Effect of high altitude on blood glucose meter performance

At-home bodyweight interval exercise in the fed versus fasted state lowers postprandial glycemia and appetite perceptions in females

Limited research has characterized the metabolic health benefits of bodyweight interval exercise (BWE) performed outside of a laboratory setting. Metabolic responses to exercise can also be influenced by meal timing around exercise, but the interactive effects of BWE and nutrition are unknown. This study investigated the effects of BWE performed in the fasted or fed state on postprandial glycemia, post-exercise fat oxidation and appetite perceptions. Twelve females (23 ± 2 years; 22 ± 2 kg/m2) underwent two virtually-monitored trials that involved completing BWE (10 × 1 min, 1 min recovery) 5 min before (FastEX) or beginning BWE 10 min after (FedEX) a standardized breakfast. Heart rate and rating of perceived exertion (RPE) were measured during exercise and capillary glucose concentrations were measured for 2 h postprandial. Following exercise, appetite perceptions were assessed and Lumen expired carbon dioxide percentage (L%CO2) was measured as an index of fat oxidation. Heart rate (85 ± 5%) and RPE (14 ± 2) did not differ between conditions (p > 0.05). Postprandial glucose mean (6.1 ± 0.6 vs. 6.8 ± 0.8 mmol/L, p = 0.03), peak (7.4 ± 1.2 vs. 8.5 ± 1.5 mmol/L, p = 0.01), and area under the curve (AUC) (758 ± 72 vs. 973 ± 82 mmol/L × 2 h, p = 0.004) were lower in FedEX versus FastEX. Appetite perceptions were lower in FedEX versus FastEX (-87.63 ± 58.51 vs. -42.06 ± 34.96 mm, p = 0.029). Post-exercise L%CO2 was transiently decreased 30 min post-exercise in both conditions (4.03 ± 0.38 vs. 4.29 ± 0.34%, p = 0.0023), reflective of increased fat oxidation following BWE. These findings demonstrate that BWE performed in the fed compared to the fasted state lowered postprandial glycemia and appetite perceptions in females.

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.

Bringing the lab bench to the field: Point-of-care testing for enhancing health research and stakeholder engagement in rural/remote, indigenous, and resource-limited contexts

Point-of-care testing (POCT) allows researchers and health-care providers to bring the lab bench to the field, providing essential health information that can be leveraged to improve health care, accessibility, and understanding across clinical and research settings. Gaps in health service access are most pronounced in what we term RIR settings-rural/remote regions, involving Indigenous peoples, and/or within resource-limited settings. In these contexts, morbidity and mortality from infectious and non-communicable diseases are disproportionately higher due to numerous geographic, economic, political, and sociohistorical factors. Human biologists and global health scholars are well-positioned to contribute on-the-ground-level insights that can serve to minimize global health inequities and POCT has the potential to augment such approaches. While the clinical benefits of POCT include increasing health service access by bringing testing, rapid diagnosis, and treatment to underserved communities with limited pathways to centralized laboratory testing, POCT also provides added benefits to both health-focused researchers and their participants. Through portable, minimally invasive devices, researchers can provide actionable health data to participants by coupling POCT with population-specific health education, discussing results and their implications, creating space for participants to voice concerns, and facilitating linkages to treatment. POCT can also strengthen human biology research by shedding light on questions of evolutionary and biocultural importance. Here, we expand on the epidemiological and research value, as well as practical and ethical challenges of POCT across stakeholders (i.e., participant, community, health researcher, and trainee). Finally, we emphasize the immense opportunities of POCT for fostering collaborative research and enhancing access to health delivery and information and, by extension, helping to mitigate persistent global health inequities.

Blood glucose meters and test strips: global market and challenges to access in low-resource settings

Blood glucose meters and test strips for self-monitoring of blood glucose (SMBG) are often inaccessible to, and infrequently used by, people with diabetes in countries with limited resources for health care. Supplies for measuring blood glucose can also be scarce in health facilities, despite being needed in a myriad of clinical settings at all levels of the health system. Numerous studies and international guidelines emphasise the value of SMBG in diabetes care, particularly in people with type 1 diabetes. In this Review, we assess global access to blood glucose meters and test strips, collating published information on cost, availability, system accuracy, competitive bidding, technological trends, and non-financial barriers. We also provide new information on global market share data and prices, taxes and tariffs, and product availability. Blood glucose meters and test strips should be viewed similarly to essential medicines, with issues of access prioritised by relevant international agencies. Efforts are needed to reduce tariffs and taxes and to create unified global system accuracy requirements and accountable post-marketing evaluations. Preferential pricing arrangements, pooled procurement, and best-purchasing practices could help to lower direct costs. SMBG supplies should also be included in national health insurance schemes. Enhanced diabetes education of health professionals and patients is crucial to ensure effective use of SMBG. Finally, as technology advances for people who can afford new interstitial fluid glucose monitoring systems, blood glucose meters and test strips must remain available and become more affordable in low-resource settings.

