Accuracy of handheld blood glucose meters at high altitude

Above the Clouds with Diabetes: From Pathophysiological Considerations to Practical Recommendations for Safe Flights

Vasdeki, Dimitra, Georgios Tsamos, Kleoniki I. Athanasiadou, Vasiliki Michou, Evangelos Botsarakos, Michael Doumas, Kalliopi Kotsa, and Theocharis Koufakis. Above the clouds with diabetes: From pathophysiological considerations to practical recommendations for safe flights. High Alt Med Biol. 00:00-00, 2024. Background: The prevalence of diabetes mellitus has been following an increasing trend in the last decades, leading to a growing number of travelers with diabetes seeking pretravel advice from medical professionals. Methods: This narrative review summarizes the existing evidence on the intriguing association between diabetes and air travel, analyzes safety and certification protocols, and provides practical recommendations for the management of diabetes during flights. Results: During air travel, individuals with diabetes face challenges arising from inappropriate dietary options, restricted access to medications and healthcare services, disruption of medication dosing intervals, and exposure to hypobaric conditions in the airplane cabin. In addition, people with diabetes, especially those treated with insulin, have traditionally been considered ineligible to become professional pilots. However, this approach gradually changes and numerous countries are now implementing strict protocols to determine the eligibility of pilots with diabetes to operate flights. Conclusions: Given the increasing use of technology and new drugs in daily clinical practice, there is a need for further research in the field to shed light on existing knowledge gaps and ensure safe flights for people with diabetes.

People With Diabetes Using Insulin Flying Across Multiple Time Zones: Limitations and Opportunities for Diabetes Technologies

Increasingly, people with diabetes (PWD) are using wearable and other devices to support self-management. During air travel, there are 4 stakeholders involved in maximizing the safety of wireless devices for diabetes care used in flight: (1) manufacturers of the devices, (2) airlines, (3) the Transportation Security Administration, and (4) the U.S. Food and Drug Administration. These stakeholders have all developed technologies and policies that assist PWD who prepare for and take appropriate actions during long-haul flights. This article discusses the performance and use of 6 classes of specific wireless diabetes devices during an airplane flight, including the following: (1) blood glucose monitors, (2) continuous glucose monitors, (3) insulin pumps, (4) smart pens for dosing insulin injections, (5) advanced hybrid closed-loop systems, and (6) spinal cord stimulators for painful diabetic neuropathy. Through the policies and safeguards of the 4 stakeholders and the proper self-care measures that insulin-using PWD can take, it is possible to maintain safe glycemic levels on flights across multiple time zones.

UIAA Medical Commission Recommendations for Mountaineers, Hillwalkers, Trekkers, and Rock and Ice Climbers with Diabetes

Hillebrandt, David, Anil Gurtoo, Thomas Kupper, Paul Richards, Volker Schöffl, Pankaj Shah, Rianne van der Spek, Nikki Wallis, and Jim Milledge. UIAA Medical Commission recommendations for mountaineers, hillwalkers, trekkers, and rock and ice climbers with diabetes. High Alt Med Biol. 24: 110-126.-The object of this advice article is not only to give the diabetic mountaineer general guidance but also to inform his or her medical team of practical aspects of care that may not be standard for nonmountaineers. The guidelines are produced in seven sections. The first is an introduction to the guidelines, and the second is an introduction to this medical problem and is designed to be read and understood by diabetic patients and their companions. The third section is for use in an emergency in mountains. The fourth is for rock, ice, and competition climbers operating in a less remote environment. These initial sections are deliberately written in simple language. The fifth and sixth sections are written for clinicians and those with skills to read more technical information, and the seventh looks at modern technology and its pros and cons in diabetes management in a remote area. Sections One and Two could be laminated and carried when in the mountains, giving practical advice.

Performance of the Eversense versus the Free Style Libre Flash glucose monitor during exercise and normal daily activities in subjects with type 1 diabetes mellitus

INTRODUCTION

Accurate blood glucose measurements are important in persons with diabetes during normal daily activities (NDA), even more so during exercise. We aimed to investigate the performance of fluorescence sensor-based and glucose oxidase-based interstitial glucose measurement during (intensive) exercise and NDA.

