Exercise As A Tool For Evaluation Of A Novel Subcutaneous Lactate Monitor

BACKGROUND: Lactate levels are commonly used as an indirect measure to assess metabolic stress both in exercise (e.g., anaerobic threshold and exercise intensity) and clinical conditions like sepsis. The current method for measuring blood lactate does not meet the need in clinical settings. Multiple blood draws and long processing preclude timely decision-making in clinical practice. A minimally invasive, blood free, continuous lactate monitor can improve clinical decisions and patient care. PURPOSE: To evaluate continuous lactate measurements of a novel enzymatic, Continuous Lactate Monitor (CLM), that was developed in our laboratory, during incremental cycling exercise challenges. METHODS: Five healthy individuals 18-45 y/o (3 males, 2 females) participated in the study. Two CLM devices were inserted subcutaneously in the lower back flank an hour before the exercise challenge. Each exercise challenge consisted of a 12-minute warm up and up to 7, 4-min incremental workload bouts separated by rest intervals. Continuous lactate measures obtained from CLM were compared with commercial lactate analyzer (Abbott iSTAT) measures taken at 12 time points from venous blood, drawn from the antecubital vein: before, during exercise, and up to 120 minutes post exercise. Area under the curve (AUC), and delay time were calculated to compare the CLM readings with blood lactate. RESULTS: Average blood lactate increased from 1.02 to 16.21 mM/L. Ratio of AUC derived from CLM to blood lactate was 1.09 (1.01-1.22). Average difference between CLM and blood lactate, with linear interpolation between blood lactate measurement, was 1.4 mM/L (0.878-2.37). At the lower levels of lactate (baseline), CLM sensitivity was lower. Average delay time between CLM readings and blood lactate was 6.16 minutes (3.70-11.21). CONCLUSIONS: The newly developed CLM has shown to be a promising tool to continuously measure lactate in a minimally invasive fashion. Results indicate the CLM can provide needed trends in lactate over time. Such a device may be used in the future to improve treatment in clinical conditions such as sepsis, assess the response to endurance exercise in both clinical and athletic settings, and guide exercise prescriptions. Supported by PERC Systems Biology. *N.D. and J.W. equal contribution