BARORECEPTOR SENSITIVITY RESPONSE TO PHASE-IV OF THE VALSALVA MANEUVER IN SPINAL-CORD INJURY

Due to the increased prevalence of ischemic heart disease and hyperten sion reported in individuals with chronic spinal cord injury (SCI), we investigated whether subjects with low level SCI (paraplegia), withou t apparent evidence of coronary artery disease, exhibit normal barorec eptor and autonomic function. Eighteen males participated in this stud y: seven normotensive with paraplegia, five hypertensive with parapleg ia and six normotensive non-SCI controls. The Valsalva maneuver was pe rformed by maintaining a pressure of 40 mmHg over 15 s and R-R interva ls (RRI) and arterial blood pressure were measured continuously. Phase IV of the Valsalva maneuver was determined by linear regression analy sis between RRI and systolic pressure, with a final slope calculated. The power spectra for RRI and blood pressure variability parameters we re also analyzed, in addition to the index a, a frequency domain estim ate of the overall gain in baroreceptor control of the RRI-arterial bl ood pressure. The normotensive subjects with paraplegia were found to have an impaired baroreceptor response when compared with age-matched, non-SCI controls. In addition, the levels of both the low frequency a nd high frequency spectral components of RRI and the index a were redu ced in these individuals at rest. These cumulative findings strongly s uggest that the integrity of the sinoaortic baroreceptors, as well as efferent parasympathetic function, may be compromised in otherwise app arently healthy individuals with chronic paraplegia. (C) 1998 Lippinco tt-Raven Publishers.