The continuous monitoring of CO2 ductances in pulmonary intensive care

Abstract

A cardiorespiratory monitoring system allows the measurement of {Mathematical expression} and {Mathematical expression} in the expired air of the patient at the mouth (endtidal CO2) and in a mixing box. From these parameters, combined with the measured {Mathematical expression}, the alveoloexpired {Mathematical expression} and alveolararterial {Mathematical expression} ductances which assimilate the respiratory system to a two-stage exchanger have brought about a lot of valuable information: 1. DuA improves by 20% in 20 patients after removal of bronchial obstruction (p<0.001) and by 9% in 7 intubated patients after tracheotomy (p<0.02). DuA falls by 15% (p<0.001) in 10 patients with hypocapnia ( {Mathematical expression} = 28 mmHg) after a dead space adjunction with the aim of normalizing {Mathematical expression}( {Mathematical expression} = 35 mmHg). 2. Dua falls by 33% in six patients after pulmonary embolism, proved by angiography (p<0.001) and by 9% in 34 patients after 30 min of pure oxygen breathing (p<0.001). On the other hand, in the absence of clinical or radiological pulmonary edema, it increases by 19% in 38 patients with hypervolemia after diuresis (furosemide) (p<0.001). Thus since {Mathematical expression} varies with anatomical dead space and the air distribution disorder, {Mathematical expression} evolves according to the disorders of the blood distribution and arterial-alveolar diffusion. The determination of these coefficients, in the absence of significant changes in the arterial blood gases, helps the diagnosis, guides the early treatment and allows for the monitoring of its efficiency. © 1980 Springer-Verlag.