ACEP COVID-19 Field Guide

Table of Contents


Work Safety


COVID-19 is thought to spread mainly through close contact from person to person, including between people who are physically near each other (<6 ft). Asymptomatic carriers can also spread the virus to others. 

COVID-19 spreads very easily from person to person

  • The virus that causes COVID-19 appears to spread more efficiently than influenza but not as efficiently as measles, which is among the most contagious viruses known to affect people.

COVID-19 most commonly spreads during close contact

  • People who are physically near (<6 feet) a person with COVID-19 or have direct contact with that person are at greatest risk of infection.
  • Infections occur mainly through exposure to respiratory droplets when a person is in close contact with someone who has COVID-19. Respiratory droplets cause infection when they are inhaled or deposited on mucous membranes, such as those that line the inside of the nose and mouth.

COVID-19 can sometimes be spread by airborne transmission

  • Some infections can be spread by exposure to the virus in small droplets and particles that can linger in the air for min to hrs. These viruses may be able to infect people who are >6 ft away from the person who is infected or after that person has left the space.
  • There is evidence that under certain conditions, people with COVID-19 seem to have infected others who were >6 ft away. These transmissions occurred within enclosed spaces that had inadequate ventilation.
  • Under these circumstances, scientists believe that the amount of infectious smaller droplets and particles produced by the people with COVID-19 became concentrated enough to spread the virus to other people. The people who were infected were in the same space during the same time or shortly after the person with COVID-19 had left.

COVID-19 spreads less commonly through contact with contaminated surfaces

  • Contamination of surfaces with droplets of the COVID-19 virus is possible and may persist for hours, and potentially days (see the field guide section entitled “COVID-19 Aerosol and Surface Stability”)

COVID-19 rarely spreads between people and animals

  • It appears that the virus that causes COVID-19 can spread from people to animals in some situations. CDC is aware of a small number of pets worldwide, including cats and dogs, reported to be infected with the virus that causes COVID-19, mostly after close contact with people with COVID-19. 
  • At this time, the risk of COVID-19 spreading from animals to people is considered to be low. 

More information can be found in the CDC Guidance on How Coronavirus Spreads.

Metered-dose inhalers versus nebulization 

Author: Susan R. Wilcox, MD, FACEP, Division Chief, Critical Care, Department of Emergency Medicine, Associate Professor of Emergency Medicine, Harvard Medical School, Associate Chief Medical Officer, Boston MedFlight

Given the risk of aerosolization of the virus, increasing the exposure risk to health care workers or other patients, nebulized medications should be avoided. Respiratory medications should be administered as metered-dose inhalers (MDIs). 


Author: Susan R. Wilcox, MD, FACEP, Division Chief, Critical Care, Department of Emergency Medicine, Associate Professor of Emergency Medicine, Harvard Medical School, Associate Chief Medical Officer, Boston MedFlight

Both BiPAP and CPAP are controversial in patients with COVID-19. The concern is that noninvasive positive-pressure ventilation (NIPPV) could theoretically increase aerosolization of the virus, increasing the exposure risk to health care workers or other patients. Additionally, experience with prior viral pneumonias has demonstrated a high failure rate of approximately 60% to 80%. Lastly, there are concerns that patients with acute respiratory distress syndrome (ARDS) may have large, unchecked tidal volumes on NIPPV, resulting in lung-injurious ventilation. The potential benefits of avoiding intubation are obvious for the individual patient. When also considering ventilators as a scarce resource, a prevented intubation can result in better resource allocation. While many institutions are not promoting NIPPV at this time, its use has been supported by the Society of Critical Care Medicine, with caveats. If NIPPV is used, patients must be monitored carefully, and intubation should not be delayed if there are any signs of worsening. However, there is insufficient evidence to recommend CPAP or BiPAP.

High-flow nasal oxygen

Article summary: respiratory support for adult patients with COVID‐19

Whittle JS, Pavlov I, Sacchetti AD, Atwood C, Rosenberg MS. Respiratory support for adult patients with COVID-19. JACEP Open. Published 2020 Apr 2. doi:10.1002/emp2.12071

Author: Jessica Whittle, MD, PhD, FACEP, Director of Research, Department of Emergency Medicine, University of Tennessee College of Medicine

