Cephalometric airway analysis in obstructive sleep apnea syndrome

Is obstructive sleep apnea associated with difficult airway? Evidence from a systematic review and meta-analysis of prospective and retrospective cohort studies

BACKGROUND

Difficult airway management and obstructive sleep apnea may contribute to increased risk of perioperative morbidity and mortality. The objective of this systematic review and meta-analysis (SRMA) is to evaluate the evidence of a difficult airway being associated with obstructive sleep apnea (OSA) patients undergoing surgery.

METHODS

The standard databases were searched from 1946 to April 2017 to identify the eligible articles. The studies which included adult surgical patients with either suspected or diagnosed obstructive sleep apnea must report at least one difficult airway event [either difficult intubation (DI), difficult mask ventilation (DMV), failed supraglottic airway insertion or difficult surgical airway] in sleep apnea and non-sleep apnea patients were included.

RESULTS

Overall, DI was 3.46-fold higher in the sleep apnea vs non-sleep apnea patients (OSA vs. non-OSA: 13.5% vs 2.5%; OR 3.46; 95% CI: 2.32-5.16, p <0.00001). DMV was 3.39-fold higher in the sleep apnea vs non-sleep apnea patients (OSA vs. non-OSA: 4.4% vs 1.1%; OR 3.39; 95% CI: 2.74-4.18, p <0.00001). Combined DI and DMV was 4.12-fold higher in the OSA vs. non-OSA patients (OSA vs. non-OSA: 1.1% vs 0.3%; OR 4.12; 95% CI: 2.93-5.79, p <0.00001). There was no significant difference in the supraglottic airway failure rates in the sleep apnea vs non-sleep apnea patients (OR: 1.34; 95% CI: 0.70-2.59; p = 0.38). Meta-regression to adjust for various subgroups and baseline confounding factors did not impact the final inference of our results.

CONCLUSION

This SRMA found that patients with obstructive sleep apnea had a three to four-fold higher risk of difficult intubation or mask ventilation or both, when compared to non-sleep apnea patients.

Prediction of tongue obstruction observed from drug induced sleep computed tomography by cephalometric parameters

OBJECTIVE

To elucidate potential role of cephalometric measurements to predict tongue base obstruction as observed on drug Induced Sleep Computed Tomography (DIS-CT).

METHODS

Study included 35 patients with moderate to severe sleep apnea who underwent DIS-CT & cephalometric examination to assess tongue base obstruction.

RESULTS

Statistically significant difference was noted for SNA angle & Mandibular posterior airway space (PAS) among groups with total tongue obstruction versus Non-total tongue obstruction identified on DIS-CT.

CONCLUSION

Lateral cephalogram can be used as a standard screening tool with commonly used skeletal and soft tissue parameters to predict the possibility of tongue collapse/obstruction during sleep in patient with moderate to severe OSAS.

No correlation between two-dimensional measurements and three-dimensional configuration of the pharyngeal upper airway space in cone-beam computed tomography

The aim of this study was to evaluate both the 2-dimensional (2D) and 3-dimensional (3D) configuration of the posterior airway space (PAS) in healthy 239 patients using cone-beam computed tomography (CBCT). In particular, we investigated the correlation between the 2D and 3D measurements in view of the potential impact on diagnosis of upper airway obstruction. The pharyngeal airway of each patient was studied at five levels: the level of the posterior nasal spine (PNS), the level of half-height of the PNS and the tip of the soft palate, the level of the tip of the soft palate, the level of the anterior-inferior point of the second vertebra, and at least the level of the top of the epiglottis. At each of these levels, the anterior-posterior dimension as well as the corresponding cross-sectional area was measured. Furthermore we measured the volume of the whole PAS between the first and the last level and compared it with the corresponding 2D values. Differences between genders and age effects were estimated in an analysis of covariance. P values <.05 were considered significant. Linear models were fitted to find the optimal formula to calculate the area or volume from measured distances. Limits of agreement were calculated as 2 ± residual standard deviations. We generated normal 2D and 3D values of the PAS for a normal population. In regard to age, no significant differences were observed. Significant differences were assessed between healthy males and females; however no correlation was observed between the obtained measurements in 2D axial view and the corresponding cross-sectional areas and mean volume in 3D view. In summary, radiologic imaging is a helpful tool to evaluate the airway space in patients with OSAS. However, drawing conclusions from 2D PAS imaging to assess 3D PAS configuration is not reliable, since there is no sufficient correlation between posterior-anterior distances and the corresponding cross-sectional areas.

Changes in Upper Airway Volume Following Orthognathic Surgery

Reduced volume of the internal skeletal dimensions of the face is 1 of the main causes of obstructive sleep apnea, and attention to patients' airways is necessary when planning orthognathic treatment. This study aims to describe changes in upper airway volume following virtually planned orthognathic surgery.A retrospective pilot study was designed with 30 randomly selected patients (10 men and 20 women, aged 23.1 ± 6.8 years, molar-relations: 15 neutral, 8 distal, and 7 mesial). Cone-beam computed tomography scans were performed before surgery and 1 week following surgery. The authors did total upper airway volume measurements and obtained 1-mm slices at vertical levels in the velo-, oro-, and hypopharynx and at the smallest visible cross-section.Measurements before and after surgery were compared using Student t test.After orthognathic surgery, the minimum cross-sectional area at the vertical level increased from 83 mm ± 33 before surgery to 102 mm ± 36 after surgery (P = 0.019). In patients with neutral and distal occlusions, the minimum cross-sectional slice volume increased in 87% but in only 57% with mesial occlusion.The present findings suggest that orthognathic surgery increases upper airway volume parameters, but a few patients have continued impairment of the airways following orthognathic surgery. Further studies are needed to confirm an individual surgical planning approach that potentially could bring the minimum cross sectional area out of the risk zone.

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.

Pharyngeal airway analysis in obese and non-obese patients with obstructive sleep apnea syndrome

BACKGROUND

Sleep disorders are a group of disorders characterized by abnormalities of respiration during sleep. OSA (Obstructive Sleep Apnea) is characterized by the repetitive episodes of complete or partial collapse of the upper airway during sleep, causing a cessation or a significant reduction of airflow.