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.

Reduced Lung Cancer Mortality With Lower Atmospheric Pressure

BACKGROUND

Research has shown that higher altitude is associated with lower risk of lung cancer and improved survival among patients. The current study assessed the influence of county-level atmospheric pressure (a measure reflecting both altitude and temperature) on age-adjusted lung cancer mortality rates in the contiguous United States, with 2 forms of spatial regression.

METHODS

Ordinary least squares regression and geographically weighted regression models were used to evaluate the impact of climate and other selected variables on lung cancer mortality, based on 2974 counties.

RESULTS

Atmospheric pressure was significantly positively associated with lung cancer mortality, after controlling for sunlight, precipitation, PM2.5 (µg/m3), current smoker, and other selected variables. Positive county-level β coefficient estimates (P < .05) for atmospheric pressure were observed throughout the United States, higher in the eastern half of the country.

CONCLUSION

The spatial regression models showed that atmospheric pressure is positively associated with age-adjusted lung cancer mortality rates, after controlling for other selected variables.

Prevalence of gestational diabetes mellitus based on various screening strategies in western Kenya: a prospective comparison of point of care diagnostic methods

Background

Early diagnosis of gestational diabetes mellitus (GDM) is crucial to prevent short term delivery risks and long term effects such as cardiovascular and metabolic diseases in the mother and infant. Diagnosing GDM in Sub-Saharan Africa (SSA) however, remains sub-optimal due to associated logistical and cost barriers for resource-constrained populations. A cost-effective strategy to screen for GDM in such settings are therefore urgently required. We conducted this study to determine the prevalence of gestational diabetes mellitus (GDM) and assess utility of various GDM point of care (POC) screening strategies in a resource-constrained setting.

Methods

Eligible women aged ≥18 years, and between 24 and 32 weeks of a singleton pregnancy, prospectively underwent testing over two days. On day 1, a POC 1-h 50 g glucose challenge test (GCT) and a POC glycated hemoglobin (HbA1c) was assessed. On day 2, fasting blood glucose, 1-h and 2-h 75 g oral glucose tolerance test (OGTT) were determined using both venous and POC tests, along with a venous HbA1c. The International Association of Diabetes in Pregnancy Study Group (IADPSG) criteria was used to diagnose GDM. GDM prevalence was reported with 95% confidence interval (CI). Specificity, sensitivity, positive predictive value, and negative predictive value of the various POC testing strategies were determined using IADPSG testing as the standard reference.

Results

Six hundred-sixteen eligible women completed testing procedures. GDM was diagnosed in 18 women, a prevalence of 2.9% (95% CI, 1.57% - 4.23%). Compared to IADPSG testing, POC IADPSG had a sensitivity and specificity of 55.6% and 90.6% respectively while that of POC 1-h 50 g GCT (using a diagnostic cut-off of ≥7.2 mmol/L [129.6 mg/dL]) was 55.6% and 63.9%. All other POC tests assessed showed poor sensitivity.

Conclusions

POC screening strategies though feasible, showed poor sensitivity for GDM detection in our resource-constrained population of low GDM prevalence. Studies to identify sensitive and specific POC GDM screening strategies using adverse pregnancy outcomes as end points are required.

Trials registration

Clinical trials.gov: NCT02978807, Registered 29 November 2016.

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.

