For use alongside - Guidance For: Prone Positioning in Adult Critical Care, ICS November 2019. 

In the light of recent safety alerts:

On the use of HME Filters during the COVID-19 pandemic and the increased likelihood of ventilator circuits and HME filters becoming waterlogged compromising ventilation please see the following FICM advice.

MHRA alert: Anaesthetic machines: off-label use during the COVID-19 pandemic (MDA/2020/012) which advised regularly checking for condensate build-up, which may affect functionality.

Further incidents relating to obstruction to ventilation due to waterlogging of ventilator circuits and HME filters during repositioning patients, we advise that prior to turning patients (either prone or supine) the HME filters and in particular the ventilator circuits are checked for water and the airway pressures noted. HME filter waterlogging MUST be considered as part of a cannot ventilate scenario.