Standard paper speed is 25mm/second. It is important to standardise the paper speed for evaluation of the heart rate and to enable accurate interval measurement of the ECG complex. If the paperspeed is changed, it is essential that this is clearly marked on the ECG recording.
Potential problems can occur if the paperspeed is changed and not acknowledged by the ECG machine operator. For example, should the paper speed be changed to 50mm/second it can give the appearance of a slow heart rate, known as a bradycardia. Equally if the paperspeed settng is decreased to 10mm/second it can give the appearance of a faster heart rate, known as a tachycardia.
Calibration relates to the size of the complexes and is important in determining the size of the heart muscle. The standard calibration is 10mm/mv. Large ECG complexes indicate large muscle mass. If the calibration is halved to reduce the size of these complexes, this must be clearly indicated on the recording.