Retroglossal Region Research Articles

A videoendoscopic evaluation of the upper airway in South East Asian adults with obstructive sleep apnea

We aimed to evaluate the severity of upper airway obstruction at the retropalatal and retroglossal regions in obstructive sleep apnea (OSA) patients. This is a descriptive cross-sectional study at the Sleep Clinic, Department of Otorhinolaryngology-Head and Neck Surgery. Flexible nasopharyngolaryngoscopy was performed in seated erect and supine position. Retropalatal and retroglossal regions were continuously recorded during quiet breathing and Mueller's maneuver in both positions. Captured images were measured using Scion Image software and narrowing rate was calculated. Level of each site was classified based on Fujita classification and severity of obstruction using Sher scoring system for Mueller's maneuver. A total of 59 patients participated in this study. Twenty-nine (49.2%) participants had type 1 (retropalatal) obstruction, 23 (38.9%) had type 2 (retropalatal and retroglossal), and seven (11.9%) in type 3 (retroglossal) obstruction. Fifty (84.7%) of the patients have severe obstruction at the retropalatal region in supine position (SRP) followed by 35 (59.3%) at retropalatal region in erect position (ERP), 27 (45.8%) at retroglossal region in supine position (SRG) and eight (13.5%) at retroglossal region in erect position (ERG). The average oxygen saturation showed significant association in ERP (P = 0.012) and SRP (P < 0.001), but not significant in ERG and SRG. Videoendoscopy utilizing flexible nasopharyngolaryngoscopy and Scion Image software is reliable, minimally invasive, and useful as an office procedure in evaluating the multilevel obstruction of upper airway in OSA patients. The retropalatal region has more severe obstruction compared with retroglossal region either in erect or supine position.

The impacts of open-mouth breathing on upper airway space in obstructive sleep apnea: 3-D MDCT analysis

Open-mouth breathing during sleep is a risk factor for obstructive sleep apnea (OSA) and is associated with increased disease severity and upper airway collapsibility. The aim of this study was to investigate the effect of open-mouth breathing on the upper airway space in patients with OSA using three-dimensional multi-detector computed tomography (3-D MDCT). The study design included a case-control study with planned data collection. The study was performed at a tertiary medical center. 3-D MDCT analysis was conducted on 52 patients with OSA under two experimental conditions: mouth closed and mouth open. Under these conditions, we measured the minimal cross-sectional area of the retropalatal and retroglossal regions (mXSA-RP, mXSA-RG), as well as the upper airway length (UAL), defined as the vertical dimension from hard palate to hyoid. We also computed the volume of the upper airway space by 3-D reconstruction of both conditions. When the mouth was open, mXSA-RP and mXSA-RG significantly decreased and the UAL significantly increased, irrespective of the severity of OSA. However, between the closed- and open-mouth states, there was no significant change in upper airway volume at any severity of OSA. Results suggest that the more elongated and narrow upper airway during open-mouth breathing may aggravate the collapsibility of the upper airway and, thus, negatively affect OSA severity.

Correlation between upper airway soft tissue 3-D measurement and the severity of obstructive sleep apnea hypopnea syndrome

To investigate the correlation between upper airway CT measurement value and severity of patients with obstructive sleep apnea hypopnea syndrome (OSAHS). The upper airway of 82 patients with OSAHS were scanned by CT during normal respiration. The 3-D CT measurement were made in lateral and anterior-posterior diameters, cross-section areas and volumes of retropalatal and retroglossal region. The lateral diameters and cross-section areas of every research plane were negatively correlated with apnea and hypopnea index (AHI), in particular the minimal lateral diameter of the whole airway (r = -0.558, P < 0.01). For volumes, AHI decreased with larger volume of nasal cavity, nasopharyngeal cavity and velopharyngeal cavity (P < 0.05 or P < 0.01). The negative correlation between AHI and proportion of cavity volume to the bone frame of velopharyngeal area and whole upper airway were significant (P < 0.05 or P < 0.01). But the correlation between AHI and volume of velopharyngeal soft tissue, the proportion of soft tissue to the bone frame volume of velopharyngeal area, the proportion of soft tissue to the bone frame volume of whole upper airway was significant positive, as well as the correlation between AHI and the proportion of soft tissue to the cavity volume of velopharyngeal area and whole upper airway (P < 0.05 or P < 0.01). To evaluate the severity of OSAHS with upper airway CT measurement, there is no difference between 3-D parameters and 2-D parameters. In terms of the whole airway, the lateral diameters, the cross-section area, the cavity volume, the soft tissue of the upper airway, are meaningful to evaluate the severity of disease, in particular the measurement of velopharyngeal area.