Diabetes, trekking and high altitude: recognizing and preparing for the risks

Although regular physical activity is encouraged for individuals with diabetes, exercise at high altitude increases risk for a number of potential complications. This review highlights our current understanding of the key physiological and clinical issues that accompany high-altitude travel and proposes basic clinical strategies to help overcome obstacles faced by trekkers with Type 1 or Type 2 diabetes. Although individuals with diabetes have adaptations to the hypoxia of high altitude (increased ventilation, heart rate, blood pressure and hormonal responses), elevated counter-regulatory hormones can impair glycaemic control, particularly if mountain sickness occurs. Moreover, high-altitude-induced anorexia and increased energy expenditure can predispose individuals to dysglycaemia unless careful adjustments in medication are performed. Frequent blood glucose monitoring is imperative, and results must be interpreted with caution because capillary blood glucose meter results may be less accurate at high elevations and low temperatures. It is also important to undergo pre-travel screening to rule out possible contraindications owing to chronic diabetes complications and make well-informed decisions about risks. Despite the risks, healthy, physically fit and well-prepared individuals with Type 1 or Type 2 diabetes who are capable of advanced self-management can be encouraged to participate in these activities and attain their summit goals. Moreover, trekking at high altitude can serve as an effective means to engage in physical activity and to increase confidence with fundamental diabetes self-management skills.

Vulnerability of point-of-care test reagents and instruments to environmental stresses: implications for health professionals and developers

Strategic integration of point-of-care (POC) diagnostic tools during crisis response can accelerate triage and improve management of victims. Timely differential diagnosis is essential wherever care is provided to rule out or rule in disease, expedite life-saving treatment, and improve utilization of limited resources. POC testing needs to be accurate in any environment in which it is used. Devices are exposed to potentially adverse storage and operating conditions, such as high/low temperature and humidity during emergencies and field rescues. Therefore, characterizing environmental conditions allows technology developers, operators, and responders to understand the broad operational requirements of test reagents, instruments, and equipment in order to improve the quality and delivery of care in complex emergencies, disasters, and austere environmental settings. This review aims to describe the effects of environmental stress on POC testing performance and its impact on decision-making, to describe how to study the effects, and to summarize ways to mitigate the effects of environmental stresses through good laboratory practice, development of robust reagents, and novel thermal packaging solutions.

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.

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.

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.

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.

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.

Hematocrit compensation in electrochemical blood glucose monitoring systems

BACKGROUND

Hematocrit (Hct) is a common interferent in test strips used by diabetes patients to self-monitor blood glucose (BG), resulting in measurement bias. Described is an electrochemical BG monitoring system (OneTouch(®) Verio™) that uses a cofacial sensor design, soluble enzyme chemistry, and multiphasic waveform to effectively correct for patient Hct, delivering an accurate reading for whole BG.

METHODS

The test strip comprises thin-film gold and palladium electrodes arranged cofacially and spatially separated with a thin spacer. Soluble glucose-sensing reagents are located on the lower palladium electrode and are hydrated on sample application. Blood glucose is oxidized by flavoprotein glucose dehydrogenase, with electron transfer via (reduced) potassium ferrocyanide mediator at the palladium electrode. Hematocrit levels are estimated by measuring oxidation of mediator diffusion to the upper gold electrode during the first portion of the assay. The Hct-corrected glucose levels are determined by an on-meter algorithm.

RESULTS

In performance testing of blood samples at five glucose levels (30-560 mg/dl) and five Hct levels (19-61%), using 12 test meters and 3 test strip lots, 100% of results (N = 2700) met International Organization for Standardization accuracy criteria (within ± 15 mg/dl and ± 20% of reference results at glucose levels of <75 and ≥75 mg/dl, respectively). Furthermore, 99.9% (2698 of 2700) of results were within ±12 mg/dl and ± 15% of reference values at glucose levels <80 and ≥80 mg/dl, respectively.

CONCLUSIONS

The technology used in this system provides accurate BG measurements that are insensitive to Hct levels across the range 20-60%.

Occupational health of miners at altitude: adverse health effects, toxic exposures, pre-placement screening, acclimatization, and worker surveillance

CONTEXT

Mining operations conducted at high altitudes provide health challenges for workers as well as for medical personnel.

OBJECTIVE

To review the literature regarding adverse health effects and toxic exposures that may be associated with mining operations conducted at altitude and to discuss pre-placement screening, acclimatization issues, and on-site surveillance strategies.

