Endoscopic evaluation of dynamic narrowing of the pharynx by the Bernouilli effect producing maneuver in patients with obstructive sleep apnea syndrome

Advanced Diagnostic Techniques in Obstructive Sleep Apnea

Optimal surgical and medical management of obstructive sleep apnea requires clinically reliable identification of patterns and sites of upper airway obstruction. A wide variety of modalities have been used to evaluate upper airway obstruction. Drug-induced sleep endoscopy (DISE) and cine MRI are increasingly used to identify upper airway obstruction sites, to characterize airway obstruction patterns, to determine optimum medical and surgical treatment, and to plan individualized surgical management. Here, we provide an overview of the applications of DISE and cine MRI in assessing upper airway obstruction in children and adults with obstructive sleep apnea.

Advanced Diagnostic Techniques in Obstructive Sleep Apnea

Optimal surgical and medical management of obstructive sleep apnea (OSA) requires clinically reliable identification of patterns and sites of upper airway obstruction. A wide variety of modalities has been used to evaluate upper airway obstruction. Drug-induced sleep endoscopy (DISE) and cine MRI are increasingly used to identify upper airway obstruction sites, to characterize airway obstruction patterns, to determine optimum medical and surgical treatment, and to plan individualized surgical management. Here, the authors provide an overview of the applications of DISE and cine MRI in assessing upper airway obstruction in children and adults with OSA.

The relationship between aerodynamic characteristics of the upper airway and severity of obstructive sleep apnea in adults

OBJECTIVE

To investigate the relationship between aerodynamic characteristics of the upper airway and severity of obstructive sleep apnea (OSA) in adults.

METHODS

Ninety-seven adult OSA patients underwent polysomnography and cone beam computed tomography (CBCT). The anatomical and aerodynamic characteristics were measured based on CBCT images and computational fluid dynamics modelling of the upper airway.

RESULTS

After controlling for patients' gender, age, and body mass index (BMI), the maximum velocity during inspiration (In-Vmax) led to the largest increase in the explanatory power of apnea-hypopnea index (AHI) variation. The In-Vmax was closely correlated with the minimum axial area, and their relationship was represented by an inversely proportional fitted curve.

CONCLUSIONS

The In-Vmax was the most relevant to OSA severity, and it could be used to assist in recognizing severe OSA patients and as a primary variable to evaluate treatment outcomes of OSA. The In-Vmax was closely related to the most constricted area of the upper airway.

Effects of respiratory muscle therapy on obstructive sleep apnea: a systematic review and meta-analysis

STUDY OBJECTIVES

The purpose of this study is to conduct a systematic review and meta-analysis evaluating the effects of respiratory muscle therapy (ie, oropharyngeal exercises, speech therapy, breathing exercises, wind musical instruments) compared with control therapy or no treatment in improving apnea-hypopnea index ([AHI] primary outcome), sleepiness, and other polysomnographic outcomes for patients diagnosed with obstructive sleep apnea (OSA).

METHODS

Only randomized controlled trials with a placebo therapy or no treatment searched using PubMed, EMBASE, Cochrane, and Web of Science up to November 2018 were included, and assessment of risk of bias was completed using the Cochrane Handbook.

RESULTS

Nine studies with 394 adults and children diagnosed with mild to severe OSA were included, all assessed at high risk of bias. Eight of the 9 studies measured AHI and showed a weighted average overall AHI improvement of 39.5% versus baselines after respiratory muscle therapy. Based on our meta-analyses in adult studies, respiratory muscle therapy yielded an improvement in AHI of -7.6 events/h (95% confidence interval [CI] = -11.7 to -3.5; P ≤ .001), apnea index of -4.2 events/h (95% CI = -7.7 to -0.8; P ≤ .016), Epworth Sleepiness Scale of -2.5 of 24 (95% CI= -5.1 to -0.1; P ≤ .066), Pittsburgh Sleep Quality Index of -1.3 of 21 (95% CI= -2.4 to -0.2; P ≤ .026), snoring frequency (P = .044) in intervention groups compared with controls.

