Development of chronic hypoventilation in amyotrophic lateral sclerosis patients.
Early prediction of respiratory muscle involvement and chronic hypoventilation (CH) in amyotrophic lateral sclerosis (ALS) patients can help to plan mechanical ventilatory aids and palliative care interventions well before respiratory failure occurs. To describe the natural history of the progressive pulmonary dysfunction leading to CH, and to identify potential parameters associated with its development in ALS, we prospectively followed 38 ALS patients up to 26 months, starting from their first presentation at our Clinic. At study entry, median FVC was 87% (interquartile range: 72-104%) and declined by 10% after 6 months (range: 2-49%), showing a very high inter-patient variability. Over the 26-months follow-up, 19 patients (50%) presented CH in the first 12 months, and eight patients (21%) developed CH in the remaining 14 months of the study. The remaining 29% of patients did not show signs of CH during the whole period of observation. In the Cox model, the category of disease progression (rapid vs. intermediate and slow), assessed using the Appel ALS Rating Scale (AARS) in the first 3 months after presentation, was the only variable associated with a significantly increased likelihood of CH. We conclude that CH can occur within 1 year from presentation in a great proportion of patients, independently from their initial respiratory status. Including the patients in specific categories of early disease progression, as assessed with the AARS, could be a sensitive method to identify patients with different risk of developing CH, and may help physicians to more efficiently plan the frequencies of respiratory evaluations, initiate mechanical ventilation and discuss advance directives with the patients and their caregivers.