NEW YORK: Changes in cabin pressure during flights may cause insulin pumps to deliver too much or too little of the medication, possibly putting extremely sensitive diabetics at risk, according to a study.

Researchers led by Bruce King at John Hunter Children's Hospital in Newcastle, Australia wrote in the journal Diabetes Care decided to investigate after learning of a 10-year-old girl with type 1 diabetes whose blood sugar got too low an hour after takeoff.

After hearing of other diabetics who used insulin pumps - which are meant to deliver insulin throughout the day, usually to people with type one diabetes - having a similar experience, they put ten insulin pumps on a commercial flight.

During takeoff, when air pressure was decreasing, the pumps delivered about 1 to 1.4 extra units of insulin on average.

During descent, when pressure was increasing, some insulin was sucked back into the pumps, causing them to give out too little insulin, by less than one unit.

“Atmospheric pressure reduction causes predictable, unintended insulin delivery in pumps by bubble formation and expansion of existing bubbles,” King and his team wrote.

King added in an email to Reuters Health: “Any person using an insulin pump should be aware that big pressure changes can cause this effect.” Other diabetes researchers, though, said the issue was infrequent and unlikely to cause problems for most diabetics.

“It's certainly not a frequent and recurring problem I hear about from patients who fly,” said Robert Cohen, an endocrinologist at the University of Cincinnati College of Medicine, who was not involved in the study.

“The people who are very sensitive to small changes in doses are the ones who are going to be most sensitive to this. People who are on large doses or are not very sensitive...are far less likely to be affected by this.”

King and his team recommended disconnecting the pump before takeoff and landing and making sure there are no air bubbles in the insulin before reconnecting it, but Cohen said it was extremely important that people understand how to carry this out correctly.

He added that patients should check with their doctors to see if this concern applies to them, and if so, how to safely deal with it. The pumps used in the study were made by Animas and Medtronic, which wrote in a joint statement to Reuters Health: “Many factors affect blood glucose during travel and the effect of small does variations over the course of a plane flight is unlikely to be clinically significant.

“However, we are both continuing to further explore this subject.”