Respiratory Failure: Classification, Causes, Symptoms, Diagnosis, Treatment, Complications, Outlook and Prevention

It occurs when the respiratory system does not maintain adequate levels of oxygen in the blood.

There may also be difficulties in eliminating waste gases, mainly carbon dioxide in the blood.

Respiratory failure is the result of inadequate gas exchange by the respiratory system, which means that arterial oxygen, carbon dioxide, or both cannot be maintained at normal levels.

A drop in oxygen carried in the blood is known as hypoxemia ; an increase in arterial carbon dioxide levels is called hypercapnia . Respiratory failure is classified as Type I or Type II, depending on whether there is a high level of carbon dioxide.

The definition of respiratory failure in clinical trials generally includes an increased respiratory rate, abnormal blood gases (hypoxemia, hypercapnia, or both), and evidence of increased work of breathing.

The normal partial pressure reference values ​​are: oxygen PaO2 more than 80 mmHg (11 kPa) and carbon dioxide PaCO2 less than 45 mmHg (6.0 kPa).

Respiratory failure occurs when not enough oxygen passes from the lungs to the blood. It also depends on the underlying cause. You may receive oxygen therapy and other treatment to help you breathe.

Classification of respiratory failure

Respiratory failure is mechanically classified based on the pathophysiological disorder in respiratory failure. This classifies respiratory failure into 4 types:

Type I respiratory failure (hypoxemia) : This is due to an intrinsic lung disease that interferes with the transfer of oxygen in the lungs. The oxygen in the blood is low and the carbon dioxide is normal or low.

Hypoxemia resulting from ventilation / perfusion mismatch or diffusion abnormality can be easily corrected with supplemental oxygen. This is in contrast to hypoxemia induced purely by increased shunt, it is refractory to supplemental oxygen.

The resulting hypoxemia stems from a higher shunt fraction, ventilation / perfusion (V / P) mismatch, or a combination of both.

Four pathophysiological mechanisms explain hypoxemia in a variety of diseases and this includes: ventilation / perfusion (V / P) mismatch, increased shunting, impaired diffusion, and alveolar hypoventilation.

It is characterized by an arterial oxygen tension (PaO2) <60mmHg (in room air) with a normal or low arterial carbon dioxide tension (PaCO2).

It is the most common form of respiratory failure and can be associated with most acute diseases of the lungs that involve fluid filling or collapse of the alveolar units.

Ventilation / perfusion mismatch (low ventilation / perfusion), which is the most common mechanism that develops when there are lung regions with a greater reduction in ventilation than in perfusion.

In bypass, there is a bypass of the ventilated alveoli by intrapulmonary or intracardiac deoxygenated mixed venous blood resulting in venous mixing.

The pathway for oxygen diffusion from the alveolar space to the pulmonary capillaries can be increased by diseases that in turn decrease the capillary surface area and prevent the complete balance of alveolar oxygen with the pulmonary capillary blood.

In underlying lung disease, there is a widening of the alveolar / arterial gradient, either from ventilation / perfusion mismatch or bypass or impairment.

Severe hypoxemia, whereas for hypoxemia accompanying hypoventilation (without underlying lung disease) the alveolar / arterial gradient is normal.

Common causes include : acute respiratory distress syndrome, chronic obstructive pulmonary disease, pneumonia , pulmonary edema, pulmonary fibrosis, asthma , pneumothorax, pulmonary embolism , pulmonary hypertension.

Type II respiratory failure (hypercapnic) : characterized by alveolar hypoventilation and increased pressure of carbon dioxide (PaCO2). It is caused by loss of central nervous system drive, impaired neuromuscular capacity, excessive dead space, or increased mechanical load.

The arterial carbon dioxide pressure PaCO2 is> 50mmHg. Commonly caused by myasthenia gravis, head injury, polyneuropathies, muscular dystrophy, kyphoscoliosis, unstable chest, obesity hypoventilation syndrome, advanced chronic bronchitis, and emphysema.

Oxygen in the blood is low and carbon dioxide is high. The pump failure leading to hypercapnia is caused by three main factors including: inadequate production of the respiratory centers that control the muscles, mechanical defect in the chest wall, excessive inspiratory load.

Inadequate output of the respiratory centers that control the muscles results in insufficient respiratory drive for the demand or respiratory centers, my reflex modifies its production to avoid respiratory muscle injury and avoid fatigue.

Insufficient activation of the central nervous system, either temporarily (from anesthesia, drug overdose or permanently) diseases of the spinal cord, produces inadequate respiratory effort and hypoventilation occurs.

Mechanical defects in the chest wall such as unstable chest, diseases of the nerves (Guillain-Barré syndrome) and anterior horn cells (poliomyelitis) or diseases of the respiratory muscles (myopathies).

Excessive inspiratory load fatigue the inspiratory muscles that are unable to generate adequate pleural pressure despite adequate respiratory drive and intact chest wall.

