Comparison between anatomy and resistance of upper airway in normal subjects, snorers and OSAS patients

Craniofacial risk factors for obstructive sleep apnea-systematic review and meta-analysis

Obstructive sleep apnea (OSA) is caused by temporary partial or complete constriction of the upper airway during sleep which leads to reduced blood oxygen and cardiovascular risks. Main symptoms vary between adults and children leading to misdiagnosis or delayed patient identification. To improve early diagnosis, lateral cephalograms can provide craniofacial measurements associated with a higher risk of OSA. In order to identify the most relevant craniofacial measurements, a systematic literature review with meta-analysis was conducted combining the terms 'orthodontic*', 'craniofacial', 'cephalometr*', 'cephalogram', 'OSA*', 'UARS', 'SDB', 'sleep disordered breathing', 'sleep apnea' and 'sleep apnoea'. Of 3016 publications, 19 were included in the systematic review and meta-analysis, 15 with adult patients and four with children. A total of 16 measurements (six angles, 10 distances) were compared, nine showed a possible influence in patients with OSA compared to controls: NSBa angle (-0.28°), ANB angle (+0.33°), ML-NSL angle (+0.34°), Me-Go-Ar angle (+0.33°), SN distance (-0.70 mm), N-ANS distance (-0.36 mm), MP-H distance (+1.18 mm), uvula length (+1.07 mm) and thickness (+0.96 mm). Posterior airway measurements were not sufficiently described or comparably measured to be statistically analysed. There is some evidence for altered craniofacial anatomy in patients with OSA compared to controls. Lateral cephalograms should be screened for these aspects routinely to improve early diagnosis of OSA and craniofacial orthopaedics should complement the interdisciplinary treatment plan for young patients with OSA.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Determining the Site of Upper Airway Narrowing in Snorers Using a Noninvasive Technique

Background

In this study, we aimed to determine the site of obstruction if surgical treatment is considered. Flexible nasopharyngoscopy is an invasive procedure currently used for the assessment of snoring and the level of obstruction. Here, we examine the role of Somnoscreen™ plus, a noninvasive cardiorespiratory polysomnographic device, in identifying the site of obstruction in patients presenting with snoring.

Methodology

This cross-sectional study was conducted in the Sleep Research Center at King Abdulaziz University Hospital. Polysomnography was conducted using Somnoscreen™ plus. All participants underwent flexible nasopharyngoscopy after polysomnography.

Results

Nasopharyngoscopy revealed that the most common site of obstruction was the nose and the soft palate (35.4%), followed by the soft palate alone (25%). Somnoscreen revealed that the site of obstruction was the nose and the soft palate in 18 (37.5%) patients and the nose alone in 16 (33.3%) patients. However, distal obstructions were not detected using Somnoscreen. The concordance of nasopharyngoscopy and Somnoscreen was 52.9%. However, it showed a discrepancy in identifying distal obstructions, which Somnoscreen™ plus failed to detect.

Conclusions

Somnoscreen appears to be sensitive for identifying proximal airway obstructions. The audio signal recordings can potentially be used as a tool to detect the site of airway obstruction in snoring; however, further studies are needed.

