Noninvasive cardiopulmonary monitoring.

Contrast dilution curves have been utilized for evaluation of hemodynamic function. Noninvasive techniques for this purpose usually have been qualitative, expensive, and cumbersome with minimal applicability to the newborn infant. The technique of roentgen densitometry has been utilized to screen children with heart murmurs. Characteristic curve patterns were identified for normal subjects and for patients with shunts with correlation to catheterization data. This technique is now being applied in a quantitative fashion to estimate cardiac output and left-to-right ductal shunts. Cardiac output volumes were inversely proportional to the difference of the second moments of the dilution curves obtained--the second moment being a measurement of the peak dispersion. The estimation of the percent of left-to-right shunt is related to the exponential decay of the left-sided curve.