Disclaimer. Disclosure 3/1/2014. Dennis Spence, PhD, CRNA

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1 Dennis Spence, PhD, CRNA RE Disclaimer The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences, or the United States Government. The author does not endorse, promote or advertise any products presented in this presentation. Disclosure Nothing to disclose 1

2 Objectives Review the stages of sleep Describe types of sleep disordered breathing with focus on OSA Compare and contrast the normal and OSA airway Describe the pathophysiology and clinical consequences of OSA Review evidence on OSA related to: Opioid effects Screening Difficult airway PACU & Postoperative Complications List perioperative precautions that may reduce risks in OSA patients Clinical Vignette 56 y/o male scheduled for ex lap for sigmoid resection PMH-HTN, obesity (BMI 48), DM II, colon cancer PSH- none Meds- HCTZ, metoprolol, glyburide EKG- NSR w/ LAD, LVH Labs- wnl BP- 160/85, HR- 58 Airway- MP III, 3FB MO, TM 2.5 FB, limited ROM, neck 50 cm +snoring, +daytime somnolence, witnessed apnea by wife Clinical Vignette What is the likelihood that this patient has undiagnosed OSA? If he has OSA, how severe is it? What other comorbidities might he have secondary to his OSA? Is he a potentially difficult airway? Does having OSA increase his risks for perioperative complications? What perioperative OSA precautions can I use to minimize his risks? 2

3 Stages of Sleep Non-REM (non-rapid eye mvt) 3 stages Stage 3 physically restorative sleep Stage 3 reduced muscle tone REM Most muscles paralyzed/relaxed Potential collapse of upper airway Lack of REM may impair ability to learn complex tasks Sleep impairment interferes w/ growth patterns, memory, healing, & immune response Types of Sleep Disordered Breathing Apnea Cessation of airflow > 10 seconds Hypopnea Decreased airflow >30% for > 10 seconds associated with: Oxyhemoglobin desaturation 4% Arousals Apnea Patterns Obstructive Mixed Central Airflow Respiratory effort American Academy of Sleep Medicine. Sleep Apnea: Diagnosis and Treatment Sleep Medicine Professional Education slides

4 OSA Definition Characterized chronic, frequent events of airway obstruction during sleep Sxs: snoring, witnessed apnea, & daytime sleepiness Secondary HTN During sleep OSA patients experience: Frequent episodes of apnea and/or hypopnea Frequent oxygen desaturation Chronic hypercarbia and hypoxemia Frequent Arousals Reduced Non-REM Stage 3 & REM sleep OSA Risk Factors Male gender Obesity (BMI>29) present in 60-90% of OSA pts Non-obese craniofacial & orofacial abnormalities (i.e, enlarged tonsils) Family hx Large neck circumference (>17 in male, >16 in female) Smoking and alcohol use Medications-sedatives, opioids Measures of Sleep Apnea Frequency Polysomnography Gold standard for diagnosis of OSA Apnea Index # apneas per hour of sleep Apnea / Hypopnea Index (AHI) # apneas + hypopneas per hour of sleep Oxygen desaturation index (ODI) Number of desaturations of 4% per hour of sleep ODI of >5 high likelihood of OSA 4

5 Severity of OSA AHI None 0-5 Mild 6-15 Moderate Severe >30 Obstructive Apnea EEG Airflow Arousal Effort (Rib Cage) Effort (Abdomen) Effort (Pes) SaO 2 10 sec American Academy of Sleep Medicine. Sleep Apnea: Diagnosis and Treatment Sleep Medicine Professional Education slides Normal Airway Retropalatal (RP) from the level of the hard palate to the caudal margin of the soft palate Retroglossal (RG) from the caudal margin of the soft palate to the base of the epiglottis Schwab et al. Am J Respir Crit Care Med ;

