Radionuclide Imaging of the Lungs

Abstract

Disorders of the respiratory tract are very common in the intensive therapy unit (ITU) probably affecting the majority of patients. Even if such patients do not originally present with lung disease, immobility, severe illness with infection, prolonged assisted ventilation and embolism may result in life-threatening respiratory disorders. Sometimes the patient’s condition is clear-cut and may be allocated to a definite diagnostic category, specific or non-specific pneumonia, pulmonary embolism or chronic obstructive airways disease, but often the causes are multiple and difficult to define and the best that can be done is a statement of the physiological deficit to suggest what remedies are required. For instance hypoxia to some degree is almost universal after major surgery and has various causes (Cooper 1972). Apart from the depressant effect of anaesthesia and analgesia, abdominal pain may severely affect ventilation. Functional residual capacity is reduced and closing volume affected adversely. Spontaneous tidal breathing of such patients occurs from a lower total lung volume, with impaired expiration from early small airways closure, particularly at the lung bases. Against this picture it may be difficult to recognize focal pulmonary atelectasis, pneumonic consolidation and major bronchial obstruction. In some of the very ill, the cause of severe respiratory failure may be quite obscure. Some of these difficult cases may seem to merge into typical adult respiratory distress syndrome (ARDS) with obvious widespread lung damage.