ARTERIAL BLOOD-GAS TENSION AND ACID-BASE-BALANCE DURING EXERCISE IN HORSES WITH PHARYNGEAL LYMPHOID HYPERPLASIA

Arterial blood gas and acid-base values during maximal exercise over a 1.2 km distance were recorded in 4 thoroughbred horses before and after the chemical induction of pharyngeal lymphoid hyperplasia (PLH). Samples were collected after galloping 0.8 km and 1.2 km, immediately upon stopping and 5 min after exercising. In only 1 horse was any difference noted in the pre and post PLH induction results. The horse was more hypercapnoeic at the 1.2 km mark and also took much longer to complete the gallop when it had PLH. It also had signs of lower respiratory disease. In the other horses, the only changes which could be attributed to PLH were seen immediately upon stopping. It seems that PLH does not inhibit gas exchange during exercise unless the lesions are extremely severe.