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

UAO in Colombian Criollo horses significantly alters ventilatory mechanics and increases post-exercise lactate, indicating greater anaerobic demand.

This cross-sectional observational study investigated the effects of upper airway obstruction (UAO) on oxygen consumption (VO2), ventilatory variables, and exercise-induced pulmonary hemorrhage (EIPH) in 23 client-owned Colombian Criollo horses performing their natural gaits. Horses were assigned to control (n=11) or UAO (n=12) groups following overground endoscopy, and all underwent a standardized submaximal exercise test using an ergospirometry facemask. Recurrent laryngeal neuropathy was the most prevalent diagnosis (83%), followed by nasopharyngeal collapse (42%), with 6/12 UAO horses having multiple diagnoses. While mean VO2 and minute ventilation did not differ significantly between groups, UAO horses demonstrated meaningfully altered ventilatory mechanics, including reduced peak inspiratory (25.2 vs. 28.3 L/s) and expiratory (33.6 vs. 38.0 L/s) flow rates, and lower breathing frequency (76.0 vs. 89.2 breaths/min) due to prolonged inspiratory and expiratory durations. Notably, post-exercise blood lactate concentrations were significantly higher in UAO horses (6.8 vs. 3.5 mmol/L), suggesting greater anaerobic metabolic demand despite similar VO2 values. No evidence of EIPH was detected in either group via bronchoalveolar lavage cytology. The authors attribute the lack of VO2 and EIPH differences to the submaximal nature of the exercise protocol. These findings confirm that UAO produces measurable ventilatory compensation strategies and increased anaerobic effort in Colombian Criollo horses, with implications for performance and welfare assessment in this breed performing demanding natural gaits.

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