OU-HCOM researcher studies causes,
prevention of fainting
 

Athens, Ohio – Thad Wilson, Ph.D., associate professor of physiology and a researcher with the Ohio University Heritage College of Osteopathic Medicine’s Institute for Neuromusculoskeletal Research, wants to find ways to keep people from fainting.

Wilson and Craig Crandall, Ph.D., a professor in the Department of Internal Medicine at the University of Texas Southwestern Medical Center, have been conducting experiments over the past 10 years to get answers for the one million U.S. patients evaluated annually for syncope (fainting).  It is estimated that about one percent of emergency department visits and hospital admissions are for evaluation of a syncopal episode, and individuals with cardiac or neurological disorders have an increased incidence of fainting.

“We determined that, as an individual starts to faint during heat stress, there’s a greater decrease in stroke volume—the amount of blood pushed out from the heart with each heartbeat—compared to when they are in neutral temperatures. This means there will be less blood traveling to the brain, which is one of the causes of syncope,” Wilson explains.

Wilson said their findings are important because they will enable scientists to start developing ways to counteract syncope. “Once you understand the mechanism of syncope, you can develop therapies to prevent it,” he said. “One therapy is to cool the skin of the individual, which can serve to increase stroke volume and prevent syncope. The other is to increase the amount of fluid the person has in their circulatory system by administering fluid intravenously and making sure they are adequately hydrated.”

In addition to individuals with cardiac or neurological disorders, people who work in warm settings and stand for long periods may be more likely to experience syncope. These include fire fighters, foundry workers, miners, bakers, construction workers and military personnel.  “We would like to take the information we gained from our laboratory studies and study syncope in actual workplace settings to see if we can develop simple and reasonable methods to counteract these occurrences,” Wilson said.

In their experiments, Wilson and Crandall manipulated body temperatures and the amount of blood returning to the hearts of healthy individuals in order to control when subjects were going to faint. Two devices — a water perfused suit and a lower-body negative pressure box—were used. A water perfused suit is tight fitting, with tubes for pumping in either hot or cold water. It was initially developed by NASA to keep astronauts cool when they are re-entering the earth’s atmosphere.

A lower-body negative pressure box is a Plexiglas box that is sealed at the subject’s waist. “Negative pressure is then created inside the box, which pulls blood toward their feet. The more negative pressure, the more they’re likely to faint because it’s preventing blood from returning to their heart,” Wilson explains. 

The researchers used heart catheterizations, echocardiography, and nuclear medicine procedures to measure the heart’s responses during their experiments. This was the first time these types of invasive measurements were conducted on humans to study syncope in different temperature conditions, according to Wilson.    

With grant funding from the National Institutes of Health and the American Heart Association, the two researchers, along with very talented collaborators, conducted experiments at four different laboratories or hospitals: Ohio University’s Institute for Neuromusculoskeletal Research, University of Texas Southwestern Medical Center, Penn State College of Medicine, and Rigshospitalet in Copenhagen, Denmark.

Wilson and Crandall co-authored an article, “Effect of Thermal Stress on Cardiac Function,” that is a synthesis of eight other research articles they co-wrote and published over the past decade. The article was featured on the cover of the January 4 issue of Exercise and Sports Sciences Reviews, the quarterly journal of the American College of Sports Medicine. The journal presents the most contemporary scientific, medical and research-based topics emerging in the field of sports medicine and exercise science.