Lung function and disability in neuromuscular patients at first admission to a respiratory clinic

Background: Respiratory failure is the most common cause of morbidity and mortality in patients with neuromuscular diseases (NMD). Non-invasive mechanical ventilation is considered highly effective for treating chronic respiratory failure. Perception and knowledge of risks associated with respiratory derangements may be underestimated.

Objective: The aim of our study was to evaluate the association among respiratory function, general clinical disability and need of home mechanical ventilation (HMV) in patients with slowly progressive NMD admitted for the first time to dedicated respiratory outpatient clinics.

Methods: Anthropometrics, lung function, respiratory muscle function, daytime blood gases data, and general clinical disability assessed by means of a clinical interview were recorded. Indication for HMV was an arterial CO(2) tension >45mmHg and/or a vital capacity <50% predicted, and/or maximal inspiratory pressure <60cmH(2)O.

Results: Two out of 5 patients complained of dyspnoea during daily activity and dysphagia, while more than 1/3 had ineffective cough and speech difficulties. Two-third of the whole group were considered to need HMV. By applying one or more criteria for NMD diagnosis, great variability was found for indication to HMV. Clinical disability was inversely related to dynamic and static lung volumes, and to respiratory muscle function.

Conclusions: About two-third of NMD patients admitted to a respiratory clinic is a candidate for home mechanical ventilation being their clinical derangement inversely related with respiratory function. The use of a simple dedicated clinical disability interview may reduce underestimation of HMV need.