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Screening adults for obstructive sleep apnea Hisham Elsaid, Frances Chung

Obstructive sleep apnea (OSA) is the most prevalent breathing disturbance during sleep [1], affecting 2% to 6% of the general population, depending on age, sex, and the definition of criteria [2]. An estimated 82% of men and 92% of women with moderate to severe OSA have not been diagnosed [3]. Sleep apnea events are defined as a complete cessation of breathing (apnea) or a marked reduction in airflow (hypopnea) during sleep, and are considered clinically relevant if they last more than 10 seconds. The episodes of apneas and hypopneas may persist for 30 to 60 seconds in some individuals. OSA is characterized by repetitive obstruction of the upper airway, often resulting in oxygen desaturation and arousals from sleep. The classic daytime manifestation is excessive sleepiness, and other symptoms such as non-refreshing sleep, poor concentration, and fatigue are commonly reported [4]. OSA is a serious condition that diminishes the quality of life [5] and is also associated with many common comorbidities. Studies have documented an increased incidence of coronary artery disease, hypertension, congestive heart failure, cerebrovascular accidents, and gastroesophageal reflux disease in OSA patients [6,7]. It is estimated that the average life span of an untreated OSA patient is 58 years, much shorter than the average life spans of 78 years for men and 83 years for women [8]. The signs and symptoms of OSA are shown in Table 1.

airway, resulting in OSA. Grunstein et al [11] performed polysomnography on 53 patients with acromegaly who were referred to a sleep disorder center. A high prevalence of OSA was found in patients both clinically suspected of having OSA and those not suspected of having it.

ETIOLOGIC AND PREDISPOSING FACTORS

Alcohol and sedatives

Airway structural abnormalities

Several pharmacologic agents have been shown to induce or exacerbate OSA, either by suppressing the arousal threshold or by selectively reducing neuromuscular control of the upper airway [16]. Alcohol, even in moderate amounts, has been documented to exacerbate existing OSA and to induce apneic activity in asymptomatic individuals [17]. Also, benzodiazepines have been documented to exacerbate existing OSA, mainly by increasing the duration of apneic events and the degree of oxygen desaturation [18,19]. Dose-dependent depression of muscle activity of the upper airway by general anesthesia is well established: most anesthestics and narcotics can alter breathing by affecting the chemical, metabolic, or behavioral control of breathing [20]. An important consideration in the choice of inhaled anesthetic is the presence of any carry-over anesthetic effects into the postoperative period that could impair respiration and/or potentiate the deleterious respiratory effects of analgesics [21]. Opioids can profoundly impair respiration in the postoperative period, leading to obstructive apneas and drastic oxygen desaturation. Although there remains a

The upper airway is the site of occlusion in OSA, and the points of airflow limitation include the nares, the nasopharynx, the oropharynx and the hypopharynx [9]. Structural abnormalities, including obesity-related fat deposits [10], may cause narrowing of the normal upper airway lumen and exacerbate sleep-disturbed-related episodes. Acromegaly Conditions that increase soft-tissue growth can, theoretically, cause narrowing and obstruction of the upper

Hot Topics in Respiratory Medicine - Volume 4 • Issue 9 • Year 2009 © FBCommunication - Modena (Italy) Screening adults for obstructive sleep apnea Authors: Hisham Elsaid, Frances Chung E-mail: [email protected]

Thyroid deficiency Several authors have noted the presence of OSA in thyroid-deficient patients, and thyroid hormone replacement has been demonstrated to reduce sleepdisturbed breathing (SDB) in patients with myxoedema and polysomnographically documented OSA [12-14]. Orr et al [12] reported on three patients with profound myxoedema and severe OSA whose condition dramatically improved following thyroid hormone replacement. Genetics In an analytical study designed to assess familial OSA, Redline et al [15] used a standardized questionnaire to ascertain the prevalence of symptoms associated with SDB in first-degree relatives of 29 patients with polysomnographically documented OSA and 21 control volunteers. Although this study was suggestive of familial aggregation of sleep-related breathing disturbances, the lack of polysomnography studies in at least a sub-sample of first-degree relatives limits its validity.