Cervical Spine Hyperextension and Altered Posturo-Respiratory Coupling in Patients With Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) is associated with postural dysfunction characterized by abnormal spinal curvature and disturbance of balance and walking, whose pathophysiology is poorly understood. We hypothesized that it may be the result of a pathological interaction between postural and ventilatory functions. Twelve patients with OSAS (4 women, age 53 years [51–63] (median [quartiles]), apnea hypopnea index 31/h [24–41]) were compared with 12 healthy matched controls. Low dose biplanar X-rays (EOS® system) were acquired and personalized three-dimensional models of the spine and pelvis were reconstructed. We also estimated posturo-respiratory coupling by measurement of respiratory emergence, obtaining synchronized center of pressure data from a stabilometric platform and ventilation data recorded by an optico-electronic system of movement analysis. Compared with controls, OSAS patients, had cervical hyperextension with anterior projection of the head (angle OD-C7 12° [8; 14] vs. 5° [4; 8]; p = 0.002), and thoracic hyperkyphosis (angle T1–T12 65° [51; 71] vs. 49° [42; 59]; p = 0.039). Along the mediolateral axis: (1) center of pressure displacement was greater in OSAS patients, whose balance was poorer (19.2 mm [14.2; 31.5] vs. 8.5 [1.4; 17.8]; p = 0.008); (2) respiratory emergence was greater in OSAS patients, who showed increased postural disturbance of respiratory origin (19.2% [9.9; 24.0] vs. 8.1% [6.4; 10.4]; p = 0.028). These results are evidence for the centrally-mediated and primarily respiratory origin of the postural dysfunction in OSAS. It is characterized by an hyperextension of the cervical spine with a compensatory hyperkyphosis, and an alteration in posturo-respiratory coupling, apparently secondary to upper airway instability.

Mandibular advancement reveals long-term suppression of breathing discomfort in patients with obstructive sleep apnea syndrome

Obstructive sleep apnoea syndrome (OSAS) patients do not report breathing discomfort in spite of abnormal upper airway mechanics. We studied respiratory sensations in OSAS patients without and with mandibular advancement device (MAD). Fifty-seven moderate to severe non obese OSAS patients were asked about breathing discomfort using visual analogue scales (VAS) in the sitting position (VAS-1), after lying down (VAS-2), then with MAD (VAS-3). Awake critical closing pressure (awake Pcrit) was measured in 15 patients without then with MAD. None of the patients reported breathing discomfort when sitting but 19 patients (33%) did when lying (VAS-2: -20% or less). A feeling of "easier breathing" with MAD was observed and was more marked in patients reporting breathing discomfort when supine (VAS-3: +66.0% [49.0; 89.0]) than in those not doing so (VAS-3: +28.5% [1.0; 56.5], p = 0.007). MAD-induced change in awake Pcrit was correlated to VAS-3. In conclusion, MAD revealed "latent dyspnea" related to the severity of upper airways mechanics abnormalities in OSAS patients.

Comparison of hyoid bone positions and pharyngeal airway dimensions in different body mass index percentile adolescent subjects

OBJECTIVE

Increased body mass index (BMI) is a growing problem worldwide and can affect medical conditions through morphological structures. The purpose of this study was to examine the hyoid bone position and pharyngeal airway dimensions on the sagittal section in different BMI percentile adolescent subjects.

METHODS

Fifty-five adolescent patients were subdivided into three groups, considering their BMI percentiles: Normal-weight (16 subjects), overweight (20 subjects), and obese (19 subjects). A total of 13 linear and angular parameters of head posture angle, pharyngeal airway dimensions, and hyoid bone positions were investigated on 55 lateral cephalometric radiographs.

RESULTS

Except for one hyoid bone measurement (RGN-H), there was no significant difference among groups. The RGN-H distances of obese and overweight adolescent subjects were higher than normal-weight adolescent subjects.

CONCLUSION

Obese, overweight, and normal-weight adolescent subjects were likely to have similar hyoid bone position and pharyngeal airway dimensions.

Three-dimensional evaluation of the posterior airway space: differences in computed tomography and cone beam computed tomography

OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) becomes increasingly important. For diagnosis and surgery, computed tomography (CT), and cone beam computed tomography (CB-CT) are used equally, although in most of cases, patient positioning differs between supine positioning (CT) and upright seating positioning (CB-CT). We measured volumetric and anatomical changes in the posterior airway space (PAS) between upright and supine positioning in a three-dimensional set up.

MATERIALS AND METHODS

Coherent CT and CB-CT scans of 55 patients were included in the study. Using Brainlab ENT 3.0, image data was superimposed, and three-dimensional models were segmented. PAS height, cross-sectional area, vertical and horizontal position of the mandible and hyoid, and volumetric analyses of the three-dimensional models were measured.

