Gary Muniz, left, Carmen Hinojosa-Laborde, Ph.D. and Victor “Vic” Convertino, Ph.D. place monitors on a volunteer in the lower body negative pressure chamber to collect physiological data as part of a research protocol.
Story and photo by Steven Galvan, DBA
USAISR Public Affairs Officer
U.S. Army Institute of Surgical Research
5 JAN 2017
The U.S. Army Institute of Surgical Research at Fort Sam Houston, Texas, has a new research center focused on improving outcomes from the leading cause of death on the battlefield. The Battlefield Health and Trauma Center for Human Integrative Physiology or BHTCHIP was formed by the USAISR Senior Scientist to study inadequate tissue oxygenation associated with military trauma and battlefield health that will result in new knowledge and materiel solutions for accurate and timely assessment of warfighters suffering from hemorrhagic shock or compromised performance.
“The focus will be on developing advanced clinical assessment and intervention for improved outcomes of combat casualties suffering from hemorrhage and healthy Soldiers whose performance may be compromised by battlefield conditions,” said Victor “Vic” Convertino, Ph.D., Senior Scientist for the U.S. Army Medical Research and Materiel Command Combat Casualty Care Research Program. “The BHTCHIP includes the only research laboratory in the Department of Defense with the unique capability that allows for the study of the physiology of human hemorrhage and onset of hemorrhagic shock using the model of lower body negative pressure.”
The lower body negative pressure chamber (LBNP) consists of an airtight chamber that creates a vacuum below the waist of test subjects to simulate the reduction in blood volume in the upper body similar to that experienced with hemorrhage.
“LBNP simulates a person progressively ‘bleeding out’ without removing a single drop of blood from them,” explained Convertino.
The LBNP model used by the BHTCHIP is unique in that it has been used to collect physiological data from more than 270 volunteers exposed to simulated hemorrhage that leads to hemodynamic decompensation (early stage of shock). According to Convertino, the database has proven uniquely critical in the development of the only state-of-the-art capability in the world that will allow emergency medical caregivers the ability to assess the status of bleeding patients such as combat Wounded Warriors or assist unit commanders to recognize compromised Soldier performance.
That state-of-the-art technology is designed to measure the body’s compensatory reserve, the body’s ability to compensate for low-volume blood loss with minimal change in traditional vital signs, using an algorithm called the Compensatory Reserve Index (CRI) that utilizes the information from the arterial wave of a standard pulse oximeter. The CRI monitor gauges whether a patient or Soldier engaged in combat requires resuscitation or immediate medical attention due to a compromise in tissue oxygenation during low circulating blood volume states.
“The CRI is a non-invasive medical device that can evaluate information from waveforms,” Convertino said. “The algorithm provides a decision support system that could help battlefield care providers make earlier life-saving decisions or to assist unit commanders in recognizing when a Soldier’s performance is compromised which could potentially affect the unit’s mission.”
Convertino’s vision of the BHTCHIP is to continue to develop new clinical research protocols designed to provide experimental and clinical validation of the compensatory reserve as a measurement of tissue oxygenation.
“We have already developed new studies and the experiments are ongoing,” he said. “The preliminary results indicate that measurement of the compensatory reserve provides superior sensitivity and specificity for low circulating blood volume states than standard vital signs.”