Factors that increase inspiratory muscle energy demand and / or decrease energy supplies predispose respiratory muscles to fatigue.

Respiratory failure can also be described according to the time it takes to develop:

Type III respiratory failure : typically occurs in the perioperative period when factors that reduce functional residual capacity (FRC) combine with causes of increased closure volume to produce atelectasis.

Commonly caused by inadequate postoperative analgesia, obesity, ascites, and excessive secretions from the airways.

Type IV respiratory failure : results of hypoperfusion of respiratory muscles in patients in shock. Patients are generally intubated and ventilated in the shock resuscitation process. Commonly caused by cardiogenic shock, septic shock, and hypovolemic shock.

Respiratory failure can be further classified as acute, develops in minutes or hours with pH <7.3 or chronic, develops over several days or more, allowing time for renal compensation and increasing bicarbonate concentration. The pH generally decreases slightly.

Arterial blood gases are not sufficient to clearly distinguish between acute and chronic respiratory failure. Abrupt changes in mental status suggest acute respiratory failure while clinical markers of chronic hypoxemia such as polycythemia or cor pulmonale.

Acute : occurs in minutes or hours; generally, the patient does not have an underlying lung disease.

Chronic – occurs over days and there is usually an underlying lung disease.

Acute over chronic : This is usually a sudden or rapid worsening of respiratory function in someone who already has chronic respiratory failure.

What are the causes of respiratory failure?

Every time we breathe, we are carrying oxygen from the air to the lungs. This passes into the blood and is then transported to the various organs. At the same time, carbon dioxide, which is the waste gas produced by the organs, passes from the blood to the lungs, and then we exhale.

This whole process requires an interaction of several systems, such as the lungs, the heart, the chest muscles and the brain. When any of these deteriorate, we run the risk of respiratory failure.

Respiratory failure is defined by low levels of oxygen in the blood and there may also be elevated levels of carbon dioxide in the blood.

There are several causes of respiratory failure, the most common being due to the lungs or the heart. Pulmonary disorders that lead to respiratory failure include chronic obstructive pulmonary disease, asthma, and pneumonia.

Heart diseases that can lead to respiratory failure can be heart failure, which may or may not be accompanied by a heart attack.

Common causes of type I respiratory failure

  • Chronic obstructive pulmonary disease (COPD).
  • Pneumonia.
  • Pulmonary edema.
  • Pulmonary fibrosis.
  • Asthma.
  • Pneumothorax.
  • Pulmonary embolism
  • Pulmonary hypertension.
  • Cyanotic congenital heart disease.
  • Bronchiectasis
  • Syndrome acute respiratory distress .
  • Respiratory diseases associated with HIV infection.
  • Cifoescoliosis.
  • Obesity .

Common causes of type II respiratory failure

  • Chronic obstructive pulmonary disease (COPD).
  • Severe asthma
  • Drug overdose, poisoning.
  • Miastenia serious.
  • Polyneuropathy
  • Poliomyelitis.
  • Muscle disorders.
  • Head injuries and neck injuries.
  • Obesity.
  • Pulmonary edema.
  • The acute respiratory distress syndrome.
  • Hypothyroidism .

What are the symptoms?

Respiratory failure may occur slowly and patients adjust, such as slowing down and avoiding physical tasks. This is less common and patients may complain of the following symptoms:

Shortness of breath – at first, this can happen only from effort; However, later on it can also occur at rest and when trying to sleep.

Tiredness : this is due to the lack of oxygen reaching the body’s organs.

A bluish tinge to the hands or lips – the medical term for this is “cyanosis.” It is noticeable when you are at rest and can be worse with exertion.

Confusion and reduced consciousness : This can occur when the oxygen levels in the blood are low or when the level of carbon dioxide increases.

There may also be features of the underlying cause, eg, chest pain in heart disease, limb weakness in neurological disorders, wheezing in asthma.

When your healthcare professional conducts an evaluation, they may find the following:

High rate of respiration (respiratory). A bluish tinge to the lips and fingers (cyanosis). Restlessness, anxiety, confusion, fits (convulsions), or coma can occur due to abnormalities in blood gases.

When listening to the lungs, there may be sounds suggestive of infection, fluid overload, or asthma, depending on the underlying cause.

There may also be features of right-sided heart failure that can occur due to stress on the heart. This is called ‘cor pulmonale’ and there will be fluid retention evidenced by an enlarged liver, swelling of the belly (abdomen), and swelling of the legs.

Mechanism of injury / disease process

In general, lung failure caused by a variety of lung disease leads to gas exchange failure manifested by hypoxemia, while pump failure results in ventilatory failure manifesting as hypercapnia.

Lung diseases can lead to muscle fatigue and ventilatory failure due to an imbalance between demands and supplies.

Similarly, patients with conditions involving the ventilatory pump and hypercapnia are characterized by the inability to cough and possibly atelectasis. This exacerbates the ventilation / perfusion mismatch resulting in hypoxemia.

