Pulmonary Blood Flow Measurements in CHF Patients

Historically, transthoracic Doppler echocardiography has been unable to provide interpretable data of blood flow within the lung parenchyma because of air attenuation of Doppler signals. Recently, a transthoracic Doppler system known as the Sonara/tek Transcranial Doppler (TCD) System has been developed that can identify parenchymal pulmonary blood flow (PPBF) signals. The ability to non-invasively collect information regarding the pulmonary aspect of the cardio-pulmonary system may provide valuable information and new insights into the structural and functional characteristics of the lung parenchyma and vasculature in health and disease states.

This new system was previously studied among 31 healthy volunteers and one subject with atrial fibrillation.1 Pulsed spectral Doppler signals were obtained over the chest wall using a signal processing and algorithm package in conjunction with a non-imaging Doppler device coupled with an electrocardiogram. Clear reproducible lung Doppler signals (LDS) originating from different elements and phases of cardiac activity that generate mechanical waves which propagate throughout the lung were expressed in pulsatile changes in ultrasound reflections. After the completion of the first 25 patients in our pilot study, we have received some valuable information. After assessing patients with CHF and pulmonary hypertension, we identified signals particular to the CHF group. There were unique features that were never observed in the normal patients. On top of the regular Lung Doppler signals seen in normal patients, high velocity "disorganized" variable signals that were not synchronous with the heart beat, but rather sometimes with respiration were observed. We believe that the signals may represent popping open of small bronchi surrounded by "water filled" parenchyma. These events that generate very strong reflector like signals may represent the movement of fluid at the blood vessel-alveolar air junction.