[Vasomotor reactivity throught the voluntary apnea test can be measured without calculating the apnea index].

Introduction: Vasomotor reactivity (VR) is the capability of the cerebral arterioles to dilate and to constrict in response to determined stimuli. Using transcranial doppler (TCD), there are various test to evaluate it, including the breath holding test. With this test, VR can be calculated two ways: using the increment percentage of the mean velocity with respect to the basal velocity (PIV) or by quantifying the apnea time to obtain what is call the breath holding index (PIV/apnea seconds). The objective of our study is to study the linear correlation between the PIV and the breath holding index.

Methods: This was an observational study performed in a neurology ambulatory setting. A total of 128 subjects, age 16 to 50 years old, were included. We assessed VR using the breath holding test described by Markus and Harrison on the middle cerebral artery. The linear correlation between the two quantitative variables was analysed using Pearson's correlation coefficient.

Results: Pearson's correlation coefficient between the PIV and the breath holding index was 0.75 for a significance level of p < 0.0001.

Conclusion: Given the good linear correlation between these two methods for calculating the VR using the breath holding test, we consider it is not necessary to calculate breath holding test time when using this test.