Oxygen consumption, locomotory-respiratory coupling and exercise-induced pulmonary hemorrhage in horses during the Paso Fino gait.

Abstract

BACKGROUND: Workload associated with the high frequency Colombian Paso Fino gait has not been evaluated. OBJECTIVES: To determine the oxygen consumption (V&#x307;O), heart rate (HR), stride frequency: breathing ratio, and hematology associated with the Paso Fino gait, including whether exercise-induced pulmonary hemorrhage (EIPH) occurs. ANIMALS: Eleven Paso Fino horses. METHODS: Prospective cohort study. Horses performed a standardized Paso Fino gait test across a wooden sounding board, simulating competition. V&#x307;Oand ventilatory parameters (tidal volume [V]; peak inspiratory and expiratory airflows [PkV&#x307;, PkV&#x307;]; respiratory rate [RR], minute ventilation [V&#x307;E]) were measured using a portable ergospirometry facemask. Heart rate was measured using electrocardiograms. Post-exercise lactate, hematocrit, bicarbonate, pH, electrolytes, and biochemistry concentrations were measured. EIPH was assessed via tracheobronchoscopy. Four horses completed a secondary high-intensity gallop to elicit peak V&#x307;Ofor comparative purposes. RESULTS: Median [IQR] mean individual HR during the Paso Fino gait was 190 [178, 201] bpm. Relative V&#x307;Omeasured 49.8 [48.4, 59.5] mL/(kg&#x2009;min; V&#x2009;=&#x2009;8.6 [8.0, 10.7] L; RR&#x2009;=&#x2009;87.1 [75.4, 99.5] bpm; V&#x307;E&#x2009;=&#x2009;869 [740, 902] L/min; PkV&#x307;&#x2009;=&#x2009;33.4 [32.7, 37.2] L/s; PkV&#x307;&#x2009;=&#x2009;44.2 [40.3, 46.0] L/s). Horses took 2.8 [2.7, 2.9] strides/second and had a stride frequency: breathing ratio of 2.0 [1.8, 2.3]. Post-exercise blood lactate concentration and hematocrit measured 2.7&#x2009;mmol/L and 50% respectively. Three horses showed endoscopic evidence of Grade-1 EIPH. The Paso Fino gait V&#x307;Oand HR equaled 79% V&#x307;Opk and 91% maximal HR, respectively, based on the high-intensity gallop. CONCLUSIONS AND CLINICAL IMPORTANCE: The Paso Fino gait represents submaximal exercise based on V&#x307;O&#x2009;<&#x2009;V&#x307;Opk and blood lactate.