Phonation threshold pressure and flow in excised human larynges

Area of Science:

• Laryngeal physiology
• Acoustic phonetics
• Aerodynamics of voice production

Background:

• Phonation threshold pressure (PTP) and phonation threshold flow (PTF) are critical aerodynamic parameters of voice production.
• Understanding these parameters in excised human larynges is essential for comparative analysis with in vivo and animal studies.

Purpose of the Study:

• To measure PTP and PTF in excised human larynges.
• To investigate the influence of posterior glottal width, glottal area, and gender on PTP and PTF.
• To determine if hysteresis occurs during phonation in excised larynges.
• To compare findings with canine experiments and human subject measurements.

Main Methods:

• Induced phonation was performed on nine fresh, excised human larynges within 24 hours postmortem.
• PTP and PTF were measured at phonation onset and offset using a laboratory bench apparatus.
• The impact of posterior glottal width, glottal area, and gender was analyzed.

Main Results:

• Significant intersubject variability was observed in both PTP and PTF.
• PTP values were comparable to in vivo measurements, but PTF was considerably higher.
• No significant effect of posterior glottal width on PTP or PTF was found.
• Hysteresis was present, with offset PTP and PTF being lower than onset values.
• Offset measurements demonstrated significantly less variability than onset measurements (P = .012 for PTP, P = .0001 for PTF).

Conclusions:

• This study provides novel data on onset and offset PTP and PTF in fresh excised human larynges.
• Higher PTF values may be attributed to vocal fold bowing and direct current flow.
• Offset PTP and PTF measurements appear to be more intrinsically reliable.
• The substantial intersubject variability in PTP and PTF suggests potential challenges for direct clinical application.