and should be avoided. Further, in remote areas health facilities are often difficult to reach.

Prevalence and severity of asthma and allergies in schoolchildren in Lhasa, Tibet

BACKGROUND

The International Study of Asthma and Allergies in Childhood (ISAAC) demonstrated that large variations existed in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis and eczema throughout the world and that environmental factors and lifestyle customs are major determinants of the prevalence and severity of these diseases. However, the relevant data about children living at high-altitude locations were considered to be underreported.

OBJECTIVE

The ISAAC Phase III programme was carried out in Lhasa, the Tibetan Autonomous Region in China, at an elevation of 3658 m above sea level to examine the occurrence of asthma, allergic rhinoconjunctivitis and eczema in schoolchildren aged 13-14 years.

METHODS

All 3196 schoolchildren in eight public junior high schools in urban Lhasa who were confirmed to be 13-14 years old were invited and participated in both written and video questionnaire investigations, among which 3190 pieces of data (49.8% of boys and 50.2% of girls) were validated and analysed.

RESULTS

Among the overall observations, the prevalence of 'having ever experienced wheezing', 'current wheezing' and 'diagnosed to have asthma' was 1.4%, 0.8% and 1.1%, respectively. The prevalence of current exercise-induced asthma and current nocturnal cough was 7.1% and 4.6%, respectively. The current prevalence of allergic rhinoconjunctivitis and eczema was 5.2% and 0.4%, respectively. In addition, the prevalence of rhinoconjunctivitis symptoms during the past 12 months showed no discernable differences throughout the year.

CONCLUSION

The prevalence of asthma, allergic rhinoconjunctivitis and eczema over the past 12 months was the lowest among the centres, that performed ISAAC worldwide.

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 Climate Therapy Reduces Local Airway Inflammation and Modulates Lymphocyte Activation

High-altitude climate therapy is a well-established therapeutic option, which improves clinical symptoms in asthma. However, little is known about the underlying immunological mechanisms. The study investigates the influence of high-altitude climate therapy on airway inflammation and cellular components of specific and unspecific immune response. Exhaled NO significantly decreased within 3 weeks of therapy in patients with allergic and intrinsic, moderate and severe asthma. Interleukin-10 (IL-10)-secreting peripheral blood mononuclear cells (PBMC) increased within 3 weeks of therapy in six of 11 patients, whereas transforming growth factor-beta(1)-secreting PBMC remained stable. Furthermore, monocyte activation, assessed by CD80 expression significantly decreased during therapy. The frequency of CRTH2-expressing T cells decreased, while regulatory T cells (T(reg)) remained stable. FOXP3 and GATA-3 mRNA expression in CD4(+) T cells did not change, while interferon-gamma and IL-13 mRNA expression decreased in eight of 10 patients. The current data demonstrate that high-altitude climate therapy reduces local airway inflammation. Furthermore, monocytes switch towards a tolerogenic phenotype under high-altitude climate therapy. The T(reg)/Th2 ratio increases; however, because of the absence of antigens/allergens, no de novo differentiation of Th2 nor T(reg) cells is observed. The high-altitude climate therapy therefore may form the immunological basis for the endogenous control of allergen-driven diseases.

Respiratory diseases and high altitude

The aim of this paper is to review how preexisting pulmonary diseases can be affected by altitude exposure. Obstructive (asthma and chronic obstructive pulmonary disease or COPD) and restrictive (interstitial pulmonary fibrosis), as well as pulmonary vascular diseases, will be considered, and the goal will be to provide insight and tools to clinicians to optimize the medical condition and thus the life-style of these patients. The underlying pathophysiologies and the effect of hypobaric hypoxia on these diseases will be reviewed such that techniques to assess patients will be appropriate. Therapeutic interventions, including the use of supplemental oxygen, in light of the underlying pathologic processes, will also be discussed.

