Accuracy of radial pulse assessment by length of counting interval.

The purpose of this study was to determine the reliability and validity of counting resting and rapid radial pulse rates at 15-, 30-, and 60-second intervals. Difference scores were calculated between heart rates obtained by the 103 nurse subjects and rates obtained from simultaneous electrocardiographic tracings taken for the three counting intervals at resting rates and at rapid rates. Repeated-measures analysis of variance indicated no differences based on the subjects' educational level. Rapid heart rates (greater than or equal to 100 beats/min), as a whole, were significantly less accurate than resting rates (p = 0.0076). Although there was a significant main effect for length of counting interval (p = 0.0490), post hoc evaluation by Tukey's HSD test showed that only the 15-second rapid counts were significantly different from all the resting counts, but they were not different from the 30- or 60-second rapid counts. These results suggest that a 30-second counting interval may be the most accurate and efficient to use in counting the radial pulse and that the 15-second counting interval should not be used for rates faster than 100 beats/min.