Racing Alaskan Sled Dogs as a Model of “Ski Asthma”

Abstract

Athletes who play sports in cold weather, particularly skaters and cross-country skiers, have an increased prevalence of lower airway disease that is hypothesized to result from repeated penetration of incompletely conditioned air into the lung periphery. In this study, we investigated the hypothesis that canine winter athletes also suffer from increased prevalence of lung disease secondary to hyperpnea with cold air. Bronchoscopy and bronchoalveolar lavage was conducted in elite racing sled dogs 24 to 48 hours after completion of a 1,100-mile endurance race. Bronchoscopic abnormalities were classified as none, mild, moderate, or severe, based on the quantity and distribution of intralumenal debris. Eighty-one percent of the dogs (48 of 59) examined had abnormal accumulations of intralumenal debris, with 46% (27 of 59) classified as moderate or severe, indicating significant accumulation of exudate. Bronchoalveolar lavage obtained from dogs after the race had significantly higher nucleated macrophage and eosinophil counts compared with sedentary control dogs. Our findings support the hypothesis that strenuous exercise in cold environments can lead to lower airway disease and suggest that racing sled dogs may be a useful naturally occurring animal model of the analogous human disease.

Airway Cell Composition at Rest and after an All-out Test in Competitive Rowers

“…Only bronchial epithelial cells (BEC) tended to increase after exercise, and their change correlated with exercise V E. The mild changes we observed compared with the severe epithelial damage found in dogs and horses after exercise in cold weather (7,8) are likely explained by different experimental settings, as our tests were conducted in the laboratory under standard environmental conditions.…”

“…Increased neutrophils, eosinophils, and lymphocytes, alone or in combination, were reported in the airways of runners (3), swimmers (4,14), ice hockey players (18), and skiers (17). Such variability likely reflects the response to both exercise and environmental factors, as exercise hyperpnea would magnify the effects of exposure to cold and dry air in winter sports (7,17,18), allergens and pollutants in long distance runners (15), or irritants in swimmers (4,14). The effects of exercise at competitive level seem to be reversible, as the increase in airway inflammatory cells returned toward normal upon cessation of training (16).…”

The breathless adolescent asthmatic athlete

“…Later, SUE-CHU et al [36] showed that during one competitive winter season, adolescent crosscountry skiers developed signs of inflammation (lymphoid follicles and deposition of tenascin) in their bronchial biopsies whether they were asthmatic or not. These findings were later confirmed in animal studies: mice exercised by running developed signs of inflammation and epithelial damage in their lungs compared with sedentary mice [37]; Alaskan sledge dogs were examined by bronchoscopy and bronchoalveolar lavage before and after a sledge race across Alaska (USA) with similar findings [38]. These findings were recently replicated in humans, as increased levels of bronchial epithelial cells were found in induced sputum of amateur endurance runners after repeated half-marathon races, in addition to apoptosis of bronchial cells after the races.…”

Mechanisms of asthma development in elite athletes

“…Mice, exercised by running, developed inflammation and epithelial damage in their airways compared with sedentary mice [33]. This was also found in Alaskan sledge dogs, examined by bronchoscopy and bronchoalveolar lavage before and after a sledge race across Alaska [34]. The epithelial damage has also been found to be of major importance in experimental image: Markus Bernet studies [35], suggesting this to be the primary lesion in asthma and exercise-induced bronchoconstriction (EIB).…”