METHOD

The study population consisted of 30 control patients (AHI ≤ 5) events per hour, 74 patients with OSAS, including 34 Obese (BMI ≥ 27) and 40 non-obese (BMI ≤ 27). Polysomnography and measurements of 21 cephalometric variables were carried out for all patients with OSAS.

RESULTS

Obese patient with OSAS showed significant difference in following cephalometric parameters: (1) PAS (2) MPT (3) MPH (4) PNS-P (5) SAS. In addition, obese patient had longer tongue (TGL), more anteriorly displaced hyoid bones (H-VL) and more anterior displacement of mandible (G-VL) when compared with control groups. The findings of non-obese patients when compared to controls showed all the findings of obese patients and in addition to that narrow bony oropharynx were significant. Step wise regression analysis showed the significant predictors for all patients were MPH, PNS-P, bony nasopharynx (PNSBa), MPT, and palatal length (ANS-PNS) for AHI. The significant predictors for obese OSA (obstructive sleep apnea) group were MAS while for non-obese OSA group ANS-PNS was significant predictor for AHI (apnea-hypopnea index).

CONCLUSION

Craniofacial landmarks such as increase in hyoid distance, longer tongue and soft palate with increased thickness and narrowing of superior pharyngeal, oropharyngeal and hypopharyngeal airway space may be important risk factors for development of OSAS.

[Craniofacial morphology and obstructive sleep apnoea-hypopnoea syndrome: a craniometric comparative analysis]

PURPOSE

The aim of this study was to define the relationship between paediatric obstructive sleep apnoea-hypopnea syndrome (OSAHS) and craniofacial morphovolumetric features through comparative craniometric analyses between affected children and controls based on conventional cephalometry.

MATERIALS AND METHODS

Cephalometric examinations of 40 children affected by OSAHS were retrospectively evaluated. Sixteen craniometric landmarks were identified, and 27 linear and angular indices related to craniofacial morphovolumetric features were measured. Subsequently, the same process of identifying landmarks and measuring indices was performed on the cephalometric examinations of 40 controls. For each index, we then calculated in both groups the mean, standard deviation, standard error and p value. By comparing the values obtained in the two series, we calculated the degree of significance of each difference between children with OSAHS and controls using the Student t test.

RESULTS

Differences of only 5/27 linear and angular indices considered were not statistically significant between groups, thus confirming susceptibility to the disorder in relation to certain splanchnocranic morphovolumetric features. The most significant differences involved mandibular plane inclination and distance between landmark sella and hyoid bone, a reliable index being the vertical position of the latter.

CONCLUSIONS

Despite the limitations associated with the 2D nature of conventional cephalometry, mainly related to projection and identification errors, and despite the upright position during examination, we consider the diagnostic value and information content of this technique high, thus reaffirming its role as a first-line imaging investigation in children with sleep-related breathing disorders.

Relations between obstructive sleep apnea syndrome and specific cephalometric measurements, body mass index, and apnea-hypopnea index

PURPOSE

To evaluate the relation of specific cephalometric landmarks, body mass index, and the apnea-hypopnea index in patients diagnosed with obstructive sleep apnea syndrome (OSAS) and treated with functional upper airway surgery.

MATERIALS AND METHODS

This was a retrospective cohort analysis of 89 consecutive patients over a 3-year period diagnosed with overnight-attended polysomnogram-confirmed OSAS who underwent functional upper airway surgery. Five predetermined specific cephalometric parameters were analyzed: posterior airway space, soft palate length, hyoid to mandibular plane angle, sella-nasion to mandibular plane angle, and gonion to gnathion length. Simple and multiple linear regression analyses were used to establish a relation between independent and dependent variables.

RESULTS

There were no statistically significant associations between the 5 specific cephalometric craniofacial structures in combination with other potential confounders, body mass index and apnea-hypopnea index, and the presence of OSAS.

CONCLUSIONS

No one skeletal or soft tissue parameter can be directly linked to OSAS.

Reoperative treatment of obstructive sleep apnea

Over the last several decades, various surgical treatments have been advocated and used to treat obstructive sleep apnea. Treatments ranging from aggressive procedures, such as tracheostomy, to the least-invasive procedures, such as radioablation, have not yielded satisfactory results. One of the major causes for surgical failures and lower success rates lies in the inadequate understanding and appreciation of the anatomic and pathophysiologic factors that contribute to upper airway obstruction. In some cases, combinations of various surgical techniques may help improve the conditions. This article reviews several major types of surgical procedures, their complications, and the recommended approaches for retreatments.

Sex differences in anthropometric and cephalometric characteristics in the severity of obstructive sleep apnea syndrome

INTRODUCTION

Craniofacial anatomic abnormalities related to structural narrowing of the upper airway have been reported in patients with obstructive sleep apnea syndrome (OSAS). The purpose of this study was to test whether there are sex differences in the relative contributions of specific anthropometric and cephalometric measurements of OSAS severity.

METHODS

The subjects were Taiwanese patients who visited the Ear, Nose, and Throat Department of National Taiwan University Hospital with complaints of snoring or sleep apnea. The anthropometric, cephalometric, and overnight polysomnographic records of 109 subjects were evaluated.

RESULTS

There are obvious sex differences in the craniofacial skeletal characteristics that contribute to OSAS severity. Male patients with the following risk factors are likely to have more severe type OSAS: increased neck size, inferiorly positioned hyoid bone, and greater anterior lower facial height. The risk factors related to the severity of OSAS in female patients include smaller posterior facial height and anteriorly positioned hyoid bone.

CONCLUSIONS

To evaluate OSAS severity, different anthropometric and cephalometric measurements should be used for men and women. The craniofacial skeletal characteristics that contribute to OSAS severity were in the anterior lower portion of the profile in men and in the posterior portion of the profile in women.

Cephalometric analysis of nonobese snorers either with or without obstructive sleep apnea syndrome

OBJECTIVE

To determine if there is an indicator on the lateral cephalometric radiograph that can be used for the differential diagnosis of severe obstruct sleep apnea syndrome and simple snoring in nonobese young male adults.

