Reliability of the noninvasive sequence methods to estimate baroreflex function using the paradigm of brain death.

Background: Various techniques have been developed to estimate spontaneous baroreflex sensitivity noninvasively. However, in the EuroBaVar study it has been shown that they yield differing results.

Aim Of The Study: To investigate the reliability of these methods further we compared the results of the most common sequence techniques. We used the paradigm of brain death with the absence of any baroreflex function.

Methods: In a prospective study we recorded breathing pattern, ECG and continuous blood pressure in 10 consecutive brain dead subjects of a neurointensive care unit. EuroBaVar sequence techniques 12-18 (ST12-ST18) were applied to the data sets and the number of sequences compared.

Results: Techniques which are based on thresholds in terms of blood pressure or R-R interval changes yielded the least false positive results: technique ST12, ST13, and ST14 detected very few sequences, while ST18 detected no sequence at all. Techniques using a correlation threshold (ST15-ST17) found a high number.

Conclusion: This study demonstrates clearly that many of the sequence techniques used to estimate baroreflex sensitivity render false positive results in the unique paradigm of brain death. Thus, the method should be selected with regard to the biological signal and the pathophysiological background.