Compensatory mechanisms in rats with nasal obstructions.

This study, in rats was designed to demonstrate the changes in respiratory dynamics in compensation for nasal obstructions. The experiment was performed on 30 rats. Fifteen rats served as the study group while another 10 rats served as controls. Five of the 30 rats were operated on to find out whether they would live and if so, for how long. Mouth breathing caused acute respiratory acidosis and marked aerophagia, leading to spontaneous death of the five experimental animals 90 to 100 hours postoperatively. Stenosis of the oropharyngeal airway due to palatal-epiglottic approximation, is supposed to be responsible for the respiratory insufficiency in nasally-obstructed rats. The compensatory changes in respiratory mechanics caused by high oropharyngeal airway resistance, together with some possible reflex changes, may have caused air swallowing. It is supposed that the increased air volume in the stomach and guts, causing elevation of the diaphragm and a paralytic ileus, contributed to mortality. No signs of aspiration were observed in these animals. After the surgical obstruction of both nostrils, changes in acid-base balance occurred in the 15 study rats 24, 48, and 72 hours postoperatively. On the first, second, and third days, a decrease in pO2 and pH, an increase in pCO2, and a compensatory increase in serum bicarbonate was observed.