Sleep Apnea Research Group

Grant Proposals

"Evaluation of a Comprehensive Sleep Apnea Disease-Severity Staging System."

Principal Investigator: Karthik Balakrishnan, MD
Co-Principal Investigator: Edward M. Weaver, MD, MPH

The apnea-hypopnea index (AHI) is the generally accepted metric of disease severity in obstructive sleep apnea syndrome (“sleep apnea”). Changes in AHI are often used as an outcome measure in clinical practice and research. However, in sleep apnea patients, AHI does not correlate well by itself with important aspects of the disorder, such as quality of life, daytime sleepiness, and reaction times. In 1998, Piccirillo and colleagues proposed a clinical-severity staging system comprising multiple aspects of sleep apnea, including anatomic (pharyngeal morphology), anthropomorphic (obesity), subjective (daytime sleepiness), and physiologic (AHI, lowest oxyhemoglobin saturation) elements. They demonstrated a dose-response relationship between this system and general health status, suggesting that it may reflect aspects of sleep apnea as a disease beyond those for which AHI is a physiologic surrogate. Nevertheless, this system has not been further evaluated in either clinical practice or research since its development. We thus propose a cross-sectional study of a cohort of sleep apnea patients at the time of diagnosis that will more extensively evaluate this system. This study is an independent construct validation with the hypothesis that the clinical severity index generated by this staging system is better associated than AHI alone with important patient-centered variables such as health status, sleep apnea-specific quality of life, and sleep quality, as well as physiologic variables (intermittent hypoxia) and markers of cardiovascular risk, namely arterial blood pressure and serum C-reactive protein. We will also examine a modified version of the system, replacing pharyngeal morphology with the more clearly defined tonsil size. A bootstrapping method will be used to generate mean correlation coefficients with standard deviations, in order to allow comparison of associations. If the clinical severity index is found to be better associated with outcomes than is AHI, this study will act as a pilot for future work on associations with CPAP success and operative therapy. This index may thus provide a more comprehensive, appropriate measure of disease severity and therapeutic effectiveness, with implications for both clinical practice and research.

“Nasal Turbinate Reductions and CPAP Outcomes for Sleep Apnea: A Sham-Controlled RCT”

Principal Investigator: Edward M. Weaver, MD, MPH
Co-Investigator: Richard A. Deyo, MD, MPH; Patrick J. Heagerty, MS, PhD; Vishesh Kapur, MD, MPH; Nathaniel F. Watson, MD

Obstructive sleep apnea syndrome afflicts at least 2 – 4% of adults and is associated with significant morbidity and mortality. Continuous positive airway pressure (CPAP) therapy is the primary treatment for sleep apnea in adults, but non-adherence to CPAP limits its effectiveness. Even with maximal medical therapy, nasal obstruction is common in sleep apnea patients and may hamper both CPAP adherence and efficacy. However, nasal obstruction (turbinate hypertrophy) is surgically correctable, and treatment of nasal obstruction may lead to more successful use of CPAP. The long-term goal of the proposed research is to develop a novel, multi-disciplinary, multi-modal approach to therapy, in order to improve clinically important treatment outcomes for sleep apnea. The short-term objectives of this proposal are to: 1) Quantify the effect of nasal turbinate reduction on the nasal airway; 2) Determine whether turbinate reduction increases CPAP use or efficacy; and 3) Determine whether turbinate reduction positively influences CPAP treatment outcomes. We will employ a single-site, randomized, double-blind, sham-placebo-controlled trial to test the hypotheses that turbinate reduction: 1) increases nasal airway cross-sectional area; 2) increases mean nightly objective CPAP use; and 3) improves sleep apnea quality of life 3 months after CPAP titration. We will use the radiofrequency turbinate reduction surgical technique, which allows ethical randomization and effective blinding. Three, six, and 12 months after turbinate reduction and CPAP titration we will measure the change in the minimal nasal cross-sectional area, level of CPAP use, and improvement in sleep apnea quality of life. Secondary outcomes will capture this treatments broader impact on the nose, CPAP, and sleep apnea. If turbinate reduction can be shown to improve sleep apnea outcomes through increased use or efficacy of CPAP therapy, this trial will demonstrate the value and effectiveness of a novel, multi-disciplinary, combined medical-surgical approach to the management of obstructive sleep apnea syndrome.
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