CONCLUSIONS

This systematic review highlights respiratory muscle therapy as an adjunct management for OSA but further studies are needed due to limitations including the nature and small number of studies, heterogeneity of the interventions, and high risk of bias with low quality of evidence.

Evaluation of the pharyngeal airway using computational fluid dynamics in patients with acromegaly

Objectives

Perioperative airway management may be particularly challenging in patients with acromegaly undergoing trans‐sphenoidal pituitary surgery (TSS). Management for airway obstruction is required prior to pituitary surgery to minimize perioperative hypoxia. The purpose of this retrospective study was to evaluate airway obstruction by simulation of computational fluid dynamics (CFD) using computed tomography (CT) images in patients who had undergone TSS.

Methods

CT images of the nasopharyngeal airways of patients with acromegaly (n = 5) or nonfunctional pituitary adenoma (n = 6) undergoing TSS from April 2012 to January 2017 were used to construct these airways in three dimensions. Estimated airflow pressure and velocity in the retropalatal airway (RA), oropharyngeal airway (OA), and hypopharyngeal airway (HA) were simulated using CFD.

Results

Estimated pharyngeal airflow pressure in the HA, OA, and RA was significantly greater in patients with acromegaly than in those with nonfunctional pituitary adenomas whereas the estimated pharyngeal airflow velocity was significantly impaired only in the RA of patients with acromegaly. Minimum postoperative SpO₂ both within 3 hours and from 3 to 12 hours after the end of anesthesia was significantly lower in the patients with acromegaly. Additionally, estimated volume of tongue and pharyngeal airflow pressure in the HA, OA, and RA correlated with minimum postoperative SpO₂.

Conclusion

Pharyngeal airflow pressure estimated from CT images is high in patients with acromegaly, and these values correlate with postoperative minimum values for SpO₂. Preoperative evaluation of CT images by CFD can predict difficulty in airway management and perioperative hypoxia.

Level of Evidence

4.

Influence of pharyngeal airway respiration pressure on Class II mandibular retrusion in children: A computational fluid dynamics study of inspiration and expiration

OBJECTIVES

To examine the influence of negative pressure of the pharyngeal airway on mandibular retraction during inspiration in children with nasal obstruction using the computational fluid dynamics (CFD) method.

SETTING AND SAMPLE POPULATION

Sixty-two children were divided into Classes I, II (mandibular retrusion) and III (mandibular protrusion) malocclusion groups.

MATERIAL AND METHODS

Cone-beam computed tomography data were used to reconstruct three-dimensional shapes of the nasal and pharyngeal airways. Airflow pressure was simulated using CFD to calculate nasal resistance and pharyngeal airway pressure during inspiration and expiration.

RESULTS

Nasal resistance of the Class II group was significantly higher than that of the other two groups, and oropharyngeal airway inspiration pressure in the Class II (-247.64 Pa) group was larger than that in the Class I (-43.51 Pa) and Class III (-31.81 Pa) groups (P<.001). The oropharyngeal airway inspiration-expiration pressure difference in the Class II (-27.38 Pa) group was larger than that in the Class I (-5.17 Pa) and Class III (0.68 Pa) groups (P=.006).

CONCLUSION

Large negative inspiratory pharyngeal airway pressure due to nasal obstruction in children with Class II malocclusion may be related to their retrognathia.

Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

The changes of the upper airway after large retraction of the incisors in adult class I bimaxillary protrusion patients were assessed mainly focused on the anatomic variation and ignored the functional changes. This study aimed to investigate the changes of the upper airway in adult class I bimaxillary protrusion patients after extraction treatment using the functional images based on computational fluid dynamics (CFD). CFD was implemented after 3D reconstruction based on the CBCT of 30 patients who have completed extraction treatment. After treatment, pressure drop in the minimum area, oropharynx, and hypopharynx increased significantly. The minimum pressure and the maximum velocity mainly located in the hypopharynx in pre-treatment while they mostly occured in the oropharynx after treatment. Statistically significant correlation between pressure drop and anatomic parameters, pressure drop and treatment outcomes was found. No statistical significance changes in pressure drop and volume of nasopharynx was found. This study suggested that the risk of pharyngeal collapsing become higher after extraction treatment with maximum anchorage in bimaxillary protrusion adult patients. Those adverse changes should be taken into consideration especially for high-risk patients to avoid undesired weakening of the respiratory function in clinical treatment.