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TABLE 1. Symptoms and signs of OSA DIURNAL SYMPTOMS OF OSA

NOCTURNAL SYMPTOMS OF OSA

Daytime sleepiness Memory and concentration dysfunction Sexual dysfunction Gastroesophageal reflux Behavioral irritability (irritability, depression, chronic fatigue, delerium) Road traffic accident

Heavy persistent snoring, worse in supine position or after alcohol or sedatives Apnea with limb movement, witnessed by bed partner Sudden awakening with noisy breathing Accidents related to sleepiness Nocturnal sweating Wake up with dry mouth Nocturnal epilepsy Nocturia

SIGNS ASSOCIATED WITH OSA Edematous soft palate or uvula Long soft palate and uvula Decreased oropharyngeal dimensions Nasal obstruction Maxillary hypoplasia Retrognathia Central adiposity and increased neck circumference Hypertension and other cardiovascular consequences

lack of good evidence in the literature of the impact of opioid administration on respiration in OSA patients, the general recommendation is that opioids and other drugs with central respiratory and sedating effects should be avoided, if possible [22,23]. Conditions predisposing to OSA are shown in Table 2.

DIAGNOSIS OF OBSTRUCTIVE SLEEP APNEA The diagnosis of OSA is established by an overnight sleep study, including polysomnography. Polysomnography is expensive to perform, requiring highly trained personnel, sophisticated equipment, and an entire night of recording. Most sleep centers typically have long waiting lists for polysomnography, resulting in delays in diagnosis and subsequent treatment. These long waiting lists and the limited resources have led to

TABLE 2. Predisposing conditions for OSA CONDITION Obesity Age Gender Neck circumference Nasal obstruction

EXAMPLE Adult obesity Greater than 50 years Male gender Greater than 40 cm As in septal deviation

Pharyngeal obstruction

Tonsillar and adenoidal hypertrophy

Laryngeal obstruction

Laryngomalacia, tracheomalacia

Craniofacial abnormalities

Down syndrome, micrognathia, achondroplasia, acromegaly, macroglossia

Endocrine and metabolic causes

Hypothyroidism, Cushing’s disease

Neuromuscular disorders

Stroke, cerebral palsy, head injury, poliomyelitis, myotonic dystrophy

Connective tissue disorders

Marfan sydrome

Genetic predisposition Alcohol, sedatives and smoking Medications and anesthesia

Benzodiazepines, anesthetics and narcotics

efforts to ‘predict’ whether patients may have a high risk of OSA based on their clinical features. This approach allows better use of polysomnography, reserving it for those patients who stand to gain the most from the investigation [24]. OSA is strongly correlated with obesity and is particularly prevalent in the morbidly obese, that is patients with a body mass index (BMI) ≥40 kg/m2 or BMI ≥35 kg/m2 with a significant associated comorbid condition [25-27]. OSA is found in 40% of obese females and 50% of obese males. OSA is a serious comorbid problem that should be evaluated and treated before a patient undergoes bariatric surgery. It has been suggested that all patients with BMI >40 kg/m2 should be screened for OSA [9], and OSA screening by polysomnography should be mandatory in all patients undergoing bariatric surgery [24].

SCREENING TOOLS FOR OBSTRUCTIVE SLEEP APNEA Many clinical models designed for OSA screening require the assistance of a computer and may not be suitable for clinical practice [26]. In addition, a number of the predictive models—based on different combinations of witnessed apneas, snoring, gasping, BMI, age, gender, and hypertension—were developed and validated in patients from sleep centers [24,27-31]; thus, these screening tools may not apply to the general population.

DEVELOPMENT OF QUESTIONNAIRES With general anesthesia and narcotics, OSA patients may have a higher perioperative risk of surgical complication. Because surgical patients normally have their visits to the preoperative clinic a few weeks before their surgery, the American Society of Anesthesiologists recently published a guideline recommending that patients should be screened at that time for risk of OSA [32]. Different questionnaires have been developed for this purpose: the American Society of Anesthesiologists check-list, the STOP questionnaire, and the STOP-Bang questionnaire [26,32]. Furthermore, the Berlin questionnaire

