Characteristics of blood flow velocity in the hypertensive canine pulmonary artery

Pulmonary blood velocity patterns in lamb models of pulmonary vascular impairment

“…Careful quantification of the maximum velocity of regurgitant flow behind the pulmonary valve has been shown to correlate well with the pressure gradient across the valve and with mean pulmonary artery pressure [1]. In short-term studies in dogs, in which each animal served as its own control, we found that (1) acute pulmonary hypertension created by hypoxia (10% O2 inhalation) increased the magnitude and dura~ tion of flow reversal along the posterior wall while decreasing the duration of flow reversal along the anterior wall [20], and (2) acute pulmonary hypertension created by embolization with polystyrene microspheres decreased the ratio of forward/reverse flow times by at least 50% when measured at a midvessel position [22].…”

“…Studies differed with respect to where the sample volume was placed (in a central position in the main pulmonary artery or in the right ventricular outflow tract), the techniques used to correct for heart rate dependencies (no correction or division by total cycle time, right ventricular ejection time, or a predicted heartrate- tract were reported to be more reliable [14]. Clinical studies as well as studies performed in our laboratory show that the pulmonary blood velocity profile can be highly irregular and that rise times near the walls, particularly the posterior wall, may be significantly shorter than those observed at the center of the vessel [14][15][16][17][18][19][20]. Thus the difficulty in obtaining good results from velocity waveforms in the main pulmonary artery may be influenced by the difficulty of positioning the sample volume in the center of the vessel using twodimensional echocardiographic techniques.…”

“…Pulmonary artery pressure and left atrial pressure were measured with Millar Mikro-tip and Statham P23Db pressure transducers, respectively; cardiac output was measured periodically by positioning an electromagnetic flow probe around the ascending aorta. A pulsed Doppler ultrasound velocity probe consisting of a 1-mm 2 piezoelectric crystal mounted on styrofoam backing embedded in epoxy at the tip of an 18-gauge needle [20] was introduced into the anterior wall of the main pulmonary artery 2cm above the valve annulus and advanced to the posterior wall position. The crystal was activated with a 20-MHz pulsed Doppler unit equipped with a hardware-implemented zero-crosser [26].…”

“…Though studies examining the effects of acutely altered pulmonary hemodynamics on velocity patterns in animals have been published [17,[19][20][21][22], little work has been reported using animal models with chronically altered hemodynamics. Thus, the goals of this study were twofold: (1) to demonstrate the successful development of animal models that mimic a broad spectrum of relevant pulmonary hemodynamics in infants and children with compromised pulmonary circulations, and (2) to use the models to explore relationships between selected pulmonary blood velocity waveform-shape parameters and pulmonary vascular conditions.…”

“…(1) irregularity in pulmonary velocity profiles such that indices vary depending on the position of the sampling site in the main pulmonary artery or the right ventricular outftow tract [14][15][16][17][18][19][20], and (2) disagreement as to whether and how to correct for variations in heart rate [1,[7][8][9][10][11][12][13][14]. Though studies examining the effects of acutely altered pulmonary hemodynamics on velocity patterns in animals have been published [17,[19][20][21][22], little work has been reported using animal models with chronically altered hemodynamics.…”