title: Unintended Insulin Pump Delivery in Hyperbaric Conditions.
abstract: Unintended pump insulin delivery was reported to occur as a consequence of decreased atmospheric pressure, probably mediated by air bubble formation and the expansion of existing bubbles. This observation has been used to explain some hypoglycemic episodes occurring in patients on insulin pump treatment in between 1 and 1 h 45 min after the flight takeoff. New models of insulin pumps have been introduced in the market, most of them are waterproof certified. It is not clear if in these new pumps the influence of atmospheric pressure changes on the insulin delivery is still present. Moreover, there are no evidences related to the insulin pump operations in hyperbaric conditions, like as during diving activities. Our aim is therefore to verify the eventual variation of insulin pump delivery determined by atmospheric pressure changes in hyperbaric conditions.
  
  
  
  Three new models of insulin pumps were tested in hyperbaric conditions at a flow rate of 2 U/h.
  
  
  
  Atmospheric pressure variation affected pump insulin release. An increase in the atmospheric pressure from 1 to 1.3 atmosphere (ATA) induced a decrease of pump basal insulin release (about -0.2 U/10 min); conversely, when the atmospheric pressure returned from 1.3 to 1 ATA, an unintended insulin delivery was observed (about +0.3 U/10 min). This phenomenon appeared to be independent of the insulin pump rate and dependent on the presence of air bubbles within the insulin tube setting and cartridge.
  
  
  
  Unintended insulin delivery driven by atmospheric pressure changes in hyperbaric conditions occurred in the new insulin pumps available. Patients should pay attention to possible variation of insulin rate during the flight or during diving activities.
authors.affiliation: 1 Diabetology Unit, Niguarda Hospital , Milan, Italy .
authors.forename: Federico
authors.initials: F
authors.lastname: Bertuzzi
authors.affiliation: 1 Diabetology Unit, Niguarda Hospital , Milan, Italy .
authors.forename: Basilio
authors.initials: B
authors.lastname: Pintaudi
authors.affiliation: 1 Diabetology Unit, Niguarda Hospital , Milan, Italy .
authors.forename: Matteo
authors.initials: M
authors.lastname: Bonomo
authors.affiliation: 2 Hyperbaric Treatment Unit, Niguarda Hospital , Milan, Italy .
authors.forename: Fabio
authors.initials: F
authors.lastname: Garuti
mesh_terms: D001274:Atmospheric Pressure; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage*; D007328:Insulin / Q000008:administration & dosage*; D007332:Insulin Infusion Systems
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin
keywords: Diabetes management; Hyperbaric chamber; Insulin pump