the site of obstruction can be measured accurately (Azizkhan et al 1985, Barker et al 1991).A reduction of tracheal diameter by 50% or more is usually associated with symptoms. Sometimes it may be helpful to examine dynamic airway function in addition. This can be seen directly, during fibreoptic bronchoscopy under local anaesthesia, or by constructing flow—volume loops. Reductions in maximum expiratory flows may warn of the possibility of obstruction after tracheal extubation.
3. Myocardial or pericardial involvement. Arrhythmias can occur, or the patient may have signs of a pericardial effusion. If cardiac tamponade is present, there is respiratory distress and pulsus paradoxicus.There may be cyanosis and syncope on straining (Keon 1981). Echocardiography should confirm the diagnosis.
4. Obstruction of the pulmonary artery. As a result of direct compression.
5. Spinal cord involvement. Can occur in posterior mediastinal tumours.
6. Recurrent laryngeal nerve problems. Predominantly occur with left-sided lesions.
7. Systemic nonmetastatic effects of tumours. These include hormone secretion, neuropathies, and myasthenia gravis.
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