Snoring & Obstructive Sleep Apnea Syndrome

Seong-Kyun Kim, M.D. & Jeong-Hoon Oh, M.D.
Comments by Kyung Shik Suh, M.D., June 1, 1998

Snoring : An Overview with Historical Perspectives

Snoring
- the lay term for obstructive breathing during sleep
- one of the most prevalent of obnoxious human habits
- In a 30- to 35-year-old population, 20% of men and 5% of women
- By age 60, 60% of men, and 40% of women
- Old legend "Primitive man defended their women even at night by making terrifying noises to frighten away beasts of prey "
- Three times more common in obese persons than in thin ones
- Most animals do not sleep on their backs, so they do not snore
Some are variations on the old idea of taping a marble on the snorer's back to force him to sleep on his side, since snoring is often worse when the person sleeps supine

Social effects of snoring

The list of complaints expressed by snorers help in our office gives poignant(heart moving) testimony to the hardships that snoring imposes on the lives of snores and their companions.

Pathophysiology of snoring
Snoring is one sign of a number of different disorders.
The sounds of snoring originate in the collapsible part of the airway where there is no rigid support; that is, from the epiglottis to the choanae.
It involves the soft palate, uvula, tonsils, tonsillar pillars, base of tongue, and pharyngeal muscles and mucosa.

Four factors, singly or in combination, contribute to snoring.

1. Incompetent tone of palatal, lingual, and pharyngeal muscles is the cause of most adult-onset snoring. Hypothyroidism also contributes to poor muscle tone, snoring, and apnea, as do neurological disorders such as cerebral palsy, muscular dystrophy, and myasthenia.
2. Space-occupying masses impinging on the airway can contribute to snoring. In children, snoring is almost always from enlarged tonsils and adenoids. One-third of adult snorers also have tonsils large enough to contribute to the airway problem.
3. Excessive length of the soft palate and uvula narrows the nasopharyngeal aperture because the palate descends not only inferiorly in direction, but posteriorly as well.
4. Restriction to airflow in the nose creates increased negative pressure during inspiration which draws together the flaccid tissues in the collapsible part of the airway, where they vibrate and cause snoring.
Nasal or septal deformity, nasal tumor, and sinusitis with nasal polyps are also possible causes of snoring

Apnea and the medical effects of snoring

Heavy snorers are more likely to be hypertensive and to develop angina pectoris than nonsnorers of a similar age and weight.
The most advanced stage of snoring is obstructive sleep apnea, which causes profound cardiac, pulmonary, and behavioral problems. ("Apnea " comes from the Greek term meaning "want of breath.")
Whereas snoring means partial obstruction of the airway, apnea means total obstruction.
It is considered pathological when apnea episodes last over 10 sec and occur over 7 to 10 times per hour (or 30 times per night)
Chronic nocturnal hypoxemia leads to some predictable cardiovascular effects.
Hypoventilation leads to pulmonary hypertension, then to increased cardiac work load and to systemic hypertension in at least 50% of patients.

Obstructive sleep apnea is now recognized as a cause of the Pickwickian syndrome, described as obesity, hypersomnolence , periodic breathing with alveolar hypoventilation and cor pulmonale.
Snoring children with massively enlarged tonsils and adenoids are at risk for significant cardiovascular, developmental , educational, and behavioral consequence of snoring and the sleep apnea syndrome.
Sleepiness in a child is often manifested as hyperactivity or antisocial behavior.

Management

Some stimulating products(those containing caffeine or nicotine)taken at bedtime might be helpful to allow the nonsnorers to fall asleep first.

Tricyclic antidepressants such as amitriptyline ( Elavil ), nortriptyline ( Pamelor ) and protriptyline ( Vivactil ) are helpful to some patients.
- decreasing the amount of time the sleeper spends in REM sleep, which is when snoring and apnea are the worst.
- side effects
: insomnia, prolonged dreaming with unpleasant nightmares, constipation, hesitancy with micturition, urinary retention, altered sexual potency, painful ejaculations, elevation of blood pressure and pulse rate, and aggrevation of cardiac arrhythmias.