MATERIALS AND METHODS

The subjects were Taiwanese male patients with a complaint of snoring and/or sleep apnea, whose body mass index was less than 25 kg/m(2) and who were younger than 40 years old. Forty-six patients with severe obstructive sleep apnea and 36 patients with simple snoring were selected and underwent lateral cephalometric radiography, from which 24 linear and 34 angular measurements were calculated. Differences between the two groups were studied, and a discriminatory analysis was performed.

RESULTS

Soft palate length, mandibular body length, tongue size, and distance from the hyoid bone to the mandibular plane were significantly larger in patients with severe obstructive sleep apnea syndrome. Of the original grouped cases, 76.5% were correctly classified using these five variables. The position of the hyoid bone in simple snorers was near the straight line from the third vertebra to the menton, whereas the position of the hyoid bone in severe obstruct sleep apnea syndrome patients was far below the line from the third vertebra to the menton.

CONCLUSION

The position of the hyoid bone relative to the line from the third vertebra to the menton can be used as an indicator for a diagnosis of severe obstruct sleep apnea syndrome in nonobese young male Taiwanese adults.

Diagnostic Studies in Obstructive Sleep Apnea

The standard for the diagnosis of obstructive sleep apnea (OSA) is polysomnography (PSG). Although PSG helps identify individuals who have OSA and guides medical management, it does not identify the obstruction site or predict surgical results. Radiologic and diagnostic studies have been used to direct surgical intervention and predict outcomes of sleep apnea surgery. These studies include lateral cephalometric radiographs, CT, MRI, asleep fluoroscopy, asleep and awake endoscopy, upper airway manometry, and acoustic reflection techniques. The ideal diagnostic study would identify individuals who have OSA, be cost-effective and readily accessible, and guide therapeutic, site-specific intervention with predictable results. In this article, the various modalities are reviewed in terms of their capability to effectively diagnose and guide treatment of OSA.

Changes in pharyngeal airway space and hyoid bone positions after body ostectomies and sagittal split ramus osteotomies

Although mandibular setback might lead to possible pharyngeal narrowing, the development of obstructive sleep-related breathing disorders may occur because of multiple factors. In this study, the changes in the pharyngeal airway space (PAS) and the hyoid bone position have been evaluated before and after surgery in patients who underwent body ostectomy (BO) and sagittal split ramus osteotomy (SSRO). In addition, the effects of the BO on PAS and on hyoid bone position have been compared with the effects of the SSRO.

MATERIAL AND METHODS

Thirty patients with mandibular prognathism underwent mandibular setback osteotomy. The patients were divided into two groups: BO group, 15 patients (5 men, 10 women) who underwent BO; and SSRO group, 15 patients (11 men, 4 women) who underwent SSRO. Changes in PAS and hyoid bone position were analyzed throughout the preoperative and early and long-term postoperative periods via lateral cephalometric radiographs.

RESULTS

A decrease has been observed in the PAS area and the anteroposterior dimension of the PAS detected in all patients in the long-term period. Hyoid bone revealed backward and downward movement during the early postoperative period; however, it showed a tendency to return to its original anatomic position during the long-term postoperative period. None of the patients had disturbances in respiration.

CONCLUSION

After BO and SSRO, a decrease in PAS area was observed, and this decrease also continued in the long-term period. Our results revealed a decrease in PAS area after BO, but the decrease was less than that in cases having SSRO.

Craniofacial morphology and obstructive sleep apnoea: a cephalometric analysis

The craniofacial morphology of 31 male patients diagnosed with obstructive sleep apnoea syndrome (OSAS) and 37 healthy male subjects were compared using cephalometric evaluation of lateral skull radiographs. The aim was to evaluate which cephalometric variables related to craniofacial morphology discriminate between OSAS patients and non-OSAS subjects. Sixteen cephalometric measurements were determined to study the craniofacial morphology. Differences in cephalometric variables between the two groups were analysed with unpaired Student t-tests (significance level 0.05). A multiple regression analysis was used to evaluate the joint predictive value of selected variables. With regard to five variables, significant differences were observed between OSAS patients and non-OSAS subjects (P < 0.05). Data indicated a relatively anterior position of the maxilla, an increase of the mid-facial height and a more inferiorly located hyoid bone in the OSAS patient group. The multiple regression analysis yielded a model discriminating between OSAS patients and non-OSAS subjects, which included two hyoid bone variables and one related with the intermaxillary relationship. A causal relationship between cephalometric variables of craniofacial morphology and OSAS is not sufficiently supported by our data. Presumably, hyoid bone position is of predictive value in the cephalometric discrimination between OSAS patients and non-OSAS subjects.

Pharyngeal airway space changes after counterclockwise rotation of the maxillomandibular complex

The purpose of this study was to evaluate the effects of double-jaw surgery with counterclockwise rotation of the maxillomandibular complex on the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology. Fifty patients (22 men, 28 women) with high occlusal plane facial morphology underwent double-jaw surgery with counterclockwise rotation of the maxillomandibular complex. The patients were divided into 2 groups: group 1, 30 patients (8 men, 22 women) who underwent maxillary and mandibular advancement and group 2, 20 patients (14 men, 6 women) who underwent maxillary advancement and mandibular setback. Presurgery and postsurgery lateral cephalometric radiographs were analyzed to correlate changes in pharyngeal airway space dimensions and velopharyngeal anatomy with maxillary and mandibular positional changes. The calibration showed a more than 0.94 correlation for both intra- and interoperator error. The average follow-up time was 29.6 months in group 1 and 22.2 months in group 2. Mean maxillary surgical change at point A was 4.15 mm in group 1 and 2.5 mm in group 2. Mean mandibular surgical change at the genial tubercles was 7.5 mm in group 1 and -4.95 mm in group 2. After surgery, group 1 patients had an increase in pharyngeal airway space of 47% at the soft palate and 76% at the base of the tongue relative to the amount of mandibular advancement. Group 2 patients had a decrease in pharyngeal airway space of 47% at the soft palate and 65% at the base of the tongue relative to the amount of mandibular setback. Double-jaw surgery with counterclockwise rotation of the maxillomandibular complex significantly affects the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology, with both mandibular advancement and setback.

