What is 'happy hypoxia'? Experts weigh in on Covid-19 symptom

Female doctor checking on Covid-19 infected patient while connected to a ventilator

A well-known symptom of the coronavirus is low oxygen levels in the body, aka hypoxia, which normally lead to shortness of breath. But some coronavirus patients with hypoxia don't experience this hallmark sign that their oxygen levels have dropped into dangerous territory.

The phenomenon is referred to as 'happy hypoxia' or 'silent hypoxia', where the body has oxygen saturation below 90%, but the person can still breathe normally. Some doctors take issue with the term, though, because coronavirus patients with silent hypoxia often have other symptoms, such as fever or cough.

Silent hypoxia isn't new or specific to the coronavirus, interventional pulmonologist Dr. Udit Chaddha, assistant professor of pulmonary, critical care and sleep medicine at the Icahn School of Medicine at Mount Sinai in New York, told TODAY. It can happen with lung infections, viral or not.

That said, some experts believe it's more common and looks different in Covid-19 versus other respiratory illnesses.

"If you'd told me two months ago that someone would be sitting in an ER comfortable and able to have a conversation, but have an oxygen concentration around 80%, I'd tell you that you were crazy," Dr. Eric Cioe-Pena, an emergency medicine physician at Northwell Health in New York City, told TODAY.

