Pharyngeal Volume Research Articles

Is the difference in the volume of the pharyngeal space, as measured by acoustic pharyngometry, before and after tonsillectomy proportional to the volume of the excised tonsils?

OBJECTIVE:Adenotonsillectomy is recognized as an effective therapy for snoring and sleep disorders in children. It is important to understand whether adenotonsillectomy significantly increases the volume of the pharyngeal space. The goal of this study was to evaluate the change in oropharyngeal volume after adenotonsillectomy and the correlation of this change with the objective volume of the tonsils and body mass index.METHODS:We included 27 subjects (14 males) with snoring caused by tonsil and adenoid hypertrophy. The mean age of the subjects was 7.92 (±2.52) years. Children with craniofacial malformations or neuromuscular diseases or syndromes were excluded. The parents/caregivers answered an adapted questionnaire regarding sleep-disordered breathing. All patients were subjected to weight and height measurements and body mass index was calculated. The subjects underwent pharyngometry before and after adenotonsillectomy and the volume of both excised tonsils together was measured in cm3 in the operating room.RESULTS:Pharyngometric analysis showed that the mean pharyngeal volume was 28.63 (±5.57) cm3 before surgery and 31.23 (±6.76) cm3 after surgery; the volume of the oropharynx was significantly increased post-surgery (p=0.015, Wilcoxon test). No correlation was found between the objective tonsil volume and the post-surgical volume increase (p=0.6885). There was a fair correlation between the oropharyngeal volume and body mass index (p=0.0224).CONCLUSION:Adenotonsillectomy increases the volume of the pharyngeal space, but this increase does not correlate with the objective tonsil size. Furthermore, greater BMI was associated with a smaller increase in the pharyngeal volume. Oropharyngeal structures and craniofacial morphology may also play a role in the increase in oropharyngeal volume.

Changes in Upper Airway Volume in Edentulous Obstructive Sleep Apnea Patients Treated with Modified Mandibular Advancement Device.

This study was an attempt to verify the utility of complete dentures modified as a mandibular advancement device (MAD) in effecting expansion in pharyngeal volume to treat obstructive sleep apnea (OSA) in edentulous patients. The sample consisted of 17 patients (12 male, 5 female, average age 61 ± 4 years; BMI, 22 ± 5; apnea hypopnea index [AHI] 15 to 30). All patients had worn complete dentures for at least 1 year; all patients had the dentures modified to a MAD. Five variables were assessed preoperatively and 6 months after wearing the modified MADs. These variables were: sleep efficiency, AHI, oxygen desaturation events/hr., mean oxygen saturation, snoring index, and airway volume. This assessment was done by subjecting the patients to all-night polysomnography. Without any prosthesis or device in the edentulous patients, the mean velopharyngeal volume was 8.05 ± 0.58 cm(3) , oropharyngeal volume was 2.14 ± 0.38 cm(3) , and hypopharyngeal volume was 3.26 ± 0.78 cm(3) . With complete dentures (unaltered) in the edentulous patients, the mean velopharyngeal, oropharyngeal, and hypopharyngeal volumes were 10.73 ± 0.98 cm(3) , 2.60 ± 0.48 cm(3) , and 4.31 ± 0.89 cm(3) , respectively. There was a statistically significant change in the airway volume following insertion of the complete dentures modified as MADs with velopharyngeal, oropharyngeal, and hypopharyngeal volume recorded as 11.76 ± 1.07 cm(3) , 3.33 ± 0.51 cm(3) , and 4.94 ± 0.83 cm(3) , respectively. From the results obtained in this limited small sample study, it was inferred that the pharyngeal expansion induced by complete dentures modified as MADs effectively reduced symptoms of OSA. Increased volume was most pronounced in the velopharynx region followed by hypopharynx and oropharynx.

Pharyngeal wall floppiness: a novel technique to detect upper airway collapsibility in patients with OSAS.

