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Evaluation of a noninvasive blood glucose monitoring device for critically ill patients


The purpose of this study was to evaluate the feasibility of the NBM device (OrSense Ltd) for noninvasive continuous glucose monitoring in critically ill patients. Critically ill patients frequently experience abnormalities in carbohydrate metabolism and a severe insulin resistance state. Hyperglycemia is a negative predictor of outcome in these patients, as high blood glucose (BG) values are associated with an increased risk of morbidity and mortality. Current BG monitoring methods do not provide the continuous glucose monitoring needed to implement tight glucose control protocols.


The NBM uses a sensor shaped like a ring, placed on the base of thumb. Red/near-infrared occlusion spectroscopy detects and analyzes BG and hemoglobin concentrations. A study was conducted on 14 patients (seven females, seven males, ages 34–92 years) in the ICU of the Rabin Medical Center. The NBM probe performed noninvasive continuous glucose monitoring for up to 24 hours, with readings every 10 minutes. There were a total of 22 sessions, with two excluded due to insufficient calibration. NBM results were compared with arterial blood samples taken through an arterial line every 30–60 minutes and were analyzed with a blood gas machine (ABL 700; Radiometer). In all sessions there was good patient compliance and no adverse effects were identified.


A prospective analysis based on a uniform model with personal calibration was performed on the NBM readings, for a total of 195 paired data points. The calibration phase lasted 3 hours utilizing reference BG values taken at t0+0:30, t0+1:30, t0+2:30, and t0+3:30. The reference BG range was 62–369 mg/dl. The median relative absolute error was 7.6%. A Clarke error grid analysis showed that 95.9% of the measurements fell within zones A (66.7%) and B (29.2%). Furthermore, the NBM and ABL 700 showed comparable estimates for the average percentage of time in hypoglycemia (8% ABL 700, 11% NBM), euglycemia (25% ABL 700, 26% NBM), and hyperglycemia (49% ABL 700, 57% NBM).


This study indicates the potential use of the noninvasive NBM as a device for continual, accurate, safe, and easy-to-use BG evaluation for the ICU. Consequently, it will improve patient care and survival, as well as reducing staff workload. The device has the promise for trend analysis, hypoglycemia detection and closed-loop systems enabling automatic glycemic control.

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Amir, O., Dvir, D., Grunberg, B. et al. Evaluation of a noninvasive blood glucose monitoring device for critically ill patients. Crit Care 12 (Suppl 2), P164 (2008).

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