The Accuracy of Continuous Glucose Monitoring and Flash Glucose Monitoring During Aerobic Exercise in Type 1 Diabetes

Abstract

Continuous glucose monitoring (CGM) devices detect more hypo-and hyperglycemic events compared to self-monitoring of blood glucose (SMBG) 1 and are emerging as the standard of care for type 1 diabetes (T1D). 2 CGM devices are also shown to detect activity-related dysglycemia in youth with T1D. 3 However, the physiologic lag in equilibrium between CGM and SMBG of 5-15 minutes may cause a clinically important discrepancy during exercise. 4,5 It remains unclear whether CGM use during exercise suffices for glucose-management decisions. The data presented here examined the concurrent use of two real-time CGM (rtCGM), and one flash glucose monitor (FGM) compared with SMBG during aerobic exercise to determine how these devices could be used effectively to guide carbohydrate intake to avoid hypoglycemia. A male subject with T1D (age 40 years; diabetes duration 25 years; HbA 1c 6.5%) was studied after informed consent was obtained. He wore a hybrid closed loop (HCL) insulin delivery system (Medtronic 670G, Minneapolis, MN; rtCGM1), Dexcom G5® CGM (San Diego, CA; rtCGM2) and Abbott FreeStyle Libre (Chicago, IL; FGM). The FGM and rtCGM devices were inserted 24-48 hours pre-exercise. SMBG was performed using a Contour® Next Link glucose meter (Ascensia Diabetes Care, Parsippany, NJ, USA) according to manufacturer recommendations. The HCL system was placed in "exercise-target" mode 1 hour before, disconnected during, and reconnected immediately after exercise. Pre-exercise meals were consumed >4 hours before activity. The exercise consisted of 1 hour of moderate-intensity running for 13 sessions over two months. Carbohydrate gels were consumed to avoid hypoglycemia during exercise based on the subject's experiences. At exercise onset, glucose levels were higher with FGM (237 ± 45 mg/dL) versus rtCGM1 (198 ± 34 mg/dL), rtCGM2 (206 ± 35 mg/dL), and SMBG (215 ± 33 mg/dL) (all P < .05; Figure 1). SMBG values dropped rapidly during exercise from 215 ± 33 to 104 ± 23 mg/dL (P = .0001),

Comparing two treatment approaches for patients with type 1 diabetes during aerobic exercise: a randomised, crossover study

“…Blood lactate was measured using a lactate analyser (Lactate Pro 2, Arkray, Japan). Glucose levels were monitored directly using the FGM device, and also via capillary sampling (Abbott Optium glucose strips) to minimise any delay between the interstitial and blood glucose levels during physical activity [12]. Self-perceived rate of exertion (RPE) was also assessed every 15 minutes during the aerobic exercise, and immediately following the 6MWT using the Borg's RPE scale [17].…”

“…beta-blockers); or were currently using closed-loop insulin pump therapy. All potential participants were screened at the WRDS Clinic and upon recruitment were required to attend the clinic again 38-48 hours prior to the rst test session to have a Flash Glucose monitoring (FGM) device (Abbott Freestyle Libre, Chicago, IL) inserted to allow for continuous glucose monitoring [12]. All participants were able to wear the Freestyle Libre device for 14 days from the date of insertion.…”

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“…beta-blockers); or were currently using closed-loop insulin pump therapy. All potential participants were screened at the WRDS Clinic and upon recruitment were required to attend the clinic again 38-48 hours prior to the rst test session to have a Flash Glucose monitoring (FGM) device (Abbott Freestyle Libre, Chicago, IL) inserted to allow for continuous glucose monitoring [11]. All participants were able to wear the Freestyle Libre device for 14 days from the date of insertion.…”

“…Blood lactate was measured using a lactate analyser (Lactate Pro 2, Arkray, Japan). Glucose levels were monitored directly using the FGM device, and also via capillary sampling (Abbott Optium glucose strips) to minimise any delay between the interstitial and blood glucose levels during physical activity [11]. Self-perceived rate of exertion (RPE) was also assessed every 15 minutes during the aerobic exercise, and immediately following the 6MWT using the Borg's RPE scale [16].…”

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“…The patient performed one hour of moderate intensity running and monitored glucose values through the CGM systems and finger-stick measurements. All three of the CGM systems lagged behind finger-stick values when glucose values dropped during exercise with the largest difference in glucose levels noted in the first 30 min of exercise [32]. Additional studies have supported the finding that discrepancies between CGM and finger-stick values are greatest during exercise and return to previous accuracy within a couple hours after aerobic exercise [33].…”