Adventure travel and type 1 diabetes: the complicating effects of high altitude

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.

Continuous Glucose Monitoring and Physical Activity

Continuous glucose monitoring (CGM) use has several potential positive effects on diabetes management. These benefits are, e.g., increased time in range (TIR), optimized therapy, and developed documentation. Physical activity is a recommended intervention tool in diabetes management, especially for people with type 2 diabetes (T2D). The benefits of physical activity for people with diabetes can be seen as an improvement of glycemic control, glycemic variability, and the reduction of insulin resistance. In relation to the physical activity of people with T2D, the benefits of CGM use can even be increased, and CGM can be a helpful tool to prevent adverse events due to physical activity of people with diabetes, such as hypoglycemic events and nocturnal hypoglycemia after sports. This narrative review aims to provide solid recommendations for the use of CGM in everyday life physical activities based on the noted benefits and to give a general overview of the guidelines on physical activity and CGM use for people with diabetes.

Traveling Across Time Zones With Type 1 Diabetes: A Pilot Study Comparing Insulin Degludec With Insulin Glargine U100

OBJECTIVE

For people with type 1 diabetes, there are limited evidence-based resources to support self-management when traveling across multiple time zones. Here, we compared glycemic control on insulin degludec versus glargine U100 as the basal insulin for adults using multiple daily injections (MDI) while traveling across multiple time zones.

RESEARCH DESIGN AND METHODS

This randomized crossover pilot study compared insulin degludec versus glargine U100 for adults with type 1 diabetes using MDI insulin during long-haul travel to and from Hawaii to New York. Insulin degludec was administered daily at the same time regardless of time zone, and glargine was administered per travel algorithm. Primary end point was the percentage of time in range (TIR) between 70 and 140 mg/dL during the initial 24 h after each direction of travel. Secondary end points included standard continuous glucose monitoring metrics, jet lag, fatigue, and sleep.

RESULTS

The study enrolled 25 participants (56% women, mean ± SD age of 35 ± 14.5 years, HbA1c of 7.4 ± 1.2% [57 ± 13.1 mmol/mol], and diabetes duration of 20.6 ± 15 years). There was no significant difference in glycemic outcomes between the two arms of the study, including TIR, hypoglycemia, or hyperglycemia. Neither group achieved >70% TIR 70-180 mg/dL during travel. Jet lag was greater on glargine U100 in eastward travel but not westward. Fatigue was greater after westward travel on glargine. Sleep was not significantly different between basal insulins.

CONCLUSIONS

In adults with type 1 diabetes using MDI of insulin and traveling across multiple time zones, glycemic outcomes were similar comparing insulin degludec and glargine U100.

Wilderness Medical Society Clinical Practice Guidelines for Diabetes Management

The Wilderness Medical Society convened an expert panel in 2018 to develop a set of evidence-based guidelines for the treatment of type 1 and 2 diabetes, as well as the recognition, prevention, and treatment of complications of diabetes in wilderness athletes. We present a review of the classifications, pathophysiology, and evidence-based guidelines for planning and preventive measures, as well as best practice recommendations for both routine and urgent therapeutic management of diabetes and glycemic complications. These recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks or burdens for each recommendation.

What do we know about travel for children with special health care needs? A review of the literature

BACKGROUND

Children travel with their families, including children with chronic illness. We know that adults with chronic illness who travel are more likely than their healthy peers to become sick while traveling. A review of the literature was undertaken to identify what is known about traveling with children with special health care needs and to identify gaps in our knowledge.

METHODS

An Online search of the PubMed, CINAHL and Google databases of English language literature was conducted June 2016, October 2017, June 2018 and April 2019 using the terms children and travel, air travel, travel health, disabled child, children with special healthcare needs, parents of disabled children, vacations, recreation, international, wheelchairs, planning techniques, asthma, diabetes, altitude, cystic fibrosis, inflammatory bowel disease, sickle cell disease, depression, food allergies, Attention Deficit Hyperactivity Disorder (ADHD), and seizures. The search was limited to years 2000-2019. A secondary search of relevant articles was conducted using the reference sections of articles identified in the primary search.