Event medicine: injury and illness during an expedition-length adventure race

To describe the incidence and type of injury and illness occurring during an expedition-length adventure race and identify those resulting in withdrawal from the event, a prospective cohort study was conducted of the injuries and illness treated during the Subaru Primal Quest Expedition Adventure Race trade mark held in Colorado July 7-16, 2002. All racers, support crewmembers, and race staff were eligible to participate in the study. When a member of the study group received medical care due to an injury or illness, the encounter was recorded on a Medical Encounter Form. If an injury or illness resulted in withdrawal from the race, this was also recorded. Information from the Medical Encounter Forms was used to generate the Medical Log. There were 671 individuals eligible to participate in the study. A total of 243 medical encounters and 302 distinct injuries and illnesses were recorded. There were 179 (59%) injuries and 123 (41%) illnesses. Skin and soft tissue injuries and illness were the most frequent (48%), with blisters on the feet representing the single most common (32.8%). Second was respiratory illness (18.2%), including upper respiratory infection, bronchitis and reactive airway disease-asthma. Respiratory illness was the most common medical reason for withdrawal from the event. Injuries accounted for almost 60% of all injury and illness yet they contributed to less than 15% of the medical withdrawals from the race. Blisters accounted for almost one-third of all conditions treated. Providers of medical support for expedition-length adventure races should be prepared to treat a wide variety of injury and illness.

Climate and the prevalence of symptoms of asthma, allergic rhinitis, and atopic eczema in children

AIMS

To investigate the association between climate and atopic diseases using worldwide data from 146 centres of the International Study of Asthma and Allergies in Childhood (ISAAC).

METHODS

Between 1992 and 1996, each centre studied random samples of children aged 13-14 and 6-7 years (approx. 3000 per age group and centre) using standardised written and video questionnaires on symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema during the past 12 months. Data on long term climatic conditions in the centres were abstracted from one standardised source, and mixed linear regression models calculated to take the clustering of centres within countries into account.

RESULTS

In Western Europe (57 centres in 12 countries), the prevalence of asthma symptoms, assessed by written questionnaire, increased by 2.7% (95% CI 1.0% to 4.5%) with an increase in the estimated annual mean of indoor relative humidity of 10%. Similar associations were seen for the video questionnaire and the younger age group. Altitude and the annual variation of temperature and relative humidity outdoors were negatively associated with asthma symptoms. The prevalence of eczema symptoms correlated with latitude (positively) and mean annual outdoor temperature (negatively).

CONCLUSIONS

Results suggest that climate may affect the prevalence of asthma and atopic eczema in children.

International patterns of the prevalence of pediatric asthma the ISAAC program

Like so much research, the findings from the ISAAC program have raised more questions than they have answered. Despite their limitations, the ISAAC findings provide the basis for further studies to investigate factors that potentially contribute to these international patterns and may lead to novel public health and pharmacologic intervention strategies that reduce the prevalence and severity of asthma worldwide.

Increased resting bronchial tone in normal subjects acclimatised to altitude

BACKGROUND

Normal subjects frequently experience troublesome respiratory symptoms when acclimatised to altitude. Bronchial hyperresponsiveness (BHR) and full and partial flow-volume loops were measured before and after ascent to 5000 m altitude to determine if there are changes in resting bronchial tone and BHR that might explain the symptoms.

METHODS

BHR to histamine was measured using a turbine spirometer to record partial and full flow-volume curves and expressed as log dose slopes. Twenty one subjects were tested at sea level and after acclimatisation at 5000 m altitude.

RESULTS

No significant change in log dose slope measurements of forced expiratory volume in 1 second occurred after acclimatisation, and the maximal expiratory flow with 30% of forced vital capacity remaining (MEF(30%)) rose on the full loop and fell on the partial loop. Their ratio (full divided by partial) rose on average by 0.28 (95% confidence limits 0.14 to 0.42) from the mean (SD) sea level value of 0.87 (0.20).

CONCLUSIONS

There is no increase in BHR in normal subjects acclimatised to altitude but an increase in resting bronchial tone occurs that could be released by deep inspiration. This may be the result of increased cholinergic tone.

Asthma and geographical altitude: an inverse relationship in Mexico

Motivated by the great asthma-prevalence variation throughout the world, we analyzed the rate variation of medical services due to asthma in the 32 Mexican states at the Instituto Mexicano del Seguro Social (approximately 24 million insured subjects). In 1993, a total of 406,036 services were due to asthma, and state rates ranged from 53 to 476 x 10,000 insured subjects. A direct correlation (p < 0.05) was found for single-room house, ascariasis, and rubella rates, but the strongest (inverse) correlation was found for geographical altitude (r = -0.73, p < 10(-5)). Thus, in Mexico, geographical altitude affects the etiological factor(s) responsible for the development of asthma or for the triggering of asthma attacks.