Pulse wave reflection: can it explain the differences between systemic and pulmonary pressure and flow waves? A study in dogs.

Abstract

SUMMARY. We have studied the effect of changes in pulse wave reflection on the configurations of pressure and flow in systemic and pulmonary circulation. Electromagnetic flow transducers, atrial catheters, and pacing leads were implanted in 10 dogs. In four animals, the flow transducer was placed on the pulmonary artery, in another four on the ascending aorta, and in two additional dogs on both vessels. One week later, ascending aortic and/or pulmonary artery flow and pressure (catheter tip manometer) were measured under general anesthesia (Nembutal, 30 mg/kg, iv). When the pulmonary circulation was studied (six dogs), measurements were made before and during serotonin infusion (0.5-0.75 mg/min). When the systemic circulation was studied (six dogs), measurements were made before and during nitroprusside infusion (50-200 jug/min). To quantify the arterial load, we calculated pulmonary and systemic input impedances. To estimate the amount of reflection, we used a reflection index which we defined as the amplitude ratio of reflected and forward wave. Nitroprusside decreased total peripheral resistance, increased total arterial compliance, and decreased the reflection index; similarity between aortic pressure and flow wave shapes increased, and they looked more like their pulmonary counterparts. Serotonin increased pulmonary vascular resistance, decreased pulmonary arterial compliance, and increased the reflection index. Resemblance of pressure and flow waves decreased. The differences in wave shapes can thus be explained by the amount of reflection: the less reflection the more pressure and flow resemble each other. (Circ Res 51: 479-485, 1982)

Input impedance of the pulmonary arterial system in normal man. Effects of respiration and comparison to systemic impedance.

“…6, June 1984 other dissimilarity is seen in the low frequency range, where the phase angles of the pulmonary impedance spectra are less than in the systemic tree. These results are consistent with less reflection in the pulmonary system (Van den Bos et al, 1982).…”

“…However, these investigators pointed out that loading effects of the external flow transducer may have affected the values of pulmonary characteristic impedance in their study. With serotonin infusion, Bergel and Milnor (1965) and Van den Bos et al (1982) reported no change in characteristic impedance. Bargainer (1967), using pulsewave velocity to calculate characteristic impedance, found an increase with serotonin infusion.…”

“…Input impedance of the systemic and pulmonary arterial systems has been shown to be sensitive to changes in those systems, either within a given subject under different physiological conditions (Murgo et al, 1981b), as a result of pharmacological interventions (Gundel et al, 1981;Van den Bos et al, 1982), or between groups of subjects under different physiological or pathological states (Nichols et al, 1977;Murgo et al, 1980). In recent years, the development of multisensor catheterizarion techniques (Murgo and Millar, 1972;Murgo, 1975) and the application of dedicated minicomputers for human hemodynamic research (Murgo et al, 1977) have greatly facilitated the calculation of input impedance in the clinical laboratory environment.…”

Age-Related Abnormalities in Arterial Compliance Identified by Pressure Pulse Contour Analysis

“…31,32 Pressure pulse waveform reflections arise primarily from discontinuities in the caliber or elastic properties along vessels in the arterial system, with the major reflection sites located close to the high-resistance arterioles. 33 The decline in the oscillatory compliance estimate was more closely associated with advancing age than a reduction in large artery compliance. Because the arterioles are largely free from atheroma and the change in oscillatory compliance was independent of blood pressure change in this population, this estimate may be a sensitive marker for the effects of the aging process per se independent of other confounding influences.…”

Echocardiography Can Identify Patients With Increased Pulmonary Vascular Resistance by Assessing Pressure Reflection in the Pulmonary Circulation

“…The shape of the pressure wave in the normal pulmonary circulation is similar to that of the flow wave. 3 From previous invasive studies in patients without increased PVR, we know that peak flow and peak pressure normally coincide, and there is no increase in pressure after peak flow. 4,5 On the other hand, in patients with pulmonary hypertension due to increased PVR, augmented pressure (AP) after peak flow due to an earlier and more pronounced pressure reflection has been observed.…”