6 OSA Airway Decreased pharyngeal area 2 nd excess adipose tissue Uvula, tonsillar pillars, tongue, lateral pharyngeal walls MRI study- Large tongue and increased volume of lateral pharyngeal walls risk factors for OSA Increased extramural pressure compresses airway (i.e., large neck) Schwab et al. Am J Respir Crit Care Med ; OSA Airway OSA Normal Schwab et al. Am J Respir Crit Care Med ; Normal vs. OSA Airway smaller airway Larger Schwab et al. Am J Respir Crit Care Med ;

7 OSA Airway OSA = airway smaller & lateral pharyngeal walls larger Schwab et al. Am J Respir Crit Care Med ; RE OSA Airway During Sleep Spence DL. Anesthesia for Uvulipharyngopalatoplasty. In Clinical Cases in Nurse Anesthesia, Ed.: Elisha, S. Jones and Bartlett; Sudbury, MA. 2010: pp

8 Vicious Cycle of OSA Sleep Onset Loss of neuromuscular compensation + Decreased pharyngeal muscle activity Airway collapses Hyperventilate: correct hypoxia & hypercapnia Airway opens Pharyngeal muscle activity restored Apnea Arousal from sleep Hypoxia & Hypercapnia Increased ventilatory effort American Academy of Sleep Medicine. Sleep Apnea: Diagnosis and Treatment Sleep Medicine Professional Education slides Clinical Consequences Moos DD, Prasch M, Cantral DE, Huls B, Cuddeford JD. Are patients with obstructive sleep apnea syndrome appropriate candidates for the ambulatory surgical center? AANA J. 2005;73(3): Co-existing diseases/symptoms associated with OSA Cardiovascular Neuropsychological Endocrine/Other Hypertension Arrhythmias: o Atrial Fibrillation o Bradycardia o A-V Block CAD Nocturnal angina MI CHF CVD Pulmonary HTN Daytime somnolence Glucose Intolerance and Diabetes Cognitive Obesity Impairment Gastroesphogeal Reflux Accident proneness Disease Anxiety Difficult airway Depression Adapted from Spence DL. Anesthesia for Uvulipharyngopalatoplasty. In Clinical Cases in Nurse Anesthesia, Ed.: Elisha, S. Jones and Bartlett; Sudbury, MA. 2010: pp

9 percentage of patients (%) 3/1/ OSA Prevalence Wisconsin Sleep Cohort Study 82% 93% Men Women % 2% 0 Prevalence 24% AHI >5 9% Mod-Sev Undx OSA Adapted from Young T et al. N Engl J Med 1993;328. How Well Do We Do? Screening Surgical Patients for OSA Polysomnography considered gold standard Problem- difficult to obtain; expensive Allows for initiation of CPAP therapy Questionnaire screening tools ASA OSA checklist Berlin Questionnaire STOP-BANG Combination of questionnaire + home sleep study 9

10 ASA Checklist Screens & estimates risk (12 items) High-risk = (+) 2 more categories Invasiveness of surgery Postop opioid requirements AHI 5 Sensitivity = 72% Specificity = 38% AHI 15 Sensitivity = 79% Specificity = 37% Abrishami et al. A systematic review of screening questionnaires for obstructive sleep apnea Can J Anesth (2010) 57: Berlin Questionnaire Most widely used in primary care 11 questions in 3 categories Obstructive sxs Daytime sleepiness HTN hx AHI 5 Sensitivity = 69% Specificity = 56% AHI 15 Sensitivity = 79% Specificity = 51% Abrishami et al. A systematic review of screening questionnaires for obstructive sleep apnea Can J Anesth (2010) 57: STOP-BANG Questionnaire 8 item screening tool for surgical patients 3 high risk OSA AHI 5 Sensitivity = 84% Specificity = 56% AHI 15 Sensitivity = 93% Specificity = 43% Chung et al. STOP questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology 2008;108:

