title: Air transport of patients with intracranial air: computer model of pressure effects.
abstract: BACKGROUND
  Air is commonly trapped within the skull in patients who have been treated for trauma or intracranial hemorrhage. In Sweden, when such a patient is transported by air ambulance it is standard procedure to maintain sea-level pressure in the cabin to prevent increased intracranial pressure (ICP). However, this type of flight operation is more difficult and expensive. Maintenance of sea-level cabin pressure is not common practice all over the world, and the criteria supporting the choice of pressurization during transport are inadequate and in need of evaluation. The purpose of this study was to develop and evaluate a model to simulate the influence of intracranial air on ICP during air transport.
  
  
  METHODS
  We identified an existing nonlinear model of the cerebral spinal fluid and intracranial pressure dynamics, then added intracranial air as a new component and evaluated the model through simulations.
  
  
  RESULTS
  The model behaved as expected, and the simulations indicated that under normal flying conditions with decreased cabin pressure the initial intracranial air volume will increase by approximately 30% at normal maximum cabin altitude, 8000 ft. The increase in ICP depends upon both the initial air volume and the rate of change in cabin altitude. For an intracranial air volume of 30 ml the estimated worst-case increments of ICP from sea level to maximum altitude would be from 10 mm Hg to 21.0 mm Hg, or from 20 mm Hg to 31.8 mm Hg.
  
  
  CONCLUSIONS
  Our results support the need for maintenance of sea-level pressure during air transport of patients with suspected intracranial air, since an ICP increment could potentially impair the patient's clinical condition.
authors.affiliation: Department of Biomedical Engineering and Informatics, Umeå University Hospital, Umeå, Sweden. nina.andersson@vll.se
authors.forename: Nina
authors.initials: N
authors.lastname: Andersson
authors.forename: Helena
authors.initials: H
authors.lastname: Grip
authors.forename: Peter
authors.initials: P
authors.lastname: Lindvall
authors.forename: Lars-Owe D
authors.initials: LO
authors.lastname: Koskinen
authors.forename: Helge
authors.initials: H
authors.lastname: Brändström
authors.forename: Jan
authors.initials: J
authors.lastname: Malm
authors.forename: Anders
authors.initials: A
authors.lastname: Eklund
mesh_terms: D017732:Air Ambulances; D000399:Air Pressure; D002543:Cerebral Hemorrhage / Q000150:complications; D006259:Craniocerebral Trauma / Q000150:complications; D006801:Humans; D008962:Models, Theoretical; D011007:Pneumocephalus / Q000503:physiopathology*; D012307:Risk Factors; D014187:Transportation of Patients