How is the diagnosis of respiratory failure made?

The diagnosis of respiratory failure requires an arterial blood gas that provides information on blood oxygen levels and carbon dioxide levels.

An arterial blood gas simply involves a needle attached to a syringe, which is then inserted into the wrist directly at the point where the pulse can be felt.

Sometimes the pulse in the wrist weakens and therefore a different site must be used – usually the groin and less often the elbow.

Find the underlying cause

Once the diagnosis has been made, further investigations will be required to find the underlying cause. This can include:

Chest X-ray : This may show infection, fluid, or lung tumors.

Blood tests : These may include complete blood count, kidney tests, and liver function tests.

They can help determine the cause and also detect any factors that may make respiratory failure worse, such as a low level of hemoglobin in the blood (anemia).

Troponin blood tests : These are used to determine if there has been a recent heart injury, for example a heart attack that may have caused respiratory failure.

Thyroid function tests : an underactive thyroid gland, when a long-term (chronic) condition can cause respiratory failure with an elevated level of carbon dioxide.

Spirometry : used to measure lung volumes and capacity and is useful in the evaluation of chronic cases.

A heart ultrasound (echocardiogram) : can look for heart causes, such as a leaking heart valve or heart failure.

Which is the treatment?

Patients with sudden onset (acute) respiratory failure or a new diagnosis of chronic respiratory failure should be admitted to the hospital immediately.

They need to be resuscitated and may need admission to an intensive care unit or the high dependency unit (depending on how ill the patient is) 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 diseases are present, and the social circumstances of the patient. Some patients may need home ventilators and oxygen support.

Treatment will aim to improve oxygen levels in the blood and remove residual carbon dioxide gas if it rises.

This will usually require artificial ventilation. Additional treatment will be directed at the underlying cause, such as antibiotics in pneumonia or diuretics in heart failure.

Treatment will be aimed at correcting blood oxygen and carbon dioxide levels and treating the underlying cause.

Treatment of respiratory failure

It may include:


High levels will be administered through a mask (although lower levels may be necessary in patients with chronic respiratory failure who have adapted to high levels of carbon dioxide).

Artificial ventilation or mechanical ventilation

This involves putting the patient in a coma, using medications and paralyzing their breathing. A tube is inserted into the windpipe and an artificial respirator then performs the work of breathing.

Once the underlying cause is treated, patients will be ‘disconnected’ from the ventilator so that their lungs begin to do the work of breathing. This is an “invasive” form of ventilation.

Non-invasive ventilation (NIV)

This is an alternative to invasive ventilation and is increasingly used, especially in cases where removal of an artificial ventilator can be difficult. It is used when there is a low level of oxygen in the blood and a high level of carbon dioxide in the blood, that is, type II respiratory failure.

The main disease in which it is used is chronic obstructive pulmonary disease. It can also be used to help patients detoxify from invasive ventilation.

Oxygenation by extracorporeal membrane

This is a newer technique used in patients of all ages. It involves the blood being artificially removed from the body and then oxygen is added to a machine while the carbon dioxide is removed. The blood is then returned to the patient.

One of the main uses of this method in adults today is 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 be no further treatment options and their respiratory failure may be terminal. They can benefit from the palliative care team, which deals with the management of terminally ill patients.

What are the complications of respiratory failure?

As a result of respiratory failure, several complications can occur, including:

Pulmonary complications : for example, a blood clot in the lung (pulmonary embolism), irreversible scarring of the lungs (pulmonary fibrosis), a build-up of air between the lung and the chest wall (pneumothorax) that can further compromise breathing, insufficiency chronic respiratory disease 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 polycythemia) : The increase in the level of red blood cells occurs from low oxygen levels in the blood, but can lead to blood clots due to slow flow in the blood vessels.

Neurological complications : A prolonged period of low oxygen levels in the blood can deprive the brain of oxygen, which can be irreversible and present as coma, seizures (seizures), and even brain death.

Long hospital admissions can lead to the following complications:

Infections acquired in the hospital : for example, pneumonia and diarrhea. Pneumonia is likely to put more pressure on respiratory function and require more ventilation.

Malnutrition that may require assisted feeding methods, such as a tube that is inserted through the nose into the stomach (nasogastric tube feeding) or provides nutrition through a needle directly into the bloodstream. Both methods have complications of their own.

Complications from lying down for long periods : limb wasting with associated weakness, pressure ulcers, deep vein thrombosis, and mental depression .

What is the perspective?

How well a patient does depends on several factors, including age, the underlying cause and whether it is treatable, the speed of diagnosis, and the presence of other diseases and complications.

Some patients may get worse despite treatment and may not survive. If someone can no longer be treated to cure them, but still needs symptom control, they can be referred to the hospice team at the hospital or to the Macmillan nurses in the community.

Can respiratory failure be prevented?

Smoking is a key factor in many cases of respiratory failure and quitting and / or not smoking is important to prevent respiratory failure.