title: Changes in altitude cause unintended insulin delivery from insulin pumps: mechanisms and implications.
abstract: OBJECTIVE
  Children 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.
  
  
  METHODS
  Ten insulin pumps were connected to capillary tubes. The effects of changes in ambient pressure on insulin delivery, bubble formation, bubble size, and cartridge plunger movement were analyzed.
  
  
  RESULTS
  During 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.
  
  
  CONCLUSIONS
  Atmospheric pressure reduction causes predictable, unintended insulin delivery in pumps by bubble formation and expansion of existing bubbles.
authors.affiliation: University of Newcastle,Newcastle, New South Wales, Australia. bruce.king@hnehealth.nsw.gov.au
authors.forename: Bruce R
authors.initials: BR
authors.lastname: King
authors.forename: Peter W
authors.initials: PW
authors.lastname: Goss
authors.forename: Megan A
authors.initials: MA
authors.lastname: Paterson
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Crock
authors.forename: Donald G
authors.initials: DG
authors.lastname: Anderson
mesh_terms: D000531:Altitude; D001274:Atmospheric Pressure; D006801:Humans; D007328:Insulin / Q000008:administration & dosage; D007332:Insulin Infusion Systems / Q000592:standards*
chemical_list: D007328:Insulin