Respiratory cross-infection in non-invasive ventilation devices

Non-invasive ventilation (NIV) is considered an aerosol-generating procedure (AGP), yet the extent of the risk of airborne pathogen transmission remains uncertain. To address this, we conducted three studies assessing bioaerosol generation, device contamination, and cough-related dispersion during NIV.

Studies 1 and 2 used a purpose-designed rig with high-efficiency particulate air (HEPA)-filtered supply flow, ensuring detection of particles generated only by the NIV system. Study 3 uses a flow-tunnel rig to compare aerosol dispersion during NIV, sham NIV, tidal breathing, and uncovered coughing.

In the controlled laboratory setting (study 1), NIV-generated aerosol particles were measured. Viable Pseudomonas aeruginosa was detected when inoculum concentrations were ≥1 × 10⁵ colony-forming unit (cfu)/mL, and the use of inline antibacterial filters prevented bacterial emission. Study 2 demonstrated low risk of NIV device contamination (1 in 10) during short-term use. While in study 3, NIV with therapeutic pressure generated higher physical aerosol counts than tidal breathing or sham NIV but less than that with uncovered coughing. Among 13 participants, viable pathogens were detected in uncovered coughs from seven (54%) participants (median: 9, interquartile range: 3-12 cfu), while only one participant had a positive result during NIV (2 cfu with sham and 3 cfu with therapeutic NIV).

Our findings demonstrate that NIV devices may be contaminated after use and can aerosolize viable bacteria. While the World Health Organization classifies NIV as a high-risk AGP, we demonstrate low likelihood of infectious particle release, particularly when effective interfaces, leak control, and robust infection prevention measures are implemented.