Pulmonary arterial compliance in dogs and pigs: the three-element windkessel model revisited.
In six dogs and six weight-matched miniature pigs at baseline and after pulmonary embolization, pulmonary arterial compliance was determined using the pulse pressure method (C(PPM)), the three-element windkessel model (C(WK-3)), and the ratio of stroke volume to pulse pressure (SV/PP). C(PPM) was lower in pigs than in dogs at baseline (0.72 +/- 0.23 vs. 1.14 +/- 0.29 ml/mmHg, P < 0.05) and after embolism (0.37 +/- 0.14 vs. 0.54 +/- 0.16 ml/mmHg, P = 0. 07) at matched flow, but not at matched flow and pressure. C(PPM) showed the expected inverse relation with pressure and a direct relation with flow. C(WK-3) was closely correlated with C(PPM), except for all dogs at baseline where C(WK-3) was up to 100% higher than C(PPM). Excluding these data, regression analysis yielded C(WK-3) = -0.01 + 1.30. C(PPM) (r(2) = 0.97). C(WK-3) was found to be unreliable when input impedance first harmonic modulus was close to characteristic impedance, i.e., when reflections were small. SV/PP correlated well with C(PPM) (SV/PP = -0.10 + 1.76. C(PPM), r(2) = 0.89). We conclude that 1) C(PPM) is a consistent estimate of pulmonary arterial compliance in pigs and dogs, 2) C(WK-3) and SV/PP overestimate compliance, and 3) C(WK-3) is unreliable when wave reflections are small.
Segers
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P
Hydraulics Laboratory, Institute for Biomedical Technology, University of Gent, B-9000 Ghent, Belgium. patrick.segers@rug.ac.be
Brimioulle
S
S
Stergiopulos
N
N
Westerhof
N
N
Naeije
R
R
Maggiorini
M
M
Verdonck
P
P
D000818:Animals; D003187:Compliance; D004285:Dogs; D006439:Hemodynamics; D008955:Models, Cardiovascular; D011312:Pressure; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology; D011674:Pulse; D013318:Stroke Volume; D013552:Swine; D014655:Vascular Resistance / Q000502:physiology