Funding for this research was provided by:
Received: 1 October 2020
Accepted: 19 October 2020
First Online: 18 December 2020
Ethics approval and consent to participate
: The Institutional Review Board of the AMC approved both the protocol of the parent study, and also this preplanned substudy (2014_088). Written informed consent was obtained before participation in the parent study; collection of endotracheal tubes after tracheal extubations did not require informed consent.
: Not applicable.
: The authors declare that they have no competing interests.