The average med student regards physics is a necessary evil - a penance to placate the MCAT gods and then promptly forget. After all, most of us got into this business because we liked biology, not math. And yet as I've progressed through my first two years, I've noticed that hidden among the touchy-feely biologists are a handful of physics-heavy specialists who actually use those long forgotten equations to do their jobs.
Today we got a nice refresher on fluid dynamics from a cardiologist who specializes in echocardiography (using sound waves to image the heart, much like sonar in submarines). The following equations came up while discussing the flow of blood between the atria in a patient with an atrial septal defect:
This is when the cardiologist coyly grinned as we all scratched our heads. Why would there be a flow of blood when there is no pressure difference? To the physics! Looking back at the equations above (or just remembering from physiology), flow (Q) is related to both pressure AND resistance. So, if the pressure is the same between the connected chambers and blood is still flowing, then the resistance must be different, and this, in fact, is the case.
TIL: Replacement valves last longer in place of the aortic valve than mitral valve. This is fairly counterintuitive because the aortic valve is generally dealing with bigger pressures. BUT, the mitral valve deals with a bigger change in pressure (AV: 120/80 vs MV: 120/12), and it's this that really causes the wear and tear.
Today we got a nice refresher on fluid dynamics from a cardiologist who specializes in echocardiography (using sound waves to image the heart, much like sonar in submarines). The following equations came up while discussing the flow of blood between the atria in a patient with an atrial septal defect:
P = Q × R ∴ Q = P / RA septal defect is when there is an abnormal hole in the heart connecting either the two atria or ventricles, neither of which are supposed to be connected. Generally, the left side of the heart is under more pressure than the right, so one might assume that blood would flow from the left to the right when there is gaping hole in the septum. With a big enough hole, the pressures equalize and you'd expect the flow through gap to stop... but it doesn't!
This is when the cardiologist coyly grinned as we all scratched our heads. Why would there be a flow of blood when there is no pressure difference? To the physics! Looking back at the equations above (or just remembering from physiology), flow (Q) is related to both pressure AND resistance. So, if the pressure is the same between the connected chambers and blood is still flowing, then the resistance must be different, and this, in fact, is the case.
TIL: Replacement valves last longer in place of the aortic valve than mitral valve. This is fairly counterintuitive because the aortic valve is generally dealing with bigger pressures. BUT, the mitral valve deals with a bigger change in pressure (AV: 120/80 vs MV: 120/12), and it's this that really causes the wear and tear.
Don't defibrillate people when they're awake. Generally not considered good bedside manner. If a shock would be good to reset their arrhythmic heart, knock them out first.
Rivaroxaban and apixaban have their mechanism in their names. What?! An intuitively named drug?! Crazy, I know! These anticoagulants counteract or ban Factor Xa. ban Xa → Xa ban → "-xaban". Tada!
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