Heart Rate and Pulse

Pulse

Pulse is essentially the rhythmic reflection of your heart’s activity—specifically, one beat or one systole of the heart. In other words, it corresponds to a single cardiac cycle. This cycle is a full cycle of the heart pumping and the heart filling with blood.  Although pulses exist in veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge within the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu, they’re too far from the heart—the pump—to be easily detected. This is why we measure pulses in arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr instead. Arteries, being closer to the heart, are where you can actually feel that rhythmic pulsing. The closer the artery is to the heart, the stronger and more pronounced the pulse will feel.

Now, take a moment to visualize this. If you were to look at a diagram, you’d see the heart located centrally. As blood travels away from the heart to different parts of the body, the distance impacts the pulse’s strength. The pulse weakens with increased distance. The farther the blood travels, the weaker the pulse feels.  For instance, consider the femoral artery, which is located in your thigh. The aorta descends from the heart. It branches off to supply blood to major organs like the kidneys. Then, it continues down to the femoral artery. This large artery delivers blood to your lower legs, which bear much of your body’s weight. Because your legs have more muscle mass compared to your arms, the femoral artery carries a larger volume of blood.

Personally, I prefer checking the carotid artery in the neckNarrow region just below the head; common fracture site. to detect a pulse. It’s closer to the heart and offers a strong, reliable signal.

To detect your radial pulse, follow these steps. Place two fingers on the radial side of your wrist. That’s the side closer to your thumb. Use light pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. and focus on the thinnest area of the skinThe body’s largest organ, providing protection and regulation. for the best results.

When recording your pulse, there are several methods you can use:

•Count for 15 seconds and multiply by 4.

•Count for 30 seconds and multiply by 2.

•Or, for the most accurate result, count for a full 60 seconds.

Heart Rate

Your heart rate (beats per minute) equals the number of pulses per minute. It corresponds to the number of cardiac cycles per minute, which is one round of pumping and filling.  This measurement gives us an idea of how many of these cardiac cycles you are having. I can use this number to make some calculations. I can also estimate the amount of blood that is leaving your heart. 

First, we obtain stroke volume from a source.  Stroke volume for age, height, weight, and all that have been estimated from cadavers.  We are going to use a pretty average stroke volume for an adult which is 70 milliliters of blood.  That’s not a lot.  It’s like a little more than half a stick of melted butter. 

Stroke volume is the amount of blood that is leaving a ventricle with one cardiac cycle. Cardiac output is the amount of blood that is leaving a ventricle in one minute. In order to calculate cardiac output I need to know how many cardiac cycles somebody is having in one minute. This is pulse or beats per minute.  This equation tells us that cardiac output is proportional to both stroke volume and heart rate. Proportional means that if stroke volume goes up so does cardiac output. If stroke volume goes down so does cardiac output. The same applies for heart rate it rises and lowers in proportion to the cardiac output. Knowing this equation allows us to consider instances that affect the stroke volume and the heart rate such as exercise.

Calculating HR

Heart rate can be calculated from an EKG paper.  Those little blocks on the background of the EKG strips represent time.  Can you see the thicker outlines of the larger boxes?  Those represent one second.  Both of these strips represent 5 seconds of heart contractions.  Let’s consider the strip on the top.  We seem to have 6 cardiac cycles or 6 heart beats per 5 seconds. So, it’s like I hooked up my patient for 5 seconds and took an EKG.  They have 6 QRS waves for these 5 seconds or 6 cardiac cycles for these 5 seconds.  Heart rate is always reported in bpm or beats per minute.  There are some calculations we have to do to get how many beats are in one minute.  Let’s make two fractions.  One will be 6 over 5 to represent our EKG strip’s 6 beats per 5 seconds.  The other fraction will have a question mark up here and 60 seconds down here.  Cross multiply 6 times 60 and then divide by 5 to get 72 beats per minute.  If I hooked up this patient and let it run for one minute, I’d see 72 QRS waves. 

Stop this video and do the calculation for the bottom EKG.  Did you get 96?  We’d have 8 over 5 and question mark over 60.  Doing that cross multiply and divide, we get 96 beats per minute. 

Stop this video and do the calculation for the bottom EKG.  Did you get 96?  We’d have 8 over 5 and question mark over 60.  Doing that cross multiply and divide, we get 96 beats per minute.