Sep 1 2020
Scientists are developing a novel device that may gage the effects of blood loss caused by hemorrhage more precisely.
Measuring seismic vibrations and heart timing: Researchers have shown that they can accurately assess blood loss by measuring seismic vibrations in the chest cavity and by detecting changes in the timing of heartbeats. That could lead to the development of a smart wearable device that could be carried by ambulance crews and medics and made available in emergency rooms and surgical facilities. Image Credit: Georgia Institute of Technology.
The device may someday allow emergency room physicians, military medics, and emergency medical technicians (EMTs) to improve treatments for victims injured by gunshot wounds, vehicular accidents, and battlefield wounds.
A team of researchers has currently demonstrated that the new device can precisely assess blood loss by identifying the variations in the timing of the heart’s activity and quantifying the seismic vibrations in the chest cavity.
This understanding, which was developed in laboratory settings, could help create an intelligent wearable device that can be easily carried by medics and ambulance crews and can be made available in surgical facilities and emergency rooms.
We envision a wearable device that could be placed on a person’s chest to measure the signs that we found are indicative of worsening cardiovascular system performance in response to bleeding. Based on information from the device, different interventions such as fluid resuscitation could be performed to help a victim of trauma.
Omer Inan, Associate Professor, School of Electrical and Computer Engineering, Georgia Institute of Technology
The Office of Naval Research has funded the study, which was reported in the Science Advances journal on July 22nd, 2020. The study involved collaborators from the Translational Training and Testing Laboratories—an affiliate of Georgia Institute of Technology—in Atlanta and also from the University of Maryland.
Many different kinds of trauma can lead to blood loss, but at times, the hemorrhage can be masked from doctors and first responders. For example, individuals suffering from trauma and blood pressure—which is currently the oft-used measure of hemorrhage—usually have elevated heart rates. Such elevated heart rates can continue to be stable until the blood loss reaches a stage that is life threatening.
It’s very difficult because the vital signs you can measure easily are the ones that the body tries very hard to regulate. Yet you have to make decisions about how much fluid to give an injured person, how to treat them—and when there are multiple people injured—how to triage those with the most critical needs. We don’t have a good medical indicator that we can measure noninvasively at an injury or battlefield scene to help make these decisions.
Omer Inan, Associate Professor, School of Electrical and Computer Engineering, Georgia Institute of Technology
In this study, Inan and graduate students Jonathan Zia and Jacob Kimball used animal models and carefully analyzed electrical signals from the heart and seismic vibrations from the chest cavity as the amount of blood was slowly decreased.
The team preferred to assess the externally quantifiable indicators of the performance of cardiovascular system and evaluate them against the data given by catheters, making direct measurements of both the blood pressure and blood volume.
Seismocardiogram turned out to be a major indicator. It is a measure of the micro-vibrations created by the contractions of the heart and the discharge of blood from the heart into the vascular system of the body.
However, the team also observed the variations in the timing of the heartbeats as the amount of blood decreased. This offered yet another measure of a waning cardiovascular system.
The most important lower-level feature we found to be important in blood volume status estimation were cardiac timing intervals: how long the heart spends in different phases of its operation. In the case of blood volume depletion, the interval is an important indicator that you could obtain using signals from a wearable device.
Omer Inan, Associate Professor, School of Electrical and Computer Engineering, Georgia Institute of Technology
Such noninvasive electrical and mechanical measures in this device could be integrated to demonstrate how a patient’s blood loss can clearly become a serious issue.
The measurements would be used by machine learning algorithms to create a simple numerical score, wherein larger numbers denote a more critical condition.
“We would give an indicator that is representative of the overall status of the cardiovascular system and how close it is to collapse,” added Inan. “If one patient is rated 50 and another is 90, first responders could give priority to the patient with the higher number.”
Apart from emergency situations, the latest assessment method could even prove useful with several types of surgery, where rapid identification of unseen blood loss could enhance the outcome for patients.
Inan and his colleagues hope to develop a model device in upcoming studies. This device may take the form of a patch measuring only 10 mm2.
Nevertheless, more electrical engineering will be required to ensure an effective operation when the patient is being shifted, and to filter out the kinds of background noise that might exist in real-world trauma situations.
“Long-term, we want to partner with clinicians to do studies in humans where we would use the wearable patch and be able to take measurements when people were coming into the trauma bay, or even while EMTs were still deployed,” added Inan. “This could become a new way of monitoring hemorrhage that could be used outside of clinical settings.”
In addition, the team has also planned to explore the opposite issue—that is, how to find out when sufficient fluid has been given to an injured person. Excess fluid can lead to edema, which is analogous to the conditions of heart failure patients in whom the lungs are filled with liquid.
The study is based on research work funded by the Office of Naval Research (ONR) under grant N000141812579.
Journal Reference:
Zia, J., et al. (2020) Enabling the assessment of trauma-induced hemorrhage via smart wearable systems. Science Advances. doi.org/10.1126/sciadv.abb1708.