The pressure-flow method: some fundamental concepts

• Published in: The Cleft palate journal Vol. 27; no. 2; p. 193
• Main Authors: Yates, C C, McWilliams, B J, Vallino, L D
• Format: Journal Article
• Language: English
• Published: United States 01.04.1990
• Subjects: Humans; Models, Biological; Palate, Soft - anatomy & histology; Pharynx - anatomy & histology; Pressure; Pulmonary Ventilation - physiology; Rheology
• ISSN: 0009-8701
• DOI: 10.1597/1545-1569_1990_027_0193_tpfmsf_2.3.co_2

The pressure-flow method introduced by Warren and DuBois is a useful method for estimating velopharyngeal orifice area. However, this investigation shows that unless geometric similarity of subject and model exists, the value of the flow coefficient k used in the equation to estimate velopharyngeal orifice area cannot be established from model tests. Use of k = 0.65 is questioned as that value is typical of thin plate orifices, a geometry that is not a good representation of the velopharyngeal passage. Values of k from the literature and from steady state tests using a model similar to Warren's are presented to show the effect of various inlet shapes. The influence of inlet shape supports the conclusion that k may be significantly higher than 0.65, conceivably approaching values in the range of 0.9 to 0.97, depending on the orifice geometry.