RESULTS

PAS height and cross-sectional area were significantly higher in CB-CT compared to CT scans (p < 0.001). In the vertical dimension, the mandible and hyoid were localized more caudally in CB-CT in contrast to CT scans (p < 0.04; p < 0.001). Three-dimensional evaluation showed a greater volume of the PAS in CB-CT (p < 0.0001). Pearson correlation coefficient showed a correlation between vertical positioning of the mandible and hyoid compared to the positioning of the patient.

CONCLUSIONS

Patient positioning during CT and CB-CT has an effect on the location of anatomical structures like the mandible and hyoid and changes the dimensions and volume of the posterior airway space significantly.

CLINICAL RELEVANCE

The radiological technique used and the positioning of the patient should be taken into account when considering further surgical therapy.

Evaluations of the tongue and hyoid bone positions and pharyngeal airway dimensions after maxillary protraction treatment

OBJECTIVE

To assess changes in the tongue and hyoid bone positions and airway dimensions after maxillary protraction using lateral cephalograms.

METHODS

Lateral cephalograms were obtained before (C0) and after (C1) an observation period for untreated children with skeletal Class I malocclusion and before (T0), immediately after (T1), and one year after (T2) maxillary protraction in children with skeletal Class III malocclusion. Cephalometric measurements were compared between the time points in both patient groups.

RESULTS

Immediately after maxillary protraction, the tongue moved superiorly and the nasopharyngeal and superior oropharyngeal airway dimensions increased. No significant changes in the middle or inferior oropharyngeal airway dimensions or in the hyoid bone position were noted after treatment.

CONCLUSIONS

Maxillary protraction improved tongue posture and modified the nasopharyngeal and superior oropharyngeal airway dimensions in patients with skeletal Class III malocclusion. Consequently, maxillary protraction may restore the intra- and extraoral balance and improve respiratory function.

High nasal resistance is stable over time but poorly perceived in people with tetraplegia and obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is highly prevalent in people with tetraplegia. Nasal congestion, a risk factor for OSA, is common in people with tetraplegia. The purpose of this study was to quantify objective and perceived nasal resistance and its stability over four separate days in people with tetraplegia and OSA (n=8) compared to able-bodied controls (n=6). Awake nasal resistance was quantified using gold standard choanal pressure recordings (days 1 and 4) and anterior rhinomanometry (all visits). Nasal resistance (choanal pressure) was higher in people with tetraplegia versus controls (5.3[6.5] vs. 2.1[2.4] cmH₂O/L/s, p=0.02) yet perceived nasal congestion (modified Borg score) was similar (0.5[1.8] vs. 0.5[2.0], p=0.8). Nasal resistance was stable over time in both groups (CV=0.23±0.09 vs. 0.16±0.08, p=0.2). These findings are consistent with autonomic dysfunction in tetraplegia and adaptation of perception to high nasal resistance. Nasal resistance may be an important therapeutic target for OSA in this population but self-assessment cannot reliably identify those most at risk.

The prevalence of perioperative complications in patients with and without obstructive sleep apnoea: a prospective cohort study

BACKGROUND AND AIMS

Patients with obstructive sleep apnoea (OSA) have a high risk of postoperative complications. The purpose of the study was to record the spectrum and frequency of postoperative complications in patients with OSA versus (vs.) without OSA depending on the type of surgery and type of anaesthesia in a large cohort of patients.

METHODS

We conducted a prospective, descriptive study (n = 400). Ethics Committee approval was obtained and written informed consent was signed. The Berlin screening questionnaire was used for OSA screening (77.2% - OSA [+]). Adverse events and complications were recorded postoperatively (AOS [+] vs. AOS [-]). Statistics: Chi square test.

