Outcomes
Primary outcome: Tracheostomy use in critical care patients. Use of a tracheostomy was recorded if the Office of Population Censuses and Surveys Classification of Interventions and Procedures version 4 (OPCS-4) code E42- was used anywhere in the HES record of procedures.
Secondary outcomes: In-hospital mortality, length of hospital stay, length of critical care stay and tracheostomy malfunction. In these analyses, tracheostomy use was treated as the primary exposure variable. Mortality was taken from the Office for National Statistics (ONS) date linked to HES data at a patient level. An in-hospital death was recorded if the date of death was the same as or +/- one day of the date of hospital discharge recorded in HES. Tracheostomy malfunction was recorded where the ICD-10 code J950 was used.