To measure pharyngeal wall floppiness (PWF) under different pressures, a novel method and technique were introduced in the present study. A prospective clinical study. Forty-seven healthy subjects (32 male; mean age, 37.9 years) and 49 patients with obstructive sleep apnea syndrome (OSAS) (46 male; mean age, 41.45 years) were recruited. The pharyngeal cavity volume was measured by acoustic reflection under positive (10 cm H2O) and negative (-10 cm H2O) pressures. The pharyngeal cavity volume was detected from the segment of 10 to 20 cm from the incisor. Moreover, PWF was calculated from the difference of pharyngeal cavity volumes under positive and negative pressures divided by the sum of the volumes under positive and negative pressures. The measurements were conducted on a group of 7 subjects weekly over 3 consecutive weeks to evaluate test-retest variability. The mean PWF was 0.19 ± 0.11 in healthy subjects and 0.24 ± 0.07 in the OSAS group, with a significant difference (P < .01). There was moderate positive correlation between PWF and age or body mass index in healthy subjects. In the 7 subjects, the mean measured interclass correlation coefficient was 0.9 (P < .05) in 3 consecutive weekly measurements. The OSAS population had greater PWF compared to healthy subjects. The age dependency of PWF in healthy subjects implied which might play important roles in the development of OSAS. This noninvasive and reproducible technique might be a useful tool in OSAS clinical applications.

Area and volume of the pharyngeal airway in surgically treated unilateral cleft lip and palate patient: A cone beam computed tomography study

Background: Area and volume of the pharyngeal airway in surgically treated unilateral cleft lip and palate (UCLP) patient: A cone beam computed tomography (CBCT) study. Context: Surgical repair of cleft causes restriction of maxillary growth and mid face but the effect of this reduced growth on volume of the pharyngeal airway has not been investigated thoroughly. Aims: The aim of the study was to assess the area, volume and smallest cross-sectional area of the pharyngeal airway in individuals with UCLP using CBCT and compare with age and sex matched noncleft controls. Settings and Design: Retrospective study. Materials and Methods: The study was carried out on 20 surgically treated UCLP patients and compared with 40 normal non cleft subjects with Class I skeletal relation within age group of 7-14 years. CBCT image processing and analysis were performed using Dolphin Imaging software (11.7 version premium; Dolphin Imaging and Management Solutions, Chatsworth, Calif) and volumetric rendering was done for airway analysis. Statistical Analysis Used: All statistical analyses were performed with SPSS software (version 15.0J for Windows; SPSS, Inc., Chicago, IL). An independent sample t-test was used to determine the significance of the difference between the means. Results: No significant difference was found in the area and volume of nasopharynx, oropharynx, hypopharynx, total pharyngeal volume (P = 0.86) and minimum axial area (P = 0.69) of the pharynx between the groups. Conclusions: Using CBCT, this study found that there was no significant difference in the pharyngeal area and volume between UCLP and noncleft groups. Further investigations are necessary to clarify the relationship between pharyngeal structure and airway function in patients with CLP.

Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3-dimensional simulation and modeling program

The aims of this study were to use 3-dimensional simulation and modeling programs to evaluate the effects of bimaxillary orthognathic surgical correction of Class III malocclusions on pharyngeal airway space volume, and to compare them with the changes in obstructive sleep apnea measurements from polysomnography. Twenty-five male patients (mean age, 21.6years) with mandibular prognathism were treated with bilateral sagittal split osteotomy and LeFort I advancement. Polysomnography and computed tomography were performed before surgery and 1.4±0.2years after surgery. All computed tomography data were transferred to a computer, and the pharyngeal airway space was segmented using SimPlant OMS (Materialise Medical, Leuven, Belgium) programs. The pretreatment and posttreatment pharyngeal airway space determinants in volumetric, linear distance, and cross-sectional measurements, and polysomnography changes were compared with the paired samples t test. Pearson correlation was used to analyze the association between the computed tomography and polysomnography measurements. The results indicated that setback procedures produce anteroposterior narrowing of the pharyngeal airway space at the oropharyngeal and hypopharyngeal levels and the middle and inferior pharyngeal volumes (P<0.05). In contrast, advancement of the maxilla causes widening of the airway in the nasopharyngeal and retropalatal dimensions and increases the superior pharyngeal volume (P<0.05). Distinctively, bimaxillary orthognathic surgery induces significant increases in the total airway volume and the transverse dimensions of all airway areas (P<0.05). Significant correlations were found between the measurements on the computed tomography scans and crucial polysomnography parameters. Bimaxillary orthognathic surgery for correction of Class III malocclusion caused an increase of the total airway volume and improvement of polysomnography parameters. A proposed treatment plan can be modified according to the risk of potential airway compromise or even to improve it with 3-dimensional imaging techniques and polysomnography.