RESULTS

185 papers were examined for travel health related outcomes for children and adults with chronic diseases. Articles were excluded if they addressed the educational needs of students with disabilities traveling abroad, did not directly address travel health (e.g travel skills, travel itineraries), contained outdated policy statements, or were case reports of a single patient. The remaining 84 papers were organized and reviewed by organ systems. The articles were primarily descriptive and did not lend themselves to a systematic review.

CONCLUSION

Children traveling with chronic and complex health conditions are a heterogeneous group of vulnerable travelers. Closing the knowledge gap about how to best help these travelers requires a multipronged approach. Research is urgently needed to identify best practices for five of the most common chronic childhood diseases: asthma, depression, ADHD, food allergies and autism. For less common illnesses, ones typically cared for in specialty clinics, expert consensus opinion and multi-center studies are needed. Families and disease advocacy societies should be included in the research as they may have already identified the most pressing travel-related health concerns and solutions for these problems.

The Effects of High Altitude on Glucose Homeostasis, Metabolic Control, and Other Diabetes-Related Parameters: From Animal Studies to Real Life

Exposure to high altitude activates several complex and adaptive mechanisms aiming to protect human homeostasis from extreme environmental conditions, such as hypoxia and low temperatures. Short-term exposure is followed by transient hyperglycemia, mainly triggered by the activation of the sympathetic system, whereas long-term exposure results in lower plasma glucose concentrations, mediated by improved insulin sensitivity and augmented peripheral glucose disposal. An inverse relationship between altitude, diabetes, and obesity has been well documented. This is the result of genetic and physiological adaptations principally to hypoxia that favorably affect glucose metabolism; however, the contribution of financial, dietary, and other life-style parameters may also be important. According to existing evidence, people with diabetes are capable of undertaking demanding physical challenges even at extreme altitudes. Still, a number of issues should be taken into account, including the increased physical activity leading to changes in insulin demands and resistance, the performance of measurement systems under extreme weather conditions and the potential deterioration of metabolic control during climbing expeditions. The aim of this review is to present available evidence in the field in a comprehensive way, beginning from the physiology of glucose homeostasis adaptation mechanisms to high altitudes and ending to what real life experience has taught us.

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.

Managing diabetes at high altitude: personal experience with support from a Multidisciplinary Physical Activity and Diabetes Clinic

OBJECTIVE

Physical activity is important for well-being but can be challenging for people with diabetes. Data informing support of specialist activities such as climbing and high-altitude trekking are limited. A 42-year-old man with type 1 diabetes (duration 30 years) attended a Multidisciplinary Physical Activity and Diabetes Clinic planning to climb Mont Blanc during the summer and trek to Everest Base Camp in the autumn. His aims were to complete these adventures without his diabetes impacting on their success.

METHODS

We report the information provided that enabled him to safely facilitate his objectives, in particular, the requirement for frequent checking of blood glucose levels, the effects of altitude on insulin dose requirements, and recognition that acute mountain sickness may mimic the symptoms of hypoglycaemia and vice versa. Real-time continuous glucose monitoring was made available for his treks.

RESULTS

The effects of high altitude on blood glucose results and glycaemic variability while treated on multiple daily injections of insulin are reported. In addition, we present a first-person account of his experience and lessons learnt from managing diabetes at high altitude.

CONCLUSIONS

A dedicated Multidisciplinary Physical Activity and Diabetes Clinic delivering individualised, evidence-based, patient-focused advice on the effects of altitude on blood glucose levels, and provision of real-time continuous glucose monitoring enabled uneventful completion of a trek to Everest Base Camp in a person with type 1 diabetes.

Type 1 Diabetes at High Altitude: Performance of Personal Insulin Pumps and Patient Metabolic Control

High-altitude trekking can expose people to extreme environmental conditions, like low temperatures and hypobaric hypoxia. Such extreme conditions make it more difficult for people with type 1 diabetes mellitus (T1DM) to maintain glycemic control. Intensive blood glucose monitoring using either glucose meters or continuous systems is imperative in these cases. In this observational study, we report metabolic control of T1DM patients and the performance of various insulin pumps at high altitude. All 19 patients with T1DM included in this study participated in the final step of the "5000 meters above sugar level" initiative, which involved trekking Damavand Mountain to an altitude of 5670 meters above sea level. We found that all pump models worked well without any disruption and no cases of diabetes decompensation or severe hypoglycemia occurred. Therefore, healthy, physically fit, and experienced individuals with T1DM should not be discouraged from participating in mountain trekking activities, as modern personal insulin pumps work well at high altitudes.

