Diaphragmatic blood flow at various levels of ventilation in the rabbit.

Diaphragmatic and renal blood flow were measured with Ytterbium-169 and Scandium 46 labelled 15 micron microspheres in sodium pentobarbitone anesthetized rabbits. The first measurement was performed during spontaneous breathing of air and the second measurement after 15 min of breathing 2-6% carbon dioxide in oxygen. The lung ventilation as well as the diaphragmatic blood flow increased significantly during breathing of the carbon dioxide-oxygen mixture. Arterial blood pressure and renal blood flow were not significantly altered by the induced hyperventilation. No significant correlation was found between the magnitude of lung ventilation and diaphragmatic blood flow. The results of the present study indicate that consecutive measurements of diaphragmatic blood flow with radioactive microspheres at various levels of breathing effort is an appropriate method for further exploration of the relationship between diaphragmatic perfusion and working performance.