Accuracy and reliability of continuous glucose monitoring in individuals with type 1 diabetes during recreational diving

Continuous Glucose Monitoring and Recreational Scuba Diving in Type 1 Diabetes: Head-to-Head Comparison Between Free Style Libre 3 and Dexcom G7 Performance

Background: Scuba diving was previously excluded because of hypoglycemic risks for patients with type 1 diabetes mellitus(T1DM). Specific eligibility criteria and a safety protocol have been defined, whereas continuous glucose monitoring (CGM) systems have enhanced diabetes management. This study aims to assess the feasibility and accuracy of CGM Dexcom G7 and Free Style Libre 3 in a setting of repetitive scuba diving in T1DM, exploring the possibility of nonadjunctive use. Material and Methods: The study was conducted during an event of Diabete Sommerso® association in 2023. Participants followed a safety protocol, with capillary glucose as reference standard (Beurer GL50Evo). Sensors' accuracy was evaluated through median and mean absolute relative difference (MeARD, MARD) and surveillance error grid (SEG). Data distribution and correlation were estimated by Spearman test and Bland-Altman plots. The ability of sensors to identify hypoglycemia was assessed by contingency tables. Results: Data from 202 dives of 13 patients were collected. The overall MARD was 31% (Dexcom G7) and 14.2% (Free Style Libre 3) and MeARD was 19.7% and 11.6%, respectively. Free Style Libre 3 exhibited better accuracy in normoglycemic and hyperglycemic ranges. SEG analysis showed 82.1% (Dexcom G7) and 97.4% (Free Style Libre 3) data on no-risk zone. Free Style Libre 3 better performed on hypoglycemia identification (diagnostic odds ratio of 254.10 vs. 58.95). Neither of the sensors reached the MARD for nonadjunctive use. Conclusions: The study reveals Free Style Libre 3 superior accuracy compared with Dexcom G7 in a setting of repetitive scuba diving in T1DM, except for hypoglycemic range. Both sensors fail to achieve accuracy for nonadjunctive use. Capillary tests remain crucial for safe dive planning, and sensor data should be interpreted cautiously. We suggest exploring additional factors potentially influencing sensor performance.

Practical aspects of diabetes technology use: Continuous glucose monitors, insulin pumps, and automated insulin delivery systems

There have been tremendous advances in diabetes technology in the last decade. Continuous glucose monitors (CGM), insulin pumps, and automated insulin delivery (AID) systems aim to improve glycemic control while simultaneously decreasing the burden of diabetes management. Although diabetes technologies have been shown to decrease both hypoglycemia and hyperglycemia and to improve health-related quality of life in individuals with type 1 diabetes, the impact of these devices in individuals with cystic fibrosis-related diabetes (CFRD) is less clear. There are unique aspects of CFRD, including the different underlying pathophysiology and unique lived health care experience and comorbidities, that likely affect the use, efficacy, and uptake of diabetes technology in this population. Small studies suggest that CGM is accurate and may be helpful in guiding insulin therapy for individuals with CFRD. Insulin pump use has been linked to improvements in lean body mass and hemoglobin A1c among adults with CFRD. A recent pilot study highlighted the promise of AID systems in this population. This article provides an overview of practical aspects of diabetes technology use and device limitations that clinicians must be aware of in caring for individuals with CF and CFRD. Cost and limited insurance coverage remain significant barriers to wider implementation of diabetes technology use among patients with CFRD. Future studies exploring strategies to improve patient and CF provider education about these devices and studies showing the effectiveness of these technologies on health and patient-reported outcomes may lead to improved insurance coverage and increased rates of uptake and sustained use of these technologies in the CFRD community.

Non-invasive and minimally invasive glucose monitoring devices: a systematic review and meta-analysis on diagnostic accuracy of hypoglycaemia detection

BACKGROUND

The use of minimally and non-invasive monitoring systems (including continuous glucose monitoring) has increased rapidly over recent years. Up to now, it remains unclear how accurate devices can detect hypoglycaemic episodes. In this systematic review and meta-analysis, we assessed the diagnostic accuracy of minimally and non-invasive hypoglycaemia detection in comparison to capillary or venous blood glucose in patients with type 1 or type 2 diabetes.

METHODS

Clinical Trials.gov, Cochrane Library, Embase, PubMed, ProQuest, Scopus and Web of Science were systematically searched. Two authors independently screened the articles, extracted data using a standardised extraction form and assessed methodological quality using a review-tailored quality assessment tool for diagnostic accuracy studies (QUADAS-2). The diagnostic accuracy of hypoglycaemia detection was analysed via meta-analysis using a bivariate random effects model and meta-regression with regard to pre-specified covariates.

