Obstructive sleep apnea, positive airway pressure treatment, and postoperative delirium: protocol for a retrospective observational study
Authors: King Christopher R , Escallier Krisztina , Ju Yo-El S. , Lin Nan , Palanca Ben Julian A. , McKinnon Sherry , Avidan Michael S 
Published: July 2019

ABSTRACTIntroductionObstructive sleep apnea (OSA) is common among older surgical patients, and delirium is a frequent and serious postoperative complication. Emerging evidence suggests that OSA increases the risk for postoperative delirium. We hypothesize that OSA is an independent risk factor for postoperative delirium, and that in patients with OSA, perioperative adherence to positive airway pressure (PAP) therapy decreases the incidence of postoperative delirium and its sequelae. The proposed retrospective cohort analysis study will use existing datasets to: (i) describe and compare the incidence of postoperative delirium in surgical patients based on OSA diagnosis and treatment with PAP; (ii) assess whether preoperatively untreated OSA is independently associated with postoperative delirium; and (iii) explore whether preoperatively untreated OSA is independently associated with worse postoperative quality of life. The findings of this study will inform on the potential utility and approach of an interventional trial aimed at preventing postoperative delirium in patients with diagnosed and undiagnosed OSA.Methods and AnalysisObservational data from existing electronic databases will be used, including over 100,000 surgical patients and ∼10,000 intensive care unit (ICU) admissions. We will obtain the incidence of postoperative delirium in adults admitted postoperatively to the ICU who underwent structured preoperative assessment, including OSA diagnosis and screening. We will use doubly robust propensity score methods to assess whether untreated OSA independently predicts postoperative delirium. Using similar methodology, we will assess if untreated OSA independently predicts worse postoperative quality of life.Ethics and disseminationThis study has been approved by the Human Research Protection Office at Washington University School of Medicine. We will publish the results in a peer-reviewed venue. Because the data is secondary and high risk for re-identification, we will not publicly share the data. Data will be destroyed after 1 year of completion of active IRB approved projects.Article summaryStrengths and limitations of this study, (containing 5 short bullet points, no longer than one sentence each, that relate specifically to the methods)Our granular database includes routine structured preoperative screening for OSA, processed laboratory results, and verified comorbid diagnoses.We have limited information on the severity of most comorbidities, creating the possibility for substantial residual confounding.Our database includes near-universal and standardized nurse-driven delirium evaluations at multiple time-points as well as clinician diagnoses.Compared to prior studies, the large sample size will allow for more aggressive confounder adjustment utilizing linked structured medical histories, intraoperative records, and administrative data.Selection bias and confounding by indication are important limitations, which we will address using advanced statistical methods.