PLACEBO-CONTROLLED BIOFEEDBACK BLOOD-PRESSURE EFFECT IN HYPERTENSIVE HUMANS

The role of biofeedback in blood pressure control remains ill-defined because of nonspecific (placebo) effects, small study numbers, and the technical limitations of continuous pressure feedback. Clarification of its potential is awaited by those seeking a nonpharmacological appr oach to blood pressure control. This study examines the capability for systolic pressure lowering of 5 mmHg or more using continuous pressur e feedback in a statistical sample of untreated, well-characterized, m ildly hypertensive individuals. Subjects were randomized in a double-b lind study to active or placebo biofeedback. Placebo consisted of a mo dified contingency approach, using a partial disguise based on a digit al high pass filter with 15 elements. Blood pressure-lowering capabili ty was assessed during two laboratory sessions. Continuous visual feed back resulted in 11 of 28 subjects on active treatment and 12 of 28 on placebo treatment lowering their systolic pressure by 5 mm Hg or more (11 +/- 5.6 and 12 +/- 8.4 mm Hg, respectively; P=NS). Prestudy press ure was well-matched (153 +/- 9/97 +/- 4 and 154 +/- 8/98 +/- 4 mm Hg, respectively). An initial small difference in diurnal profile did not change. These findings indicate that among mildly hypertensive indivi duals, almost half can lower systolic pressure at will for short perio ds. This capability is independent of the real or placebo nature of th e feedback signal. We conclude that there is no specific short-term bi ofeedback pressure-lowering capability in hypertensive individuals. Fu rther exploration is needed to determine whether specific components o f the placebo effect can be delineated, whether personality characteri stics influence the response, and whether further biofeedback training can alter the outcome.