Respiratory failure is nearly any condition that affects breathing and ultimately results in failure of the lungs to function properly. The main tasks ofthe lungs and chest are to get oxygen into the bloodstream from air that is inhaled (breathed in) and, at the same to time, to eliminate carbon dioxide (C02) from the bloodstream through air that is exhaled (breathed out). In respiratory failure, either the level of oxygen in the blood becomes dangerously low, and/or the level of C02 becomes dangerously high.
Respiratory failure often is divided into two main types. One type is hypoxemic respiratory failure. This occurs when something interferes with normal gasexchange and too little oxygen gets into the blood (hypoxemia). All organs and tissues in the body suffer as a result. Respiratory distress syndrome, high altitudes (where there is less oxygen in the air), various forms of lung disease, severe anemia, and blood vessel disorders, can all prevent the lungs from extracting sufficient oxygen from the air.
The other type of respiratory failure is ventilatory failure. This occurs when breathing is not strong enough to rid the body of C02, which then builds up in the blood. This can happen when the respiratory center in thebrainstem fails to drive breathing, when muscle disease keeps the chest wallfrom expanding when breathing in, or when chronic obstructive lung disease ispresent, making it difficult to exhale. Many respiratory conditions cause both too little oxygen (hypoxemia) and too much C02 (ventilatory failure).
The major categories of respiratory failure, with specific examples of each,are:
- Obstruction of the airways. Examples are chronic bronchitis withheavy secretions; emphysema; cystic fibrosis; asthma (a condition in which itis very hard to get air in and out through narrowed breathing tubes).
- Weak breathing. This can be caused by drugs or alcohol, which depress therespiratory center; extreme obesity; or sleep apnea, where patients frequently stop breathing during sleep.
- Muscle weakness. This can be caused by muscular dystrophy; polio; a stroke that paralyzes the respiratory muscles;injury of the spinal cord; or Lou Gehrig's disease.
- Lung diseases.These include severe pneumonia; pulmonary edema (fluid in the lungs); heart disease; respiratory distress syndrome; pulmonary fibrosis and other scarringdiseases of the lung; radiation exposure; smoke inhalation; and widespread lung cancer.
- An abnormal chest wall. This condition can be caused by scoliosis or severe injury to the chest wall.
Both low blood oxygen and high blood C02 can impair mental functions. Patients may become confused and disoriented and find it impossible to carry out their normal activities or do their work. Marked C02 excess can cause headaches and, in time, a semi-conscious state, or even coma. Lowblood oxygen causes the skin to take on a bluish tinge. It also can cause anabnormal heart rhythm (arrhythmia). Lung disease may cause abnormal chest sounds upon examination with a stethoscope such as wheezing in asthma, and "crackles" in obstructive lung disease. Patients often breathe rapidly, are restless, and have a rapid pulse. A patient with ventilatory failure is prone to gasp for breath, and may use the neck muscles to help expand the chest.
The primary symptom of respiratory failure is shortness of breath. Other signs and symptoms are not specific but depend upon what is causing the failure.Good general health and some degree of "reserve" lung function will help a patient through an episode of respiratory failure. The key diagnostic method isto measure the amounts of oxygen, C02, and acid in the blood at regular intervals.
In treating respiratory failure, most patients are first given oxygen, then the underlying cause of respiratory failure must be treated. For example, antibiotics are used to fight a lung infection, or, for an asthmatic patient, a drug to open up the airways is commonly prescribed. A patient whose breathingremains very poor will require a mechanical ventilator to aid breathing. A plastic tube is placed through the nose or mouth into the windpipe and attachedto a machine that forces air into the lungs. This can be a lifesaving treatment and should be continued until the patient's own lungs can take over the work of breathing. It is very important to use no more pressure than is necessary to provide sufficient oxygen, otherwise ventilation may cause further lung damage. Drugs are given to keep the patient calm, and the amount of fluid in the body is carefully adjusted so that the heart and lungs can function asnormally as possible. Steroids, which combat inflammation, may sometimes be helpful but they can cause complications, including weakening the breathing muscles.
The respiratory therapist has a number of methods available to help patientsovercome respiratory failure. They include:
- Suctioning the lungs through a small plastic tube passed through the nose, in order to remove secretions from the airways that the patient cannot cough up.
- Postural drainage, in which the patient is propped up at an angle or tilted to help secretions drain out of the lungs. The therapist may clap the patient on the chest orback to loosen the secretions, or a vibrator may be used for the same purpose.
- Breathing exercises after the patient recovers sufficiently to help strengthen the muscles that aid breathing.
The prognosis (outlook) for patients with respiratory failure depends chieflyon its cause. When respiratory failure develops slowly, pressure may build up in the lung's blood vessels, a condition called pulmonary hypertension. This condition may damage blood vessels and cause the heart to fail. If it is not possible to provide enough oxygen to the body, complications involving either the brain or the heart may also prove fatal. If the kidneys fail or the diseased lungs become infected, the prognosis is poor. In some cases, the primary disease causing respiratory failure is irreversible. Then, the patient, family, and physician together must decide whether to prolong life by ventilator support. Occasionally, lung transplantation is an option; however, this itis a highly complex procedure and availability of healthy lungs is small. Ifthe underlying disease can be effectively treated, however, the outlook is usually good. Care is needed not to expose the patient to polluting substancesin the atmosphere as it could tip the balance against recovery.
The best prevention of respiratory failure is early treatment of any lung disease or respiratory disease. Once serious respiratory failure is present, treatment in an intensive care unit with specialized personnel and equipment isdesirable.