In an ALS patient with FVC 60–70% predicted, normal daytime ABG, and normal nocturnal oximetry, but persistent orthopnea and unrefreshing sleep, do you initiate nocturnal NIV — and if so, how do you navigate the CMS coverage gap?

Guidelines disagree on when to start NIV in ALS, and CMS coverage lags behind all of them. CHEST 2023 supports initiation at FVC <80% with symptoms (or <50% without), SNIP/MIP <−40 cmH₂O, or hypercapnia. NICE NG42 similarly triggers on FVC <80% plus symptoms (particularly orthopnea), or SNIP/MIP <40 cmH₂O alone, or sex-stratified SNIP/MIP <65 cmH₂O (men) / <55 cmH₂O (women) plus symptoms. CMAJ 2020 goes further — upright FVC <65% qualifies even without symptoms, and orthopnea alone is sufficient. The EAN 2024 guideline dropped numerical thresholds entirely in favor of a symptom-forward framework. The retired AAN 2009 parameter historically allowed orthopnea alone. In contrast, CMS LCD L33800 covers NIV in progressive NMD only when one of the following is met: PaCO₂ ≥45 mmHg awake, nocturnal SpO₂ ≤88% for ≥5 continuous minutes, FVC <50% predicted, or MIP <60 cm H₂O — meaning a symptomatic FVC 60–70% patient meets every major society guideline but not the payer rule.