RESULTS

We identified 3416 nonduplicate articles. Finally, 15 studies with a total of 733 patients were included. Different thresholds for hypoglycaemia detection ranging from 40 to 100 mg/dl were used. Pooled analysis revealed a mean sensitivity of 69.3% [95% CI: 56.8 to 79.4] and a mean specificity of 93.3% [95% CI: 88.2 to 96.3]. Meta-regression analyses showed a better hypoglycaemia detection in studies indicating a higher overall accuracy, whereas year of publication did not significantly influence diagnostic accuracy. An additional analysis shows the absence of evidence for a better performance of the most recent generation of devices.

CONCLUSION

Overall, the present data suggest that minimally and non-invasive monitoring systems are not sufficiently accurate for detecting hypoglycaemia in routine use.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2018 CRD42018104812.

A Comprehensive Review of Continuous Glucose Monitoring Accuracy during Exercise Periods

Continuous Glucose Monitoring (CGM) has been a springboard of new diabetes management technologies such as integrated sensor-pump systems, the artificial pancreas, and more recently, smart pens. It also allows patients to make better informed decisions compared to a few measurements per day from a glucometer. However, CGM accuracy is reportedly affected during exercise periods, which can impact the effectiveness of CGM-based treatments. In this review, several studies that used CGM during exercise periods are scrutinized. An extensive literature review of clinical trials including exercise and CGM in type 1 diabetes was conducted. The gathered data were critically analysed, especially the Mean Absolute Relative Difference (MARD), as the main metric of glucose accuracy. Most papers did not provide accuracy metrics that differentiated between exercise and rest (non-exercise) periods, which hindered comparative data analysis. Nevertheless, the statistic results confirmed that CGM during exercise periods is less accurate.

The current use of wearable sensors to enhance safety and performance in breath-hold diving: A systematic review

INTRODUCTION

Measuring physiological parameters at depth is an emergent challenge for athletic training, diver's safety and biomedical research. Recent advances in wearable sensor technology made this challenge affordable; however, its impact on breath-hold diving has never been comprehensively discussed.

METHODS

We performed a systematic review of the literature in order to assess what types of sensors are available or suitable for human breath-hold diving, within the two-fold perspective of safety and athletic performance.

RESULTS

In the 52 studies identified, sensed physiological variables were: electrocardiogram, body temperature, blood pressure, peripheral oxygen saturation, interstitial glucose concentration, impedance cardiography, heart rate, body segment inertia and orientation.

CONCLUSIONS

Limits and potential of each technology are separately reviewed. Inertial sensor technology and transmission pulse oximetry could produce the greatest impact on breath-hold diving performances in the future.

Continuous Glucose Monitoring Diving and Diabetes: An Update of the Swedish Recommendations

Divers travel to different countries to explore various diving sites worldwide. In 2005, the Divers Alert Network (DAN) published their guidelines for recreational diving and diabetes mellitus. However, although years have passed, there is still no consensus in the form of international guidelines on diabetes and diving. Large differences are noted with regard to the regulations in different countries. Furthermore, the diabetes technology has evolved rapidly and is not reflected in current international guidelines. This is potentially both a medical and an insurance problem for a diver with diabetes. We present a short summary of the recently updated Swedish recommendations for recreational divers with type 1 diabetes mellitus, focusing on the use of continuous glucose monitoring and continuous subcutaneous insulin infusion during such circumstances.

Monitoring of Pediatric Type 1 Diabetes

Regular self-monitoring of blood glucose levels, and ketones when indicated, is an essential component of type 1 diabetes (T1D) management. Although fingerstick blood glucose monitoring has been the standard of care for decades, ongoing rapid technological developments have resulted in increasingly widespread use of continuous glucose monitoring (CGM). This article reviews recommendations for self-monitoring of glucose and ketones in pediatric T1D with particular emphasis on CGM and factors that impact the accuracy and real-world use of this technology.

Into the deep blue sea: A review of the safety of recreational diving in people with diabetes mellitus

People with diabetes, particularly those being insulin treated, have been for many years considered ineligible for diving, because of the high risk of adverse events. Blood glucose levels tend to decline during diving, probably because of changes in insulin requirements and resistance, due to increased physical activity and effects of hyperbaric environment on glucose tolerance. Strict adherence to safety protocols, in conjunction with optimal physical status, lack of diabetic complications (especially impaired awareness of hypoglycaemia) and satisfactory baseline glycaemic control, seem to minimise the risk of complications during diving. The integration of modern technology into diabetes management, providing potential for underwater continuous glucose monitoring, can be useful in optimising metabolic control before, during and after diving. Despite the significant progress been made on safety issues, there is still a need to implement the relevant recommendations into divers' everyday practice. Existing evidence is mainly derived from small studies and there is a wide heterogeneity in terms of study designs and explored outcomes, rendering the extraction of definitive conclusions challenging. The aim of this review is to present and critically evaluate available evidence, use of technology, and gaps in existing knowledge that deserve further evaluation by future studies.