RESEARCH DESIGN AND METHODS

Prospective, observational study in 23 persons with type 1 diabetes when mountain biking for 6 days, followed by 6 days of NDA. Readings of the Eversense (fluorescence-based continuous glucose monitoring (CGM); subcutaneously implanted) and of the Free Style Libre (FSL; glucose oxidase-based flash glucose monitoring (FGM); transcutaneously placed) were compared with capillary glucose levels (Free Style Libre Precision NeoPro strip (FSLCstrip)).

RESULTS

Mean average differences (MAD) and mean average relative differences (MARD) were significantly different when comparing exercise with NDA (reference FSLCstrip); Eversense MAD 25±19 vs 17±6 mg/dL (p<0.001); MARD 17±6 vs 13%±6% (p<0.01) and FSL MAD 32±17 vs 18±8 mg/dL (p<0.01); MARD 20±7 vs 12%±5% (p<0.001).When analyzing the data according to the Integrated Continuous Glucose Monitoring Approvals (class II-510(K) guidelines), the overall performance of interstitial glucose readings within 20% of the FSLCstrip during exercise compared with NDA was 69% vs 81% for the Eversense and 59% vs 83% for the FSL, respectively. Within 15% of the FSLCstrip was 59% vs 70% for the Eversense and 46% vs 71% for the FSL.

CONCLUSIONS

During exercise, both fluorescence and glucose oxidase-based interstitial glucose measurements (using Eversense and FSL sensors) were less accurate compared with measurements during NDA. Even when acknowledging the beneficial effects of CGM or FGM, users should be aware of the risk of diminished accuracy of interstitial glucose readings during (intensive) exercise.

Proof of Concept Study to Assess the Influence of Oxygen Partial Pressure in Capillary Blood on SMBG Measurements

BACKGROUND

Measurement results provided by blood glucose monitoring systems (BGMS) can be affected by various influencing factors. For some BGMS using glucose oxidase (GOx)-based test strips, one of these factors is the oxygen partial pressure (pO₂) of the applied blood sample. Because assessing the potential influence of pO₂ when measuring capillary blood samples is not straight-forward, we performed a proof of concept study.

METHOD

Influence of pO₂ was investigated for two GOx-based BGMS (BGMS A and B). Measurement results of the GOx-based BGMS were compared with measurement results from a pO₂-independent BGMS (BGMS C). A total of 119 samples from 60 subjects were measured, twice with BGMS C, then 6 times each with BGMS A and BGMS B or vice versa, and again twice with BGMS C. Immediately afterward, pO₂ was determined. Linear regression analysis based on relative differences between results from BGMS A or BGMS B and results from BGMS C was performed to estimate the degree of pO₂ influence.

RESULTS

The relative bias between the lowest and highest pO₂ values differed by 14.3% for BGMS A, indicating a pO₂ influence that might be clinically relevant, and by 9.7% for BGMS B, indicating that pO₂ influence may be too small to be reliably detected because of the BGMS' imprecision.

CONCLUSIONS

This proof of concept study showed that with the procedures used, a potentially clinically relevant influence of pO₂ in capillary blood samples on GOx-based BGMS could be detected. Further larger-scale studies are needed to verify this influence.