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was developed a number of years ago for screening OSA in the general population [33]. The Berlin questionnaire The Berlin questionnaire (BQ; Appendix 1) is a commonly used questionnaire for OSA, and has been validated for patients in the primary care setting [34]. The 10-item BQ contains five questions on snoring, three on excessive daytime sleepiness, one on sleepiness while driving, and one enquiring about a history of hypertension. Details of age, gender, weight, height, and neck circumference are also recorded. The BQ stratifies patients into high or low risk of having OSA based on their endorsement of symptom severity. The BQ performed well in a study of 744 primary care patients, yielding a sensitivity of 0.89 and a specificity of 0.71 [33,35]. Preliminary studies indicate that at AHI >15, about half of the high-risk patients identified by the BQ are subsequently found to have OSA by polysomnography [34]. Our own results showed that the BQ has a moderately high level of sensitivity, 68.9, in surgical patients, with a specificity of 56.4, a positive predictive value (PPV) of 77.9, and a negative predictive value (NPV) of 44.9 [36]. Even though the BQ does have a relatively high sensitivity and specificity for identifying OSA in the preoperative setting, the number of questions and the complicated scoring procedure may be too cumbersome for anesthesiologists in their busy preoperative clinics. The STOP questionnaire Recently, Chung et al [26] developed and validated the STOP questionnaire in surgical patients to facilitate the widespread use of an OSA screening tool. The BQ was condensed and modified into a shorter OSA screening questionnaire (STOP). The STOP questionnaire contains four questions: S – Do you snore loudly, loud enough to be heard through a closed door?; T – Do you feel tired or fatigued during the daytime almost every day?; O – Has anyone observed bserved that you stop breathing during sleep?; and P – Do you have a history of high blood pressure with or without treatment? ((Appendix 2). To keep the STOP questionnaire concise and easy to use, the questions were designed in a yes-or-no format. Patients are considered to be at high risk of OSA if they answer yes to two or more questions [26]. The sensitivity of the STOP questionnaire at AHI >5, >15, and >30 cutoff levels was found to be 65.6%, 74.3%, and 79.3%, respectively (Table 3). The STOP-Bang model An alternative scoring model combining the STOP questionnaire and Bang—BMI (B), age (a), neck circumference (n) and gender (g)—further improves the sensitivity of the STOP questionnaire to detect most cases of OSA, especially moderate and severe OSA ((Appendix 3). BMI >35 kg/m2, age above 50 years, male gender gender, and neck circumference >40 cm are scored as positive. Patients are considered to be at high risk of OSA if they display three or more of the traits [26]. The sensitivity of the STOP questionnaire increased to 83.6%, 92.9% and 100% for AHI cutoffs 5, 15 and 30, respectively, by using the STOP-Bang model [26] (see Table 3). The STOP-Bang model demonstrated a moderately high level of sensitivity and specificity in surgical patients, and it was better able to detect patients with moderate (AHI >15) to severe OSA (AHI >30). If the patient is ranked as having a low risk of OSA by the STOP-Bang model, one

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APPENDIX 1. Berlin Questionnaire Height m Weight kg Age Please choose the correct response to each question.

Male/Female

Category 1 1. Do you snore? a. Yes b. No c. Don’t know If you snore: 2. Your snoring is: a. Slightly louder than breathing b. As loud as talking c. Louder than talking d. Very loud—can be heard in adjacent rooms 3. How often do you snore? a. Nearly every day b. 3–4 times a week c. 1–2 times a week d. 1–2 times a month e. Never or nearly never 4. Has your snoring ever bothered other people? a. Yes b. No c. Don’t know 5. Has anyone noticed that you quit breathing during your sleep? a. Nearly every day b. 3–4 times a week c. 1–2 times a week d. 1–2 times a month e. Never or nearly never Category 2 6. How often do you feel tired or fatigued after your sleep? a. Nearly every day b. 3–4 times a week c. 1–2 times a week d. 1–2 times a month e. Never or nearly never 7. During your waking time, do you feel tired, fatigued, or not up to par? a. Nearly every day b. 3–4 times a week c. 1–2 times a week d. 1–2 times a month e. Never or nearly never 8. Have you ever nodded off or fallen asleep while driving a vehicle? a. Yes b. No If yes: 9. How often does this occur? a. Nearly every day b. 3–4 times a week c. 1–2 times a week d. 1–2 times a month e. Never or nearly never Category 3 10. Do you have high blood pressure? a. Yes b. No c. Don’t know The questionnaire consists of three categories related to the risk of having OSA. Categories and scoring: Category 1: items 1, 2, 3, 4, and 5 Item 1: If yes is the response, assign 1 point. Item 2: If c or d is the response, assign 1 point. Item 3: If a or b is the response, assign 1 point. Item 4: If a is the response, assign 1 point. Item 5: If a or b is the response, assign 2 points. Category 1 is positive if the total score is 2 or more points. Category 2: items 6, 7, and 8 (item 9 should be noted separately) Item 6: If a or b is the response, assign 1 point. Item 7: If a or b is the response, assign 1 point. Item 8: If a is the response, assign 1 point. Category 2 is positive if the total score is 2 or more points. Category 3 is positive if the answer to item 10 is yes or if the BMI of the patient is greater than 30 kg/m2. High risk of OSA: two or more categories scored as positive Low risk of OSA: only one or no category scored as positive (Data taken from Netzer NC, Stoohs RA, Netzer CM, Clark K, Kingman P, Strohl KP KP. Using the Berlin questionnaire to identify patients at risk for the sleep apnea syndrome. Ann Intern Med 1999;131:485-491)