Upper Airway Collapsibility and OSA: A Novel Method in Detecting Pharyngeal Wall Floppiness

Objectives: Upper airway collapse is the major reason of obstructive sleep apnea (OSA). However, the site and mechanism of the obstruction remains unclear. To measure the pharyngeal wall floppiness under different pressures, a novel method and technique is introduced in the present study. Methods: Forty-seven normal subjects (male: 32; mean age, 37.9 years) and 49 OSA patients (male: 6; mean age, 41.45 years) were recruited in this prospective clinical study. The pharyngeal cavity volumes were measured by means of acoustic reflection under positive (10 cmH2O) and negative (–10 cmH2O) pressures. The pharyngeal wall floppiness was calculated from the difference of pharyngeal cavity volumes under positive and negative pressures divided by the sum of the volumes under different pressures. Results: The pharyngeal wall floppiness was 0.19 ± 0.11 in normal subjects and 0.24 ± 0.07 in OSA group with a significant difference ( P &lt; .01). There was moderate positive correlation between pharyngeal wall floppiness and age or body mass index (BMI) in normal subjects. In OSA patients, the pharyngeal wall floppiness had a weak negative correlation to age, whereas it had moderate positive correlation to sleep apnea severity (apnea-hypopnea index), BMI or neck circumference, respectively. Conclusions: The OSA population had greater pharyngeal wall floppiness. The age dependent of pharyngeal wall floppiness in normal subjects implied that aging might play important roles in the development of OSA. The measurement of pharyngeal wall floppiness could be a useful and valuable parameter in diagnosis of OSA and predicting the adherence in continuous positive airway pressure (CPAP) treatment.

Improved Apnea-Hypopnea Index and Lowest Oxygen Saturation After Maxillomandibular Advancement With or Without Counterclockwise Rotation in Patients With Obstructive Sleep Apnea: A Meta-Analysis

This study investigated whether patients with obstructive sleep apnea (OSA) who undergo maxillomandibular advancement (MMA) with counterclockwise (CCW) rotation compared with those who undergo MMA without CCW rotation have better outcomes. This was a systematic review with meta-analysis. The Medline and Cochrane databaseswere searched for randomized controlled trials using Medical Subject Headings. The predictor variable was operative technique, namely MMA with or without CCW rotation of the maxillofacial complex. The key outcome variables were changes in pre- and postsurgical values of pharyngeal volume measured on computed tomogram or cone-beam computed tomogram and changes in Apnea-Hypopnea Index (AHI) and lowest oxygen saturation (LSAT) values after surgery. Data were subjected to a meta-analysis based on odds ratios (OR) with 95% confidence intervals (CIs) and P values lower than .05 by χ(2) test were considered significant. Twenty-one randomized controlled trials were identified and 4 were assessed for the variables of interest. Postoperative AHI and LSAT measurements showed vast improvement. The sample was not large enough to make a correlation between pharyngeal volume changes and surgical method used. Postoperative parameters included an AHI lower than 5 (OR= 14.9; 95% CI, 2.7-83.5; P= .002), an AHI lower than 20 (OR = 114.8; 95% CI, 23.5-561.1; P <.00001), pooled results of a 50% decrease in the AHI (OR= 6.1; 95% CI, 2.2-17.0; P= .0006), and an increase greater than 90% in LSAT measurements during sleep (OR= 6.0; 95% CI, 1.8-19.9; P= .003). The funnel plot showed no evidence of publication bias. CCW-MMA or MMA in patients with OSA results in a statistically meaningful decrease in postoperative AHI and a statistically meaningful increase in postoperative LSAT.

