respiratory failure
Meaning of respiratory failure: Respiratory failure names a measurement rather than a disease, so the same label covers a sedative overdose and end-stage lung disease alike.
Definition of respiratory failure
Respiratory failure is a state in which the lungs cannot keep the blood adequately supplied with oxygen, cannot clear enough carbon dioxide from it, or both. It is defined by measurements of the gases in arterial blood rather than by how hard the breathing looks. Causes range from diseased lung tissue to weak breathing muscles, and it can develop over minutes or over years.
What are the two types?
| Type | Blood gas pattern | Underlying fault |
|---|---|---|
| Type 1, hypoxemic | Oxygen low, carbon dioxide normal or low | Gas cannot cross into the blood from diseased lung tissue |
| Type 2, hypercapnic | Carbon dioxide high, oxygen usually low as well | Not enough air is being moved in and out overall |
The split is practical rather than academic, because the two arise from different faults and are supported in different ways. In the first, the lung is diseased while the bellows still work, as when air sacs fill with pus or fluid. In the second the bellows themselves fail: the drive to breathe is suppressed, the muscles are weak, the chest wall is stiff, or the airways are so obstructed that stale air cannot be cleared. Both leave tissue short of oxygen, a state named hypoxia.
What causes it?
Anything that damages the lungs or interrupts the machinery of breathing. Severe pneumonia, fluid flooding the lungs from a failing heart, a large clot in the lung arteries, a severe asthma attack and advanced chronic lung disease account for much of it. Away from the lung itself, opioid and sedative overdose blunts the drive to breathe, spinal injury and nerve or muscle disease weaken the effort, and severe obesity or a deformed chest wall loads it. Every part of the respiratory system can fail on its own, and in intensive care several commonly fail together.
How does it show?
Fast labored breathing, use of the neck and shoulder muscles, and an inability to finish a sentence are the visible signs. Low oxygen produces restlessness, confusion and a bluish tinge to the lips and fingertips. Rising carbon dioxide produces headache, flushing, drowsiness and eventually unconsciousness, a sequence that can look deceptively calm. The condition is time critical, because the brain and heart sustain damage within minutes once oxygen delivery fails. Failure arriving suddenly is dangerous at gas levels that a person with long-standing lung disease lives with, since the body adapts to slow change and not to abrupt change.
Also known as
Used in a sentence
Respiratory failure was documented on arterial blood gas analysis at admission.
Good to know
The diagnosis rests on measured blood gases rather than on appearance, and a person with long-standing lung disease may function at oxygen and carbon dioxide levels that would represent acute failure in someone whose lungs were previously normal.
Word origin
Where “respiratory failure” comes from
Respiration comes from the Latin respirare, to breathe again, built from re-, meaning again, and spirare, meaning to breathe.