Effects of mandibular advancement on upper airway dimension and collapsibility in patients with obstructive sleep apnea using dynamic upper airway imaging during sleep

The objective of this study was to evaluate the effects of mandibular advancement on oropharyngeal dimension and collapsibility and reveal the predominate site of change produced by mandibular advancement in patients with obstructive sleep apnea (OSA). Sixteen adults (13 males and 3 females) with symptomatic mild to severe OSA participated. Custom-made silicone mandibular positioners were used to keep the mandible at 67% of maximum advancement. Changes in the oropharyngeal size and collapsibility with mandibular advancement were evaluated using ultrafast computed tomography taken during wakefulness and midazolam-induced sleep. Cross-sectional areas were assessed using electron beam tomography at 4 levels: high retropalatal (HRP), low retropalatal (LRP), high retroglossal (HRG), and low retroglossal (LRG). During sleep, the minimum cross-sectional areas decreased 36.5%, 67.8%, 75.5%, and 65.8% at each level of HRP, LRP, HRG, and LRG respectively, as compared with those measured during wakefulness. Mandibular advancement during sleep increased 75.7%, 141.3%, 128.1%, and 119.9% at each level. The oropharynx showed 70.3%, 110.4%, 140.3%, and 156.9% increase in the Collapsibility Indices during sleep at each level of HRP, LRP, HRG, and LRG, respectively, compared with wakefulness. However, collapsibility indices decreased 29.1%, 23.2%, 21.4%, and 34.1% at each level with mandibular advancement. Mandibular advancement increases oropharyngeal diameter and decreases oropharyngeal collapsibility during midazolam-induced sleep respiration at the retropalatal as well as the retroglossal region in most patients with OSA.

Evaluation of the upper airway measurements by multi-slice CT before and after operations in obstructive sleep apnea syndrome patients

Objective To evaluate the changes of the upper airway of the patients with obstructive sleep apnea syndrome (OSAS) before and after operations and to know the effects of operations by MSCT. Methods The upper airway dimensions of 26 patients with OSAS were measured on multiplanar reformatted (MPR), curved-planar reformatted (CPR), volume rendering(VR) images of 16-slice spiral CT. The measurements include the anteroposterior calibres and the areas on the reformatted axial images on the pharyngeal cavity levels, the calibres and the minimum areas in retropalatal and retroglossal regions, the areas of the soft palate and uvula on the reformatted sagittal view with maximum thickness, the maximum wall thickness of the right and left the upper airway on the coronary images, the volume of the upper airway before and after the operations. The measurements were correlated with the polysomnography (PSG) records. The data were analyzed paired-samples t-test and Pearson correlations. Results By comparison, the anteroposterior calibres and the cross-sectional areas on the reformatted axial view of the lower retropalatal region (slice 4) of the upper airway increased significantly after operations. The anteroposterior diameter increased from 5. 9 mm before operations to 12.8 mm after operations, where t = - 5.506, P < 0.05. The areas increased from 51.0 mm2 before operations to 275.0 mm2 after operations, where t = -5.011, P <0.05. In the higher retropalatal region (shce 2) of the upper airway, the anteroposterior diameter decresased from 14.8 mm before operations to 9.2 mm after operations, where t = 2.867, P < 0.05. The areas decreased from 241.0 mm2 before operations to 128.0 mm2 after operations, where t = 3.087, P < 0.05. The anteroposterior calibres of retroglossal region (slice 7) decreased from 12.7 mm before operations to 10.3 mm after operations,where t = 3.718, P <0.05. The L-R calibres and the minimum areas of of retropalatal increased significantly from 6.4 mm, 33.0 mm2 before operation to 10.9 mm, 76. 0 mm2 after operation, where t = -3.413, -2. 216, respectively and P < 0.05. Of the 9 cases whose apnea and hypopnea index (AHI) ≤5 events/hour after operations, the minimum areas of retropalatal region, the anterio-posterior diameter, L-R calibres increased significantly. The areas increased from 41.0 mm2 before operations to 76.0 mm2 after operations, were t = -4. 932, P <0.05. The anteroposterior calibres increased from 4.6 mm before operations to 6.6 mm after operations, where t = - 7. 308, P < 0.05. The L-R calibres increased from 8.3 mm before operations to 13.6 mm after operations, where t = - 4.320, P < 0.05. Conclusions MPR、CPR、VR of MSCT can evaluate the not only the morphology but the function changes of the upper airways on the OSAS patients. The increasing of the minimum cross-sectional area may be one of the important indications for evaluating operations. The narrowing of the higher retropalatal region of the upper airway after operations should be an alert to the clinicians. Key words: Sleep apnea syndrome; Airway obstruction; Tomography, X-ray computed; Image processing computer-assisted