Impact of a sports project centered on scuba diving for adolescents with type 1 diabetes mellitus: New guidelines for adolescent recreational diving, a modification of the French regulations

BACKGROUND

Recreational scuba diving has been authorized for type 1 diabetics over 18 years old - the age of majority in France - since 2004, but it remained forbidden for younger diabetics by the French underwater federation (FFESSM). Here, we present a study to evaluate: - the conditions under which diving could be authorized for 14- to 18 year olds with type 1 diabetes; - the value of continuous glucose monitoring (CGM) while diving. A secondary objective was to monitor the impact of diving on the teenagers' quality of life.

SUBJECT AND METHODS

Sixteen adolescents (14-17.5 years old) were included. Diabetes was known for 6 years (range, 1-14) and Hb1Ac was 9.0% (range, 7.7-11.9). The study was conducted in Mayotte with both capillary glycemia (CG) and CGM measurements taken during five dives.

RESULTS

The average CG prior to diving was 283mg/dL and decreased by 75±76mg/dL during the dive. No hypoglycemia occurred during the dives and four episodes occurred after. Glycemia variations during dives and for the overall duration of the study were greater than for adults, most likely due to the general adolescent behavior, notably regarding diet and diabetes management. CGM was greatly appreciated by the adolescents. They had an overall satisfactory quality of life. No significant variations were observed during the entire course of the study.

CONCLUSIONS

Although in need of further studies, these preliminary results show that CGM can be used while diving. CGM records show a continuous decrease of glycemia during dives. Based on these results, the French underwater federation has now authorized diving for adolescent type 1 diabetics following a specific diving protocol that includes HbA1c<8.5%, autonomous management of diabetes by the adolescent, reduction of insulin doses, and target glycemia prior to the dive>250mg/dL.

Diabetic Patients Who are Amateur Divers

Diabetes is an “epidemic of the 21st century” and it is estimated that in 2011 6.7% of Poland’s population suffered from diabetes, one quarter of which was unaware of the disease. Such a high prevalence of diabetes mellitus results in an increasing number of physicians being confronted with the problem of qualifying patient with diabetes to partake in amateur sports, including diving. This publication presents the most important information concerning risk assessment, admission of diabetic patients to amateur diving and some proposed protocols of management before and during sport practice.

Glucose changes and working memory in individuals with type 1 diabetes during air pressure changes simulating skydiving

BACKGROUND

Several countries restrict individuals with type 1 diabetes mellitus (T1DM) from skydiving because of concerns over possible alterations in consciousness. To our knowledge, glucose levels and working memory in individuals with T1DM during skydiving have not been assessed earlier. The objective of this study was to investigate changes in glucose levels and working memory in selected subjects with T1DM compared with control subjects without diabetes mellitus (DM) during ambient air pressure changes as those anticipated during standard skydiving.

SUBJECTS AND METHODS

Six subjects with T1DM and six controls were included. Using a hypobaric chamber, the ambient air pressure was changed to simulate a standard skydive from 4,000 m (13,000 feet) above mean sea level. The procedure was repeated six times to mimic a day of skydiving activity with a median of 8.7 h/day (5(th), 95(th) percentile: 8.1, 9.8 h). All subjects carried a continuous glucose monitor (CGM). Capillary glucose tests were taken in order to calibrate the CGM. Hemoglobin oxygen saturation, heart rate, and working memory, evaluated through digit span, were monitored regularly.

RESULTS

No subject experienced documented symptomatic hypoglycemia with impaired working memory during the simulations. One asymptomatic hypoglycemia episode with a plasma glucose level of <3.9 mmol/L was recorded in a subject with T1DM, with a corresponding CGM trend indicating declining glucose levels. Interstitial glucose levels of <3.9 mmol/L were recorded by CGM in three of the controls during the simulations. There were no significant differences in hemoglobin oxygen saturation, heart rate, or working memory between the T1DM patients and the controls.

CONCLUSIONS

This study of interstitial glucose levels and working memory could not show the activity-specific risk factor (i.e., repetitive rapid-onset hypobaric hypoxia exposures) to be a greater safety concern for selected subjects with T1DM compared with subjects without DM during a simulated day of skydiving. Further studies are needed to clarify the suitability of subjects with T1DM to participate in this air sport.

