Mitigating Fugitive Aerosols During Aerosol Delivery via High-Flow Nasal Cannula Devices

Guidance on Mitigating the Risk of Transmitting Respiratory Infections During Nebulization by the COPD Foundation Nebulizer Consortium

BACKGROUND

Nebulizers are used commonly for inhaled drug delivery. Because they deliver medication through aerosol generation, clarification is needed on what constitutes safe aerosol delivery in infectious respiratory disease settings. The COVID-19 pandemic highlighted the importance of understanding the safety and potential risks of aerosol-generating procedures. However, evidence supporting the increased risk of disease transmission with nebulized treatments is inconclusive, and inconsistent guidelines and differing opinions have left uncertainty regarding their use. Many clinicians opt for alternative devices, but this practice could impact outcomes negatively, especially for patients who may not derive full treatment benefit from handheld inhalers. Therefore, it is prudent to develop strategies that can be used during nebulized treatment to minimize the emission of fugitive aerosols, these comprising bioaerosols exhaled by infected individuals and medical aerosols generated by the device that also may be contaminated. This is particularly relevant for patient care in the context of a highly transmissible virus.

RESEARCH QUESTION

How can potential risks of infections during nebulization be mitigated?

STUDY DESIGN AND METHODS

The COPD Foundation Nebulizer Consortium (CNC) was formed in 2020 to address uncertainties surrounding administration of nebulized medication. The CNC is an international, multidisciplinary collaboration of patient advocates, pulmonary physicians, critical care physicians, respiratory therapists, clinical scientists, and pharmacists from research centers, medical centers, professional societies, industry, and government agencies. The CNC developed this expert guidance to inform the safe use of nebulized therapies for patients and providers and to answer key questions surrounding medication delivery with nebulizers during pandemics or when exposure to common respiratory pathogens is anticipated.

RESULTS

CNC members reviewed literature and guidelines regarding nebulization and developed two sets of guidance statements: one for the health care setting and one for the home environment.

INTERPRETATION

Future studies need to explore the risk of disease transmission with fugitive aerosols associated with different nebulizer types in real patient care situations and to evaluate the effectiveness of mitigation strategies.

Efficacy of a surgical mask during high-flow nasal oxygen therapy in preventing aerosol dispersion: a randomized controlled study

PURPOSE

It is not clear whether or not high-flow nasal oxygenation used in patients with severe respiratory tract infection, or coughing, increases the risk of infection to the healthcare personnel, and whether or not applying a surgical mask to the patient's face or treating the patient in a negative-pressure room can reduce the risk.

METHODS

In a randomized crossover design, we compared in 50 participants receiving high-flow nasal oxygenation, the aerosol counts measured at approximately 20 cm above the participant's mouth in 32 different circumstances (with or without coughing, with or without wearing a surgical mask, at four different flow rates of oxygenation, in a positive- or negative-pressure operating room).

RESULTS

In a positive-pressure room, a surgical mask significantly decreased the aerosol counts during coughing (P = 0.0005), or during no coughing (P = 0.009), under high-flow nasal oxygenation (at 60 l.min-1). In the negative-pressure room, the aerosol count was significantly lower than in the positive-pressure room, for all the circumstances (all P < 0.001), and a surgical mask significantly decreased the aerosol counts during coughing (P = 0.047) but not during no coughing (P = 0.60).

CONCLUSION

In conclusion, treating a patient in a negative-pressure room, or applying a surgical mask, during high-flow nasal oxygenation (with the flow rate of 60 l.min-1) would inhibit, but would not completely prevent, dispersion of aerosols by coughing.

In vitro model for investigating aerosol dispersion in a simulated COVID-19 patient during high-flow nasal cannula treatment

The use of high-flow nasal cannula in the treatment of COVID-19 infected patients has proven to be a valuable treatment option to improve oxygenation. Early in the pandemic, there were concerns for the degree of risk of disease transmission to health care workers utilizing these treatments that are considered aerosol generating procedures. This study developed an in vitro model to examine the release of simulated patient-derived bioaerosol with and without high-flow nasal cannula at gas flow rates of 30 and 50 L/min. Aerosol dispersion was evaluated at 30 and 90 cm distances. Reduction of transmission risk was assessed using a surgical facemask on the manikin. Results indicated that the use of a facemask facilitated a 94-95% reduction in exhaled aerosol concentration at 30 cm and 22-60% reduction for 90 cm distance across both gas flow rates. This bench study confirms that this in vitro model can be used as a tool to assess the risk of disease transmission during aerosol generating procedures in a simulated patient and to test factors to mitigate the risk.

Aerosol-Generating Procedures and Virus Transmission

During the early phase of the COVID-19 pandemic, many respiratory therapies were classified as aerosol-generating procedures. This categorization resulted in a broad range of clinical concerns and a shortage of essential medical resources for some patients. In the past 2 years, many studies have assessed the transmission risk posed by various respiratory care procedures. These studies are discussed in this narrative review, with recommendations for mitigating transmission risk based on the current evidence.