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Clinical Investigations: SLEEP AND BREATHING |

Sites of Obstruction in Obstructive Sleep Apnea* FREE TO VIEW

Anil N. Rama, MD, MPH; Shivan H. Tekwani, BS; Clete A. Kushida, MD, PhD
Author and Funding Information

*From the Stanford University Center of Excellence for Sleep Disorders, Stanford, CA.

Correspondence to: Clete A. Kushida, MD, PhD, Stanford University Center of Excellence for Sleep Disorders, 401 Quarry Rd, Suite 3301, Stanford, CA 94305-5730; e-mail: clete@stanford.edu



Chest. 2002;122(4):1139-1147. doi:10.1378/chest.122.4.1139
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Study objective: The aim of this article was to identify the most common sites of obstruction in patients with obstructive sleep apnea (OSA) by a systematic review of published studies.

Design: The review was conducted by a MEDLINE search of the English literature published during the years 1980 to 2002. The inclusion criteria were experiments involving five or more adult subjects, total rather than partial obstruction or narrowing of the upper airway, and techniques that were performed on the subjects while they were asleep.

Conclusion: Although there was considerable variability in the techniques and the results, the most common site of obstruction detected by these studies was at the level of the oropharynx, with extension to the laryngopharynx commonly observed.

Figures in this Article

Obstructive sleep apnea (OSA) is the intermittent cessation of breathing during sleep due to the collapse of the pharyngeal airway. The identification of the sites of upper airway (UA) obstruction in patients with OSA may be beneficial in choosing the appropriate surgical intervention.1Precise localization of the sites of UA occlusion during sleep has been attempted by a variety of techniques including nasopharyngoscopy, fluoroscopy, pressure measurements, CT scanning, and MRI (Table 1 ).2,47,918,2025,2731 Each particular technique has its unique advantages and disadvantages (Table 2 ), which may account for the wide variability in the observed results.

Preliminary article searches were performed for the years 1980 to 2002 using the key words sites of obstruction, obstructive sleep apnea, CT, and MRI. Articles from the search were collected and screened based on the following selection criteria: studies consisted entirely of adults > 18 years of age; studies recorded complete rather than partial obstruction or narrowing of the UA; studies employed techniques that were performed during sleep, induced with or without sedation; and studies that involved five or more patients. Articles written in a language other than English were not included, unless they contained abstracts from which relevant data could be obtained.

Various investigations, such as those by Badr et al,32Launois et al,33and Rubinstein and coworkers,3435 have focused on pharyngeal narrowing as opposed to complete obstruction. While articles such as these did localize the sites of narrowing in patients with OSA, they were not included in this review because there are no collective standards for pharyngeal narrowing. Pharyngeal narrowing is a more subjective measurement, and what one investigator may consider to be narrowing another may not. In order to reduce confusion and to make the comparisons more homogenous, only investigations focusing on complete obstructions were used. Although the exclusion of investigations focusing on the narrowing of the UA may allow for easier comparisons between studies, it may unjustly simplify the true physiologic process of OSA, which is characterized by hypopneas as well as apneas. In addition, having set a 22-year data search limit, a number of investigations performed prior to 1980, such as those by Lugaresi et al36and Borowiecki et al,37were excluded. Also, other investigations, such as those by Haponik et al38and Schwab et al,39 studied awake patients, using CT scanning and MRI, respectively. Studies on awake patients were excluded because the physiology of the UA while a patient is awake does not reflect the true physiology of the UA during sleep.17

After the initial screening process, additional articles were chosen from the references of the included research articles. These articles were subjected to the same inclusion criteria. Collectively, the articles were compared for their experimental techniques and results in the localization of the sites of obstruction in OSA patients.

Based on standard anatomic definitions,26 the pharyngeal airway can be divided into the following three regions of interest: the nasopharynx, defined as the area behind the nose and above the soft palate; the oropharynx, defined as the area from the soft palate to the upper border of the epiglottis; and the laryngopharynx, defined as the area from the upper border of the epiglottis to the inferior border of the cricoid cartilage (Fig 1 ). Due to a lack of consensus, investigators have used a broad range of terminology to refer to the same or overlapping parts of the pharyngeal airway. For instance, the terms retropalatal (behind the soft palate), retrolingual (behind the tongue), velopharynx, and mesopharynx have been used to refer to the same or overlapping parts of the oropharynx. In addition, the terms hypopharynx and supralaryngeal airway have been used to refer to the same or overlapping parts of the laryngopharynx. When the data from the various articles are presented, we have used the authors’ terminology in describing the sites of obstruction. Table 3 correlates the authors’ wide range of terminology to standard anatomic definitions.

