Symptoms, clinical and physiological findings motivating home mechanical ventilation in patients with neuromuscular diseases.

OBJECTIVE: To clarify the relationship between symptoms, clinical signs and physiological abnormalities that were motivating the initiation of home mechanical ventilation in patients suffering from neuromuscular diseases.
METHODS: From The Swedish Home Mechanical Ventilation Register we identified 352 patients with neuromuscular diseases and we looked at circumstances (acute vs elective) and clinical motives for starting ventilatory support.
RESULTS: Home mechanical ventilation was commenced electively in 268 patients (76%) and among these daytime sleepiness was the most common motive, being reported in 56% of the patients. In the 24 children with spinal muscular atrophy, however, 96% started ventilation electively and cough insufficiency was the most common motive. The patients were moderately hypercapnic (PaCO(2): 7.0 kPa, SD 1.3). None of the clinical motives were related to the PaCO(2) level. Average PaO(2) was above 8 kPa in all groups, but lowest in the patients with post-polio and dystrophia myotonica. Mean vital capacity was close to 40% of predicted, but significantly lower in the Duchenne patients (26% of predicted).
CONCLUSION: Daytime sleepiness was the most common clinical symptom motivating home mechanical ventilation in this group of patients with chronic hypercapnic respiratory insufficiency secondary to neuro/myopathies. Respiratory function testing is therefore suggested to be included in the diagnostic work up of daytime sleepiness in these patients.