What postural change in FVC is suggestive of respiratory muscle weakness?  

In our practice, an assisted ventilation clinic which is enriched with patients who have diagnosed neuromuscular disease and/or chronic respiratory failure of unclear etiology, we often use 12% or 200cc simply by analogy to the criteria we use to assess bronchodilator responsiveness during PFTs. Al...

We use a supine drop of 15% for "significance." A symptomatic ALS population Postural change of FVC predicts some respiratory symptoms in ALS had roughly this percentage change. 15% cutoff is seen in ERS statement as well 2019 ERS.I agree, clinical signals may be sooner and certainly vary by patholo...