Noninvasive, continuous evaluation of peripheral vascular resistance in humans

We sought a noninvasive alternative method of monitoring peripheral vascula r resistance continuously in humans, based on the analysis of arterial pres sure waveforms, Radial arterial pressure waveforms were recorded noninvasiv ely with a tonometer and analysed using a neural network method. To test th e accuracy of this method, the peripheral vascular resistance was also dete rmined by an invasive thermodilution method using a Swan-Ganz catheter in 2 0 subjects. To test the method in a clinical application, peripheral vascul ar resistance was determined by the noninvasive method before and after adm inistration of nifedipine in 6 patients with essential hypertension. Neural network analysis of waveforms reliably yielded values between 0.00 and 1.0 0. Peripheral vascular resistance :determined by neural network analysis an d according to the invasive method showed a significant (p < 0.005) positiv e linear correlation. The peripheral vascular resistance measured by neural network analysis showed a significant (p < 0.05) decrease 30 min after adm inistration of nifedipine, paralleling a decrease in blood pressure, Neural network analysis of tonometric radial artery waveforms provides an accurat e, noninvasive, and continuous index of peripheral vascular resistance in h uman subjects. This simple method should permit more extensive homodynamic studies and larger epidemiological surveys in contrast to those undertaken using invasive techniques.