Diabetes-Related Knowledge of Polish National Mountain Leaders

Nabrdalik, Katarzyna, Hanna Kwiendacz, Monika Gubała, Kinga Tyrała, Mariusz Seweryn, Andrzej Tomasik, Tomasz Sawczyn, Michał Kukla, Władysław Grzeszczak, and Janusz Gumprecht. Diabetes-related knowledge of Polish national mountain leaders. High Alt Med Biol. 19:237-243, 2018.-Mountain trekking is a popular activity for patients with diabetes. In Poland, mountain leaders often accompany organized groups to ensure their safety during treks; we aimed to evaluate their competency in caring for diabetic clients by assessing their diabetes-related knowledge. This was a cross-sectional study among Polish, certified, active mountain leaders carried out by means of an anonymous, standardized 41-item questionnaire adapted from a study by Wee et al. It was distributed through e-mail to 500 leaders. A total of 106 (21.2%) mountain leaders completed the questionnaire (males 60.4%) with a mean (standard deviation [SD]) age of 38.6 (13.5) years. Their mean (SD) length of experience acting as a mountain leader was 11.9 (10.2) years. The average score was 72.4% of the maximum possible (29.7 of 41 points). Results varied significantly depending on gender (p = 0.006). The percentage of correct answers among questions in each section varied between 23.6% and 100%. The main sources of diabetes-related knowledge identified by respondents were members of their family and their friends who suffer from diabetes (33%). First aid courses were indicated as sources of information by only 12.6% of the informants. Results of the questionnaire revealed that respondents did have a reasonable level of diabetes-related knowledge. There were topics in which the respondents achieved lower than an average score, demonstrating a need for further education.

MANAGEMENT OF DIABETES DURING AIR TRAVEL: A SYSTEMATIC LITERATURE REVIEW OF CURRENT RECOMMENDATIONS AND THEIR SUPPORTING EVIDENCE

OBJECTIVE

Individuals with diabetes are increasingly seeking pretravel advice, but updated professional recommendations remain scant. We performed a systematic review on diabetes management during air travel to summarize current recommendations, assess supporting evidence, and identify areas of future research.

METHODS

A systematic review of the English literature on diabetes management during air travel was undertaken utilizing PubMed and MEDLINE. Publications regarding general travel advice; adjustment of insulin and noninsulin therapies; and the use of insulin pumps, glucometers and subcutaneous glucose sensors at altitude were included. Gathered information was used to create an updated summary of glucose-lowering medication adjustment during air travel.

RESULTS

Sixty-one publications were identified, most providing expert opinion and few offering primary data (47 expert opinion, 2 observational studies, 2 case reports, 10 device studies). General travel advice was uniform, with increasing attention to preflight security. Indications for oral antihyperglycemic therapy adjustments varied. There were few recommendations on contemporary agents and on nonhypoglycemic adverse events. There was little consensus on insulin adjustment protocols, many antedating current insulin formulations. Most publications advocated adjusting insulin pump time settings after arrival; however, there was disagreement on timing and rate adjustments. Glucometers and subcutaneous glucose sensors were reported to be less accurate at altitude, but not to an extent that would preclude their clinical use.

CONCLUSION

Recommendations for diabetes management during air travel vary significantly and are mostly based on expert opinion. Data from systematic investigation on glucose-lowering medication adjustment protocols may support the development of a future consensus statement.

ABBREVIATIONS

CSII = continuous subcutaneous insulin infusion (device) DPP-4 = dipeptidyl peptidase 4 EGA = error grid analysis GDH = glucose dehydrogenase GOX = glucose oxidase GLP1 = glucagon-like peptide-1 NPH = neutral protamine Hagedorn SGLT2 = sodium-glucose cotransporter-2.

Clinical review: the misreporting of logbook, download, and verbal self-measured blood glucose in adults and children with type I diabetes

Despite advances in technology, the frequent self-measurement of blood glucose (SMBG) remains fundamental to the management of 1 diabetes mellitus (T1DM). Once measured, SMBG results are routinely reported back to health professionals and other interested parties, either verbally, via a logbook, or electronically downloaded from a pump or meter. The misreporting of SMBG using various techniques represents a classic non-adherence behavior and carries with it both acute and chronic dangers. In addition, while this behavior appears very prevalent, many aspects remain largely unstudied. With this in mind, we aimed to summarize literature addressing the misreporting of SMBG in T1DM via a detailed literature search. This produced both recent and past literature. While most of these studies examined the prevalence of deliberate misreporting in a verbal or logbook context, others focused on the motivations behind this behavior, and alternative forms of misreporting, including deliberate manipulation of meters to produce inaccurate results and true technological errors. This timely review covers all aspects of misreporting and highlights multiple patient techniques, which are clearly adapting to advances in technology. We believe that further understanding and attention to this aspect of adherence may lead not only to improvements in glycemic control and safety, but also to the psychological well-being of those affected by type 1 diabetes.