Upper airway factors that protect against obstructive sleep apnoea in healthy older males.

The prevalence of obstructive sleep apnoea (OSA) increases with age, yet the risk factors for OSA in older people remain poorly understood. This study aimed to define the age-related changes in upper airway morphology in carefully matched groups of healthy older (>60 years, n=11) and younger (<40 years, n=14) males, using direct (magnetic resonance imaging (MRI)) and indirect (acoustic reflection) imaging. The median (interquartile range) combined retropalatal and retroglossal pharyngeal length was greater in older than in younger males (older 8.8 (7.8-9.0) cm, younger 7.8 (7.0-8.3) cm; p=0.03), as was the soft palate cross-sectional area (older 43.1 (36.0-48.8) cm(2), younger 35.3 (30.5-40.5) cm(2); p=0.03), parapharyngeal fat pad diameter (older 1.7 (1.4-2.2) cm, younger 1.2 (1.0-1.8) cm; p=0.03) and cross-sectional area of the fat pads (older 13.8 (9.1-17.1) cm(2); younger 7.4 (5.9-13.0) cm(2); p=0.02) as measured by MRI. Using acoustic reflection, pharyngeal calibre (older 4.8 (3.8-6.6) cm(2), younger 3.4 (2.8-4.6) cm(2); p=0.03), pharyngeal volume (older 35.1 (30.9-55.4) cm(3), younger 27.2 (22.7-44.2) cm(3); p=0.04) and glottis area (older 2.7 (2.1-3.9) cm(2), younger 1.3 (1.1-1.9) cm(2); p=0.003) were also larger in older participants compared with younger participants. There was no difference in craniofacial measures between groups, including volumetric data and hyoid bone position. The larger pharyngeal calibre observed in older males may be compensating for an age-related enlargement in pharyngeal soft tissue that predisposes to OSA.

Upper Airway Fat Tissue Distribution in Subjects With Obstructive Sleep Apnea and Its Effect on Retropalatal Mechanical Loads

To validate the hypothesis that fat tissue accumulation adjacent to the upper airway contributes to a predisposition to obstructive sleep apnea (OSA), irrespective of body mass index (BMI), as well as investigate the effect of the volume of fat tissue on pharyngeal mechanical loads. Fourteen subjects and 14 controls were enrolled in this study. Pharyngeal anatomy (the fat tissue volume in the retropalatal region and retroglossal region) were evaluated using magnetic resonance imaging. Whether the subjects had a segmental closing pressure higher than atmospheric pressure was determined by pharyngoscopy under general anesthesia. The difference in fat tissue distribution between subjects with OSA and BMI-matched controls was investigated. Fat tissue distributions in subjects with positive or negative segmental closing pressure were also compared. Significant differences occurred between controls and subjects with OSA in volumes of parapharyngeal fat pad (P = .001), fat of soft palate (P = .01), as well as proportion of the parapharyngeal fat pad to the volume of total lateral pharyngeal soft tissues (P = .004). The volume of pharyngeal cavity, neck circumference, and volume of subcutaneous fat tissues were not significantly different statistically. Volume of fat in soft palate (odds ratio 5.893) and parapharyngeal fat pad in retropalatal and retroglossal region (odds ratios 1.781 and 1.845) were significant predictors of OSA. The volume of fat in the soft palate (P = .003) and parapharyngeal fat pad (P = .002) was higher in participants with positive retropalatal closing pressure; participants with positive retroglossal closing pressure had increased volumes of the tongue (P = .02) and the parapharyngeal fat pad (P = .004). Patients with OSA have more fat tissue adjacent to the pharyngeal cavity than BMI-matched controls. Fats deposited around the upper airway may contribute to the collapsibility of retropalatal and retroglossal airway in both patients and controls.