METHODS

We used the Ovid ( http://ovidsp.tx.ovid.com ) search engine to conduct a MEDLINE search for "coal mining" or "mining" and "altitude sickness" or "altitude" and a second MEDLINE search for "occupational diseases" and "altitude sickness" or "altitude." The search identified 97 articles of which 76 were relevant. In addition, the references of these 76 articles were manually reviewed for relevant articles. CARDIOVASCULAR EFFECTS: High altitude is associated with increased sympathetic tone that may result in elevated blood pressure, particularly in workers with pre-existing hypertension. Workers with a history of coronary artery disease experience ischemia at lower work rates at high altitude, while those with a history of congestive heart failure have decreased exercise tolerance at high altitude as compared to healthy controls and are at higher risk of suffering an exacerbation of their heart failure. PULMONARY EFFECTS: High altitude is associated with various adverse pulmonary effects, including high-altitude pulmonary edema, pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness. Mining at altitude has been reported to accelerate silicosis and other pneumoconioses. Miners with pre-existing pneumoconioses may experience an exacerbation of their condition at altitude. Persons traveling to high altitude have a higher incidence of Cheyne-Stokes respiration while sleeping than do persons native to high altitude. Obesity increases the risk of pulmonary hypertension, acute mountain sickness, and sleep-disordered breathing. NEUROLOGICAL EFFECTS: The most common adverse neurological effect of high altitude is acute mountain sickness, while the most severe adverse neurological effect is high-altitude cerebral edema. Poor sleep quality and sleep-disordered breathing may contribute to daytime sleepiness and impaired cognitive performance that could potentially result in workplace injuries, particularly in miners who are already at increased risk of suffering unintentional workplace injuries. OPHTHALMOLOGICAL EFFECTS: Adverse ophthalmological effects include increased exposure to ultraviolet light and xerophthalmia, which may be further exacerbated by occupational dust exposure. RENAL EFFECTS: High altitude is associated with a protective effect in patients with renal disease, although it is unknown how this would affect miners with a history of chronic renal disease from exposure to silica and other renal toxicants. HEMATOLOGICAL EFFECTS: Advanced age increases the risk of erythrocytosis and chronic mountain sickness in miners. Thrombotic and thromboembolic events are also more common at high altitude. MUSCULOSKELETAL EFFECTS: Miners are at increased risk for low back pain due to occupational factors, and the easy fatigue at altitude has been reported to further predispose workers to this disorder. TOXIC EXPOSURES: Diesel emissions at altitude contain more carbon monoxide due to increased incomplete combustion of fuel. In addition, a given partial pressure of carbon monoxide at altitude will result in a larger percentage of carboxyhemoglobin at altitude. Miners with a diagnosis of chronic obstructive pulmonary disease may be at higher risk for morbidity from exposure to diesel exhaust at altitude.

CONCLUSIONS

Both mining and work at altitude have independently been associated with a number of adverse health effects, although the combined effect of mining activities and high altitude has not been adequately studied. Careful selection of workers, appropriate acclimatization, and limited on-site surveillance can help control most health risks. Further research is necessary to more completely understand the risks of mining at altitude and delineate what characteristics of potential employees put them at risk for altitude-related morbidity or mortality.

Comparison of capillary whole blood versus venous plasma glucose estimations in screening for diabetes mellitus in epidemiological studies in developing countries

BACKGROUND

This study compared capillary blood glucose (CBG) measurements with venous plasma glucose (VPG) measurements in screening for diabetes and prediabetes in epidemiological studies.

METHODS

Four hundred seven subjects ≥ 20 years old (54.1% male) without previously known diabetes underwent oral glucose tolerance tests at a tertiary diabetes center in Chennai, India. Simultaneous measurements of CBG (OneTouch(®) Ultra(®) meter, LifeScan, a Johnson & Johnson Company, Milpitas, CA) and VPG (AU2700, Beckman, Fullerton, CA) were performed, both in the fasting state and 2 h after a 75-g glucose load (2-h post-glucose [PG]). Diabetes, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) were defined using American Diabetes Association (ADA) and World Health Organization (WHO) criteria.

RESULTS

The mean fasting CBG and VPG values were 122 ± 39 mg/dL and 115 ± 40 mg/dL, respectively, and the 2-h PG values were 203 ± 84 mg/dL and 176 ± 85 mg/dL, respectively. The Pearson's correlation coefficient for CBG with VPG was 0.681 (P < 0.001) in the fasting state and 0.897 (P < 0.001) for the 2-h PG load, indicating good correlation between the two methods. Based on the ADA fasting criteria, 31.9% versus 21.1% (capillary vs. venous) had diabetes, whereas based on the WHO criteria, 43.2% versus 38.6% (capillary vs. venous) had diabetes. The accuracy of identifying diabetes was 83.3% by the ADA and 90.9% by WHO criteria, for IGT it was 85.3%, and for IFG it was 66.3% by the ADA and 72.2% by the WHO criteria.

