By J. Brady Scott, PhD, RRT, RRT-ACCS, AE-C, FAARC, FCCP
Associate Professor, Program Director, College of Health Sciences, Department of Cardiopulmonary Sciences – Division of Respiratory Care, Rush University, Chicago
SYNOPSIS: When appropriate precautions (adequate room ventilation, use of total face masks, dual-limb circuits, and filters) are used, environmental contamination of SARS-CoV-2 during noninvasive ventilation is low. Noninvasive ventilation does not appear to increase the risk of COVID-19 infection for healthcare workers or patients when precautions are applied.
SOURCE: Dell’Olio A, Vocale C, Primavera A, et al. Environmental contamination by SARS-CoV-2 during noninvasive ventilation in COVID-19. Respir Care 2023;68:1-7.
Early in the COVID-19 pandemic, there was reasonable concern about aerosol transmission associated with noninvasive respiratory support. The situation led to early intubation and an overall shortage of mechanical ventilators.1 Most research suggests that noninvasive respiratory support, such as high-flow nasal cannula (HFNC) oxygen therapy and noninvasive ventilation (NIV), does not increase the risk of viral transmission compared to conventional oxygen therapy or invasive mechanical ventilation.1-4 That said, at least one study demonstrated that 10% of healthcare workers caring for patients with COVID-19 with NIV were infected with the virus.5 Because questions remain about viral spread and surface contamination during the use of NIV for patients with COVID-19, Dell’Olio et al sought to understand this issue better. They hypothesized that using sufficient room ventilation, total face masks, dual-limb circuits, and filters would lead to no evidence of SARS-CoV-2 on surfaces close to patients using NIV.
This was a prospective, observational, single-center study performed in a COVID-19-dedicated intensive care unit (ICU) between April 2020 and March 2021. Inanimate surfaces in the room were sampled at different distances from the source (patient’s mouth). The distances were 50 cm (head lateral bed rail), 80 cm (body lateral bed rail), 150 cm (table bed rail), and 200 cm (1-m-high upside-down bin on the floor). Each room had negative pressure with 10 air changes per hour. NIV was delivered via total face masks (Respironics PerforMax, Philips, Amsterdam, the Netherlands), dual-limb circuits, and with filters in place between both ventilator ports and the ventilator-side limbs of the circuits. After the surfaces were disinfected, samples were collected immediately (negative control) and at six, 12, and 24 hours. SARS-CoV-2 was detected with a real-time reverse transcriptase-polymerase-chain-reaction (RT-PCR) test.
Overall, a total of 16 bed stations were analyzed for the presence of SARS-CoV-2 for a total of 256 environmental swabs. No patient included in the study underwent any aerosol-generating procedure (AGP) other than NIV, as stated by the authors. Pressure support was used during NIV, and HFNC oxygen therapy was used any time subjects were disconnected during the 24-hour period of observation. When analyzed, none of the 256 samples were positive for SARS-CoV-2. Additionally, the samples were analyzed for ribonuclease (RNase) to identify other genetic material on the swabbed surfaces. Less than 10% (8.2%) of the samples contained genomic materials that indicated contamination from sources other than SARS-CoV-2. Positive control samples were taken from the inside of the NIV mask, and results were positive for both SARS-CoV-2 and RNase.
COMMENTARY
When proper safeguards are taken, it appears that NIV can be delivered safely and poses no additional risk to healthcare workers and patients. It is hoped that the findings of this study and others will increase healthcare workers’ confidence that NIV can be provided safely for patients with COVID-19. When precautions can be applied, decisions about NIV vs. invasive mechanical ventilation for respiratory support can be based on patient factors instead of concern about environmental contamination.
In a review article by Li et al,6 the authors suggested that NIV and continuous positive airway pressure (CPAP) should no longer be considered AGPs. Similarly, in the editorial that accompanied the Dell’Olio study,1 Li also stated that the pandemic helped the medical community better differentiate aerosol transmission risks and what should be classified as an AGP. Li et al6 stated that procedures classified as AGPs provoke cough and produce infectious bioaerosol particles that exceed those produced during baseline activities, such as breathing and talking. Examples of those procedures include intubation, bronchoscopy examination, tracheostomy open-suctioning, and nasal pharyngeal suctioning. Instead of being called an AGP, NIV is better classified as an aerosol-dispersing procedure. NIV, as an aerosol-dispersing procedure, does not generate additional bioaerosol.6 This distinction is essential, since research has shown that viral load, aerosol particle size, and speed/distance of viral transport affect how significant aerosol dispersion may be.6
Cumulatively, studies have provided a blueprint for the safe delivery of NIV for patients with COVID-19. The risk of transmission can stay low if non-vented masks, dual-limb circuits filtered at the exhalation port, single-limb circuits with filters placed at the exhalation port or between the mask and exhalation port, well-ventilated rooms (negative pressure rooms), and personal protective equipment are used.6 Dell’Olio et al added to the literature by providing direct evidence that aerosol transmission risks can be mitigated during NIV use. This information is relevant as we still care for patients requiring noninvasive respiratory support due to COVID-19 infection. It also applies in the post-pandemic era as we plan to simultaneously provide respiratory support for patients while providing a safe environment for healthcare workers and other patients.
REFERENCES
- Li J. Optimizing respiratory care for patients while protecting ourselves. Respir Care 2023;68:167-168.
- Roca O, Pacheco A, Rodon J, et al. Nasal high-flow oxygen therapy in COVID-19 patients does not cause environmental surface contamination. J Hosp Infect 2021;116:103-105.
- Thuresson S, Fraenkel CJ, Sasinovich S, et al. Airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in hospitals: Effects of aerosol-generating procedures, HEPA-filtration units, patient viral load, and physical distance. Clin Infect Dis 2022;75:e89-e96.
- Li J, Fink JB, Elshafei AA, et al. Placing a mask on COVID-19 patients during high-flow nasal cannula therapy reduces aerosol particle dispersion. ERJ Open Res 2021;7:00519-2020.
- Franco C, Facciolongo N, Tonelli R, et al. Feasibility and clinical impact of out-of-ICU noninvasive respiratory support in patients with COVID-19-related pneumonia. Eur Respir J 2020;56:2002130.
- Li J, Alolaiwat A, Fink JB, Dhand R. Aerosol-generating procedures and virus transmission. Respir Care 2022;67:1022-1042.
