Initial investigations for a patient suspected of having atelectasis should include a chest radiograph (chest X-ray) to identify areas of lung collapse or other abnormalities. This is the primary imaging modality to confirm atelectasis and exclude other pathologies.
Additional investigations may include spirometry to assess lung function and exclude other chronic airway diseases.
A full blood count should be performed to identify any anaemia or polycythaemia that might affect oxygen delivery.
Pulse oximetry is useful to assess oxygen saturation, especially if there are clinical features of respiratory compromise.
Further imaging such as a CT scan of the thorax may be considered if the chest X-ray findings are inconclusive or if there is suspicion of other lung pathology.
ECG and serum natriuretic peptides may be warranted if cardiac disease or pulmonary hypertension is suspected clinically.