Continuous versus occasional measurement of blood pressure in reactivity testing

BACKGROUND: The Finapres device has provided a unique window for cardiovascular psychophysiological research because of its ability to track blood pressure beat-to-beat non-invasively. OBJECTIVE: To examine some of the implications for studying reactivity with this device versus with a standard cuff technique. METHODS: We examined systolic blood pressure, diastolic blood pressure and heart rate data of 20 subjects during resting baseline and during a stressful task (public speaking). We compared reactivity measured by using the Finapres device (the average response over 3 min) with lsquo;traditional ' reactivity judged in terms of the average of three randomly sampled blood pressure and heart rate values, as a proxy for cuff measurements. Between-subjects and within-subjects components of variance were estimated. RESULTS: The availability of the Finapres device with its multiple measurement of blood pressure and heart rate dramatically improved the reliability of measurement. For instance, use of a Finapres-like device is equivalent to increasing the sample sizes by 17-67%, depending on the physiological variable of interest. CONCLUSION: Continuous blood pressure measurements using a Finapres-like device result in tighter reactivity data; thus smaller sample sizes can be employed with this instrumentation.