The Natural History of a Patient With COVID-19 Pneumonia and Silent Hypoxemia

In less than a year, COVID-19 has infected nearly 100 million people worldwide and caused more than 2 million deaths and counting. Although the infection fatality rate is estimated to be 1% and the case fatality rate between 2% and 3%, COVID-19 has had a disproportionate effect on the older population and those with comorbidities. Some of these findings are mirrored in the US Department of Veterans Affairs (VA) population, which has seen a higher case fatality rate.^1-4

As a respiratory tract infection, the most dreaded presentation is severe pneumonia with acute hypoxemia, which may rapidly deteriorate to acute respiratory distress syndrome (ARDS) and respiratory failure.^5-7 This possibility has led to early intubation strategies aimed at preempting this rapid deterioration and minimizing viral exposure to health care workers. Intubation rates have varied widely with extremes of 6 to 88%.^8,9

However, this early intubation strategy has waned as some of the rationale behind its endorsement has been called into question. Early intubation bypasses alternatives to intubation; high-flow nasal cannula oxygen, noninvasive ventilation, and awake proning are all effective maneuvers in the appropriate patient.^10,11 The use of first-line high-flow nasal cannula oxygen and noninvasive ventilation has been widely reported. Reports of first-line use of high-flow nasal cannula oxygen has not demonstrated inferior outcomes, nor has the timing of intubation, suggesting a significant portion of patients could benefit from a trial of therapy and eventually avoid intubation.^11-14 Other therapies, such as systemic corticosteroids, confer a mortality benefit in those patients with COVID-19 who require oxygen or mechanical ventilation, but their impact on the progression of respiratory failure and need for intubation are undetermined.

There also are reports of patients who report no signs of respiratory distress or dyspnea with their COVID-19 pneumonia despite profound hypoxemia or high oxygen requirements. Various terms, including silent hypoxemia or happy hypoxia, are descriptive of the demeanor of these patients, and treatment has invariably included oxygen.^15,16 Nevertheless, low oxygen measurements have generally prompted higher levels of supplemental oxygen or more invasive therapies.

Treatment rendered may obscure the trajectory of response, which is important to understand to better position options for invasive therapies and other therapeutics. We recently encountered a patient with a course of illness that represented the natural history of COVID-19 pneumonia with low oxygen levels (referred to as hypoxemia for consistency) that highlighted several issues of management.

Case Presentation

A 62-year-old undomiciled woman with morbid obesity, prediabetes mellitus, long-standing schizophrenia, and bipolar disorder presented to our facility for evaluation of dry cough and need for tuberculosis clearance for admittance to a shelter. She appeared comfortable and was afebrile with blood pressure 111/74 mm Hg, heart rate 82 beats per minute. Her respiratory rate was 18 breaths per minute, but the pulse oximetry showed oxygen saturation of 70 to 75% on room air at rest. A chest X-ray showed bibasilar infiltrates (Figure 1), and a rapid COVID-19 nasopharyngeal polymerase chain reaction (PCR) test returned positive, confirmed by a second PCR test. Baseline inflammatory markers were elevated (Figure 2). In addition, the serum interleukin-6 also was elevated to 66.1 pg/mL (normal < 5.0), erythrocyte sedimentation rate elevated to 69 mm/h, but serum procalcitonin was essentially normal (0.22 ng/mL; normal < 20 ng/mL) as was the serum lactate (1.4 mmol/L).

The patient was admitted to the intensive care unit (ICU) for close monitoring in anticipation of the possibility of decompensation based on her age, hypoxia, and elevated inflammatory markers.¹⁷ Besides a subsequent low-grade fever (100.4 oF) and lymphopenia (manual count 550/uL), she remained clinically unchanged. Throughout her hospitalization, she maintained a persistent psychotic delusion that she did not have COVID-19, refusing all medical interventions, including a peripheral IV line and supplemental oxygen for the entire duration. Extensive efforts to identify family or a surrogate decision maker were unsuccessful. After consultation with Psychiatry, Bio-Ethics, and hospital leadership, the patient was deemed to lack decision-making capacity regarding treatment or disposition and was placed on a psychiatric hold. However, since any interventions against her will would require sedation, IV access, and potentially increase the risk of nosocomial COVID-19 transmission, she was allowed to remain untreated and was closely monitored for symptoms of worsening respiratory failure.