The current perception thresholds vary between horizontal and 70 degrees tilt-up positions.
We investigated the influence of posture on current perception threshold (CPT). The subjects consisted of 20 healthy male volunteers (23-31 yr old). At both the horizontal and the 70 degrees tilt-up position (TUP), the CPTs (5, 250, and 2000 Hz) of the middle finger were determined by using the Neurometer CPT/C (Neuropteran, Baltimore, MD). Autonomic nervous activities were evaluated by heart rate variability (HRV) analysis and spontaneous baroreflex sensitivity analysis at the two postures previously mentioned. The three CPTs at the 70 degrees TUP were significantly lower than those at the horizontal posture (5 Hz, P < 0.05; 250 Hz, P < 0.001; 2000 Hz, P < 0.05). The changes in HRV and spontaneous baroreflex sensitivity at the 70 degrees TUP indicated decreasing parasympathetic tone. The CPTs of 5 and 250 Hz were significantly correlated with mean systolic blood pressure at the 70 degrees TUP. The CPT of 2000 Hz was significantly correlated with the 0.15-0.4 Hz component in HRV at both postures. The regression analysis of the difference of 5 Hz CPT with that of the mean systolic blood pressure showed a significant correlation (P < 0.001). To evaluate the clinical course of peripheral nerve disorders, the comparison of CPTs measured during the same posture is important. This suggests that CPTs must be measured at the horizontal posture.


CONCLUSIONS
Current perception thresholds at the 70 degrees tilt-up posture were significantly lower than those at the horizontal posture. When the compensatory mechanism for preserving blood pressure was emphasized, the current perception thresholds would have a relational connection to mean systolic blood pressure, similar to the concept of hypertension-induced hypoalgesia.
Department of Anesthesiology, Kumamoto University School of Medicine. Surgical Center, Kumamoto University Hospital, Japan. shimoda@kaiju.medic.kumamoto-u.ac.jp
O
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Shimoda
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Ikuta
D000328:Adult; D001794:Blood Pressure; D004562:Electrocardiography; D004568:Electrodiagnosis; D006801:Humans; D008297:Male; D009460:Neurologic Examination; D017288:Pain Threshold / Q000502:physiology*; D010465:Perception; D011187:Posture / Q000502:physiology*; D016683:Supine Position / Q000502:physiology