High-flow nasal oxygen (HFNO) includes high-flow nasal cannula (HFNC) and high-velocity nasal insufflation. The use of HFNO has been associated with lower mortality in hypoxemic respiratory failure.1 Compared to conventional oxygen therapy, HFNO is associated with decreased risk of subsequent intubation (RR 0.85, 95% CI 0.74-0.99)2 and need for ICU admission.3,4  Initial concern existed on the risk of aerosolization with HFNO, leading some to recommend avoiding use of this modality. However, the degree of aerosolization has been shown to be minimal with these devices, and it is now recommended as the oxygenation therapy of choice in patients with respiratory distress (Figure 3.3). Guidelines from the WHO,5 the Italian Thoracic Society,6 the Respiratory Care Committee of the Chinese Thoracic Society,7 and The Australian and New Zealand Intensive Care Society;8 a joint statement from the German intensive care, anesthesia, and emergency medicine societies;9 and the joint guidelines produced by the European Society of Intensive Care Medicine and The Society of Critical Care Medicine10 all recommend HFNO as a therapy for COVID-19 respiratory failure. Recent publications suggest that newer HFNO and NIPPV systems with good interface fitting do not create widespread dispersion of exhaled air and therefore may be associated with low risk of airborne transmissions.5,8

A high-fidelity mannequin study demonstrated that even at the highest setting of 60 L/ min, exhaled air dispersion was 17 cm in a healthy lung scenario and 4.8 cm in a severely diseased lung scenario.11 Some guidelines recommend placement of a surgical mask over patients being treated with high-flow therapies as a secondary safety measure.9 High-fidelity human mannequin simulation studies show surgical masks do, in fact, reduce exhaled air dispersion.12 If HFNO oxygen therapy is used, medical staff should use airborne protection, and the patient should be treated in a negative-pressure room, if available.5,8

Newer data also support the safety of high-flow oxygen therapies. A recent study was published evaluating computational fluid dynamic simulation and a different model of high-flow oxygen therapy.13 It demonstrated that a patient treated with high-flow oxygen therapy at maximal settings with a surgical mask placed over the face generated an aerosol dispersion cloud similar to a patient with tidal breathing.13

There is no currently published evidence that HFNO is a risk factor for nosocomial transmission of respiratory pathogens.14-17 During the 2003 Toronto SARS-CoV outbreak, HFNO was not found to be a risk factor for transmission to health care workers.17 This is in contrast to endotracheal intubation, which was strongly associated with transmission to health care workers during the SARS epidemic.18 

There are currently no defined criteria for HFNO failure, but patients who require vasopressor support17 and whose respiratory rate and thoracoabdominal asynchrony are not rapidly relieved with HFNO19 are potentially at high risk of HFNO failure. Recently, the “ROX Index” was developed to aid in the prediction of clinical outcomes of patients treated with HFNO. It is calculated by the ratio of oxygen saturation, as measured by pulse oximetry/FiO2 to respiratory rate. A ROX Index >4.88 is predictive of success, meaning the patient is unlikely to progress to needing mechanical ventilation.20 Patients with established ARDS should move rapidly to mechanical ventilation and treated per published recommendations.21,22

Figure 3.3 Comparison of aerosol dispersion differences, using various treatment modalities.

