AMES, Iowa – Most strokes and heart attacks in the world are ischemic. This means that a blockage or clot in an artery blocks oxygen-rich blood from reaching the brain or heart cells. Tissues can die if they are stopped for too long.
Similar to how exercise can help muscles adapt to more challenging workouts, increasing numbers of studies suggest that short, repetitive bouts of decreased circulation with a blood pressure monitor cuff could reduce tissue damage and protect against strokes and heart attacks. Researchers found that the non-invasive, simple procedure can improve vascular and cardiac function, lower blood pressure, and reduce the heart’s workload.
James Lang, Iowa State University assistant professor of kinesiology, consolidated nearly 100 studies – some of which he had conducted – into a review paper published in the Journal of Physiology. He explained that “remote ischemic ischemia preconditioning” (RIPC) is generally five minutes of high pressure on an individual’s arm followed by five minutes of rest. This process can be repeated up to four times.
Multiple studies have shown that RIPC can create a protective window 48 hours after the session ends. However, Lang’s laboratory experiments and others suggest that preconditioning for several days may increase protection and provide other health benefits.
Lang stated that RIPC has many potential applications. Lang said, “I believe there are a lot of possible applications and potential with RIPC; someone preparing to have a surgery; people having had a stroke or heart attack, which increases their risk of it happening again; people unable to exercise, pre-hypertensive, or sleep apnea.
Even astronauts might be able to reap the benefits of RIPC. Lang explained that astronauts work out for up to two hours per day to prevent muscle atrophy and cardiac disease caused by microgravity in space. A blood pressure cuff can be incorporated into their workouts to help them stay fit.
Filling the gaps
Lang stressed that more research is necessary to ensure that RIPC works in different environments and for diverse populations. In the 1980s and 1990s, animal models are the best sources of information about the mechanisms and duration of protective effects.
Lang said, “Unfortunately, a lot a researchers jumped quickly into large clinical studies in 2000s and their results were inconsistent because of a host of outside factors like the participants’ medications and physical and genetic factors as well as age and sex.” Lang added that a follow-up study by other researchers also found propofol suppresses the effects of RIPC.
Lang and other researchers have worked to bridge the gap between animal research, large clinical trials, and animal research.
“In the laboratory, we can do more controlled experiments with human participants, try out to figure what factors influence RIPC, and when it is best to administer RIPC.”
Lang’s laboratory
Lang and his research group found that a week of RIPC could increase participants’ microcirculatory capacity up to 50% in one study. Another study measured blood pressure drops and less intense “fight or flight” responses while participants were sleeping.
“Together it was improving participants’ blood Heart and Blood Vessels, and possibly reducing the workload for the heart.”
Lang measures study participants’ blood vessel dilation when exposed to warm skin. This is one way Lang can test the effectiveness of RIPC. Lang attaches a tiny, nickel-sized device to the arm of each participant before and after RIPC. A small heater heats the skin while a doppler shines a laser beam into the micro-vessels below.
Doppler Lang’s lab uses a similar technique to detect changes in atmospheric conditions. It measures the flow of red blood cells in response to heat.
Lang explained that a loss in blood vessel elasticity, i.e. the extent to which blood vessels can constrict or dilate, increases the risk for high blood pressure, Heart and Blood Vessels attacks, strokes, and dementia.
Lang is currently working with a Des Moines University researcher to see if RIPC can help those with diabetes who have slow-healing wounds. High blood glucose can cause damage to small blood vessels and nerves. Plaque coating can also make accessing white blood cells or nutrients challenging for cuts and sores.
Lang states that side effects of RIPC are infrequent, but anyone interested in trying it outside of a research study should first speak to their doctor.
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