Endoscopy represents one of the earliest techniques that was used to detect the sites of obstruction in OSA patients and involves using a nasopharyngoscope. Rojewski et al2 studied 11 patients using simultaneous polysomnography and video recordings from a 4.4-mm diameter nasopharyngoscope. Detailed data were not provided, but the investigators found the level of obstruction in the area of the hypopharynx. The length of the collapsing segment was variable and was observed to extend as high as the velopharyngeal sphincter. Remmers et al29and Isono et al30 used endoscopy and catheters combined with nasal airway positive pressure and muscle paralysis to identify the portion of the UA that was most likely to collapse in the absence of pharyngeal muscle contraction. Remmers et al29found that a majority of obstructions occurred in the nasopharynx, while Isono et al30 found that a majority of obstructions occurred in the velopharynx. These data should be interpreted with caution as the collapsing segment identified by their methods may not reflect the region of closure during spontaneous apneas.

Endoscopy allows for the direct visualization of the interior of the UA. However, the disadvantages include the stenting open of the airway by the endoscope, the increase in UA resistance and the decrease in airflow by the endoscope, the need to move the endoscope for better UA visualization during the course of the night, and the wide variation in the duration of testing due to the subjects’ ability to tolerate the equipment. The use of anesthesia prior to endoscopy has been implicated in altering the characteristics of the UA.8

Fluoroscopy is a technique used to observe the internal structure of the UA using x-rays. Suratt et al3studied 11 patients using videofluoroscopy with or without barium and obtained data in 6 patients who fell asleep and had UA obstruction. All six patients had obstructions during inspiration when the soft palate touched the posterior pharyngeal wall and tongue, with extension of the obstruction in the caudal direction. Hillarp et al4studied 57 patients using video recordings of the UA after nasal and oral ingestion of barium contrast material. The investigators found the site and length of the obstruction during the obstructive apnea had interindividual and intraindividual variation. Obstructions with pharyngeal collapse extending below the uvula were more common (59%) than those that were primarily palatal (28%). Obstructions at two levels, namely, the soft palate-uvula interface and the epiglottis, were seen in seven patients. One problem with fluoroscopy is the lack of simultaneous polysomnography. Walsh et al5 overcame this problem by examining 45 patients using somnofluoroscopy (ie, lateral fluoroscopic examination of the UA with simultaneous polysomnography). Adequate data were found for 40 patients, with the initial obstructions starting above the C2 vertebra level in 26 patients and below the C2 vertebra level in 13 patients. Although no specific data were provided, the investigators found that there was propagation of the occlusion in the caudal and rostral directions. They also found that the UA dynamics were variable among patients. However, unlike Hillarp et al,,4 they appeared consistent within a given patient. Pepin et al6 used somnofluoroscopy to study 11 patients and found that the UA collapsed at the oropharynx in all 11, with extension to the hypopharynx in 10 patients, and extension to the pharyngolarynx in 5 patients.

Fluoroscopy not only provides a dynamic view of the UA during sleep, but it also allows the visualization of events outside the pharyngeal airway. For instance, movements of the cervical spine, downward motion of the hyoid bone, and jaw movements at the end of an apnea can be observed directly. In addition, the activation of the masseter muscle may be important for reopening the UA.7Compared to other methods, fluoroscopy also avoids the use of anesthesia, which has been reported to alter the properties of the UA.8

Fluoroscopy has a number of disadvantages. For example, the use of radiation can limit the number of apneas that can be recorded in each patient. Walsh et al5examined three to five apneas in each patient, and Pepin et al6 examined five apneas in each patient. Consequently, not all stages of sleep can be examined. This is important because, as will be discussed later, UA collapsibility may vary between rapid eye movement (REM) and non-REM (NREM) sleep. Another disadvantage is that lateral fluoroscopy visualizes the UA in only two dimensions, making it difficult to obtain precise measurements of the UA lumen with this technique. Other disadvantages include the use of barium contrast,34 the use of sedation (eg, benzodiazepines) to induce sleep,,4 and the health risks of radiation exposure.

