Hypoxia

Hypoxia are of four different types, and are clinically known as:

• Hypoxic hypoxia: Hypoxic hypoxia is a condition that can simply be described as the lack of saturated blood oxygen due to a low supply of oxygen in the air. It is the hypoxemic type of hypoxia, where there isn't enough oxygenated blood reaching the tissues of the body. It is also known as generalised hypoxia.
• Anemic hypoxia: The reduced amount of oxygenated haemoglobin means that blood isn't able to carry enough oxygen to different parts, leading to a development of this condition. This condition is seen during instances of carbon monoxide poisoning.
• Histotoxic hypoxia: In this condition, oxygen reaches the tissues but they are not able to utilise it due to poor functioning or damaged cells, stopping them from performing their function of extracting all the necessary oxygen from the blood. Blood-borne diseases, heart diseases and conditions concerning the circulatory system or lungs are all linked to this form of hypoxia. This type of hypoxia is also seen in alcohol or drug abuse, as well as cyanide poisoning.
• Stagnant hypoxia: In this type of hypoxia, the condition or quality of blood being supplied to the body may be fine, but it is the blood flow to the tissues that may be disrupted or become uneven. Conditions that develop over time and cause heart attacks or heart failure can lead to the slowing down of blood circulation or inadequate distribution of blood to different parts of the body, leading to hypoxia.

Besides these four types of hypoxia, anoxia is an extreme form of the condition, in which there is no oxygen left in the tissues and cells of the body, making it life-threatening.

COVID-19 is a respiratory disease that has caused millions of infections and thousands of deaths around the world. It has also given rise to a previously unknown condition dubbed happy hypoxia or silent hypoxia.

Happy hypoxia is a peculiar condition in which patients of COVID-19 develop dangerously low levels of blood oxygen but without any interim sign of difficulty breathing.

Typically in cases of hypoxia or hypoxemia, patients complain of shortness of breath (also known as dyspnea) soon after the problem begins. However, patients with happy hypoxia in COVID-19 don't experience this symptom until their blood oxygen drops dangerously low. The patients, as a result, are able to perform their daily tasks without any complaints.

The absence of shortness of breath as a symptom has, however, allowed medical practitioners to give treatment to COVID-19 patients without putting them on a ventilator or resorting to intubation, although the presence of this condition has been baffling for researchers and medical professionals alike. (Read more: Risk of intubation and ventilator use in COVID-19 patients)

There are a number of symptoms that can be present in a patient in the case of hypoxia:

• Shortness of breath
• Headaches
• Lightheadedness
• Fatigue
• Nausea and vomiting
• Wheezing
• Discolouration of the skin: the tip of the fingers, toes or nails may become blue, a condition that is known as cyanosis
• High blood pressure during onset, followed by low blood pressure during the development of the condition
• Palpitations in the early stages, causing irregular heartbeat or arrhythmias
• Confusion, loss of cognitive functions or loss of memory
• Feeling disorientated or loss of coordination in movement
• Severe cases may involve loss of consciousness, seizures, coma or death
• An abnormal increase in the red blood cells, also known as secondary polycythemia

The different types of hypoxia are caused by different factors.

• Hypoxic hypoxia may be caused by a lack of breathable atmospheric oxygen at high altitudes in the mountains, among pilots flying their aircrafts, or deep sea divers. This generalised type of hypoxia is also experienced by people suffering from cardiopulmonary episodes, as the lungs are unable to supply oxygen to the blood.
• Hypoxia is also seen in preterm births (newborns who had less than 37 weeks of gestation), as their lungs are not fully developed in the womb.
• COVID-19 patients may experience silent hypoxia or happy hypoxia without the onset of symptoms until there is a drastic drop in blood oxygen levels.
• Anaemic hypoxia may be caused by any condition in which the haemoglobin in our blood binds with molecules other than oxygen. Example, carbon monoxide poisoning.
• Stagnant hypoxia develops due to the faulty supply of blood to the tissues and cells, caused by heart diseases or sudden trauma such as heart failure or heart attacks, or any other condition restricting the normal circulation of blood to the tissues.

Generalised hypoxia may be triggered in respiratory conditions such as pneumonia or chronic problems such as asthma or COPD. Preventing episodes and sudden onset of the above-mentioned symptoms is critical to managing this condition. Carrying an inhaler that helps in easing breathlessness or other medicines that do so is extremely important.

Certain lifestyle changes such as eating a balanced diet rich in different kinds of nutrients and remaining active—with about 150 minutes of mild to moderate levels of exercise in a week—are a good way to keep respiratory conditions at bay, as they help in strengthening the tissues in the lungs, allowing them to take up more oxygen per breath.

Being aware of your surroundings, and knowing what triggers your asthma or other respiratory infections is also important. Avoiding polluted areas, smoke from vehicles or allergens and remaining in a calm, peaceful atmosphere can help in keeping your triggers at bay.

Hypoxia can be diagnosed with the help of a simple device known as a pulse oximeter—just clip it in on the tip of your finger or ear, and it calculates the oxygen saturation level in your blood. Readings above 94% are usually a sign of good blood oxygen levels, but anything below that should be observed closely. (Remember, a pulse oximeter may not be effective for some patients, such as diabetics.)

Visit a doctor or an emergency room if oxygen saturation drops below 92%. Oxygen may need to be supplied artificially if the blood oxygen levels are below 92% (this figure may be higher or lower for some people).

If you have diabetes or hypertension, check with your doctor about the normal range of blood oxygen saturation for you and the right way to monitor your blood oxygen levels.

X-rays help to look at the health of the lungs. Pulmonary function tests are also sometimes ordered to look for the cause behind the low levels of oxygen in the body, while other tests may be required to check for carbon monoxide poisoning.

To relieve the symptoms of hypoxia, oxygen is supplied to the body artificially as the lungs aren't able to perform their task. Solutions such as oxygen therapy, ventilators, ECMO or extracorporeal membrane oxygenation are used in clinics and hospitals.

Hypoxia often occurs due to an underlying problem affecting the lungs, hence stabilising the breathing function is important before performing further tests.

• The use of oxygen tanks to supply the patient with oxygen is important from the moment they are admitted in a hospital.
• Doctors will then assess the situation and see if the patient needs to be put on a ventilator to stabilise his/her condition.
• The use of certain inhalers in the case of underlying asthma or COPD may also be required to improve the condition of the patient suffering from hypoxia.