Effect of body position on tongue posture in awake patients with obstructive sleep apnoea

Small airway resistance in obese and nonobese patients with obstructive sleep apnea syndrome using impulse oscillometry

Background/aim

There is limited information on the pathologic changes in the small airways among obese and nonobese patients with obstructive sleep apnea syndrome (OSAS). Impulse oscillometry (IOS) measures airway resistance and reactance independently of patient effort. This study aimed to compare airway resistance in small airways using IOS between obese and nonobese patients with OSAS.

Materials and methods

In this real-life cross-sectional study, demographic information was collected from obese and nonobese subjects diagnosed with moderate and severe OSAS without any other underlying diseases. Spirometry and IOS measurements were conducted, and the values of both groups were statistically analyzed.

Results

The nonobese group had a mean age of 45.6 ± 11.7 years (median 45), while the obese group had a mean age of 48.4 ± 9.5 years (median 47.5). The mean body mass index (BMI) for the nonobese group was 26.2 ± 2.1 kg/m2 (median 27 kg/m2), and for the obese group, it was 35.6 ± 6.4 kg/m2 (median 33 kg/m2). Statistically significant differences were observed between the two groups in R5 - R20 percentage, reactance area (AX), and resonant frequency (Fres) values (p < 0.05).

Conclusion

Among obese OSAS patients, there is an increase in resistance in small airways as indicated by IOS values. IOS shows promise as a potential screening tool for diagnosing OSAS.

Characteristics of airway resistance in obstructive sleep apnea patients with asthma on oscillometry

BACKGROUND

Asthma and obstructive sleep apnea (OSA) are prevalent chronic respiratory disorders with a high tendency to coexist. Both diseases involve increased airway resistance in the upright position because of narrow upper or lower airways. Moreover, there is a marked increase in airway resistance in the supine position in patients with OSA. We verified the characteristics of OSA in combination with asthma.

METHODS

Airway resistance was measured by oscillometry in the upright and supine position in 11 healthy participants (control), 59 patients with OSA alone, and 33 OSA patients with asthma (coexistence) in the hospital between April 2014 and July 2020. We compared the differences in airway resistance between the upright and supine positions among the three groups. In addition, we performed cephalometry to evaluate the upper airway structure in patients with OSA alone and in patients with both OSA and asthma.

RESULTS

A marked increase in airway resistance due to postural change was observed in the "OSA alone" group compared to that in the control group. However, this was not observed in the "coexistence" and control groups. Moreover, the "coexistence" group had fewer structural abnormalities in the upper airway than the "OSA alone" group on cephalometry.

CONCLUSIONS

The airway resistance of patients with OSA alone markedly increased with posture change because of upper airway abnormalities. However, there was a smaller increase with postural changes in OSA patients with asthma, suggesting the possibility of a smaller degree of upper airway abnormality compared to patients with OSA alone.

CLINICAL TRIAL REGISTRATION NUMBER

This study is approved by the research ethics committee of the Shinshu University School of Medicine (permission number: 4272).

Reduced Tongue Mobility: An Unrecognised Risk Factor of Childhood Obstructive Sleep Apnoea

STUDY OBJECTIVES

Childhood obstructive sleep apnoea (OSA) is an important and prevalent disease. A short lingual frenulum is a risk factor for OSA, but whether tongue mobility also plays a role in OSA aetiology remains unknown. This study aimed to examine tongue mobility in children with and without OSA. We hypothesized that reduced tongue mobility was associated with OSA. We also evaluated the relationship between tongue mobility and craniofacial profile.

METHODS

This was a cross-sectional case-control study. Prepubertal Chinese children aged 5-12 years, suspected to have OSA were recruited from our sleep disorder clinic. All subjects underwent overnight polysomnography (PSG). The lingual frenulum was evaluated based on tongue mobility and free tongue length. Craniofacial measurements were assessed by lateral cephalometry.

RESULTS

Eighty-two subjects (mean age: 8.32 ± 1.70 years, 57 males) were recruited. The mean tongue mobility was 58.2 (±19)% and 67.4 (±15)% (p=0.019) in subjects with and without OSA, respectively. Tongue mobility was inversely correlated with OAHI (r=-0.218, p=0.049). In multivariate logistic regression, low tongue mobility was independently associated with a higher risk of OSA after adjustment for age, sex, BMI z-score, presence of large tonsils and turbinates and nocturnal oral breathing (odds ratio=3.65, 95% CI= 1.22-11.8). Tongue mobility was found to correlate with the cranial base angle (Ba-S-N) (r=0.262, p=0.018), which determines the relative position of the mandible.

CONCLUSIONS

In pre-pubertal children, reduced tongue mobility is associated with the occurrence and severity of OSA. Assessing tongue mobility is recommended in childhood OSA management.

