RSB

Patients with respiratory muscle weakness exhibit an increased central motor output and rapid shallow breathing (RSB). As weakness progresses, the bellows action of the chest decreases and tidal volume (Vt) decreases further. This results in a decreased peripheral afferent input to supraspinal centers, likely to amplify the perception of breathlessness throughout the mismatching mechanism. We speculate that this mechanism is involved in the perception of dyspnea in patients with NMD.
Materials and Methods
Patients
Eleven consecutive patients (5 men) aged 44.7 ± 11.8 years (range, 23 to 72 years), including 7 patients with limb-girdle dystrophy, 2 patients with Duchenne muscular dystrophy, and 2 patients with amyotrophic lateral sclerosis and no respiratory complaints, were studied. Patients were ambulatory and wheelchair bound. The standard criteria were used to select pa-tients.  website 
None of the patients had a scoliosis or any abnormalities shown on chest radiography or obvious abnormalities in diaphragm placement. Five patients were current mild smokers (< 5 pack-years). Seventeen healthy normal subjects matched for age (range, 26 to 62 years; mean, 41.5 years) and sex (8 men) were studied as a control group. The study was approved by the local ethics committee, and subjects gave their informed consent. The anthropometric characteristics of the patients are shown in Table 1.