Week 7 - Obstructive Sleep Apnea Flashcards
Obstructive Sleep Apnea vs Central Sleep Apnea
Obstructive: Abnormal breathing during sleep due to anatomical disorder of the pharynx (Loss of pharyngeal muscle tone during sleep)
-cessation of breathing for >10 seconds despite continued ventilatory efforts
Central: Abnormal breathing due to interruption in central respiratory drive – results in episodic cessation of breathing during sleep
-Cheyne stokes respirations, CHF
What is obstructive hypopnea?
More than 50% reduced airflow for >10 seconds
How do you determine the severity of OSA?
Apnea/Hypopnea Index (AHI)
-frequency of apnea and hypopnea events per hour
Mild = AHI 6-15 Moderate = AHI 16-25 Severe = AHI >25
What is the pathophysiology of OSA?
-Loss of upper airway muscle tone during REM sleep (increased pharyngeal resistance)
-Negative pharyngeal pressures during inspiration – collapse of the upper airway and apnea
(leads to hypoxemia and hypercarbia)
*sympathetic hyperactivity and frequent arousal from sleep which restores muscle tone and resumption of airflow
What comorbidities can OSA lead to?
Frequent Arousals –> Sleep Disruption –> Excessive Daytime Somnolence –> Impaired Concentration/Memory
O2 desaturation and sympathetic hyperactivity and systemic inflammatory response leads to CV morbidities: HTN, Arrhythmias, MI, CHF, Pulmonary HTN
What are anatomic/neural factors that lead to OSA?
- Skeletal deformities (retrognathia)
- Large tongue size
- Masses (tonsil/adenoid hypertrophy)
- Chronic airway inflammation (smoking)
- Obesity
- Pharyngeal closing pressure in OSA pt’s is greater than atm pressure
- Pharyngeal relaxation and collapse during REM sleep (generalized loss of SM tone)
- Trauma to upper airway mucosa due to repetitive collapse –> diminished neural sensory capability
- Vicious cycle (OSA makes OSA worse)
What are the two types of obesity?
Android - central obesity, located in the upper body
-associated with increased O2 consumption and cardiac disease
Gynecoid - peripheral obesity, located in the hips, buttocks and thighs
-less likely associated with CV disease
What is Polysomnography?
Gold standard in diagnosis of OSA
- consists of EEG, electrooculogram, and submental electromyogram for staging sleep apnea
- oral and nasal airflow and respiratory efforts, oximetry, systemic blood pressure, ECG and capnography are also monitored
What is the gold standard screening tool for OSA?
STOP-BANG
Snoring Tiredness (daytime) Observe Apnea Pressure (HTN?) BMI >35 Age >50 Neck Circumference >40cm Gender (male)
What are CV/Pulmonary complications of OSA?
- HTN
- Arrhythmias
- Atherosclerosis
- MI
- CHF
- Biventricular failure
- Respiratory failure
- Pulmonary HTN
- Cor PUlmonale
What are endocrine complications of OSA?
Insulin resistance
Type II DM
Leptin resistance –> Metabolic Syndrome –> Obesity
What are neurological complications of OSA?
- Daytime hyper somnolence
- Impaired concentration
- CVA
- Neurocognitive dysfunction
- Idiopathic intracranial HTN
- Spontaneous CSF leaks
What is idiopathic intracranial HTN related to OSA?
Increased ICP preceding/during/after apneic episodes
Increased ICP in OSA patients during wakeful states (particularly in AM – severe headaches)
What are treatment options for OSA?
CPAP = gold standard therapy – provides excellent symptom control and reduces OSA associated complications
Intraoral Devices: useful for mild to moderate OSA – mandibular repositioning devices, tongue restraining devices, good symptom control
Surgical Treatment: tonsillectomy, tissue debulking procedure (purpose is to create more open airway so obstructions are less likely
What are perioperative implications of OSA?
- Sleep disruptions from surgery (diminished sleep quality and quantity preop)
- Increased sensitivity to sedatives and opioids (reduced response to hypoxia and hypercarbia)
- Increased PACU, ICU, and hospital length of stay
- More unplanned admissions
- Increased overall complications
What are local and regional anesthesia intraoperative considerations of OSA?
Local and regional anesthesia may be preferred
- may be tricky due to anatomic considerations of patient (able to lay flat for extended period of time?)
- may not require airway manipulation
- reduces intraop sedatives and opioids? (risk of benzos/sedatives in non-secure airway
- cpap should be utilized if possible
- if deep sedation is likely, GA should be utilized (airway should be secured)
What are general anesthesia intraoperative considerations of OSA?
- Optimal technique would allow for rapid recovery and early, full return of protective airway reflexes and allow maintenance of patent airway
- No evidence to support TIVA better than inhalational gas
- Hyperventilation during mechanical ventilation should be avoided – metabolic alkalosis – postop hypoventilation
- Secure airway (RSI, premedicate with Na Citrate, Reglan, Pepcid)
- OG/NG Tube
- Limit long active opioids until awake
What are airway considerations during anesthesia for a pt with OSA?
- Often reported to present with difficult tracheal intubation – short, thick neck, large neck circumference, AHI >40 and limited mandibular protrusion
- Obesity – difficult face mask ventilation, MP III or IV
- OSA = independent risk factor for difficult intubation (25% of pts need advanced airway techniques)
- Positioning is critical (utilize ramping)
- Plan for difficult airway
- Have help available
- Preoxygenation with 100% O2 – 10cm H2O CPAP for 3-5 min with HOB elevated to 25-30 degrees
What are emergence considerations for pts with OSA?
Use caution with extubation
- awake and alert (deep extubation not advised!)
- reversal of muscle relaxants
- positive leak test prior to extubation
- utilize tube exchanger
- have airway devices on standby
- oral/nasal airway
- extubate in semi upright (>30 degree head up) position whenever possible
CPAP immediately postop