In-vitro performance of the Enlite Sensor in various glucose concentrations during hypobaric and hyperbaric conditions

BACKGROUND

There is a need for reliable methods of glucose measurement in different environmental conditions. The objective of this in vitro study was to evaluate the performance of the Enlite® Sensor when connected to either the iPro™ Continuous Glucose Monitor recording device or the Guardian® REAL-Time transmitting device, in hypobaric and hyperbaric conditions.

METHODS

Sixteen sensors connected to eight iPro devices and eight Guardian REAL-Time devices were immersed in three beakers containing separate glucose concentrations: 52, 88, and 207 mg/dl (2.9, 4.9, and 11.3 mmol/liter). Two different pressure tests were conducted: a hypobaric test, corresponding to maximum 18000 ft/5500 m height, and a hyperbaric test, corresponding to maximum 100 ft/30 m depth. The linearity of the sensor signals in the different conditions was evaluated.

RESULTS

The sensors worked continuously, and the sensor signals were collected without interruption at all pressures tested. When comparing the input signals for glucose (ISIGs) and the different glucose concentrations during altered pressure, linearity (R(2)) of 0.98 was found. During the hypobaric test, significant differences (p < .005) were seen when comparing the ISIGs during varying pressure at two of the glucose concentrations (52 and 207 mg/dl), whereas no difference was seen at the 88 mg/dl glucose concentration. During the hyperbaric test, no differences were found.

CONCLUSIONS

The Enlite Sensors connected to either the iPro or the Guardian REAL-Time device provided values continuously. In hyperbaric conditions, no significant differences were seen during changes in ambient pressure; however, during hypobaric conditions, the ISIG was significantly different in the low and high glucose concentrations.

Continuous glucose monitoring--a study of the Enlite sensor during hypo- and hyperbaric conditions

BACKGROUND

The performance and accuracy of the Enlite(™) (Medtronic, Inc., Northridge, CA) sensor may be affected by microbubble formation at the electrode surface during hypo- and hyperbaric conditions. The effects of acute pressure changes and of prewetting of sensors were investigated.

MATERIALS AND METHODS

On Day 1, 24 sensors were inserted on the right side of the abdomen and back in one healthy individual; 12 were prewetted with saline solution, and 12 were inserted dry. On Day 2, this procedure was repeated on the left side. All sensors were attached to an iPro continuous glucose monitoring (CGM) recorder. Hypobaric and hyperbaric tests were conducted in a pressure chamber, with each test lasting 105 min. Plasma glucose values were obtained at 5-min intervals with a HemoCue(®) (Ängelholm, Sweden) model 201 glucose analyzer for comparison with sensor glucose values.

RESULTS

Ninety percent of the CGM systems operated during the tests. The mean absolute relative difference was lower during hyperbaric than hypobaric conditions (6.7% vs. 14.9%, P<0.001). Sensor sensitivity was slightly decreased (P<0.05) during hypobaric but not during hyperbaric conditions. Clarke Error Grid Analysis showed that 100% of the values were found in the A+B region. No differences were found between prewetted and dry sensors.

CONCLUSIONS

The Enlite sensor performed adequately during acute pressure changes and was more accurate during hyperbaric than hypobaric conditions. Prewetting the sensors did not improve accuracy. Further studies on type 1 diabetes subjects are needed under various pressure conditions.

Continuous glucose monitoring system during physical exercise in adolescents with type 1 diabetes

AIM

Continuous glucose monitoring system (CGMS) provides detailed information on glucose fluctuations. The aim was to establish whether CGMS could be used during physical exercise and whether it detects more episodes of hypoglycaemia and hyperglycaemia than frequent blood glucose measurements.

METHODS

Adolescents with type 1 diabetes (12 girls and 47 boys) participated in three annual sports camps that lasted for 3-4 days and included different types of exercise: soccer, floorball + cross-country skiing and golf. During the study, blood glucose values, mean 8.7 ± 3.3 per day, were obtained with Hemocue in parallel with the CGMS.

RESULTS

Ninety-eight per cent of the participants used the sensor at all times during the camps. Eighty-seven per cent of the sensors gave adequate signals for 24 h and 66% for 48 h. Median durations of hypoglycaemia and hyperglycaemia were 1.7 h per day and 3.8 h per day, respectively. The CGMS identified significantly more episodes of hypoglycaemia (p < 0.005) and hyperglycaemia (p < 0.005) during the day and night than frequent blood glucose tests.

CONCLUSION

We demonstrate that, even during days that included episodic strenuous physical exercise, CGMS could provide useful information on glucose fluctuations during day and night, albeit with significant failure rates.