Strengths and limitations
HES data covers all NHS-funded hospital activity in England. As such they are the most complete and detailed record of hospital activity in England related to COVID-19. The eight-month study period allowed us to look at temporal trends over an extended period.
However, as with any administrative dataset, there are limitations in using HES data. HES relies on individual hospital trusts compiling data accurately and in a consistent manner. As such, some patients who underwent a tracheostomy may not have been coded as such and so number of tracheostomies reported here is likely to be an under-estimate. Furthermore, tracheostomy complications are likely to be underreported due to coding limitations.19 However, we have no reason to suspect that our data are systematically biased in terms of temporal trends or the profile of patients receiving tracheostomy.