Catheters positioned in the UA can measure pressure differences during an apnea to localize the sites of obstruction. UA pressure measurements have been attempted using a variety of techniques, including fluid-filled catheters,9movable catheters,1011 bias-flow catheters,1,12and micropressure sensors.1318 The techniques have varied from the use of only one movable catheter, one to several stationary catheters, or a combination of stationary and movable catheters, all containing variable numbers of pressure transducers. One advantage of using a catheter over other methods such as endoscopy, fluoroscopy, CT scanning, or MRI is the ability to obtain a full night’s data. Hudgel12 studied nine patients with four pressure-monitoring catheters and found five patients with hypopharyngeal obstructions and four patients with palatal obstruction. Chaban et al11 studied 10 patients using two stationary catheters and one movable catheter and found 5 patients with soft palate obstruction and 5 patients with tongue base obstruction. However, the use of multiple catheters might stent open the UA and, possibly, might prevent apneas and hypopneas that would otherwise occur. Metes et al10 tried to overcome this problem by using a single, movable catheter to study 51 patients. Data were obtained from 37 patients, with 30 patients found to have retropalatal collapse and 7 patients found to have retrolingual collapse. However, the mechanical stimulation of the pharyngeal wall inflicted by a movable catheter possibly may disrupt sleep and affect the respiratory events that are being observed. Shepard and Thawley9 tried to overcome this problem by using a 6-mm diameter multiport catheter with four pressure sensors to evaluate 18 patients, and they found 10 patients with oropharyngeal collapse and 8 patients with initial oropharyngeal collapse extending to the region of the base of the tongue. Katsantonis et al15 used a 2.3-mm diameter, four-pressure-sensor catheter to examine 20 patients. Fourteen patients had UA collapse confined to or initiating in the oropharyngeal region, with the obstruction extending to the tongue base in 7 patients and to the entire UA in 2 patients. Four patients had UA collapse at the base of the tongue, and two patients had collapse at the hypopharynx. Rollheim et al18 studied 13 patients using a 2-mm diameter, four-pressure-sensor catheter in both an in-hospital and ambulatory setting. Of the 11 patients who completed the study, the investigators found that the relationship between upper and lower obstructive events is reproducible between ambulatory and hospital recordings. Rollheim et al,31 in a separate study, also noted the repeatability of sites of obstructive events in patients who have frequent apneic events or a high degree of transpalatal or subpalatal predominance, particularly in those patients who have a combination of these two criteria. The investigators added that it was rare to find exclusively upper or lower obstructions. The majority of patients had a mixture of both, with transpalatal obstructions being more common than subpalatal obstructions.

Since the difference in pressure gradients is used to determine the site of obstruction, it seems intuitive that the greater the number of pressure sensors used, the more precise will be the determination of the site of obstruction. Tvinnereim and Miljeteig13studied 12 patients using a five-pressure-sensor catheter and found that 6 patients had obstructions between the rim of the soft palate and the middle mesopharynx, 2 patients had obstructions between the middle mesopharynx and the top of the epiglottis at the tongue base, and 4 patients had obstructions between the top of the epiglottis at the tongue base and the upper esophagus. Woodson and Wooten14 studied 12 patients using a 2.3-mm diameter, five-pressure-sensor catheter and found the initial obstruction in 9 patients at the level of the palate, and in 3 patients at the level of the tongue base. Three patients with initial obstructions at the palate demonstrated distal obstruction on subsequent occluded breaths. Interestingly, simultaneous videoendoscopy in four of these patients with a palatal level of obstruction also identified near-total visual UA collapse without obstruction of the lower oropharynx, which was not identified by pharyngeal manometry. Boudewyns et al17 studied 28 patients using a 2-mm diameter, five-pressure-sensor catheter and found that the site of UA obstruction varied among consecutive apneas in all but 2 patients. The lower limit of the UA obstruction was predominantly located at the nasopharynx and oropharynx. Boudewyns et al27 also studied 10 patients before and after they underwent uvulopalatopharyngoplasty and found that patients with UA collapse that was restricted to the oropharynx were the most likely to benefit from the surgery.