Figure 3.2


  1. Frat JP, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med. 2015;372(23):2185-2196. doi:10.1056/NEJMoa1503326
  2. Rochwerg B, Granton D, Wang DX, et al. High flow nasal cannula compared with conventional oxygen therapy for acute hypoxemic respiratory failure: a systematic review and meta-analysis. Intensive Care Med. 2019;45(5):563-572. doi:10.1007/s00134-019-05590-5
  3. Nagata K, Morimoto T, Fujimoto D, et al. Efficacy of high-flow nasal cannula therapy in acute hypoxemic respiratory failure: decreased use of mechanical ventilation. Respir Care. 2015;60(10):1390-1396. doi:10.4187/respcare.04026
  4. Plate JDJ, Leenen LPH, Platenkamp M, Meijer J, Hietbrink F. Introducing high-flow nasal cannula oxygen therapy at the intermediate care unit: expanding the range of supportive pulmonary care. Trauma Surg Acute Care Open. 2018;3(1):e000179. Published 2018 Aug 3. doi:10.1136/tsaco-2018-000179
  5. WHO. Clinical management of severe acute respiratory infection when novel coronavirus (2019-nCoV) infection is suspected: interim guidance. Published 2020 January 28. WHO/nCoV/Clinical/2020.3
  6. Harari SA, Vitacca M, Blasi F, Centanni S, Santus PA, Tarsia P. Managing the respiratory care of patients with COVID-19. Italian Thoracic Society - Associazione Italiana Pneumologi Ospedalieri - Societa Italiana Di Pneumologia; 2020.
  7. Respiratory care committee of Chinese Thoracic Society. [Expert consensus on preventing nosocomial transmission during respiratory care for critically ill patients infected by 2019 novel coronavirus pneumonia]. Zhonghua Jie He He Hu Xi Za Zhi. 2020;17(0):E020. doi:10.3760/cma.j.issn.1001-0939.2020.0020
  8. ANZICS. COVID-19 guidelines. The Australian and New Zealand Intensive Care Society; 2020. 
  9. Kluge S, Janssens U, Welte T, Weber-Carstens S, Marx G, Karagiannidis C. Empfehlungen zur intensivmedizinischen Therapie von Patienten mit COVID-19 [Recommendations for critically ill patients with COVID-19] [published online ahead of print, 2020 Mar 12]. Med Klin Intensivmed Notfmed. 2020;1-3. doi:10.1007/s00063-020-00674-3
  10. Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with coronavirus disease 2019 (COVID-19) [published online ahead of print, 2020 Mar 28]. Intensive Care Med. 2020;1-34. doi:10.1007/s00134-020-06022-5
  11. Hui DS, Chow BK, Lo T, et al. Exhaled air dispersion during high-flow nasal cannula therapy versus CPAP via different masks. Eur Respir J. 2019;53(4):1802339. Published 2019 Apr 11. doi:10.1183/13993003.02339-2018
  12. Hui DS, Chow BK, Chu L, et al. Exhaled air dispersion during coughing with and without wearing a surgical or N95 mask. PLoS One. 2012;7(12):e50845. doi:10.1371/journal.pone.0050845
  13. Leonard S, Atwood CW, Walsh BK, et. al. Preliminary Findings on Control of Dispersion of Aerosols and Droplets During High-Velocity Nasal Insufflation Therapy Using a Simple Surgical Mask: Implications for the High-Flow Nasal Cannula. Chest, 2020.
  14. Leung CCH, Joynt GM, Gomersall CD, et al. Comparison of high-flow nasal cannula versus oxygen face mask for environmental bacterial contamination in critically ill pneumonia patients: a randomized controlled crossover trial. J Hosp Infect. 2019;101(1):84-87. doi:10.1016/j.jhin.2018.10.007
  15. Kotoda M, Hishiyama S, Mitsui K, et al. Assessment of the potential for pathogen dispersal during high-flow nasal therapy [published online ahead of print, 2019 Nov 20]. J Hosp Infect. 2019. doi:10.1016/j.jhin.2019.11.010
  16. Raboud J, Shigayeva A, McGeer A, et al. Risk factors for SARS transmission from patients requiring intubation: a multicentre investigation in Toronto, Canada. PLoS One. 2010;5(5):e10717. Published 2010 May 19. doi:10.1371/journal.pone.0010717
  17. Rello J, Perez M, Roca O, et al. High-flow nasal therapy in adults with severe acute respiratory infection: a cohort study in patients with 2009 influenza A/H1N1v. J Crit Care. 2012;27(5):434-439. doi:10.1016/j.jcrc.2012.04.006
  18. Bouadma L, Lescure FX, Lucet JC, Yazdanpanah Y, Timsit JF. Severe SARS-CoV-2 infections: practical considerations and management strategy for intensivists. Intensive Care Med. 2020;46(4):579-582. doi:10.1007/s00134-020-05967-x
  19. Sztrymf B, Messika J, Bertrand F, et al. Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med. 2011;37(11):1780-1786. doi:10.1007/s00134-011-2354-6
  20. Roca O, Caralt B, Messika J, et al. An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy. Am J Respir Crit Care Med. 2019;199(11):1368-1376. doi:10.1164/rccm.201803-0589OC
  21. Fielding-Singh V, Matthay MA, Calfee CS. Beyond low tidal volume ventilation: treatment adjuncts for severe respiratory failure in acute respiratory distress syndrome. Crit Care Med. 2018;46(11):1820-1831. doi:10.1097/CCM.0000000000003406
  22. Matthay MA, Aldrich JM, Gotts JE. Treatment for severe acute respiratory distress syndrome from COVID-19 [published online ahead of print, 2020 Mar 20]. Lancet Respir Med. 2020. doi:10.1016/S2213-2600(20)30127-2

Article Summary: DoD COVID-19 practice management guide regarding high-flow nasal cannula in the clinical management of severe COVID-19

Matos RI, Chung KK, Benjamin J, et al. DoD COVID-19 practice management guide: clinical management of COVID-19. Defense Health Agency. Published 2020 Mar 23.

To consolidate resources and optimize the management of patients requiring clinical care during the global COVID-19 pandemic, selected information from the practice management guide regarding HFNC is listed here. Refer to the full document cited above for a detailed rationale and complete list of references.

Management of severe COVID-19: oxygen therapy and monitoring

Give supplemental oxygen therapy immediately to patients with respiratory distress, hypoxemia, or shock and target SpO2 92% to 96% (No. 1).

