Early Detection of Silent Hypoxia

The development of Covid-19 has brought forth a new phenomenon that is increasingly challenging.

The development of Covid-19 has brought forth a new phenomenon that is increasingly challenging. Three patients in Banyumas reportedly appeared asymptomatic but then suddenly died.

According to a statement of Banyumas Regent Achmad Husein, all three of them seemed happy before they died. Unlike other Covid-19 patients, they had not shown any symptoms of cough, flu or fever. However, the oxygen saturation (the percentage of red blood cells that bind oxygen) continued to decline, leading to breathing failure. An examination then confirmed that the three were Covid-19 positive. This is what the public calls the “happy hypoxia” syndrome.

This syndrome is reported to have afflicted many Covid-19 patients. Before the pandemic, it has also been seen in other lung infections, atelectasis and intrapulmonary shunts, but it has increased rapidly because of Covid-19.

Essentially, this syndrome outwits the infected person, as if there is no breathing problems and the person appears to be in good health. However, the situation changes drastically as the patient suddenly has trouble breathing, which is quickly followed by breathing failure leading to death.

It comes as no surprise that the media hyperbolically promotes the term “happy hypoxia”, which is a condition where people experience hypoxia, or a lack of oxygen, but appear to still feel fine, even happy. The person does not feel that he or she is in trouble, even though their

life is in jeopardy. The medical community has long described this condition by a more realistic term, “silent hypoxia” (or hidden hypoxia. The term silent refers to the absence of symptoms of shortness of breath with a hypoxic body condition, even though it is accompanied by other symptoms, such as fever and cough and cold.

How do Covid-19 patients experience this silent hypoxia? As we all know, Covid-19 predominantly attacks respiratory cells. A severe form of this respiratory infection is pneumonia (inflammation of the lungs). Pneumonia that is caused by Covid-19 progresses very quickly and is often fatal, especially in vulnerable groups, such as those who have comorbidity factors, especially among the elderly. At first, they feel nothing is happening, but they are outwitted by a condition that progresses extremely fast and violently.

The drastic changes often occur in less than a week. The patient does not even realize that he or she is under a severe attack and their pneumonia has entered the severe category. The attacks can be very sudden, and the patient immediately become severely short of breath. Doctors do not have much of a chance to keep the patient breathing.


Against basic biology

In general, hypoxia is defined as a condition in which a person lacks oxygen in their body tissue (oxygen saturation is below 90 percent). This may happen as a result of changes in elevation and can be experienced by climbers of very high mountains, where oxygen is thin and the climbers have not prepared their bodies for the adjustment (acclimatization). In severe cases it can result in coma, even death. However, if the climber is brought to a lower place, his body will gradually return to normal.

This condition can also occur when someone has pneumonia due to Covid-19. Pneumonia due to Covid-19 is a new variant of pneumonia that has been reported by many hospitals, where many of their critical patients are affected by Covid-19 inflammation. However, there is something interesting. Many patients “do not feel” respiratory problems, while in fact they have Covid-19 pneumonia. The specifics in these cases can vary.

There are patients whose X-ray results initially show only mild inflammation of the lung, which worsens drastically within days. A new X-ray would then point to very severe pneumonia.

Another example is a patient who has a CT scan to check for injuries after a fall. The CT scan also shows pneumonia. Another, elderly patient faints without knowing why, and yet another patient has diabetes. When both of them are examined and subjected to X-rays tests, it turns out that both of them are infected with Covid-19. That comes as a surprise, because they generally don’t report complaints about breathing, despite the oxygen level in their blood being below normal.

These all describe the uniqueness of lung inflammation triggered by Covid-19. Generally, pneumonia is a lung infection, in which the air bag is filled with liquid. The patient experiences chest pain and shortness of breath. However, in cases of Covid-19 pneumonia, the patient does not initially feel short of breath.

In a healthy body, the oxygen saturation in the cells and body tissues ranges from 95-100 percent. If oxygen levels drop below 90 percent, in general, a person will begin to feel short of breath. If the drop is down to 50 percent, the shortness of breath will get worse. However, strangely enough, in the case of Covid-19, when the oxygen level drops below 90 percent, even down to 50 percent, patients often do not complain of shortness of breath, so they are not aware that they have pneumonia. When they finally get checked by a doctor, their lung inflammation may already be at a critical level.

A study published in the American Journal of Respiratory and Critical Care Medicine, as quoted by CNN Indonesia, reviews this silent hypoxia syndrome. According to Martin J. Tobin, a pulmonologist and author of the study, this syndrome has puzzled many physicians, because it conflicts with basic biological concepts. In some cases, the patient does not feel shortness of breath and their activity is not disturbed. When oxygen saturation drops, alarms in the brain do not respond until the oxygen reaches dangerously low levels.

