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Using Laser Speckle Imaging to Provide Early Warning for Hemorrhages During Labor

A wearable optical device for early detection of hemorrhage during labor or after childbirth has been developed by scientists.

Using Laser Speckle Imaging to Provide Early Warning for Maternal Mortality

Researchers developed a wearable wrist-worn device that uses laser speckle imaging to catch early signs of postpartum hemorrhage. Image Credit: Francesca Bonetta-Misteli, Washington University in St. Louis

Severe heavy bleeding could be hard to detect before it becomes an emergency and accounts for nearly 30% of maternal deaths around the world and just more than 10% of maternal deaths in the United States.

Studies have shown that early diagnosis and treatment for postpartum hemorrhage is the best method to avoid death. The new device is developed to be worn on the wrist, where it utilizes laser speckle imaging to constantly track for a reduction in blood flow that offers an early sign that heavy bleeding is happening elsewhere in the body.

Postpartum hemorrhage most severely impacts people in low- and middle-income areas, who have limited access to high-quality medical diagnostics and treatments.

Christine O’Brien, Research Team Leader, Washington University in St. Louis

O’Brien added, “We were inspired to develop an accessible tool that can be used in both low- and high-resource settings to detect this condition earlier than current methods. This work is the first step in the development and proof-of-concept testing of our initial prototype.”

In the Optica Publishing Group Journal Biomedical Optics Express, the scientists provide studies that confirm the prototype’s potential to detect changes in blood flow utilizing a swine model of hemorrhage. Depending on such positive outcomes, they are currently performing studies with healthy volunteers.

Our hope is that this work will lead to a device that will enable prevention of morbidity and mortality caused by postpartum hemorrhage, ensuring new moms make it home safely with their babies,” said the paper’s first author Francesca Bonetta-Misteli.

Bonetta-Misteli added, “In a medical setting, it could be useful for monitoring how patients are responding to treatment for a hemorrhage. It could also offer a standalone tool for use at home or in other settings that alerts mothers giving birth when they may be in danger and should seek medical attention.”

Catching Early Signs

When a hemorrhage happens, the body initiates a process called peripheral vasoconstriction to redirect blood flow to the crucial organs by limiting blood to peripheral body parts that are less necessary, like the feet, hands, and arms. This results in a reduction in blood flow in the peripheral locations while blood flow remains normal in the body’s core.

Because of peripheral vasoconstriction, vital signs can remain unchanged until there is very severe blood loss, meaning that in many instances we cannot use vital signs to detect postpartum hemorrhage before it becomes severe.

Christine O’Brien, Research Team Leader, Washington University in St. Louis

O’Brien added, “By monitoring blood flow in the wrist, our device can detect peripheral vasoconstriction as it occurs in response to postpartum hemorrhage before the patient starts to show symptoms.”

A multidisciplinary research group, which included physicians and engineers, came up with the wearable device, which makes use of laser speckle flow index (LSFI) for hemorrhage-induced peripheral vasoconstriction detection.

LSFI pulls data regarding blood flow by utilizing a laser and a camera to detect and measure temporal and spatial alterations in speckle patterns that are developed when light interacts with flowing blood cells.

The scientists had to make a wireless, battery-powered laser speckle system that could be worn on the wrist even though wearable laser spot imaging sensors have been developed for real-time tracking of cardiovascular physiology and blood flow. Also, they developed a quick speckle processing protocol for onboard video data processing.

Testing Sensitivity to Blood Flow Changes

The scientists positioned it on a tissue-mimicking phantom with a hollow channel, via which they flowed a milk-like liquid for the blood flow to be simulated.

When the scientists changed the rate at which the liquid flowed over a range that would be expected in blood vessels, the scientists noted an almost ideal linear response to the flow rate. This showed that the device was very sensitive to blood flow at the anticipated physiological conditions.

Further, they performed a hemorrhage and resuscitation study in a swine animal model. Since test animals lost blood, the device detected near-immediate, constant decreases in blood flow.

The response obtained was nearly perfectly linear, having an average correlation between detected blood flow measure and volume of blood removed of 0.94. Besides, in the majority of the animals, the device quantified an increase in blood flow at the time of the intravenous injection with saline. This points out that the added volume aided in increasing blood flow to the periphery.

This demonstrates that the wearable laser speckle imaging sensor could be utilized to track patients for early signs of postpartum hemorrhage and also track their response to resuscitation efforts.

Currently, scientists are making new prototypes that utilize a highly stable, smaller laser consisting of lower laser power and a longer battery life, and that could offer quicker outcomes. Besides testing the device with healthy volunteers, the researchers plan to start enrolling pregnant women in a clinical study at Washington University in the forthcoming months.

They are planning to collaborate with investigators from countries with high mortality rates as a result of postpartum hemorrhage to test the performance of the device and its utility in resource-limited settings.

To move beyond research application to true clinical use, the device would need to be manufactured by a commercial partner that can create a device that meets regulatory criteria, and this device would need to undergo testing under a number of conditions and with a diverse population.

Christine O’Brien, Research Team Leader, Washington University in St. Louis

O’Brien added, “It will also be critical to obtain feedback from patients, nurses, physicians, and other members of the healthcare team throughout the development process.”

We are obtaining feedback and conducting many of these tests with our research prototypes, including the consideration of artifacts caused by motion and testing performance across a range of skin pigmentation levels to ensure the results are not biased by skin color,” continued O’Brien.

Journal Reference

Bonetta-Misteli, F., et al. (2023) Development and evaluation of a wearable peripheral vascular compensation sensor in a swine model of hemorrhage. Biomedical Optics Express.


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