The effects of three nebulized osmotic agents in the dry larynx.

PURPOSE: This investigation examined the effects of nebulized hypertonic saline, isotonic saline (IS), and sterile (hypotonic) water on phonation threshold pressure (PTP) and self-perceived phonatory effort (PPE) following a surface laryngeal dehydration challenge. METHOD: In a double-blind, randomized experimental trial, 60 vocally healthy women (n = 15 per group) underwent a laryngeal desiccation challenge involving oral breathing for 15 min using medical-grade dry air (RH<1%). Three of the four groups then received nebulized isotonic saline (0.9% NaCl), hypertonic saline (7% NaCl), or sterile (hypotonic) water, respectively; the 4th group served as a nontreatment control. PTP and PPE were estimated for high-pitched productions at baseline, immediately postdesiccation, and at 5, 20, 35, and 50 min postnebulization. RESULTS: PTP increased significantly for all groups following the desiccation challenge. PTP values were, on average, 0.5 cm H(2)O greater immediately postdesiccation versus baseline. In contrast, PTP values did not change significantly following the administration of nebulized treatments, although a temporary trend toward a reduction in PTP was observed for the IS group. Unexpectedly, PPE ratings decreased significantly after the desiccation challenge. In general, PPE ratings were poorly correlated with PTP measures. CONCLUSION: A laryngeal desiccation challenge (i.e., temporary exposure to extremely low relative humidity while breathing transorally) significantly increased PTP. Although interesting trends emerged, none of the nebulized treatments significantly enhanced recovery from the negative effects of desiccation on PTP. In light of very low correlations between PTP and PPE, serious questions are raised regarding presumed associations between these measures.