Upper airway calibre and impedance in patients with Steinert's myotonic dystrophy.

Myotonic dystrophy (MD) can be responsible for increased inspiratory muscle loading, the origin of which is debated, with some authors incriminating distal lesions and others central abnormalities. Using a recent non-invasive method based on single transient pressure-wave reflection analysis, we measured central airway calibre from the mouth to the carina and respiratory impedance in a group of adults with MD, a group of patients with sleep apnoea syndrome (SAS) but no neuromuscular disease, and a group of normal controls. All participants were awake during the measurements. We found no reduction in central airway calibre in the patients with the adult form of MD, as compared to the normal controls. These data suggest that MD may be associated with peripheral airway obstruction related to alterations in the elastic properties of the lung.