Effects of Varying Lengths and Diameters During Straw Phonation on an Excised Canine Model.
Jacob Tangney, Austin Scholp, Jing Kang and 2 others
PMID 31353125WHAT IT FOUND
In excised canine larynges, straws of 5-25 cm and 9-15 mm diameter lowered the pressure needed to start phonation.
The 3 mm diameter often blocked airflow entirely. These findings explain the mechanics of straw phonation but do not prove clinical benefit in humans.
Key findings
01Straw lengths of 5 cm and 25 cm significantly decreased the phonation threshold pressure compared to the control condition.
02Restriction diameters of 3 mm, 9 mm, and 15 mm significantly reduced phonation threshold pressure, with 15 mm showing the largest change excluding the unreliable 3 mm condition.
03The 3 mm restriction failed to achieve phonation in the majority of larynges because the supraglottal pressure created was too high, lowering the transglottal pressure below the threshold for vibration.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used excised canine larynges, which cannot replicate the dynamic shape changes and active muscle adjustments a human vocal tract makes during therapy. The 3 mm restriction data is based on only 12 of 29 larynges because the others failed to phonate, limiting generalizability for narrow straws. The model is static and hard-walled, so it does not account for soft tissue compliance or real-world patient variability. No human subjects were involved, so clinical efficacy and patient comfort cannot be assessed.
Declared interests
The authors declare no conflicts of interest. The canine larynges were donated by Covance Labs.
The easy way to misread this
Do not assume these aerodynamic findings translate directly to patient outcomes. The inability of the 3 mm straw to induce phonation in this model may be an artifact of the static, hard-walled setup, as human vocal tracts are flexible and can adjust to narrow straws in ways this bench cannot.