Subgrouping persons with snoring and/or apnea by using anthropometric and cephalometric measures

Craniofacial and anthropometric characteristics are identified risk factors for obstructive sleep apnea syndrome (OSAS). Phase 1 of this study used cephalometric radiographs to record craniofacial measurements from 60 OSAS subjects with a respiratory disturbances index (RDI) of 20 or greater (group A) and 60 subjects with a history of loud snoring and an RDI less than 20 (group B). From this data set, a craniofacial risk index (CRI) was constructed using age, body mass index (BMI), and 14 cephalometric measures previously reported to be associated with OSAS. A separating boundary (CRIS) was established by using discriminant analysis to differentiate between the two groups. All measurements were determined by an investigator who was blinded to the subjects' RDI score. Phase 2 used a second sample of 19 group A and 47 group B subjects to test the ability of the CRI derived from the first sample to classify subjects in this second sample into the correct age group. The CRI was able to classify correctly 72.3% (34 of 47) of the group A subjects when all variables were used in the discriminant model. Using only four variables (age, BMI, hyoid mandibular plane distance, and tongue length) selected by the stepwise method, 72.3% (34 of 47) of the group B subjects and 78.7% of group A subjects were classified correctly. These results suggest that a stepwise CRI could be used to classify heterogeneous groups of individuals with increased RDI into subgroups with varying degrees of anatomic risk for disease. Such subgrouping by anatomic risk could be important in determining the pathophysiology of OSAS because it is likely that differences in upper airway anatomy among individuals interacts with a variety of other factors to produce clinical illness.

Pulmonary complications of obesity

Obesity can profoundly alter pulmonary function and diminish exercise capacity by its adverse effects on respiratory mechanics, resistance within the respiratory system, respiratory muscle function, lung volumes, work and energy cost of breathing, control of breathing, and gas exchange. Weight loss can reverse many of the alterations of pulmonary function produced by obesity. Obesity places the patient at risk of aspiration pneumonia, pulmonary thromboembolism, and respiratory failure. It is the most common precipitating factor for obstructive sleep apnea and is a requirement for the obesity hypoventilation syndrome, both of which are associated with substantial morbidity and increased mortality. There are numerous medical and surgical therapies for obstructive sleep apnea and obesity hypoventilation. Weight reduction in the obese is among the most effective of these measures.

Frontal and Lateral Cephalometry in Patients With Sleep-Disordered Breathing

OBJECTIVES/HYPOTHESIS

The traditional lateral-view cephalometric analysis is limited because it provides only two-dimensional analysis of the three-dimensional craniofacial structure. The objectives were to analyze lateral and frontal cephalometric radiographs in a series of normal patients and those with varying degrees of sleep-disordered breathing and to define the degrees of narrowing or other unfavorable anatomical changes that might differentiate the patients with sleep-disordered breathing from normal subjects.

STUDY DESIGN

A prospective study of 100 adult patients with sleep-disordered breathing and 60 age-matched normal subjects.

METHODS

An analysis of the lateral and frontal cephalometric measurements was performed to assess velopharyngeal anatomical features. A comparison was made between the patients' polysomnographic and cephalometric analyses.

RESULTS

The compromised cephalometric parameters that may be found in patients with sleep-disordered breathing include acute skull-base and bony nasopharynx angles, inferior hyoid position, thickening of the velum, reduced retrovelar posterior air space along with thickening of the velum, thickening of the posterior pharyngeal wall, and narrowing of the velopharyngeal lumen. Worsening of sleep-disordered breathing was generally associated with increased numbers of compromised cephalometric parameters. As body mass index increases, there is reduced velopharyngeal width, the velum thickness is increased, and the posterior pharyngeal wall thickness is increased.

CONCLUSIONS

Sleep-disordered breathing is associated with statistically significant changes in a number of cephalometric measurements. Frontal cephalometric analysis adds further information regarding the anatomical assessment of patients with upper airway obstruction, enhancing the traditional lateral cephalometric view.

Normal standard curve for acoustic pharyngometry

Pharyngeal size, compliance, and the dynamic behavior of the upper airway are important factors in the production of obstructive sleep apnea. Assessment of the upper airway for possible site(s) of obstruction is one of the keys to a successful management of the condition. Acoustic pharyngometry has the potential for localizing such sites, however, standardizing the operating technique and producing a standard normal curve is a prerequisite before exploring the potential of this equipment. A total number of 350 normal volunteers (271 males and 79 females) were examined by acoustic pharyngometry and a coefficient of variance of 5% to 7% was obtained from each of them. Mean and standard deviation of pharyngeal area at each point of X-axis (distance) was obtained and analyzed statistically to produce a general standard curve. Using special techniques during examination, the oropharyngeal junction and glottis were located, and thus a mapped acoustic pharyngogram was produced. Mean pharyngeal area was 3.194 cm(2) in males (SD 0.311) and 2.814 cm(2) in females (SD 0.331). Mean glottic area was 1.06 cm(2) in males (SD 0.119) and 0.936 cm(2) in females (SD 0.108). A minimal pharyngeal area is probably needed as a "golden standard" to evaluate patients with obstructive sleep apnea.

Maxillomandibular advancement for persistent obstructive sleep apnea after phase I surgery in patients without maxillomandibular deficiency

OBJECTIVE

To assess the outcomes of maxillomandibular advancement (MMA) for the treatment of persistent obstructive sleep apnea syndrome (OSA) after phase I reconstruction in patients who do not have maxillomandibular deficiency.

METHODS

From January 1997 to September 1998, 25 patients previously treated with phase I reconstruction (uvulopalatoplasty, genioglossus advancement, and/or hyoid suspension) who did not have maxillary and mandibular deficiencies underwent MMA for persistent OSA. Variables examined include age, sex, body mass index (BMI), respiratory disturbance index (RDI), lowest oxygen saturation (LSAT), and cephalometric data. In addition, a minimum of 6 months after surgery, questionnaires containing a 10-cm visual analogue scale (0 = no change, 10 = drastic change) were mailed to the patients. The questionnaire subjectively assessed the patient's perception of the facial appearance after surgery, whether there was pain or discomfort of the temporomandibular joint, the overall satisfaction with the treatment outcomes, and whether the patient would recommend the operation to other patients.