11 STOP-BANG Does a higher score predict more severe OSA? N = 746 STOP-BANG = 5 were 10x more likely to have Sev OSA vs. score <3 Score of 5 = Specificity 74% for Sev OSA Table 1. Odds of OSA based on STOP-Bang Score STOP-Bang score All OSA (AHI>5) Mod/Sev OSA (AHI>15) Severe OSA (AHI >30) ( ) 4.75 ( ) ( ) ( ) 6.29 ( ) ( ) 7 or ( ) 6.88 ( ) ( ) Chung et al. High STOP-BANG score indicates a high probability of obstructive sleep apnea Br J Anaesth 2012;108: Does STOP-BANG Predict Postop Complications? Vasu et al 2010 N = 135 surgical patients STOP-BANG score 3 vs. 3 Outcomes = composite postop complications Afib, hypotension, MI, hypoxemia, PE, pneumonia Results for STOP-BANG 3 Odds: 11.4x more postoperative complications (P = 0.03) Vasu TS et al Arch Otolarynglol Head Neck Surg; 2010;136(10): How Common is OSA in Surgical Patients? Finkel et al (2008) N = 2778 surgical pts OSA screening questionnaire High-risk pts sleep study Compared high vs. low risk Results OSA prevalence = 22% 82% never diagnosed High-risk = >BMI, >Neck circ., >HTN, >DM Home Sleep Study Results (n = 207) Finkel et al. Sleep Medicine. 2009;10: Spence DL. Anesthesia Abstracts 2011;(5)9:

12 percentage of patients (%) percentage of patients (%) 3/1/2014 How Common is OSA is Surgical Patients? STOP-BANG study N = 2721 surgical patients STOP-BANG + sleep study Results High-risk ( 3)= 28% Sleep Study Results N = OSA Incidence (AHI >5) Mild OSA (AHI >5) Moderate OSA (AHI >15) Severe OSA (AHI >30) Chung et al. Anesthesiology 2008;108: Spence DL. Anesthesia Abstracts 2011;(5)9: How Common is OSA is GI Patients? ERCP OSA Study N = 231 ERCP patients Used STOP-BANG Results High-risk ( 3)= 43% >MP score, >ASA class, >age, >BMI, >male gender Coté GA et al. Clin Gastroenterol Hepatol 2010;8: EBP STOP-BANG Projects Does incorporation of the STOP-BANG increase our ability to identify patients at high risk for OSA? Method Baseline: measure incidence of high risk OSA Educated nurses & implemented STOP-BANG Post: measured incidence of high risk OSA (score 3) High-risk for OSA Lakdawala (2011) Williams et al (2012) 10 0 Before After Before After Lakdawala L. J Perianesthesia Nurs (1): Williams et al Presented at AANA State of Science Aug

13 Challenges with Screening Incorporated into EMR & preop workflow Auto-calculated score Score 5 to flag as high risk 8 months = 12,500 necks measured Implementing auto-sleep study referral not possible Altering medical assistant and nurse practitioner workflows in the clinic was straightforward. but changing our anesthesia providers workflow has not yet been successful. While some of the variables can be derived from demographics and patient history,... obtaining neck circumference measurements and asking the additional screening questions adds extra time.. JC Screen patients for respiratory depression risk factors (see sidebar). Robert Stoelting, MD, President, Anesthesia Patient Safety Foundation: Clinically significant drug-induced respiratory depression (oxygenation and/or ventilation) in the postoperative period remains a serious patient safety risk that continues to be associated with significant morbidity and mortality. Preoperative Implications OSA prevalence 22-43% >80% of patients have OSA and don t know it Have high index of suspicion for coexisting diseases HTN, CAD, DM, atrial fibrillation Difficult airway Should develop screening process for undiagnosed OSA Polysomnography & initiation of CPAP when possible Use the STOP-BANG Requires multidisciplinary team, buy-in & support at all levels 13

