Certified EkG technician (CET) Practice Exam

When should the technician use the 300 method?

1. During a physical examination

2. When calculating a full cardiac cycle

3. For measuring blood pressure variations

4. When performing a Holter monitor test

The correct answer is: When calculating a full cardiac cycle

The 300 method is a technique used specifically in the interpretation of EKGs to calculate the heart rate from an ECG strip, particularly when the rhythm is regular. This method takes advantage of the predictable structure of the EKG waveform, where you count the number of large squares between R waves and use this to determine the heart rate. By knowing that there are 300 large squares in one minute of a continuous EKG strip, the heart rate can be calculated with the formula: 300 divided by the number of large squares between successive R-waves. This makes the 300 method particularly effective when computing the rate for a full cardiac cycle as represented on a standard EKG. The other contexts, such as physical examinations, measuring blood pressure variations, or conducting a Holter monitor test, do not specifically utilize the 300 method for heart rate calculation; therefore, they are not relevant for this technique. The 300 method is exclusively applicable when interpreting the rhythm and heart rate of a regular EKG tracing.