RESULTS

Nineteen (76%) questionnaires were completed and returned by 15 men and 4 women. The mean age was 45.3 +/- 6.6 years and the mean BMI was 33.1 +/- 7.1 kg/m2. The mean RDI improved from 63.6 +/- 20.8 to 8.1 +/- 5.9 events per hour, and the mean LSAT improved from 73.3 +/- 13.2% to 88.1 +/- 4.1%. One patient was defined as an incomplete responder (RDI >20). One patient reported transient pain and discomfort of the temporomandibular joint. Although all of the patients felt that there were changes in their facial appearance after surgery, 18 of the 19 patients gave either a neutral or a favorable response to their facial esthetic results. All of these patients were satisfied with the overall outcomes and would recommend the treatment to others.

CONCLUSION

MMA is a highly effective treatment for persistent OSA after phase I surgery in patients who otherwise do not have maxillomandibular deficiency. The patient satisfaction is extremely high. Furthermore, previous concerns of unfavorable postoperative facial esthetics and temporomandibular joint dysfunction do not appear to be significant.

Diagnosing and comanaging patients with obstructive sleep apnea syndrome

BACKGROUND

Obstructive sleep apnea syndrome, or OSAS, is a common, but underdiagnosed, disorder that potentially is fatal. It is characterized by repetitive episodes of complete or partial upper airway obstruction leading to absent or diminished airflow into the lungs. These episodes usually last 10 to 30 seconds and result in loud snoring, a decrease in oxygen saturation, and chronic daytime sleepiness and fatigue. The obstruction is caused by the soft palate, base of the tongue or both collapsing against the pharyngeal walls because of decreased muscle tone during sleep. Potentially fatal systemic illnesses frequently associated with this disorder include hypertension, pulmonary hypertension, heart failure, nocturnal cardiac dysrhythmias, myocardial infarction and ischemic stroke.

CLINICAL IMPLICATIONS

The classic signs and symptoms of OSAS may be recognizable by dental practitioners. Common findings in the medical history include daytime sleepiness, snoring, hypertension and type 2 diabetes mellitus. Common clinical findings include obesity; a thick neck; excessive fat deposition in the palate, tongue (enlarged) and pharynx; a long soft palate; a retrognathic mandible; and calcified carotid artery atheromas on panoramic and lateral cephalometric radiographs.

CONCLUSIONS

Dentists cognizant of these signs and symptoms have an opportunity to diagnose patients with occult OSAS. After confirmation of the diagnosis by a physician, dentists can participate in management of the disorder by fabricating mandibular advancement appliances and performing surgical procedures that prevent recurrent airway obstruction.

Assessment of the pharyngeal airway space after mandibular setback surgery

PURPOSE

This retrospective study evaluated the change in pharyngeal airway space associated with surgical mandibular setback.

PATIENTS AND METHODS

Lateral cephalograms of 14 adult patients taken preoperatively, immediately postoperatively, and at long-term follow-up were traced, and the width of the pharyngeal airway space and the pharyngeal airway space area were calculated and compared.

RESULTS

At long-term follow-up, the mean amount of mandibular setback was 9.7 mm. The mean reduction in the distance from the tongue base to the posterior pharyngeal wall was 4.77 mm (28% decrease). The mean reduction in pharyngeal airway space area was 1.52 cm2, which corresponded to a 12.8% reduction. There was a strong correlation between the amount of mandibular setback and the decrease in pharyngeal airway space area.

CONCLUSION

Mandibular setback surgery causes a long-term decrease in pharyngeal airway space area. In patients who have other risk factors, for example, overweight, short necks, or large tongues, a mandibular setback procedure could possibly predispose to the development of sleep apnea syndrome.

Proposed cephalometric diagnosis for osteogenic obstructive sleep apnea (OSA): the mandibular/pharyngeal ratio

The purpose of this laboratory study is to devise a simple, diagnostic test to assess possible osteological deficiency as a probable cause of OSA. Modern day skulls of fifty males and forty eight females of Tuscan origin and an additional seventy-five skulls, from India, with their cephalograms were used for this study. Mandibular length and antero-posterior dimension of the nasopharynx--pharyngeal tubercle (PhT) to posterior nasal spine (PNS)--were measured on the Tuscan skulls. The nasopharynx was similarly measured on the Indian skulls and readings multiplied by 1.14, the magnification factor of the cephalometric apparatus used. The PhT-PNS distance was then plotted on the cephalogram of Indian skulls with point PhT at the basiocciput. The possible presence of an osteogenic etiology of OSA can be determined by comparison of the mandibular/pharyngeal ratio obtained from the skull cephalograms to that of the individual patient.

Morphological assessment of the soft palate in habitual snoring using image analysis

OBJECTIVES

Define differences in palatal and uvular dimensions between habitual snorers and healthy nonsnoring control subjects. Document the changes in palatal configuration after different types of palatoplasty.

STUDY DESIGN

A prospective controlled clinical study was performed analyzing video recordings of the soft palate and oropharynx of 251 subjects (121 habitual snorers, 79 patients after laser-assisted uvulopalatoplasty ([LAUP], and 51 healthy volunteers).

METHODS

The recordings were captured using a rigid endoscope with a reference measure applied to the soft palate and a mark at the junction of the soft and hard palate. Four parameters were studied in the captured pictures after correction for the distortion deformity in fiberoptic endoscopic images: 1) length of soft palate, 2) length of uvula, 3) width of uvula, and 4) distance between posterior pillars.

RESULTS

Analysis showed that habitual snorers, compared with healthy volunteers have significantly increased soft palate length (P = .00001), increased uvula length (P = .0002) and width (P = .00001), and narrowed oropharyngeal isthmus (distance between the posterior pillars) (P = .04). In patients studied after LAUP, the length of the soft palate is significantly shorter (P = .00001) than in the preoperative cohort, and the oropharyngeal isthmus is significantly narrower (P = .00001). Moreover, this latter distance is significantly narrower (P = .00001) when compared with healthy volunteers.

