Monthly, daily, and circadian variations of measurements of pulmonary mechanics in horses with chronic obstructive pulmonary disease
Jean, D.; Vrins, A.; Lavoie, J.P.
American Journal of Veterinary Research 60(11): 1341-1346
1999
ISSN/ISBN: 0002-9645 PMID: 10566805 Document Number: 503728
Temporal variations of pulmonary function were determined in 5 horses without respiratory tract disease (controls) and 7 horses with chronic obstructive pulmonary disease (COPD). Pulmonary function testing was performed monthly during 3 consecutive months, daily for 5 consecutive days, and at 6-h intervals for 24 h before and after administration of atropine (0.02 mg/kg body weight, i.v.) and after 5 consecutive months at pasture. Respiratory rate, tidal volume (VT), minute ventilation (VE), maximum change in trans-pulmonary pressure ( Delta PL), pulmonary resistance (RL) and pulmonary elastance (EL) were calculated. COPD-affected horses had a significantly higher expiratory to inspiratory time ratio (TE/TI) and Delta PL, EL and RL than horses without respiratory diseases during all periods and higher VE during monthly and daily evaluations. Daily variation in VT and monthly and circadian variation in EL were significant in COPD-affected horses. In control horses, significant changes were apparent only in TE/TI during daily recordings. In COPD-affected horses, reduction in Delta PL, RL and EL was significant after atropine administration and after maintenance on pasture. Despite variations in measurements of respiratory mechanics in both groups of horses, values remained significantly different between groups over time. It is concluded that despite individual variation, measurements were repeatable during short and long periods. Response to administration of atropine to COPD-affected horses underestimated improvement in respiratory tract function that resulted from maintenance on pasture.