ICU glucose monitoring measured in plasma using mid-infrared spectroscopy

Introduction

There are increasing calls for a highly accurate, automated system to enable tight glycemic control and avoid hypoglycemia in an ICU setting. OptiScan Biomedical has developed a glucose monitor based on mid-infrared spectroscopy that draws blood samples (120 μl) and measures plasma glucose concentrations approximately every 15 minutes. The goal of this study was to validate the performance of the OptiScan model 5000 (OptiScanner) at different glycemic levels in a healthy diabetic patient population.

Methods

Eighteen people (14 males, age 44 (18 to 64) years, BMI 29.0 (21.9 to 37.5) kg/m²) with type 1 (n = 8) or type 2 (n = 10) diabetes were connected to an OptiScanner. Their blood glucose concentrations were kept in a euglycemic (75 to 180 mg/dl), hypoglycemic (<75 mg/dl) and hyperglycemic (>180 mg/dl) range by intravenous administrations of insulin and glucose. Each OptiScanner blood sample was automatically withdrawn from a forearm vein. Blood samples for reference measurements using the YSI 2300 were withdrawn from the same arm within 60 seconds of the OptiScanner draw and analyzed immediately. A total of 250 paired data points in each glucose range will be collected in this ongoing study.

Results

The aggregate data points (374 paired readings between the OptiScanner and the YSI 2300) were within ISO standard, with 98.9% of the glucose values within ± 20% above 75 mg/dl and ± 15 mg/dl below this value. A Clark Error Grid analysis showed a total of 369 points (98.7%) in zone A (Figure 1). Points outside A exceeded the A zone boundary by an average of 5.3% and a maximum of 8.7%. The total coefficient for variance was 5.7%. The total r² was 0.99.

Figure 1

Conclusions

These preliminary results show that the OptiScanner is highly accurate in a healthy diabetic population.