You’ve probably seen CPR performed in popular media. Almost every episode of your favorite medical drama features an unconscious patient rushed in on a gurney, with a paramedic pushing rhythmically on their chest. A doctor takes over, administers some of the well-recognized ‘epi’ and shocks, the monitor beeps and displays a sinus graph and the patient sputters awake. The next idyllic scene shows them all well again.
Real life is a little messier, as it tends to be.
Emergency medical services take, on average, 8 minutes to arrive at a call. After that, they take about 30 minutes to reach a hospital and get the patient looked onto machines, performing CPR throughout. In that time, the heart is not pumping so all the blood in a body is sitting stagnant. With no flow, new oxygen and vital nutrients can’t reach all the cells. Stagnation also allows clotting factors to react with each other and activate the clotting mechanism, which blocks flow even when pumping is restored and makes the accessibility to cells worse. The first blood vessels to suffer are called micro-capillaries, the smallest in the body located in fingertips, the tongue and most importantly, the brain. The CPR paramedics perform is not perfect- the motion cannot
exactly mimic the contractions of the heart, so the flow is still very reduced.
Preventing as much cognitive injury from these microcapillaries is the most important goal. And that’s where the ECMO machine comes in.
Many patients who require this type intervention are put on the ECMO machine in the hospital, an external heart and lung machine that oxygenates and pumps blood much more efficiently until their heart is fixed. (Quick aside: the ECMO machine was pioneered at the University of Michigan by Dr. Bartlett in the 80s!) There is, however, a caveat, in which the patient has to be taken off of the ECMO machine in 8 hours, or the body produces a massive immune response
that can causes irreversible and fatal inflammation. The ECMO machine is plastic-based and the oxygenator works by introducing direct oxygen to the blood hemoglobin. Turns out blood reacts poorly to touching anything other than blood vessel walls, including the oxygen since, physiologically, it is passed through the lung alveoli membrane first.
Interestingly, staying on the ECMO machine for even a few hours, though it saves lives, can produce debilitating effects on the kidneys. My work is centered on the ECMO process, where my lab tests proprietary combinations of new drugs on ECMO that can help alleviate the effects of clotting and restore
brain function. We are also working on using nitric oxide gases to increase the safety and longevity of the machine itself, since NO and NO2 have been shown to be inhibitory inflammatory activators.
We use pigs and sheep to recreate the exact conditions in which people usually collapse and receive CPR. Animal models are often used in life sciences when a complex systematic response needs to be studied. Then, we put them on ECMO simulations in different drug combinations and trials to record the effects on the heart, the brain and capillaries. For the brain, we measure intercranial pressure which tells us if it is swelling, and we also use a very powerful camera to
actually see the microcapillaries in the tongue in real-time, where you can even make out individual RBCs flowing. I work on the heart, which is wholly monitored on a BioPak machine through pressures from the aorta and each chamber. I collect and compare heart data of the animal before the entire prep and after, to analyze how the efficiency and viability of the cardiac muscle has changed from being on ECMO. The end goal is to get the heart beating and patients weaned off the ECMO as soon as possible without lasting damage. The lab also has other cool projects running simultaneously, like artificial lungs for people waiting on lung transplants and an external placenta for premature babies!
The author works at ECLS Bartlett Laboratory, University of Michigan Ann Arbor.
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