Interferences and Limitations in Blood Glucose Self-Testing: An Overview of the Current Knowledge

In general, patients with diabetes performing self-monitoring of blood glucose (SMBG) can strongly rely on the accuracy of measurement results. However, various factors such as application errors, extreme environmental conditions, extreme hematocrit values, or medication interferences may potentially falsify blood glucose readings. Incorrect blood glucose readings may lead to treatment errors, for example, incorrect insulin dosing. Therefore, the diabetes team as well as the patients should be well informed about limitations in blood glucose testing. The aim of this publication is to review the current knowledge on limitations and interferences in blood glucose testing with the perspective of their clinical relevance.

Point-of-care devices for physiological measurements in field conditions. A smorgasbord of instruments and validation procedures

Point-of-care (POC) devices provide quick diagnostic results that increase the efficiency of patient care. Many POC devices are currently available to measure metabolites, blood gases, hormones, disease biomarkers or pathogens in samples as diverse as blood, urine, feces or exhaled breath. This diversity is potentially very useful for the comparative physiologist in field studies if proper validation studies are carried out to justify the accuracy of the devices in non-human species under different conditions. Our review presents an account of physiological parameters that can be monitored with POC devices and surveys the literature for suitable quantitative and statistical procedures for comparing POC measurements with reference "gold standard" procedures. We provide a set of quantitative tools and report on different correlation coefficients (Lin's Concordance Correlation Coefficient or the more widespread Pearson correlation coefficient), describe the graphical assessment of variation using Bland-Altman plots and discuss the difference between Model I and Model II regression procedures. We also report on three validation datasets for lactate, glucose and hemoglobin measurements in birds using the newly proposed procedures. We conclude the review with a haphazard account of future developments in the field, emphasizing the interest in lab-on-a-chip devices to carry out more complex experimental measurements than the ones currently available in POC devices.

Glucose intolerance associated with hypoxia in people living at high altitudes in the Tibetan highland

OBJECTIVES

To clarify the association between glucose intolerance and high altitudes (2900-4800 m) in a hypoxic environment in Tibetan highlanders and to verify the hypothesis that high altitude dwelling increases vulnerability to diabetes mellitus (DM) accelerated by lifestyle change or ageing.

DESIGN

Cross-sectional epidemiological study on Tibetan highlanders.

PARTICIPANTS

We enrolled 1258 participants aged 40-87 years. The rural population comprised farmers in Domkhar (altitude 2900-3800 m) and nomads in Haiyan (3000-3100 m), Ryuho (4400 m) and Changthang (4300-4800 m). Urban area participants were from Leh (3300 m) and Jiegu (3700 m).

MAIN OUTCOME MEASURE

Participants were classified into six glucose tolerance-based groups: DM, intermediate hyperglycaemia (IHG), normoglycaemia (NG), fasting DM, fasting IHG and fasting NG. Prevalence of glucose intolerance was compared in farmers, nomads and urban dwellers. Effects of dwelling at high altitude or hypoxia on glucose intolerance were analysed with the confounding factors of age, sex, obesity, lipids, haemoglobin, hypertension and lifestyle, using multiple logistic regression.

RESULTS

The prevalence of DM (fasting DM)/IHG (fasting IHG) was 8.9% (6.5%)/25.1% (12.7%), respectively, in all participants. This prevalence was higher in urban dwellers (9.5% (7.1%)/28.5% (11.7%)) and in farmers (8.5% (6.1%)/28.5% (18.3%)) compared with nomads (8.2% (5.7%)/15.7% (9.7%)) (p=0.0140/0.0001). Dwelling at high altitude was significantly associated with fasting IHG+fasting DM/fasting DM (ORs for >4500 and 3500-4499 m were 3.59/4.36 and 2.07/1.76 vs <3500 m, respectively). After adjusting for lifestyle change, hypoxaemia and polycythaemia were closely associated with glucose intolerance.

