The pulsatile component of left atrial pressure has little effect on pulmonary artery impedance estimation in normal rats

Figures

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  Figure 1. (A) Schemes for one‐input, one‐output (I1O1) analysis and two‐input, one‐output (I2O1) analysis. In the I1O1 analysis, pulmonary artery impedance (PAZ) is calculated as the reciprocal of hydraulic admittance from pulmonary artery (PA) pressure to PA flow [Y 1(f)]. In the I2O1 analysis, hydraulic admittance from PA pressure to PA flow [Y 2X(f)] and that from left atrial (LA) pressure to PA flow [Y 2U(f)] are calculated, and PAZ is determined by the reciprocal of Y 2X(f). (B) A schema for an elastic lossless tube with three‐element Windkessel model. The model is characterized by peripheral resistance (RP), pulmonary arterial compliance (CP), characteristic impedance (ZC), and transmission time from an inlet of PA to a reflection site in pulmonary vascular bed (TD).

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  Figure 2. (A) Averaged power spectra of pulmonary artery (PA) flow, PA pressure, left atrial (LA) pressure. (B) Averaged modulus and phase of a transfer function from PA pressure to LA pressure, and coherence function. Solid lines denote averaged data, and dotted lines denote mean ± standard error.

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  Figure 3. (A) Averaged modulus and phase of pulmonary artery impedance (PAZ) estimated by one‐input, one‐output (I1O1) analysis [Z1(f)], and coherence function. (B) Averaged modulus and phase of PAZ estimated by two‐input, one‐output (I2O1) analysis [Z2(f)], and partial coherence function (left panels). Averaged modulus and phase of the reciprocal of hydraulic admittance from LA pressure to PA flow [Y 2U(f)], and partial coherence function (right panels). Multiple coherence function between the combination of two inputs (PA and LA pressure) and one output (PA flow) is demonstrated in the bottom panel. Solid lines denote averaged data, and dotted lines denote mean ± standard error. Red dotted lines denote a tube and three‐element Windkessel model fitted to averaged modulus and phase of PAZ estimated by I1O1 or I2O2 analyses.

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  Figure 4. (A) Averaged data showing the difference between pulmonary artery impedance (PAZ) estimated by one‐input, one‐output analysis (I1O1) and PAZ estimated by two‐input, one‐output analysis (I2O1). Difference in modulus was calculated as the difference from the PAZ modulus by I1O1 analysis expressed in the common logarithm to that by I2O1 analysis. Difference in phase is the difference of the PAZ phase by I1O1 analysis from that by I2O1 analysis. Solid lines denote averaged data, and dotted lines denote mean ± standard error. (B) Correlation of modulus (left panel; expressed in common logarithm) and phase (right panel) of PAZ estimated by I1O1 analysis [Z1(f)] with those estimated by I2O1 analysis [Z2(f)]. Coefficients of determination are demonstrated in each panel.

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  Figure A1. Averaged data of modulus and phase of pulmonary artery impedance estimated directly as a transfer function from PA flow to PA pressure [ZDirect(f)] and the data calculated as the reciprocal of hydraulic admittance from PA pressure to PA flow [Z1(f)], and the corresponding coherence functions. Solid lines denote averaged data, and dotted lines denote mean ± standard error. (A) In the upper panels, data are plotted on a logarithmic scale in the abscissa. (B) In the lower panels, data shown in the upper panels are duplicated on a linear scale in the abscissa to better illustrate the differences in the high frequency range.