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Laryngoscope. 2009 Sep;119(9):1851-5. doi: 10.1002/lary.20572.

Differentiating between adductor and abductor spasmodic dysphonia using airflow interruption.

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  • 1Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.



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


The R(L) of six ABSD and seven ADSD patients was measured using the airflow interrupter, a noninvasive device designed to measure MFR and P(s) 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 R(L) for the ADSD and ABSD subtypes at 65 dB were 24.78 cmH(2)O/L/s and 14.51 cmH(2)O/L/s, respectively (P = .04). Mean R(L) at 70 dB were 40.02 cmH(2)O/L/s and 15.84 cmH(2)O/L/s (P = .014). P(s) for the ADSD and ABSD subtypes at 65 dB were 10.23 cmH(2)O and 8.32 cmH(2)O, respectively (P = .582). At the 70 dB level, P(s) were 12.39 cmH(2)O and 11.78 cmH(2)O (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 R(L) 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.

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