Effects of inhalation of albuterol sulphate, ipratroprium bromide and frusemide on breathing mechanics and gas exchange in healthy exercising horses

The possibility that pre-exercise inhalation of bronchodilator by healthy h orses could improve their mechanics of breathing and enhance performance wa s investigated. Ipratropium bromide (0.35 mug/kg bwt; n = 7) was administer ed by nebulisation 30 min before exercise and frusemide (1 mg/kg bwt; n = 6 ) was given in the same manner 2 h before exercise, Albuterol sulphate (360 and 720 mug; n = 7) were administered with a metered dose inhaler 2 h befo re exercise. Each drug was investigated independently of the others using c ross-over protocols, Horses completed incremental exercise tests and oxygen consumption, carbon dioxide production, arterial blood gases, heart rate a nd measures of breathing mechanics including total pulmonary resistance (R- L) and nasopharyngeal resistance (R-L) were determined for each exercise in tensity. The resistance of the lower airways was calculated subsequently fr om the difference between R-L and R-U. None of the drugs tested had an effe ct on any of the variables measured, possibly because maximal bronchodilati on is stimulated in healthy horses by the normal sympathoadrenergic respons e to exercise. Therefore, the pre-exercise inhalation of a bronchodilator b y a healthy horse is unlikely to improve performance capacity.