Evaluation of infrared thermography and 6-minute walk tests to assess airflow limitation, impaired thermoregulation, and exercise intolerance in dogs with brachycephalic obstructive airway syndrome

Abstract

Brachycephalic obstructive airway syndrome (BOAS) is associated with significant morbidity and mortality. Routine clinical evaluation fails to detect physiologic consequences of BOAS including airflow limitation, exercise intolerance, and impaired thermoregulation. A six-minute walk test (6MWT) with infrared thermography (IRT) may aid detection and clinical management by assessing the physiologic consequences of BOAS. IRT has been used in dogs to assess thermoregulation and in people with obstructive sleep apnea. Our objectives were to compare 6MWT and IRT parameters between healthy mesaticephalic (Mesa) and brachycephalic (Brachy) dogs, and dogs with BOAS. 6MWT parameters include normalized distance walked (ND), rectal temperature, pulse, respiratory rate, and pulse oximetry (SPO2). Mean (Tmean) and maximum (Tmax) IRT temperatures at 3 regions of interest (ROI) were evaluated. Evaluation timepoints were pre-6MWT, immediately post-6MWT (T0) and 5 (T5) and 15min post-6MWT (T15). No significant difference in ND, SPO2, or temperature were found between groups (p>.05). BOAS dogs had higher dorsal and rostral Tmax and Tmean temperatures compared to Mesa dogs at all timepoints (p < .05). BOAS dogs had higher Tmean temperatures compared to Brachy dogs at baseline and T15 and T5 and T15 for dorsal and rostral ROIs respectively (p < .001). ROC analysis showed significant discrimination between BOAS and non-BOAS (Brachy and Mesa) dogs with areas under the curve between 0.79-0.96. Significant moderate correlations were found between IRT temperatures, ND and rectal temperature. This pilot study demonstrates the potential in pairing the 6MWT and IRT with evaluation of clinical signs as screening tool to identify dogs with BOAS.