Various investigators9,14 have concluded that UA obstruction is located at one particular site in the UA that remains the same during consecutive apneas. This is in contrast to the conclusions of other investigators who have demonstrated that apneas may result from obstruction at variable sites in a given patient.13,1617 Tvinnereim and Miljeteig,13 Skatvedt,16and Boudewyns et al17 found multiple sites of UA obstruction in 1 of 7 patients, 7 of 20 patients, and 26 of 28 patients, respectively. The literature supporting a single point of obstruction stems from early studies with technical limitations, whereas more recent literature employs more sophisticated technology and thereby has identified accurately multiple sites of obstruction.

Furthermore, UA collapsibility may vary among different sleep stages. Katsantonis et al15 mentioned that the site of obstruction remained constant throughout sleep stages and positions, but detailed data on this issue were not discussed. Boudewyns et al17 demonstrated that during REM sleep more apneas occurred at the oropharynx compared to the nasopharynx, and in three patients tongue base and/or hypopharyngeal obstruction occurred only during REM sleep and not during NREM sleep or wakefulness. Shepard and Thawley9 studied nine patients specifically during REM and NREM sleep and observed an extension of the collapse toward more caudal segments of the UA during REM in seven patients. They also noted that in 10 of 18 patients, independent of the sleep state, sleep position had little effect on the extent over which the UA collapsed.

The wide discrepancy in the results may be attributable to a variety of reasons. First, the various investigators’ use of different definitions for the same or overlapping segments of the UA is confusing. Shepard and Thawley9 defined oropharyngeal collapse as an absence of pressure deflections in two sensors located at the level of the soft palate and at the base of the tongue. By contrast, Katsantonis et al,15 defined oropharyngeal collapse as the absence of pressure deflections in a sensor located at the posterior choanae. Furthermore, what Boudewyns et al,17 defined as nasopharyngeal collapse corresponds with what Katsantonis et al,15 defined as oropharyngeal collapse, and what Boudewyns et al,17 defined as oropharyngeal collapse matches what Shepard and Thawley,9 defined as oropharyngeal collapse. In addition, in an earlier study by Hudgel,,12 stationary catheters were positioned without confirmatory radiographs, making the anatomic localization imprecise.

Second, the ability to precisely detect the site of obstruction depends on the number of pressure sensors used. For instance, sensors located at the posterior choanae, the rim of the soft palate, and the level of the hyoid bone allow classification into retropalatal and retrolingual sites of obstruction. Obstruction located between the soft palate and tongue base cannot be differentiated from occlusion occurring between the tongue base and supralaryngeal segment with this technique. Several investigators1314,1617,40 used five or more pressure sensors located at various locations in the UA. This technique allowed for the detection of additional sites of obstruction when compared to investigators who used fewer sensors.9,15

Third, the use of pressure sensors to determine the sites of obstruction may have some limitations. For instance, the technique only permits identification of the lower limit of obstruction. Although manometry allows the measurement of pressure changes at different levels of the UA simultaneously, it does not identify narrowing at nonobstructive segments of the UA during a respiratory event with the complete cessation of airflow. Combining videoendoscopy with manometry, Woodson and Wooten14 observed narrowing of the pharyngeal segments that were not identified as the initial site of obstruction. Specifically, the manometric obstruction noted during expiration was observed by videoendoscopy to extend caudally during inspiration, which was associated with increased negative pressures. Consequently, manometry may miss visually observed collapse at nonobstructive segments of the UA. Chaban et al11 attempted to overcome this problem by using a movable catheter to determine both the lower and upper limits of obstruction. However, they were unable to determine the upper limit of obstruction in the vast majority of their subjects, possibly due to the interaction between the catheter and the pharyngeal wall.

Fourth, it is not known how the use of anesthesia or the placement of the catheter in the UA interferes with the UA dynamics. The use of local anesthesia may alter the collapsibility of the UA by impairing pharyngeal reflexes.19 Other investigators have hypothesized that UA anesthesia may impair the arousal response by affecting the UA mechanoreceptors.8 The use of a catheter in the UA may also disturb sleep and reduce sleep efficiency.17 To minimize this potential problem, several investigators1317 have utilized a single, stationary multisensor catheter to record simultaneous obstructions in more than one pharyngeal segment with minimal physiologic interference and discomfort to the patient.

