Veterans Affairs

TrueRAP: device standardizes breathing efforts during echocardiograms

Adds validity and reliability to heart ultrasound measurements of right atrium pressure for improved diagnosis of heart failure

Medical & Biotechnology

Image: Pixabay

Scientists at the U.S. Department of Veterans Affairs (VA) have recently developed a medical device which standardizes echocardiography estimates of right atrium pressure (RAP) leading to more accurate diagnosis of heart failure. The patented technology is available via patent license agreement to companies that would make, use, or sell it commercially.

An echocardiogram is an ultrasound of the internal parts of the heart. Recent reports suggest that over 7 million echocardiograms are performed on Medicare beneficiaries each year. Among these, standard transthoracic echocardiograms are the most common. Part of the reason for their popularity is that they provide a noninvasive estimate of RAP, which has important diagnostic and therapeutic implications related to heart failure.

RAP is estimated from an echocardiogram by observing how the diameter of the inferior vena cava changes with breathing. Unfortunately, this estimate often does not reflect a patient’s true RAP due to measurement error. A major source of this error is how patients breathe when ultrasound images are recorded.

Effortful breaths (high volumes of air over short periods of time) are achieved by forceful expansions of the lungs. This lowers the pressure in the chest, and as a physiologic consequence, airflow increases to the lungs. The lower pressure in the chest also lowers RAP directly, which increases the flow of blood back to the heart. A drop in RAP and an increase in blood flow back to the heart will tend to collapse the inferior vena cava. The degree of this collapse depends heavily on just how effortful the breaths are. When the effort of breathing is known, the amount of collapse of the inferior vena cava can be used to estimate the RAP. Thus, results vary along with individual breathing differences and in the different ways in which sonographers instruct patients to breathe.

Now, a VA researcher has developed a device which standardizes breathing efforts during echocardiogram estimates of RAP. While such impedance threshold devices (ITDs) have been around for over 30 years they have not included the ability to adjust the level of required respiratory level (impedance). The new device from the VA is adjustable so that the required threshold can be increased or decreased, depending on both the baseline breathing effort of the patient and the inspiratory effort needed to cause inferior vena cava collapse.

The device is handheld and disposable. In operation, it employs a series of valves that create a slight amount of resistance during inspiration. This resistance helps to ensure that patient breathing effort does not change moment to moment. It also enhances the negative pressure in the chest which as mentioned above, draws blood back to the heart and causes the inferior vena cava to collapse. Knowledge of breathing effort coupled with the echocardiogram showing the amount of vein collapse yields the diagnostic information.

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