Validation of computational fluid dynamics methodology used for human upper airway flow simulations

An anatomically accurate human upper airway model was constructed from multiple magnetic resonance imaging axial scans. This model was used to conduct detailed Computational Fluid Dynamics (CFD) simulations during expiration, to investigate the fluid flow in the airway regions where obstruction could occur. An identical physical model of the same airway was built using stereo lithography. Pressure and velocity measurements were conducted in the physical model. Both simulations and experiments were performed at a peak expiratory flow rate of 200L/min. Several different numerical approaches within the FLUENT commercial software framework were used in the simulations; unsteady Large Eddy Simulation (LES), steady Reynolds-Averaged Navier-Stokes (RANS) with two-equation turbulence models (i.e. k−ε, standard k−ω, and k−ω Shear Stress Transport (SST)) and with one-equation Spalart–Allmaras model. The CFD predictions of the average wall static pressures at different locations along the airway wall were favorably compared with the experimental data. Among all the approaches, standard k−ω turbulence model resulted in the best agreement with the static pressure measurements, with an average error of ∼20% over all ports. The highest positive pressures were observed in the retroglossal regions below the epiglottis, while the lowest negative pressures were recorded in the retropalatal region. The latter is a result of the airflow acceleration in the narrow retropalatal region. The largest pressure drop was observed at the tip of the soft palate. This location has the smallest cross section of the airway. The good agreement between the computations and the experimental results suggest that CFD simulations can be used to accurately compute aerodynamic flow characteristics of the upper airway.

Cervical CT derived neck fat tissue distribution differences in Japanese males and females and its effect on retroglossal and retropalatal airway volume

The objective of this study was to investigate the difference of neck fat tissue distribution by sex and its correlation with retropalatal and retroglossal airway. A total of 38 consecutive patients (male: 19; female: 19) who received a CT scan were compared in the retroglossal region and at the narrowest cross section of the airway. Retroglossal fat tissue volume (FV) was segmented with Amira software and separated into subcutaneous and internal fat volume (SFV, IFV). These volumes were normalized by retroglossal neck volume (NV). Men had 51.9% more IFV/NV and 64.4% less SFV/NV compared with women. Age-adjusted BMI was negatively correlated with retroglossal airway volume (normalized by NV) and with the lateral width of the smallest cross-section airway (LW) in females. In males the IFV/NV was negatively correlated with LW, after adjusting for BMI and age. Upper airway collapsibility analysis is needed to rule out whether increased BMI or IFV causes an increase in airway collapsibility.

Avaliação da obstrução da via aérea superior através da videonasofaringoscopia: comparação da manobra de Müller com o sono induzido

A nasofaringoscopia com realização de Manobra de Müller é freqüentemente utilizada para determinar o local da obstrução na via aérea superior. No entanto, sua utilidade é controversa, uma vez que é realizada com o paciente acordado e pode não reproduzir os fenômenos obstrutivos que ocorrem durante o sono. OBJETIVOS: Comparar o grau de obstrução faríngea nas regiões retropalatal e retrolingual que ocorrem durante a manobra de Müller com aquelas que ocorrem durante o sono induzido. MATERIAL E MÉTODOS: Estudo prospectivo de 8 pacientes (3 homens e 5 mulheres) com idade (média ±desvio padrão) de 48,6 ± 9,2 anos de idade através de videonasofaringoscopia durante a manobra de Müller e durante o sono induzido por midazolam endovenoso. RESULTADOS: Observamos obstrução retropalatal similar durante a manobra de Müller e sono induzido (média + desvio padrão 3,13 + 0,99 e 2,75 + 0,46, respectivamente, p= 0,234). Em contraste, a obstrução retrolingual foi significantemente menor durante a manobra de Müller (média + desvio padrão 0,63 + 1,06 e 2,63 + 1,30, respectivamente, p= 0,005). CONCLUSÃO: O método do sono induzido foi seguro sob as condições de monitorização adotadas, tendo detectado maior ocorrência de colapso retrolingual do que a manobra de Müller.

