Feasibility and accuracy of Doppler echocardiographic estimation of pulmonary artery occlusive pressure in the intensive care unit

Abstract

Mitral inflow and pulmonary vein inflow variables have been shown to relate to left ventricular filling pressures. However, the feasibility and accuracy of Doppler estimation of pulmonary artery (PA) occlusive pressure in the intensive care unit have not been previously assessed. Accordingly, 67 consecutive patients in intensive care units who had PA catheters underwent Doppler recordings of mitral inflow, pulmonary vein flow, and isovolumic relaxation time (IVRT). Thirty-six patients met Doppler inclusion criteria. Most exclusions were due to atrial fibrillation, merging of peak velocity during early diastole (E) and atrial contraction (A) mitral flow velocities, and inadequate recordings. Mean age (±SD) was 65 ± 12 years, ejection fraction varied between 19% and 80%, and 45% of patients were on mechanical ventilation. Doppler-derived variables were related to occlusive pressure (mean 16 ± 6 mm Hg, range 6 to 40), and the most significant variables were entered into a multiple linear regression analysis. The derived relation was tested in 30 repeat studies after a variety of hemodynamic interventions and in a prospective group of 32 additional patients (mean age 63 ± 11.6 years, pressure range 7 to 28 mm Hg). The highest correlations with occlusive pressure were observed with the E/A ratio (r = 0.75), IVRT (r = −0.55), atrial filling fraction (r = −0.65), and deceleration time (r = −0.50). Pulmonary venous recording could be obtained in only 16% of patients. The best model was with E/A and IVRT: PA occlusive pressure = 17 + (5.3 E/A) − (0.11 IVRT), r = 0.79. In the group with repeat studies, a significant correlation was observed between predicted and observed changes in occlusive pressure (r = 0.87), with a mean difference between pressure changes of 0.4 ± 3 mm Hg. Similarly, in the prospective group, a significant correlation was observed between measured and Doppler-derived occlusive pressures (r = 0.88). Of the total 112 patients screened, Doppler estimation of occlusive pressure could be performed in 63%. Estimation of PA occlusive pressure is therefore feasible by Doppler in approximately two thirds of adult patients in intensive care units and may significantly contribute to management of the critically ill patient.