Healthcare-Associated Infections (HCAIs) and cross-contamination are a significant cause of mortality and morbidity in patients under general anaesthesia or during mechanical ventilation in intensive care.2

In mechanically ventilated patients, the upper airways are bypassed by an artificial airway thus, unlike during normal breathing, inspired gases are not filtered before reaching the lungs. More often these infections are resistant to standard antibiotic therapy and this topic is the cause of increasing public concern.

The incidence of HCAIs increases the hospital care cost of a patient by $10,375 and it increases the length of stay by 3.30 days.3 

Using the right devices in the right way and at the right time, like breathing filters and/or closed suction devices could help healthcare professionals to proactively fight against these infections providing a correct approach and patient treatment.1

When a patient is brought into a hospital with respiratory distress or respiratory failure, the safety of the patient, caregivers, other patients, and even family members is on the line. In busy hospital environments today, it is vital that clinicians control the spread of many contagious virus and bacterials like tuberculosis, HIV-1, pseudomonas aeruginosa and as well other new respiratory pathogens.

Some patients who present with respiratory distress will require ventilation. Ventilator filters can play a key role in protecting the safety anyone entering the environment of patients on mechanical ventilation by reducing the risk of cross contamination.4,5 Filtration can also protect your hospital staff by helping to minimize the inhalation of airborne pathogens and the contamination with bacteria and viruses that can lead to the spread of infection.4.7


Filtration can play a key role in limiting the spread of certain pandemics. But not all filters are created equal.4 Two important considerations when choosing a ventilator filter are:

  • Filter efficiency
  • Whether the filter is integrated and housed in a warmed environment protected from cooler ambient air

Filter efficiency ratings are determined by how a filter performs at the most penetrating particle size (MPPS).7 MPPS refers to the most difficult particles to filter, and they are the particles of greatest concern that could penetrate a filter.4 These particles have become the standard particle size for NIOSH testing of breathing system filters.7

The NIOSH has established three levels of filter efficiency percentage that correspond with three filter classes — N95 (95 percent), N99 (99 percent), and N100 (99.97 percent).6 In filtration, penetration is the percentage of particles that completely pass through the filter.

For example, if 1,000 particles hit a filter and five slip through, the penetration would be 0.5 percent.7 The efficiency is the percentage of particles that are caught by the filter — 99.5 percent in this example.7

Therefore, choosing an N100-rated equivalent filter with 99.97 percent efficiency against 0.3 μm particles like the one used in Vancouver provides the most protection from particles of greatest concern.5,7 The filtration efficiencies posted by many manufacturers include Bacterial Filtration Efficiency or Viral Filtration Efficiency results, often with ratings of 99.99 percent to 99.9999 percent.7 This testing is typically done using 3.0 μm droplets, which are ten times the diameter (and one thousand times the mass or volume) of the MPPS. This makes the results appear impressive but difficult to relate to real world filtration capabilities.7

Other important considerations when choosing a filter include:

  • Whether the filter is integrated
  • How frequently it needs to be changed due to condensation build up
  • The subsequent rise in resistance from condensation build-up


Heated and nonheated filters may have similar filtration performance.5 The difference is in the management of condensation. Nonheated expiratory filters and heat moisture exchanging filters (HMEFs) require routine changing, since accumulated condensation may increase the resistance of these filters.4 With every instance of a filter change, a break in containment — and therefore a risk of pathogen exposure — is introduced.4

A ventilator with an integrated filter in a housing designed to be heated (actively or passively) and protected from ambient air temperatures can help reduce condensation, while allowing any excess water to be accumulated in a collection vial. This water can be easily drained without breaking the patient circuit or exchanging the expiratory filter, and heated filters can be left in use for extended durations before needing to be replaced.4,5 Avoiding the need for routine circuit disconnections to manage water accumulation may enhance a hospital’s infection control efforts.4


  • 1. Zannin E, Veneroni C, Dellaca' R, Mosca F, Gizzi C, Ventura ML. Bacterial-viral filters to limit the spread of aerosolized respiratory pathogens during neonatal respiratory support in a pandemic era. Pediatr Res. 2021;89(6):1322-1325.

  • 2. Alp E, Voss A. Ventilator associated pneumonia and infection control. Ann Clin Microbiol Antimicrob. 2006;5:7. Published 2006 Apr 6.doi:10.1186/1476-0711-5-7

  • 3. Hassan M, Tuckman HP, Patrick RH, Kountz DS, Kohn JL. Cost of hospital-acquired infection. Hosp Top. 2010;88(3):82-89. 

  • 4. Thiessen RJ. The impact of severe acute respiratory syndrome on the use of and requirements for filters in Canada. Respir Care Clin N Am. 2006;12(2):287–306. 

  • 5. Thiessen, RJ. Heated expiratory filtration: lessons from the SARS experience. Published 2007. Accessed Feb. 5, 2020. 

  • 6. Centers for Disease Control and Prevention. NIOSH guide to the selection and use of particulate respirators. Published Jan., 1996. Accessed Feb. 17, 2020. 

  • 7. Thiessen RJ. Filtration of respired gases: theoretical aspects. Respir Care Clin N Am. 2006;12(2):183–201.