RESULTS

The highest rate of complications was found in patients who had underwent surgery in the abdominal cavity under general anaesthesia, AOS [+] vs. AOS [-]: cardiovascular [56.4%] vs. [7.5%], respiratory [17.6%] vs. [3.5%], stroke [0.7%] vs. [0.0% ], prolonged awakening from anaesthesia [2.5%] vs. [0.0%], postoperative fever [1.4%] vs. [0.3%], difficult orotracheal intubation [3.5%] vs. [0.3% ], unscheduled transfer to the intensive care unit [5.7%] vs. [0.0%].

CONCLUSIONS

OSA [+] patients who underwent abdominal surgery under general anaesthesia had a higher rate of complications compared to OSA [-] patients, and also compared to patients who had undergone peripheral limb surgery. Surgery on the musculoskeletal system is much better tolerated by patients with OSA, suffering a lower number and range of events and postoperative complications. Loco-regional anaesthesia should be considered a priority in patients with OSA.

Craniofacial and upper airway morphology in adult obstructive sleep apnea patients: A systematic review and meta-analysis of cephalometric studies

Obstructive sleep apnea (OSA) is one of the common sleep breathing disorders in adults, characterised by frequent episodes of upper airway collapse during sleep. Craniofacial disharmony is an important risk factor for OSA. Overnight polysomnography (PSG) study is considered to be the most reliable confirmatory investigation for OSA diagnosis, whereas the precise localization of site of obstruction to the airflow cannot be detected. Identifying the cause of OSA in a particular ethnic population/individual subject helps to understand the etiological factors and effective management of OSA. The objective of the meta-analysis is to elucidate altered craniofacial anatomy on lateral cephalograms in adult subjects with established OSA. Significant weighted mean difference with insignificant heterogeneity was found for the following parameters: anterior lower facial height (ALFH: 2.48 mm), position of hyoid bone (Go-H: 5.45 mm, S-H: 6.89 mm, GoGn-H: 11.84°, GoGn-H: 7.22 mm, N-S-H: 2.14°), and pharyngeal airway space (PNS-Phw: -1.55 mm, pharyngeal space: -495.74 mm² and oro-pharyngeal area: -151.15 mm²). Significant weighted mean difference with significant heterogeneity was found for the following parameters: cranial base (SN: -2.25 mm, S-N-Ba: -1.45°), position and length of mandible (SNB: -1.49° and Go-Me: -5.66 mm) respectively, maxillary length (ANS-PNS: -1.76 mm), tongue area (T: 366.51 mm²), soft palate area (UV: 125.02 mm²), and upper airway length (UAL: 5.39 mm). This meta-analysis supports the relationship between craniofacial disharmony and obstructive sleep apnea. There is a strong evidence for reduced pharyngeal airway space, inferiorly placed hyoid bone and increased anterior facial heights in adult OSA patients compared to control subjects. The cephalometric analysis provides insight into anatomical basis of the etiology of OSA that can influence making a choice of appropriate therapy.

Upper airway imaging in sleep-disordered breathing

Our understanding of sleep-disordered breathing has evolved considerably over the past three decades, and clinical techniques of evaluation have progressed tremendously. Myriad imaging techniques are now available for the physician to approach the dynamic features resulting in turbulent airflow, upper airway narrowing or collapse at different levels. Controversy exists in the choice of investigations, probably because the best evaluation should be a combination of different techniques. Physical, radiographic, endoscopic and acoustic evaluations could be integrated to understand the degree and the levels of airway reduction and/or obstruction in a given patient. This review focuses on cost-effective and easily implemented techniques in daily practice, allowing quality assessment of the dynamic anatomy of sleep-disordered breathing: cephalometry, (sleep-)endoscopy and acoustic reflectometry of the upper airway.

Peripharyngeal tissue deformation and stress distributions in response to caudal tracheal displacement: pivotal influence of the hyoid bone?

