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 ( PaCO2: 7.0 kPa, SD 1.3). None of the clinical motives were related to the PaCO2 level. Average PaO2 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.