Breathing system and heat and moisture exchangers filters

Abstract

Breathing system filters (i.e., inspiratory filters and expiratory filter) and heat and moisture exchange filters (HMEF) can be used for blocking the release of viruses and bacteria from ventilators. Filters are divided into mechanical and electrostatic filters. Mechanical filters have a high hydrophobic capacity and can maintain high filtration efficiency, even under wet conditions. Some electrostatic filters have a low hydrophobic capacity, which may reduce filtration efficiency. Therefore, a mechanical filter is used as the expiratory filter while using a heated humidifier. Since mechanical filters have a large amount of dead space, electrostatic filters are often used for HMEFs. HMEFs with electrostatic filters should be used in combination with an expiratory filter because filtration efficiency will decrease if the moisture mixed from the HME side also enters the filter side. Furthermore, it is necessary to pay particular attention to the increase in expiratory resistance and devise ways to reduce the mixing of water into the filter housing to extend the filter replacement interval.