Normal values and predictive equations for aerodynamic function in British Caucasian subjects.

Many useful objective measurements of air volume and flow may be made with a high degree of validity and reliability using present-day respirometers within a speech clinic. We have studied measures of aerodynamic function in 76 British Caucasian subjects and derived reference equations for mean flow rate (MFR), phonation quotient (PQ), vocal velocity index (VVI), phonation time and the phonation volume/vital capacity ratio. Measures from resting breathing patterns have also been investigated. Age was found to be an important determinant in the reference equations. MFR, PQ and VVI were all greater than previously reported. The equations derived in this study should provide a more appropriate assessment of aerodynamic function than the previously reported normal ranges.