Negative wave reflections in pulmonary arteries.
The pulmonary arterial branching pattern suggests that the early systolic forward-going compression wave (FCW) might be reflected as a backward-going expansion wave (BEW). Accordingly, in 11 open-chest anesthetized dogs we measured proximal pulmonary arterial pressure and flow (velocity) and evaluated wave reflection using wave-intensity analysis under low-volume, high-volume, high-volume + 20 cmH2O positive end-expiratory pressure (PEEP), and hypoxic conditions. We defined the reflection coefficient R as the ratio of the energy of the reflected wave (BEW [-]; backward-going compression wave, BCW [+]) to that of the incident wave (FCW [+]). We found that R = -0.07 +/- 0.02 under low-volume conditions, which increased in absolute magnitude to -0.20 +/- 0.04 (P < 0.01) under high-volume conditions. The addition of PEEP increased R further to -0.26 +/- 0.02 (P < 0.01). All of these BEWs were reflected from a site ~3 cm downstream. During hypoxia, the BEW was maintained and a BCW appeared (R = +0.09 +/- 0.03) from a closed-end site ~9 cm downstream. The normal pulmonary arterial circulation in the open-chest dog is characterized by negative wave reflection tending to facilitate right ventricular ejection; this reflection increases with increasing blood volume and PEEP.
Hollander
E H
EH
Departments of Medicine and Physiology and Biophysics, Cardiovascular Research Group, University of Calgary, Calgary, Alberta, Canada, T2N 4N1.
Wang
J J
JJ
Dobson
G M
GM
Parker
K H
KH
Tyberg
J V
JV
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D004285:Dogs; D011651:Pulmonary Artery / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology