Circulatory effects of excitation of the respiratory tract

Abstract

The circulatory effects of the mechanical excitation of the trachea and the larynx have been studied comparatively in ex­ perimental investigations carried out on dogs.

In the tracheal excitation effect, three stages can be distinguished. First stage : immediately at the beginning of the ex­ citation, hypotension and bradycardia, preceding the first ex- piration of coughing in the majority of cases ; in some expe- riments the blood pressure increases from the very beginning. Second stage : an increase of arterial pressure from the firstexpiration of coughing, reaching the control level, and usually a level higher than before the excitation. Third stage : afterthe excitation has been withdrawn, during the last part of the seizure, a decrease in pressure is begun ; and once the seizure has been finished, the arterial pressure gradually returns to normal.

The intensity of the initial hypotension is not correlative to the type of the respiratory movement recorded at the same time, and therefore suggest that the mechanical influences has little importance, depending principally on the reflex effect.
Laringeal excitation produces a typical respiratory response that is respiratory inhibition vníƒth constrition of the glottis, and mechanically, this phenomenon is very different from coug­ hing. The simultaneous circulatory response is characteri- zed by hypotension and bradycardia stronger than in the first stage of the tracheal excitation and has been analyzed by ECG record

Both tracheal and laringeal hypotensive reflexes increase under conditions of central depression. This has been observed in some experiments after chlorpromazine.