The effects of upper airway obstruction on oxygen consumption and ventilatory variables in Colombian criollo horses.

backgroundWhile conditions associated with upper airway obstruction (UAO) are reported in Colombian Criollo horses, their effect on ventilation and performance is unknown. HYPOTHESIS/

objectivesTo investigate how oxygen consumption ($\dot{\rm V}$O2), ventilation,, and exercise-induced pulmonary hemorrhage (EIPH) are affected by UAO in horses performing at natural gaits. ANIMALS: Twenty-three client-owned Colombian Criollo horses.

methodsA cross-sectional observational study assigned horses to a control (C), or UAO group after overground endoscopy. All horses performed a standardized submaximal exercise test while wearing an ergospirometry facemask. Post-exercise blood lactate concentration and bronchoalveolar lavage cytological results were assessed.

resultsTwelve horses had UAO, with 6/12 having multiple diagnoses. Recurrent laryngeal neuropathy was most prevalent (83%), followed by nasopharyngeal collapse (42%). Mean $\dot{\rm V}$O2 and minute ventilation were not different between C (79.4 ± 22.0 mL/(kg min); 723 ± 203 L/min) and UAO (88.2 ± 23.2 mL/(kg min); 648 ± 190 L/min). UAO resulted in lower peak inspiratory (25.2 ± 5.3 L/s, P = .01) and expiratory (33.6 ± 7.3 L/s, P = .03) flow than C (28.3 ± 10.0 and 38.0 ± 9.0 L/s). Longer inspiratory and expiratory durations in UAO resulted in lower breathing frequency (76.0 ± 16.0 vs. 89.2 ± 12.4 breaths/min). Post-exercise [lactate] was greater (P = .05) in UAO (6.8 [4.6-9.3] mmol/L) than C (3.5 [3.0-5.5] mmol/L). No evidence of EIPH was noted. CONCLUSIONS AND CLINICAL IMPORTANCE: Horses with UOA had marked changes in ventilation, however, $\dot{\rm V}$O2 and EIPH severity were not different to C, likely because the exercise was submaximal.