• Spasmodic dysphonia;
  • laryngeal resistance;
  • airflow interruption;
  • mean flow rate;
  • subglottal pressure



To measure the laryngeal resistance (RL), subglottal pressure (Ps), and mean flow rate (MFR) of adductor (ADSD) and abductor (ABSD) spasmodic dysphonia patients using the airflow interrupter.


The RL of six ABSD and seven ADSD patients was measured using the airflow interrupter, a noninvasive device designed to measure MFR and Ps via mechanical balloon valve interruption. Subjects performed 10 trials at each of two intensity levels, with each trial consisting of a sustained /a/ during which phonation was interrupted for 500 ms. Laryngeal resistance was calculated as subglottal pressure divided by airflow.


Mean RL for the ADSD and ABSD subtypes at 65 dB were 24.78 cmH2O/L/s and 14.51 cmH2O/L/s, respectively (P = .04). Mean RL at 70 dB were 40.02 cmH2O/L/s and 15.84 cmH2O/L/s (P = .014). Ps for the ADSD and ABSD subtypes at 65 dB were 10.23 cmH2O and 8.32 cmH2O, respectively (P = .582). At the 70 dB level, Ps were 12.39 cmH2O and 11.78 cmH2O (P = .886). MFR for the ADSD and ABSD subtypes at 65 dB were 435 mL/s and 746 mL/s (P = .205). Mean MFR at 70 dB were 518 mL/s and 848 mL/s (P = .198).


Noninvasive measurements of RL may be useful for differentiating between ADSD and ABSD. This simple objective test, which produces a quantitative output, could be used to evaluate laryngeal function in patients with spasmodic dysphonia. Laryngoscope, 2009