초록 미리보기

Background: Orthostatic hypotension (OH) is caused by autonomic nervous dysfunction that compromises cerebral blood flow regulation resulting in fainting. Conventionally, OH is diagnosed as orthostatic BP fall in lying-to standing or tilt-table test.
Objectives: We investigated that near-infrared spectroscopy (NIRS) measuring cerebral autoregulation (CA) was an effective tool to diagnose OH.
Methods: We investigated 179 volunteers, 19 patients with OH (OH-BP) diagnosed as supine-to-stand fall in SBP ≥20 mmHg or DBP ≥10 mmHg, 41 patients with OH symptom (OH-Sx) categorized by using OH symptom assessment scale over 4 without diagnostic orthostatic BP change, and 119 healthy controls (HC) without any CA problems. A continuous-wave NIRS system (NIRSIT, OBELAB Inc.) was used to measure total hemoglobin concentration (HbT) changes in the forehead at a sampling frequency of 8.13 Hz during 2-min squat followed by standing for 9min. The changes were averaged and merged in two channels (i.e. left and right), then the time differential of HbT (dHbT/dt: DHbT) was extracted. CA was evaluated by measuring the peak time (PT) of the minimum and maximum value of DHbT oscillation during the squat-to-stand transition. The groups were compared using ANOVA, Kruskal-Wallis, and post-hoc testing (p<0.05).
Results: At the baseline, the age in OH-BP group was slightly higher, but not significant (p=0.065). The mean SBP, DBP, and HR did not show significant difference between groups. The maximum LPT was significantly longer in OH-BP group (p=0.019). Moreover, the maximum RPT were significantly longer in both OH-Sx and OH-BP groups than HC group (p=0.002). Minimum LPT and RPT were similar in all groups.
Conclusions: The subjects with orthostatic BP fall showed delayed maximum PT when measured with NIRS.  The subjects with orthostatic hypotension symptoms also had slightly delayed maximum PT even when there were no definitive orthostatic BP falls. This result suggests the possibility of using NIRS not only as a diagnostic tool but also as an effective method to  characterize individual CA.