Health Tips

Some of you might heard of a term called ‘happy hypoxia’. Do you know what is that?

Okay, let’s break the words down:

Happy: Hmm… I believe this doesn’t need much explanation

Hypoxia: Refers to low oxygen saturations 

Together, it actually means despite many of the COVID-19 patients having low oxygen level, but they DO NOT suffer from breathing difficulty. Which is actually DEFYING basic biology.

Well, let me explain it further.

Happy hypoxia (or silent hypoxemia)

FYI,

Hypoxia is a condition where the oxygen supply is insufficient for normal life functions;

Hypoxemia is a condition where there is a low arterial oxygen (blood oxygen) supply 

In some publications these terms are used interchangeably.

A normal oxygen saturation (or blood oxygen level) is 95 to 100%, anything lower than 92% is considered as hypoxemia. A 80-85% blood oxygen level is viewed as life threatening condition. While hypoxia is an alarming sign for imminent failure of vital body organs such as the heart and brain, usually with the symptom of difficult in breathing, happy hypoxia does not elicit any of such obvious external sign. Therefore the COVID-19 patients seem to be ‘happy’ as they could swipe their phones, talk to the doctors etc., while their blood oxygen level are worryingly low.

Why do COVID-19 patients have low oxygen saturations?

Many researchers and medical experts agree that clotting in the alveoli (the small blood vessels in the lungs) is considered the primary cause of hypoxia. This is because of the inflammatory reactions in the alveoli, instigates a cascade of proteins that prompts blood clotting, therefore preventing sufficient oxygen supply to the lung tissues and cells.

Now that we have discussed about the cause of hypoxia. Let’s talk about features that could lead to dyspnea (difficulty in breathing):

• Low oxygen saturations a.k.a hypoxia
• Stiff or fluid-filled lungs
• Increased level of carbon dioxide as they lungs couldn’t expel it efficiently 

Severe hypoxia cases would lead to dyspnea. Clinically saying, the presence of dyspnea would be no surprise in hypoxia. Surprise would arise only if hypoxemia triggered significant stimulation in the respiratory centers and the patients did not develop dyspnea. In COVID-19 serious cases, patients struggle to breathe with damaged lungs, but in the early phase, low oxygen saturation isn't always appeared with obvious respiratory difficulties. Carbon dioxide levels can be normal, and breathing deeply is comfortable. This can be dangerous because these patients can quickly collapse and require urgent access to ventilators (the machines that support their breathing). 

Now, here comes the question: How do I know if my oxygen saturation is low if I am asymptomatic?

Do you still remember the trend of people panic buying pulse oximeter, which happened not long ago?

Yes! this is what I’m talking about.

What is a pulse oximeter used for?

Pulse oximeter measures the blood oxygen level and heart rate, by clipping firmly on to your fingertip and painlessly analyses two wavelengths of light from blood flowing through that region. It is one of the easiest way to measure oxygen saturation.

Should you invest in a pulse oximeter?

While pulse oximeter can help detecting the fall of blood oxygen level in the early phase of COVID-19, it CANNOT replace COVID-19 test. In other words, pulse oximeter CANNOT diagnose COVID-19. However, they can alert patients who are already COVID-19 infected when their blood oxygen levels are falling. Thus it is beneficial for COVID-19 patients who have symptoms such as fever, cough and dyspnea or, those at high risk of developing serious symptoms, like the elderlies and those with medical conditions such as serious heart or lung conditions.

Meanwhile, having breathing difficulty and low oxygen saturations are just two possible COVID-19 symptoms, and it’s important to know all of the symptoms. Here is a list of COVID-19 symptoms compiled by Centers for Disease Control and Prevention (CDC).

Source from CDC: Symptoms of COVID-19

Whereas for people who are young and healthy, and have no COVID-19 symptoms, it’s not necessary to have a pulse oximeter at home. In addition, people who plan to use the device are advisable to seek for guidance from the medical professionals, in order to utilize the device properly and be able to interpret the readings correctly.

Factors that are affecting the accuracy of the pulse oximeter reading

• Poor blood circulation (eg. cold extremities) 
• Skin pigmentation (pulse oximeter is proven to be less accurate in people with darker skin tones)
• Skin thickness 
• Skin temperature
• Current tobacco use
• Use of fingernail polish
• Other lung diseases such as asthma or lung infections

Pulse oximeter has 2% error window, meaning the reading might be 2% higher or lower than the actual blood oxygen level.

Take-home messages

• Do not rely solely on a pulse oximeter to assess your health condition or oxygen level.
• Monitor yourself for other COVID-19 symptoms even if your pulse oximeter reading is normal.
• Seek doctor immediately if your:
  • Lip colour changes from the natural shade to appear blue
  • Skin colour changes from the original tone to a red/purple appearance 
  • Persistent sweating even when you do not perform high intensity exercises or in a hot surrounding 
  • Have difficulty in breathing

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Disclaimer: As a service to our users and general public, Doc2Us provides health education contents. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

References:

1. Netmeds. Happy Hypoxia: Decoding The Mystery Behind Why Oxygen Levels Decline In COVID-19 Patients
2. Science. The Mystery of the Pandemic’s ‘Happy Hypoxia’
3. Yale Medicine. Should You Really Have a Pulse Oximeter at Home?
4. FDA. Pulse Oximeter Accuracy and Limitations: FDA Safety Communication

Written by

Ms. Elaine Fung