Pleural pressure in relation to variations in variations in bronchial calibre and lung elasticity

Abstract

In a former paper the authors showed that in the graphics which by current methods register the bronchial tone through resistance to insufflation, there may appear modifications which logically must not be interpreted as changes in the bronchial caliber, but might be due-to changes in the pulmonary elasticity. In the present paper they propose and put into practice in dogs with artificial respiration, the register of pleural pressure and of the volume of expired air, simultaneously with the register of resistance to insufflation, according’ to the method of Konzett and Rossler. The' substances utilized to bring about bronchomotor and circulatory chances are histamine, acetyl-choline and adrenaline.

From the results the authors infer that pleural pressure is modified by the variations in the bronchial caliber, although the former may also be influenced by changes in the elasticity of the pulmonary parenchyma. However the influence of these changes, compared with those of the bronchial caliber, is not exercised in the same sense on acting upon the pleural pressure and upon the resistance to insufflation. An increase of resistance to insufflation in the current methods of registering the bronchial tone may be interpreted as due to a tightening of the bronchial opening, when the former is accompanied by a diminution of pleural pressure and of the volume of expired air. When the said increase of resistance is due to a supposed disminution of pulmonary clasticity, it is also accompanied by a diminution of expired air, but the pleural pressure increases instead of diminishing.

By means of the simultaneous register of pleural pressure and expired air, it is possible to recognize and exclude, not only the influences of supposed pulmonary elasticity variations, but also those of extra-pulmonary origin, which might be produced in the bronchial tone register in closed thorax by eventual spontaneous contractions of the respiratory muscles. An increase of resistance to insufflation due to the latter, would manifest itself by an increase of pleural pressure but also of expired air. The last named does not augment, but rather diminishes when the increase of insufflation resistance is due to a bronchial tightening or to a diminution of pulmonary elasticity.

The system utilized by the authors for the registering of the variations of expired air volume is described. For the registering of pleural pressure, the closed thorax is punctured with a current pneuma-thorax canule which is in communication with a Marey register capsule. By deep anaesthesia, or sometimes by the use of curare, the possibility of any variations in the pleural pressure through spontaneous contractions of the respiratory muscles is excluded in the majority of experiments.

In some experiments the pressure in the pulmonary artery and in the left auricule is also registered. The changes observed in pulmonary circulation caused by the injection of the substances utilized, specially by adenaline, are very remarkable and susceptible to various interpretations. However this presents a problem which several investigators have studied with contradictory results and interpretations. This problem is not the object of the present paper, but the authors announce further investigations on same.

They also propose another investigation problem, suggesting that the changes in the repletion of pulmonary vessels may produce modifications in the elasticity of the pulmonary parenchyma. The latter not precisely in the sense currently accepted in clinic on referring to pulmonary extasis of patients with heart disease, as a state of greater rigidity, on the contrary, the authors suggest that the greater the repletion of pulmonary vessels, the more pronounced is the effective elastic retraction during expiration. They announce further investigations on this subject.