Heavy snores should have a thorough examination of the nose, mouth, palate, nasopharynx, hypopharynx, and larynx additionally, studies in a sleep laboratory ( polysomnograms ) are essential

Medical therapy may be as simple as treatment of a nasal allergy or infection or correction of a nasal obstruction with surgery

Surgery can also remove and tighten up redundant pharyngeal tissue and shorten a long, floppy uvula and soft palate - UPPP
* Tracheostomy - the ultimate treatment for patients with far-advanced and life threatening sleep apnea.
* Chronically snoring child should be examined thoroughly

If no other specific cause for the snoring is discovered
*T et A will usually bring prompt and dramatic relief of snoring and will probably make an important difference in the health and well-being of the child

Obstructive Sleep Apnea : Sleep physiology & Pathophysiology

Diagnosis by History, Physical Exam and Special Studies

*Apnea : cessation of airflow at the nostrils and mouth for at least 10 seconds

*Hypopnea :

reduction of naso-oral airflow and thoraco-abdominal respiratory effort < 1/3 of basal volume level
decrease of O2 level

BMI : Body Mass Index(Kg/m2)

On the basis of polysomnography the apnea will be classified as central, obstructive, or a mixture with one predominating element

*SDB(sleep-disordered breathing)

*UARS(upper airway resistance syndrome):
Recently described upper airway problem, arousals during sleep related to an abnormally increased work of breathing and increased upper airway resistance, yet respiratory disturbance index(RDI) may remain normal. These arousals commonly result in symptoms of EDS(excessive daytime somnolence).

*Obstructive apnea : abscence of airflow at the nose and mouth despite discernible respiratory efforts
Caused by a structural narrowing of the upper airway that becomes manifest when muscular tone diminishes during sleep.

reduction of naso-oral airflow < 50% of basal volume level
increase of thoraco-abdominal respiratory effort > 20% of basal volume level
decrease of O2 level
arousal in EEG and ENG

*Central apnea : the patient's airway is normal, but airflow is absent because of an abscence of respiratory effort.
Caused by a neurologic defect in the control of respiration such as with bulbar poliomyelitis, degenerative neurological diseases, intracranial neoplasm, brain stem infarction, narcotic or sedative overdose, Ondine's curse, bilateral cervical cordotomy.

reduction of naso-oral airflow < 20% of basal volume level
decrease of thoraco-abdominal respiratory effort < 20% of basal volume level

*Mixed apnea : a combination of both components, beginning as central apnea followed by the onset of inspiratory effort without airflow

Sleep physiology

* Polygraphic recordings during sleep, consisting of EEG, EOG, EMG have shown sleep to be a complex state

* Normal sleep
quiet sleep or NREM sleep
active sleep or REM sleep

* The four stage of NREM sleep
- divided into stages 1 to 4 according to the types of EEG waveforms
- represent progressively deeper sleep and slowing of the EEG
- appearance of high-voltage, low-frequency slow waves in stages 3 and 4
- ANS is relatively quiescent and the respiratory rate, heart rate, and blood pressure reach their lowest levels

* REM sleep
- Most normal people experience three to five periods of REM sleep in an average night
- occurs after NREM sleep
- desynchronized EEG with low-voltage, mixed-frequency waves
- Bilateral synchronous eye movements are present
- Skeletal muscle tone is generally depressed
- EMG showing hypoactivity of muscles
- ANS activity fluctuates, which result in variable changes in heart rate, blood pressure, cerebral blood flow, metabolic rate, temperature regulation and respiration

Pathophysiology of sleep apnea

* The correct evaluation of sleep disorders requires careful monitoring of inflow at the nose and mouth, as well as monitoring of thoracic breathing movements

* Apnea index : No. of Apneic episodes / Sleep time(hr)

Definition of Sleep Apnea: the number of apneic episodes per hour of sleep(apnea index) greater than 5, with apneic episodes occuring during both REM and NREM sleep - diagnostic for sleep apnea
Clinically symptomatic patients usually have an apnea index greater than 30

*RDI : Respiratory Distress Index = (Apnea+Hypopnea) / Sleep time(hr)

* Three variables are important in the development of the collapse and obstruction of the upper airway
1. the decreased activity of the muscle dilators of the pharyngeal airway
2. the relative vacuum generated in the upper airway during inspiration
3. the surgical anatomy of the upper airway

* In patients who have obstructive apnea, the site of the predominant airway obstruction has been localized to the supralaryngeal portion of the airway

* the occlusion typically begins in the oropharynx with the tongue contacting the soft palate and posterior pharyngeal wall.