Evaluation of pharyngeal airway space amongst different skeletal patterns

The aim of the present study was to evaluate the dimensions of the pharyngeal airway space (PAS) in awake, upright children with different anteroposterior skeletal patterns using cone beam computed tomography (CBCT). The volume, area, minimum axial area and seven linear measurements of PAS were obtained from the CBCT images of 50 children (mean age 9.16 years). The patients were divided in two groups according to the ANB angle (group I 2°≤ANB≤5°; group II ANB>5°). Means and standard deviations of each variable were compared and correlated using independent t-test and Pearson's correlation test. There were statistically significant differences in the following parameters: angle formed by the intersection between NA and NB lines (p<0.001), angle formed by the intersection between SN and NB lines (p<0.05), Minimal pharyngeal airway space between the uvula and the posterior pharyngeal wall (p<0.05), airway volume (p<0.01), airway area (p<0.01) and minimum axial area (p<0.05). The anteroposterior cephalometric variable SNB had positive correlation with the variables PAS-UP (p<0.01), Minimal pharyngeal airway space between the uvula tip and the posterior pharyngeal wall (p<0.05), Pharyngeal airway space on mandibular line (p<0.05), Minimal pharyngeal airway space between the back of the tongue and the posterior pharyngeal wall (p<0.05), volume airway (p<0.05), airway area (p<0.05) and minimum axial area (p<0.05). The vertical cephalometric variables angle formed by the intersection between SN and GoGn lines (p<0.05) and angle formed by the intersection between FH and mandible plane (p<0.05) showed negative correlation with PAS-UT. These results showed that PAS was statistically larger in group I than group II, indicating that the dimensions of the PAS are affected by different anteroposterior skeletal patterns.

Tonsil volume, tonsil grade and obstructive sleep apnea: is there any meaningful correlation?

OBJECTIVES:The aims of this study were to evaluate the correlation between oropharyngeal examination and objective palatine tonsil volume in snoring adults and verify the influence of the oropharyngeal anatomy, body mass index, age, and severity of obstructive sleep apnea on actual tonsil volume. In addition, we aimed to assess the influence of tonsil size on obstructive sleep apnea in adults.INTRODUCTION:Pharyngeal wall geometry is often altered in adults who have obstructive sleep apnea, and this might influence the findings of the oropharyngeal examination that, in turn, are the key factors when considering surgical management for this condition. Furthermore, the correlation between the actual tonsil volume and the severity of obstructive sleep apnea in adults is currently unknown.METHODS:We prospectively studied 130 patients with obstructive sleep apnea or primary snoring who underwent pharyngeal surgery with intraoperative measurement of tonsil volume. We compared tonsil volume with preoperative polysomnography, oropharyngeal examination, and anthropometric data.RESULTS:We found a significant correlation between actual tonsil volume and subjective tonsil grade. We also found a significant correlation between tonsil volume and the apnea-hypopnea index. Using a multivariate linear regression model, tonsil volume was found to be significantly correlated with age, body mass index, and oropharyngeal examination, but not with polysomnography. Clinically, only the rare tonsil grade IV was indicative of more severe obstructive sleep apnea.CONCLUSIONS:There is a strong correlation between clinical tonsil grade and objective tonsil volume in snoring adults, and this correlation exists regardless of the presence or severity of obstructive sleep apnea. Pharyngeal tissue volume likely reflects the body mass index rather than obstructive sleep apnea severity.

Influence of tongue muscle contraction and transmural pressure on nasopharyngeal geometry in the rat

