Obesity, Sleep Apnea, the Airway, and Anesthesia

1. Obesity, Sleep Apnea, the Airway, and Anesthesia R3 김상영

2. Obstructive Sleep Apnea (OSA) • 4% of men, 2% of women • Obesity : very important independent causative-risk factor (60~90% of OSA, BMI>29㎏/㎡) • Craniofacial and orofacial bony abn., nasal obx., large tonsil : 주로 소아에서 • Excess neck fat • 대부분 진단이 이루어지지 않은채 살고있음 • 마취과 의사가 gatekeeper

3. Definition of OSA Terms • OSA정의 • Cessation of airflow for more than 10 seconds despite continuing ventilatory effort, • 5 or more times per hour of sleep, • usually associated with a decrease in arterial oxygen saturation (SaO₂) of more than 4% • Obstructive sleep hypopnea (OSH) • Decrease in airflow of more than 50% for more than 10 seconds, • 15 or more times per hour of sleep • Usually associated with snoring and may be associated with a decrease in SaO₂of greater than 4%

4. Table 1. Definition of OSA and OSH OSA = obstructive sleep apnea; OSH = obstructive sleep hypopnea

5. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Normal Pharyngeal Muscle Activity • Subatmostheric intraairway pr. • 3 pharyngeal segments • Retropalatal pharynx • Retroglossal pharynx • Retroepiglottic pharynx • Collapsible • Ant. And lat. Walls lack bony support

6. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Fig 1 A

7. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Fig 1 B

8. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Fig 1 C

9. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Normal Sleep • NREM sleep ⇒ REM sleep (4~6cycles) • Generalized loss of m. tone • Deep NREM(stage3,4), REM • Compliant lat. Pharyngeal wall (m/c site) • NREM sleep중의 r. = awake상의 2배 • REM sleep중의 r. > NREM r.

10. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Obesity and OSA: Pharyngeal Pathology and Incidence • Inverse relation between obesity and pahryngeal area • 지방축적부위 : uvula, tonsil, tonsillar pillars, tongue, aryepiglotic folds, lat. Pharygeal walls • 지방축적↑⇒근이완때와 비슷한 효과 ⇒ soft wall이 collapse유발 • Transmural pr.& compliance of the wall • Extraluminal pr.(목살, 목둘레가 중요)

11. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Arousal • 무호흡시에 일어나는 event들 • PaO₂↓ • PaCO₂↑ • Ventilatory effort progressively ↑ • Intraairway pr. Progressively ↑ • Arousal • By reticular activating system • EEG activity↑, vocalization, extremity twitching, gasping or snorting on airway opening • 생존을 위해 필요한 반응

12. Pathopysiology of Obstructive Sleep Apnea in the Adult Obese Patient • Systemic Pathophysiology of OSA • Systemic effects of the sleep→arousal→sleep cycles SLEEP SNORING, NOCTURNAL Primary Event RESTLESSNESS SOCIAL ISOLATION OBSTRUCTED ↓O₂& ↑CO₂ AROUSAL BREATHING DAYTIME SLEEPNESS ARRTHYMIAS PULM. HTN SYSTEMIC HTN PERSONALITY BEHAVIOR CHANGES COGNITION MYOCARDIAL ISCHEMIA RVH LVH ACCIDENT PRONE

13. Diagnosis of OSA • 관련요소들 • Obesity, snoring or apnea during sleep, periodic snorting and apparent arousal, daytime sleepness or fatigue, increased neck circumference

14. Diagnosis of OSA • Obesity • BMI = mass/height²=kg/m²or 703 × lbs/inches² • Underweight(<19), normal(19~24.9), overweight(25~29.9), obesity(30~34.9), morbid obesity(>35) • 지방과 근육 구분이 잘 안되는 단점 • Obstructive vs central sleep apnea • 숨쉬려는 노력 유무에 따라 나뉨

15. Diagnosis of OSA • Fig 3

16. Diagnosis of OSA • Table 2. Understanding the Sleep Study Report SpO₂(oxygen saturation) data are also reported as number of events per 60-69%, 70-79%, 80-89%, and the lowest SpO₂. Electrocardiogram and hemodynamics are usually descriptive and the extremes reported. TV = tidal volume; AHI = apnea-hypopnea index ODI = oxygen desaturation; AI = arousal index

17. Effect of Anesthetic Drugs on Airway Patency in the Adult Obese Patient with OSA • All central depressant drugs ⇒ pharyngeal dilator m. action ↓ • Propofol, thiopental, narcotics, benzodiazepines, small doses of neuraomuscular blockers, nitrous oxide • Opioids • Cause airway obx., poor ventilatory response • Post op pain↑⇒ opioids 사용량↑ ⇒ 위험도↑ • 수술뒤 1주까지는 위험한 기간 (by REM sleep)

18. Implications for Airway Management • Preoperative Evaluation: OSA and Airway Status • 미리 진단된 사람 적다 • 마취과 의사는 gatekeeper • Nocturnal snoring-snorting-apnea, arousals, diurnal sleepness등을 확인 • HTN history, 목둘레 40-42cm이상이면 위험증가 • Nocturnal diaphoresis and enuresis, frequent nocturia, morning headaches, and abnormal cardiovascular and neuropsychiatric function • Regional anesthesia

19. Implications for Airway Management • Tracheal Intubation • 더 어려운 경우 많다 • Obesity, short thick neck, excess pharyngeal tissue • 같은 나이의 환자보다 difficult비율 100배 • Awake? Or under general anesthesia? • Premedication 신중을… • 다른 기구들을 활용 • Ex) flexible fiberscope • Fully preoxygenation • Small FRC(small oxygen reservoir) • High oxygen consumption • Laryngoscopy : optimal manner • Two hand mask나 다른 유사시를 대비. 2인 이상

20. Implications for Airway Management • Fig 4

21. Implications for Airway Management • Extubation : Awake vs Leaving the Tube In • Risk of airway obx. After extubation↑ • Nasal packing시 더 증가 • Life-threatening postextubating obx.: 5% • Negative-pr. Pulm. Edema • Narcotics 과다 사용은 피하라 • Regional anesthesia가 도움되기도 • Reverse Trendelenburg or semiupright positon등 체위이용도 도움 • Two-hand manuver, reintu등 상황에 대비하여 2인 이상 대기 • N-CPAP : SpO₂떨어질때만 O₂분율 높여라

22. Implications for Airway Management • Table 3. Major Determinants of Awake versus Asleep(DEEP) Extubation in Patients with OSA undergoing UPPP or Nasal surgery

23. Implications for Airway Management • Opioid Pain Management : Location of Patient • Opioid-induced upper airway obx. • Moitored-care environment가 필요한 이유 • 고려할 factor들 Table 4. Determinants of Whether Extubated Obese Patients with Sleep Apnea → Ward vs ICU BMI = body mass index; AHI = apnea-hypopnea index BP = blood pressure

24. Implications for Airway Management • Table 5. Extubated Obese Sleep Apnea Patients : Ward vs ICU