What Is Hypoxaemia?

Hypoxaemia is a condition where there are less than normal amounts of oxygen in the blood. Many important metabolic processes in our bodies require oxygen. When the level of oxygen in your arteries drops below the normal range, it can impede these metabolic processes which can then lead to various health complications. In this article, we will examine the causes, symptoms, diagnosis, and treatment options of this condition.

Overview

To understand hypoxaemia, we need to first understand oxygen saturation and haemoglobin. Haemoglobin is a protein present in red blood cells, which binds to oxygen and delivers it to the places it is needed in our bodies. Oxygen saturation refers to the amount of haemoglobin in the blood that is bound to oxygen. Oxygen saturation is measured as a percentage, and a range of  95 to 100 per cent is considered normal. One is considered to be hypoxaemic when their oxygen saturation drops to 95 per cent or less while they are at rest.¹ This may be caused by several different reasons such as a decreased availability of oxygen in the environment (like in the case of high altitudes), or an impairment in the individual's lung function.

Causes of hypoxaemia

Hypoxaemia can be caused by a decreased oxygen supply to the body, a decreased intake or decreased absorption by the body. These are some conditions that could lead to hypoxaemia:

Anaemia: this is a decrease in the amount of red blood cells in the blood. A decrease in red blood cell numbers automatically means fewer haemoglobin numbers and, by extension, less oxygen in the blood. Hypoxaemia is one of the complications of anaemia.

Chronic obstructive pulmonary disease (COPD): COPD consists mainly of two lung diseases, chronic bronchitis and emphysema. Over time, these conditions lead to the thickening of the walls of the airways in a person's lungs, causing a ventilation-perfusion mismatch. This is a condition where there is adequate oxygen going into the lungs, however, it is not getting absorbed enough for sufficient oxygen to enter the blood.

Heart conditions: your heart pumps oxygen-rich blood to the body, but also collects blood from the body and returns it to the lungs to be reoxygenated. Heart conditions, such as atrial septal defects and ventricular septal defects, cause the mixing of oxygen-rich blood from the lungs with less oxygenated blood collected from the body, leading to the heart pumping blood with less oxygen to your body.

Sleep apnoea: sleep apnoea is a disorder that involves an individual having intermittent episodes where they stop breathing or take shallow breaths while asleep. These episodes can last for seconds to minutes and for a lot of patients, the cycle continues throughout the duration of sleep. During those breathless episodes, the lungs and body do not get oxygen, which leads to hypoxia. Severe sleep apnoea over time leads to hypoxaemia.²

Altitude sickness: also referred to as “mountain sickness”, altitude sickness is a condition caused by a rapid ascent from a lower altitude to a higher altitude without allowing time for the body to acclimatise. Mountain sickness commonly occurs at elevations 3,000–5,000 metres above sea level.³ The pressure of oxygen in the air decreases with increasing altitude leading to decreased oxygen intake. The sudden fall in oxygen supply to the body results in symptoms like shortness of breath, fatigue, headaches, and dizziness.

Signs and symptoms of hypoxaemia

Symptoms of hypoxaemia can be non-specific or resemble other conditions:

• Difficulty breathing
• Chest pain
• Fatigue
• Headache
• Dizziness
• Rapid breathing 
• Confusion 

Because they are not very specific, it is important to consult a healthcare professional for advice.

Management and treatment for hypoxaemia

The management and treatment of hypoxaemia involve identifying and addressing the underlying cause. A treatment plan will depend on the severity and underlying condition, and the degree of hypoxaemia. These may include:

Oxygen therapy: providing supplemental oxygen is often the first-line treatment for hypoxaemia. Oxygen delivery can be achieved through a mask, nasal prongs, or a ventilator. This helps to increase the oxygen concentration in the inhaled air. It is especially useful in cases where the cause of hypoxaemia is sleep apnoea or heart failure.²

Medication: medications that treat the underlying cause of hypoxaemia rather than hypoxaemia directly are used concurrently with other therapies such as supplemental oxygen. Antibiotics may be prescribed in cases of lung infections. Bronchodilators and diuretics also help in alleviating symptoms of some lung conditions that lead to hypoxaemia.

Pulmonary rehabilitation: pulmonary rehabilitation involves a combination of breathing techniques, exercises, and education, to help improve lung function, especially in patients with lung injuries or chronic lung diseases.

Surgical interventions: surgery may be necessary for some lung or heart conditions that cannot be managed with medication alone. Repair of structural defects, as well as transplants, help in resolving conditions contributing to hypoxaemia.