CONCLUSIONS

Habitual snorers have a long soft palate, a long wide uvula, and a narrowed oropharyngeal isthmus. LAUP shortens and tightens the elongated palate and causes a further reduction in the space between the posterior pillars.

The influence of craniofacial structure on obstructive sleep apnea in young adults

PURPOSE

This study compares craniofacial measurements of lateral cephalometric radiographs of young obstructive sleep apnea patients with those of nonapneic snorers and controls.

PATIENTS AND METHODS

Forty-eight patients (BM=28.0+/-3.8) with obstructive sleep apnea, 25 patients (BMI=26.3+/-3.5) with nonapneic snoring, and 54 controls (BMI=24.8+/-2.7) were evaluated. All subjects were between 18 and 40 years of age. Nineteen lateral cephalometric measurements were performed by a single investigator blinded to the results of the polysomnograms.

RESULTS

Univariate logistic regression analysis of the 19 variables showed significantly increased midfacial height (ANS-N), narrowed middle airway space (MAS), steep mandibular plane angle (FMA), elongated pharynx (PNS-Eb), and inferiorly positioned hyoid bone (PNS-H, MP-H) in the obstructive sleep apnea group. The nonapneic snoring group showed only a tendency toward maxillary and mandibular retrognathia (SNA and SNB). No significant differences were found for cranial base angle (S-N-Ba), PAS, inferior airway space, maxillary unit length (ANS-PNS) mandibular unit length (Cd-Gn), tongue height (Tng-Ht), soft palate length (PNS-P), and palatal vault height (Ocl-Pal 6). The OSA group was also found to have multiple sites of abnormality of both the upper and lower pharynx, with 58% of the patients having two or more abnormal values (1 standard deviation from the mean) as opposed to 40% of the nonapneic snoring group.

CONCLUSIONS

Highly significant craniofacial abnormalities were found in the upper and lower pharynx in young obstructive sleep apnea patients. Most of these patients (58%) had abnormalities in both the upper and lower pharynx, suggesting that palatal surgery alone may be an inadequate treatment. This information may define future investigations needed to determine how to more effectively treat this subgroup of young obstructive sleep apnea patients.

Obstructive sleep apnoea syndrome: results and conclusions of a principal component analysis

A cephalometric analysis according to Hasund, supplemented by special obstructive sleep apnoea syndrome (OSAS) parameters, was performed on 169 patients who had been referred from the sleep laboratory. Statistical analysis showed a correlation between specific cephalometric landmarks including posterior airway space (PAS), a soft palate length, hyoid position and posterior growth development of the mandible and OSAS severity. A principal component analysis differentiated between four subgroups of OSAS patients: (1) orthognathic obese subjects; (2) patients with a long soft palate and low-positioned hyoid; (3) retrognathic patients with narrow PAS; and (4) prognathic ones. Lateral cephalometry is an important contribution to OSAS diagnostics and oral and maxillofacial therapy procedures.

Comparison of two dental devices for treatment of obstructive sleep apnea syndrome (OSAS)

Previous case reports have indicated dental devices can be an effective nonsurgical treatment for snoring and obstructive sleep apnea. This pilot study evaluated the effectiveness of two intraoral devices in reducing the Respiratory Disturbance Index (RDI) and Epworth Sleepiness Scale (ESS) scores in a group of 24 adult volunteers with a history of loud snoring. Subjects were randomly assigned to two groups. Twelve subjects were fitted with a dental device designed to increase vertical dimension and protrude the mandible (device A). The other 12 subjects received a different device designed to minimally increase vertical opening without protruding the mandible (device B). Unattended home sleep monitoring (Edentrace II Digital Recorder, Edentech Corp.) was used to compute RDI at two time periods: (T0) before using any dental device and (T1) while using a dental device 2 weeks after the initial delivery date. The mean RDI and ESS scores at T0 for subjects in the device A group were 35.6 +/- 28.4 and 12.0 +/- 3.9, respectively. Means for the same measures at T1 were 21.1 +/- 21.4 and 8.2 +/- 4.0. For subjects in the device B group, means for RDI and ESS scores at T0 were 36.5 +/- 43.7 and 13.0 +/- 4.5, the means at T1 were 46.8 +/- 47.0 and 12.5 +/- 5.7. The effectiveness of the two devices was estimated by comparing the difference in RDI scores from T0 to T1 for the 10 subjects who were using device A and completed the study and the 8 subjects who were using device B and completed the study. Six subjects withdrew for various reasons. From T0 to T1, device A reduced RDI scores in 9 of 10 subjects, with a mean reduction in RDI of 14.5 (p < or = 0.05) and in ESS score of 3.8 (p < or = 0.005). Device B showed no change or an increased RDI score in 8 of 8 subjects. Seven of the eight subjects who showed no improvement in RDI with device B were then fitted with device A. Four of these seven subjects showed a reduction in RDI and five showed a reduction in ESS after using device A for 2 weeks. The mean reduction in RDI and ESS was 2.4 +/- 19.8 and 2.4 +/- 3.0, respectively. Hence, we conclude that a dental device that advances the mandible and increases the vertical dimension to open the upper airway is more effective in reducing the number of apneic and snoring events during sleep than one which does not.

Contribution of craniofacial risk factors in increasing apneic activity among obese and nonobese habitual snorers

STUDY OBJECTIVE

To determine the role of craniofacial risk factors in increasing apneic activity between nonobese and obese habitual snorers.

DESIGN

Cross-sectional.

SETTING

Care-seeking volunteers identified through advertisements, and referral-based volunteers from two sleep centers serving the greater Cleveland area.

PATIENTS

The study included 142 habitual snorers (mean +/- SD, 45.5 +/- 10.6 years, 68% men; 20% African-Americans)

MEASUREMENTS AND RESULTS

Apneic activity was determined using unattended home sleep monitoring to assess the respiratory disturbance index (RDI). Independent variables included body mass index, cranial index, facial index, and 13 anatomic variables (lateral and frontal cephalometric radiographs were used to characterize craniofacial hard and soft tissues). A linear regression model explained approximately 54% and 53% of the variation in RDI (log transformed) scores for the nonobese and obese groups, respectively. The largest predictor of RDI in the nonobese group was tongue length, followed by alignment of the middle cranial fossa, and age. In the obese group, the largest predictor of RDI was hyoid to mandibular plane, followed by tongue length.