Caudal tracheal displacement (TD) leads to improvements in upper airway (UA) function and decreased collapsibility. To better understand the mechanisms underlying these changes, we examined effects of TD on peripharyngeal tissue stress distributions [i.e., extraluminal tissue pressure (ETP)], deformation of its topographical surface (UA lumen geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing, adult male New Zealand white rabbits. Graded TD was applied to the cranial tracheal segment from 0 to ∼10 mm. ETP was measured at six locations distributed around/along the length of the UA, covering three regions: tongue, hyoid, and epiglottis. Axial images of the UA (nasal choanae to glottis) were acquired with computed tomography and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid bone displacement. TD resulted in nonuniform decreases in ETP (generally greatest at tongue region), ranging from −0.07 (−0.11 to −0.03) [linear mixed-effects model slope (95% confidence interval)] to −0.27 (−0.31 to −0.23) cmH2O/mm TD, across all sites. UA length increased by 1.6 (1.5–1.8)%/mm, accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 2.8 (1.7–3.9) to 4.9 (3.8–6.0)%/mm. The hyoid bone was displaced caudally by 0.22 (0.18–0.25) mm/mm TD. In summary, TD imposes a load on the UA that results in heterogeneous changes in peripharyngeal tissue stress distributions and resultant lumen geometry. The hyoid bone may play a pivotal role in redistributing applied caudal tracheal loads, thus modifying tissue deformation distributions and determining resultant UA geometry outcomes.

Changes in hyoid bone position following rapid maxillary expansion in adolescents

OBJECTIVE

To examine changes in hyoid to mandibular plane distance (H-MP) and tongue length (TL) between children who had orthodontic treatment with and without rapid maxillary expansion (RME).

MATERIALS AND METHODS

Lateral and frontal cephalograms of 138 patients treated with RME and 148 controls treated without RME were used to measure pretreatment (T(1)) and posttreatment (T(2)) intermolar (IM) distance, lateronasal width (LNW), H-MP, and TL. Medical histories were used to collect demographic information, history of mouth breathing, difficulty breathing through the nose, and previous adenotonsillectomy. Groups were group-matched for age and gender. Descriptive statistics were calculated. Group means were compared using t-tests and chi-square statistics. Reliability was estimated using intraclass correlations and kappa statistics. Statistical significance was set at P < .05.

RESULTS

At T(1), the RME group showed smaller LNW (24.83 ± 1.99 vs 26.18 ± 2.05) and IM (50.17 ± 2.3 vs 51.58 ± 2.83). The distance from H-MP was longer in the RME group (15.69 ± 3.95 vs 13.86 ± 3.4). Mean changes (T(2) - T(1)) in the RME group were increased LNW (+2.48 ± 1.38 vs +0.94 ± 1.11 for the non-RME group) and IM (+3.21 ± 1.72 vs +0.98 ± 1.67). The mean change (T(2) - T(1)) in H-MP for the RME group was -0.68 ± 3.67 compared with +1.1 ± 2.96 for the non-RME group. Mean changes for TL were not statistically significant. No significant differences were noted at T(2) between groups for LNW, H-MP, or TL.

CONCLUSIONS

In this sample, RME produced significant changes in H-MP, and TL was unaffected.

Three-dimensional computed tomographic analysis of airway anatomy in patients with obstructive sleep apnea

PURPOSE

To identify abnormalities in airway size and shape that correlate with the presence and severity of obstructive sleep apnea (OSA).

MATERIALS AND METHODS

This was a retrospective case series of patients undergoing treatment of OSA who had preoperative computed tomographic (CT) scans of the upper airway available. Patients who had undergone CT scanning for nonairway pathologic features during the same period served as the controls. Digital 3D-CT reconstructions were made and 12 parameters of airway size and 4 of shape were analyzed. The posterior airway space, middle airway space, and hyoid to mandibular plane distance were measured on the lateral cephalograms of the patients with OSA. Bivariate analysis was used to identify the factors associated with the presence and severity of OSA as measured by the respiratory disturbance index (RDI). Multiple regression analysis identified the factors that correlated with the RDI.

