Lobar Distribution of Pulmonary Circulation in the Supine and Erect Rat

¹ From the Department of Physiology, the Hebrew University-Hadassah Medical School and the Respiratory Research Laboratory, Department of Pulmonary Diseases, Hadassah University Hospital, Jerusalem, Israel

When the bronchial tree is blocked, gas trapped in the alveoli is resorbed by blood which continues to flow through the lungs until death of the animal. The speed of gas resportion is proportional to the amount of blood flowing through the area. When the proper gas mixture is inspired, survival time is sufficient to cause atelectasis in some parts of the lung. These are obviously the better perfused parts relative to volume. In supine rats atelectasis was encountered in the right upper lobe more often than in the right lower lobe and the difference is statistically significant (P < .001). In the erect position, the same results were obtained. This shows that the upper lobe is better perfused than the lower, regardless of posture. Discrepancy between work on man and dog—which indicate shifts in perfusion to the dependant parts of the lung on assumption of erect posture—and the present study is attributed to the small size of rats, in which changes in hydrostatic pressure differences between upper and lower lobes is necessarily small.

Note:
with the technical assistance of David Ben-Shahar