Type 1 Diabetes Duration Decreases Pulmonary Diffusing Capacity during Exercise

BACKGROUND

Diabetes damages peripheral tissues; however, its effects on the lung are less known. Lung diffusing capacity (DLCO) is influenced by alveolar-capillary membrane conductance (DM) and pulmonary capillary blood volume (VC), both of which are reduced in adults with type 1 diabetes (T1D).

OBJECTIVE

We sought to determine if diabetes duration affects DLCO, DM, VC, and cardiac output (Q).

METHODS

24 T1D patients (10.7-52.8 years) and 24 non-diabetic controls were recruited and had DLCO, DM, VC, and Q measured at rest and during exercise (40, 70 and 90% VO2max).

RESULTS

When stratified into two groups based on age (young, <20.6 years old), there were no significant differences in DLCO, DM, VC, or Q (all of which were normalized to body surface area [BSA]) in the young group or in the old group. When stratified by diabetes duration (short duration, 0.33-8.9 years vs. long duration, 9.6-28 years), the T1D patients in the long duration group had lower DLCO/BSA and DM/BSA compared to the controls (p < 0.05). There were no differences in any of the variables in the short duration group.

CONCLUSIONS

This study has shown that duration of diabetes is associated with decrements in diffusing capacity and its components.

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.

Vacation ease: travelling with an insulin pump

BACKGROUND

Vacation travel is a welcome retreat from our everyday world. Whether the trip is trekking in Nepal, a ski vacation in the western Rockies or a beach holiday to the Caribbean, the insulin pump is a constant companion for many people with diabetes. As a healthcare professional assisting individuals in their travel plans, we can contribute to the success of their trip by encouraging early preparation and by sharing practical and timely tips.

PURPOSE

To provide current information and practical insights for healthcare professionals (HCP) who are counseling patients with diabetes travelling with an insulin pump.

LIMITATIONS

There are numerous suggestions for all patients with diabetes who travel. This article will focus on travel recommendations specific to the pump user. Due to the lack of research in this area the information shared is based on evidence where possible and otherwise patient experience.

CONCLUSION

Insulin pump users can enjoy any type of vacation travel. Certain destinations require more preparation than others but regardless of the choice of venue, preplanning in collaboration with a knowledgeable health care provider can contribute to a successful experience.

Health risks of young adult travelers with type 1 diabetes

AIM

International travel has become popular among young adults. This study evaluated the rate and characteristics of travel-associated health risks among young adults with type 1 diabetes mellitus (T1DM) compared with healthy same-aged individuals.

METHODS

A retrospective study was conducted of 47 young adults with T1DM and 48 without (controls). Structured questionnaires accessed information regarding 154 international trips during the preceding 5 years and lasted 7 days and longer.

RESULTS

Mean ± SD ages of the diabetic and control groups were 26.6 ± 5.0 and 26.9 ± 2.6 years, respectively. Mean trip durations were 80.0 (range 7.0-390.0) and 87.6 days (range 7.0-395.0), respectively. The number of trips per person was 1.5 ± 0.6 and 1.7 ± 0.8, and the proportion of trips to developing countries 64 and 61%, respectively. There were no differences between the groups in rates of travel-related diseases that required medical consultation (11% vs 15% for all trips). No patient sought medical attention for acute problems related to diabetes management. Prior to 71% of their trips to developing countries, respondents with diabetes consulted their diabetes physician; prior to 26% of their trips they switched from an insulin pump to injections; during 41% of the trips they increased glucose monitoring; and for the period of 11% of the trips they defined their metabolic control as poor. Self-reported mean hemoglobin A1c (HbA1c) levels before and after trips were 7.65 ± 1.45 and 7.81 ± 1.23%, respectively (p = 0.42, paired t-test).