* Periods of obstructive apnea usually are terminated by brief arousals that increase pharyngeal muscular activity sufficiently to maintain airway

* apnea duration is largely determined by the briskness of the arousal response to the stimuli in REM sleep as compared with NREM sleep: apneic episodes usually last longer during REM sleep

* Significant structural narrowing of either the oral or hypopharyngeal airway, or both, has been confirmed by CT in many patients with obstructive sleep apnea
- often correlate with the clinical findings of large tonsils, excessive tissue in the soft palate, a large uvula, and a large base on tongue area

* During apneic events
- PaCO2 increases and PaO2 decreases

* Lung volume and alveolar PaO2 are the major determinants of lung oxygen stores - factors that reduce long volume ( the supine position and obesity ) and PaO2 ( hyperventilation ) act together to reduce lung oxygen stores and accelerate the rate of oxygen desaturation

* Pulmonary and systemic arterial pressures increase in response to nocturnal oxygen desaturation irrespective of the type of apnea
-> contribute to ventricular hypertrophy and eventual decompensation

* Systemic hypoxemia stimulates catecholamine release : elevated levels of which have been reported in patients with sleep apnea
-> contribute to the development of systemic hypertension in these patients

* Apnea commonly associated with prominent sinus arrythmia

* The bradycardia is mediated by increased vagal efferent activity

* Because of the possibility of apnea-associated arrhythmias, patients with obstructive sleep apnea may be at risk for cardiovascular mortality

* Patients with an apnea index greater than 20 had a much greater mortality than those with an index of less than 20

* The cumulative survival of the group treated with only UPPP was not different from the survival curve of untreated ob structive apnea patients with an apnea index greater than 20

* The obstructive apnea event is characterized by collapse of the pharyngeal airway at the level of the oropharynx and hypopharynx

* The patency of the pharyngeal airway
- under partial control of the CNS
- involuntary adjustments in muscle tone

* Factors that may contribute to the collapse of the pharyngeal airway
- atmospheric pressure
- weight of cervical tissue
- compliance of the airway walls
- inspiratory negative pressure within the airway

* Compliance of the walls of the pharyngeal airway
- depend on local factors and, most important the tone of the musculature of the pharynx

* The dispropotrionate anatomy consists of any combinationation of a large base of tongue, large soft palate, shallow palatal arch, narrow mandibular arch, or retrognathic mandible.


Associated disorders

* Central sleep apnea
- uncommon
- usually a sequelae of traumatic, infectious, ischemic, or neoplastic injury to the brain stem where the respiratory control centers are loated

* Obesity
- major disorder associated with obstructive sleep apnea,
- Considerable overlap exists of patients with obstructive sleep apnea and patients with obesity-hypoventilation syndrome
- Obese patients with obstructive apnea
: observed to develop carbon dioxide retention with added respiratory loads secondary to additional weight gain, respiratory infections, or congestive heart failure

* In addition to thyroid hormone, sex hormones are believed to play an important role in the development of obstructive sleep apnea
- high levels of testosterone have been associated with development of the syndrome
- Progesterone, which is known to stimulate ventilation, may contribute to the low frequency of disordered breathing during sleep in premenopausal women

* Patients with epistaxis treated with both anterior and posterior nasal packs may have significant obstructive sleep apnea with decreased oxygen saturation
- this may contribute to the sudden deaths that have been reported in epistaxis patients with nasal packings

* Obstructive sleep apnea has been reported in patients after irradiation of the neck
- this may be secondary to supraglottic edema and aggravated by hypothyroidism

History

* Many patients and spouses will have correctly diagnosed sleep apnea by noting the history of excessive snoring, restless sleep patterns, or apneic events at night, as well as daytime drowsiness

* Snoring sound from the passage of air through the oropharynx
-> vibtations of the soft palate

* The relaxed tone of the muscles in this area
- contribute to the excessive vibrations associated with the snoring noise

* Increased negativity in the inspired air secondary to the obstruction
- increase the turbulence in the area, thus aggravating the snoring noise

* The history may indicate nasal, facial, or pharyngeal trauma that may, in retrospect have triggered the later onset of snoring or obstructive sleep apnea

Physical exam

* 70% of patients with OSA
- 15% heavier than their ideal body weights
* A significant number have short, thick necks, with excessive cervical tissue
* Classic findings :
- redundant folds of mucosa in the oropharynx and palate, with thickened, beefy red mucosa and a prominent gag reflex
* Systemic hypertension (idiopathic)
- 30% - 50% of cases
* Soft signs
- anatomical features of the nose, pharynx, soft palate, uvula, tongue, and body type that are often seen in OSA
* The examination should include the mouth, nasal, pharyngeal, laryngeal and neck areas

