Comment:

Pre‑bronchodilator spitrometry is normal with no significant response to acute bronchodilator therapy. Gas transfer is moderately reduced. Static lung volumes show a mildly elevated functional residual capacity and residual volume. In measuring the supine and sitting spirometry, there is a significant reduction in the FEV1 and FVC when supine. There was no significant response to inhaled hypertonic saline with a maximum fall in FEV 1 of 6% and response dose ratio of 0. 15. Overall, the results are suggestive of respiratory muscle weakness and formal measurement of inspiratory and expiratory muscle strength would confirm this The reduction in gas transfer is not fully explained by this however, and causes for this would include pulmonary vascular disease or early interstitial lung disease Clinical correlation is recommended.