31 PHOTOS
States reopen, relax guidelines to prevent coronavirus spread
See Gallery
States reopen, relax guidelines to prevent coronavirus spread
NEW YORK, NEW YORK - MAY 06: An employee wearing a mask cleans the inside of the restaurant, Blue Stripes Cacao Shop as it prepares to reopen for takeaway and delivery orders after being closed for over a month amid the coronavirus pandemic on May 6, 2020 in New York City. Governor Andrew Cuomo made the announcement that all bars and restaurants must close by on March 16th unless it was takeout or delivery. COVID-19 has spread to most countries around the world, claiming over 263,000 lives with over 3.8 million cases. (Photo by Alexi Rosenfeld/Getty Images)
NEW YORK, NEW YORK - MAY 06: An employee wearing a mask cleans the inside of the restaurant, Blue Stripes Cacao Shop as it prepares to reopen for takeaway and delivery orders after being closed for over a month amid the coronavirus pandemic on May 6, 2020 in New York City. Governor Andrew Cuomo made the announcement that all bars and restaurants must close by on March 16th unless it was takeout or delivery. COVID-19 has spread to most countries around the world, claiming over 263,000 lives with over 3.8 million cases. (Photo by Alexi Rosenfeld/Getty Images)
THOUSAND OAKS, CA - MAY 06: A Cadillac Dealership displays a sign stating its reopened during the Coronavirus Pandemic on May 06, 2020 in Thousand Oaks, California. The coronavirus pandemic worldwide has claimed over 263,000 lives and infected over 3.7 million people. (Photo by Josh Lefkowitz/Getty Images)
HOUSTON, May 5, 2020 -- Customers shop at a shopping mall in Frisco, on the outskirts of Dallas, Texas, the United States, May 5, 2020. After closed for several weeks due to the outbreak of COVID-19 pandemic, the shopping mall reopened with shortened business hours on Tuesday. (Photo by Dan Tian/Xinhua via Getty) (Xinhua/ via Getty Images)
HOUSTON, May 5, 2020 -- Cars are parked in front of a shopping mall in Frisco, on the outskirts of Dallas, Texas, the United States, May 5, 2020. After closed for several weeks due to the outbreak of COVID-19 pandemic, the shopping mall reopened with shortened business hours on Tuesday. (Photo by Dan Tian/Xinhua via Getty) (Xinhua/ via Getty Images)
Dawson Padilla (L), owner of a protein shakes store, works behind the bar on May 5, 2020 in Stillwater, Oklahoma. - In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. "About three and a half hours after the law came into effect" of the text, "we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence," said Norman McNickle, the city's director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
A worker of the Aspen Cafe wears a mask as she makes coffee on May 5, 2020 in Stillwater, Oklahoma. - In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. "About three and a half hours after the law came into effect" of the text, "we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence," said Norman McNickle, the city's director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
Kelly Lyda, owner of the Aspen Cafe, stands in his Cafe on May 5, 2020 in Stillwater, Oklahoma. - In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. "About three and a half hours after the law came into effect" of the text, "we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence," said Norman McNickle, the city's director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
Computer specialist Toby Angel drinks his coffee on May 5, 2020 in Stillwater, Oklahoma. - In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. "About three and a half hours after the law came into effect" of the text, "we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence," said Norman McNickle, the city's director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
WESTPORT, CONNECTICUT - MAY 05: A cafe along a shopping street in the affluent community remains mostly empty of pedestrians and open stores on May 05, 2020 in Westport, Connecticut. A growing number of states have begun reopening parts of the economy amid demonstrations like the one yesterday that targeted the Connecticut state capital and the governor's mansion in Hartford. (Photo by Spencer Platt/Getty Images)
WESTPORT, CONNECTICUT - MAY 05: A cafe along a shopping street in the affluent community remains mostly empty of pedestrians and open stores on May 05, 2020 in Westport, Connecticut. A growing number of states have begun reopening parts of the economy amid demonstrations like the one yesterday that targeted the Connecticut state capital and the governor's mansion in Hartford. (Photo by Spencer Platt/Getty Images)
LAGUNA HILLS, CA - MAY 05: Customers maintain safety protocols at The BarberHood in Laguna Hills, CA, on Tuesday, May 5, 2020. The shop is one of the first to re-open and defy the state"u2019s stay-at-home order during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)
SAN CLEMENTE, CA - MAY 05: Visitors walk on the beach south of the pier in San Clemente, CA on Tuesday, May 5, 2020. The city opened its beaches for daily active use after coordinating with Gov. Gavin Newsom"u2019s office to maintain social distancing during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)
SAN CLEMENTE, CA - MAY 05: Surfers were back on the waves at T Street in San Clemente, CA on Tuesday, May 5, 2020. The city opened its beaches for daily active use after coordinating with Gov. Gavin Newsom"u2019s office to maintain social distancing during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)
KENMORE, WA - MAY 05: Lynette Fisher-Charles and her dog Gracie, a two-year-old springer spaniel, go for a hike in Saint Edward State Park on May 5, 2020 in Kenmore, Washington. The first phase to reopen the state begins today easing some restrictions including opening some parks, that were put in place during Governor Jay Inslees Stay Home, Stay Healthy order last March to help reduce the spread of COVID-19. Kenmore, WA is located northeast of Seattle. (Photo by Karen Ducey/Getty Images)
KENMORE, WA - MAY 05: Daryl Kline, a park ranger at Saint Edward State Park removes a sign saying the park is closed on May 5, 2020 in Kenmore, Washington. The first phase to reopen the state begins today easing some restrictions that were put in place during Governor Jay Inslees Stay Home, Stay Healthy order last March to help reduce the spread of COVID-19. Kenmore, WA is located northeast of Seattle. (Photo by Karen Ducey/Getty Images)
LAGUNA BEACH, CA - MAY 05: Lifeguards keep a lookout at Laguna Beach, CA after officials reopened access to the sand on Tuesday, May 5, 2020. The beach has been closed since March 23, 2020 due to the COVID-19 (coronavirus) outbreak. City parks along the beach are still closed and people cannot sit or linger on the sand. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)
NEW YORK, May 4, 2020 -- Photo taken on May 4, 2020 shows Times Square in New York, the United States. Amid the ongoing COVID-19 pandemic, New York Governnor Andrew Cuomo on Monday outlined additional guidelines regarding when regions can reopen. According to the Governor's Press Office, the state will monitor four core factors to determine if a region can reopen: number of new infections, health care capacity, diagnostic testing capacity and contact tracing capacity. (Photo by Wang Ying/Xinhua via Getty) (Xinhua/Wang Ying via Getty Images)
NEW YORK, May 4, 2020 -- A worker cleans a cafe's signboard at Times Square in New York, the United States, May 4, 2020. Amid the ongoing COVID-19 pandemic, New York Governnor Andrew Cuomo on Monday outlined additional guidelines regarding when regions can reopen. According to the Governor's Press Office, the state will monitor four core factors to determine if a region can reopen: number of new infections, health care capacity, diagnostic testing capacity and contact tracing capacity. (Photo by Wang Ying/Xinhua via Getty) (Xinhua/Wang Ying via Getty Images)
ASBURY PARK, NJ - MAY 4: People walk near the closed boardwalk due to the outbreak of COVID-19 in the state on May 4, 2020 in the Jersey Shore in New Jersey. Some towns at Jersey Shore expect the reopening of beaches soon. (Photo by Eduardo MunozAlvarez/VIEWpress/Corbis via Getty Images)
NORTH ANDOVER, MA - MAY 4: Although all golf courses in Massachusetts are still ordered to stay closed by governor Charlie Baker, workers at the North Andover Country Club in North Andover, MA work on the grass on May 4, 2020, getting the course ready for when they eventually are allowed to re-open. (Photo by Jim Davis/The Boston Globe via Getty Images)
LOS ANGELES, CA - MAY 04: Gov. Gavin Newsom announced select retail businesses will be allowed to reopen starting Friday in California during the coronavirus pandemic on Monday, May 4, 2020 in Los Angeles, CA. (Jason Armond / Los Angeles Times via Getty Images)
SANFORD, UNITED STATES - MAY 04, 2020: Customers enjoy a meal at Racks Billiards Sports Bar and Grill on the first day that retail stores and restaurants in all Florida counties except Palm Beach, Broward, and Miami Dade were permitted to reopen as COVID-19 restrictions are eased. Under phase one of the plan to reopen the state, stores and restaurants are limited to 25 percent of their indoor capacity.- PHOTOGRAPH BY Paul Hennessy / Echoes Wire/ Barcroft Studios / Future Publishing (Photo credit should read Paul Hennessy / Echoes Wire/Barcroft Media via Getty Images)
SANFORD, UNITED STATES - MAY 04, 2020: A customer leaves a Books-A-Million store on the first day that retail stores and restaurants in all Florida counties except Palm Beach, Broward, and Miami Dade were permitted to reopen as COVID-19 restrictions are eased. Under phase one of the plan to reopen the state, stores and restaurants are limited to 25 percent of their indoor capacity.- PHOTOGRAPH BY Paul Hennessy / Echoes Wire/ Barcroft Studios / Future Publishing (Photo credit should read Paul Hennessy / Echoes Wire/Barcroft Media via Getty Images)
BOZEMAN, MT - MAY 04: Sales staff wear masks at the reopened Schnee's Boots, Shoes and Outdoors on Main Street on May 4, 2020 in Bozeman, Montana. Wyoming health officials today reported that the state's confirmed coronavirus cases grew by nine to a total of 444. (Photo by William Campbell/Getty Images)
BOZEMAN, MT - MAY 04: Signs for restaurants and stores announce their reopenings on Main Street on May 4, 2020 in Bozeman, Montana. Wyoming health officials today reported that the state's confirmed coronavirus cases grew by nine to a total of 444. (Photo by William Campbell/Getty Images)
JENSEN BEACH, FLORIDA - MAY 04: Cole Hunter carries Harper Hunter, 1, as Holly Hunter,4, follows along as they arrive at the beach on May 04, 2020 in Jensen Beach, Florida. Restaurants, retailers, as well as beaches and some state parks reopened today with caveats, as the state continues to ease restrictions put in place to contain COVID-19. The counties of Palm Beach, Broward and Miami Dade continue to maintain restrictions. (Photo by Joe Raedle/Getty Images)
JACKSONVILLE BEACH, FLORIDA - MAY 04: People are seen dining outside at Cruisers Grill as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Jacksonville Beach, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)
JACKSONVILLE BEACH, FLORIDA - MAY 04: People are seen at a department store as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Jacksonville Beach, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)
SAINT AUGUSTINE, FLORIDA - MAY 04: A mask is seen on the statue of Henry M. Flagler as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Saint Augustine, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)
A man works on power lines in Los Angeles, California on May 4, 2020, amid the coronavirus pandemic. - California governor Gavin Newsom earlier today announced the gradual reopening of the state later this week as dismal US employment figures are expected with the release of figures Friday May 8 for April's US jobs report, as 30 million Americans filed for unemployment in the last six weeks. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