14 Society of Anesthesia & Sleep Medicine, Volume 3, Issue 1 w 2014 Anesthesia Providers could potentially impact a significant public health burden and reduce the percentage of undiagnosed OSA patients in major ways: proper implementation of screening guidelines, optimization of interventional therapy (e.g., CPAP) perioperatively and ensuring follow up by sleep physician postoperatively Our Role does not stop within the confines of the operating room or the PACU. Specialist sleep physician referral and appropriate therapy are crucial in long term cardiac and cerebrovascular outcomes. Opioids & OSA OSA sleep study (N = 19 moderate OSA, AHI>15-30) Continuous remifentanil infusion in sleep lab Results Only 20% experienced REM sleep (P < 0.05) Increased # arousals vs. baseline study AHI increased (44 ± 29 vs. 24 ± 5, P = NS) #obstructive apneas lower(4 ± 6 vs. 8 ± 5, P = NS) #hypopneas increased (22 ± 16 vs. 15 ± 6, P = NS) #Central apneas increased (17 ± 29 vs., 0.4 ± 1 P < 0.05) Bernards CM et al. Anesthesiology 2009;110: Opioids & OSA Lowest SaO2= Baseline = 87 ± 4% Remifentanil = 80 ± 5% P< 0.05 Bernards CM et al. Anesthesiology 2009;110: Spence DL. Anesthesia Abstracts 2011;(5)9:

15 Opioids & OSA Opioids reduce REM sleep decreases # of obstructive apneas REM sleep is when airway most relaxed # central apneas may increase (no stimulus to breathe) REM rebounds in 48-72hrs worsening of OSA sxs* Hypoxemia & hypercarbia may have triggered increased # arousals & reduced obstructions Hypoxemia incidence and severity worse on remifentanil Implication Be cautious when administering opioids to OSA patients *Lao P, Sun F, Amirshahi B, Islam S, Vairavanathan S, Shapiro C, Chung F. A significant exacerbation of sleep breathing is OSA patients undergoing surgery with general anesthesia. Sleep 2009;32: A223. OSA & Difficult Airway Are Patients with OSA more Difficult to Ventilate? Predictors of Impossible Mask Ventilation Neck radiation changes 7.1 Male sex 3.3 Sleep apnea 2.4 MP III or IV 2 Beard 2 Odds ratio Patients with 3 of these risk factors were 8.9x more likely to be impossible to mask ventilate Kheterpal S et al Prediction and Outcomes of Impossible Mask Ventilation: A Review of 50,000 Anesthetics. Anesthesiology. 110(4): , April

16 Are Patients with OSA more Difficult to Intubate? Palatal muscle resection for OSA (N = 115) (Lee et al 2011) 20% difficult intubation (DI) rate Predictors Large neck 40 cm AHI 50 UPPP (N = 180) (Kim et al 2006) OSA vs. no OSA DI rate: 16.6% vs. 3.3% Spence DL. Anesthesia Abstracts 2011;(5)9: OSA & Difficult Intubations Bariatric Surgery observational study (N = 180) 78% female, BMI = 49.4 ± 7.6, median OSA severity = mild Median MP score = MP 2, neck circumference = 43.8 ± 5.4 cm Results DI rate = 3.3% No relationship between OSA dx and difficult intubation in bariatric pts(p = NS) Predictors of DI = >MP 2 & male gender Larger neck = poorer glottic view Meligan et al Anesth Analg 2009;109: Implications Men with severe OSA & large necks at greatest risk Airway surgery for OSA may be risk Be prepared for difficult mask and intubation! Ramp obese pts & optimize sniffing position Backup device (indirect video laryngoscopy, LMA) Call for help early! Consider AFOB 16

17 Sedation & OSA Cohort study N = 231 High-risk OSA 1.6x more likely ERCP/EUS to experience SAO2<90% High vs. Low risk OSA (STOP-BANG) CRNA = propofol +/- opioid/midazolam Outcomes = Airway maneuvers sedation related complications Coté GA et al Clin Gastroenterol Hepatol 2010;8: Spence DL. Anesthesia Abstracts 2011;(5)9: PACU & Suspected OSA Cohort study N = 693 surgical Non-OSA dx patients High vs. Low-Risk OSA Outcome = recurrent PACU respiratory complications <90% with nasal cannula; 3 episodes needed for yes Results 32% high-risk for OSA >1 event of SaO2 <90% = 28% vs. 11%, P < High-risk OSA = 3.5x more likely postop resp. event 21x more likely experience recurrent PACU events 2.7x more likely experience postop complication Unplanned ICU admission = 27% vs. 8% Gali et al. Anesthesiology 2009;110: PACU & Suspected OSA High-risk OSA = more likely to experience recurrent desaturation Gali et al. Anesthesiology 2009;110: Spence DL. Anesthesia Abstracts 2011;(5)9:

18 Implications- PACU Desaturation most common complication What about hypercarbia? Points to need to have plan for high-risk OSA pts ICU vs. Step-down unit Question: Should OSA pts have continuous ETCO2 & SaO2 monitoring? Severity? Gali et al. Anesthesiology 2009;110: OSA & Postop Complications Case-control study of TKA surgery pts clinically suspected or diagnosed OSA pts vs. control (N = 202) Respiratory complications = 28% vs. 10%, P = Note. Serious complications were undx defined OSA as vs. complications dx OSA = necessitating transfer to the ICU for cardiac events Total or urgent complications respiratory = support 32% vs. with 3%, need P <0.05 for intubation or CPAP. Gupta et al. Mayo Clin Proc 2001;76: Spence DL. Anesthesia Abstracts 2011;(5)9:. OSA & Postop Complications N = 240 N = 240 Liao P et al. Postoperative complications in patients with obstructive sleep apnea: a retrospective matched cohort study. Can J Anesth 2009;56: Spence DL. Anesthesia Abstracts 2011;(5)9. 18

19 OSA & Postop Complications OSA group (N = 240) 2x increased risk of postop complication 27% require CPAP 2 nd hypoxemia Complications occurred more often after transfer to ward CV & neuro complications same 2 vs. 1 cardiac arrests in OSA pts 2 for difficult intubation/reintubation Liao P et al. Postoperative complications in patients with obstructive sleep apnea: a retrospective matched cohort study. Can J Anesth 2009;56: OSA & Postop Complications National Inpatient Sample OSA Study N = 3,441, Memtsoudis S et al. Perioperative pulmonary outcomes in patients with sleep apnea after noncardiac surgery. Anesth Analg 2011;112: OSA & Postop Complications National Inpatient Sample OSA Study N = 3,441,262 Table 1. Odds of Postoperative pulmonary complications in OSA patients General surgery Aspiration pneumonia ARDS PE Intubation/mechanical ventilation Orthopedic Aspiration pneumonia ARDS PE Intubation/mechanical ventilation 1.37 ( ) 1.58 ( ) 0.90 ( ) 1.95 ( ) 1.41 ( ) 2.39 ( ) 1.22 ( ) 5.20 ( ) Note. Results are odds ratio (95% confidence interval). All are significant (P < 0.05). 21. Memtsoudis S et al. Perioperative pulmonary outcomes in patients with sleep apnea after noncardiac surgery. Anesth Analg 2011;112:

20 Non-SDB group Higher Hospital charges, $39,977 vs. $37,934, P < Slightly higher mortality 0.3% vs. 0.1%, P Longer LOS 7.1 days vs. 5.8 days, P < 0.01 Why???? Higher vigilance in those dx w/ OSA? Some Non-SDB group could have had undiagnosed OSA? Does Technique Matter? Neuraxial anesthesia +/- GA associated with improved outcomes Reduced odds of major complications, requirement for critical care admission (especially for neuraxial anesthesia alone), or mechanical ventilation Associated with reduced hospital length of stay and costs. Randomized N = 177 OSA patients (AHI>15) to auto-titrated CPAP started 3 days prior to surgery or routine care CPAP significantly reduced postoperative AHI Low compliance <48% of patients used the CPAP >4h per night 20