The mammalian pharynx is a hollow muscular tube that participates in ingestion and respiration, and its size, shape, and stiffness can be altered by contraction of skeletal muscles that lie inside or outside of its walls. MRI was used to determine the interaction between pharyngeal pressure and selective stimulation of extrinsic tongue muscles on the shape of the rat nasopharynx. Pressure (-9, -6, -3, 3, 6, and 9 cmH₂O) was applied randomly to the isolated pharyngeal airway of anesthetized rats that were positioned in a 4.7-T MRI scanner. The anterior-posterior (AP) and lateral diameters of the nasopharynx were measured in eight axial slices at each level of pressure, with and without bilateral hypoglossal nerve stimulation (0.1-ms pulse, 1/3 maximal force, 80 Hz). The rat nasopharynx is nearly circular, and positive pharyngeal pressure caused similar expansion of AP and lateral diameters; as a result, airway shape (ratio of lateral to AP diameter) remained constant. Negative pressure did not change AP or lateral diameter significantly, suggesting that a negative pressure reflex activated the tongue or other pharyngeal muscles. Stimulation of tongue protrudor muscles alone or coactivation of protrudor and retractor muscles caused greater AP than lateral expansion, making the nasopharynx slightly more elliptical, with the long axis in the AP direction. These effects tended to be more pronounced at negative pharyngeal pressures and greater in the caudal than rostral nasopharynx. These data show that stimulation of rodent tongue muscles can adjust pharyngeal shape, extending previous work showing that tongue muscle contraction alters pharyngeal compliance and volume, and provide physiological insight that can be applied to the treatment of obstructive sleep apnea.

Atrophy among Mucosa-Only versus Muscular Mucosa Superiorly Based Pharyngeal Flaps: A Pilot Animal Study

Velopharyngeal insufficiency is frequently managed surgically via the superiorly based pharyngeal flap procedure. The flap used in this procedure traditionally consists of both mucosa and muscle. Although muscle is included to potentially increase survival and tissue bulk, its inclusion may result in postoperative dysfunction of pharyngeal sidewall motion. Although the benefits of pharyngeal flap surgery are established, the denervated muscular portion of the flap appears to atrophy. The purpose of this study was to evaluate whether a flap consisting entirely of mucosa provides the same tissue bulk as a conventional pharyngeal flap 12 weeks postoperatively. Ten laboratory-grade cats served as direct patient surrogates. Cats were randomized to undergo a superiorly based pharyngeal flap procedure with flaps composed of either both muscle and mucosa (n = 5) or mucosa only (n = 5). Blinded volumetric analysis was performed by three board-certified neuroradiologists using magnetic resonance imaging of the pharynx immediately after surgery and at 4, 8, and 12 weeks. At 12 weeks postoperatively, pharyngeal flaps composed of both mucosa and muscle atrophied to reach volumetric equivalence with mucosa-only flaps. Evaluation of final pharyngeal flap volume demonstrated no statistical differences between the two groups. This study demonstrates equivalent final superiorly based pharyngeal flap tissue bulk for flaps composed of only mucosa when compared with conventional pharyngeal flaps. Thus, the mucosa-only pharyngeal flap may yield similar outcomes while potentially providing for an earlier return of normal pharyngeal function.

Pharyngeal articulation in the production of voiced and voiceless fricatives

A structural magnetic resonance imaging study has revealed that pharyngeal articulation varies considerably with voicing during the production of English fricatives. In a study of four speakers of American English, pharyngeal volume was generally found to be greater during the production of sustained voiced fricatives, compared to voiceless equivalents. Though pharyngeal expansion is expected for voiced stops, it is more surprising for voiced fricatives. For three speakers, all four voiced oral fricatives were produced with a larger pharynx than that used during the production of the voiceless fricative at the same place of articulation. For one speaker, pharyngeal volume during the production of voiceless labial fricatives was found to be greater, and sibilant pharyngeal volume varied with vocalic context as well as voicing. Pharyngeal expansion was primarily achieved through forward displacement of the anterior and lateral walls of the upper pharynx, but some displacement of the rear pharyngeal wall was also observed. These results suggest that the production of voiced fricatives involves the complex interaction of articulatory constraints from three separate goals: the formation of the appropriate oral constriction, the control of airflow through the constriction so as to achieve frication, and the maintenance of glottal oscillation by attending to transglottal pressure.

