Respiratory failure occurs when the breathing system fails to keep adequate blood oxygen levels. There may also be difficulties in removing waste gases, mainly blood carbon dioxide.
What causes it?
Every time we take a breath in we are taking oxygen from the air down to the lungs which then crosses over into the blood and is then transported to the various organs. At the same time carbon dioxide, which is the waste gas produced by organs, crosses from the blood and into the lungs - we then breathe this out. This whole process requires an interplay of various systems such as the lungs, the heart, the chest muscles and the brain. When any of these are impaired we are at risk of respiratory failure. Respiratory failure is defined by low blood oxygen levels and there may also be raised blood carbon dioxide levels.
There are various causes of respiratory failure, the most common being due to the lungs or heart. The lung disorders that lead to respiratory failure include chronic obstructive pulmonary disease (COPD), asthma and pneumonia. Heart disease that can lead to respiratory failure can be heart failure which may or may not be accompanied by a heart attack.
Read more about the causes of respiratory failure.
What do I feel when it happens?
Very early on there may not be any symptoms or just tiredness after exertion. Gradually, as the respiratory failure worsens, there is an inability to get oxygen to the body's organs. The most common features are shortness of breath (which may be at rest or on exertion) and becoming tired easily. There may also be symptoms of the underlying causes, such as a raised temperature in pneumonia or leg swelling in heart failure.
Learn about the symptoms of respiratory failure.
Do I need any further tests?
People with sudden respiratory failure or new respiratory failure are likely to need urgent hospital admission. Further tests will be required to make the diagnosis and to find the underlying cause. These tests are likely to include blood tests, a chest X-ray, a heart ultrasound scan (echocardiography) and a computerised tomography (CT) scan of the lungs.
Discover more about the diagnosis of respiratory failure.
How is it treated?
Treatment of sudden or new respiratory failure often requires emergency measures to make the patient more stable medically. This may require resuscitation and artificial ventilation. Patients may need to be admitted to the intensive care unit or the high dependency unit (based on how unwell the patient is).
Treatment will aim to improve the blood oxygen levels and remove the waste gas carbon dioxide if it is raised. This will usually require artificial ventilation. Further treatment will be aimed towards the underlying cause, such as antibiotics in pneumonia or diuretics in heart failure.
Some patients may become worse despite treatment and they may not survive. If someone can no longer be treated with a view to cure, but still needs symptom control, they may be referred to the palliative care team in hospital or to the Macmillan nurses in the community.
Read more about the treatment of respiratory failure.
Does it lead to any complications?
Respiratory failure is a serious illness and it may take many days to weeks for the patient to get better. Complications can occur at any stage of the illness and can affect a number of the body's organs. For example, severe lung illness can make a blood clot in the lung more likely. Artificial ventilation can lead to irreversible scarring of the lungs which can make respiratory function worse.
Not smoking and stopping smoking are important to preserve healthy lungs.
Learn about the complications of respiratory failure.
What are the symptoms of respiratory failure?
It is possible that respiratory failure can occur slowly and that patients adapt, such as walking slower and avoiding physical tasks. This is less common and patients may complain of the following symptoms:
- Shortness of breath - at first, this may happen only on exertion; however, later on it may also occur at rest and when trying to sleep.
- Tiredness - this is due to a lack of oxygen getting to the body's organs.
- A bluish tinge to the hands or lips - the medical term for this is 'cyanosis'. It can be noticed when at rest and may worsen with exertion.
- Confusion and reduced consciousness - this can occur when either the blood oxygen levels are low or when the carbon dioxide level increases.
- There may also be features of the underlying cause - for example, chest pain in heart disease, weakness of limbs in neurological disorders, wheeze in asthma.
When the healthcare professional makes an assessment, they may find the following:
- High breathing (respiratory) rate.
- A bluish tinge to lips and fingers (cyanosis).
- Restlessness, anxiety, confusion, fits (seizures) or coma - these can occur due to the abnormalities in blood gases.
- On listening to the lungs there may be noises suggestive of infection, fluid overload or asthma, depending on the underlying cause.
- There may also be features of right-sided heart failure which can occur due to the strain on the heart. This is called 'cor pulmonale' and there will be fluid retention evidenced by an enlarged liver, swelling of the tummy (abdomen) and swelling of the legs.
What are the causes of respiratory failure?
When we breathe we are taking in oxygen which then passes to the blood and can be used by cells for daily functions. At the same time, waste gas called carbon dioxide is also taken from the blood and enters the lungs. We then breathe this out.
In order for us to breathe, not only the lungs are involved but also the muscles of the chest wall, and the brain (which co-ordinates our breathing). The heart is also important.
Types of respiratory failure
Respiratory failure can be divided into two types:
- Type I respiratory failure - the blood oxygen is low and the carbon dioxide is normal or low.
- Type II respiratory failure - the blood oxygen is low and the carbon dioxide is high.
Respiratory failure can also be described according to the time it takes to develop:
- Acute - happens within minutes or hours; usually, the patient has no underlying lung disease.
- Chronic - occurs over days and usually there is an underlying lung disease.
- Acute on chronic - this is usually a sudden or quick worsening of the respiratory function in someone who already has chronic respiratory failure.
Causes of respiratory failure
Common causes of type I respiratory failure
- Chronic obstructive pulmonary disease (COPD).
- Pulmonary oedema.
- Pulmonary fibrosis.
- Pulmonary embolism.
- Pulmonary hypertension.