Special studies

1. Fiberoptic endoscopy

* The main value of endoscopic exam
- evaluate the anatomy of the nasopharynx and hypopharynx when it cannot be seen with mirrors because of a patient's irrepressible gag reflex

* It also affords the opportunity to examine the airway during the Mueller maneuver

Mueller maneuver

: consists of a forced inspiratory effort with the mouth and nose closed
: performed with the patient in both upright and supine positions
: the fiberoptic endoscope is passed transnasally to observe upper airway patency at two different levels, the oropharyngeal level ( soft palate and the junction of the nasopharynx ) and the hypopharyngeal level( just above the epiglottis )
: the degree of airway collapse should be noted

The patient is placed on his back
-> fiberoptic scope is slipped down to various levels in the upper airway
-> The patient is instructed to close his mouth while the examiner occludes the nose with the instrument in place
-> The patient then creates a sucking maneuver

Modified Mueller maneuver

patients - sitting position(Sher et al. Laryngoscope, 1985)
-> degree of collapse graded separately at the retropalatal area, the lateral pharyngeal walls, and the base of tongue as follows:

0 : no collapse
1+ : 25% reduction of cross sectional area
2+ : 50% reduction in area
3+ : 75% reduction in area
4+ : for complete obstruction

2. Cephalometrics

* Riley et al.
- reported that a low position of the hyoid bone, with reference to the mandibular plane(MP), correlated well with poor response to UPPP
- evaluate the distance from the tongue base to the posterior pharyngeal wall and found this posterior airway space ( PAS ) to be smaller in nonresponders to UPPP. these patients have a PAS less than 7 mm and have a distance from the hyoid to the mandibular plane ( MP-H ) greater than 20 mm.

3. Polysomnography

A full polysomnographic study simultaneously records a patient's EEG eye movements (to determine sleep stage)
air movement at the nose and mouth, thoracic and abdominal respiratory movements,
chin muscle EMG
oximetry to moniter blood oxygen saturation level (pulse oxymetry) - mean and lowest O2 saturation
EKG to detect rhythm changes (modified V2 lead)
Others ( leg movements - to detect nocternal myoclonus, penile tumescence - for the study of impotence )
snoring sound

* The report can include a measure of the sleep onset time ( latency ) and the proportion of sleep time spent in each of the sleep stages.

* OSA patients - a brief sleep onset ( they fall to sleep promptly )

* Insomnia patients - a prolonged sleep onset

* Restful sleep
- evenly divided between the light stages and the deep stages
- light stages : 5 - 10 % in stage 1, 40 - 50 % in stage 2
- deep stages : 10 - 15 % in each of stages 3 and 4,
15 - 20 % in stage 5 ( REM sleep )

* OSA patients
- increase in stage 2 sleep time ( 60 - 70 % ) at the expense of stage 3 and 4
- this reflects the patient's inability to maintain an airway during deep sleep and detracts from the effectiveness - or the refreshing nature of the sleep

4. Multiple sleep latency test (MSLT)
- provides an objective assessment of the tendency to sleep
- correlates well with the subjective feelings of excessive daytime sleepiness
- measures the amount of time required for a patient to fall asleep
- The mean sleep onset latency in normal persons : 10 - 15 min
- OSA patients : have a much reduced sleep onset time

5. PFT

6. Rhinomanometry

7. Sleepiness Scale

Epworth Sleepiness Scale(ESS) : questionnaire quantification of sleepiness
Stanford's Sleepiness Scale(SSS) : questionnaire for quantification of sleepiness

Differential diagnosis

* Narcolepsy
: a syndrome which consists of excessive daytime sleepiness and abnormal manifestations of REM sleep, most commonly frequent sleep - onset REM periods
characterized by attacks of sleep with sudden onset and short duration usually last 15 min

* Sleep deprivation
* Periodic movements syndromes

Natural History

In general, the apnea worsens with age and with weight gain
- changes in the soft tissue of the airway may be important than deteriorating neurologic function
( aging is accompanied by a noticeable loss of turgor in the airway )
In patients with severe obstructive sleep apnea, a striking amount of excessive nocturnal death has been reported.
- usually from cardiovascular causes, presumably due to lethal arrhythmias
- do not have a higher incidence of coronary disease
* Chronic heart failure from sleep apnea

Nonsurgical management of snoring and OSA

* reduction of risk factors

1. Obesity -> weight reduction
- increases in lung volume attendant with weight reduction may have a favorable impact on the size of the pharyngeal lumen
- The consequent reduction in pharyngeal resistance minizes the generation of negative intraluminal pressure and thereb y mitigates the tendency toward airway collapse
- nocturnal hemoblobin oxygen desaturation may be improved

