Sensitive detection of hemodynamic failure during orthostatic stress in patients with diabetic polyneuropathy using a mini laser Doppler blood flowmeter.

Autonomic dysfunction in diabetes is serious but often underestimated. The purpose of this study was to evaluate hemodynamics within the important initial phase just after standing, which cannot be evaluated by conventional instruments for orthostatic hypotension. Earlobe blood flow (EBF), which indirectly reflects the blood pressure response on standing, was evaluated using a mini laser Doppler flowmeter during standing from the sitting position in 58 healthy controls and 56 diabetic patients categorized as without (11), mild (27), and advanced diabetic polyneuropathy (18). The response area of the EBF waveform within 30 seconds after standing was calculated. An increased response area indicates poor recovery of EBF. Response area increased significantly with the degree of neuropathy (P < .001 for linear trend). Orthostatic hypotension was detected in two patients in the mild neuropathy group. The present approach may be sensitive and practical for detecting autonomic dysfunction not detected with the conventional orthostatic test.

Orthostatic response of cephalic blood flow using a mini laser Doppler blood flowmeter and hemodynamics of a new active standing test.

PURPOSE: Cephalic hemodynamic assessment is important in initial orthostatic hypotension. We sought to investigate cephalic blood flow (CBF) in the earlobe using a mini laser Doppler flowmeter (LDF) during orthostatic challenge. In addition, we clarified hemodynamic differences during a new active standing protocol using a footstool standing test (FST) with bending of the legs on the footstool in the sitting position to reduce the load of the squatting posture in the conventional squat standing test (SST). METHODS: Ten healthy men (21 ± 0.5 years) performed the SST after a 1 min squat and the FST after a 1 min load consisting of bending the legs on a footstool in the sitting position. Earlobe CBF, beat-to-beat arterial blood pressure (ABP), mean arterial blood pressure (MAP), and heart rate (HR) were recorded during each test. RESULTS: Earlobe CBF showed a transient fall synchronized with the ABP during each test. No significant differences in the recovery times (RTs) of CBF and MAP were observed during the SST (CBF 12.9 ± 0.6 s vs. MAP 12.1 ± 0.5 s, P = 0.313) and FST (CBF 10.6 ± 0.4 s vs. MAP 10.1 ± 0.8 s, P = 0.552). Although the CBF and ABP decreases were not different in each test, the HR increase was significantly lower with the FST (24 ± 2 bpm) than with the SST (31 ± 3 bpm, P < 0.005). CONCLUSIONS: Earlobe CBF reflects the compensatory ABP regulatory response during standing and is potentially useful for estimating the orthostatic ABP response indirectly. Furthermore, the FST is a low-load protocol that can be an effective protocol for a standing test of cardiac function.

Integrated laser Doppler blood flowmeter designed to enable wafer-level packaging.

The authors propose a new sensor structure for an integrated laser Doppler blood flowmeter that consists of two silicon cavities with a PD and laser diode inside each cavity. A silicon lid formed with a converging microlens completes the package. This structure, which was achieved using micromachining techniques, features reduced optical power loss in the sensor, resulting in its small size and significantly low power consumption. Measurements using a model tissue blood flow system confirmed that the new sensor had high linearity and a wide dynamic range for measuring tissue blood flow.