Suggested filter placement of filters to protect patient, anesthesia machine, and gas analyzer from viral cross contamination

Suggested placement of filters to protect patient, anesthesia machine, and gas analyzer from viral cross contamination. In adults with a tidal volume greater than 300 mL, the best viral filtration is obtained with one pleated mechanical filter placed at the expiratory limb and another placed at the airway. Gas for analysis is sampled from the machine side of the airway filter. In children or adults with tidal volumes greater than 30 mL, an appropriately sized electrostatic filter (with or without HME component) can be substituted at the airway to decrease the dead space added by a mechanical filter. This may be the best configuration for long-term ventilation because mechanical pleated filters tend to become obstructed quickly when placed at the airway. In neonates with tidal volumes less than 30 mL (or in children if an appropriately low-volume electrostatic filter is not available) the airway filter is replaced with a mechanical filter in the inspiratory limb. In this configuration, the gas analyzer is only protected by filters in the water trap (not shown). Mechanical pleated filters provide the best filtration, which improves with humidity, but tend to have a large internal volume and easily become obstructed by secretions and condensed humidity. They may also be less available during viral pandemics. Electrostatic filters have a lower viral filtration efficiency (VFE), which gets worse as they become wet from humidified patient gases. However, they are less prone to obstruction, are more available, and can be made with a smaller internal volume.