RESULTS

Of the 44 patients with OSA, 15 (10 men and 5 women) had pre- and postoperative CT scans available. In addition, 17 patients (11 men and 6 women) were used as controls. The airway length was significantly increased in the patients with OSA (P < .01). On bivariate analysis, the length, lateral/retroglossal anteroposterior dimension ratio and genial tubercle to hyoid bone distance were associated with the RDI (P < .03). On multiple regression analysis, length (P < .01) had a positive correlation and the lateral/retroglossal anteroposterior dimension ratio (P = .04) an inverse correlation with the RDI.

CONCLUSIONS

The results of this study indicate that the presence of OSA is associated with an increase in airway length. Airways that were more elliptical in shape and mediolaterally oriented (greater lateral/retroglossal anteroposterior dimension ratio) had a decreased tendency toward obstruction.

Snoring source identification and snoring noise prediction

This paper investigates the snoring mechanism of humans by applying the concept of structural intensity to a three-dimensional (3D) finite element model of a human head, which includes: the upper part of the head, neck, soft palate, hard palate, tongue, nasal cavity and the surrounding walls of the pharynx. Results show that for 20, 40 and 60Hz pressure loads, tissue vibration is mainly in the areas of the soft palate, the tongue and the nasal cavity. For predicting the snoring noise level, a 3D boundary element cavity model of the upper airway in the nasal cavity is generated. The snoring noise level is predicted for a prescribed airflow loading, and its range agrees with published measurements. These models may be further developed to study the various snoring mechanisms for different groups of patients.

Upper airway dynamics during negative expiratory pressure in apneic and non-apneic awake snorers

Background

The ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated.

Methods

Forty-eight subjects with sleep disordered breathing (SDB) and 7 healthy subjects, as non-snorer controls, underwent the NEP application of -5 and -7 cmH₂O in the seated and supine position during wakefulness, after performing a sleep study. The upper airway collapsibility was assessed by computing the volume exhaled during the first 0.5 sec. (V,NEP_0.5) and 1 sec. (V,NEP₁) following the NEP start.

Results

Patients with severe (AHI ≥ 30) (n = 19) and mild-to-moderate (AHI <30 and >5) (n = 15) OSAH had lower V,NEP_0.5 (340 ± 88 ml) as compared to snorers (AHI ≤ 5) (n = 14) (427 ± 101 ml; p < 0.01) and controls (n = 7) (492 ± 69 ml; p < 0.001) in the supine position with NEP -5 cmH₂O. Less significant differences among the different groups were observed for V,NEP_0.5 in the seated position with NEP -5 cmH₂O and in both positions with NEP -7 cmH₂O (only OSAH patients vs controls, p < 0.001). Similar results were obtained for V,NEP₁ in either position by using both NEP -5 cmH₂O and -7 cmH₂O. In spite of this, a substantial overlapping of V,NEP_0.5 and V,NEP₁ between snorers and OSAH patients did not allow to identify a reliable diagnostic cut-off level. An inverse correlation with AHI was found for V,NEP_0.5 in the supine position with NEP -5 cmH₂O (r_s = -0.46, p < 0.05) in severe OSAH patients.

Conclusion

The awake OSAH patients exhibit values of V,NEP_0.5 and V,NEP₁ lesser than those of awake snorers. The NEP technique, however, appears to have a limited usefulness as clinical tool for routine screening of the OSAH patients during wakefulness.

Sleep. 2: pathophysiology of obstructive sleep apnoea/hypopnoea syndrome

The pathogenesis of airway obstruction in patients with obstructive sleep apnoea/hypopnoea syndrome is reviewed. The primary defect is probably an anatomically small or collapsible pharyngeal airway, in combination with a sleep induced fall in upper airway muscle activity.