Original ArticlePrevalence of undiagnosed obstructive sleep apnea among adult surgical patients in an academic medical center
Introduction
Obstructive sleep apnea (OSA) refers to a condition where those affected periodically have obstruction to breathing while they sleep. Twenty-five percent of the US adult population is thought to be at high-risk for having OSA [1], and the estimated prevalence of OSA in the US adult population is 20% [2]. Some risk factors for OSA are male gender [3], [4], smoking [5], age >40 [4] and obesity [4], [6]. The prevalence of OSA is expected to rise as an increasing proportion of Americans are obese and elderly [7]. It is estimated that up to 90% of people with OSA are undiagnosed [8], which is likely owing to poor awareness of OSA [9], a lack of routine screening, and the limited number of diagnostic sleep study facilities [10].
Much of the preoperative assessment before surgery has focused on the diagnosis and management of heart and lung diseases. There has been little emphasis on screening for or diagnosing sleep-disordered breathing prior to surgery [11]. However, patients with OSA may be more vulnerable during the perioperative period, particularly if they receive general anesthesia and opioid analgesia. These medications could diminish the protective arousal reflex and may thereby increase the risk for prolonged periods of apnea and respiratory arrest [12]. In addition, these medications can worsen existing OSA by increasing upper airway resistance by decreasing pharyngeal muscle tone [12]. These outcomes may be more likely to happen when the care providers are unaware of their diagnosis and cannot properly identify these patients to take preventative precautions.
Outcome studies on specific surgical populations have shown that patients with OSA have a higher incidence of postoperative complications [13], [14], [15], [16], [17] such as unplanned ICU admissions, longer hospital stay, longer ICU stay, postoperative encephalopathy, and postoperative infection [15], [16]. Even patients who are suspected to have OSA based on screening questionnaires may have increased postoperative respiratory complications [13], [14]. OSA is also associated with numerous comorbidities such as diabetes [18], hypertension [19], stroke [20], heart failure [21], and coronary artery disease [21]. Furthermore, OSA is associated with an increased risk of mortality independent of these comorbidities [20].
Recently the American Society of Anesthesiologists (ASA) published guidelines on caring for surgical patients with OSA which state that perioperative risk directly increases with severity of OSA [22]. For this reason, the guidelines stress the importance of screening all surgical patients for risk factors for OSA and then modifying perioperative care and increasing vigilance for surgical patients at risk for OSA. The ASA has proposed an OSA risk stratification screen, based predominantly on the severity of OSA, the risks of surgery and the likely administration of sedative and analgesic medications [22]. However, no studies have demonstrated the feasibility of universal screening in the preoperative setting to identify those with undiagnosed OSA and to implement changes in identifying and monitoring these patients.
The proportion of adult surgical patients who have undiagnosed OSA has not been well established. We therefore conducted a single-center, prospective, observational study to establish the prevalence of undiagnosed OSA among adult surgical patients with a preoperative OSA screening program.
Section snippets
Materials and methods
The Human Research Protection Office (HRPO) at Washington University School of Medicine approved this study. A waiver of written consent was granted for the voluntary screening portion of this study as completion of the questionnaire gave implied consent. All participants who agreed to use the home testing device for OSA signed written, informed consent.
All participants undergoing elective surgery at our urban tertiary care referral center attended the preoperative assessment clinic. Adult
Results
We screened 2877 adult patients in the preoperative assessment clinic (Fig. 1). Of the 2778 patients who completed the screening questionnaire, 661 (23.7%) screened high-risk for OSA. There were 173 (6.2%) patients who had a previous diagnosis of OSA: 127 of them screened high-risk and 46 did not screen high-risk. These patients were excluded from analysis.
There were 534 patients who screened high-risk for OSA and were without a previous diagnosis of OSA. Patient characteristics of our surgical
Discussion
Almost a quarter of adult patients presenting for surgery at a tertiary care referral center screened high-risk for OSA. The majority of those who screened high-risk and underwent home testing were found to have OSA. Most of the patients who screened high-risk had not previously been diagnosed with OSA; only 6% of all patients had a prior diagnosis of OSA.
The validity of this study rests on a number of assumptions. The first is that the home studies are accurate in diagnosing OSA and
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