COVID-19: Potential Causes for Hypoxemia | Loyola Medicine

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Wednesday, July 8, 2020

New Study Explains Potential Causes for “Happy Hypoxia” Condition in Patients With the COVID-19 Virus

Findings could prevent unnecessary intubation

image of lungs

MAYWOOD, IL—A new research study provides possible explanations for COVID-19 patients who present with extremely low, otherwise life-threatening levels of oxygen, but no signs of dyspnea (difficulty breathing). This new understanding of the condition, known as silent hypoxemia or “happy hypoxia,” could prevent unnecessary intubation and ventilation in patients during the current and expected second wave of coronavirus.

The condition “is especially bewildering to physicians as it defies basic biology,” said Martin J. Tobin, MD, Loyola Medicine and Edward J. Hines Jr. VA Hospital pulmonologist and critical care specialist, and professor, Loyola University Chicago Stritch School of Medicine. Dr. Tobin is lead author of the study, “Why COVID-19 Silent Hypoxemia is Baffling to Physicians,” appearing recently in the online American Journal of Respiratory and Critical Care Medicine.

“In some instances, the patient is comfortable and using a phone at a point when the physician is about to insert a breathing (endotracheal) tube and connect the patient to a mechanical ventilator,” said Dr. Tobin, “which while potentially lifesaving carries its own set of risks.”

The study included 16 COVID-19 patients with very low levels of oxygen (as low as 50%; normal blood oxygen saturation is between 95 and 100%), without shortness of breath or dyspnea, and found that “several pathophysiological mechanisms account for most, if not all, cases of silent hypoxemia. This includes the initial assessment of a patient’s oxygen level with a pulse oximeter.

“While a pulse oximeter is remarkably accurate when oxygen readings are high, it markedly exaggerates the severity of low levels of oxygen when readings are low,” said Dr. Tobin. “Another factor is how the brain responds to low levels of oxygen. As oxygen levels drop in patients with COVID-19, the brain does not respond until oxygen falls to very low levels—at which point a patient typically becomes short of breath,” he said.

In addition, more than half of the patients had low levels of carbon dioxide, which may diminish the impact of an extremely low oxygen level.

“It is also possible that the coronavirus is exerting a peculiar action on how the body senses low levels of oxygen,” said Dr. Tobin, which could be linked to the lack of smell, experienced by two-thirds of COVID-19 patients.

While acknowledging that further research is needed, the study concludes that “features about COVID-19 that physicians find baffling become less strange when viewed in the light of long-established principles of respiratory physiology.”

“This new information may help to avoid unnecessary endotracheal intubation and mechanical ventilation, which presents risks, when the ongoing and much anticipated second wave of COVID-19 emerges,” said Dr. Tobin. 

About Loyola Medicine and Trinity Health

Loyola Medicine, a member of Trinity Health, is a quaternary care system based in the western suburbs of Chicago that includes Loyola University Medical Center (LUMC), Gottlieb Memorial Hospital, MacNeal Hospital and convenient locations offering primary and specialty care services from 1,877 physicians throughout Cook, Will and DuPage counties. LUMC is a 547-licensed-bed hospital in Maywood that includes the William G. and Mary A. Ryan Center for Heart & Vascular Medicine, the Cardinal Bernardin Cancer Center, a Level 1 trauma center, Illinois's largest burn center, a certified comprehensive stroke center and a children’s hospital. Having delivered compassionate care for over 50 years, Loyola also trains the next generation of caregivers through its teaching affiliation with Loyola University Chicago’s Stritch School of Medicine and Marcella Niehoff School of Nursing. Gottlieb is a 247-licensed-bed community hospital in Melrose Park with 150 physician offices, an adult day care program, the Gottlieb Center for Fitness, the Loyola Center for Metabolic Surgery and Bariatric Care and the Loyola Cancer Care & Research at the Marjorie G. Weinberg Cancer Center at Melrose Park. MacNeal Hospital is a 374-bed teaching hospital in Berwyn with advanced inpatient and outpatient medical, surgical and psychiatric services, advanced diagnostics and treatments. MacNeal has a 12-bed acute rehabilitation unit, a 25-bed inpatient skilled nursing facility, and a 68-bed behavioral health program and community clinics. MacNeal has provided quality, patient-centered care to the near west suburbs since 1919.

Trinity Health is one of the largest multi-institutional Catholic healthcare systems in the nation, serving diverse communities that include more than 30 million people across 22 states. Trinity Health includes 92 hospitals, as well as 109 continuing care locations that include PACE programs, senior living facilities and home care and hospice services. Its continuing care programs provide nearly 2.5 million visits annually. Based in Livonia, Mich., and with annual operating revenues of $18.3 billion and assets of $26.2 billion, the organization returns $1.1 billion to its communities annually in the form of charity care and other community benefit programs. Trinity employs about 129,000 colleagues, including 7,800 employed physicians and clinicians. Committed to those who are poor and underserved in its communities, Trinity is known for its focus on the country's aging population. As a single, unified ministry, the organization is the innovator of Senior Emergency Departments, the largest not-for-profit provider of home health care services—ranked by number of visits—in the nation, as well as the nation’s leading provider of PACE (Program of All Inclusive Care for the Elderly) based on the number of available programs.