title: A prospective observational study of the association between cabin and outside air temperature, and patient temperature gradient during helicopter transport in New South Wales.
abstract: The prevalence of hypothermia in patients following helicopter transport varies widely. Low outside air temperature has been identified as a risk factor. Modern helicopters are insulated and have heating; therefore outside temperature may be unimportant if cabin heat is maintained. We sought to describe the association between outside air, cabin and patient temperature, and having the cabin temperature in the thermoneutral zone (18-36°C) in our helicopter-transported patients. We conducted a prospective observational study over one year. Patient temperature was measured on loading and engines off. Cabin and outside air temperature were recorded for the same time periods for each patient, as well as in-flight. Previously identified risk factors were recorded. Complete data was obtained for 133 patients. Patients' temperature increased by a median of 0.15°C (P=0.013). There was no association between outside air temperature or cabin temperature and patient temperature gradient. The best predictor of patient temperature on landing was patient temperature on loading (R2=0.86) and was not improved significantly when other risk factors were added (P=0.63). Thirty-five percent of patients were hypothermic on loading, including those transferred from district hospitals. No patient loaded normothermic became hypothermic when the cabin temperature was in the thermoneutral zone (P=0.04). A large proportion of patients in our sample were hypothermic at the referring hospital. The best predictor of patient temperature on landing is patient temperature on loading. This has implications for studies that fail to account for pre-flight temperature.
authors.affiliation: Anaesthetist, Aeromedical and Retrieval Service, Ambulance Service New South Wales, Sydney, New South Wales.
authors.forename: M
authors.initials: M
authors.lastname: Miller
authors.affiliation: Staff Specialist, Aeromedical and Retrieval Service, Ambulance Service New South Wales, New South Wales, Sydney Medical School, Sydney University, Sydney, New South Wales.
authors.forename: C
authors.initials: C
authors.lastname: Richmond
authors.affiliation: Research Coordinator, Aeromedical and Retrieval Service, Ambulance Service New South Wales, School of Molecular Bioscience, University of Sydney, Sydney, New South Wales.
authors.forename: S
authors.initials: S
authors.lastname: Ware
authors.affiliation: Medical Director, Aeromedical and Retrieval Service, Ambulance Service New South Wales, Sydney, New South Wales.
authors.forename: K
authors.initials: K
authors.lastname: Habig
authors.affiliation: Staff Specialist, Aeromedical and Retrieval Service, Ambulance Service New South Wales, Sydney Medical School, Sydney University, Sydney, New South Wales.
authors.forename: B
authors.initials: B
authors.lastname: Burns
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017732:Air Ambulances; D001831:Body Temperature / Q000502:physiology*; D005260:Female; D006801:Humans; D007035:Hypothermia / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009517:New South Wales; D011446:Prospective Studies; D012307:Risk Factors; D013696:Temperature; D014187:Transportation of Patients / Q000379:methods; D055815:Young Adult
keywords: helicopter; hypothermia; inter-hospital transfer; temperature