Evaluation of airway obstruction by nasopharyngoscopy: comparison of the Müller maneuver versus induced sleep

SummaryThe use of nasopharyngoscopy during the application of intrathoracic pressure (Müller maneuver) is frequently employed to establish the site of upper airway obstruction. The Müller maneuver, however, is used when the patient is awake and therefore may not correlate with obstruction occurring during sleep. Aim: to compare the degree of pharyngeal obstruction in the retropalatal and retroglossal regions during the Müller maneuver versus induced sleep using nasopharyngoscopy. Study design: A prospective, case series study. Material and methods: Eight patients (three males, five females), with a mean age of 48.6 +/- 9,2 year, underwent nasopharyngoscopy to assess airway anatomy and funciton during the Müller maneuver while awake and during sleep induced by drip infusion of Midazolam. Results: Retropalatal obstruction was similar during the Müller maneuver and sleep (mean + standard deviation = 3.13 +/- 0.99 and 2.75 +/- 0.46, p= 0.234). Retroglossal obstruction was significantly lower during Müller maneuver compared to sleep (mean + standard deviation 0.63 +/- 1.06 and 2.63 +/- 1.30, respectively, p= 0.005). Conclusion: The sleep inducing method was safe under the monitored conditions of this study, and detected more retroglossal obstruction than the Müller maneuver.

Three-Dimensional Changes in Upper Airways of Patients With Obstructive Sleep Apnea Following Maxillomandibular Advancement

The purpose of this study was to analyze the morphologic changes of the airway in obstructive sleep apnea (OSA) patients by helical computed tomography (CT) scanning following maxillomandibular advancement (MMA) surgery. Twenty consecutive OSA patients treated with MMA from 2000 to 2003 at the University of Alabama at Birmingham Hospital and diagnosed by polysomnography (PSG) were included in this study. The criteria for this study were MMA surgery, pre- and postoperative helical CT scan, and PSG. Lateral (LAT) and anterioposterior (AP) airway dimensions were measured from the level of the hard palate to the hyoid using helical CT scans. There was enlargement of LAT and AP diameters for all patients at all levels. LAT dimensions were enhanced greater than AP in the retroglossal region. MMA results in significant increase in both AP and LAT airway dimensions.

Study of low dose and dynamic multi-slice CT about obstructive sleep apnea syndrome in sleeping

Objective To perform Low dose dynamic MSCT( multi-slice CT) in sleeping obstructive sleep apnea syndrome ( OSAS) patients correcting the imprecise measure values in waking state, and to exactly analyse the location and extension of the dynamic changes about the condition. Methods Sixteen OSAS patients were scanned both in waking and naturally sleeping period ( end phase of inspiration and expiration). Measured at the narrowest part of the retropalatal ( RP) and retroglossal ( RG) and 5 mm under the tip of epiglottis at the epiglottal ( EPG) at the end period of inspiration in sleeping, respectively, and compared the accurate pos(?)on of the narrowest or occlusive level in 3 phases. All patients were also scanned using cine mode at the narrowest level at the end period of inspiration in sleeping to show the pharyngeal cavity changes during sleep. Results The smallest XSA of RP region (Mw = 47. 50 mm2 ,Me =73. 00 mm2 , Mi =2. 00 mm2 ;Zwe =2. 897,Pwe =0. 003 ;Zwi =4. 192,Pwi 0. 01 ;Zie =4. 538,Pie 0. 01) were statistical difference among three phases, furthermore, the AP(the anteroposterior diameter) of RP(MW = 8. 00 mm, Me=9. 50 mm,Mi = 1. 50 mm;Zwe=l. 933,Pwe =0. 056;Zwi =3. 720,Pwi 0. 01 ;Zie =4. 230,Pie 0. 01) and LR(the left-right diameter) of RP region (Mw =8.00 mm,Me =9.00 mm,Mi =1.00 mm;Zwe =1.210, Pwe =0. 246;Zwi =4. 203,Pwi 0.01;Zie =4.557,Pie 0. 01) and the volum of RP (Mw =4.00 mm3, Me= 5. 50 mm3 ,Mi = 1.50 mm3;Zwe = 1.576,Pwe =0. 125;Zwi =3.532,Pwi 0.01;Zie = 4.077,Pie 0. 01 ) and the distance between the posterior wall and anterior vertebra of RP (Mw =7.00 mm, Me = 6. 00 mm, Mi =10. 50 mm;Zwe =0.557,Pwe =0.603;Zwi=2.541,Pwi =0.011;Zie = 2.852,Pie =0.004) and RG regions (Mw=5.00 mm,Me =3.00 mm,Mi =9.50 mm;Zwe =0.747,Pwe =0.482;Zwi =2.657, Pwi =0. 007 ;Zie = 3. 075, Pie = 0. 001 ) , were different between inspiration and expiration of sleeping or awake. The dynamic cine CT scan during sleeping could show phaiyngeal change, clearly. Conclusion At the end period of inspiration in sleeping, the location of narrow or obstructive of airway is the most precise and sensitive and the false negative at the waking could be obviously reduced. Low dose MSCT scan reduced exposure and expense.

