Abstract

An assessment of a non-invasive technique for measurement of stroke distance was made using a portable Doppler ultrasound machine. The aim was to determine the measurement error of repeated stroke distance measurements (within-observer variability) and to assess measurement agreement between two operators (between-observer variability). The measurement error (within-observer variability) for both operators was similar at approximately 2 cm. However, the measurements of the two operators (between-observer variability) did not agree well. Using the mean (SD) of three readings by each operator, the mean difference between the operators was −0.21 cm (1.96) giving a 95% confidence interval for the differences of −4.0 to +3.6 cm. There were significant positive and negative correlations between stroke distance and a variety of variables (age, height, weight, heart rate), but the relations were weak. The results indicate that the Doppler ultrasound technique for measurement of stroke distance would best be used to study trend changes in an individual patient, or subject, by a single operator.