The regulation of respiratory resistance in exercising horses

摘要: Horses display remarkable aerobic capabilities, attaining during muscular exercise a maximal rate of oxygen consumption about 30-fold higher than the resting value, and 2.5-fold that other mammals similar body mass. Under these circumstances an enormous mechanical burden is expected to impinge on equine respiratory pump regulatory mechanisms aiming minimize this load may play important role in determining adequacy system metabolic requirements. The behaviour has been investigated horses at rest treadmill locomotion different velocities gaits. During hyperpnoea, exhibit significant reduction lung viscous resistance not observed mammals, such as dogs humans. Therefore, exercise-dependent increase work breathing lower horse mammals. This airway patency appeared be mainly determined by pattern laryngeal movements. In fact, exercise, cross-sectional area, with video-endoscopic imaging technique level rima glottidis (CSArg), undergoes inspiration averaging up over 4 times expiratory values. Although linear correlation was found between CSArg minute ventilation (VE), activation contributes conductance only when narrower tracheal section. It appears therefore exercising pulmonary resistive features are finely controlled reduce supported muscles counterbalance ventilatory energetic requirements inherent remarkably enhanced performance species.