OSAS Flashcards
What % of patients with OSAS have systemic hypertension
0.4
What level of oxygen desaturation is associated with a significantly higher incidence of PVCs
0.5
What is the respiratory arousal index
apneas + hypopneas + RERAs per hour.
What is the RDI in patients with severe OSAS
>30 events per hour.
What is the relative risk for sleep-disordered breathing in a patient with allergic rhinitis
1.8.
How far is the genioglossus normally moved with the genioglossus advancement (GA)
10 - 14 mm.
What are the normal dimensions of the osteotomy in GA
10 x 20 mm.
What % of patients with OSAS will be considered difficult to intubate
19%.
What proportion of patients with OSAS are obese
2/3.
What is the prevalence of obstructive sleep apnea syndrome (OSAS)
24% of adult men and 9% of adult women; about 30 million people in the US.
What is the minimal mandibular height necessary for performing GA
25 mm.
What is the prevalence of behavioral and emotional problems in children undergoing tonsillectomy and adenoidectomy for treatment of sleep-disordered breathing
25%.
When should PSG be performed after surgery for OSAS
6 months after surgery.
What is the incidence of postoperative hypertension in patients with OSAS without history of hypertension
63%.
What is the cure rate for OSAS in patients with RDI
77% (Riley and Powell).
How far from the inferior border of the mandible should the osteotomy be placed
8 - 10 mm.
What % of cases of anesthesia of the chin/lip after GA will resolve by 6 months
95%.
What is the definition of a hypopneic episode
A 50% or more decrease in flow with a drop in oxygen saturation of 4°/o or more.
What is the Bernoulli principle
A column of air flowing through a conduit produces a partial vacuum or negative pressure at the margins of the column that increases as the rate of flow increases.
What is the normal thickness of the soft palate in adults
About 12 mm; gets thinner laterally.
How is an arousal defined during PSG
Abrupt shift in EEG frequency consisting of an alpha wave, theta wave or wave with frequency > 16 Hz, excluding spindle waves; must be preceded by at least I 0 seconds of sleep, must last at least 3 seconds, and must be accompanied by increase in chin EMG.
What preoperative factor is associated with a positive long-term response to UPPP
AHI
What is an RERA (respiratory effort related arousal)
An arousal related to an obstructive respiratory event other than apnea or hypopnea (ie, esophageal pressure crescendo, snoring, increased diaphragm EMG, or increased nasal resistance).
What is the AHI
Apnea-hypopnea index or # apneic and hypopneic events per hour.
Neurocognitive dysfunction is most related to which two measurements on PSG
Arousal index and hypoxemia.
Where is dehiscence most likely to occur after UPPP
At the inferior tonsillar poles.
What is the ideal MAP after surgery for OSAS
Below 100 mm Hg.
What factors are associated with an increased risk of base of tongue obstruction
BMI >31, mandibular skeletal deficiency, and RDI >40.
What are some adjunctive procedures for patients who do not improve after UPPP
BOT reduction, mandibular advancement with LeFort I osteotomy and maxillary advancement, genioglossus advancement, tracheostomy.
What are the categories of apneic or hypopneic episodes
Central, obstructive, or mixed.
What is the definition of sleep apnea
Cessation of airflow due to obstruction or cessation of respiratory effort during sleep.
What is the definition of an apneic episode
Cessation of airflow for I 0 seconds, usually associated with an arousal and/or desaturation.
What does a standard polysomnography (PSG) record
EEG, EOG, EMG (submentalis and mentalis, anterior tibialis), EKG, oxygen saturation, nasal airflow, rib cage and abdominal respiratory effort.
What preoperative symptom best correlates with improvement in AHI after UPPP
Excess daytime sleepiness.
Increased electrical activity of which muscles has been demonstrated in patients with OSAS while awake
Genioglossus and tensor palatini muscles.
What is the only patient characteristic shown to increase the likelihood of OSAS
High body mass index.
When is clock-dependent alerting most active
In the afternoon.
Why should adenoidectomy be avoided when performing UPPP
Increases the risk of nasopharyngeal stenosis.
What is “clock-dependent alerting”
Internal signal from the biological clock that opposes the tendency to fall asleep.
What are the 4 basic types of polysomnographies
Level I - standard. Level II - comprehensive portable. Level III - modified portable. Level IV - continuous single or dual bioparameter.
What physical features are predictors of difficult intubation in patients with OSAS
Low hyoid (mental protuberance to hyoid distance >30cm), mandibular deficiency, and large neck circumference (>45.6 em).
What are the possible complications of GA
Mandible fracture, dental injury, failure to advance, infection, anesthesia of lower lip, gums, and chin, bleeding/hematoma.
What is considered abnormal negative esophageal pressure (-Pes)
More negative than - 12 mm Hg.
Why is OSAS worse during REM sleep
Muscle relaxation is maximal during REM sleep.
What disease is characterized by a decreased sleep latency time with quick onset of REM sleep on polysomnogram
Narcolepsy.
What are the primary disadvantages of an outpatient study
No EEG to assess total sleep time and no EMG to study periodic limb movements.
What are the most common physical signs associated with OSAS
Obesity, systemic and pulmonary hypertension, erythrocytosis, congestive heart failure, sleep-related arrhythmias, unexplained cognitive/psychiatric disturbances.
What is the success of UPPP for the treatment of OSAS in adults
Overall, 50% experience a 50°/o reduction in AHI or in the amount of oxyhemoglobin desaturation.
What are the general indications for performing tracheostomy on patients with OSAS
Oxygen saturation
What is a split-night study
Patient is studied for the first half of the night then placed on a CPAP machine for the latter half.
What is the primary disadvantage of a split-night study
REM sleep is most concentrated in the final 1/3 of the night; OSAS is worse during REM sleep.
What are the most common symptoms associated with OSAS
Restless sleep, loud snoring, excess daytime sleepiness, decreased intellectual capacity and memory loss, personality changes or depression, decreased libido, morning headaches (in decreasing order of frequency).
What are the advantages of the uvulopalatal flap
Reversible; less pain and less incidence of dehiscence than UPPP.
What is upper airway resistance syndrome (UARS)
Snoring with pathologic daytime sleepiness, poor sleep efficiency, and fragmented sleep; near-normal RDis and oxygen saturations but abnormal negative esophageal pressures.
Where in the brain is the “biological clock”
Suprachiasmatic nuclei.
What is the Venturi effect
The acceleration of flow as a current of air or liquid enters a narrowed passage.
What is the preferred treatment for OSAS in children
Tonsillectomy and adenoidectomy.
What is Fujita’s classification of airway obstruction in patients with OSAS
Type I - palate only (normal base of tongue). Type Il/IIA - palate and base of tongue. Type III/liB - base of tongue only (normal palate).