The Shape of the Epiglottis Reflects Improvement in Upper Airway Obstruction after Weight Loss

Obstructive sleep apnea (OSA) is a sleep disorder characterized by recurrent episodes of closure of the upper airway during sleep, and is highly prevalent among overweight individuals. A significant percentage of patients with OSA remain undiagnosed. This condition creates chronic nighttime hypoxemia that can result in significant complications including systemic and pulmonary hypertension, cor pulmonale, and stroke. Polysomnography is still the most widely used method for diagnosing OSA. Studies have shown that in the majority of patients with OSA the airway obstruction involves the retroglossal region. Upon performing esophagogastroduodenoscopy on patients with a wide range of body mass indices (from 21 to 63), we noticed a gradual increase in the concavity of the posterior epiglottal surface as the BMI increases. Upon following some of the patients who underwent laparoscopic gastric banding and lost significant weight, we noticed a dramatic change in the shape of the epiglottis. This reflects a relief in the pressure on the epiglottis created by the collapsing airways in periods of apnea. Thus, the deformity in the shape of the epiglottis reflects the chronic airway collapse in obese patients, and improvement in this deformity after weight loss indicates a relief of the chronic upper airway obstruction.

A Novel Volumetric Magnetic Resonance Imaging Paradigm to Study Upper Airway Anatomy

We utilized novel three-dimensional volumetric analysis techniques with magnetic resonance imaging (MRI) to study the upper airway and surrounding soft-tissue structures. These MRI techniques allowed us to objectively quantify the volume of the tongue, soft palate, parapharyngeal fat pads, and lateral pharyngeal walls. We first validated our volumetric imaging techniques on a phantom and then demonstrated that our results were reliable and reproducible in normal subjects who did not lose weight. Finally, we studied 12 obese, nonapneic women during wakefulness before and after weight loss. We hypothesized that our novel magnetic-resonance computer-reconstruction techniques would allow us to detect small reductions in the volume of the tongue, soft palate, lateral pharyngeal walls, and parapharyngeal fat pads and increases in the volume of the upper airway with weight loss. University medical center. Normal controls and 12 obese nonapneic women. Weight loss. Following a mean 17.1+/-8.62 kg (17.3%) reduction in weight, upper airway volume increased (p = 0.06) in both the retropalatal and retroglossal regions. This increase in upper airway volume was mediated by significant reductions in the volume of the lateral pharyngeal wall (p = 0.0001) and parapharyngeal fat pads (p = 0.001). However, the volume of the tongue (p = 0.35) and soft palate (p = 0.39) were not reduced significantly with weight loss. These data indicate that volumetric MRI is a powerful tool to study anatomic changes in the upper airway and surrounding soft-tissue structures and is sensitive enough to detect changes in these structures.

Relationship between cephalometric characteristics and obstructive sites in obstructive sleep apnea syndrome.

