Army Improving CRI

Researchers at the Army Institute of Surgical Research (ISR) in San Antonio and at Fort Sam Houston Texas are improving medical monitors that have been used in clinics and hospitals since the early 1970s helping physicians and medical staffs assess a patient’s condition. The Compensatory Reserve Index (CRI) is a new algorithm that uses the information obtained from a standard pulse oximeter and gauges whether a patient requires resuscitation or immediate medical attention.

“The CRI can evaluate information from waveforms generated by taking a standard pulse oximeter, which is a non-invasive medical device routinely placed on a finger or ear that can measure levels of blood oxygen saturation and heart rate,” said Victor A. Convertino, PhD, Tactical Combat Casualty Care Research Task Area Program Manager at the ISR. “The algorithm provides a decision support system that could help a young medic who doesn’t have the experience needed in pre-hospital care to make life-saving decisions.

The CRI has a gauge much like a fuel gauge in a vehicle to indicate when fuel is running low. The CRI gauge will then begin to show a loss in fuel well in advance of changes in blood oxygen or heart rate measured by the pulse oximeter.

According to Convertino, when a person is injured and bleeding internally, the body compensates by increasing heart rate and constricting blood vessel responses that can elevate blood pressure, but at the same time, the patient’s vital signs can appear normal to the attending clinician.

However, the CRI will show that the patient is in danger when the pulse oximeter alone will not show the danger. “A person can be bleeding internally and seem normal until the body can no longer compensate and then will go into shock in a matter of seconds,” said Convertino.

Convertino and his team have conducted experiments on more than 230 participants using a Lower Negative Blood Pressure (LNBP) machine as a model of hemorrhage to collect the data that has been downloaded onto the algorithm. “The physiology of using the LNBP machine looks the same as if someone were bleeding,” he said.

The CRI now requires FDA approval and it is anticipated that CRI will receive FDA clearance within the next year. In addition, a protocol to conduct clinical trials has been developed.

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