How has our interest in the airway changed over 100 years?

Since the beginning of our specialty, our understanding of the link between function and facial growth and development has progressively improved. Today, we know that children with sleep-related breathing problems will often develop distinctive facial characteristics. In adults, sleep apnea can result in serious morbidity and mortality. Orthodontists can ask sleep-related questions in the health history to help identify sleep breathing disorders. Treating these patients presents unique opportunities for orthodontists to collaborate with other medical specialties to improve a patient's health and treatment outcome. Research presented in our Journal in the next century may shed new light that will help us better identify the problem and aid the specialty in developing more effective evidence-based treatment. Additional efforts are needed to understand the physiology, neurology, and genetics of sleep breathing disorders.

Correlation of Lateral Cephalogram and Flexible Laryngoscopy with Sleep Study in Obstructive Sleep Apnea

Objective. To study the correlation between lateral cephalogram, flexible laryngoscopy, and sleep study in patients diagnosed with obstructive sleep apnea (OSA). Background. Screening tools should be devised for predicting OSA which could be performed on an outpatient basis. With this aim we studied the skeletal and soft tissue characteristics of proven OSA patients. Methods. A prospective study was performed in patients diagnosed with obstructive sleep apnea by sleep study. They were evaluated clinically and subjected to lateral cephalometry and nasopharyngolaryngoscopy. The findings were matched to see if they corresponded to AHI of sleep study in severity. An attempt was made to see whether the data predicted the patients who would benefit from oral appliance or surgery as the definitive treatment in indicated cases. Results. A retropalatal collapse seen on endoscopy could be equated to the distance from mandibular plane to hyoid (MP-H) of lateral cephalometry and both corresponded to severity of AHI. At the retroglossal region, there was a significant correlation with MP-H, length of the soft palate, and AHI. Conclusion. There is significant correlation of lateral cephalogram and awake flexible nasopharyngolaryngoscopy with AHI in OSA. In unison they form an excellent screening tool for snorers.

Transverse Retropalatal Collapsibility Is Associated with Obstructive Sleep Apnea Severity and Outcome of Relocation Pharyngoplasty

OBJECTIVE

The aim of this study was to investigate whether the retropalatal airway shape and collapsibility defined by awake nasopharyngoscopy with Müller's maneuver were associated with apnea-hypopnea index (AHI), positional dependency, and surgical outcome of relocation pharyngoplasty in patients with obstructive sleep apnea.

STUDY DESIGN

Case series with planned data collection.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

A total of 45 obstructive sleep apnea patients were included who underwent conservative treatment (n = 13) or relocation pharyngoplasty (n = 32), and their baseline and postoperative polysomnographies and awake nasopharyngoscopies with Müller's maneuver were reviewed. Shape ratio (transverse diameter [TD] / longitudinal diameter [LD]) in the stationary and Müller's phases and collapsibility (ColTD and ColLD) of the airway at the level of the uvular base were measured with a picture archiving and communication system. Intra- and interrater reliabilities were assessed. Associations among nasopharyngoscopic measurements, AHI, positional dependency, and surgical success (defined as a reduction of AHI ≥50% and a postoperative AHI ≤20/h) were statistically analyzed.

RESULTS

Reliability tests indicated substantial agreements of all nasopharyngoscopic measurements between raters and within raters. A higher baseline ColTD was significantly associated with an elevated AHI (r = 0.49, P = .001), whereas a lower postoperative ColTD was significantly related to surgical success (r = -0.38, P = .034). Nasopharyngoscopic findings were not statistically significantly correlated with positional dependency.

