A blood tension of carbon dioxide below normal. It is produced by HYPERVENTILATION which may be voluntary, mechanical (if the patient is on a ventilator) or in response to a physiological insult such as metabolic acidosis or brain injury.
In?ammation of the alveoli (see ALVEOLUS) of the lungs caused by an allergic reaction. When the in?ammation is caused by infection it is called PNEUMONIA, and when by a chemical or physical agent it is called pneumonitis. It may be associated with systemic sclerosis or RHEUMATOID ARTHRITIS.
Extrinsic allergic alveolitis is the condition induced by the lungs becoming allergic (see ALLERGY) to various factors or substances. It includes BAGASSOSIS, FARMER’S LUNG and BUDGERIGAR-FANCIER’S LUNG, and is characterised by the onset of shortness of breath, tightness of the chest, cough and fever. The onset may be sudden or gradual. Treatment consists of removal of the affected individual from the o?ending material to which he or she has become allergic. CORTICOSTEROIDS give temporary relief.
Fibrosing alveolitis In this disease there is di?use FIBROSIS of the walls of the alveoli of the lungs. This causes loss of lung volume with both forced expiratory volume and vital capacity affected, but the ratio between them remaining normal. The patient complains of cough and progressive DYSPNOEA. Typically the patient will be cyanosed (blue – see CYANOSIS), clubbed (see CLUBBING), and have crackles in the mid- and lower-lung ?elds. Blood gases will reveal HYPOXIA and, in early disease, hypocapnia (de?ciency of carbon dioxide in the blood due to hyperventilation). There is an association with RHEUMATOID ARTHRITIS (about one-eighth of cases), systemic lupus erythematosus (see under LUPUS), and systemic SCLEROSIS. Certain drugs – for example, bleomycin, busulphan and hexamethonium – may also cause this condition, as may high concentrations of oxygen, and inhalation of CADMIUM fumes.... alveolitis
An abnormally rapid resting respiratory rate (see RESPIRATION). If voluntarily induced, it causes lightheadedness and then unconsciousness by lowering the blood tension of carbon dioxide.
Hyperventilation is a manifestation of chest and heart diseases which raise carbon dioxide tension or cause HYPOXIA (e.g. severe CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) or PULMONARY OEDEMA). Mechanically ventilated patients may be hyperventilated to lower carbon dioxide tension in order to reduce INTRACRANIAL PRESSURE. (See also HYPOCAPNIA.)... hyperventilation
(hypocapnia) n. a condition in which there is an abnormally low concentration of carbon dioxide in the blood. This may be caused by breathing that is exceptionally deep in relation to the physical activity of the individual.... acapnia
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