Comparison of Methods of Eliciting Vital Capacity: Forced Versus Slow Vital Capacity.
S N Awan, J A Awan
PMID 39814619WHAT IT FOUND
Forced and slow vital capacity measurements showed no significant difference in healthy young adults.
The two methods produced highly correlated results and can be considered interchangeable in this population, meaning either can be used for basic voice evaluation.
Key findings
01Mean differences between slow and forced vital capacity were not statistically significant across all three measurement devices tested.
02Slow and forced vital capacity measurements were extremely strongly correlated regardless of the device used.
03The authors conclude that these two measures are essentially interchangeable for non-respiratory disordered young adults.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study only included young, healthy adults, so the findings cannot be applied to older patients or those with respiratory or neurological conditions, where the difference between forced and slow vital capacity may be significant. The vortex whistle device is experimental and not yet available for clinical use. The study measured capacity but did not assess how these differences impact actual voice production or speech quality.
Declared interests
The authors declare no competing financial interests or personal relationships that could have influenced the work.
The easy way to misread this
Do not assume forced and slow vital capacity are interchangeable for all patients. This study only tested healthy young adults; in older or disordered populations, forced maneuvers may underestimate lung capacity and cause complications like fainting, making the slow method safer and more accurate.