Airway cooling and mucosal injury during cold weather exercise

Abstract

SummaryIn human subjects that exercise strenuously in cold weather, there is evidence that hyperventilation with cold air leads to peripheral airway cooling, desiccation and mucosal injury. Our hypothesis was that hyperventilation with cold air can result in penetration of unconditioned air (air that is not completely warmed and humidified) into the peripheral airways of exercising horses, resulting in peripheral airway mucosal injury. To test this hypothesis, a thermister-tipped catheter was inserted through the midcervical trachea and advanced into a sublobar bronchus in three horses that cantered on a treadmill at 6.6 m/s while breathing cold (5°C) air. The mean (± s.e.) intraairway temperature during cantering was 33.3 ± 0.4°C, a value comparable to the bronchial lumen temperatures measured in man during maximal exercise while breathing subfreezing dry air. In a second experiment, 6 fit Thoroughbred racehorses with satisfactory performance were used to determine whether strenuous exercise in cold conditions can produce airway injury. Horses were assigned to Exercise (E) or Control (C) groups in a random crossover design. Samples of bronchoalveolar lavage fluid (BALF) in the E treatment were recovered within 30 min of galloping exercise in 4°C, 100% relative humidity (E), while in C BALF samples were obtained when the horses had not performed any exercise for at least 48 h prior. Ciliated epithelial cells in BALF were higher in E than in the C treatment. Similar results have been found in human athletes and laboratory animal models of cold weather exercise. These results support the hypothesis that, similar to man, horses that exercise in cold weather experience peripheral airway mucosal injury due to the penetration of unconditioned air.Furthermore, these results suggest that airway cooling and desiccation may be a factor in airway inflammation commonly found in equine athletes.

Asthma, airway inflammation and epithelial damage in swimmers and cold-air athletes

“…The epithelial shedding may also be a result of specific environmental exposures, particularly in chlorinated swimming pools. Additionally, cold, dry air may be an important stimulus for epithelial cell shedding in the human nose at rest [21] and in horses' airways during exercise [22]. Repeated cold-air inhalation may also be responsible for AHR in cold-air athletes, through repeated exposure to plasma-derived products, resulting from the repair process induced by airway dehydration [2].…”

Bronchial epithelial damage after a half-marathon in nonasthmatic amateur runners

“…Data on temperature and humidity and air pollutants (PM 10 and ozone) were obtained by the environmental agency Azienda Municipalizzata Igiene Ambientale for the week preceding the race and the day of the race as previously described (7).…”

“…In mice, endurance training caused increased inflammatory cells and damage of bronchial epithelium in small airways (8). Bronchial epithelial cells damage also occurred in horses after exercise while breathing cold air (10). In dogs challenged with repeated insufflation of dry and cold air, loss of ciliated epithelium and airway remodeling occurred (11).…”

Environmental conditions, air pollutants, and airway cells in runners: A longitudinal field study

“…With regard to exercise, bronchial epithelial cells may be affected by osmotic changes triggered by exercise hyperventilation (Anderson & Kippelen, 2008;Hashimoto et al, 1999). Bronchial epithelial damage was found after exercise in horses breathing cold air (Davis, Lockard, Marlin, & Freed, 2002), and in dogs challenged at rest with dry air insufflations into a pulmonary segment (Davis et al, 2003). In humans, bronchial epithelial cells in induced sputum tended to increase after very heavy exercise (Morici et al, 2004).…”