On continuous insufflation in fowls. A demonstration

Abstract

For many years this laboratory was interested in continuous insufflation which was carried out on mammals. At this meeting we wish to demonstrate apnœa produced by continuous insufflation in fowls. As you know, in these animals the bones are connected with the air sacs and the lungs. In this chicken, air is driven through both humeri and it escapes through a tracheal cannula. When the air is driven under sufficient pressure the respiratory movements are entirely abolished; the thorax stands still mostly in an exaggerated state of inspiration. This standstill may be sustained for two hours and longer. By this method the organism is liable to be washed out of its CO₂ content more thoroughly than by any other method of artificial respiration or forced respiration. Nevertheless, the animals appear to be in a good condition with no symptom which could be interpreted as “shock”. Furthermore, when the continuous insufflation is interrupted, one of the following conditions may follow, according to the duration of the standstill, the degree of pressure, and to the gas used. Either the inspiratory state may be converted at once into a continuous expiratory standstill (apnœa vera), lasting 20 to 50 seconds and gradually attaining the amplitude of the original respiratory oscillations; or the state of the inspiratory standstill continues, in a somewhat diminished degree, for many seconds before it is converted, abruptly or gradually, into an expiratory standstill. We shall mention briefly the facts that an admixture of ether to the insufflated air invariably prolongs the expiratory after-effect, and that an admixture of CO₂ (3 per cent.) prevents the standstill even during insufflation.

In fowls the expiration is normally of an active type and the expiratory standstill can only mean that after the interruption of the insufflation the expiratory muscles get temporarily into a state of strong tonic contraction.