CONCLUSIONS

Measurements of soft tissues of the oropharynx (especially the tongue) are more closely associated with increased apneic activity. In addition, the hard tissue anatomic limits of the oropharynx may place nonobese individuals in the at-risk group. Therefore, anatomic relationships that are temporally stable may be useful to predict apneic activity in later years.

A three-dimensional airway assessment for the treatment of snoring and/or sleep apnea with jaw repositioning intraoral appliances: a case study

The purpose of this snoring/sleep apnea study was to assess the role of 3-D magnetic resonance imaging (MRI) of the airway correlated to jaw reposturing/intraoral appliance design. A clinical case is presented utilizing this technology, integrating a diagnostic baseline and follow-up sleep study/ polysomnograph. The baseline polysomnography, prior to jaw repositioning appliance design, indicated a respiratory disturbance index (RDI) of 21.5 hypopnea/apneas per hour. The follow-up sleep study, with use of an intraoral repositioning appliance, showed a 3.9 per hour RDI, an 82% RDI reduction/improvement. Magnetic resonance TMJ and airway images were done. The MRI enhanced airway assessment computer software program analyzed the 3-dimensional volume and cross sectional area changes from hard/soft palate junction to epiglottis. Imaged were the oropharynx nasopharynx and hypopharynx regional anatomy. The baseline, without mandibular positioning device, showed a total airway volume of 5,801.31 cubic mm, whereas with the mandibular positioning device in place, the total airway volume was increased to 8,657.22 cubic mm or a total increased volume of 32%. The largest improvement site in the airway was the mid-soft palatal uvula/nasopharynx region, with base of tongue moving forward. Along with traditional polysomnography, 3-dimensional MRI airway imaging should be considered as a diagnostic procedure in assessing sleep apnea patients. The necessity of a combined medical/dental team approach is emphasized.

Cephalometric assessment in obstructive sleep apnea

It is reported that some specific craniofacial characteristics are associated with obstructive sleep apnea syndrome (OSAS). To test this finding, the present study developed and assessed the feasibility of a craniofacial index score (CIS) in differentiating patients with OSAS from habitual snorers. Anthropometric measurements and lateral head radiographs were obtained on 24 male and 4 female patients with OSAS who had physician-diagnosed OSAS (respiratory disturbance index (RDI) >20), and 25 male and 5 female habitual snorers (RDI <20). Thirteen cephalometric and four anthropometric measure- ments were used in a discriminant model to construct the CIS. The model was able to correctly classify 82.1% of the OSAS group and 86.7% of the snoring group. In addition, variables that were related to the soft tissues, hyoid bone to mandibular plane, Body Mass Index, and soft palate length had the highest predictive value. These findings indicate that a CIS constructed from cephalometric and anthropometric measurements can be used to identify subjects with and without OSAS.

Craniofacial structure and obstructive sleep apnea syndrome--a qualitative analysis and meta-analysis of the literature

The etiologic relevance of craniofacial structure to obstructive sleep apnea syndrome (OSAS) is controversial yet the premise of a causal association serves to justify many treatments. A qualitative and quantitative analysis of the literature was performed to examine the foundation for any relationship between craniofacial structure and OSAS. A MEDLINE search and investigation of the published and unpublished literature on diagnostic imaging and OSAS was toxonomically arranged. Each sample study was evaluated by using the following criteria: (a) appropriate control group, (b) "blinding" of evaluators, (c) reliability measured, (d) random assignment of treatment, and (e) "success" was defined adequately in efficacy studies. Morphologic variables were combined among studies and compared with controls drawn from either the same patient pool as the OSAS group, or matched for gender, age, and body mass index. Analysis revealed 32 review articles, 16 case reports, and 95 sample studies. Only seven sample studies drew a control group from the same patient pool, whereas five used matched controls. Only one of these studies satisfied all the qualitative criteria. Of the treatment efficacy studies, 10 defined outcome adequately. However, none of these met all the qualitative criteria. The most consistent, strong effect sizes with the highest potential diagnostic accuracies were for mandibular plane to hyoid, mandibular plane angle, and mandibular body length. Only mandibular body length demonstrated a clinically significant association with and diagnostic accuracy for OSAS. However, since this variable's controls were selected from the literature, possible explanations for a positive association include methodologic differences between studies, varying magnification factors, and morphologic differences.

Cephalometric comparison of characteristics in chronically snoring patients with and without sleep apnea syndrome

OBJECTIVE

The purpose of this investigation is to cephalometrically study 50 snoring patients with and without sleep apnea and to determine whether cephalograms can be used as a diagnostic tool to differentiate persons who are chronic snorers from persons with sleep apnea.

STUDY DESIGN

A sample of 30 sleep apnea patients was compared with a sample of 20 chronic snorers without sleep apnea as documented by polysomnography. Forty cephalometric measurements were determined to study various skeletal, soft tissue, and airway abnormalities.

RESULTS

This study showed that both groups presented multiple cephalometric abnormalities. Only four measurements differed significantly between the two samples. In the sleep apnea group the maxilla was retropositioned and the hypoid bone displaced inferiorly and distally as compared to nonapneic snorers.

CONCLUSIONS

Because of the overall presence of abnormal cephalometric findings in both samples and given similar age and weight ranges, a differential diagnosis between chronic snorers with and without sleep apnea cannot be reliably based on standard cephalometric evaluation alone.

Morphology of the viscerocranium in obstructive sleep apnoea syndrome--cephalometric evaluation of 400 patients

The aim of this study was the cephalometric evaluation of patients with obstructive sleep apnoea in order to see whether certain craniofacial characteristics exist. Additional to known skeletal facial parameters cephalometric analysis has been used to establish pharyngeal dimensions. Surprisingly, many patients with obstructive sleep apnoea (nearly 40%) showed certain craniofacial characteristics which apparently predispose to pharyngeal obstruction and to obstructive sleep apnoea. More than one third of 400 patients prove to have pharyngeal narrowing combined with more or less distinct maxillary and mandibular deficiency. Cephalometric evaluation helps to identify sleep apnoea patients, in whom maxillomandibular advancement surgery might be effective in the treatment of obstructive sleep apnoea. According to our results, an indication for surgical treatment by maxillomandibular advancement exists in patients with maxillary and especially mandibular deficiency combined with pharyngeal narrowing.

