Collapse of part or all of a lung caused by obstruction of one or more air passages in the lung. Obstruction may be caused by accumulation of mucus, by an accidentally inhaled foreign body, by a tumour in the lung, or by enlarged lymph nodes exerting pressure on the airway.
The main symptom is shortness of breath. There may also be a cough and chest pain. The condition can be diagnosed by chest X-ray. Treatment is aimed at removing the cause of the blockage and may include physiotherapy or bronchoscopy. If the obstruction can be removed, the lung should reinflate normally.
Collapse of a part of the lung, or failure of the lung to expand at birth.
n. failure of part of the lung to expand. This occurs when the cells lining the air sacs (alveoli) are too immature, as in premature babies, and unable to produce the wetting agent (surfactant) with which the surface tension between the alveolar walls is overcome. It also occurs when the larger bronchial tubes are blocked from within by retained secretions, inhaled foreign bodies, or bronchial cancers, or from without by enlarged lymph nodes, such as are found in patients with tuberculosis and lung cancers. The lung can usually be helped to expand by physiotherapy and removal of the internal block (if present) via a *bronchoscope, but prolonged atelectasis becomes irreversible.
(bi-level positive airways pressure) trade name for a device that provides ventilation for patients by delivering air to the lungs at two levels of pressure, either cyclically in an anaesthetized patient or triggered by the patient’s attempts at breathing when awake. The higher pressure inflates the lungs to whatever volume can safely be achieved, while the lower pressure enables controlled exhalation against a resistance: this minimizes *atelectasis, a risk with conventional positive-pressure ventilators, which allow exhalation against zero resistance (by opening a valve in the device). Although BiPAP is a trade name, it is now widely used generically for this type of ventilation (or ventilator). There are also other devices that utilize the same principle, for example vPAP (variable positive airways pressure).... bipap
(CPAP) an air pressure in the range 5–30 cm H2O (1.2–7.5 mPa). It can be applied to the upper airways using a full face mask or a nasal mask only (nCPAP). It is used in high-dependency units to optimize oxygen delivery to patients who are being weaned from ventilators and on patients at home with *obstructive sleep apnoea. It works by improving nasopharyngeal airways, reducing the work of breathing, and preventing basal *atelectasis during sleep.... continuous positive airways pressure
n. a wetting agent. Surfactants can be added to materials used in dentistry to reduce surface tension and so improve flow. Pulmonary surfactant, secreted by type II *pneumocytes, is a complex mixture of compounds (including lipids, protein, and carbohydrates) that prevents the air sacs (alveoli) of the lungs from collapsing by reducing surface tension. In its absence, as in the immature lungs of premature babies, *atelectasis and *respiratory distress syndrome will develop.... surfactant
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