Fifth, investigators have used at least two contrasting procedures to determine the site of obstruction using catheters. The first is based on changes in pressure pattern, which was proposed by Hudgel12 and has been used by several investigators including Boudewyns et al.17 For example, the site of obstruction was determined to be in the hypopharynx if inspiratory pressure swings ceased from the nasopharyngeal and oropharyngeal catheter tracings but persisted in the hypopharyngeal tracings during the absence of inspiratory flow.1 The second method is based on the gradient in inspiratory pressures between different sensors, which was used by Skatvedt.16 Specifically, Skatvedt defined a clinically significant obstruction as occurring when the pressure difference between two transducers was > 50% of the more caudal of the two pressures.40 Regardless, the use of catheters neither provides volumetric data nor identifies the anatomic structures that contribute to collapse and obstruction.

Sixth, movement of the inserted catheters may result in the erroneous identification of a site of obstruction.

CT scanning is a noninvasive imaging technique that can provide a quantitative assessment of the UA. Stein et al20evaluated eight patients using cine CT scans (scanner capable of multiple-level, rapid-sequence scans) and found that all eight patients had obstructions at the uvula and oropharynx, but that the length of obstruction varied from one patient to another. In three of the eight patients, the obstruction extended caudally to the hypopharynx. Furthermore, in three of eight patients, as the obstruction moved caudally the rostral areas opened, creating a “seesaw” pattern of obstruction. Crumley et al21 studied eight patients using cine CT and found that all eight patients had airway closure at the velum and oropharynx, and that three of the eight also showed closure at the high hypopharynx-hyoid site. Four of the eight patients demonstrated changing levels of closure. Specifically, three patients showed a seesaw pattern of closure initially affecting the velum and oropharynx, and later affected the low oropharynx and high hypopharynx, accompanied by a reopening of the velum and oropharynx.

The advantages of CT scanning include the ability to scan the entire airway, the ability to combine it with polysomnography, and the noninvasive nature of the technique. The disadvantages of CT scanning in the selected studies include the use of only axial images, the inability to image the entire pharyngeal airway in a single plane, the ability to record only a short period of time, and the health risk of radiation exposure.

MRI has been used to investigate the dynamic changes of the UA in OSA patients. Suto et al22studied 15 patients using ultrafast MRI, and obstruction was noted in 13 patients. Six patients had a single obstruction at the velum palatinum, while seven patients had multiple levels of obstruction (obstructions at the velum palatinum and oropharynx, five patients; obstruction at the velum palatinum, oropharynx, and hypopharynx, one patient; and obstruction at the velopharynx and hypopharynx, one patient. Yokoyama et al23studied 12 patients using ultrafast MRI and found 9 patients with obstructions in the upper mesopharynx and 3 patients with obstructions in the upper and mid-mesopharynx. Suto and Inoue24studied 33 patients using inversion recovery-turbo fast low-angle shot (FLASH) imaging sequences and found obstruction in 31 of 33 patients. Twenty-one patients had obstructions at the velopharynx alone, 8 patients had obstructions at the velopharynx plus the oropharynx, and 2 patients had obstructions at the velopharynx, oropharynx, and hypopharynx. One particular disadvantage of these earlier studies was that they did not permit the UA to be monitored for long periods of time. Specifically, although FLASH MRI permits subsecond sagittal imaging, this method is able to provide an image series of only approximately 1 min. Furthermore, high-field MRI systems generate a great deal of noise, requiring the use of sedation to achieve sleep. Yoshida et al25 tried to overcome these problems by studying 22 patients using low-field magnetic resonance fluoroscopy, which allowed for long-term monitoring and a quiet environment, negating the need for IV tranquilizers. They recorded at least 30 min of sleep for each patient, and 21 of 22 patients did not require sedation. Data were acquired for 20 patients, and the investigators found 9 patients with occlusions in the retropalatal pharynx and 11 patients with both simple retropalatal and combined retropalato-retroglossal obstructions. Ikeda et al28 avoided the use of sedation, but 13 of 19 patients could not fall asleep spontaneously due to the noise of the MRI device and were excluded from study. Data obtained from six patients showed that all patients had obstructions at the level of the soft palate (which was defined as the area above the lower tip of the uvula), with two of the patients showing an additional obstruction at the oropharynx (which was defined as the area between the lower tip of the uvula and the upper tip of the epiglottis).

