Evaluation of Lung Doppler Signals in Patients Presenting to EMD

Historically, ultrasound has been unable to provide interpretable data from the lung parenchyma, mainly because of the high total ultrasound energy attenuation and scattering by the air in the lungs. 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 (transthoracic 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. Preliminary data from ongoing studies employing the TPD in chronic diseases such as CHF, COPD and pulmonary hypertension, show promise regarding the diagnostic potential of the lung Doppler signals (unpublished data). However, lung Doppler signals in acute disease states were not investigated so far. It is reasonable to speculate that the pathological processes underlying acute cardiovascular and pulmonary diseases will affect the LDS. Therefore, the TPD may have diagnostic potential in these conditions. For example, during acute pulmonary embolism a portion of the pulmonary vascular system is occluded; therefore it's reasonable to assume that the LDS will disappear in the affected area, enabling to confirm the diagnosis without using ionizing radiation (as in CT