21 CPAP adherence in patients with newly diagnosed obstructive sleep apnea prior to elective surgery. Guralnick AS, Pant M, Minhaj M, Sweitzer BJ, Mokhlesi B. Methods: Pre-surgical patients who screened positive for OSA on the STOP-Bang questionnaire and underwent PSG before surgery. CPAP was offered to patients with moderate or severe OSA. Results: Median Adherence only 2.5 h/n Conclusion: Adherence to prescribed CPAP therapy during the perioperative period was extremely low. J Clin Sleep Med Oct 15;8(5):501-6 Postoperative Implications Known or suspected OSA patients increased risk for postoperative pulmonary/respiratory complications Hypoxemia Need for higher level of care CPAP improves postop AHI, but compliance poor Neuraxial improved outcomes reduced costs Mod-Sev OSA may need continuous ETCO2 +/- SPO2 Smart Pump Technology Patient Surveillance systems OSA During Pregnancy Home sleep study N = 161 obese w BMI > 30 kg/m 2 AHI >5 vs. AHI <5 Outcomes Perinatal outcomes Predictors of preeclampsia controlled for BMI, age, diabetes Results OSA incidence = 15% Age 30±6 vs. 27±6 (P = 0.04) Prepregnancy BMI 48±11 vs. 39±6 (P <0.001) CHTN 58% vs. 33% (P = 0.02) Asthma 50% vs. 31% (P = 0.005) Louis J et al. Perinatal Outcomes Associated With Obstructive Sleep Apnea in Obese Pregnant Women. Obstet Gynecol 2012;120:

22 percentage of patients (%) 3/1/2014 OSA during Pregnancy Predictors of preeclampsia 3.5x more likely w/ OSA 2.8x more likely w/ previous preeclampsia 4.3x more likely w/chtn Cesarean Delivery Preeclampsia Wound Complications NICU Admission Hyperbilirubinemia All P < OSA No OSA Perioperative OSA Precautions Need to ID those with known or suspected OSA (especially moderate-severe) Minimize preoperative sedation Prepare for possible difficult airway Minimize use of long acting opioids. Consider utilizing multimodal analgesic techniques and regional anesthesia when possible Utilize short acting inhaled or intravenous anesthetics intraoperatively Utilize capnography during monitored anesthetic care Ensure patient is full reversal of neuromuscular blockade. Ensure patient is fully conscious and cooperative prior to extubation Utilize non-supine posture for extubation and recovery Resume or consider use of CPAP therapy in patients with OSA Have plan for postop monitoring. Consider continuous ETCO2 +/- SPO2 Seet E, Chung F. Management of sleep apnea in adults- functional algorithms for the perioperative period: continuing professional development. Can J Anesth. 2010;57: Society of Ambulatory Anesthesia Consensus Guidelines 2012 Recommend screening with STOP-BANG & presume patient has OSA based on sxs Literature unclear of benefit of sleep study or CPAP on postop outcomes Non-optimzed patients may not be suitable for ambulatory surgery Optimal duration of CPAP therapy prior to surgery unknown Recommend nonopioid analgesic/multimodal techniques especially for painful ambulatory surgery Encourage patients w/ OSA to use CPAP postop whenever sleep Educate surgeons, patient and family on minimizing opioids, use of CPAP, and sleeping in lateral position Patients should f/u with primary care MD for sleep study postop if identified as high risk for OSA based on STOP-BANG Joshi et al. Anesthesia & Analgesia. 115(5): , November

23 Joshi et al. Anesthesia & Analgesia. 115(5): , November References 1. American Academy of Sleep Medicine. Sleep Apnea: Diagnosis and Treatment Sleep Medicine Professional Education slides Chung SA, Yuan H, Chung F. A systemic review of obstructive sleep apnea and its implications for anesthesiologists. Anesth Analg. 2008;107(5): Spence DL. Anesthesia for Uvulipharyngopalatoplasty. In Clinical Cases in Nurse Anesthesia, Ed.: Elisha, S. Jones and Bartlett; Sudbury, MA. 2010: pp Schwab et al. Identification of upper airway anatomic risk factors for obstructive sleep apnea with volumetric magnetic resonance imaging. Am J Respir Crit Care Med ; Horner RL. Respiratory motor activity: influence of neuromodulators and implications for sleep disordered breathing. Can J Physiol Pharmacol 2007;85: Metzner J, Posner KL, Domino KB. The risk and safety of anesthesia at remote locations: the US closed claims analysis. Curr Opin Anesthesiol 2009;22: Chung F, Yegnesaran B, Liao P et al. Validation of the Berlin Questionnaire and American Society of Anesthesiologists Checklist as screening tools for obstructive sleep apnea in surgical patients. Anesthesiology 2008;108: Chung F et al. STOP questionnaire: a tool to screen patients for obstructive sleep apnea. Anesthesiology 2008;108: Lakdawala L. Creating a safer perioperative environment with an obstructive sleep apnea screening tool. J Perianesthesia Nurs (1):

