Pulmonary capillary blood flow during cardiac catheterization

¹ Department of Physiology, Graduate School of Medicine, University of Pennsylvania; and Heart Station, Philadelphia General Hospital, Philadelphia, Pennsylvania

Methods for the measurement of mean and instantaneous pulmonary capillary blood flow by means of a horizontal body plethysmograph have been described. Methods of calibration were described for the determination of the rate with which N₂O was taken up by the blood from the recorded plethysmographic pressure. They included a correction factor for leaks, and for changes from mainly adiabatic to more isothermal conditions. Duplicate determinations with the plethysmographic N₂O uptake method of mean pulmonary capillary blood flow showed a good reproducibility and comparison with the direct Fick method during cardiac catheterization on six patients did not show any statistically significant difference. Examples illustrating the use of the method for comparison between the pulmonary vascular pressure gradient and the pulmonary capillary pulse flow curves are presented.