Quantification of vocal tract configuration of older children with Down syndrome: A pilot study

Objective To quantify the vocal tract (VT) lumen of older children with Down syndrome using acoustic reflection (AR) technology. Design Comparative study. Setting Vocal tract lab with sound-proof booth. Participants Ten children (4 males and 6 females), aged 9–17 years old diagnosed with Down syndrome. Ten typically developing children (4 males and 6 females) matched for age, gender, and race. Intervention Each participant's vocal tract measurements were obtained by using an Eccovision Acoustic Pharyngometer. Main outcome measures Six vocal tract dimensional parameters (oral length, oral volume, pharyngeal length, pharyngeal volume, total vocal tract length, and total vocal tract volume) from children with Down syndrome and the typically developing children were measured and compared. Results Children with Down syndrome exhibited small oral cavities when compared to control group ( F(1, 18) = 6.55, p = 0.02). They also demonstrated a smaller vocal tract volumes ( F(1, 18) = 2.58, p = 0.13), although the results were not statistically significant at the 0.05 level. Pharyngeal length, pharyngeal volume, and vocal tract length were not significantly different between the two groups. Conclusion Children with Down syndrome had smaller oral cavities, and smaller vocal tract volumes. No significant differences were found for pharyngeal length, pharyngeal volume, and vocal tract length between these two groups.

Three-dimensional Morphological Analyses of Positional Dependence in Patients with Obstructive Sleep Apnea Syndrome

It is generally considered that patients with obstructive sleep apnea syndrome (OSAS) at increased perioperative risk should be placed in nonsupine positions throughout the recovery process; however, not all patients with OSAS show positional dependence. The authors hypothesized that morphological differences exist in three-dimensional (3D) soft tissue and craniofacial structures of the pharyngeal airway between positional and nonpositional OSAS. The subjects of the study were body mass index-matched, age-matched, and apnea hypopnea index-matched positional (n = 10) and nonpositional (n = 10) Japanese OSAS patients and body mass index-matched Japanese control subjects (n = 10). Pharyngeal magnetic resonance imaging and cephalometric radiography were performed during wakefulness. The patients with positional OSAS had a smaller volume of the pharyngeal lateral wall soft tissues, larger maxilla-nasion-mandible angle, and smaller lower facial height than the nonpositional OSAS and the control subjects. The patients with positional OSAS showed a significantly steeper sella-nasion-mandible angle and smaller craniofacial volume than the control subjects. There were no significant differences in tongue volume and 3D pharyngeal anatomical balance between positional and nonpositional OSAS. Multivariate stepwise regression for positional dependence showed that the dominant determinant was the volume of the lateral pharyngeal wall, followed by lower facial height and maxilla-nasion-mandible angle. Patients with positional OSAS have wider airways in the lateral parts, lower facial height, and more backward position of the lower jaw, which may explain differences in the maintenance of pharyngeal airway patency in the lateral sleep position.

Improvement in Sleep Apnea during Nocturnal Peritoneal Dialysis Is Associated with Reduced Airway Congestion and Better Uremic Clearance

Among peritoneal dialysis (PD) patients, nocturnal PD (NPD) is known to improve sleep apnea compared with continuous ambulatory peritoneal dialysis (CAPD), but the contributing factors are unclear. Thirty-eight incident ESRD patients underwent overnight polysomnography (PSG) during NPD and CAPD. Bioelectrical impedance analysis, magnetic resonance imaging of the upper airway, and urea kinetics (Kt/V) during sleep were measured on both occasions. The prevalence of severe sleep apnea (apnea-hypopnea index, AHI > or = 15/h) was 21.1% during NPD, and 42.1% during CAPD. Mean AHI increased from 9.6 +/- 2.7/h during NPD to 21.5 +/- 4.2/h during CAPD. Both obstructive and central apnea worsened after conversion to CAPD. NPD achieved greater reductions in total body water, hydration fraction, and net ultrafiltration than CAPD during sleep. Overnight peritoneal Kt/V and creatinine clearance were lower after conversion. Both peritoneal Kt/V and peritoneal creatinine clearance correlated with AHI, as did their changes after conversion. Volumetric magnetic resonance imaging revealed reduced pharyngeal volumes and cross-sectional area, and tongue enlargement after conversion. Improvement in sleep apnea during NPD versus CAPD is associated with better fluid and uremic clearance and reduced upper airway congestion during sleep.