The advantages of MRI include a choice of multiple scanning planes, high-contrast resolution, noninvasiveness, and the possibility of observing the pharynx in real time. Disadvantages include the inability to record a full night of sleep, the lengthy time for each imaging slice (approximately 1 s), the lack of simultaneous polysomnography, the use of sedation (benzodiazepines or hydroxyzine hydrochloride) to fall asleep during FLASH MR imaging, and the loud noise of the MRI machine during FLASH MR imaging, which may disrupt sleep.

Diverse methods have been used to identify sites of obstruction in OSA patients. No technique is without methodological problems, ranging from the invasiveness of the procedures with concomitant sleep disruption (eg, endoscopy and catheters) to viewing time limitations secondary to radiation exposure (eg, fluoroscopy and CT scanning). Given these limitations, the precise localization of the sites of obstruction in patients with OSA may not be possible using current techniques. Nevertheless, the majority of studies, irrespective of technique, indicate that the primary site of obstruction is at the level of the oropharynx, although extensions to the laryngopharynx are frequently observed.

Early investigations confined the site of obstruction in OSA patients to one particular location, whereas more recent studies have demonstrated multiple sites of obstruction, seesawing obstructions, and varying obstructions within the same individual. Technologic advances in the methods used to detect the sites of obstruction in OSA patients have demonstrated that the UA is more dynamic than originally thought. The variable sites of obstruction imply a complex underlying pathogenesis of UA obstruction that is affected by many factors, including neck anatomy, adipose tissue distribution, anesthetics, sleep stage, and a variety of other components that are still unknown and collectively result in varying types of obstructions within the same individual.

A number of investigators have advocated localizing a site of obstruction as a means to support a given surgical procedure, such as a uvulopalatopharyngoplasty. The logic of this endeavor is essentially flawed, given the dynamic nature of the UA. The site of obstruction in a given OSA patient is as unique as his or her fingerprints, and efforts to advocate one surgical procedure for a single point of obstruction are unsound.

Additional studies precisely characterizing the dynamic obstructions in OSA patients would be interesting. These investigations should include larger samples of patients, the use of anatomic nomenclature based on that in Gray’s Anatomy,26 and the development of new assessment techniques. More importantly, however, future work should be directed toward understanding the complex interaction of the myriad factors determining airway obstruction, and the search to justify a given surgical procedure should be abandoned.

Abbreviations: FLASH = fast low-angle shot; NREM = non-rapid eye movement; OSA = obstructive sleep apnea; REM = rapid eye movement; UA = upper airway

Table Graphic Jump Location
Table 1. UA Sites of Obstruction Using Various Techniques*
Table Graphic Jump Location
Table 1A. Continued
Table Graphic Jump Location
Table 1B. Continued*
* 

NA = data not available; AI = apnea index; AHI = apnea-hypopnea index; D = diameter; PSG = polysomnography; NAPP = nasal airway positive pressure; M = male; F = female; MR = magnetic resonance; S/P = status post. Values in parentheses are No. of patients.

 

In-hospital PSG.

 

Ambulatory PSG.

§ 

Mean ± SD.

 

Night 1.

 

Night 2.

Table Graphic Jump Location
Table 2. Advantages and Disadvantages of Techniques to Assess the Sites of UA Obstruction*
* 

See Table 1 for abbreviations not used in the text.

Figure Jump LinkFigure 1. Sagittal diagram of the head and neck depicting key structures of the UA.Grahic Jump Location
Table Graphic Jump Location
Table 3. Correlation of Anatomic Terms Used by Investigators to Those Defined by Gray’s Anatomy
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Badr, MS, Toiber, F, Skatrud, JB, et al Pharyngeal narrowing/occlusion during central sleep apnea.J Appl Physiol1995;78,1806-1815. [PubMed]
 
Launois, SH, Feroah, TR, Campbell, WN, et al Site of pharyngeal narrowing predicts outcome of surgery for obstructive sleep apnea.Am Rev Respir Dis1993;147,182-189. [PubMed]
 
Rubinstein, I, Bradley, TD, Zamel, N, et al Glottic and cervical tracheal narrowing in patients with obstructive sleep apnea.J Appl Physiol1989;67,2427-2431. [PubMed]
 
Rubinstein, I, Slutsky, AS, Zamel, N, et al Paradoxical glottic narrowing in patients with severe obstructive sleep apnea.J Clin Invest1988;81,1051-1055. [PubMed]
 
