Personal Insulin Pump With Predictive Low Glucose Management Technology at High Altitude

These days, compared to days gone by, patients with type 1 diabetes mellitus (T1DM) are becoming more and more physically active, with some choosing to partake in extreme sports such as high-altitude mountain trekking. Although numerous high-altitude mountain expeditions including patients with T1DM have been reported,^1,2 diabetic device performance at high altitude has not been thoroughly assessed. The devices to which we refer include glucose meters, continuous glucose monitoring (CGM) systems, and insulin pumps, especially newest ones.^3,4 Here, we present the case of a T1DM patient, and the pump with predictive low glucose management technology user, who climbed Aconcagua—a mountain 6962 meters above sea level. The data provided below are based on both the patient’s report and downloads from the insulin pump.

The case study patient is a 42-year-old male, who has been suffering from T1DM for 20 years. His BMI at the time of the study was 24 kg/m², and his last available HbA1c was 7.2%. The patient is a very active individual, who regularly runs marathons and participates in mountain runs. After undergoing treatment with multiple daily insulin injections for many years and being reluctant to insulin pump therapy, he chose to switch to the Medtronic MiniMed 640G (Medtronic MiniMed, Northridge, California, USA) insulin pump with implemented SmartGuard® technology, with protection against hypoglycemia being his primary motivator. ⁵ The switch was made 3 months prior to his 7-day expedition to Aconcagua. He was informed that the performance of the predictive low glucose management technology at high altitude had not been tested yet; however, he chose to stay on the pump and carry backup insulin in pens with him during the trek.

He began his climb at 2950 meters, and at the end of the first day he reached Confuluencia Camp at 3400 meters. His mean blood glucose level during that time stayed around 120 mg/dl. Following acclimatization, he trekked to de Mulas Camp at 4300 meters, where he underwent a medical examination (assessment of mood, heart rate, pulse, oxygen saturation of arterial blood). During the night, after reaching de Mulas Camp, he suffered a headache and experienced fluctuations in blood glucose; however, he did not experience a single episode of hypoglycemia (defined as blood glucose level below 70 mg/dL). Over the days to follow, he climbed Nido de Condores (5550 meters), Plaza Cólera (5970), and on the 7th day he reached Aconcagua. The final episode of activation of predictive insulin delivery suspension was recorded at an altitude of 5600 meters. The patient recalls that he experienced and addressed a slightly elevated blood sugar level (between 140 and 200 mg/dL) later on; since the “suspend before low” option was set at 70 mg/dL, the SmartGuard had “no chance” to act. According to the patient, the CGM system performed well, and showed no significant discrepancy between data from the CGM system and hand blood glucose meter (Contour® Plus Link 2.4, Ascensia, Basel, Switzerland).

During the 7-day expedition the patient experienced just 1 episode of hypoglycemia (blood sugar level of 61 mg/dL); the predictive insulin delivery suspension was activated 11 times.

In summary, the insulin pump with predictive low glucose management technology performed well at high altitude; however, further studies are needed before any recommendation for its usage at altitude can be made.