Patients with obstructive sleep apnea syndrome (OSAS) have characteristic dentofacial features, but the sites of obstruction differ greatly. The purpose of this study was to investigate the dentofacial characteristics of patients with OSAS with respect to the obstructive sites. The subjects consisted of 30 Japanese men with OSAS divided into 3 groups of 10 patients each. One group had obstruction at the retropalatal and retroglossal region (Rp + Rg group), a second group had obstruction at the retropalatal region (Rp group), and a third group had obstruction due to tonsillar hypertrophy (tonsillar hypertrophy group). To identify the Rp + Rg and Rp groups, dynamic magnetic resonance imaging (MRI) was used. To identify the tonsillar hypertrophy group, Mackenzie's classification, axial MRI, and the weight of the tonsils were used. A control group was composed of 10 Japanese men showing no symptoms suggestive of OSAS. Lateral cephalometric radiographs were obtained for all of the subjects, and analysis of variance was performed for the 46 cephalometric parameters. Among the many dentofacial characteristics of OSAS patients, the tendencies for retrognathia, micrognathia, and skeletal Class II were strongest in the Rp + Rg group and somewhat strong in the Rp group. The presence of a long soft palate was dominant in the Rp group, whereas the tendency for a long face was dominant in the tonsillar hypertrophy group. All of the groups shared the characteristic of having an inferior position of the hyoid bone. Based on the results of the current study, we conclude that many features of OSAS are specifically related to each obstructive type of OSAS.

Airway assessment by volumetric computed tomography in snorers and subjects with obstructive sleep apnea in a Far-East Asian population (Chinese).

To evaluate the airway dimension of simple snorers and subjects with obstructive sleep apnea (OSA) in a Far-East Asian population (Chinese). Prospective study of 117 near-consecutive patients evaluated for snoring and possible OSA from January 1998 to December 1998 in a sleep laboratory. Overnight polysomnography (PSG) was performed on all patients and the sleep parameters, including respiratory disturbance index (RDI), snoring index, minimal oxygen saturation (min O2), percentage of slow wave sleep (SWS), and rapid eye movement (REM) were recorded. Three-dimensional computerized tomography (CT) during awake periods was performed. The anteroposterior (AP) and the lateral distance of the retropalatal (RP) region in the oropharynx, the smallest area of RP, and retroglossal (RG) regions, and the total volume of the oropharynx were measured. Ninety-eight patients were diagnosed with OSA (mean RDI, 41.48 +/- 26.45 events per hour; min O2, 72.82 +/- 12.86%), whereas 19 were simple snorers. The AP and the lateral distance of the RP region, as well as the smallest area of the RP region, are significantly smaller in subjects with OSA. However, no differences in the RG region and the total volume of the oropharynx were found between the two groups. Linear regression analysis demonstrated that the lateral dimension and the smallest RP area in overweight subjects inversely correlated with the RDI, but only the AP dimension of the RP area was found to have an inverse correlation with the RDI in the underweight subjects. In Far-East Asians (Chinese), the RP airway was found to be the primary site of narrowing in subjects with OSA, and the narrowest RP area was inversely correlated with RDI. Furthermore, weight may influence the pattern of RP narrowing by contributing to lateral collapse.

Effects of head and body position on two- and three-dimensional configurations of the upper airway.

This study was carried out to test the hypothesis that changes in head/body position induce changes in upper-airway dimensions. Contiguous images were obtained by means of magnetic resonance imaging in normal awake subjects during nasal breathing. A statistical analysis was made on 5 consecutive slices, including the most constricted sites in both the retropalatal and retroglossal regions. Dimensional changes in the upper airway in association with changes in head/body position were evaluated. In the retropalatal region, there was a significant decrease in the lateral dimension in the lateral recumbent position compared with that in the supine position. The cross-sectional area in the retroglossal region was significantly increased in both the "supine with the head rotated" and "lateral recumbent" positions. This change was accompanied by significant volumetric changes in the retroglossal region. Thus, sleeping with the head rotated may be effective for improving upper-airway obstruction.

Quantitative evaluation of the upper airway during nasopharyngoscopy with the müller maneuver

To quantitatively examine changes in the upper airway caliber of normal subjects at graded negative inspiratory pressures generated during nasopharyngoscopy with a Müller maneuver. Eighteen normal subjects prospectively underwent nasopharyngoscopy with Müller maneuvers. Subjects performed graded and maximal effort Müller maneuvers while sitting upright, and maximal-effort Müller maneuvers in the supine position. Two regions of the upper airway--the retropalatal and retroglossal--were examined. Images from the endoscopic examination were objectively analyzed by adjusting manually traced airway contours using full-width, half-maximum edge detection algorithm software. The adjusted tracings' area and dimensions through the airway centroid were measured. Müller maneuvers performed at -40 cm H2O resulted in a 64%+/-17% (P = .0001) reduction in upper airway area that consisted of a 51%+/-20% (P = .0001) reduction in the lateral dimension and a 21%+/-24% (P = .0026) reduction in antero-posterior dimension. Müller maneuvers in the retroglossal region did not significantly reduce airway area (P = .575), but demonstrated an altered airway conformation that consisted of lateral narrowing and an increase in antero-posterior dimension. Changes in body position did not result in significant differences in either airway caliber or airway dimension. Airway caliber during forced inspiration is mediated primarily through changes in the lateral pharyngeal walls. This study has also shown that antero-posterior and lateral airway structures are largely independent in their response to Müller maneuvers. Similarly, the retropalatal and retroglossal regions of the upper airway respond differently to forced negative intraluminal pressure.