For adults, initiate oxygen therapy during resuscitation at 5 to 6 L/min, and titrate flows to reach target SpO2 92% to 96% during resuscitation. If a persistent requirement for 5 to 6 L/min continues and resources are lacking for invasive ventilation, consider use of HFNC or a face mask with a reservoir bag at 10 to 15 L/min if the patient is in critical condition (No. 3).

Recommendations are evolving regarding the risk-benefit ratio but favor HFNC over BiPAP/noninvasive ventilation (NIV) if early intubation and mechanical ventilation is not possible. HFNC is a more effective intervention for noninvasive management of ARDS that requires less staff intervention. HFNC is also potentially safer for staff than BiPAP/NIV. Avoid BiPAP, if HFNC is unsuccessful; early intubation is recommended (No. 4).

Management of Critical COVID-19: acute respiratory distress syndrome (ARDS)

Development of respiratory failure 

All forms of respiratory therapy have a risk of aerosolization of the virus and risk to others. Comparison of noninvasive respiratory modalities continues to evolve, but presently, use of HFNC should be favored over BiPAP. HFNC is more efficacious for noninvasive management of ARDS compared to BiPAP, is generally well tolerated, and requires less staff intervention (coming in and out of room for alarms and trouble-shooting). If this therapy is attempted, it should ideally be confined to negative-pressure isolation rooms, and health care workers should have appropriate personal protective equipment (PPE), including N95 masks and PAPR (No. 2).

Management of ARDS 

Although an area of controversy, early expert opinion favors HFNC over other noninvasive modalities (see The Internet Book of Critical Care: COVID-19) because it appears to be well tolerated, more efficacious than BIPAP and less provider intensive. There is presently no definitive evidence that HFNC augments transmission of the virus (No. 2).

Caring for special populations: pregnancy, nursing mothers, infants, children, and the elderly

Neonatal intensive care unit

Patients requiring nasal cannula or those who are intubated on mechanical ventilation (closed circuit) require contact/droplet precautions when handling, including a surgical mask, a gown, a hair cover, and gloves (No. 5).

Per WHO guidance for clinical management of COVID-19, “newer high-flow nasal cannula (HFNC) and non-invasive ventilation (NIV) systems with food interface fitting do not create widespread dispersion of exhaled air and therefore should be associated with low risk of airborne transmission.” These patients could be cared for with contact/droplet precautions only (to include a face mask) but could consider N95 (or PAPR) if readily available.

Article summary: AARC guidance document for SARS CoV-2 (COVID-19)

American Association for Respiratory Care. Guidance document: SARS CoV-2. AARC website.

Author: Richard D. Branson, MSc, RRT, FAARC, Editor-in-Chief, Respiratory Care, University of Cincinnati; Dean R. Hess, Editor, Respiratory Care; Rich Kallet, MSc, PhD, RRT, FAARC, Managing Editor, Editor, Respiratory Care, San Francisco General Hospital; Lewis Rubinson, PhD, MD, Chief Medical Officer, Morristown Medical Center, Morristown, NJ

Below is select information from the guidance document regarding HFNC (Table 3.1). Refer to the full document cited above for a detailed rationale and complete list of references. 

Table 3.1 Recommendations from the Society for Critical Care Medicine Task Force.

Table 3.1

COVID-19 Guidance on Ventilation in the Workplace

Ensuring adequate ventilation throughout the work environment can help to maintain a safe and healthy workplace. Employers should work with heating, ventilation, and air conditioning (HVAC) professionals to consider steps to optimize building ventilation. The following tips can help reduce the risk of exposure to the coronavirus:

  • Ensure all HVAC systems are fully functional, especially those shut down or operating at reduced capacity during the pandemic.
  • Remove or redirect personal fans to prevent blowing air from one worker to another.
  • Use HVAC system filters with a Minimum Efficiency Reporting Value (MERV) rating of 13 or higher, where feasible.
  • Increase the HVAC system’s outdoor air intake. Open windows or other sources of fresh air where possible.
  • Be sure exhaust air is not pulled back into the building from HVAC air intakes or open windows.
  • Consider using portable high-efficiency particulate air (HEPA) fan/filtration systems to increase clean air, especially in higher-risk areas.
  • When changing filters, wear appropriate personal protective equipment. ASHRAE recommends N95 respirators, eye protection (safety glasses, goggles, or face shields), and disposable gloves.
  • Make sure exhaust fans in restrooms are fully functional, operating at maximum capacity, and are set to remain on.
  • For more information access the OSHA COVID-19 Guidance on Ventilation in the Workplace.

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