Evaluation of Upper Airway
The upper airway structure and obstructive sleep apnea syndrome may be evaluated with a physical examination, fiberoptic endoscopic evaluation, and cephalometric x-rays. The physical examination is done with special expertise to indentify the traits which pertain to the upper airway that collapse during sleep. The fiberoptic endoscopic examination is performed using special telescopes which allow measurement of both size, shape, and collapsibility. Cephalometric x-rays are special x-rays of the face which allow two dimensional measurement of the bone and soft tissues.
Three Basic Types of Airway Obstruction
Using the above mentioned methods there are three basic types of airway obstruction.
Type I: Obstruction of the upper part of the throat. Many patients will have:
Long and thickened soft palate
Narrow width and depth of the upper throat
Large uvula with wrinkling or "telescoping" of excess tissue
Bulge from hypertrophy of muscle in the throat
Redundant mucosal folds
Type II: Combined upper and lower obstruction of the throat
Collapsing and obstruction from the sides of the throat
Obstruction involve both palate and tongue base segments
Type III: Obstruction of the lower part of the throat
Obstruction at the base of the tongue
Increased lingual tonsils (base of the tongue)
Redundant tissues of the upper voice box
A small mandible (lower jaw bone) or maxilla (upper jaw bone) with or without an abnormal "bite" occlusion
Increased neck girth
African American, Hispanic, or Asian Race
Goals of Upper Airway Evaluation
Identifying pathologic tissue obstructing the upper airway
Identifying levels or segments of obstruction (to guide surgery)
Methods of Evaluating the Upper Airway
Nasopharyngoscopy during sleep and wakefulness
Mueller's Maneuver - The Mueller's maneuver with fiberoptic nasal endoscopy has demonstrated variable results in predicting uvulopalatopharyngoplasty (UPPP) success.
The Mueller's maneuver is a reverse Politzer maneuver. An expiration (breathing out) with a fiberoptic scope sequentially viewing the upper and lower pharynx, the patient attempts an inspiration (breathing air into the lungs) with mouth closed and nostrils closed shut. Collapse during the negative inspiratory pressure is speculated to reflect collapse during sleep.
Prospective studies of surgical UPPP patients have found that patients likely to obstruct in the tongue base segment with this maneuver have a much lesser chance of UPPP success.
Mueller's maneuver does not necessarily correlate to manometrically measured levels of obstruction during sleep or to levels of obstruction endoscopically viewed in sedated patients.
Compared to other more direct methods Mueller's maneuver has 60% false negative and false positive results in identifying tongue base obstruction. The identification of tongue base obstruction varies due to patient positioning. Supine (lying on back) position better identifies tongue base abnormalities that manifest during sleep.
Cephalometric x-rays - Lateral cephalometric roentgenography utilizes a standard technique to identify and quantitate skeletal as soft tissue landmarks. Direct determination of the airway measurements may be difficult due to physiologic variability.
Cephalometric roentgenography provides insight into the underlying structural abnormalities in obstructive sleep apnea. Various skeletal and orthodontic relationships have been associated with specific soft tissue findings.
Patients with normal facial relationships and Type I normal dental occlusion demonstrate greater soft tissue disproportion.
Patients with retrognathia and Type II occlusion may manifest obstructive sleep apnea syndrome with less obesity and may or may not demonstrate severe soft tissue disproportion of the pharynx. Retrognathia, a narrow posterior auspice at the tongue base, an inferiorly positioned hyoid bone, and a longer soft palate have been associated with poorer palatopharyngoplasty results.
Upper Airway Manometry
Because physiologic state, position, and respiration alter the size and position of the upper airway, most methods, which do not control for these variables, will normally be imprecise.
Abnormalities, which decrease the structural size or increase the collapsibility of the upper airway, may contribute to objective sleep apnea syndrome.
Airway size has been inversely related to severity of disease. Hypertrophic tonsils and adenoids, tumors, cystic masses, and craniofacial syndromes may contribute but these are unusual as an isolated etiology (origin of a disease) in adults.
Instead, non-pathologic redundant or obstructive tissues are common. These normal but obstructive tissues have been referred to "disproportionate." This result in an upper airway that is smaller and more collapsible in obstructive sleep apnea than age and weight matched non-apneics.