'Silent Hypoxemia' and Other Curious Clinical Observations in COVID-19

Gary S. Ferenchick, MD, MS; Hannah R.B. Ferenchick, MD


April 16, 2020

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This transcript has been edited for clarity.

Gary S. Ferenchick, MD, MS, a professor of medicine at Michigan State University, interviewed his daughter, Hannah R.B. Ferenchick, MD, an emergency and critical care physician working on the frontline in a busy Detroit hospital, about some of the unusual clinical features of patients with suspected or confirmed COVID-19.

Gary S. Ferenchick, MD, MS: I'm Gary Ferenchick with Hannah Ferenchick, who has agreed to join us to talk about what's going on in Detroit, and also about PPE and decontamination processes. Why don't you introduce yourself?

Hannah R.B. Ferenchick, MD: I am Hannah Ferenchick. I'm an ER physician and medical intensivist. I split my time between the medical ICU and the emergency department at Detroit Medical Center.

Dr Gary Ferenchick: We were talking earlier about some of the not-well-described clinical scenarios that patients with definitive COVID might present with. One of these was the idea of "silent hypoxemia." Could you describe that?

Dr Hannah Ferenchick: Silent hypoxemia is being described in many of these COVID patients. That means the patient is very hypoxemic—they may have an oxygen saturation of about 85% on room air, but clinically they look very comfortable—they are not dyspneic or tachypneic and may not even verbalize a significant sense of shortness of breath. It's not every patient, but it has been interesting to see patients sitting there looking fairly normal, with a resting oxygen saturation much lower than you would expect for someone who doesn't have underlying pulmonary disease or other symptoms.

Dr Gary Ferenchick: What abnormalities are you seeing on standard or not-so-standard lab tests?

Dr Hannah Ferenchick: Some of the characteristic lab findings we are seeing are lymphopenia and elevated inflammatory markers (eg, CRP). A couple of other atypical findings seem to be specific for COVID—elevated LDH, ferritin, CPK, and procalcitonin levels. Some of the hematologic markers that we look at—the coagulation profile studies—are also abnormal, showing thrombocytopenia and elevated D-dimer levels.

That constellation of symptoms represents more of a clinical picture. A lot of times we have only a very high clinical suspicion, because in many parts of the country it still takes days to get back a confirmatory PCR test.

Much like we do for the flu, the confirmatory test is a nasopharyngeal swab that is run for COVID/coronavirus PCR. Unfortunately the sensitivity of that test is not great. Some studies have quoted 75%-80%, so even a negative PCR does not necessarily rule out the disease, especially if you have a high clinical suspicion. A clinical suspicion is based on the typical symptoms. Many patients, although not all, will have symptoms of lower respiratory tract infection.

Dr Gary Ferenchick: So the right clinical scenario with the right hematologic/biochemical findings dramatically raises the chance that the patient has COVID?

Dr Hannah Ferenchick: Yes, and one thing that we have all been astonished by is how terrible some of these x-rays can look. There are a lot of typical findings on x-ray. Some describe them as looking like pulmonary edema, but the patient has no history of heart failure. Peripheral consolidation and ground-glass opacities are classically described. If you saw one of these x-rays from a patient with bacterial pneumonia, you would expect that patient to be very ill-appearing. Sometimes we get x-rays on patients who are sitting there, maybe mildly symptomatic on room air, and we are astonished by how terrible their x-rays look.

Unfortunately, imaging studies are something we haven't been able to rely on too much for diagnosis. Part of that is to maintain hospital safety, because to take a patient to CT scan, you have to consider the turnaround time for cleaning the CT scanner and the exposure of additional staff to a possibly infected patient. Some of those logistical considerations have limited the availability of radiography.

Gary S. Ferenchick, MD, MS, is a family physician and professor in the Department of Medicine at Michigan State University in East Lansing, Michigan. His daughter, Hannah R.B. Ferenchick, MD, is an assistant professor in the Department of Emergency Medicine, Division of Pulmonary & Critical Care and Sleep Medicine, at Wayne State University, Detroit, Michigan, and a medical intensivist and emergency medicine physician at Detroit Medical Center.

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