Lafortuna Claudio L, Saibene Franco, Albertini Mariangela, Clement M Giovanna
Istituto di Bioimmagini e Fisiologia Molecolare del Consiglio Nazionale delle Ricerche, via Cervi 93 Segrate, 20090 Milan, Italy.
Eur J Appl Physiol. 2003 Oct;90(3-4):396-404. doi: 10.1007/s00421-003-0925-0. Epub 2003 Aug 14.
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 higher than that of other mammals of similar body mass. Under these circumstances an enormous mechanical burden is expected to impinge on the equine respiratory pump and regulatory mechanisms aiming to minimize this load may play an important role in determining the adequacy of the respiratory system to the metabolic requirements. The behaviour of the respiratory system has been investigated in horses at rest and during treadmill locomotion at different velocities and gaits. During exercise hyperpnoea, horses exhibit a significant reduction in the lung viscous resistance not observed in other mammals, such as dogs and humans. Therefore, the exercise-dependent increase in the rate of mechanical work of breathing is lower in the horse than in other mammals. This increase in the equine airway patency during exercise appeared to be mainly determined by the pattern of laryngeal movements. In fact, during exercise, the laryngeal cross-sectional area, determined with a video-endoscopic imaging technique at the level of rima glottidis (CSArg), undergoes during inspiration an increase averaging up to over 4 times the resting expiratory values. Although a significant linear correlation was found between CSArg and minute ventilation (VE), the laryngeal activation contributes to increase lung conductance only when CSArg is narrower than the tracheal section. It appears therefore that in exercising horses pulmonary resistive features are finely controlled to reduce the mechanical load supported by the respiratory muscles and to counterbalance the increase in the ventilatory energetic requirements inherent in the remarkably enhanced aerobic performance observed in this species.
马表现出卓越的有氧能力，在肌肉运动时达到的最大耗氧率比静息值高约30倍，比体重相似的其他哺乳动物高2.5倍。在这种情况下，预计巨大的机械负担会作用于马的呼吸泵，旨在最小化这种负荷的调节机制可能在决定呼吸系统对代谢需求的充足性方面发挥重要作用。已经对马在静息状态以及在跑步机上以不同速度和步态运动时的呼吸系统行为进行了研究。在运动性呼吸急促期间，马的肺粘性阻力显著降低，而在狗和人类等其他哺乳动物中未观察到这种情况。因此，马在运动时呼吸机械功速率的增加比其他哺乳动物要低。马在运动时气道通畅性的增加似乎主要由喉部运动模式决定。事实上，在运动期间，通过视频内镜成像技术在声门裂水平测定的喉部横截面积（CSArg）在吸气时平均增加到静息呼气值的4倍以上。尽管在CSArg与分钟通气量（VE）之间发现了显著的线性相关性，但仅当CSArg比气管横截面积窄时，喉部激活才有助于增加肺传导性。因此，在运动的马中，肺部阻力特征似乎受到精细控制，以减轻呼吸肌所承受的机械负荷，并抵消在该物种中观察到的显著增强的有氧能力所固有的通气能量需求的增加。
