What does physics have to do with medicine?
I distinctly remember a night early in my career, I was working the overnight in a quaint community hospital. I was half-sleep when the nurse told me we had a new patient in the ED. It was an otherwise quiet night in the department so I walked over and saw her while the nurse was doing the triage. It was a 50-something year old woman who was complaining of shoulder pain that woke her up from her sleep. She had done a good job of taking care of herself thus far but was not afraid to come to the doctor if she thought something was wrong. She couldn’t fall back asleep so she decided to come to the ED to be evaluated. After talking with the patient, I asked the nurse to get an EKG. I went back over to my computer and sat down to start my note. The nurse shuffled over to me and handed me the EKG. After about 2 seconds of reviewing it, I jumped up and started barking out orders. The patient was having a myocardial infarction (MI) or heart attack.
As an emergency physician I see hundreds of electrocardiograms (ECGs or EKGs) a week. To the untrained eye the pages look like squiggly lines on a paper but in my profession, those same lines can be the difference between life and death. Understanding what the lines mean helps me determine if the heart’s electricity is functioning normally, if blood flow is adequate to the various portions of the heart or if there are signs of ischemia or blockage of the blood vessels. We also use EKGs to determine if a patient has an abnormality in their blood due to toxins or electrolytes. So much information from a few squiggly lines.
I won’t go into too many specifics when it comes to the physics behind the heart, its electricity and blood flow but I will say this, the heart is a complex machine with many moving part. It is simple yet efficient. It moves unoxygenated blood thru the lungs and to the rest of the body. Its power source is simple. It functions with accuracy and precision with each cycle or beat thousands of times a day.
Understanding how the heart works on a macro (large scale) or micro (small scale) level requires and understanding of physics. It requires an understanding of how electricity is generated as positive energy flows down a gradient to depolarize the cells of the SA node that leads to the contraction of the the heart muscles. It also requires the understanding of pressure gradients and flow of fluid through pipes (or vessels) in order to understand the intricacies of the circulatory system and blood pressure.
Along with the normal function of the heart, an understanding of physics can help you understand what’s wrong with the heart, with the help of the EKG. A typical QRS complex indicates a single heart beat. It includes multiple sections that tell the story of the electricity of the heart. Changes in those QRS complexes can indicate a toxidrome or ischemia (lack of blood flow). Without an understanding of the physics, physicians wouldn’t be able to use EKGs as a diagnostic tool.
Check out this link: http://ecg.bidmc.harvard.edu/maven/mavenmain.asp. It is a website that has hundreds of EKGs that you can peruse, test your diagnostic skills, and see why physics is important in the whole process.