Fig. 1.

Different ventilator circuit assemblies to reduce viral spreading. (a) Ventilator using double circuit with an integrated expiratory valve. The filter* must be interposed between the expiratory arm and the ventilator. (b) Ventilator using single-limb circuit with an active expiratory valve: the filter* must be interposed between the mask and the expiratory valve. (c) Ventilator using single limb circuit with intentional leaks. Not-vented mask must be preferred if available. In this case a deported exhalation port (Whisper Swivel or similar) must be added. The filter* must be interposed between the mask and the deported exhalation port. If a non-vented mask is not available an alternative is to seal the intentional leak of the vented mask. In the last case caution must be taken not to block anti-asphyxia valve. I: inspiratory arm; E: expiratory arm. * There are not published studies comparing the efficacy of different filters.