Evaluation of neurogenic and metabolic influences from a perfused leg on respiratory exchanges

Abstract

Paired mongrel dogs of near equal weight were used in two separate series of perfusion experiments. In the first series, the amputated leg of the ‘perfused’ dog remained connected to the rest of the body by the femur and the femoral nerve. The arterial and venous femoral vessels were anastomosed to the corresponding vessels in the ‘donor’ dog. Three milligrams per kilogram of 2–4-dinitrophenol was injected intravenously into the donor dog which was now perfusing the amputated extremity. The expired air was collected, analyzed and subjected to statistical analysis. It was found that the minute volume, oxygen consumption and carbon dioxide production exhibited an increase of approximately 100% above control values in the donor dogs. The perfused animals in this series also exhibited marked increases in the same parameters. It was discovered that dinitrophenol was reaching the perfused animal via the blood supply of the intact femur. Therefore, a second series of experiments was undertaken in which the femur was also amputated leaving the nerves as the sole connection to the body of the animal. The donor dogs again exhibited the expected elevation in ventilatory function, but the perfused animals demonstrated no changes. In both series, severing the nerves did not alter the ventilatory response. The data suggest that increased metabolism per se does not stimulate pulmonary ventilation via neural pathways.