2. Sleeping position
- It was postulated that the supine position facilitated gravity - associated relapse of the tongue against the posteri oropharyngeal wall.
- with increasing weight, sleep - disordered breathing was less influenced by body position

3. Alcohol
- Animal studies suggest that alcohol precipitates and / or aggravates sleep - disordered breathing by depressing hypog lossal nerve activity
- Phrenic nerve activity is ultimately translated into the generation of negative intrapharyngeal pressure via diaphrag m contraction while
Hypoglossal nerve innervates the dilator muscles of the upper airway, stabilizing the pharynx against collapse in respo nd to this pressure

4. other drugs as risk factors
- benzodiazepine,
- flurazepam : depresses the arousal response to hypoxia and hypercapnia during sleep
- diazepam : depresses hypoglossal nerve activity
- sedatives and hypnotics

* Therapeutic agents with possible neurally mediated activity

- protriptyline a nonsedating, tricyclic antidepressant
: shortened REM sleep time
: the response of protriptyline is usually inadequate in patients with moderate and severe obstructive apnea
: side effect : anticholinergic effect
urinary hesitancy, dry mouth, constipation, decreased libido, rash, confusion, ataxia, and hair loss

- progestational agents
: ventilatory stimulant
: individuals with the greatest arterial carbon dioxide tensions and lowest arterial oxygen tensions while awake tended to have the greatest response to MPA ( medroxyprogesterone acetate )
: benefit in treating central sleep apnea and primary alveolar hypoventilation

- tryptophan

- supplemental oxygen

* Devices which act directly to maintain upper airway payency

- nasopharyngeal airway

- tongue - retaining(retraction) device( TRD )
: rationale - it increases pharyngeal patency by pulling the superior aspect of the tongue forward, away from the posterior wall of the pharynx

- Nasal continuous positive airway pressure( Nasal CPAP )
: airway pressure 7 - 15 cm of water
: this pressure acts as a pneumatic splint and passively opens the airway to prevent the obstructive episodes

<Pharyngeal surgery for OSA and snoring >

1 Rationale of surgical treatment
: bypassing the obstructive area by tracheostomy or eliminating the obstructive lesion in order to prevent soft palate collapse in the upper airway during an apneic episode

- new surgical procedure, to be acceptable, should meet the following criteria
1. low surgical risk ( safety )
2. low incidence of complications
3. minimal morbidity or functional impairment
4. reasonable success rate

2. Anatomic abnormalities of OSAS patients

1). Redundant oropharyngeal tissues
- large edematous uvula
- wide posterior pillar mucosa ( web formation )
- redundant mucosal folds of the lateral and posterior pharyngeal wall which may extend from the nasopharynx to the hypopharynx

2). A low palatal arch with a long low - haging soft palate
- contribute to the narrowing of the pharynx and facilitate airway collapse because of a flp valve mechanism during inspiration that occurs with simultaneous hypnogenic hypotonia of the pharyngeal dilator muscle

3). large tongue

4). floppy epiglottis

5). hypertrophic tonsils

6). redundant lateral pharyngeal walls

3. Indication for surgical treatment

1). significant bradycardia ( below 40/min ) with apnea
2). asystole
3). ventricular tachycardia
4). So2 falling frequently below 50 %
5). severe hypercarbia ( PCO2 greater than 50 min )
6). cor pulmonale
7). extreme hypersomnolence as measured objective by the ultiple sleep latency test (MSLT), because of the danger of causing an accident while driving

* Three degrees of hypersomnolence
1. Marked : the patient cannot stay awake even when motivated
2. Moderate : the patient frequently falls asleep whenever sedentary, job performance is suffering, and driving is usua lly a significant concern
3. Mild : the patient can stay awake to work satisfactorily and complains little about problems in driving short distances ( up to 30 min )

4. Classification of upper airway anatomy in OSA
: classified into 3 types based on upper airway anatomical findings
1). type 1
airway narrowing predominantly involves the oropharynx and the palatal arch is in a normal position
2). type II
palatal arch is in a low position and the tongue is relatively large divided into two subgroups depending on the level of predominant airway narrowing
IIa : predominantly involves the oropharynx, and the larynx and hypopharynx are easily seen with mirror
IIb : involves both the oro - and hypopharynx
3). type III
airway compromise is limited to the hypopharyngeal airway

