Intrathoracis pressure measurement in horses during exercise: Validation of the wireless equivent 300 device

Abstract

Low-grade respiratory disease is a potential cause for reduced athletic performance. Increased intrathoracic pressure amplitude (IP) indicates impaired respiratory function but measurements at rest are insensitive diagnostics to abnormally elevated respiratory effort during exercise. A purpose-designed device (Equivent 300) for continuous telemetric measurement of IP during exercise was validated and reference ranges of exercising IP in warmblood horses were established. Twenty healthy Dutch warmblood mares underwent resting IP measurements using a standard method and the Equivent. With the device in place, horses underwent a standardized lunging exercise test (four minutes trot, four minutes canter, five minutes trot, five minutes walk) on four consecutive days. Heart rate and mean IP for each stage and ambient temperature and humidity for each session were recorded. All data were checked for normality and a mixed linear model was used to determine mean IP for each stage and the intraclass correlation coefficient (ICC) of IP for each stage with horse, SET stage, and session as explanatory variables. Reference values were calculated as mean IP±2SD. The device was well tolerated by the horses. There was no significant effect of session day; the ICC for ‘horses was 0.11 and the ICC for ‘stage’ was 0.77. Mean IP was 21.1±4.9 (ref 11.4-30.9), 33.9±7.9 (ref 18.2-49.7), 24.3±5.6 (ref 13.1-35.6) and 10.5±3.1 (ref 4.3-16.6) cm H2O for trot-1, canter, trot-2 and walk respectively. Reliable telemetric exercising IP measurement is possible but swallowing, coughing, head- and neck position, location of the esophageal balloon, G-force associated with locomotion were possible artefact-causing factors.