SIMULTANEOUS LV AND RV VOLUMES BY CONDUCTANCE CATHETER - EFFECTS OF LUNG INSUFFLATION ON PARALLEL CONDUCTANCE

One aspect in the measurement of ventricular volume using the conducta nce catheter technique is the assessment of parallel electrical conduc tivity of structures extrinsic to the ventricular blood pool. Because it is sometimes necessary to make volume measurements during ventilati on or spontaneous respiration, the extent to which parallel conductanc e may vary with lung insufflation was investigated. Anesthetized pigs (11-15 kg) were ventilated and instrumented with both left (LV) and ri ght ventricular (RV) conductance and pressure-tip catheters and end-ho le catheters for injection of hypertonic saline into the inferior vena cava and pulmonary artery. Data were recorded during ventilation with tidal volumes of 10 and 20 ml/kg, and the associated fluctuations to LV and RV end-diastolic (EDV) and stroke (SV) volumes were measured. W ith the use of a saline dilution technique, parallel conductance (V-c) was determined for each ventricle with the ventilator off and lungs i nsufflated to 0, 10, and 20 ml/kg. Whereas ventilation caused marked o scillations in LV and RV EDV and SV, these variations could not be att ributed to V-c, which remained statistically unchanged from their base line values of 34.1 +/- 3.1 in the LV and 31.1 +/- 4.4 in the RV. Thes e results indicate that the fluctuations that occur in conductance cat heter-derived LV and RV volume signals with ventilation are not caused by any significant changes to parallel conductance.