5. Current available pharyngeal surgical procedures

1) UPPP (Uvulopalatopharyngoplasty)
- has become the most commonly used procedure to treat OSA and snoring
- designed to enlarge the potential oropharyngeal airway lumen in an attempt to reduce airway collapse during sleep
- consists of excising redundant oropharyngeal tissues from the free margin of the soft palate, tonsillar pillars, and uvula
- after incision, the noncollapsible oropharyngeal space is reconstructed by stretching the posterolateral pharyngeal wall and approximating the two palatal arch muscles

2) LAUP (Laser-assisted uvulopalatopharyngoplasty)
- allows selective excision of the uvula and soft palate
- prevents overresection and maintains palate function
- morbidity is lower owing to smaller excisions
- patients are avilable to return to work the following day
- postoperative pain : peaks on 4th day and resolves by day 10

3) Advancement of the mandible
4) Tracheotomy

References :

1. Thawley SE:"Sleep Apnea Disorders" in Cummings et al, Otolaryngology-Head and Neck Surgery, 2nd Ed. Vol 2, 1392-1413, Mosby, St. Louis, 1993

2. Michael D. Poole: "Obstructive Sleep Apnea" in Bailey et al, Head and Neck Surgery-Otolaryngology, 1st Ed. Vol 1, 598-606, J.B. Lippincott, Philadelphia, 1993

3. Fairbanks DNF, Fujita S, Ikematsu T, Simmons FG : Snoring and Obstructive Sleep Apnea. Raven Press, New York, 1985

@. Surgical planning including preop upper airway assessment

1. simple snorer and UARS(upper airway resistance syndrome) ---> LAUP

2. OSAS

2-1) 5<RDI<20 : mild OSAS without significant oxygen desaturation ---> LAUP or UPPP(patients choose)

2-2) 20<RDI<40 : moderate OSAS & 40<RDI : severe OSAS ---> multilevel pharyngeal surgery (UPPP + GA + HM) * GA=Genioglossus Advancement, HM=Hyoid Myotomy and Suspension

2-3) more severe OSAS ---> refer to CPAP(continuous positive airway pressure)

2-4) nasal obstruction ---> topical nasal corticosteroids ---> septoplasty and turbinate reduction

#"nasal spary test" described by Fairbanks(patients use intranasal decongestant spary on alternative nights for 1 week and then compare snoring on spary and nonspary nights)

References(comments by KS Suh, MD)

1. Thawley SE:"Sleep Apnea Disorders" in Cummings et al, Otolaryngology-Head and Neck Surgery, 2nd Ed. Vol 2, 1392-1413, Mosby, St. Louis, 1993

2. Utley DS, Shin EJ, Clerk AA, Terris DJ : A cost-effective and rational surgical approach to patients with snoring, UARS, or OSAS. Laryngoscope 107: 726-734, 1997

3. Fairbanks DNF, Fujita S, Ikematsu T, Simmons FG : Snoring and Obstructive Sleep Apnea. Raven Press, New York, 1985

@ Mueller's maneuver

consists of a forced inspiratory effort with the mouth and nose closed performed with the patient in both upright and supine positions the fiberoptic endoscope is passed transnasally to observe upper airway patency at two different levels, the oropharyngeal level ( soft palate and the junction of the nasopharynx ) and the hypopharyngeal level( just above the epiglottis ) the degree of airway collapse should be noted

Table. Upper airway anatomy classification of Mueller's maneuver*

*Sher AE et al, Predictive values of Mueller's maneuver in selection of patients with UPPP. Laryngoscope 1985;95:1483-1487

The degree of pharyngeal obstruction at each level is determined by the reduction of pharyngeal lumen and as recorded as;

0 : no collapse
1+ : 25% reduction of cross sectional area
2+ : 50% reduction in area
3+ : 75% reduction in area
4+ : for complete obstruction

@ Cephalometrc analysis

Cephalometric analysis is a another useful tool to identify the hypopharyngeal obstructive lesions of OSAS if associated with skeletal II and/or soft tissue abnormalitis. Riley el al* A small posterior air space(=PAS)(4-5mm; control 11.6mm) is regarded as the only consistent cephalometric finding in all nine patients evaluated. Inferiorly positioned hyoid and shorter palatal length on cephalometric X-ray are also charactristic of PPP failures. Abnornal mandibular postion was present in only 50% of PPP failures.

MP: Mandibular Plane

*Riley RW et al, Palatopharyngoplasty failure, cephalographic roentgenograms, and obstructive sleep apnea. Otolaryngol Head Neck Surg 1985; 93:240-243