EFFECTS OF AIRWAY-OBSTRUCTION ON TRANSMURAL PULMONARY-ARTERY PRESSUREIN EXERCISING HORSES

Objective-To determine whether laryngeal hemiplegia would increase tra nsmural pulmonary artery pressure (TPAP). Animals-6 horses. Design-Hor ses were studied under 5 conditions: control conditions, after inducti on of left laryngeal hemiplegia, during obstruction of the left nostri l, after placement of an instrumented tracheostomy, and after placemen t of an open tracheostomy. Horses were evaluated after being given sal ine solution and after being given furosemide. Procedures-Horses were exercised on a high speed treadmill, using a maximum speed of 13 m/s. During each exercise, airway pressures, airflow, esophageal and pulmon ary artery pressures, and blood gas partial pressures were measured. R esults-When adjusted for horse, speed, and obstruction condition, mean TPAP (pulmonary artery pressure - esophageal pressure) and minimum TP AP were significantly lower after administration of furosemide than af ter administration of saline solution. in horses given saline solution , respiratory obstruction that increased intrapleural pressure signifi cantly increased mean TPAP, and respiratory obstruction that decreased intrapleural pressure significantly decreased minimum TPAP. Conclusio ns-Changes in intrapleural pressure appear to play an important role i n pulmonary artery pressure and TPAP. Clinical Relevance-Because induc tion of laryngeal hemiplegia did not increase TPAP, laryngeal hemipleg ia is unlikely to contribute to development of exercise-induced pulmon ary hemorrhage.