What is "silent hypoxia"?

Silent hypoxia occurs in coronavirus patients when "there's areas of the lung ... (where) ventilation is pretty normal, but there's enough disease that they're having lower oxygen levels," Dr. David Hill, a pulmonary specialist in Waterbury, Connecticut and spokesperson for the American Lung Association, told TODAY.

"(These patients) will still have good enough lung function in terms of how the lungs move that they're able to blow off their carbon dioxide well so they don't develop the shortness of breath," he added.

Chaddha said he's seen in it in "a handful" of his coronavirus patients. Of every 10, usually between two and four experience silent hypoxia to some extent, he estimated.

When patients with silent hypoxia seek medical care, they've usually had coronavirus symptoms for five to seven days, Hill said. Cioe-Pena added that the "worst" time for hypoxia, silent or not, in coronavirus patients is around day 10 of the infection.

All three experts agreed that there are no characteristics or criteria that determine whether a person is at higher risk of silent hypoxia. It can be treated with a ventilator, but usually other strategies come first, such as a CPAP machine (continuous positive airway pressure machine, which uses a hose and mask to deliver constant air pressure) or adjusting the position of the body.

What's the impact of silent hypoxia on the body?

Chaddha stressed that the presence of silent hypoxia doesn't determine a coronavirus patient's prognosis.

"Let's say patient A had silent (hypoxia), and patient B did not," he explained. "It doesn't necessarily mean that patient A will do bad or good, or patient b will do bad or good. If patient B is more short of breath, it probably means there are other things going on."

Silent hypoxia doesn't usually go untreated for extended periods in coronavirus patients because they usually develop shortness of breath eventually, which should prompt them to seek medical care, Chaddha said. Also, many of these patients experience other signs of the coronavirus before shortness of breath, which land them in the emergency room or a doctor's office.

