A Reference-Less Time-Division-Duplex Transceiver IC for a 5-Fr 6-Electrode Renal Denervation Catheter in 0.18-µm 70-V BCDMOS.

This paper presents the first time-division-duplex transceiver IC for a 5-Fr 6-electrode renal denervation (RDN) catheter for treatment of resistant hypertension. Each IC encapsulated in a platinum electrode implements an RDN catheter with 37.5 % of diameter reduction, which enables minimally invasive surgery with reduced complications. The six electrodes sharing only four electrical wires perform packet communication with an external power control unit for independent operation and deliver the designated RF energy to the renal artery wall while measuring local temperature and impedance. Two 500- kHz 21-Vrms AC signals with ±35-V DC potentials are used as supplies to transfer up to 6-W RF ablation signal with 120-Vpp swing while maintaining the maximum DC supply voltages of the ICs less than the break-down voltage of 70 V. The proposed RDN IC fabricated in 0.18-µm HV BCDMOS occupies 2.1 mm2.

Assessment of cerebral autoregulation using continuous-wave near-infrared spectroscopy during squat-stand maneuvers in subjects with symptoms of orthostatic intolerance.

Orthostatic lightheadedness in healthy young adults often leads to syncope in severe cases. One suggested underlying mechanism of orthostatic lightheadedness is a drop in transient blood pressure (BP); however, a decrease in BP does not always lead to a drop in cerebral blood flow (CBF) due to cerebral autoregulation (CA). We present a direct assessment method of CA using a multichannel continuous-wave near-infrared spectroscopy (CW-NIRS) device that measures the temporal changes in oxy- and deoxy-hemoglobin concentrations in the prefrontal cortex. Twenty healthy young adults were recruited. During the experiment, continuous beat-to-beat BP and heart rate were simultaneously measured during repetitive squat-stand maneuvers. We introduce a new metric termed 'time-derivative hemodynamic model (DHbT)', which is the time-derivative of total-hemoglobin concentration change that reflects the changes of cerebral blood volume and CBF. Although the absolute levels and the variations of systolic and diastolic BPs and mean arterial pressure showed no significant difference between the two groups, the proposed model showed a distinct difference in slope variation and response time of DHbT between the subjects with frequent symptom of orthostatic intolerance and the healthy control subjects. Thus, these results clearly demonstrate the feasibility of using CW-NIRS devices as a CA performance assessment tool.