Craniofacial cephalometric evaluation in habitual snorers with and without obstructive sleep apnea

Cephalometry has been used to evaluate soft tissue and craniofacial dimensions in moderate-to-severe obstructive sleep apnea syndrome (OSA), but rarely in habitual snoring, the preclinical stage of OSA. This study deals with craniofacial bone measurements in a sample of 28 male habitual snorers with and without OSA, and 10 healthy non-snorers. Habitual snorers showed a significant decrease in sagittal dimensions of the cranial base and mandibular bone; there was also a shorter maxilla in group B (apnea plus hypopnea index more than 10) with respect to group A (apnea plus hypopnea index less or equal to 10). Facial height and angle dimensions were not different between snorers and non-snorers. These findings indicate that some habitual snorers may have some anatomic disposition to upper airway obstruction during sleep.

Surgical correction of nasal obstruction in the treatment of mild sleep apnoea: importance of cephalometry in predicting outcome

BACKGROUND

A study was undertaken to determine if cephalometric radiographs could identify those who will benefit from nasal surgery in patients with a sleep apnoea hypopnoea syndrome (SAHS) and chronic nasal obstruction.

METHODS

Fourteen patients with SAHS were enrolled. Those with normal posterior airway space and mandibular plane to hyoid bone distances on preoperative cephalometric radiographs were matched with those with abnormal cephalometry for the frequency of sleep disordered breathing and body mass index. Polysomnographic studies (all subjects) and nasal resistance measurements (n = 10) were performed one to three months before and two to three months after surgery (septoplasty, turbinectomy, and polypectomy).

RESULTS

There was no difference in the baseline results of the polysomnographic studies between the two groups of patients. Nasal resistance decreased from a mean (SE) value of 2.9 (0.3) cm H2O/l/s before surgery to 1.4 (0.1) cm H2O/l/s after surgery in the normal cephalometry group and from 2.7 (0.3) cm H2O/l/s to 1.3 (0.3) cm H2O/l/s in the other group. The apnoea + hypopnoea index returned to normal (< 10 breathing abnormalities/hour) in all but one subject with normal cephalometric measurements, and sleep fragmentation improved with a decrease in the arousal index from 23.9 (3.3)/hour at baseline to 10.6 (2.5)/hour after surgery. Both of these parameters remained unchanged after surgery in the patients with abnormal cephalometry.

CONCLUSIONS

Normal cephalometry is helpful in identifying patients with mild SAHS and nasal obstruction who will benefit from nasal surgery. The presence of craniomandibular abnormalities makes it unlikely that nasal surgery will improve sleep related breathing abnormalities.

Cephalometric measurements in snorers, non-snorers, and patients with sleep apnoea

Cephalometry is often used to assess patients with sleep apnoea but whether these measurements differ from those in non-apnoeic snorers and how they are influenced by age is not clear. Cephalometric radiographs of patients with sleep apnoea were compared with those of snorers without sleep apnoea and those of non-snorers. Fifty two snorers with suspected sleep apnoea had a conventional sleep study and were divided into two groups: those with an apnoea-hypopnoea index greater than 10/h (n = 40, sleep apnoea group) and those whose apnoea-hypopnoea index was 10/h or less (n = 12, snorer group). The cephalometric measurements in these patients were compared with those of 34 non-snoring control subjects. Controls were subdivided into two groups: control group 1 included 17 subjects similar in age to the sleep apnoea and snorer groups (mean (SD) age 50.0 (10.9), 50.7 (9.4), and 50.6 (9.7) years); control group 2 included 15 young men (25.4 (2.6) years). The distance from the mandibular plane to the hyoid bone (MP-H) and the length of the soft palate were greater in the patients with sleep apnoea (28.7 (7.8) and 43.6 (5.0) mm) than in the snorers (23.7 (4.2) and 40.3 (4.9 mm). The MP-H was similar in snorers and age matched control subjects, but was significantly greater in the older than in the younger control subjects (22.1 (6.1) vs 17.0 (6.8]. The soft palate was longer in subjects who snored (both sleep apnoea patients and snorers) than in control subjects. The MP-H distance significantly correlated with age for all subjects (snorers and controls) and for the control subjects alone. This study shows that non-apnoeic snorers have cephalometric abnormalities that differ from those of patients with sleep apnoea and that cephalometric values are influenced by the subject's age.

Cephalometric analysis of permanently snoring patients with and without obstructive sleep apnea syndrome

Habitual heavy snoring may be considered a preliminary stage of sleep apnea syndrome. This investigation deals with the craniofacial morphology of 51 heavily snoring patients, with and without obstructive sleep apnea, and with 28 healthy control patients. The apnea group showed a reduced posterior airway and a posterior rotation of the mandible. Reduction of the anterior-posterior diameter of the cranial base, maxilla and mandible and vertical reduction of the posterior facial height appeared to be common facial characteristics in both snoring and apnea patients. These findings indicate an anatomical disposition for snoring and apnea.

Cephalometric analysis of long-term airway space changes with maxillary osteotomies

The cephalometric radiographs of 13 patients without sleep apnea who had undergone isolated maxillary surgery were studied. The authors found increases in both the nasopharyngeal and hypopharyngeal airway spaces 3 to 5 years after surgery. The results suggest that adaptive processes occur in both the upper and lower jaw, which contribute to an enlarged airway after surgery.

Severity of obstructive sleep apnea

A four-level severity scale for obstructive sleep apnea is offered using four criteria: maximum oxygen desaturation, apnea/hyponea index, symptoms of excessive day-time sleepiness, and symptoms of related cardiac disease. Oxygen desaturation and the apnea/hyponea index for 175 patients, all having had uvulopalatopharyngoplasty surgery, showed 19% mild, 33% moderate, 17% moderately severe, and 31% severe obstructive sleep apnea. There was a very poor correlation between oxygen desaturations and number of obstructive events, which demands that both be used in any estimation of disease severity.