Diffuse correlation spectroscopy (DCS) is a new optical method using near-infrared light for noninvasively measuring brain-blood flow. [Photo by J. Adam Fenster/University of Rochester]
ECMO therapy is a life-saver for acute heart or lung failure patients. During therapy, blood flows out of the vein through tubes and into a machine that performs the actions of the heart and lungs. The oxygenated blood is then returned to the body to allow the heart and lungs to rest.
ECMO can stabilize critically ill patients in an intensive care unit, but the procedures can have many risks, including brain injuries, the researchers suggest. Patients undergoing that treatment are often comatose, but current neuromonitoring techniques are too risky and invasive to perform on a routine basis.
The researchers designed the devices to monitor the cortex, the brain’s outermost layer where neurons reside. Multiple devices are linked together, including electroencephalography (EEG) that studies electrical activity, and a new optical method called diffuse correlation spectroscopy (DCS) that measures brain-blood flow. The University of Rochester researchers also used evoked potentials, which are measurements of the electrical signals produced by the nervous system in response to external stimuli. Evoked potentials help examine deeper structures in the brain.
“Using near-infrared light, we can noninvasively evaluate blood flow about 1 cm into the brain tissue,” said researcher Regine Choe, an associate professor of biomedical engineering and electrical engineering. “This is done by bouncing light off the red blood cells in the brain’s capillaries.”
According to Choe, much of the brain’s health can be measured through blood flow and neural activity.
“The correlation between blood flow measured by DCS and neural activity measured by EEG can tell us a lot about the health of the brain. We believe evoked potentials will provide important indicators about whether a patient can potentially wake up from their coma,” she said.
More about the therapy
ECMO monitoring researchers Regine Choe (center), Imad Khan (right) and Irfaan Dar (left) pose with diffuse correlation spectroscopy (DCS) sensors that noninvasively measure brain-blood flow. [Photo by J. Adam Fenster/University of Rochester]
Choe and Khan have used DCS technology on the front portions of the brain, which has resulted in findings like asymmetric perfusion in the hemisphere. The researchers suggest that the finding could be caused by ECMO in comatose patients. The team wants to expand perfusion monitoring to the 20 locations of the brain that are often used for EEG monitoring to create an additional metric for brain health.
The University of Rochester researchers ultimately want to create a low-cost instrument that incorporates both modalities so that they can prepare for clinical trials.
“Our brains naturally have extremely intricate ways of controlling the amount of blood flow it receives, and how much oxygen and carbon dioxide need to be in the blood,” said Khan. “With ECMO, we are bypassing all of that to put blood flow and gas exchange in the hands of a clinician. Our device will provide clinicians with more data to make informed decisions about how to regulate these factors.”
Assistant professor of clinical medicine and cardiac intensivist Mark Marinescu is collaborating on the project and believes this technique could provide better patient care.
“A lot of times patients will come in unconscious because they are so sick and you have to make life-changing decisions about long-term medical devices to support them,” said Marinescu. “It would be really helpful to be able to predict if they are neurologically going to do okay afterwards. That would help us counsel patients’ families regarding what we should advocate for.”