CONCLUSION

Transverse retropalatal collapsibility measured by awake nasopharyngoscopy with Müller's maneuver helps to predict individuals with moderate to severe sleep apnea and surgical outcome.

The effect of rapid maxillary expansion on pharyngeal airway pressure during inspiration evaluated using computational fluid dynamics

INTRODUCTION

Recent evidence suggests that rapid maxillary expansion (RME) is an effective treatment of obstructive sleep apnea syndrome (OSAS) in children with maxillary constriction. Nonetheless, the effect of RME on pharyngeal airway pressure during inspiration is not clear. The purpose of this retrospective study was to evaluate changes induced by the RME in ventilation conditions using computational fluid dynamics.

METHODS

Twenty-five subjects (14 boys, 11 girls; mean age 9.7 years) who required RME had cone-beam computed tomography (CBCT) images taken before and after the RME. The CBCT data were used to reconstruct 3-dimensional shapes of nasal and pharyngeal airways. Measurement of airflow pressure was simulated using computational fluid dynamics for calculating nasal resistance during exhalation. This value was used to assess maximal negative pressure in the pharyngeal airway during inspiration.

RESULTS

Nasal resistance after RME, 0.137 Pa/(cm(3)/s), was significantly lower than that before RME, 0.496 Pa/(cm(3)/s), and the maximal negative pressure in the pharyngeal airway during inspiration was smaller after RME (-48.66 Pa) than before (-124.96 Pa).

CONCLUSION

Pharyngeal airway pressure during inspiration is decreased with the reduction of nasal resistance by the RME. This mechanism may contribute to the alleviation of OSAS in children.

The Relation of the Obstruction Site on Muller's Maneuver with BMI, Neck Circumference and PSG Findings in OSAS

We investigated relation of the site of obstruction detected on Muller maneuver (MM) with polysomnography (PSG) and physical examination findings. Data of 703 patients admitted to Ankara Numune Education and Research Hospital Sleep Laboratory between 2008 and 2013 were analyzed retrospectively; 394 patients with apnea-hypopnea indexes (AHI) ≥5/h were included. Site of collapse on MM was determined at retrolingual level at anteroposterior (M1) and lateral-lateral (M2) directions; at retropalatal level at anteroposterior (M3) and lateral-lateral (M4) directions. There were 125 (31.7 %) females and 269 (68.3 %) males. BMI had significant positive correlations with M2 (p < 0.001) and M4 (p = 0.002) scores, ESS (p = 0.013) and AHI (p = 0.001). AHI had significant positive correlations with ESS (p = 0.003), M2 (p < 0.001), M3 (p = 0.037) and M4 (p < 0.001) scores and NC (p = 0.001). Minimum oxygen saturation had significant reverse correlations with M1 (p = 0.046), M2 (p < 0.001), M3 (p = 0.003), M4 (p < 0.001), AHI (p < 0.001), ESS (p = 0.003) and BMI (p = 0.001). In OSAS patients, increased BMI, NC and AHI are correlated with lateral pharyngeal wall (LPW) collapse in retropalatal and retrolingual levels on MM. LPW collapse is more valuable to predict OSAS compared to anteroposterior collapse. LPW collapse on MM may be used as a selection criterion for ordering PSG. Further studies are needed to better clarify importance of LPW in OSAS surgery.

Fractal quantitative endoscopic evaluation of the upper airway in patients with obstructive sleep apnea syndrome

Objective: To analyze computer-assisted quantitative measurements of endoscopic images taken during fiberoptic nasopharyngoscopy with Müller's maneuver that were processed with the use of fractal geometry and correlate them with the apnea-hypopnea index of patients with obstructive sleep apnea syndrome as well as habitual snorers.

Study Design: Diagnostic test assessment for the analysis of images acquired through fiberoptic nasopharyngoscopy with Müller's maneuver and processed with the use of fractal geometry.

