Respiratory failure happens when the respiratory system is unable to maintain adequate gas exchange. This can lead to low levels of oxygen in the blood, known as hypoxaemia, and in some cases high levels of carbon dioxide, known as hypercapnia.
Respiratory failure can develop suddenly or over a longer period of time. It may be caused by conditions affecting the lungs themselves, the muscles involved in breathing, the brain’s control of breathing, or other parts of the body involved in supplying oxygen.
How does normal respiration work?
Normal respiration depends on several processes working together.
- Oxygen intake: When we breathe in, oxygen enters the lungs.
- Gas exchange: Oxygen passes from the lungs into the bloodstream, while carbon dioxide moves from the blood into the lungs.
- Oxygen transport: Oxygen-rich blood is carried by the heart to the body’s organs and tissues.
- Carbon dioxide removal: Carbon dioxide is breathed out of the body.
The lungs, heart, respiratory muscles and brain all play an important part in this process.
When any part of this system is significantly impaired, the balance of oxygen and carbon dioxide in the blood can be disrupted, leading to respiratory failure.
What causes respiratory failure?
Respiratory failure can be caused by a wide range of conditions.
Some affect the lungs and interfere with oxygen entering the bloodstream, while others affect breathing itself and reduce the body’s ability to remove carbon dioxide.
Common causes include:
- Chronic obstructive pulmonary disease (COPD)
- Pneumonia
- Severe asthma
- Pulmonary oedema
- Acute respiratory distress syndrome (ARDS)
- Pulmonary embolism
- Pulmonary fibrosis
- Pneumothorax
- Pulmonary hypertension
- Bronchiectasis
- Neuromuscular disorders
- Drug overdose or poisoning
- Head or neck injuries
- Obesity
- Certain heart conditions
The underlying cause can influence both the type of respiratory failure that develops and the treatment required.
What are the types of respiratory failure?
Respiratory failure is commonly divided into two main types according to the levels of oxygen and carbon dioxide in the blood.
Type 1 respiratory failure
Type 1 respiratory failure occurs when the level of oxygen in the blood is low, while the carbon dioxide level is normal or low.
It is usually associated with conditions that interfere primarily with oxygen exchange in the lungs.
Common causes include:
- Pneumonia
- Pulmonary oedema
- Acute respiratory distress syndrome (ARDS)
- Pulmonary embolism
- Pulmonary fibrosis
- Asthma
- Pneumothorax
- Pulmonary hypertension
- Bronchiectasis
Type 2 respiratory failure
Type 2 respiratory failure occurs when the level of oxygen in the blood is low and the carbon dioxide level is high.
This usually happens when ventilation is inadequate and the body is unable to remove carbon dioxide effectively.
Common causes include:
- COPD
- Severe asthma
- Drug overdose or poisoning
- Neuromuscular disorders
- Muscle disorders
- Head or neck injuries
- Obesity
- Hypothyroidism
Acute and chronic respiratory failure
Respiratory failure can also be classified according to how quickly it develops.
Acute respiratory failure
Acute respiratory failure develops rapidly, usually over minutes or hours.
It can occur in people with previously normal lung function or during a sudden worsening of an existing respiratory condition.
Examples include:
- A severe asthma attack
- Acute respiratory distress syndrome
- Severe pneumonia
Acute respiratory failure requires urgent medical assessment and treatment.
Chronic respiratory failure
Chronic respiratory failure develops more gradually, usually over days or longer.
It is often associated with long-term respiratory conditions where the body has had time to partially adapt to reduced respiratory function.
Examples include:
- COPD
- Interstitial lung disease
Acute-on-chronic respiratory failure
Acute-on-chronic respiratory failure occurs when someone with existing chronic respiratory failure experiences a sudden deterioration.
Examples include:
- An acute COPD exacerbation
- A respiratory infection in someone with pre-existing chronic lung disease
What are the symptoms of respiratory failure?
Respiratory failure can develop gradually or appear suddenly.
Some people with slowly developing respiratory failure may adapt by reducing their level of physical activity, which can make the symptoms less obvious initially.
Symptoms can include:
- Shortness of breath, initially on exertion and potentially later at rest
- Tiredness
- A bluish tinge to the lips or fingers, known as cyanosis
- Confusion
- Reduced consciousness
- Wheezing
- Chest pain
- Muscle or limb weakness, depending on the underlying cause
Severe or rapidly worsening breathing difficulty, confusion, reduced consciousness or blue lips or skin require urgent medical attention.
How is respiratory failure assessed?
A doctor will assess both the severity of the respiratory failure and the condition causing it.
Clinical signs may include:
- A high respiratory rate
- Cyanosis
- Restlessness or anxiety
- Confusion
- Reduced consciousness
- Abnormal lung sounds
- Signs of fluid retention or right-sided heart failure
How is respiratory failure diagnosed?
Arterial blood gas analysis
An arterial blood gas test is an important investigation in diagnosing respiratory failure.
