Effects of sedation and salbutamol administration on hyperpnoea and tidal breathing spirometry in healthy horses.

This study investigates how sedation and the administration of a bronchodilator impact the lung function in healthy horses, both at rest and during simulated stressful conditions.

Study Background

• The research was conducted because sedation is often necessary when testing a horse’s lung function, but the effects of the drugs used can potentially affect the results of these tests.
• The researchers developed this study to understand the specific effects of sedation and the administration of a bronchodilator on a horse’s lung function.
• They examined these effects during normal breathing (eupnoeic respiration) and during heavy breathing provoked by increased carbon dioxide levels (rebreathing).
• To conduct these experiments, the researchers used a pneumotachographic spirometry system, which measures the amount and speed of air that is breathed in and out.

Results and Findings

• In the case of normal breathing, sedation with acetylpromazine (ACP), xylazine, or a combination of both was associated with considerable reductions in the breathing rate, the total amount of air exchanged in a minute, and the peak airflows.
• Peak expiratory airflows occurred later in the breathing cycle than it did in horses that were not sedated.
• The proportion of the expiration period during which peak flow occurs was also affected during normal breathing.
• However, these effects of sedation on lung function indices diminished under simulated stressful breathing conditions (rebreathing).

Implications and Recommendations

• The research suggests that future studies should take into account the fact that rebreathing reduces the effects of sedation.
• They might consider including stimulated heavy breathing as part of the protocol for measuring lung function in horses.
• Given that all sedative agents used in the study had some effect on normal breathing (but ACP had the least effect), ACP might be the preferred choice of sedative for horses during lung function tests.
• The bronchodilator salbutamol was found to increase the peak inspiratory flow during normal breathing in healthy horses. The implications of this result for the treatment of horses with respiratory disorders warrant further investigation.