CONCLUSIONS

Socioeconomic factors, hypoxaemia and the effects of altitudes >3500 m play a major role in the high prevalence of glucose intolerance in highlanders. Tibetan highlanders may be vulnerable to glucose intolerance, with polycythaemia as a sign of poor hypoxic adaptation, accelerated by lifestyle change and ageing.

Cardiometabolic risk factors in native populations living at high altitudes

BACKGROUND

It is generally accepted that metabolic changes that take place in individuals exposed to high elevation are because of ambient hypoxia, which occurs as a consequence of a low total atmospheric pressure. The discovery of hypoxia inducible factor 1 (HIF1), a transcription factor, has been a breakthrough in the understanding of adaption to high altitudes.

OBJECTIVE

The purpose of the present review was to discuss specific epidemiological aspects of cardiovascular disease (CVD) risk factors and their mechanisms in vulnerable, understudied populations living at high altitudes.

RESULTS

Obesity prevalence has been inversely associated with elevation. HIF1 has been related to plasma leptin--a hormone secreted by adipose tissue that produces negative feedback on appetite--and inversely associated with obesity. Diverse factors, such as genetics, chronic hypoxia, diet and lifestyle behaviours, could have an influence on the high dyslipidaemia rates of high-altitude natives. Hypoxia could mediate the effects of altitude on human physiology, including lipid metabolism. Genetic studies suggest that dyslipidaemia could be related to the HIF1. Hypoxia inhibits oxidative phosphorylation and stimulates the oxygen signalling pathway through the HIF1. Low fasting glycaemia in individuals at high altitudes has been shown. An increased GLUT4 protein content in skeletal muscle in response to hypoxia has been reported and could be associated with lower glucose levels. Given the high prevalence of dyslipidaemia and the low prevalence of obesity and diabetes in these impoverished high-altitude communities, changes in lifestyle including decreased physical activity and the consumption of a more westernised diet would likely increase the prevalence of CVD related mortality.

CONCLUSIONS

Control over major CVD risk factors, when identified early, could be the key to reducing morbidity and mortality in patients with limited access to medical services such as Native populations.

Glucose homeostasis during short-term and prolonged exposure to high altitudes

Most of the literature related to high altitude medicine is devoted to the short-term effects of high-altitude exposure on human physiology. However, long-term effects of living at high altitudes may be more important in relation to human disease because more than 400 million people worldwide reside above 1500 m. Interestingly, individuals living at higher altitudes have a lower fasting glycemia and better glucose tolerance compared with those who live near sea level. There is also emerging evidence of the lower prevalence of both obesity and diabetes at higher altitudes. The mechanisms underlying improved glucose control at higher altitudes remain unclear. In this review, we present the most current evidence about glucose homeostasis in residents living above 1500 m and discuss possible mechanisms that could explain the lower fasting glycemia and lower prevalence of obesity and diabetes in this population. Understanding the mechanisms that regulate and maintain the lower fasting glycemia in individuals who live at higher altitudes could lead to new therapeutics for impaired glucose homeostasis.

Study of the effect of altitude on the measurement of glycated haemoglobin using point-of-care instruments

We measured the glycated haemoglobin (HbA1c) levels of a total of 24 non-diabetic volunteers and diabetic patients using a point-of-care (POC) analyser in three Cameroonian cities at different altitudes. Although 12 to 25% of duplicates had more than 0.5% (8 mmol/mol) difference across the sites, HbA1c values correlated significantly (r = 0.89-0.96). Further calibration studies against gold-standard measures are warranted.

Physical activity at altitude: challenges for people with diabetes: a review

BACKGROUND

A growing number of subjects with diabetes take part in physical activities at altitude such as skiing, climbing, and trekking. Exercise under conditions of hypobaric hypoxia poses some unique challenges on subjects with diabetes, and the presence of diabetes can complicate safe and successful participation in mountain activities. Among others, altitude can alter glucoregulation. Furthermore, cold temperatures and altitude can complicate accurate reading of glucose monitoring equipment and storage of insulin. These factors potentially lead to dangerous hyperglycemia or hypoglycemia. Over the last years, more information has become available on this subject.

