Date of Award
Master of Science in Biomedical Engineering - (M.S.)
Biomedical Engineering Committee
Ronald H. Rockland
Stanley S. Reisman
Karen S. Quigley
Although numerous studies evaluate baroreflex response as part of their research protocol, only one was identified as having evaluated continuous baroreceptor response as part of a 70° head-up tilt. It was done by Youde et al.  and was limited in that it evaluated only sequences of three beats for lag 0. The limitations of the Youde study  are not present in this thesis.
The data for this thesis came from a 70° head-up tilt study performed on chronic fatigue syndrome subjects by LaManca et al.  at the East Orange VA Medical Center. Baroreflex was not evaluated as part of the LaManca study. The goal of this thesis was to determine the utility of using the baroreflex sensitivity index (BRSI) on chronic fatigue syndrome subjects as a marker to discriminate between subject populations. Five groups are studied; five chronic fatigue syndrome (CFS), five chronic fatigue syndrome with postural orthostatic tachycardia syndrome (CFS-POTS), five chronic fatigue syndrome with fibromyalgia (CFS-FM), five control with postural orthostatic tachycardia syndrome (CON-POTS) and five control (CON).
The sequence method was used to assess baroreflex function. Comparative time analyses were done of weighted BRSI values between groups as well as between lags within groups. Baroreflex effectiveness index, BEI, was also evaluated along with the total number of ramps and sequences within and between groups.
Comparative time analysis provided a graphical representation of the behavior of the baroreflex during head-up tilt. Spikes in BRSI in the transitions between baseline and tilt and again between tilt and recovery were most noticeable for CFS-FM followed by CON-POTS and CFS-POTS. The CFS and CON groups were surprisingly similar in their behavior throughout the tilt. Differences between CON and CFS became graphically more apparent when evaluating BRSI by lag and calculating the percent change in sequences by lag. Slope of the weighted average for BRSI was calculated over a moving window of two-minute intervals. Based on this graph, slope does not appear to indicate a large difference between subject populations.
Evaluation of the total number of ramps and sequences by group for each lag indicated that the most efficient use of ramps was seen in lag 0 for all groups. The number of sequences tapered off dramatically in lags 1 and 2 regardless of the availability of ramps. The percent decrease in the number of sequences between lags for each group was calculated. The two most consistent groups in the number of sequences generated from the available ramps across all lags are CON and CFS-FM. The least consistent group is CFS.
The utilization of comparative time analysis to evaluate BRSI is an unexplored area of baroreflex research. Based on the graphical results of this thesis the idea appears to have merit.
Donnelly, Diane L., "Study of baroreceptor sensitivity index in chronic fatigue syndrome" (2003). Theses. 643.