CONCLUSIONS

Young adults with type 1 diabetes did not report more travel-related diseases than did healthy individuals. Most reported reasonable to good glycemic control during the trip without severe consequences.

Changes in the levels of cytokines in both diabetic/non-diabetic type I children living in a moderate altitude area in Saudi Arabia

The aim of the present study was to investigate the possible effects of living in moderate altitude area on pro/anti-inflammatory cytokines profile (IFN-γ, TNF-α, IL-6, IL-1β, IL-10, and IL-4) among type I diabetic (T1D) and non- T1D children compared with those living at sea level area. A prospective clinical study was carried out at pediatric outpatient endocrine clinics in Taif City, which is a moderate altitude area in Saudi Arabia, that stands about 1800-2000 meters above sea-level; and in Mecca City, which is a sea level area, that lies in the middle west of Saudi Arabia. Hemoglobin A1c (HbA1c) percentage was estimated and cytokine measurements were performed in sera by flow cytometry using Cytometric Bead Array (CBA) technology. In this study we included 600 children who were consecutively enrolled (sex and age were matched). The HbA1c was statistically significantly higher in children living in moderate altitude compared to those living at sea level (overall p<0.001). Furthermore, T1D patients had higher values of serum cytokine levels (IFN-γ, TNF-α, IL-6, IL-1β, IL-4, and IL-10) in comparison to non-T1D control group (overall p<0.001). In conclusion, the data of the present study clearly showed that in both T1D and non-T1D children, moderate altitude-natives expressed high HbA1c and both pro-and anti-inflammatory cytokines. Type I diabetic children living in moderate altitude or at sea level showed elevated levels of IFN-γ, TNF-α, IL-6, IL-1β, IL-4, and IL-10 than control subjects. Glycemic control in non-diabetic children was affected by living in moderate altitude, however, HbA1c significantly increased in diabetic children living in moderate altitude.

Improved glycemic control in moderate altitude type II diabetic residents

Exposure to altitude hypoxia may elicit changes in glucose homeostasis. This work is designated to investigate the glycemic control in type II diabetic patients (DMII) permanently resident at moderately high altitude (2400 m), and to investigate whether the arterial oxygen-related parameters are different in DMII patients living at altitude compared to those living at low altitude. Blood glucose, HbA1c, hemoglobin concentration, and hematocrit (HCT) were measured in moderate altitude type II diabetics and compared with both altitude nondiabetics and diabetic patients living at normoxic and normobaric conditions. The data revealed that fasting blood glucose was lower in altitude diabetic patients compared to diabetics living at low altitude (157±33 mg/dL and 176.81±15.98 mg/dL, respectively, p<0.01). Also, glycemic control was improved in altitude diabetic patients, where their HbA1c was lower than the corresponding low altitude diabetic patients (8.68±0.79% and 9.30±1.02% respectively, p<0.01). Low oxygen tension at altitude was compensated in both diabetics and nondiabetics by a significant increase in both hemoglobin and HCT (17.33±0.72 mg/dL and 50.7±2.20%, respectively) compared to the corresponding groups living at low levels (15.53±0.55 mg/dL and 45.8±1.64%, respectively). The underlying disease neither affected the arterial oxygen tension (PaO2) nor oxygen saturation (SaO2), where insignificant correlations were observed between glucose, PaO2 (r=-0.06) and SaO2 (r=-0.2). These results suggest that moderate altitude may improve the glycemic control in type II diabetic patients compared to diabetics living at sea level.

Metabolic effects of high altitude trekking in patients with type 2 diabetes

OBJECTIVE

Limited information is available regarding the metabolic effects of high altitude trekking in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Thirteen individuals with type 2 diabetes took part in a 12-day expedition to the summit of Mount Toubkal (altitude, 4,167 m), Morocco, after 6 months of exercise training. Energy expenditure, body weight, blood glucose, fasting insulin, lipids, and HbA(1c) were assessed.