Upper airway and soft tissue structural changes induced by CPAP in normal subjects.

Nasal continuous positive airway pressure (CPAP) is the treatment of choice for adults with obstructive sleep apnea. CPAP is known to increase upper airway size; however, the direct effects of CPAP on soft tissue structures surrounding the upper airway are less well understood. Magnetic resonance imaging was used to study the effect of incremental levels (0, 5, 10, and 15 cm H2O) of CPAP on the upper airway and surrounding soft tissue structures in 10 normal subjects. Progressive increases in CPAP resulted in the following major findings: (1) airway volume and airway area (measured at several different locations [midregion, minimal, maximal]) within the retropalatal and retroglossal regions increased; (2) lateral airway dimensional changes were greater than anterior-posterior changes; (3) lateral upper airway soft tissue structural changes were significantly greater than anterior-posterior changes; (4) lateral pharyngeal wall thickness decreased and the distance between the lateral parapharyngeal fat pads increased. An inverse relationship was demonstrated between CPAP level and pharyngeal wall thickness; (5) minimal changes were noted in the soft palate and tongue. These data suggest that the lateral pharyngeal walls are more "compliant" than the soft palate and tongue. This investigation provides further evidence that the lateral pharyngeal walls play an important role in mediating upper airway caliber.

Dynamic upper airway imaging during awake respiration in normal subjects and patients with sleep disordered breathing.

The effects of respiration on upper airway caliber were studied using cine computed tomography (CT) in 15 normal subjects, 14 snorer/mildly apneic subjects, and 13 patients with obstructive sleep apnea. All subjects were scanned in the supine position during awake nasal breathing. Eight-millimeter-thick axial slices were obtained at four anatomic levels from the nasopharynx to the retroglossal region every 0.4 s during a respiratory cycle. Tidal volume measured from an integrated pneumotachograph signal was correlated with slice acquisition during inspiration and expiration to generate loops comparing upper airway area and tidal volume. In all three subject groups and at all anatomic levels studied, there were significant dimensional changes in upper airway caliber during the respiratory cycle. The major findings in this investigation include: (1) the upper airway was significantly smaller in apneic than normal subjects, especially at the retropalatal low and retroglossal anatomic levels; in apneic patients the airway had an anterior-posterior configuration unlike the normal airway, which had a horizontal configuration with the major axis in the lateral direction; (2) in all three subject groups, little airway narrowing occurred in inspiration, suggesting that the action of the upper airway dilator muscles balanced the effects of negative intraluminal pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic imaging of the upper airway during respiration in normal subjects

The present study was conducted to determine the effects of quiet respiration on upper airway caliber in 15 normal subjects by using cine computed tomography. The cine computed tomography (Imatron) scanner was programmed to obtain 8-mm-thick axial slices every 0.4 s during inspiration and expiration at four anatomic levels, from the nasopharynx to the retroglossal region. Airflow (pneumotachograph) was measured, and tidal volume was obtained by integration. Upper airway area, determined by an objective edge detection algorithm, was plotted as a function of tidal volume to generate a loop describing upper airway area changes at each level during a respiratory cycle. The results demonstrate a 17% change in airway size across all anatomic levels during respiration. The maximum upper airway cross-sectional area at all four anatomic levels was significantly greater during expiration than during inspiration. Other major findings include 1) upper airway cross-sectional area decreases slightly during early inspiration, enlarges toward end inspiration, and is larger at end inspiration than at the beginning of inspiration; 2) upper airway cross-sectional area enlarges from end inspiration to the first point in expiration; the airway enlarges further, reaching its maximum early in expiration, and then narrows toward end expiration; and 3) the changes in upper airway dimensions during resting tidal breathing are greater in the lateral than in the anteroposterior direction. The data suggest that during inspiration, the action of negative intraluminal pressure may be largely balanced by the action of the upper airway dilator muscles, whereas during expiration, positive intraluminal pressure produces expansion of the upper airway.