Evaluation of a near-infrared automated blood glucose monitor for use in critical care settings

Introduction

Luminous Medical (Carlsbad, CA, USA) is developing an automated, patient-attached system that uses near-infrared spectroscopy to measure glucose in whole blood. The system under development will aid caregivers in achieving tight glycemic control in critical care patients. Luminous Medical conducted a pilot study to characterize system performance in terms of automated blood access and glucose measurement accuracy.

Methods

Four volunteers with type 2 diabetes (mean BMI = 32) participated in an IRB-approved study of the Luminous Medical Automated Glucose Monitor (AGM). Two subjects were enrolled for 24-hour sessions, and two for 48-hour sessions. Two AGM systems were used in the study. A standard peripheral intravenous catheter was placed in the subject's arm to provide venous access. The AGM was attached to the catheter via a sterile, patient-dedicated, disposable tubing set. The system was configured to automatically draw a blood sample through a flow cell integrated into the disposable set at 30-minute intervals. Near-infrared transmission spectra were collected as blood was drawn through the flow cell. After measurement, the system reversed flow to return the blood to the subject and to flush the circuit with saline. Glucose measurements were determined from collected spectra using partial least-squares regression applied in subject-out cross-validation. Simultaneous blood samples collected and analyzed with a YSI 2700 Select provided reference glucose values.

Results

The Luminous Medical AGM systems collected 283 blood glucose measurements during 144 hours of operation. The system operated with a single disposable set without interruption during each of the four sessions, infrequently requiring only minor operator interventions (such as slight adjustment of the arm position). Glucose values ranged from 75 to 340 mg/dl. Bland–Altman analysis showed good agreement between Luminous Medical AGM glucose measurements and paired reference values, with a mean difference of 4.15 mg/dl, 95% confidence limits of -18.8 to 10.5 mg/dl, and R² = 0.97.

Conclusion

Luminous Medical's AGM provides reliable access to peripheral venous blood samples in volunteers with type 2 diabetes, and accurately measures glucose in these samples. Luminous technology holds considerable promise for providing an improved critical care glucose monitoring solution over currently available methods.