Studies of critically-ill adults or paediatric patients who were transferred from one hospital to another for treatment not available at the referring hospital because of lack of beds, expertise or service were eligible. Studies needed to clearly described personnel who accompanied patients and needed to report mortality and length of hospital or intensive care unit stay at the receiving hospital. Studies of infants, neonates and pregnant women were excluded. The review defined specialist transport personnel as dedicated transport crews or the addition of critical care staff based at the receiving hospital; other personnel who accompanied patients (including house staff from the referring hospital) were defined as non-specialist personnel. Studies that did not have comparable control groups were excluded (details were reported).
Included studies compared tertiary-based transport teams (including at least one person with specialist training in transport medicine) with ordinary ambulance crews with or without staff from the referring hospital or compared different grades of specialist teams. Where reported, transport was by surface or by air. Studies included patients transported from the scene of the injury (primary transport). Most studies involved either adults only or patients of all ages; one study was of paediatric patients. All studies included patients with different conditions and illness severity.
One reviewer conducted the searches and identified potentially relevant studies. Two reviewers then independently selected studies that met inclusion criteria from the full reports. Disagreements were resolved by consensus with the help of a third reviewer.