Assessment of phonation threshold pressure: a critical review and clinical implications.

PURPOSE: To describe the origins of the task elicitation procedure for determining phonation threshold pressure and, through a literature review and online survey, describe published procedural, environmental, and participant variable departures from the original methodology.
METHOD: Literature search terms included phonation threshold pressure, subglottal pressure and phonation, pressure measurement and phonation, lung pressure and phonation, and vocal fold oscillation onset. Inclusion criteria were limited to indirect assessment of phonation threshold pressure, English language publications between 1980 and 2009, and peer-reviewed journals. Studies including animals, computer or physical models, alaryngeal speakers, laryngeal airway resistance, or any airflow interruption technique were excluded. Twenty-four articles matched the inclusionary criteria. An online survey to query task elicitation procedures was then developed from the literature review.
RESULTS: The scientific rationale for inclusion of phonation threshold pressure data was consistent across published studies; however, variations in procedural methodology for task elicitation were identified, as were environmental and participant inconsistencies that might affect phonation threshold pressure values. Findings of the online survey mirrored the inconsistencies identified in the literature review.
CONCLUSIONS: The methodological differences for task elicitation identified in this comprehensive review of the literature and the online survey, while bringing into question the reliability of phonation threshold pressure measurement, illuminate scientific questions yet to be answered to further refine and potentially standardize phonation threshold pressure as a more reliable research and clinical measurement.