Since most patients may have untreated hypoxia for just a few days, experts stress that "low oxygen levels by themselves don't cause a lot of damage," Hill said. "Long-term, if we're talking months to years, that's not something we expect to see with Covid ... I really don't believe there's a lot of people hanging out at home feeling well and suddenly showing up sick with Covid-19."

Cioe-Pena added that low oxygen levels are "cause for investigation (by a medical professional) but not necessarily ... a life-threatening condition." In fact, he discharged a patient with the condition because she was otherwise fine.

Young, healthy patients can tolerate low oxygen levels for longer, Hill added.

14 PHOTOS
Coronavirus in US prisons
See Gallery
Coronavirus in US prisons
Inmates on the landscape crew tend to shrubbery at Las Colinas Women's Detention Facility in Santee, California, on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
TOPSHOT - A Sheriff's deputy and on-site nurse give medications to an inmate at Las Colinas Women's Detention Facility in Santee, California, on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
Tomoka Correctional Institution is seen in Daytona Beach, Florida on April 25, 2020, as corrections officials report that 84 inmates and 10 staff at the prison have tested positive for COVID-19. The number of prisoners at Tomoka who have tested positive for the coronavirus has more than doubled in the past week, making it the Florida prison with the most cases. (Photo by Paul Hennessy/NurPhoto via Getty Images)
Tomoka Correctional Institution is seen in Daytona Beach, Florida on April 25, 2020, as corrections officials report that 84 inmates and 10 staff at the prison have tested positive for COVID-19. The number of prisoners at Tomoka who have tested positive for the coronavirus has more than doubled in the past week, making it the Florida prison with the most cases. (Photo by Paul Hennessy/NurPhoto via Getty Images)
Tomoka Correctional Institution is seen in Daytona Beach, Florida on April 25, 2020, as corrections officials report that 84 inmates and 10 staff at the prison have tested positive for COVID-19. The number of prisoners at Tomoka who have tested positive for the coronavirus has more than doubled in the past week, making it the Florida prison with the most cases. (Photo by Paul Hennessy/NurPhoto via Getty Images)
A woman plays a horn while taking part in a vigil outside Queensboro Correctional Facility on April 23, 2020 in New York City. - The vigil was held for Leonard Carter, who died from COVID-19, while incarcerated at the facility. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
A man wearing a mask takes part in a vigil outside Queensboro Correctional Facility on April 23, 2020 in New York City. - The vigil was held for Leonard Carter, who died from COVID-19, while incarcerated at the facility. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
A woman wearing a mask takes part in a vigil outside Queensboro Correctional Facility on April 23, 2020 in New York City. - The vigil was held for Leonard Carter, who died from COVID-19, while incarcerated at the facility. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
A man wearing a mask holds a poster reading "No death camps in NYS", while taking part in a vigil outside Queensboro Correctional Facility on April 23, 2020 in New York City. - The vigil was held for Leonard Carter, who died from COVID-19, while incarcerated at the facility. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)
An inmate reads a book while in the infirmary at Las Colinas Women's Detention Facility in Santee, California on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
An inmate sews protective masks at Las Colinas Women's Detention Facility in Santee, California, on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
Inmates work in the laundry room at Las Colinas Women's Detention Facility in Santee, California, on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
Inmates sew protective masks at Las Colinas Women's Detention Facility in Santee, California, on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
Female inmates sit apart while watching TV at Las Colinas Women's Detention Facility in Santee, California on April 22, 2020. - Inmates and Sheriff's deputies at the prison are practicing COVID-19 measures including wearing masks, staying keeping a safe distance and doing more frequent cleaning at the facility. (Photo by Sandy Huffaker / AFP) (Photo by SANDY HUFFAKER/AFP via Getty Images)
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

How can you protect yourself from silent hypoxia?

The only way to know if you have silent hypoxia without seeking medical care is through at-home monitoring, Chaddha said. The best device for this is a pulse oximeter, which measures the saturation of oxygen carried in a person's red blood cells. You attach it to your finger tip to get a reading.

They're available for purchase in pharmacies and online for between $20-$60, but many experts say this tool isn't appropriate for everyone.

Chaddha only recommends monitoring your oxygen levels at home if you have the coronavirus and previous low oxygen levels, and your condition is not yet improving.

Hill, meanwhile, called the idea that every Covid-19 patient get a pulse oximeter "premature". He suggested that if you're in a high-risk group, talk to your doctor about pulse oximetry. You should also ask for advice on which device to purchase and training on how to use it. Inaccurate readings only further overwhelm the health care system.

Ultimately, the existence of silent hypoxia isn't a reason to believe your health could be failing with little to no signs. As Chaddha explained, "Don't get worried about it, but be aware of it."

- This article first appeared on Today

Read Full Story Click here to comment

FROM OUR PARTNERS