PURPOSE

To provide an up-to-date overview of the pathophysiological changes during physical activity at altitude and the potential problems related to diabetes, including the use of (continuous) blood glucose monitors and insulin pumps. To propose practical recommendations for preparations and travel to altitude for subjects with diabetes.

DATA SOURCES AND SYNTHESIS

We researched PubMed, medical textbooks, and related Internet sites, and extracted human studies and data based on relevance for diabetes, exercise, and altitude.

LIMITATIONS

Given the paucity of controlled trials regarding diabetes and altitude, we composed a narrative review and filled in areas lacking diabetes-specific studies with data obtained from nondiabetic subjects.

CONCLUSIONS

Subjects with diabetes can take part in activities at high, and even extreme, altitude. However, careful assessment of diabetes-related complications, optimal preparation, and adequate knowledge of glycemic regulation at altitude and altitude-related complications is needed.

Impact of partial pressure of oxygen in blood samples on the performance of systems for self-monitoring of blood glucose

BACKGROUND

The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample.

MATERIALS AND METHODS

Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ≤45 mm Hg, approximately 70 mm Hg, and ≥150 mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70 mm Hg, which was considered to be similar to pO2 values in capillary blood samples, and the mean BG value at pO2 levels ≤45 mm Hg and ≥150 mm Hg were calculated.

RESULTS

The GOD systems showed mean relative differences between 11.8% and 44.5% at pO2 values ≤45 mm Hg and between -14.6% and -21.2% at pO2 values ≥150 mm Hg. For the GDH system, the mean relative differences were -0.3% and -0.2% at pO2 values ≤45 mm Hg and ≥150 mm Hg, respectively.

CONCLUSIONS

The magnitude of the pO2 impact on BG measurements seems to vary among the tested oxygen-sensitive GOD systems. The pO2 range in which oxygen-sensitive systems operate well should be provided in the product information.

The accuracy of a glucose-oxidase-based point-of-care glucometer in premature infants

OBJECTIVE

The purpose of this study was to evaluate the accuracy of a novel commercial glucose-oxidase (GO)-based glucometer in measuring glucose concentrations in arterial blood samples collected from premature infants.

PATIENTS AND METHODS

A commercial glucometer, which is a plasma separation GO-based glucometer, was employed to compare the accuracy of the commercial blood glucometer with that of a standard glucose analyser for monitoring blood glucose levels in premature infants. Arterial blood samples were collected and analysed, including samples adjusted for specific glucose (3.6 mmol/L, 8.3 mmol/L and 16.7 mmol/L) and PaO2 levels (range, 40-400 mm Hg).

RESULTS

In total, 159 samples were collected. Bland-Altman analysis showed good correlation between the commercial glucometer and standard glucose analyser. Error-grid analysis revealed that all of the results were within zone A (ie, the clinically accurate estimate zone). The biases between the two systems were low at different PaO2 levels and haematocrits. Finally, the influence of different PaO2 levels was within acceptable ranges.

CONCLUSIONS

The GO-based glucometer evaluated in this study provides accurate results even when measured at high PaO2 and different haematocrits and is suitable for measuring arterial glucose levels in premature infants.

System accuracy of blood glucose monitoring systems: impact of use by patients and ambient conditions

For self-monitoring of blood glucose by people with diabetes, the reliability of the measured blood glucose values is a prerequisite in order to ensure correct therapeutic decisions. Requirements for system accuracy are defined by the International Organization for Standardization (ISO) in the standard EN ISO 15197:2003. However, even a system with high analytical quality is not a guarantee for accurate and reliable measurement results. Under routine life conditions, blood glucose measurement results are affected by several factors. First, the act of performing measurements as well as the handling of the system may entail numerous possible error sources, such as traces of glucose-containing products on the fingertips, the use of deteriorated test strips, or the incorrect storage of test strips. Second, ambient and sampling conditions such as high altitude, partial pressure of oxygen, ambient temperature, and the use of alternate test sites can have an influence on measurement results. Therefore, the user-friendliness of a system and the quality of the manufacturer's labeling to reduce the risk of handling errors are also important aspects in ensuring reliable and accurate measurement results. In addition, the analytical performance of systems should be less prone to user errors and ambient conditions. Finally, people with diabetes must be aware of the information and instructions in the manufacturer's labeling and must be able to measure and interpret blood glucose results correctly.

