Monitoring patients in the operating room by measuring blood flow in the neck with ultrasound
Joris van Houte defended his PhD thesis at the Department of Electrical Engineering on June 5th.
It is crucial to closely monitor the circulatory system of critically ill patients, because proper blood flow is needed to supply all organs with oxygen. So far the most accurate way to monitor this has been through insertion of catheters into a blood vessel, but it carries risks such as infections and vascular damage. Therefore, there is an ongoing search for safer, non-invasive alternatives that do not require needle punctures. Carotid Doppler ultrasound (CDU) is an promising technique that uses sound waves to examine blood flow in the carotid artery and detect changes in circulation in a timely manner. Joris van Houte examined with his PhD research if CDU is truly useable and reliable as an alternative method for monitoring patient circulation, and which aspects of blood flow are most informative.
The carotid artery lies just beneath the skin in the neck, making it easily accessible for examination. That鈥檚 why focused on the blood flow in this point of the body. Within his PhD research he looked at three characteristics of blood flow: the amount of blood flowing through the carotid artery (blood flow), the duration of blood flow during each heartbeat (blood flow time) and the maximum velocity of the blood flow (blood flow velocity). First he studied the blood flow and the results showed that while the flow in the carotid artery is somewhat correlated with overall circulation, it is not precise enough to fully replace invasive methods. Measurements can be influenced by natural bodily mechanisms, such as the brain鈥檚 own regulation of its blood supply. Additionally, measuring blood volume can be prone to technical inaccuracies, making it difficult to reliably detect changes in circulation elsewhere in the body via the neck.
Blood flow time
After that, Joris van Houte examined the measurement of blood flow time. In some situations, this flow time closely matched measurements taken directly from the heart. Especially when looking at trends (changes over time), this parameter provided useful information. This may help to indicate whether a patient would benefit from additional fluid administration to optimize circulation. Further research in larger studies would be needed to confirm this.
Blood flow velocity
Finally, peak blood flow velocity in the carotid artery was examined. This parameter appeared promising, particularly when compared to similar measurements obtained via the current standard method using invasive catheters. Based on this study鈥檚 findings, this application of CDU also seems reliable for determining whether a patient might benefit from fluid administration.
Developing new technologies
Although it is still too early to claim that CDU alone can replace standard patient monitoring methods, flow time and flow velocity do show potential for future use. Especially in combination with other clinical data, CDU may contribute to the early recognition of clinical deterioration in a patient. Future research now focuses on improving these measurements and developing new technologies, such as an ultrasound patch that can measure blood flow continuously and wirelessly, without the involvement of a doctor or nurse. This brings us closer to a future in which critically ill patients can be helped more quickly, safely, and comfortably.
Title of PhD thesis: Supervisors: Prof. Arthur Bouwman, Prof. Massimo Mischi and Dr. Leon Montenij.