CONCLUSION

CBG is a feasible alternative for screening of diabetes and IGT in epidemiological studies in developing countries where obtaining venous samples may be difficult.

Wavesense technology glucometer Linus for routine self-monitoring and clinical practice

Conventional glucometer systems for plasma/blood glucose monitoring are based on colorimetry or static electrochemistry using a fixed input signal. The recent glucometer Linus, Wellion, Agamatrix, USA, based on wavesense dynamic electrochemistry, uses a time-varying input signal to give a more accurate glucose reading. The purpose of this study was to compare the plasma glucose (PG) readings obtained by nursing staff from glucometer Linus and PG values estimated on an approved analyzer Daytona™, Randox, Global Medical Instrumentation, Inc., MN, USA. In the course of 5 weeks, 221 fingerprick capillary blood samples were taken from persons with diabetes at different times and investigated using glucometer Linus. Within two following minutes, blood from the same fingerprick was also collected in a tube and centrifuged; the plasma was analyzed on the Daytona™ analyzer. Statistical analysis was performed using the software SPSS v. 15.0, SPSS Inc., Chicago, IL, USA. A total of 221 paired PG values were plotted on the error grid diagram indicating that 218 values (98.6%) of the glucose readings (Linus vs. Daytona) were within the clinically accurate zone A (maximum difference ±20%) and 3 values (1.4%) within the acceptable zone B. Daytona showed 4 PG values <4.2 mmol/l (75 mg/dl) and their difference of respective Linus readings was always <0.83 mmol/l (15 mg/dl). Correlation of results was strong (r = 0.992). Glucometer Linus readings correspond to the ISO and FDA standards. So, Linus appears to be an accurate device for PG-self-monitoring and clinical practice.

The equine neonatal intensive care laboratory: point-of-care testing

Rapid evaluation and intervention is a requirement and a characteristic of patient management in neonatal intensive care units, and this applies for equine neonates also. Appropriate interventions are based on solid knowledge of age, maturity, and species-specific differences in reference ranges. Point-of-care (POC) testing devices speedup decision making regarding treatments and interventions. However, there are potential limitations of these devices when applied to age groups and species beyond those they were specifically developed for. This article discusses the age-specific differences in the reference ranges and the potential limitations of POC devices currently used, which may affect delivery of care.

Accuracy of handheld blood glucose meters at high altitude

Background

Due to increasing numbers of people with diabetes taking part in extreme sports (e.g., high-altitude trekking), reliable handheld blood glucose meters (BGMs) are necessary. Accurate blood glucose measurement under extreme conditions is paramount for safe recreation at altitude. Prior studies reported bias in blood glucose measurements using different BGMs at high altitude. We hypothesized that glucose-oxidase based BGMs are more influenced by the lower atmospheric oxygen pressure at altitude than glucose dehydrogenase based BGMs.

Methodology/Principal Findings

Glucose measurements at simulated altitude of nine BGMs (six glucose dehydrogenase and three glucose oxidase BGMs) were compared to glucose measurement on a similar BGM at sea level and to a laboratory glucose reference method. Venous blood samples of four different glucose levels were used. Moreover, two glucose oxidase and two glucose dehydrogenase based BGMs were evaluated at different altitudes on Mount Kilimanjaro. Accuracy criteria were set at a bias <15% from reference glucose (when >6.5 mmol/L) and <1 mmol/L from reference glucose (when <6.5 mmol/L). No significant difference was observed between measurements at simulated altitude and sea level for either glucose oxidase based BGMs or glucose dehydrogenase based BGMs as a group phenomenon. Two GDH based BGMs did not meet set performance criteria. Most BGMs are generally overestimating true glucose concentration at high altitude.

Conclusion

At simulated high altitude all tested BGMs, including glucose oxidase based BGMs, did not show influence of low atmospheric oxygen pressure. All BGMs, except for two GDH based BGMs, performed within predefined criteria. At true high altitude one GDH based BGM had best precision and accuracy.