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APPENDIX 2. STOP Questionnaire

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APPENDIX 3. STOP-Bang Scoring Model

1. Snoring: Do you snore loudly (loud enough to be heard through closed doors)? Yes No 2. Tired: Do you often feel tired, fatigued, or sleepy during daytime? Yes No 3. Observed: Has anyone observed you stop breathing during your sleep? Yes No 4. Blood pressure: Do you have or are you being treated for high blood pressure? Yes No High risk of OSA: answering yes to two or more questions Low risk of OSA: answering yes to fewer than two questions (Data taken from Chung F, Yegneswaran B, Liao P, et al. STOP questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology 2008;108:812-821)

can be confident in excluding moderate to severe sleep apnea [26]. The ASA checklist In its recent guidelines for perioperative management of OSA patients, the American Society of Anesthesiologists (ASA) Task Force on OSA [32] developed a 14-item checklist to assist anesthesiologists in identifying patients at high risk of OSA. The checklist contains three categories of predisposing physical characteristics, symptoms, and complaints attributable to OSA ((Appendix 4). Patients endorsing symptoms or signs in two or more of the categories are considered to be at high risk of having OSA. The major drawback to this screening tool is the time commitment, because the checklist needs to be completed by a clinician. The checklist is a consensus of the ASA Task Force and had not been validated in any patient population. Recently, we validated the ASA checklist in surgical patients and found that its sensitivity and specificity in predicting OSA are similar to those of the STOP questionnaire (see Table 3). Other questionnaires A number of screening tools in the literature—the Sleep Disorders Questionnaire (SDQ) [37], the Hawaii sleep questionnaire [38], the Wisconsin questionnaire [4], the self-

1. Snoring: Do you snore loudly (louder than talking or loud enough to be heard through closed doors)? Yes No 2. Tired: Do you often feel tired, fatigued, or sleepy during daytime? Yes No 3. Observed: Has anyone observed you stop breathing during your sleep? Yes No 4. Blood pressure: Do you have or are you being treated for high blood pressure? Yes No 5. BMI: BMI more than 35 kg/m2 Yes No 6. Age: Age over 50 years Yes No 7. Neck circumference: Neck circumference greater than 40 cm Yes No 8. Gender: male Yes No High risk of OSA: answering yes to three or more items Low risk of OSA: answering yes to fewer than three items (Data taken from Chung F, Yegneswaran B, Liao P, et al. STOP questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology 2008;108:812-821)

reported questionnaire by Haraldsson et al [39], the selfreported questionnaire by Pouliot et al [40], the modified Berlin questionnaire [41], and the modified Wisconsin questionnaire [42]—were all developed and tested in patients mainly from sleep centers. Patients referred to sleep centers are suspected of having sleep-related disorders, especially OSA. Thus, they are preselected patients, and screening tools for OSA developed and validated in sleep centers cannot be applied to other patient populations without validation in the target patient population [26].

THE PERIOPERATIVE SETTING There has been very little research on OSA patients and their perioperative morbidity and mortality. Case reports comprise most of the literature in this area. It has been postulated that the cardiorespiratory consequences of OSA may be exacerbated in the perioperative setting due to the adverse effects of anesthetics and analgesics

TABLE 3. Predictive parameters of Berlin, ASA, STOP and STOP-Bang STOP

STOP-Bang

BERLIN

ASA

AHI >5 Sensitivity% Specificity% PPV% NPV% Odds ratio

65.6 60.0 78.4 44.0 2.857

83.6 56.4 81.0 60.8 6.587

68.9 56.4 77.9 44.9 2.855

72.1 38.2 72.1 38.2 1.559

AHI >15 Sensitivity% Specificity% PPV% NPV% Odds ratio

74.3 53.3 51.0 76.0 3.293

92.9 43.0 51.6 90.2 9.803

78.6 50.5 50.9 78.3 3.736

78.6 37.4 45.1 72.7 2.189

AHI >30 Sensitivity% Specificity% PPV% NPV% Odds ratio

79.5 48.6 30.4 89.3 3.656

100 37.0 31.0 100 >999.999

87.2 46.4 31.5 92.8 5.881

87.2 36.2 27.9 90.9 3.862

Data are presented as mean. Abbreviations: AHI, apnea-hypopnea index; ASA, American Society of Anesthesiologists; NPV, negative predictive value; PPV, positive predictive value.

