Pulmonary circulation time: comparison of mean, median, peak, and onset (appearance) values using indocyanine green and first-transit radionuclide techniques.

To assess the difference between a variety of mathematical methods for assessing pulmonary transit time, we evaluated 11 acutely anesthetized and instrumented mongrel dogs at a control stage and then during infusions of isoproterenol or phenylephrine, or after the induction of ischemia. Green-dye optical density curves were obtained to evaluate a variety of pulmonary circulation times. Mean transit time, median time, peak time, and onset time all correlated well (r greater than or equal to 0.93), with the mean time being the longest, followed by the median time (4% less than the mean time, p less than 0.05), peak time (15% less than the mean time p less than 0.01), and onset or appearance time (49% less than the mean time, p less than 0.001). In the 34 available data points the mean time averaged 4.67 +/- 1.7 seconds, the median time averaged 4.47 +/- 1.74 seconds, the peak time averaged 3.98 +/- 1.7 seconds, and the onset time averaged 2.27 +/- 1.43 seconds. Similar results were obtained from the first-pass radionuclide angiograms from 17 adult male subjects. We conclude that median, peak, and onset times are reasonable though predictably shorter approximates of mean pulmonary transit time. They may be utilized during interventions (particularly when alternative counting methods are planned, as with radionuclide or possibly digital angiographic techniques) as guides to changes in the pulmonary circulation.