Effects of loudness cues on respiration in individuals with Parkinson's disease.

Individuals with Parkinson's disease (PD) demonstrate low vocal intensity (hypophonia) which results in reduced speech intelligibility. We examined the effects of three cues to increase loudness on respiratory support in individuals with PD. Kinematic data from the rib cage and abdomen were collected using respiratory plethysmography while participants read a short passage. Individuals with PD and normal age- and sex-matched controls (OC) increased sound pressure level (SPL) to a similar extent. As compared to OC, individuals with PD used larger rib cage volume excursions in all conditions. Further, they did not slow their rate of speech in noise as OC speakers did. Respiratory strategies used to support increased loudness varied with the cue, but the two groups did not differ in the strategies used. When asked to target a specific loudness, both groups used more abdominal effort than at comfortable loudness. Speaking in background noise resulted in the largest increase in SPL with the most efficient respiratory patterns, suggesting that natural or implicit cues may be best when treating hypophonia in individuals with PD. Data demonstrate the possibility that both vocal loudness and speech rate are impacted by cognitive mechanisms (attention or self-perception) in individuals with PD.