There are numerous reports of people who had contracted Covid-19 pneumonia experiencing fever, cough, stomach pain and fatigue and being critically out of breath when they were finally admitted to the hospital.

Why many Covid-19 patients die suddenly, even though they did not feel short of breath (silent hypoxia), is not yet clear.

Physiologically, in the human body, there is a system of balance that plays a role in maintaining the body’s physiological functions to adapt, including adapting to sudden changes in elevation.

If someone who lives in Jakarta with an altitude of 5 meters above sea level goes by plane to an altitude of 9,000 m above sea level, then after landing, he or she can feel dizzy, nauseous and their ears are buzzing as if covered by air. However, their condition will gradually return to normal after adapting.

Therefore, this case of hypoxia does not occur in people who used to live in the highlands. Meanwhile, mountain climbers need camps for stops at various altitudes so that their body can adapt to the thinner air.

According to the Le-Chatelier principle, with the decrease in oxygen, the body balance will shift to the left, and as a result, the level of HbO2 (hemoglobin, red blood cells) in the blood decreases. As a result, the oxygen supply to the entire tissue is decreased. This is what causes nausea, dizziness, ringing in the ears and a feeling of discomfort.

This condition causes the body to adapt by producing as much hemoglobin as possible. With increasing hemoglobin concentration, it will shift the body balance back to the right and HbO2 will increase back to normal. This adjustment lasts 2-3 weeks. On average, people living in highlands have a higher hemoglobin level than the people living in lowlands.

What if the lungs are attacked by the Covid-19 virus? There are lung cells that produce surfactant, an important substance that helps the alveoli (air sacs) stay open when we exhale. When the Covid-19 virus infects the lungs, it causes inflammation in all components of the lung, including the surfactants. So important is the role of the surfactants that if they are destroyed, the air sacs are deflated and oxygen levels drop, sometimes dramatically.

We breathe to absorb O2 (oxygen) and emit CO2 (carbon dioxide) with the ability of CO2 to release 20 times easier than the entry of O2. Naturally, the alarm responding to difficulty of breathing is stimulated by sensors in the brain that detect high concentrations of CO2, not O2. At the beginning of the Covid-19 attack period, the lung condition is still unchanged, that is, CO2 can still be released. But the entry of O2 has begun to be disrupted (leading to hypoxia).

Low CO2 conditions do not result in a shortness of breath response. The patient still feels normal and comfortable. This is a false condition. Without realizing it, the body seems to tolerate the drop in oxygen levels in the blood. It is silent hypoxia.

This condition continues, as the air sacs collapse further, the pneumonia worsens, resulting in disruption of the CO2 releasing pathway and accompanied by a drop in oxygen saturation to a very low level (less than 50 percent). It is then that the patient begins to feel difficulty breathing with more severe failure of the organs. The patient will eventually breathe harder and deeper to draw in oxygen, which is very low, while CO2 has accumulated.

Unfortunately, it is too late, which makes breathing aid useless. The condition gets worse, the fluid builds up and the lungs become stiff. CO2 builds up, because it can’t be released completely. So the patient experiences acute respiratory failure because their oxygen level is very low and dangerous. Eventually, the patient needs a ventilator. According to many reports, ventilators are not of much help in patients who have reached the acute stage. This may explain why so many Covid-19 patients die suddenly, even though previously they had no complaints of shortness of breath. Silent hypoxia, which initially is not felt, develops rapidly into respiratory failure.


Easy oximetry detection

Covid-19 is a tremendous killing machine, targeting the lung. Because so many patients don’t go to hospital until their pneumonia has reached a severe stage, many end up on ventilators. This is why many hospitals fall behind due to lack of ventilators. The patient comes to the hospital in an emergency when his lungs is very tired.

From the above explanation, a simple method for early identification of suspected Covid-19 patients with symptoms such as fever, cough, cold and diarrhea is to monitor their pulse and their oxygen saturation with an oximeter. This is an initial method of identification while waiting for the PCR (polymerase chain reaction) test result, which is considered to be accurate in detecting Covid-19. Oximetry is placed at the fingertips to measure oxygen levels and increase in heart rate.

British Prime Minister Boris Johnson, who was tested positive for Covid-19, uses this simple tool to monitor the condition of his heartbeat and breathing. This simple method can help save patients as well as streamline the hospital management system.

Oximetry, which can be found at the pharmacy, can be a simple but effective tool to independently monitor the likelihood of developing hypoxia before going to the hospital. This early detection method will avoid our dependence on using a breathing machine or ventilator at any time. Amid the condition, where there is a continuing increase in the number of Covid-19 patients, both symptomatic and asymptomatic, it is increasingly urgent to get an early warning for the safety of ourselves and those around us.


Djoko Santoso, Professor of Internal Medicine, Faculty of Medicine, Airlangga University.