Published ahead of print on January 11, 2007, doi:10.1164/rccm.200608-1205OC Am. J. Respir. Crit. Care Med., Volume 175, Number 7, April 2007, 726-730 A more recent version of this article appeared on April 1, 2007
Submitted on August 24, 2006 Use of Flow-Volume Curves to Predict Oral Appliance Treatment Outcome in Obstructive Sleep ApneaBiao Zeng1,1 Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, University of Sydney, Sydney, NSW, Australia; Department of Respiratory and Sleep Medicine, St George Hospital, University of New South Wales, Sydney, NSW, Australia, 2 Department of Respiratory and Sleep Medicine, St George Hospital, University of New South Wales, Sydney, NSW, Australia, 3 Discipline of Orthodontics, Sydney Dental Hospital, Sydney, NSW, Australia, 4 Department of Statistics, Macquarie University, Sydney, NSW, Australia, 5 Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, University of Sydney, Sydney, NSW, Australia; Department of Respiratory and Sleep Medicine, St George Hospital, University of New South Wales, Sydney, NSW, Australia; Woolcock Institute of Medical Research, Sydney, NSW, Australia * To whom correspondence should be addressed. E-mail: cistullip{at}med.usyd.edu.au.
Background: It has been recognised that mandibular advancement splint (MAS) treatment is effective in some, but not all, patients with OSA. Hence there is a need for a simple and reliable clinical tool to assist in the differentiation of treatment responses. We hypothesized that abnormalities of flow-volume curves, together with other clinical variables, may have clinical utility in the prediction of MAS treatment outcome. Methods: 54 patients with known OSA underwent MAS treatment. Expiratory and inspiratory flow-volume curves were measured in the erect and supine positions to derive mid-inspiratory flow (MIF50) and the ratio of expiratory to inspiratory flow at 50% of vital capacity (MEF50/MIF50). Multivariable logistic regression was performed to identify additional significant clinical variables in the prediction of treatment outcome. Results: The mean (±SD) AHI in 35 Responders was significantly reduced from 28.9 ± 13.7/h to 6.7 ± 5.8/h (p < 0.001). In 19 Non-Responders there was no significant change in AHI. MIF50 was lower (6.04 ± 1.80 L/s vs 6.88 ± 1.08 L/s; p = 0.035) and MEF50/MIF50 ratio higher (0.82 ± 0.23 vs 0.61 ± 0.15; p = 0.001) in Responders than Non-Responders. Logistic regression analysis revealed that MEF50/MIF50 ratio was the most important predictive factor for MAS treatment outcome, but that BMI, age and baseline AHI were also contributory. Conclusions: These data suggest that flow volume curves, in combination with other factors such as BMI, age, and baseline AHI, may have a useful clinical role in the prediction of treatment outcome with MAS. Key words: Obstructive sleep apnea, flow-volume curves, spirometry, oral appliances
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