Final answer:
To calculate the heart rate on a regular rhythm EKG strip, measure the time interval between R waves using the grid on the EKG paper and apply the 300 rule by dividing 300 by the number of large squares between two R waves.
Step-by-step explanation:
When the rhythm is regular on an EKG strip, the heart rate can be calculated by measuring the time interval between consecutive R waves (the highest points of the QRS complex). To do this, you can use the small square grid on the EKG paper, where each small square typically represents 0.04 seconds. If you know the paper speed (commonly 25 mm/s), you count the number of small squares between two R waves and then use this number to calculate the heart rate. A quick method is to use the 300 rule, which involves dividing 300 by the number of large squares (each large square is made up of 5 small squares and represents 0.20 seconds) between two R waves. The resulting number is an approximate heart rate per minute.
If the heart rhythm is abnormal, such as when there are irregular beats or extra beats, this method may not be accurate, and other techniques or more thorough analysis may be required to determine the heart rate.