1
Methods of Airway Evaluation
As the interest in sleep-disordered breathing (SDB) has increased, various attempts have been made to assess upper airway anatomy in patients with this relatively frequent disorder. From the very beginning, researchers and clinicians used a multitude of different techniques not only to reveal potential differences in upper airway anatomy to better understand the origin and the pathophysiology of the disease, but also to improve patient management and treatment success. Whereas the value of thorough clinical assessment remains indubitable, the value of the Mueller maneuver has been questioned from the beginning. Static radiologic imaging techniques such as x-ray cephalometry, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) have been used mostly to detect differences in airway anatomy. Dynamic scanning protocols (e.g. ultrafast CT or cine MRI) and multiple pressure recordings have been used to gain insights into the mechanism and level of airway obstruction. Upper airway endoscopy has been inaugurated during sleep and sedated sleep to directly visualize airway obstruction, and the assessment of critical closing pressures has been used to quantify upper airway collapsibility.
2
Clinical Examination and Clinical Scores
A clinical examination, including an endoscopy of the upper airway during wakefulness, still constitutes the basis of every airway evaluation in snorers and obstructive sleep apnea (OSA) patients. Anatomic and static clinical findings were the first parameters to be evaluated to improve treatment success. The impact of enlarged palatine tonsils became evident in the surgical experiences with children. If performed simultaneously, tonsillectomy was described by most authors as a positive predictive factor for a successful uvulopalatopharyngoplasty (UPPP). All the other anatomic parameters such as the size of the uvula, the existence of longitudinal pharyngeal folds, and so forth did not show any relationship to the success rate of UPPP if evaluated separately. In contrast to the significant influence of enlarged tonsils in palatal obstruction, equivalent clinical finding for tongue base obstructions could not be detected. Woodson and Wooten only found hints that the oropharynx was normal in cases with retrolingual obstruction.
Aware of this dilemma, Friedman et al. developed a clinical four-degree staging system incorporating the tonsil size, the position of the soft palate, the tongue size, and the body mass index (BMI). This anatomic staging system predicted the success rate better than OSA severity only for classic UPPP. One may argue that the staging system merely reflects the clinical examination of an experienced sleep physician; nevertheless, such a system may be particularly helpful for less experienced observers.
Whether there are further predictive anatomic parameters for other surgical strategies has not been evaluated to date. The subjectivity of the assessment and the variability of the nomenclature of the clinical findings are significant limitations in this context.
3
The Mueller Maneuver
Snoring as well as apneas can be simulated by most people, and a direct effect of the Mueller maneuver may be seen during wakefulness. Thus snoring simulation and the effects of the Mueller maneuver have been used in upper airway evaluation before surgical intervention in patients to predict surgical outcome and to improve patient selection. Nevertheless, the value of this relatively simple examination has been questioned repeatedly in the past.
3.1
Techniques of the Maneuver
To be able to compare results between different investigators and patients, as well as before and after an intervention, the maneuver should be performed and documented in a standardized fashion. Because of its simplicity, according to Sher et al., the classification has been widely used to describe the finding obtained during the maneuver. In this classification, four degrees of airway obstruction at the different levels are defined, ranging from minimal to complete occlusion. Furthermore, any visible obstruction linked to the epiglottis is described. The reproducibility and inter-rater reliability of the results remain problematic. Taking all the available data into account, the reliability of the Mueller maneuver remains highly questionable, and the evaluation of the maneuver seems highly subjective and hard to reproduce.
3.2
Predicting Airway Obstruction During Sleep and Surgical Success
There is some evidence that the sites of obstruction detected with the Mueller maneuver do not reliably reflect the sites of obstruction during sleep. This could be demonstrated through a comparison with videoendoscopy, multichannel pressure recordings, and dynamic MRI during sleep. Table 3.1 shows the different sites of airway obstruction detected with the different methods of airway evaluation according to selected examples from the literature.
| Method | Author | Diagnosis | n | Palatal | Retrolingual | Combined | Epiglottis | No Result |
|---|---|---|---|---|---|---|---|---|
| Mueller | Petri et al. | OSAS | 30 | 8 | 0 | 22 | n.d. | 0/30 |
| maneuver | Sher et al. | OSAS | 171 | 101 | 56 | 14 | 2/101 | 0/171 |
| Skatvedt | SBAS | 20 | 4 | 0 | 4 | n.d. | 0/20 | |
| Sum (mean value %) | 221 | 113 (51%) | 56 (25%) | 40 (18%) | 2 (1%) | 0/221 (0%) | ||
| Endoscopy | Launois et al. | OSAS | 18 | 11 | 2 | 5 | n.d. | 8/26 |
| during sleep | Woodson and Wooten | OSAS | 11 | 5 | 6 | n.d. | n.d. | n.d. |
| Sum (mean value %) | 29 | 16 (55%) | 8 (28%) | 5 (17%) | 8/26 (31%) | |||
| Endoscopy | Croft and Pringle | SBAS | 56 | 25 | n.d. | 31 | 0 | 15/71 |
| under sedation | Pringle and Croft | SBAS | 70 | 33 | 9 | 28 | 0 | 20/90 |
| Camilleri et al. | SBAS | 25 | 17 | 0 | 8 | 0 | 2/27 | |
| Hessel et al. | SBAS | 340 | 111 | 8 | 221 | n.d. | n.d. | |
| Steinhart et al. | SBAS | 306 | 139 | 23 | 134 | 10 | 16/322 | |
| Den Herder et al. | SBAS | 127 | 65 | 15 | 47 | n.d. | n.d. | |
| Quinn et al. | Snoring | 50 | 35 | 4 | 5 | 6 | 4/54 | |
| Marais | Snoring | 168 | 101 | 52 | 13 | 2 | 37/205 | |
| El Badawey et al. | Snoring | 46 | 8 | 2 | 36 | n.d. | 5/55 | |
| Abdullah et al. | Snoring | 30 | 12 | 0 | 18 | 0 | n.d. | |
| Abdullah et al. | OSAS | 89 | 12 | 4 | 71 | 2 | 4/93 | |
| Sum (mean value %) | 1307 | 558 (43%) | 117 (9%) | 612 (47%) | 20 (1.5%) | 103/917 (11%) | ||
| Pressure | Hudgel | OSAS | 9 | 4 | 5 | 0 | n.d. | 0/9 |
| recordings during sleep | Chaban et al. | OSAS | 10 | 5 | 5 | 0 | n.d. | n.d. |
| Metes et al. | SBAS | 51 | 30 | 7 | n.d. | n.d. | 13/51 | |
| Tvinnereim and Miljeteig | OSAS | 12 | 6 | 2 | n.d. | 4 (?) | 0/12 | |
| Skatvedt | SBAS | 20 | 2 | 5 | 10 | n.d. | 0/20 | |
| Katsantonis et al. | OSAS | 20 | 5 | 4 | 9 | 2 (?) | 0/20 | |
| Woodson and Wooten | OSAS | 11 | 8 | 3 | n.d. | n.d. | n.d. | |
| Sum (mean value %) | 133 | 60 (47%) | 31 (23%) | 19 (14%) | 6 (4,5%?) | 13/112 (12%) |
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