Respiratory phenotypes in ALS as determined by respiratory questions of the ALSFRS-R and their relation to respiratory tests.

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