Effects of simulated altitude on blood glucose meter performance: implications for in-flight blood glucose monitoring

BACKGROUND

Most manufacturers of blood glucose monitoring equipment do not give advice regarding the use of their meters and strips onboard aircraft, and some airlines have blood glucose testing equipment in the aircraft cabin medical bag. Previous studies using older blood glucose meters (BGMs) have shown conflicting results on the performance of both glucose oxidase (GOX)- and glucose dehydrogenase (GDH)-based meters at high altitude. The aim of our study was to evaluate the performance of four new-generation BGMs at sea level and at a simulated altitude equivalent to that used in the cabin of commercial aircrafts.

METHODOLOGY/PRINCIPAL FINDINGS

Blood glucose measurements obtained by two GDH and two GOX BGMs at sea level and simulated altitude of 8000 feet in a hypobaric chamber were compared with measurements obtained using a YSI 2300 blood glucose analyzer as a reference method. Spiked venous blood samples of three different glucose levels were used. The accuracy of each meter was determined by calculating percentage error of each meter compared with the YSI reference and was also assessed against standard International Organization for Standardization (ISO) criteria. Clinical accuracy was evaluated using the consensus error grid method. The percentage (standard deviation) error for GDH meters at sea level and altitude was 13.36% (8.83%; for meter 1) and 12.97% (8.03%; for meter 2) with p = .784, and for GOX meters was 5.88% (7.35%; for meter 3) and 7.38% (6.20%; for meter 4) with p = .187. There was variation in the number of time individual meters met the standard ISO criteria ranging from 72-100%. Results from all four meters at both sea level and simulated altitude fell within zones A and B of the consensus error grid, using YSI as the reference.

CONCLUSIONS

Overall, at simulated altitude, no differences were observed between the performance of GDH and GOX meters. Overestimation of blood glucose concentration was seen among individual meters evaluated, but none of the results obtained would have resulted in dangerous failure to detect and treat blood glucose errors or in giving treatment that was actually contradictory to that required.

Increased insulin requirements during exercise at very high altitude in type 1 diabetes

OBJECTIVE

Safe, very high altitude trekking in subjects with type 1 diabetes requires understanding of glucose regulation at high altitude. We investigated insulin requirements, energy expenditure, and glucose levels at very high altitude in relation to acute mountain sickness (AMS) symptoms in individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Eight individuals with complication-free type 1 diabetes took part in a 14-day expedition to Mount Meru (4,562 m) and Mount Kilimanjaro (5,895 m) in Tanzania. Daily insulin doses, glucose levels, energy expenditure, and AMS symptoms were determined. Also, energy expenditure and AMS symptoms were compared with a healthy control group.

RESULTS

We found a positive relation between AMS symptoms and insulin requirements (r = 0.78; P = 0.041) and AMS symptoms and glucose levels (r = 0.86; P = 0.014) for Mount Kilimanjaro. Compared with sea level, insulin doses tended to decrease by 14.2% (19.7) (median [interquartile range]) (P = 0.41), whereas glucose levels remained stable up to 5,000 m altitude. However, at altitudes >5,000 m, insulin dose was unchanged (36.8 ± 17 vs. 37.6 ± 19.1 international units [mean ± SD] P = 0.75), but glucose levels (7.5 ± 0.6 vs. 9.5 ± 0.8 mmol/L [mean ± SD] P = 0.067) and AMS scores (1.3 ± 1.6 vs. 4.4 ± 4 points [mean ± SD] P = 0.091) tended to increase. Energy expenditure and AMS symptoms were comparable in both groups (P = 0.84).

CONCLUSIONS

Our data indicate that in complication-free individuals with type 1 diabetes, insulin requirements tend to increase during altitudes above 5,000 m despite high energy expenditure. This change may be explained, at least partly, by AMS.