Background: HFCWO is commonly used for airway clearance. However the effect of mucus clearance on the rheological property, driving pressure and frequency during HFCWO is not clear. The purpose of this study is to clarify differences of airway clearance efficacy. Method: 24 normal subjects participated in the study 1. Mucus stimulants (MS) were prepared using thickener 1, 2, 3 and 4% and the pressure controls of SmartVest™ were driven 20, 40 and 60 on the frequency 13Hz. MS rheological studied were measured using Rheometer. They were quiet breathing into the endotracheal tubes having internal diameter of 7mm during SmartVest™. We measured migration velocity of each MS, PEFR, PEmax and effortless breathing. Another 26 normal subjects participated in the study 2. MS were prepared using similar thickener were driven frequency 9Hz, 13Hz and 17Hz on the driving pressure 40. Measurement methods and items were carried out in a similar manner of Study 1. Results: The higher setting pressure and frequency controls droved, the more PEFR and PEmax increased (p<0.05). In the rheology of MS, the lower viscoelasticity of 1% MS had, the faster clearance velocity moved (p<0.05). However, the clearance velocity did not increase in the higher viscoelasticity of MS in spite of high driving pressure. The 13Hz oscillation was most reduced in viscoelasticity and yield value by comparison with 9Hz and 17Hz. The lower viscoelasticity of MS in the each frequency, the clearance velocity increased (p<0.05). The subjects were not tolerable on17Hz. Conclusions: The oscillation of 13Hz and driving pressure 40 is the most effective for mucus clearance.
Miyagawa et al. (Thu,) studied this question.
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