Lifestyle modifications: small lifestyle changes such as avoiding or quitting smoking, maintaining a healthy BMI, and engaging in regular exercise can help prevent conditions that may lead to hypoxaemia. Regular aerobic exercise enhances heart and lung function, ultimately improving oxygen availability in the blood.

Diagnosis

If your healthcare provider suspects that you may be suffering from hypoxaemia, they will first assess your medical history and conduct a physical examination and an assessment of your vital signs (including oxygen saturation levels, heart rate, and respiratory rate) to determine a cause and gauge the severity. After an initial evaluation, your healthcare provider might order further tests to confirm the diagnosis. These may include:

Pulse oximetry: a small device called a pulse oximeter is attached to the patient’s finger to measure the blood oxygen saturation or percentage of oxygen in the blood. It is a quick, non-invasive test that can be done in the doctor’s office or at the patient's bedside. While it is quick and easy to perform, it is not as reliable as other tests so is often used as an initial screening test or in conjunction with other tests. 

Blood tests: arterial blood gas (ABG) tests are performed on a blood sample taken from a patient’s artery. This directly measures the arterial oxygen saturation, as well as other gases present in the blood like carbon dioxide. This is more accurate than pulse oximetry.

Imaging tests: imaging tests like X-rays or computed tomography (CT) scans may be performed to assess the heart and lungs to evaluate their structure and condition.

Pulmonary function tests: assessing lung function helps determine if the cause of hypoxaemia is the lungs or other organs. They can also be used to determine the type and severity of lung diseases.

Complications

Complications of hypoxaemia vary depending on the cause, severity, and the amount of time an individual has been hypoxaemic.

Organ damage: prolonged hypoxaemia may lead to damage to some organs like the kidneys.

Cardiac complications: when there is hypoxaemia, the heart tries to compensate by pumping harder and faster. This puts strain on the heart over time and leads to hypertension and heart failure.

Pulmonary hypertension: this is when there is high blood pressure in the arteries of the lungs. When there is a low percentage of oxygen in the blood, the arteries in the lungs shrink. This increases the pressure within the walls of the arteries. If the hypoxaemia continues for a long time after pulmonary hypertension develops, it could eventually lead to heart failure.

FAQs

How can I prevent hypoxaemia?

Preventing hypoxaemia involves maintaining good respiratory and cardiovascular health. Some measures that can help reduce the risk of hypoxaemia are:

• Avoid smoking
• Adopt a healthy lifestyle with regular aerobic exercise 
• Maintain a healthy BMI 
• Regular visits with your healthcare provider for health maintenance, especially if you suffer from any chronic conditions

How common is hypoxaemia?

Hypoxaemia is a relatively common condition, particularly among individuals with chronic heart and lung disorders. The prevalence of hypoxaemia will vary depending on gender and age, as well as many other factors associated with the population being studied and the specific criteria used to define the condition.

Who is at risk of hypoxaemia?

The following people are at greater risk of hypoxaemia:

• People with chronic respiratory conditions
• People with heart conditions
• People ascending to high altitudes 
• People with blood conditions like anaemia

What can I expect if I have hypoxaemia?

Patients suffering from hypoxaemia have varied symptoms depending on the severity and if the hypoxaemia is acute or chronic:

Breathlessness: even when at rest or during minimal activity.

Rapid breathing: your body attempts to take in more air to compensate for the low blood oxygen levels.

Cyanosis: often occurs with severe hypoxaemia, this is a bluish discolouration of parts of the body (especially the extremities) due to low oxygen levels.

Confusion: confusion occurs in cases of acute or severe hypoxaemia as it begins to affect brain function.

Fatigue: low oxygen levels can result in persistent tiredness or lack of energy, even after adequate rest.

When should I see a doctor?

If you suspect hypoxaemia or are experiencing symptoms such as shortness of breath, fatigue, headaches, or dizziness, it is important to consult your healthcare provider for evaluation and appropriate management. Patients with chronic heart and lung conditions should have regular check-ups with their healthcare provider.

Summary

Hypoxaemia is a condition characterised by low blood oxygen levels. Various conditions may cause an individual to develop it. The most common conditions that lead to hypoxaemia are those that affect the heart and lungs. Other factors are high altitude and anaemia. Symptoms of hypoxaemia can be non-specific, however, recognising the symptoms is crucial for early diagnosis and prompt treatment. Treatment for hypoxaemia focuses on addressing the root cause of the condition and may include lifestyle modification, medication, supplemental oxygen, and surgery in some cases.