IS AUSCULTATION ADEQUATE TO ESTIMATE BLOOD PRESSURE RESPONSES RELATED TO BODY POSITION CHANGES?

Abstract

Abstract Objective: The auscultatory blood pressure (BP) measurement technique, relying on the K1 and K5 Korotkoff sounds, is the current reference to validate new devices in the standard sitting position. There are few data to tell whether it should also be used for device validation in other body positions, since the K1 and K5 sounds can be affected by changes in vascular tone. In this study, we recorded the BP responses to body position changes by the auscultatory method, and we compared them to data from simultaneous recordings by a volume-clamp method. Design and method: Systolic (SBP) and diastolic (DBP) were estimated on the left upper arm by two independent blinded observers, and on the ipsilateral middle finger by a volume-clamp device (Nexfin, BMEYE, The Netherlands) in the supine followed by the standing position, and in the standing followed by the supine position. The auscultatory readings were repeated if readings differed more than 4mmHg between the two observers. A first auscultation was performed before the position change, and a second one 150 s after the position change. Because volume-clamp measurements were not available during upper-arm cuff inflation, the mean of volume-clamp values in a 30 s window prior to auscultation onset were used for the analyses. Results: Sixty-seven participants, between 21 and 65 years old, participated in this study. As illustrated in the figure, volume-clamp reported a consistent mean DBP increase of 9.3 mmHg when moving from supine to sitting, and a consistent mean DBP decrease of 10.4 mmHg when moving from sitting to supine. These results agree with those previously reported using simultaneous invasive and volume-clamp measurements. On the contrary, auscultation detected no consistent body position-related change in the DBP readings. Neither auscultation nor volume-clamp detected consistent body position-related changes in SBP readings. Conclusions: Compared to volume-clamp, auscultation was not able to detect any consistent changes in BP during orthostatic challenge. Our study suggests that the use of Korotkoff sounds to estimate BP in body positions other than sitting and relaxed may not be appropriate.