Effects of sedation and salbutamol administration on hyperpnoea and tidal breathing spirometry in healthy horses.
Authors: Raidal S L, Burnheim K, Evans D, Hughes K J
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary When assessing respiratory function in horses using spirometry, sedation becomes necessary for safety and compliance, yet the choice of sedative agent can substantially alter measured breathing parameters. Raidal and colleagues examined how acetylpromazine, xylazine, and their combination affected tidal breathing and induced hyperpnoea (via CO₂ rebreathing) in healthy horses using pneumotachographic spirometry. All sedative agents significantly reduced respiratory frequency, minute ventilation, and peak airflow during quiet breathing, with peak expiratory flow occurring later in the respiratory cycle; however, these effects were attenuated when horses were challenged with rebreathing-induced hyperpnoea, and acetylpromazine produced the least pronounced changes of the three options. Salbutamol administration increased peak inspiratory flow during tidal breathing in healthy animals, consistent with its bronchodilator properties. For practitioners and researchers conducting pulmonary function testing, these findings suggest that acetylpromazine is the preferred sedative to minimise artifactual changes in baseline respiratory mechanics, and incorporating CO₂-rebreathing protocols into the spirometry assessment may provide more meaningful physiological data by overriding drug-induced respiratory depression.
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Practical Takeaways
- •When performing pulmonary function testing in horses, use acetylpromazine as the preferred sedative if sedation is necessary, as it has the least impact on respiratory measurements during normal breathing
- •Incorporate induced hyperpnoea (rebreathing) protocols into spirometry procedures to obtain more reliable respiratory function data that better reflects the horse's true pulmonary capacity despite sedation effects
- •Salbutamol may improve inspiratory airflow in healthy horses, which could be relevant when assessing responses to bronchodilators during diagnostic pulmonary testing
Key Findings
- •Sedation with acetylpromazine, xylazine, or combination significantly reduced respiratory frequency, minute ventilation, and peak airflows during normal breathing
- •Peak expiratory airflow timing shifted later in the respiratory cycle under sedation compared to untreated horses
- •Carbon dioxide-induced hyperpnoea (rebreathing) attenuated the suppressant effects of sedation on pulmonary function indices
- •Salbutamol increased peak inspiratory flow during normal respiration in healthy horses; acetylpromazine showed least pronounced respiratory effects among sedatives tested