Pulmonary artery thermodilution catheter

A pulmonary artery thermodilution catheter with a rapid-response thermistor is used to plot a thermodilution temperature curve simultaneously with an ECG trace and measured stroke volume. The plateau method originally used to calculate right ventricular ejection fraction from these traces was cumbersome and overestimated the value if it was less than 30 per cent. This method has been modified (D.h.a!D..ayt.„.§.£.,.al, 1987). The exponential portion of the downslope of the temperature curve begins when temperature has risen by 20 per cent from its nadir, and a computer algorithm yields a single first-order exponential curve to fit this washout curve. Three temperatures (T,, T2, and T3) are recorded at the first three R waves after this 20 per cent rise, and the mean of two residual fractions ( T2/T3 and T^T,) calculated. The right ventricular ejection fraction is then determined as 1 minus the mean residual fraction, and is little affected by mild tricuspid regurgitation. Commercial automated systems have been developed for this task. The right ventricular end-diastolic volume (RVEDV) and end-systolic volume (RVESV) can now be calculated since

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Sleep Apnea

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