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Respiratory failure (lung failure) is a condition in which the level of oxygen in the blood becomes dangerously low or the level of carbon dioxide becomes dangerously high.

• Conditions that block the airways, damage lung tissue, weaken the muscles that control breathing, or decrease the drive to breathe may cause lung failure.
• People may be very short of breath, have a bluish coloration to the skin, and be confused or sleepy.
• Doctors use blood tests to detect low levels of oxygen or high levels of carbon dioxide in the blood.
• Oxygen is given.
• Sometimes people need the help of a machine to breathe until the underlying problem can be treated.

Respiratory failure is a medical emergency that can result from long-standing, progressively worsening lung disease or from severe lung disease that develops suddenly, such as the acute respiratory distress syndrome (see Respiratory Failure and Acute Respiratory Distress Syndrome: Acute Respiratory Distress Syndrome (ARDS)), in otherwise healthy people.

Causes

Almost any condition that affects breathing or the lungs can lead to respiratory failure. Certain disorders, such as hypothyroidism or sleep apnea, can decrease the unconscious reflex that drives people to breathe. An overdose of opioids or alcohol also can decrease the drive to breathe by causing profound sedation. Obstruction of the airways, injury to the lung tissues, damage to the bones and tissues around the lungs, and weakness of the muscles that normally inflate the lungs are also common causes. Respiratory failure can occur if blood flow through the lungs becomes abnormal, as happens in pulmonary embolism (see Pulmonary Embolism (PE): Pulmonary Embolism). This disorder does not stop air from moving in and out of the lungs, but without blood flow to a portion of the lungs, oxygen is not properly extracted from the air.

Did You Know? Age-related reductions in lung function place older people at higher risk of severe symptoms after developing pneumonia.

Symptoms

Low oxygen levels in the blood can cause shortness of breath and result in a bluish coloration to the skin (cyanosis). Low oxygen levels, high carbon dioxide levels, and increasing acidity of the blood cause confusion and sleepiness. If the drive to breathe is normal, the body tries to rid itself of carbon dioxide by deep, rapid breathing. If the lungs cannot function normally, however, this breathing pattern may not help. Eventually, the brain and heart malfunction, resulting in drowsiness (sometimes to the point of becoming unconscious) and abnormal heart rhythms (arrhythmias), both of which can lead to death.

Some symptoms of respiratory failure vary with the cause. A child with an obstructed airway due to the inhalation (aspiration) of a foreign object (such as a coin or a toy) may suddenly gasp and struggle for breath (see First Aid: Choking). People with acute respiratory distress syndrome may become severely short of breath over a period of hours. Someone who is intoxicated or weak may quietly slip into a coma.

Diagnosis

A doctor may suspect respiratory failure because of the symptoms and physical examination findings. A blood test done on a sample taken from an artery confirms the diagnosis when it shows a dangerously low level of oxygen or a dangerously high level of carbon dioxide. Chest x-rays and other tests are done to determine the cause of respiratory failure.

What Causes Respiratory Failure? Underlying Problem Cause Airway obstruction Chronic obstructive pulmonary disease, asthma, bronchiectasis, cystic fibrosis, bronchiolitis, inhaled foreign bodies Poor breathing (decrease in the drive to breathe) Obesity, sleep apnea, hypothyroidism, drug or alcohol intoxication Muscle weakness Myasthenia gravis, muscular dystrophy, polio, Guillain-Barré syndrome, polymyositis, certain strokes, amyotrophic lateral sclerosis (ALS), spinal cord injury Abnormality of lung tissue Acute respiratory distress syndrome (ARDS), pneumonia, pulmonary edema (excess fluid in the lungs) from heart or kidney failure, drug reaction, pulmonary fibrosis, widespread tumors, radiation, sarcoidosis, burns Abnormality of chest wall Scoliosis, chest wound, extreme obesity, deformities resulting from chest surgery

Treatment

People with respiratory failure are treated in an intensive care unit. Oxygen is given initially, usually in a greater amount than is needed, but the amount of oxygen can be adjusted at a later time. Occasionally, in people in whom carbon dioxide levels have remained high for some time, excess oxygen can result in slowing of the movement of air (ventilation) in and out of the lungs and a dangerous further increase in the carbon dioxide level. In such people, the dosage of oxygen needs to be more carefully regulated.

The underlying disorder causing the respiratory failure must also be treated. For example, antibiotics are used to fight bacterial infection, and bronchodilators are used in people with asthma to open the airways. Other drugs may be given, for example, to decrease inflammation or treat blood clots. Mechanical ventilation is necessary unless respiratory failure resolves rapidly.

Last full review/revision January 2008 by Brian K. Gehlbach, MD; Jesse B. Hall, MD