1961 Volume 14 Issue 2 Pages 41-44
Physiological respiration in animals is carried out by the increase and decrease of negative pressure in the thoracic cavity. This fact has been made clear by a number of research workers. The author confirmed it also in the dog. The present experiment was conducted as a basic one for the performance of artificial respiration under pressure at the time of thoracotomy in animals. A re-lationship between artificial intrapulmonic pressure and morphological changes of the lung was investigated in lungs in situ and excised ones of the dog, goat, cow, and horse. Interrelationships were studied among intrapulmonic pressure, amounts of naturally and artificially inhaled air, and body weight.
Besides, pulmonary tissue under pressure was examined histologically in goats and cattle. The results obtained are summarized as follows.
1. The pulmonary weight was 1.0 to 1.5 per cent in every animal species.
2. Intrapulmonic pressure had a definite relationship to the amounts of naturally and artificially inhaled air and body weight. The higher intrapulmonic pressure, the larger becomes the inspiratory volume of air.
3. A larger artificial inspiratory volume of air was required for the excised lung than for that left in the thoracic cavity until the same intrapulmonic pressure was reached.
4. In dogs and goats lying on the right side with the left half of the thoracic cavity open, the lung was swollen moderately when the intrapulmonic pressure was in a range of 3.0 to 3.7 mmHg (unit omitted hereinafter), showed a typical form when the pressure was 8.0 to 15.0, and protruded partly from the opening of the excised thoracic cavity when the pressure was higher than 15.0.
5. The state of the lung was observed on horses and- cattle kept in the same position as mentioned in the preceding paragraph. The lung was swollen moderately in horses and cattle when the intrapulmonic pressure was in a range of 15 to 20 and in a range of 19 to 23, respectively. It adhered closely to the opening of the excision of the thorax when the pressure was 19.0 in horses and 22.9 in cattle. It protruded outside of the excised opening of the thorax when the pressure reached 20.0 in horses and 25.0 in cattle. When the lung was swollen moderately and when it adhered closely to the excised opening of the thorax, the artificialley inhaled air had amounted to 3 to 6 liters in horses and 6.0 to 7.4 liters in cattle.
6. Histological examination was carried out on lungs of goats and cattle swollen with artificially inhaled air. Congestion of alveolar blood vessels and splitting of pulmonary elastic fibers were observed and, in the case of cattle, dilatation of terminal bronchioli was obvious.
7. The experimental results indicate that when thoracotomy is performed, artificial respiration should be carried out so that intrapulmonic pressure might be 8 to 13 mmHg in goats and 20 to 23 mmHg in cattle. When the artificial inspiratory volume of air is so adjusted as to be in a range of 4 to 6 liters in cattle, the lung is to be swollen moderately and no alveolar walls will be broken.
This seems to indicate a limit of artificial pressure inside the lung.