Respiratory phenotypes in amyotrophic lateral sclerosis as determined by respiratory questions on the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised and their relation to respiratory tests.

These three distinct ALS phenotypic respiratory categories represent progressive stages of ventilatory dysfunction, supporting ALSFRS-R clinical relevance. Orthopnoea is a severe symptom that should prompt NIV, phrenic nerve response being an independent predictor. Early NIV promotes similar survival for G2 and G3.