Variability of specific airway resistance in patients with laryngeal hemiplegia.

OBJECTIVES: This study was designed to analyze whether respiratory flows and specific airway resistance (sRaw) depend on the degree of breathiness and on the position of the paralyzed vocal fold in laryngeal hemiplegia. METHODS: We performed a prospective study involving 55 patients affected by laryngeal hemiplegia. RESULTS: The paralyzed fold was in an intermediate position in 18 cases and in a paramedian position in 37. Breathiness was estimated with the GRBAS scale, and the patients were divided into four groups: B0 (12 patients), B1 (14), B2 (16), and B3 (13). Spirometry was used to measure the flow-volume loop, and body plethysmography was used to measure the sRaw at increasing respiratory frequencies (30 +/- 5, 60 +/- 5, and 90 +/- 5 breaths per minute). The mean inspiratory flows (PIF, FIF50) were lower than predicted (<80%) in all four groups; there was no significant intergroup difference. In all four groups, the mean FEF5o/FIF50 ratio was >1, as is typical of variable extrathoracic obstruction. The mean sRaw values increased with respiratory frequency, and the increase was higher in group B3, although the values varied widely. The frequency-dependent increase in the sRaw value was not significantly related to the degree of breathiness, nor to the position of the paralyzed fold. Furthermore, Spearman's coefficient did not reveal any correlation between the sRaw values and inspiratory flows, showing that plethysmography and spirometry explore different aspects of airway function. CONCLUSIONS: Respiratory flows and sRaw are not significantly influenced by either the degree of breathiness or the position of the paralyzed vocal fold.