It measures the amount of oxygen and carbon dioxide in the blood and can help determine whether someone has Type 1 or Type 2 respiratory failure.
Blood is usually taken from an artery at the wrist, although other sites may sometimes be used.
Investigating the underlying cause
Further investigations depend on the individual patient’s symptoms and clinical findings.
These may include:
- Chest X-ray
- Blood tests
- Full blood count
- Kidney and liver function tests
- Troponin tests where heart damage is suspected
- Thyroid function tests
- Spirometry, particularly in chronic respiratory disease
- Echocardiography where a cardiac cause is suspected
Identifying the underlying cause is an essential part of deciding on the most appropriate treatment.
How is respiratory failure treated?
Treatment depends on the severity and cause of the respiratory failure.
Acute respiratory failure and newly diagnosed severe respiratory failure may require admission to hospital and, in some cases, treatment in an intensive care unit.
The main aims of treatment are to improve oxygen levels, reduce excessive carbon dioxide where present, and treat the underlying condition.
Oxygen therapy
Supplemental oxygen may be given through a mask or other oxygen-delivery device.
The amount of oxygen required depends on the individual patient’s condition and blood gas results.
Ventilatory support
Some patients need additional help with breathing.
This may include:
Non-invasive ventilation (NIV):
A mask is used to support breathing without inserting a tube into the airway. This can be particularly useful in some patients with COPD and raised carbon dioxide levels.
Mechanical ventilation:
A breathing tube is inserted into the trachea and connected to a ventilator. This is used when respiratory failure is severe and the patient cannot maintain adequate breathing independently.
Extracorporeal membrane oxygenation (ECMO):
In selected severe cases, blood can be circulated through an external machine that adds oxygen and removes carbon dioxide.
Treating the underlying cause
Additional treatment may include:
- Antibiotics for bacterial infection
- Steroids for some inflammatory or obstructive respiratory conditions
- Treatment for heart disease or fluid overload
- Treatment of neurological or muscular conditions
- Other medicines depending on the underlying cause
Some people with chronic respiratory failure can be managed at home, depending on the severity of their condition, the underlying cause, other illnesses and their individual circumstances.
What complications can respiratory failure cause?
Respiratory failure can affect several parts of the body, particularly when oxygen levels remain low for a prolonged period.
Possible complications include:
- Pulmonary embolism
- Pulmonary fibrosis
- Pneumothorax
- Chronic respiratory failure
- Dependence on ventilatory support
- Heart complications
- Increased red blood cell count
- Blood clots
- Seizures
- Brain injury caused by prolonged low oxygen levels
- Hospital-acquired infections
- Muscle wasting
- Pressure sores
- Deep vein thrombosis
- Malnutrition during prolonged illness
The risk of complications depends on the severity and duration of the respiratory failure and the underlying medical condition.
What is the prognosis for respiratory failure?
The outlook varies considerably from person to person.
Important factors include:
- The underlying cause
- How quickly respiratory failure develops
- How quickly treatment begins
- The person’s age
- Other existing medical conditions
- Whether complications develop
Some people recover fully once the underlying cause is treated, while others may require ongoing respiratory support or long-term management.
In advanced or terminal illness, palliative care may form part of treatment.
Can respiratory failure be prevented?
Not every cause of respiratory failure can be prevented.
However, reducing the risk of serious respiratory disease can help.
One of the most important preventive measures is avoiding smoking or stopping smoking.
People with existing respiratory conditions should also follow their recommended treatment and seek medical advice if their symptoms deteriorate significantly.
Concerned about your respiratory symptoms?
If you would like specialist assessment or advice about ongoing respiratory symptoms, get in touch to arrange a consultation with Dr Shalin Diwanji.
Frequently asked questions about respiratory failure
Respiratory failure can be caused by conditions that affect the lungs, breathing muscles, nervous system or other parts of the body involved in maintaining normal oxygen and carbon dioxide levels.
Common causes include COPD, pneumonia, severe asthma, pulmonary oedema, pulmonary embolism, neuromuscular disorders and drug overdose.
Symptoms can include shortness of breath, tiredness, confusion, reduced consciousness and a bluish colour to the lips or fingers.
Symptoms can develop gradually or very quickly depending on the cause.
Type 1 respiratory failure occurs when blood oxygen levels are low while carbon dioxide levels remain normal or low.
It is commonly associated with conditions that interfere with oxygen exchange in the lungs.
Type 2 respiratory failure occurs when oxygen levels are low and carbon dioxide levels are high.
It usually develops when ventilation is inadequate and the body cannot remove carbon dioxide effectively.
Acute respiratory failure can be a medical emergency and may require immediate hospital treatment.
Sudden severe breathlessness, blue lips or skin, confusion or reduced consciousness should be treated as urgent symptoms.
Treatment depends on the underlying cause and severity.
It may include oxygen therapy, non-invasive ventilation, mechanical ventilation and treatment of the condition responsible for the respiratory failure.
