Measuring Blood Pressure in the Lung Circulation With Sonar Technology (Echo-Doppler)

Overview

This is a non-invasive study using a standard doppler echocardiographic transducer which records signals emanating from the lungs (TPD). These signals are caused by pulsation of blood vessels in the lung tissue. The innovations in this study are: 1. The software processing of the reflected ultra-sound waves from the lung rendering a reproducible, clear and strong signal in sync with the cardiac cycle, 2. The observation based on pilot studies that blowing hard against resistance during recording (something called a Valsalva maneuver), affects the lung signal weakening it and even obliterating it as the pressure rises. The investigators hypothesis is that since the signal comes from the blood vessels in the lung, the pressure at which the recorded signal disappears during the Valsalva maneuver represents the blood pressure in the lungs.

Current methods for noninvasive measurement of pulmonary arterial blood pressure by standard echo-doppler equipment are fraught with uncertainty. So much so that patients being screened and followed for pulmonary arterial hypertension require right heart catheterization. An invasive and uncomfortable and potentially dangerous procedure. This study is designed to confirm our preliminary observation that there is good correlation between Valsalva maneuver pressure and pulmonary arterial blood pressure. Sixty patients undergoing right heart catheterization for clinical reasons will be studied. The study itself is short, about 30 minutes, painless and done with the patient either sitting up in bed or semi-reclining. The probe is positioned over the right chest wall and the patient is requested to successively blow into a mouthpiece at rising pressures, to tolerance. The results obtained using TPD to asses pulmonary arterial pressure will be compared to the results obtained at catheterization. This is part of the development phase of the technology.