Lugaresi, E, Coccagna, G, Cirignotta, F Polygraphic and cineradiographic aspects of obstructive apneas occurring during sleep: physiopathological implication. von Euler, C Lagercrantz, H eds.Central nervous control mechanisms in breathing1979,495-501 Pergamon Press. New York, NY:
 
Borowiecki, B, Pollak, CP, Weitzman, ED, et al Fibro-optic study of pharyngeal airway during sleep in patients with hypersomnia obstructive sleep-apnea syndrome.Laryngoscope1978;88,1310-1313. [PubMed]
 
Haponik, EF, Smith, PL, Bohlman, ME, et al Computerized tomography in obstructive sleep apnea: correlation of airway size with physiology during sleep and wakefulness.Am Rev Respir Dis1983;127,221-226. [PubMed]
 
Schwab, RJ, Gefter, WB, Hoffman, EA, et al Dynamic upper airway imaging during respiration in normal subjects and patients with sleep disordered breathing.Am Rev Respir Dis1993;148,1385-1400. [PubMed]
 
Skatvedt, O Continuous pressure measurements during sleep to localize obstructions in the upper airways in heavy snorers and patients with obstructive sleep apnea syndrome.Eur Arch Otorhinolaryngol1995;252,11-14. [PubMed]
 

Figures

Figure Jump LinkFigure 1. Sagittal diagram of the head and neck depicting key structures of the UA.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. UA Sites of Obstruction Using Various Techniques*
Table Graphic Jump Location
Table 1A. Continued
Table Graphic Jump Location
Table 1B. Continued*
* 

NA = data not available; AI = apnea index; AHI = apnea-hypopnea index; D = diameter; PSG = polysomnography; NAPP = nasal airway positive pressure; M = male; F = female; MR = magnetic resonance; S/P = status post. Values in parentheses are No. of patients.

 

In-hospital PSG.

 

Ambulatory PSG.

§ 

Mean ± SD.

 

Night 1.

 

Night 2.

Table Graphic Jump Location
Table 2. Advantages and Disadvantages of Techniques to Assess the Sites of UA Obstruction*
* 

See Table 1 for abbreviations not used in the text.

Table Graphic Jump Location
Table 3. Correlation of Anatomic Terms Used by Investigators to Those Defined by Gray’s Anatomy

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Launois, SH, Feroah, TR, Campbell, WN, et al Site of pharyngeal narrowing predicts outcome of surgery for obstructive sleep apnea.Am Rev Respir Dis1993;147,182-189. [PubMed]
 
Rubinstein, I, Bradley, TD, Zamel, N, et al Glottic and cervical tracheal narrowing in patients with obstructive sleep apnea.J Appl Physiol1989;67,2427-2431. [PubMed]
 
Rubinstein, I, Slutsky, AS, Zamel, N, et al Paradoxical glottic narrowing in patients with severe obstructive sleep apnea.J Clin Invest1988;81,1051-1055. [PubMed]
 
Lugaresi, E, Coccagna, G, Cirignotta, F Polygraphic and cineradiographic aspects of obstructive apneas occurring during sleep: physiopathological implication. von Euler, C Lagercrantz, H eds.Central nervous control mechanisms in breathing1979,495-501 Pergamon Press. New York, NY:
 
Borowiecki, B, Pollak, CP, Weitzman, ED, et al Fibro-optic study of pharyngeal airway during sleep in patients with hypersomnia obstructive sleep-apnea syndrome.Laryngoscope1978;88,1310-1313. [PubMed]
 
Haponik, EF, Smith, PL, Bohlman, ME, et al Computerized tomography in obstructive sleep apnea: correlation of airway size with physiology during sleep and wakefulness.Am Rev Respir Dis1983;127,221-226. [PubMed]
 
Schwab, RJ, Gefter, WB, Hoffman, EA, et al Dynamic upper airway imaging during respiration in normal subjects and patients with sleep disordered breathing.Am Rev Respir Dis1993;148,1385-1400. [PubMed]
 
Skatvedt, O Continuous pressure measurements during sleep to localize obstructions in the upper airways in heavy snorers and patients with obstructive sleep apnea syndrome.Eur Arch Otorhinolaryngol1995;252,11-14. [PubMed]
 
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