The SARS-CoV-2 virus and COVID-19 illness certainly have raised many serious health concerns and caused large disruptions in the delivery of care across the nation, especially in places like New York, Seattle, and New Orleans. Respiratory therapists have been on the front lines of the effort to save lives threatened by the virus and while we often hear in the media that there are not enough ventilators, the truth is that without a well-qualified respiratory therapist on site, the modern critical care ventilator is largely useless.
Outside of the current hotspots, much of the rest of the nation faces a continuing disruption in the health care system and possible surge in critically ill patients. In addition, everyone is considering what the new normal will look like when (and if) social distancing strategies are relaxed. As we continue to prepare, this may be a good time to briefly review what we know and what we don’t know about the mechanical ventilation of COVID-19 patients.
Before we discuss ventilatory support of the COVID-19 patient, let’s review some of the features of the disease. First, about 81% of infected individuals experience mild to moderate symptoms. These folks tend to do just fine at home. About 14% of infected individuals wind up with severe disease, including hypoxemia requiring hospital admission. About 5% of infected individuals become critically ill, and most of these patients will require intubation and mechanical ventilation.
COVID-19 is thought to be spread by droplets expelled when an infected individual coughs or sneezes. These droplets may land on others, or on inanimate objects and be transferred through touching the nose, mouth, or eyes. Consequently, treating everyone you meet as potentially infected, wearing a mask (either procedure or surgical mask or cloth mask) to protect others, keeping a distance of at least 6 feet apart, and frequently washing your hands can be effective in reducing the spread of the disease. Social isolation has pretty clearly been shown to be very effective in reducing spread when large numbers of the population follow directions and stay home.
While some infected individuals may show no symptoms, the common clinical manifestations of COVID-19 include fever (99% of cases), fatigue (70%), dry cough (59%), loss of appetite (40%), muscle aches (35%), and shortness of breath (31%). Other symptoms may include sore throat, nasal congestion, headache and (rarely) nausea, vomiting and diarrhea. Typically, exposure to SARS-CoV-2 is followed by symptoms in about 4 to 5 days, however, symptoms can appear up to 14 days following exposure. For those with serious or critical illness, dyspnea may occur 6 to 7 days following initial symptoms which may then develop into full-blown ARDS (Acute Respiratory Distress Syndrome) in another two or three days. Consequently, the course of the illness can progress over a number of days, and those with mild illness at home should receive guidance on self-monitoring and actions to take if the illness worsens.
The respiratory disease caused by the SARS-CoV-2 virus presents as an acute viral pneumonia, which can then evolve into full-blown ARDS. Patients seen in the emergency room and intensive care unit typically present with profound, acute hypoxemic respiratory failure. The chest radiograph will often show ground-glass opacification, generally in the lower lung fields and in the periphery, with or without areas of consolidation. Morbidity and mortality can be very high, with reports of up to 80% of patients receiving mechanical ventilation expiring. Recall that mortality rates in more traditional ARDS are about 35% to 46%, and ARDSnet has reported ARDS mortality as low as 26 to 35%. It’s not clear if the very high mortality rate associated with COVID-19 is due entirely to the disease process or may be exacerbated by intensive care units and emergency departments being overwhelmed.
Initial hospital care includes the administration of oxygen therapy, typically by nasal cannula at 5-6 L/min in an attempt to maintain an SpO2 of at least 92%, but not higher than 96%. Most current guidance (AARC, WHO, SCCM, ) suggests there be a low threshold for treatment failure followed by urgent intubation. However, some in New York City have begun to defer intubation and mechanical ventilation unless absolutely necessary in order to conserve scarce resources. Since many COVID-19 do not have hypercapnia, some have suggested initiation of high flow nasal cannula (HFNC) for the severe hypoxemia seen. Concerns about creating aerosols and related problems with infection control have led others to suggest simply using an oxygen mask with reservoir bag and flows to the oxygen mask in the range of 10-15 L/min. If used, HFNC flows may be restricted to 30 L/min in an attempt to reduce aerosol generation. While NIV has been tried at some centers, it appears to have a high failure rate and if the patient does not respond quickly to NIV, intubation and invasive ventilation have been recommended.
Current guidelines suggest the ventilator management of COVID-19 patients include the use of the ARDSnet protocols. This is not without some controversy, as the initial presentation of COVID-19 associated respiratory failure may be “atypical”. Guidelines for mechanical ventilation of the COVID-19 patient will be further discussed in the next installment of our blog. That said, what we know about COVID-19 is constantly evolving, and today’s approach will almost certainly be revised as more information becomes available.
About David C. Shelledy, RRT, RPFT, FAARC, FASAHP
Professor and Dean, School of Health Professions, University of Texas Health Science Center, San Antonio, Texas, Dean Emeritus and Professor, Departments of Respiratory Care, Clinical Sciences, and Health Systems Management, Rush University, Rush University Medical Center, Chicago, Illinois
Dr. Shelledy has served as a professor, respiratory care program director and respiratory care academic department chairman for over 25 years. He has taught patient assessment, both at the bedside and in the classroom to respiratory care students at St. Petersburg College, Georgia State University, Athens Technical College, Rush University, University of Arkansas for Medical Sciences, and the
University of Texas Health Science Center at San Antonio. He currently holds appointment as Professor and Dean, School of Health Professions at The University of Texas Health Science Center, San Antonio, Texas.
His most recent award winning text Mechanical Ventilation is a comprehensive guide to the evaluation and management of critically ill
patients requiring mechanical ventilatory support. This new text helps respiratory care students and clinicians alike bridge the gap between theory and practice as they strive to provide the very best care for patients.
Clinical management of severe acute respiratory infection (SARI) when COVlD–19 disease is suspected. Interim guidance, March 13, 2020, World Health Organization. https://www.who.int/publications-detail/clinical-management-of-severe-acute-respiratory-infection-when-novel-coronavirus-(ncov)-infection-is-suspected
SARS COV-2 guidance document. American Association for Respiratory Care. https://www.aarc.org/wp-content/uploads/2020/03/guidance-document-SARS-COVID19.pdf
Society for Critical Care Medicine COVID-19 Guidelines. https://sccm.org/SurvivingSepsisCampaign/Guidelines/COVID-19
Worsester S. Is protocol driven COVID-19 ventilation doing more harm than good? Medscape, April 6, 2020. https://www.medscape.com/viewarticle/928236
Gattinoni L, Coppola S, Cressoni M, et al. Covid-19 Does Not Lead to a “Typical” Acute Respiratory Distress Syndrome (letter to the editor). American Journal of Respiratory and Critical Care Medicine. March 30, 2020 https://www.atsjournals.org/doi/abs/10.1164/rccm.202003-0817LE