RESULTS

Training reduced fasting glucose (-0.7 ± 0.9 mmol/L, P = 0.026) and increased exercise capacity (+0.3 ± 0.3 W/kg, P = 0.005). High altitude trekking decreased fasting insulin concentrations (-3.8 ± 3.2 μU/L, P = 0.04), total cholesterol (-0.7 ± 0.8 mmol/L, P = 0.008), and LDL cholesterol (-0.5 ± 0.6 mmol/L, P = 0.007).

CONCLUSIONS

High altitude trekking preceded by exercise training is feasible for patients with type 2 diabetes. It improves blood glucose, lipids, and fasting insulin concentrations, while glucose control is maintained.

Metabolic regulation during constant moderate physical exertion in extreme conditions in Type 1 diabetes

BACKGROUND

Constant moderate intensity physical exertion in humid environments at altitude poses a considerable challenge to maintaining euglycaemia with Type 1 diabetes. Blood glucose concentrations and energy expenditure were continuously recorded in a person trekking at altitude in a tropical climate to quantify changes in glucose concentrations in relation to energy expenditure.

CASE REPORT

Blood glucose concentrations and energy expenditure were continuously monitored with a Guardian® real-time continuous glucose monitoring system (CGMS) and a SenseWear® Pro3 armband (BodyMedia Inc., USA), in a 27-year-old woman with Type 1 diabetes, during her climb up Mount Kinabalu in Borneo (c. 4095 m). Comparative control data from the same person was collected in the UK (temperate climate at sea level) and Singapore (tropical climate at sea level). Maximum physical effort during the climb was < 60% VO(2MAX) (maximal oxygen consumption). Mean daily calorific intakes were 2300 kcal (UK), 2370 kcal (Singapore) and 2274 kcal (Mount Kinabalu), and mean daily insulin doses were 54 U (UK), 40 U (Singapore) and 47 U (Mount Kinabalu). Despite markedly increased energy expenditure during the climb [4202 kcal (Mount Kinabalu) vs. 2948 kcal (UK) and 2662 kcal (Singapore)], mean blood glucose was considerably higher during the trek up Mount Kinabalu [13.2 ± 5.9 mmol/l, vs. 7.9 ± 3.8 mmol/l (UK) and 8.6 ± 4.0 mmol/l (Singapore)].

CONCLUSION

Marked unexpected hyperglycaemia occurred while trekking on Mount Kinabalu, despite similar calorie consumption and insulin doses to control conditions. Because of the risk of unexpected hyperglycaemia in these conditions, we recommend that patients embarking on similar activity holidays undertake frequent blood glucose monitoring.

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.

Does careful glycemic control improve aerobic capacity in subjects with type 1 diabetes?

Existing evidence shows that some, but not all, individuals with type 1 diabetes are capable of the same aerobic capacity as matched nondiabetic subjects. Poor glycemic control impairs pulmonary, cardiac, and vascular responses to exercise. This review examines how careful glycemic control affects these responses and may independently improve aerobic capacity.

Medication and dosage considerations in the prophylaxis and treatment of high-altitude illness

With increasing numbers of people traveling to high altitude for work or pleasure, there is a reasonable chance that many of these travelers have preexisting medical conditions or are receiving various medications at the time of their sojourn. As with all travelers to high altitude, they are at risk for altitude illnesses such as acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema. While there are clear recommendations for pharmacologic measures to prevent or treat these illnesses, these recommendations are oriented toward healthy individuals and do not take into account the presence of preexisting medical conditions. In this review, we consider how the choice and dose of the medications used in the management of altitude illness-acetazolamide, dexamethasone, nifedipine, tadalafil, sildenafil, and salmeterol-are affected by a patient's underlying medical conditions. We discuss the indications and current dosing recommendations for individuals without underlying disease, and then consider how drug selection or dosing regimens will be affected by the presence of renal insufficiency, hepatic insufficiency, other important medical conditions, and the potential for serious drug interactions. We include comments about interactions with antimalarial medications and antibiotics used in the treatment of traveler's diarrhea, as well as the safety of use during pregnancy. By giving these issues adequate consideration, clinicians can increase the chances that properly evaluated patients with underlying medical conditions will enjoy a safe trip to high altitude.