Definition of Respiratory failure

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Respiratory failure: Inability of the lungs to perform their basic task of gas exchange, the transfer of oxygen from inhaled air into the blood and the transfer of carbon dioxide from the blood into exhaled air. The basis of respiratory failure may be failure of the exchange of oxygen and carbon dioxide within the tiny air sacs (alveoli) in the lungs; failure of the muscles required to expand the lungs; or failure of the brain centers controlling respiration.

A host of medical conditions can lead to respiratory failure, including:

• A long history of asthma
• A long history of emphysema
• A long history of chronic obstructive lung disease
• Major surgery on the abdomen, heart, or lungs
• An overdose of sleeping pills or certain depressant drugs
• A premature baby who weighs less than 3 pounds
• A baby with bronchopulmonary dysplasia
• Multiple physical injuries, as in an auto accident
• Extensive burns
• Profuse bleeding, as from a gunshot wound
• Near drowning
• Advanced heart failure
• Severe infection, such as AIDS
• Extremely obesity

The ventilatory apparatus: The exchange of these gases occurs in tiny air sacs in the lung, the alveoli. When a person breathes in, air is brought into the alveoli by the action of the respiratory muscles -- the diaphragm, the muscles between the ribs, and the accessory muscles (those between the neck and the chest wall). These are collectively called "the ventilatory apparatus."

The respiratory centers: The activity of the respiratory muscles is controlled by respiratory centers in the brain. The brain's respiratory centers in turn are controlled by chemoreceptors, special cells that are sensitive to the amounts of carbon dioxide or oxygen in the blood. The chemoreceptors that are sensitive to oxygen concentration are located in the large arteries in the neck in the carotid bodies. When they sense a fall in the level of oxygen in the blood, they send messages that stimulate the respiratory center in the brain so that there will be an increase in the rate or depth of breathing.

Failure of the ventilatory apparatus or respiratory centers: Whenever any part of the ventilatory apparatus and/or the respiratory centers fails to work properly, the result can be respiratory failure. Both adults and babies can develop respiratory failure. In infants, however, respiratory failure occurs mostly in premature babies whose lungs have not yet fully developed.