24 References 10. Bernards CM, Knowlton SL, Schmidt DF, DePaso WJ, Lee MK, McDonald SB, Bains OS. Respiratory and sleep effects of remifentanil in volunteers with moderate obstructive sleep apnea. Anesthesiology 2009;110: Chung et al. High STOP-BANG score indicates a high probability of obstructive sleep apnea Br J Anaesth 2012;108: Finkel et al. Prevalence of undiagnosed obstructive sleep apnea among adult surgical patients in an academic medical center. Sleep Medicine. 2009;10: Gross 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: Coté GA, Hovis CE, Waldbaum L et al. A screening instrument for sleep apnea predicts airway maneuvers in patients undergoing advanced endoscopic procedures. Clin Gastroenterol Hepatol 2010;8: Kheterpal S, Martin L, Shanks AM, Tremper KK. Prediction and outcomes of impossible mask ventilation: review of 50,000 anesthetics. Anesthesiology 2009;110: Lee SJ, Lee JM, Kim TS, Park YC. The relationship between the predictors of obstructive sleep apnea and difficult intubation. Korean J Anesthesiol 2011;60: References 17. Kim JA, Lee JJ. Preoperative predictors of difficult intubation in patients with obstructive sleep apnea syndrome. Can J Anesth 2006;53: Meligan PJ, Porter S, Max B, Malhotra G, Greenblatt EP, Ochroch EA. Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients. Anesth Analg 2009;109: Moos DD, Prasch M, Cantral DE, Huls B, Cuddeford JD. Are patients with obstructive sleep apnea syndrome appropriate candidates for the ambulatory surgical center? AANA J. 2005;73(3): Rao SL, Kunselman AR, Schuler GH, DesHarnais S. Laryngoscopy and tracheal intubation in the head-elevated position in obese patients: a randomized, controlled, equivalence trial. Anesth Analg 2008;107: Memtsoudis S et al. Perioperative pulmonary outcomes in patients with sleep apnea after noncardiac surgery. Anesth Analg 2011;112: Vasu TS, Dogharmji K, Cavallazzi R et al. Obstructive sleep apnea syndrome and postoperative complications: clinical use of the STOP-BANG questionnaire. Arch Otolaryngol Head Neck Surg 2010;136: Gali B, Whalen FX, Schroeder DR, Gay PC, Plevak DJ. Identification of patients at risk for postoperative respiratory complications using a preoperative obstructive sleep apnea screening tool and postanesthesia assessment. Anesthesiology 2009;110: Gupta RM, Parvizi J, Hanssen AD, Gay P. Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: a case-control study. Mayo Clin Proc 2001;76: Seet E, Chung F. Management of sleep apnea in adults- functional algorithms for the perioperative period: continuing professional development. Can J Anesth. 2010;57: References 26. Lao P, Sun F, Amirshahi B, Islam S, Vairavanathan S, Shapiro C, Chung F. A significant exacerbation of sleep breathing is OSA patients undergoing surgery with general anesthesia. Sleep 2009;32: A Liao P et al. Postoperative complications in patients with obstructive sleep apnea: a retrospective matched cohort study. Can J Anesth 2009;56: Joshi et al. Society for Ambulatory Anesthesia Consensus Statement on Preoperative Selection of Adult Patients with Obstructive Sleep Apnea Scheduled for Ambulatory Surgery. Anesth Analg (5): Louis J et al. Perinatal Outcomes Associated With Obstructive Sleep Apnea in Obese Pregnant Women. Obstet Gynecol 2012;120: