Lobeline-induced hyperpnea in equids. Comparison with rebreathing bag and exercise

In order to facilitate lung auscultation, a transitory hyperpnea may be obtained by lobeline administration, use of a rebreathing bag or exercise. The effect of these three methods on the pulmonary function were studied and compared in 5 healthy ponies. Respiratory airflow and tidal volume were measured with a pneumotachograph Nr. 5 and pleural pressure with the esophageal balloon catheter technique. Pulmonary function values were measured before, during and after the hyperpnea induced by (i) lobeline, (ii) rebreathing and (iii) exercise. Lobeline administration induced an hyperpnea due to both an increase in tidal volume and respiratory rate; this increase in ventilation lasted for about 90 s and was accompanied by a sharp rise in the respiratory peak airflows, especially the expiratory ones. The rebreathing method induced a less hyperpnea which lasted only 30 s. Lastly the hyperpnea after a light treadmill exercise was the longer in duration and intermediate between the preceding methods in intensity.