Airway Changes During Labor and Delivery

Tracheal intubation fails much more often in pregnant than in nonpregnant women, but no prospective studies evaluating airway changes during labor have been reported. The investigators carried out 2 studies of airway changes during labor. The first study utilized the conventional Samsoon modification of the Mallampati score, which is based on visualizing the soft palate, faucial pillars, and uvula. The visibility of these structures depends on the relative capacity of the oropharyngeal cavity and the volume of the base of the tongue. In the second study, upper airway volumes were measured by acoustic reflectometry at the onset and end of labor. This method yields values for the components of the upper airway, oral volume, and pharyngeal volume, and includes the concealed part of the upper airway. The first study, conducted in 61 women, demonstrated a significant increase in airway class from pre-labor to the post-labor phase. The airway increased by one grade after labor in one-third of women and by 2 grades in another 5%. Women who initially had class 4 airways were excluded from the study, but 8 women had a class 4 airway and 22 had a class 3 airway at the end of labor. In the second study, performed on 21 women, oral volume and pharyngeal area and volume decreased significantly after labor and delivery. In neither study did airway changes correlate with the duration of labor or with fluid administration. The investigators believe that the airway must be examined immediately before cesarean delivery is carried out rather than depending solely on data from pre-labor assessment.

Airway Changes During Labor and Delivery

Tracheal intubation fails much more often in pregnant than in nonpregnant women, but no prospective studies evaluating airway changes during labor have been reported. The investigators carried out 2 studies of airway changes during labor. The first study utilized the conventional Samsoon modification of the Mallampati score, which is based on visualizing the soft palate, faucial pillars, and uvula. The visibility of these structures depends on the relative capacity of the oropharyngeal cavity and the volume of the base of the tongue. In the second study, upper airway volumes were measured by acoustic reflectometry at the onset and end of labor. This method yields values for the components of the upper airway, oral volume, and pharyngeal volume, and includes the concealed part of the upper airway. The first study, conducted in 61 women, demonstrated a significant increase in airway class from pre-labor to the post-labor phase. The airway increased by one grade after labor in one-third of women and by 2 grades in another 5%. Women who initially had class 4 airways were excluded from the study, but 8 women had a class 4 airway and 22 had a class 3 airway at the end of labor. In the second study, performed on 21 women, oral volume and pharyngeal area and volume decreased significantly after labor and delivery. In neither study did airway changes correlate with the duration of labor or with fluid administration. The investigators believe that the airway must be examined immediately before cesarean delivery is carried out rather than depending solely on data from pre-labor assessment.

Airway Changes during Labor and Delivery

There are no prospective studies that evaluated airway changes during labor. The purpose of this study was to evaluate airway changes in women undergoing labor and delivery. Two studies were undertaken to evaluate airway changes during labor. The first study used the conventional Samsoon modification of the Mallampati airway class. The airway was photographed at the onset and the end of labor. Women with class 4 airways were excluded from initial participation. In the second study, upper airway volumes were measured using acoustic reflectometry at the onset and the conclusion of labor. Acoustic reflectometry software computed the values for the components of upper airway, oral volume, and pharyngeal volume. In study 1 (n = 61), there was a significant increase in airway class from prelabor to postlabor (P < 0.001). The airway increased one grade higher in 20 (33%) and two grades higher in 3 (5%) after labor. At the end of labor, there were 8 parturients with airway class 4 (P < 0.01) and 30 parturients with airway class 3 or class 4 (P < 0.001). In study 2 (n = 21), there were significant decreases in oral volume (n = 21; P < 0.05), and pharyngeal area (P < 0.05) and volume (P < 0.001) after labor and delivery. No correlation was observed between airway changes during labor and duration of labor, or fluids administered during labor in either study. Airways can change during labor. Therefore, a careful airway evaluation is essential just before administering anesthesia during labor rather than obtaining this information from prelabor data.