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APPENDIX 4. ASA Checklist Category 1 Predisposing Physical Characteristics a. BMI 35 kg/m2 b. Neck circumference 43 cm/17 inches (men) or 40 cm/16 inches (women) c. Craniofacial abnormalities affecting the airway d. Anatomical nasal obstruction e. Tonsils nearly touching or touching the midline Category 2 History of Apparent Airway Obstruction during Sleep Two or more of the following are present (if patient lives alone or sleep is not observed by another person, then only one of the following need be present): a. Snoring (loud enough to be heard through closed door) b. Frequent snoring c. Observed pauses in breathing during sleep d. Awakens from sleep with choking sensation e. Frequent arousals from sleep Category 3 Somnolence One or more of the following are present: a. Frequent somnolence or fatigue despite adequate “sleep” b. Falls asleep easily in a non-stimulating environment (e.g., watching TV, reading, riding in or driving a car) despite adequate “sleep” c. [Parent or teacher comments that child appears sleepy during the day, is easily distracted, is overly aggressive, or has difficulty concentrating]* d. [Child often difficult to arouse at usual awakening time] Scoring: If two or more items in category 1 are positive, category 1 is positive. If two or more items in category 2 are positive, category 2 is positive. If one or more items in category 3 are positive, category 3 is positive. High risk of OSA: two or more categories scored as positive Low risk of OSA: only one or no category scored as positive * Items in brackets refer to pediatric patients. (Modified with permission from Gross JB, Bachenberg KL, Benumof JL, et al. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology 2006;104:1081-1093)

on ventilatory control and upper airway muscle tone, particularly during the early postoperative period [43]. In addition, there are theories that sleep disturbances, including sleep deprivation and fragmentation as well as rebound increases in rapid eye movement sleep during the later postoperative period, may have additional adverse effects on the cardiorespiratory system [21,44,45]. There is only one retrospective case–control study in OSA surgical patients: Gupta et al [46] found an increased incidence of postoperative complications, an elevated rate of transfers

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to the intensive care unit (ICU), and prolongation of the length of hospital stays in patients with OSA versus control patients matched for age, sex and BMI. Receiving continuous positive airflow pressure (CPAP) therapy prior to surgery appeared to reduce the rate of serious complications and shorten the average length of hospital stay by one day. Undiagnosed OSA may pose a variety of problems for anesthesiologists. A number of case reports have documented an increase in the incidence of postoperative complications and deaths among patients suspected of having OSA [47]. Untreated OSA patients are known to have a higher incidence of difficult intubation, postoperative complications, increased ICU admissions, and greater duration of hospital stay [36,46,48]. Identifying patients with OSA is the first step in preventing postoperative complications due to OSA. The STOP questionnaire is a concise and easy-to-use screening tool to identify patients with a high risk of OSA. Incorporating BMI, age, neck size, and gender (STOP-Bang) into the STOP questionnaire will further increase the questionnaire’s sensitivity and NPV, especially for patients with moderate to severe OSA. In our study, the patients with OSA had an increased rate of postoperative complications: respiratory, cardiac or ICU admission. Having an AHI >5 or being identified as having a high risk of OSA by the STOP-Bang questionnaire significantly increased the risk of postoperative complications [36]. Therefore, preoperative screening of patients by using the STOP questionnaire or STOPBang can be very helpful in predicting high-risk patients preoperatively in order to manage them in the best possible way perioperatively.

CONCLUSION There is a high prevalence of undiagnosed OSA in the general population. OSA has a negative impact on the quality of life, as well as an increased incidence of mortality and morbidity. The diagnosis of OSA is established by an overnight sleep study including polysomnography. The STOP questionnaire is a concise and easy-to-use screening tool to identify patients with a high risk of OSA. It has been validated in surgical patients at preoperative clinics as a screening tool. Incorporating BMI, age, neck size, and gender into the STOP questionnaire (STOPBang) further increases the questionnaire’s sensitivity and NPV, especially for patients with moderate to severe OSA. The STOP questionnaire is short—only 4 questions with a yes-or-no format—and should be incorporated into routine screening of general and surgical populations.

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