In a matter of weeks, a novel coronavirus named SARS-CoV-2, and the resulting illness, COVID-19, has caused a worldwide pandemic. As countries around the world ration supplies and national stockpiles of ventilators are being commissioned, it is worth discussing the role of noninvasive ventilation (NIV) as it pertains to patients with severe illness due to COVID-19.
Many guidelines are recommending against the use of noninvasive ventilation in patients with COVID-19, for two reasons:
- NIV can result in an increase risk to hospital staff.
- NIV may not be helpful and may cause harm to patients.
Let’s talk about these points in a little more detail.
Can the use of NIV increase the risk of exposure for staff?
Let’s first deal with staff safety and the risk of aerosol-based transmission to health care workers.
Some reports have stated that SARS-CoV-2 can remain viable in aerosols for up to three hours, and NIV has been grouped together with a variety of other respiratory procedures that may cause aerosolization (e.g., intubation, extubation, nebulization, and bronchoscopy). Given the risk of aerosol dispersion through or around the mask interface, and the fact that certain interfaces contain asphyxiation valves or ports that can leak out exhaled gases, certain guidelines suggest noninvasive ventilation should be avoided completely. In addition, improper fit may cause leaking gas from around the mask
Using smoke to simulate aerosols, studies have looked at the dispersion distance with a variety of respiratory support devices.1 A traditional nasal cannula at 5 L / min demonstrated a dispersion of 100 cm. When there's a leak or a valve in a NIV mask, on a bilevel setting (BPAP) with an inspiratory positive airway pressure (IPAP) of 18 cmH2O, maximal dispersion in a negative pressure room was measured at 92 cm. Shorter distances were demonstrated with lower inspiratory pressures—but still, NIV results in larger dispersion distances compared to other noninvasive support methods.2
And, based on data from the original SARS outbreak, use of noninvasive ventilation, or NIV, was associated with an increased risk of encountering respiratory secretions, and an increased risk of transmission of SARS to health care workers. COVID-19 may act differently, but we may not have reliable data for weeks to months. So, until we have a better understanding, it’s best to only use NIV for patients with COVID-19 with caution and by following the most up-to-date recommendations at the time.
Does NIV help or harm patients with COVID-19?
Another concern about the use of NIV in patients with COVID-19 is the potential that it will be ineffectual.
COVID-19 may cause severe viral pneumonia that meets the definition of acute respiratory distress syndrome (ARDS). But we must be cautious with the use of NIV in pneumonia and ARDS. Historical failure rates are around 50%.
Additionally, noninvasive ventilation may cause harm to patients through two different mechanisms, leading to worsening patient outcomes:
- The lack of ability to control tidal volumes.
- The possible delay in intubation and mechanical ventilation.
Applying NIV in patients with COVID-19
So, what to do if noninvasive ventilation, or NIV, might be the only option or seems like a reasonable thing to try? For example, if you have a patient with an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with wheezing, and you suspect COVID-19, NIV may be a reasonable choice.
There are 5 steps to follow when using NIV to treat patients with COVID-19:
- Ensure that you are able to get a negative pressure room. If none are available, obtain a single occupancy room and ensure the door is closed at all times.
- Choose the best interface for the patient's tolerance. When available, consider a helmet or full-face mask interface to minimize particle dispersion. Ensure a good seal, and make sure the mask does not have an anti-asphyxiation valve or cord.
- Use dual limb circuitry with a filter on the expiratory limb of a critical care ventilator. This may decrease dispersion compared with single limb circuitry portable devices.
- Start with continuous positive airway pressure (CPAP) using the lowest effective pressures, between 5 and 8 cmH2O. Early reports suggest most patients with COVID-19 are not hypercapnic, so bilevel positive airway pressure (BPAP) may result in increased inspiratory pressures without any added benefit.
- Reevaluate patients within the first few hours of therapy. If patients are not responding, consider intubation and mechanical ventilation.
That’s it for now. If you want to improve your understanding of key concepts in medicine, and improve your clinical skills, make sure to register for a free trial account, which will give you access to free videos and downloads. We’ll help you make the right decisions for yourself and your patients.
- Hui, DS, Chow, BK, Lo, T, et al. 2015. Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask. Chest. 147: 1336–1343. PMID: 25392954
- Ferioli, M, Cisternino, C, Leo, V, et al. 2020. Protecting healthcare workers from SARS-CoV-2 infection: practical indications. Eur Respir Rev. 29: 2000068. PMID: 32248146