MADRID —
This phenomenon is due to air bubble formation and reabsorption in the insulin caused by ambient pressure changes in the airplane’s cabin. It has nothing to do with the pump itself and happens with all insulin pumps, including those in hybrid closed-loop systems, Bruce King, MD, said at the European Association for the Study of Diabetes (EASD) 2024 Annual Meeting.
The extent to which this affects people with diabetes who use insulin pumps depends on their dose and insulin sensitivity among other factors, but all who fly should be aware of the possibility and take precautions, particularly with children, Dr. King, a pediatric endocrinologist at John Hunter Children’s Hospital, Newcastle, Australia, told this news organization.
“Basically, the pumps are very safe in flight, but they deliver a little bit of extra insulin when you go up and stop delivery when you come back down again. There are a couple of simple steps that people can take to make sure that they don’t have problems during the flight,” he said.
Specifically, he advised that for pumps with tubing, wearers can disconnect just prior to takeoff and reconnect when the plane reaches cruising altitude, about 20 minutes into the flight. The insulin will still come out, but it won’t be delivered to the person, Dr. King said.
On descent, they can disconnect after landing and prime the line to remove the insulin deficit.
With the Omnipod, which can’t be disconnected, the only solution is to eat a small snack on takeoff. And on landing, eat another small snack such as a banana, and give a bolus for it to overcome the blockage of insulin delivery.
In any case, Dr. King said, “One of the most important things is informing people with diabetes about this effect so they’re aware of it and can act appropriately when they fly.”
Asked to comment, Nicholas B. Argento, MD, a practicing endocrinologist in Columbia, Maryland, and author of the American Diabetes Association’s book, “Putting Your Patients on the Pump,” called the issue a “minor effect,” adding, “While I think it would be reasonable to make those changes ... it seems like a lot of effort for a difference of 0.6 units extra on ascent and 0.5 units less on descent.”
He noted there is a risk that the individual might forget to reattach the pump after 20 minutes, leading to hyperglycemia and even diabetic ketoacidosis. Instead, “one could put the pump on suspend for 1 hour on ascent. That would not stop the extra insulin but would net less insulin during that time period.”
And after descent, “you have to walk a lot in most cases, so I don’t think they need to take this into consideration. So many other factors change in air travel that I don’t think this is a significant enough effect to make the effort.”
A Known Phenomenon, the Manufacturers Are Aware
This phenomenon has been described previously, including by Dr. King in a 2011 Diabetes Care paper. The new research is among a series of experiments funded by the European Union Aviation Safety Agency in collaboration with the pump manufacturers Medtronic (MiniMed), Tandem (t:slim), and Insulet (Omnipod), primarily aimed at establishing safety parameters for airline pilots with insulin-treated diabetes.
Both the Omnipod DASH and Omnipod 5 User Guides include warnings about unintended insulin delivery during flight, and both advise users to check their blood glucose levels frequently while flying.
In a statement, Jordan Pinsker, MD, Chief Medical Officer at Tandem Diabetes Care, told this news organization, “While it has long been known that routine air travel pressure changes can cause minor fluctuations in insulin pump delivery, the impact of these variations have been found to be generally minor as it relates to glycemic control.”
Dr. Pinsker added that the Tandem Mobi user manual includes a warning related to significant pressure changes in specific air travel situations and offers guidance to disconnect. However, “the t:slim X2 pump’s microdelivery technology limits how much extra insulin can get delivered from air pressure changes due to a mechanism between the tubing and the contents of the bag inside the cartridge.”
Medtronic’s user guide says that the 780G system has not been tested at altitudes higher than 10,150 feet.
Hypobaric Chamber Used to Simulate Flight
The study was conducted in vitro, in a hypobaric chamber designed to mimic atmospheric changes during commercial flight. A total of 10 Medtronic MiniMed 780G, 10 Tandem t:slim X2, and six Insulet Omnipod DASH pumps were tested.
The hypobaric chamber was depressurized to 550 mm Hg over a 20-minute ascent, maintained at a 30-minute cruise, followed by a 20-minute descent to ground (750 mm Hg). During the simulated flights, insulin infusion was set at 0.6 units per hour, a rate typical for both adults and children, to allow accurate measurements with multiple flights.
Insulin delivery rates and bubble formation were recorded by attaching infusion sets to open-ended 100 µL capillary tubes against 1-mm grid paper.
Full cartridges — Medtronic: 3 mL, t:slim: 3 mL, and Omnipod: 2 mL — all over-delivered 0.60 units of insulin over a 20-minute ascent compared with delivery at ground level. And during descent, the cartridges under-delivered 0.51 units of insulin.
But if There’s Rapid Decompression…
In a separate protocol, insulin infusion sets without pumps were tested in a simulation of rapid decompression. Insulin delivery during both ascent and descent showed statistically significant differences compared with delivery at ground level (both P < .001). In this scenario, fluid delivery was equivalent to 5.6 units of excess insulin.
Dr. King pointed out that while these are rare events, about 40-50 occur annually. One was the widely publicized Alaska Airlines flight in January 2024 when the door fell off in midair.
Dr. Argento said, “The catastrophic decompression is of note, and I would want patients to be aware of this, but it is asking a lot for someone thinking they are going to die to remember to disconnect as it starts.”
The researchers are investigating this phenomenon further in people, including airline pilots.
Dr. King’s research group has been involved in research with Medtronic, Tandem, and Insulet. Dr. Argento has consulted or been on advisory boards for Eli Lilly Diabetes, Dexcom, Diabeloop, Convatec, and Senseonics and served on the speakers’ bureaus for Boehringer Ingelheim, Dexcom, Eli Lilly Diabetes, MannKind, Novo Nordisk, Xeris, and Zealand Pharma.
A version of this article appeared on Medscape.com.