Quality of glucose measurement with blood glucose meters at the point-of-care: relevance of interfering factors

AIM

A good understanding of the relevance of interfering factors having an impact on blood glucose (BG) measurement is needed to obtain the required quality. This depends on the application in which meters designed for self-monitoring of BG (SMBG) are used.

METHODS

By means of a literature search all publications (from January 1, 1980 to August 10, 2009) were identified that report about the influence of potentially interfering substances/factors on the measurement quality of BG meters.

RESULTS

Certain substances (e.g., maltose) can have a profound and misleading impact on the BG measurement result when the enzymatic reaction embedded on the given test strips cross-reacts. Also, a number of other drugs (e.g., acetaminophen) and factors (like temperature and altitude) affect the reliability of BG measurement massively. However, the susceptibility of the BG meter (depending on the enzyme technology of the test strips) differs significantly.

CONCLUSIONS

In daily practice the factors that have a relevant impact on the reliability of BG measurements with modern BG meters are rarely met. Clearly this also depends on the intended use (SMBG in patient hands vs. point-of-care testing in hospitals). To avoid misleading measurement results requires adequate training of all people involved.

Review article: glucose measurement in the operating room: more complicated than it seems

Abnormalities of blood glucose are common in patients undergoing surgery, and in recent years there has been considerable interest in tight control of glucose in the perioperative period. Implementation of any regime of close glycemic control requires more frequent measurement of blood glucose, a function for which small, inexpensive, and rapidly responding point-of-care devices might seem highly suitable. However, what is not well understood by many anesthesiologists and other staff caring for patients in the perioperative period is the lack of accuracy of home glucose meters that were designed for self-monitoring of blood glucose by patients. These devices have been remarketed to hospitals without appropriate additional testing and without an appropriate regulatory framework. Clinicians who are accustomed to the high level of accuracy of glucose measurement by a central laboratory device or by an automated blood gas analyzer may be unaware of the potential for harmful clinical errors that are caused by the inaccuracy exhibited by many self-monitoring of blood glucose devices, especially in the hypoglycemic range. Knowledge of the limitations of these meters is essential for the perioperative physician to minimize the possibility of a harmful measurement error. In this article, we will highlight these areas of interest and review the indications, technology, accuracy, and regulation of glucose measurement devices used in the perioperative setting.

Challenges to glycemic measurement in the perioperative and critically ill patient: a review

Accurate monitoring of glucose in the perioperative environment has become increasingly important over the last few years. Because of increased cost, turnaround time, and sample volume, the use of central laboratory devices for glucose measurement has been somewhat supplanted by point-of-care (POC) glucose devices. The trade-off in moving to these POC systems has been a reduction in accuracy, especially in the hypoglycemic range. Furthermore, many of these POC devices were originally developed, marketed, and received Food and Drug Administration regulatory clearance as home use devices for patients with diabetes. Without further review, many of these POC glucose measurement devices have found their way into the hospital environment and are used frequently for measurement during intense insulin therapy, where accurate measurements are critical. This review covers the technology behind glucose measurement and the evidence questioning the use of many POC devices for perioperative glucose management.

Performance of glucose dehydrogenase (GDH) based and glucose oxidase (GOX) based blood glucose meter systems at moderately high altitude

OBJECTIVE

Self-monitoring of blood glucose (SMBG) is a fairly efficient method of preventing hypoglycaemia in diabetic patients. Blood glucose meters (BGMs) are influenced by factors such as altitude, temperature, blood oxygen concentration, low atmospheric pressure or humidity. In this study we aimed at evaluating the performance of glucose dehydrogenase (GDH) or glucose oxidase (GOX) based glucometers at moderately high altitude.

METHOD

A total of 286 female or male patients, most of whom had type 2 diabetes, were included in this study. The simultaneous readings made by two different glucometers were compared with the readings made at the reference laboratory.

RESULTS

Blood glucose levels measured by a GDH based glucometer at moderately high altitude were significantly (p=0.007) higher compared to those measured at the reference laboratory. Although blood glucose levels measured by a GOX based glucometer were lower compared to those measured at the reference laboratory, the difference was not significant (p=0.54). The difference between GOX and GDH readings with regard to blood glucose levels was also significant (p=0.001). Blood glucometers were influenced by moderately high altitude.

