Temperature-dependent Physio-psychological Changes by Footbath-Changes in electroencephalogram, cerebral circulation, R-R variability and comfort- / 日本温泉気候物理医学会雑誌

ABSTRACT

We studied temperature-dependent effects of the footbath on heart rate variability, EEG (F3, F4, P3, P4 of 10/20 international method), cerebral circulation, and subjective comfort, using electrocardiography (ECG), electroencephalography (EEG), near-infrared spectroscopy (NIRS), transcranial Doppler (TCD) and face scale. Subjects were 14 healthy adult women (32±6 years old) who took 3 types of footbath (10cm below the knee at 38°C, 40°C, and 42°C) and the control sitting position without footbath in a randomized sequence after providing written informed consent. Their ECG, EEG, NIRS on the forehead, and TCD findings for the middle cerebral artery were monitored for 50min including a 30min footbath. Subjective changes were monitored every 5min using the face scale. LF (low frequency; 0.04-0.15Hz) and HF (high frequency; 0.15-0.4Hz) components and Lorenz plots parameters were obtained from ECG R-R variability. EEG power and EEG right-left coherence were also calculated.<br>At 42°C footbath, total hemoglobin (Hb) concentration of the forehead, LF/HF ratio, Pulsatility Index (PI a marker of intracranial circulation and intracranial pressure obtained from TCD), and parietal β₁ wave power increased significantly. HF power and EEG coherence of θ and α₁ wave of the parietal and frontal leads decreased significantly with decline of comfort. At 40°C, cerebral circulation, LF/HF and PI changed less, but EEG power of the frontal α₁ and α₂, and parietal β₁ waves increased significantly after the cessation of footbath with simultaneous increase of comfort. At 38°C, transient but significant decrease of PI value after footbath was associated with significant increase of EEG power of the frontal θ and parietal α₂ waves after footbath. Parameters having statistically significant correlation with subjective comfort were HF power, Lorenz plots parameters, EEG power and coherence, and frontal Oxy Hb (r=0.150-0.231, p<0.0001 by Spearman's method). The EEG power of frontal α₁ waves had the largest correlation coefficient with subjective comfort (r=0.231, p<0.0001).<br>It was assumed that temperature-dependent changes of autonomic nervous activity and cerebral circulation caused changes of EEG and comfort during footbath. It was indicated that frontal α₁ wave power of EEG and Lorenz plots parameters obtained from R-R variability may be usable as indices of comfort in hot bathing.