Coupling of Blood Pressure and Subarachnoid Space Oscillations at Cardiac Frequency Evoked by Handgrip and Cold Tests: A Bispectral Analysis

Abstract

The aim of the study was to assess blood pressure–subarachnoid space (BP–SAS) width coupling properties using time–frequency bispectral analysis based on wavelet transforms during handgrip and cold tests. The experiments were performed on a group of 16 healthy subjects (F/M; 7/9) of the mean age 27.2 ± 6.8 years and body mass index of 23.8 ± 4.1 kg/m2. The sequence of challenges was first handgrip and then cold test. The handgrip challenge consisted of a 2-min strain, indicated by oral communication from the investigator, at 30% of maximum strength. The cold test consisted of 2 min of hand immersion to approximately wrist level in cold water of 4 °C, verified by a digital thermometer. Each test was preceded by 10 min at baseline and was followed by 10-min recovery recordings. BP and SAS were recorded simultaneously. Three 2-min stages of the procedure, baseline, test, and recovery, were analyzed. We found that BP–SAS coupling was present only at cardiac frequency, while at respiratory frequency both oscillators were uncoupled. Handgrip and cold test failed to affect BP–SAS cardiac–respiratory coupling. We showed similar handgrip and cold test cardiac bispectral coupling for individual subjects. Further studies are required to establish whether the observed intersubject variability concerning the BP–SAS coupling at cardiac frequency has any potential clinical predictive value.