[Clinical scale of ventilatory failure risk in patients with amyotrophic lateral sclerosis]

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that causes atrophy and paralysis of skeletal muscles, including respiratory muscles. The development of ventilatory failure determines the prognosis. The primary outcome was to determine which common clinical variables can be predictors of daytime hypercapnia and develop a risk model of ventilatory failure. Secondary outcome was to determinate the survival rate of high-risk patients with and without hypercapnia.

Retrospective study. Patients with ALS without mechanical ventilation were selected and followed from June 2015 to May 2024. They underwent arterial blood carbon dioxide measurement and classified into two groups: hypercapnic (pCO2 ≥45 mmHg) and normocapnic (pCO2 <45 mmHg). Different predictive models for hypercapnia were constructed.

An association between orthopnea (p=0.0001), dyspnea (p=0.02) and FVC <50% (p=0.04) was found. The predictive model constructed with the following variables: orthopnea, dyspnea and ALSFRS-R score ≤21, presented a good performance on the detection hypercapnia risk. A score > 23 points had a sensitivity of 80.6% and a specificity of 72.8% for detecting patients at high risk of hypercapnia. Normocapnic patients at high risk who start mechanical ventilation before developing hypercapnia improve their survival rate by 6 months (p=0.17).

The risk score includes easily obtained clinical variables and is effective in detecting patients at risk for hypercapnia. Initiating mechanical ventilation in at-risk patients who have not yet developed hypercapnia has a clinically significant impact on survival.