Changes in Altitude Cause Unintended Insulin Delivery From Insulin Pumps Mechanisms and implications

OBJECTIVEdChildren and adults with type 1 diabetes who receive insulin pump therapy have reported hypoglycemia during air travel. We studied the effects of atmospheric pressure on insulin pump delivery. RESEARCHDESIGNANDMETHODSdTen insulin pumpswere connected to capillary tubes. The effects of changes in ambient pressure on insulin delivery, bubble formation, bubble size, and cartridge plunger movement were analyzed. RESULTSdDuring a flight (200 mmHg pressure decrease), excess insulin delivery of 0.623% of the cartridge volume occurred (P, 0.001, Student t test). In hypobaric chamber studies, bubbles developed in the insulin when the pressure decreased and displaced the insulin out of the cartridge. Pre-existing bubbles changed in size consistent with Boyle law. Cartridge plunger movement did not occur in normal flight conditions but did occur when catastrophic plane depressurization was mimicked. CONCLUSIONSdAtmospheric pressure reduction causes predictable, unintended insulin delivery in pumps by bubble formation and expansion of existing bubbles. Diabetes Care 34:1932–1933, 2011 A10-year-old girl with well-controlledtype 1 diabetes managed with in-sulin pump therapy developed re-current hypoglycemia 60 to 90 min after commencing commercial air travel. Upon direct inquiry, we are now aware of 50 children and adults using insulin pumps who experience this phenomenon. In 1994, Aanderud et al. (1) demon-strated that insulin pumps delivered “more insulin than the set rate during de-compression. ” At sea level, the ambient pressure is 760 mmHg (1 atmosphere). When commercial planes ascend to 40,000 feet, the cabin pressure decreases by 200 mmHg to 560 mmHg (cabin pres-sure equivalent of 8,000 feet) (2). The ob-jective of this study was to investigate the effects of pressure changes during airplane flight on insulin pump delivery