Evaluation of Lung Doppler Signals in Pediatric and Adult Patients

Recently it has been shown that clear reproducible Doppler signals can be recorded from the lung parenchyma by means of a pulsed Doppler ultrasound system incorporating a special signal processing package parametric Doppler, TPD, EchoSense Ltd., Haifa, Israel). These lung Doppler signals (LDS) are in full synchrony with the cardiac cycle and can be obtained from the lungs, including areas remote from the heart and main pulmonary vessels. The LDS waves typically have peak velocities of up to 30 cm/s and are of relatively high power, making it possible to detect them despite the aforementioned attenuation by the air in the lungs. The LDS are thought to represent the radial wall movement of small pulmonary blood vessels, caused by pressure pulse waves of cardiac origin which propagate throughout the lung vasculature. The LDS may contain information of significant diagnostic and physiological value regarding the pulmonary parenchyma and vasculature, as well as the cardio-vascular system in general.

Pulmonary arterial hypertension (PAH) is a condition characterized by reshaping of the small pulmonary arteries with increase in pulmonary vascular resistance, leading gradually to right-sided cardiac failure. A trans-thoracic echocardiograph (TTE) is a test classically undertaken in order to screen for pulmonary hypertension. However, the systolic pulmonary artery pressure (SPAP) values thereby obtained are often imprecise and depend upon the expertise of the individual carrying out the test. Therefore, the pulmonary arterial pressure and cardiac output values have to be ascertained with a right-sided cardiac catheterization, which is considered the gold-standard, but is invasive.

In a pilot study of adult PAH patients (unpublished), lung Doppler signals have been shown to have the potential to diagnose pulmonary hypertension in two different ways: First, by measuring the degree of attenuation of the LDS during acute pressure rise in the chest cavity (i.e. during Valsalva maneuver). Second, by detecting differences between the LDS in patients with PAH and control subjects.

One of the objectives of the present study is to evaluate the lung Doppler signals in pediatric patients of various age groups, with and without pulmonary vascular disease. The second objective of the study is to verify previous findings of abnormal lung Doppler signals in adult patients with pulmonary hypertension.