Setting: Sleep laboratory in a tertiary care private hospital in Athens, Greece.

Subjects and Methods: A total of 42 subjects (25 patients, 17 control subjects) underwent fiberoptic endoscopic nasopharyngoscopy with Müller's maneuver and polysomnographic overnight testing. Endoscopic images were digitally analyzed, and fractal analysis software was used to determine fractal dimensions of postpalatal airway contour during quiet inspiration and Müller's maneuver. Findings were correlated with the apnea-hypopnea index.

Results: Fractal dimension of collapsed airway and airway collapsibility was shown to be correlated with the apnea-hypopnea index (r = −0.481 and 0.518). We used 9.5 percent airway collapsibility on the basis of fractal dimensions as a cutoff (decided according to a receiver operating characteristic curve) and found that the predictability of obstructive sleep apnea had a sensitivity of 92.0 percent (95% confidence interval 75.03-97.78) and a specificity of 82.4 percent (95% confidence interval 58.97-93.8), with a positive predictive value of 88.5 percent and a negative predictive value of 87.5 percent ( P < 0.0001).

Conclusion: Fractal analysis provides an additional measure of objectivity for the interpretation of computer-assisted quantitative endoscopic evaluation of patients with obstructive sleep apnea. Nevertheless, as confidence intervals show, some uncertainty remains regarding the real population estimate, and therefore additional studies involving larger population groups are encouraged.

Combination of Bernouilli effect producing maneuver-induced pharyngeal narrowing rate with body mass index as predictive tool for obstructive sleep apnea syndrome

CONCLUSIONS

It is suggested that the combination of the pharyngeal narrowing rate during the Bernouilli effect producing maneuver (BEPM) with the body mass index (BMI) might be a promising predictive method for obstructive sleep apnea syndrome (OSAS).

OBJECTIVES

An attempt was made to clarify the possibility that the dynamic narrowing of the pharynx evaluated by nasopharyngoscopy with BEPM, a forced inspiration through the nose with the mouth closed, might be a reliable clinical daytime predictor for identifying patients at risk of developing OSAS.

SUBJECTS AND METHODS

Subjects were 57 patients complaining of snoring and sleepiness during daytime. Endoscopic images of the retropalatal pharynx were obtained and their area was measured by NIH imaging. The pharyngeal narrowing rate during quiet nasal breathing and that during BEPM were compared to assess pharyngeal dynamics. To increase the sensitivity of this method, BMI was added to the pharyngeal narrowing rate during BEPM.

RESULTS

The criterion of BEPM at a cut-off value of 50% with BMI at a cut-off value of 25 kg/m(2) achieved a sensitivity of 93%, while the specificity was 67% in differentiating simple snorers from OSAS patients (apnea index >5). In addition, the likelihood ratio of the method was found to be 2.81.

The correlation between pharyngeal narrowing and the severity of sleep-disordered breathing

OBJECTIVE: The aim of this study was to examine the correlation between the degree or shape of pharyngeal narrowing as observed during the Muller maneuver and the severity of sleep-disordered breathing (SDB).

SUBJECTS AND METHODS: We enrolled 33 patients with SDB, and they underwent polysomnography (PSG). The degree of pharyngeal narrowing (grade I-IV) according to fiberoptic nasopharyngoscopy with the Muller maneuver (FNMM) and the shape of pharyngeal narrowing were evaluated at different anatomical levels. These variables were compared with the total apnea hypopnea index (AHI), the supine AHI, and the lateral AHI obtained by PSG.

RESULTS: The retroglossal FNMM grades revealed significant correlation with total AHI ( P = 0.030) and supine AHI ( P = 0.012). The retropalatal FNMM grades were significantly correlated with lateral AHI ( P = 0.020). The lateral-narrowing type at the retropalatal level is more significantly associated with higher total AHI compared with the anteroposterior-narrowing type ( P = 0.010).

CONCLUSION: The anatomic level and the degree of pharyngeal narrowing observed during FNMM revealed a correlation with the AHIs of different sleeping positions.