CONCLUSION

The use of a GOX based glucometer at moderately high altitude may be useful in detecting hypoglycaemia at these conditions, since significantly higher blood glucose levels were measured with a GDH based glucometer compared to reference readings.

Thermal stress and point-of-care testing performance: suitability of glucose test strips and blood gas cartridges for disaster response

OBJECTIVE

Point-of-care testing (POCT) devices are deployed in the field for emergency on-site testing under a wide range of environmental conditions. Our objective was to evaluate the performance of glucose meter test strips and handheld blood gas analyzer cartridges following thermal stresses that simulate field conditions.

METHODS

We evaluated electrochemical and spectrophotometric glucose meter systems and a handheld blood gas analyzer. Glucose test strips were cold-stressed (-21 degrees C) and heat-stressed (40 degrees C) for up to 4 weeks. Blood gas cartridges were stressed at -21 degrees C, 2 degrees C, and 40 degrees C for up to 72 hours. Test strip and cartridge performance was evaluated using aqueous quality control solutions. Results were compared with those obtained with unstressed POCT strips and cartridges.

RESULTS

Heated glucose test strips and blood gas cartridges yielded elevated results. Frozen test strips and cooled cartridges yielded depressed glucose and blood gas results, respectively. Frozen cartridges failed.

CONCLUSIONS

The performance of glucose test strips and blood gas cartridges was affected adversely by thermal stresses. Heating generated elevated results, and cooling depressed results. Disaster medical assistance teams and emergency medical responders should be aware of these risks. Field POCT devices must be robust to withstand adverse conditions. We recommend that industry produce POCT devices and reagents suitable for disaster medical assistance teams.

Self-Monitoring of Blood Glucose (SMBG) in insulin- and non-insulin-using adults with diabetes: consensus recommendations for improving SMBG accuracy, utilization, and research

Current clinical guidelines for diabetes care encourage self-monitoring of blood glucose (SMBG) to improve glycemic control. Specific protocols remain variable, however, particularly among non-insulin-using patients. This is due in part to efficacy studies that neglect to consider (1) the performance of monitoring equipment under real-world conditions, (2) whether or how patients have been taught to take action on test results, and (3) the physiological, behavioral, and social circumstances in which SMBG is carried out. As such, a multidisciplinary group of specialists, including several endocrinologists, a health psychologist, a diabetes nurse practitioner, and a patient advocate (the Panel), discuss within this review article how the potential of SMBG might be fully realized in today's healthcare environment. The resulting recommendations cover technological, clinical, behavioral, and research considerations with the aim of achieving short- and long-term benefits, ranging from fewer hypoglycemic episodes to lower complication-related costs. The panel also made suggestions for designing future studies that increase the ability to discern optimal models of SMBG utilization for individuals with diabetes who may, or may not, use insulin.

Metabolic and Cardiovascular Parameters in Type 1 Diabetes at Extreme Altitude

PURPOSE

The American Diabetes Association states that physical activity can be performed by individuals with Type 1 diabetes. Nevertheless, extreme altitude mountaineering represents a demanding challenge. We present the metabolic and cardiovascular parameters found in individuals with Type 1 diabetes during the ascent to Cho Oyu located at a height of 8201 m.

METHODS

Six individuals with Type 1 diabetes and 10 matched controls participated in the expedition. Both groups were evaluated before and after 4 h of trekking for vital indices, blood gases, acute mountain sickness, and metabolic control at 0, 3700, and 5800 m.

RESULTS

No difference between the groups was observed in acute mountain sickness scores. There was a progressive elevation in basal heart rates in both groups at increasing altitude while no changes were observed in mean blood pressures. After the 3 h of trekking, a significant increase in heart rate was observed in the controls at 0 m whereas a significant decrease in blood pressure was observed at higher altitude only in controls. HbA1c levels were worse after the expedition in both groups. A progressive increase in insulin requirement was observed in subjects with Type 1 diabetes (38 +/- 6 U x d(-1) at 0 m to 51 +/- 6 at 4200 m, P < 0.001). At an altitude of 5800 m, there was a significant increase in blood lactate concentration, independently of the activity level in the two groups.

CONCLUSIONS

At extreme altitude, highly motivated trekkers with Type 1 diabetes but free from long-term complications present metabolic and cardiovascular parameters comparable with those of control subjects despite a worsening in metabolic control. This type of physical activity must be accompanied by careful glucose monitoring.