Sympathetic Neural Mechanisms Underlying Attended and Unattended Blood Pressure Measurement

Whether blood pressure (BP) values differ when BP is measured with or without the presence of a doctor (attended and unattended BP measurements) is controversial, and no information exists on whether and to what extent neurogenic mechanisms participate at the possible BP differences between these measurements. In this study, we assessed continuous beat-to-beat finger systolic BP and diastolic BP, heart rate, muscle, and skin sympathetic nerve traffic (microneurography) before and during BP measurement by an automatic device in the presence or absence of a doctor. This was done in 18 untreated mild-to-moderate essential hypertensive patients (age, 40.2±2.8 years, mean±SEM). During attended BP measurement, there was an increase in systolic BP, diastolic BP, heart rate, and skin sympathetic nerve traffic and a muscle sympathetic nerve traffic decrease, the peak changes being +5.3%,+8.4%,+9.4%,+30.9%, and −15.2%, respectively (P<0.05 for all). In contrast, during unattended BP measurement, systolic BP, diastolic BP, heart rate, and skin sympathetic nerve traffic were modestly, albeit in most instances significantly, reduced, whereas muscle sympathetic nerve traffic remained almost unchanged. During unattended BP measurement, peak systolic BP was 14.1 mm Hg lower, peak heart rate was 10.6 bpm lower, and peak skin sympathetic nerve traffic was 8.5 bursts/min lower than the peak values detected during attended BP measurement. Thus the cardiovascular and neural sympathetic responses to the alerting reaction elicited by BP measurement in the presence of a doctor are almost absent during unattended BP measurement, during which, if anything, a modest cardiovascular sympathoinhibition occurs. This has important implications for comparison of studies using these different BP measurement approaches as well as for decision concerning threshold and target BP values for treatment.