Maximum phonation time as a tool of screening respiratory muscle weakness in myopathic patients

UNLABELLED: We examined the relation of maximum phonation time (MPT) and vital capacity (VC) and reviewed the usefulness of MPT as a respiratory function screening. SUBJECTS: 18 healthy adult subjects (8 men and 10 women), and 32 myopathic patients (24 men and 8 women). METHODS: MPT and VC were measured in sitting position. Six patients were tested with and without air stacking by glossopharyngeal respiration. RESULTS: In healthy subjects, MPT was 29.9 +/- 11.8 seconds in men and 21.7 +/- 7.8 seconds in women. Second trials showed good reproducibility. The healthy group had no correlation between MPT and VC. The patient group showed a significant positive correlation between MPT and VC (r2= 0.25, p=0.003). All patients with MPT less than 15 seconds showed VC less than 1.5 l and %VC less than 50%. Air-stacking by glossopharyngeal respiration significantly increased the MPT. CONCLUSIONS: MPT is a useful screening test for respiratory muscle weakness. The patients are easily aware of the effect of air-stacking by glossopharyngeal respiration.