- Cyanotic congenital heart disease.
- Acute respiratory distress syndrome.
- Respiratory illness associated with HIV infection.
Common causes of type II respiratory failure
- Severe asthma.
- Drug overdose, poisoning.
- Myasthenia gravis.
- Muscle disorders.
- Head injuries and neck injuries.
- Pulmonary oedema.
- Acute respiratory distress syndrome.
How is the diagnosis of respiratory failure made?
The diagnosis of respiratory failure requires an arterial blood gas which provides information on the levels of the blood oxygen and carbon dioxide levels. An arterial blood gas simply involves a needle connected to a syringe, which is then inserted at the wrist directly into the point where the pulse can be felt. Sometimes the pulse at the wrist is weakened and so a different site has to be used and this is usually the groin and, less commonly, the elbow.
Finding the underlying cause of respiratory failure
Once the diagnosis has been made, further investigations will be required to find the underlying cause. This may include:
- Chest X-ray: this may show infection, fluid or tumours of the lung.
- Blood tests: these may include full blood count, kidney tests and liver function tests. They may help to work out the cause and also to detect any factors that may be worsening the respiratory failure, such as a low blood haemoglobin level (anaemia).
- Troponin blood tests: these are used to determine if there has been recent heart injury - for example, a heart attack which may have caused the respiratory failure.
- Thyroid function tests: an underactive thyroid gland, when a long-term (chronic) condition, may cause respiratory failure with a raised carbon dioxide level.
- Spirometry: this is used to measure the lung volumes and capacity and is useful in the evaluation of chronic cases.
- A heart ultrasound scan (echocardiography): this can look for cardiac causes, such as a leaking heart valve or heart failure.
What is the treatment for respiratory failure?
Patients with sudden-onset (acute) respiratory failure or a new diagnosis of chronic respiratory failure need to be admitted to hospital immediately. They need to be resuscitated and may need admission to an intensive care unit with artificial ventilation and life support. On the other hand many patients with chronic respiratory failure can be treated at home. This will depend on how severe the respiratory failure is, the underlying cause, whether other illnesses are present and the patient's social circumstances. Some patients may need ventilators at home and oxygen support.
Treatment will be directed towards correcting the blood oxygen and carbon dioxide levels and treating the underlying cause.
Treatment of respiratory failure
This may include:
- Oxygen - high levels will be given through a mask (although lower levels may be needed in patients with chronic respiratory failure who have adapted to high carbon dioxide levels).
- Artificial ventilation:
- Mechanical ventilation:
- This involves the patient being put into a coma, using medication and paralysing their breathing.
- A tube is inserted into the trachea and an artificial ventilator then does the work of breathing.
- Once the underlying cause is treated, patients will be 'weaned' off the ventilator so that their lungs start to do the work of breathing.
- This is a form of 'invasive' ventilation.
- Non-invasive ventilation (NIV):
- This is an alternative to invasive ventilation and is increasingly being used, especially in cases where weaning from an artificial ventilator may prove difficult.
- It is used when there is a low blood oxygen level and high blood carbon dioxide level, ie type II respiratory failure. The main disease it is used in is chronic obstructive pulmonary disease (COPD).
- It can also be used to help wean patients from invasive ventilation.
- Extracorporeal membrane oxygenation (ECMO):
- This is a more recent technique being used in patients of all ages.
- It involves blood being artificially removed from the body and then oxygen being added by a machine whilst carbon dioxide is removed. The blood is then returned to the patient.
- One of the main uses of this method in adults at present is in severe heart failure where other treatments have failed.
- The underlying cause may also require treatment - for example, steroids and antibiotics.
- For some patients there may not be any further treatment options and their respiratory failure may be terminal. They may benefit from the palliative care team, which deals with managing patients with terminal illnesses.
What are the complications of respiratory failure?
As a result of respiratory failure various complications can occur, including:
- Lung complications: for example, a blood clot on the lung (pulmonary embolism), irreversible scarring of the lungs (pulmonary fibrosis), a collection of air between the lung and chest wall (pneumothorax) which can further compromise breathing, chronic respiratory failure and dependence on a ventilator.
- Heart complications: for example, heart failure, fluid around the heart (pericarditis) and acute heart attack.
- Increase in blood count (called polycythaemia): the increased level of red cells occurs from low blood oxygen levels but can lead to blood clots, due to sluggish flow in the blood vessels.
- Neurological complications: a prolonged period of low blood oxygen levels can deprive the brain of oxygen, which may be irreversible and may present as coma, fits (seizures) and even brain death.
- Prolonged hospital admissions can lead to the following complications:
- Hospital-acquired infections: for example, pneumonia and diarrhoea. A pneumonia is likely to put further strain on the respiratory function and can require a need for further ventilation.
- Malnutrition which may require assisted feeding methods, such as a tube being inserted down the nose into the stomach (nasogastric feeding), or providing nutrition through a needle straight into the bloodstream. Both of these methods have complications of their own.
- Complications from being bed bound for long periods: wasting of limbs with associated weakness, pressure sores, deep vein thrombosis and mental depression.
What is the outlook following respiratory failure?
How well a patient does depends on several factors, including age, the underlying cause and whether it is treatable, the speed of diagnosis and presence of any other illnesses and complications.
Can respiratory failure be prevented?
Smoking is a key factor in many cases of respiratory failure and stopping smoking and/or never smoking are important to prevent respiratory failure.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Gurvinder Rull
Prof Cathy Jackson