‘Happy’ Hypoxia: The Silent Sinister

By Alicia Tan Siew Yik and Kousalya Vijendran (BAC Apprentices) 


The COVIDNOW portal reports a downward trend in daily new cases, hospitalisations, and fatality rates. This is a far cry from just a few weeks ago. Individuals who are suspected of or have tested positive for Covid-19 Category 1 (asymptomatic) and Category 2 (symptomatic – showing mild symptoms) are instructed to undergo home quarantine by the Ministry of Health (MOH). Only a small number of patients in Categories 4 and 5 require hospitalisation and oxygen. Though this may appear to be a relief for those dreading hospitalisation, there may yet be something sinister lurking in the shadows. It’s called ‘silent’ or ‘happy’ hypoxia.  


What is hypoxia? 

When your body does not receive enough oxygen, you may experience hypoxemia (low oxygen in your blood) or hypoxia (low oxygen in your tissues). While hypoxia can be caused by hypoxemia, sometimes both these terms are used interchangeably to describe these problems. Ordinarily, when a person is experiencing low oxygen level, the body detects it and attempts to compensate by stimulating multiple accessory respiratory muscles, such as the intercostal muscles. When one is out of breath, they usually pant thus increasing their breathing rate. Hypoxia is typically identified by a number of symptoms, including shortness of breath, chest pain, wheezing, and an increase in heart rate. Without oxygen, vital body organs like the brain, heart, liver, and kidneys can be damaged within minutes.  


What is ‘silent’ or ‘happy’ hypoxia? 

On the contrary, ‘silent’ or ‘happy’ hypoxia does not prompt any such noticeable external symptoms. The body receptors fail to sense the low oxygen level and do nothing to compensate for the low oxygen level. As this happens, the respiratory muscles do not commit to the extra work needed. There will be no panting or shortness of breath. They become unaware that they are being deprived of oxygen and their body will begin to deteriorate without them noticing. According to Dr. Nurul Yaqeen, an internal and respiratory specialist based at Sunway Velocity Medical Centre, Covid-19 can cause this due to the virus’s effect on a patient’s lungs. Although ‘silent’ hypoxia is not unique to Covid-19 patients, this phenomenon has been observed more frequently in those suffering from Covid-19 than in those suffering from other respiratory illnesses.  

The coronavirus primarily infects the lung causing inflammation. This impairs the ability of the lung to exchange oxygen optimally into the blood thus resulting in low oxygen levels in the blood. As patients focus on combating other Covid-19 symptoms such as fever, cough, and diarrhoea, their bodies begin to fight back against the lack of oxygen in the body by increasing breathing rate to compensate. Meanwhile, the body gradually adjusts to the lower levels of oxygen, similar to what happens when a person travels to high altitudes. They may be unaware of their accelerated breathing rate and therefore, do not seek help. This phenomenon explains why patients are brought in either dead or at a stage in which they cannot be saved.  

So, what can be done?  

Despite the fact that ‘silent’ hypoxia is deadly, it can be identified and treated. While the normal oxygen saturation in the bloodstream of a healthy individual range between 94 and 99 percent, anything less would necessitate medical attention. In order to stay ahead of ‘hypoxia’, patients who are quarantined at home for Covid-19 are strongly advised to check their blood oxygen levels at least three times per day. A pulse oximeter, which is available at most local pharmacies, can be used for this purpose. This enables the patient to closely monitor his or her oxygen level. A low oxygen level requires immediate medical attention. The patient will need to be put on a ventilator to restore healthy blood oxygen levels.  

The challenge in this post-Covid-19 vaccination era is that some people may be infected without even realising it as most cases are asymptomatic. With the virus’ never-ending mutations, we must ensure that we practise regular self-testing. Early detection is critical to ensure the safety of you and your loved ones.