Evaluation of tongue volume and oral cavity capacity using cone-beam computed tomography

The aims of this study were to reveal the usefulness of a newly developed method for measuring tongue volume (TV) and oral cavity capacity (OCC) and to assess the relationship between them. The tongue was coated with a contrast agent, and the TV and OCC were determined using cone-beam computed tomography (CBCT). We enrolled 20 adults who were scheduled to undergo CBCT to evaluate the relationship of the third molar roots to the alveolar nerve before molar extraction. Each participant’s tongue was coated with a contrast agent, and CBCT of the tongue and oral cavity was performed. Using computer software, we evaluated reconstructed 3D images of the TV, oral cavity proper volume (OCPV), and OCC. The mean TV was 47.07 ± 7.08 cm³. The mean OCPV and OCC were 4.40 ± 2.78 cm³ and 51.47 ± 6.46 cm³, respectively. There was a significant correlation between TV and OCC (r = 0.920; p < 0.01) but not between TV and OCPV. The mean TV/OCC ratio was 91 ± 5%. The proposed method produced CBCT images that enabled effective measurement of TV and OCC. This simple method of measuring TV and OCC will be useful in the diagnosis on the tongues with abnormal size.

Craniocervical Posture in Patients with Obstructive Sleep Apnea

INTRODUCTION

Obstructive Sleep Apnea (OSA) is characterized by repeated episodes of upper airway obstruction during sleep.

OBJECTIVE

The objective of this study is to verify the craniofacial characteristics and craniocervical posture of OSA and healthy subjects, determining possible relationships with the apnea/hypopnea index (AHI).

METHODS

This case-control study evaluated 21 subjects with OSA, who comprised the OSA group (OSAG), and 21 healthy subjects, who constituted the control group (CG). Cephalometry analyzed head posture measurements, craniofacial measurements, and air space. Head posture was also assessed by means of photogrammetry.

RESULTS

The groups were homogeneous regarding gender (12 men and 9 women in each group), age (OSAG = 41.86 ± 11.26 years; GC = 41.19 ± 11.20 years), and body mass index (OSAG = 25.65 ± 2.46 kg/m2; CG = 24.72 ± 3.01 kg/m2). We found significant differences between the groups, with lower average pharyngeal space and greater distance between the hyoid bone and the mandibular plane in OSAG, when compared with CG. A positive correlation was found between higher head hyperextension and head anteriorization, with greater severity of OSA as assessed by AHI.

CONCLUSION

OSAG subjects showed changes in craniofacial morphology, with lower average pharyngeal space and greater distance from the hyoid bone to the mandibular plane, as compared with healthy subjects. Moreover, in OSA subjects, the greater the severity of OSA, the greater the head hyperextension and anteriorization.

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.

Non-apneic snoring and the orthodontist: radiographic pharyngeal dimension changes with supine posture and mandibular protrusion

OBJECTIVE

To evaluate the radiographic changes that occur in the pharynx and surrounding structures with alteration of posture from the upright to the supine position and the effect that mandibular protrusion whilst supine has on these dimensions.

DESIGN

Prospective cephalometric study.

SETTING

University Dental Hospital and School.

SUBJECTS AND METHOD

This prospective study involved 35 consecutively referred adults with proven non-apneic snoring. Lateral skull radiographs were obtained with the subjects upright in occlusion, supine in occlusion and supine with the mandible protruded to the maximum comfortable position. Radiographs were traced and digitized, and the pharyngeal dimensional changes and hyoid position were examined. Males and females were examined separately.

RESULTS

Radiographic pharyngeal dimensions were changed with altered posture, resulting in significant reductions in the minimum post-palatal (p<0.01) and post-lingual (p<0.05) airway measurements in the supine position. Mandibular protrusion whilst in the supine position produced increases in the functioning space for the tongue.

CONCLUSION

A supine posture results in significant reductions in pharyngeal airway measurements of non-apneic snorers. Mandibular protrusion whilst in the supine position produces an increase in the functioning space for the tongue.

The relationship between upper airways and craniofacial morphology studied in 3D. A CBCT study

OBJECTIVES

To assess whether morphology and dimension of the upper airway differ between patients characterized by various craniofacial morphology.

SETTING AND SAMPLE POPULATION

Ninety young adult patients from the Postgraduate Clinic, Section of Orthodontics, Department of Dentistry, Health, Aarhus University, Denmark, with no obvious signs of respiratory diseases and no previous adeno-tonsillectomy procedures. Thirty patients were characterized as Class I (-0.5 < ANB < 4.5), 30 as Class II (ANB > 4.5), and 30 as Class III (ANB < -0.5).

MATERIAL AND METHODS

Cone-beam computed tomography (CBCT) scans obtained in a supine position for all patients. Cephalometric landmarks were identified in 3D. Sagittal and transversal dimensions, cross sections, and partial and total volumes of the upper airway were correlated with the cephalometric measurements in all three planes of space. The cross-sectional minimal area of the upper airway was assessed as well.

RESULTS

No statistical significant relationships between dimension and morphology of upper airways and skeletal malocclusion were found.

CONCLUSION

Differences in craniofacial morphology as identified by the sagittal jaw relationship were not correlated with variation in upper airway volumes. A clinical significant relation was detected between minimal area and total upper airway volume.

Craniofacial contribution to residual obstructive sleep apnea after adenotonsillectomy in children: a preliminary study

STUDY OBJECTIVES

Pediatric obstructive sleep apnea (OSA) is frequently associated with adenotonsillar hypertrophy, and the fact that about 30% of affected children continue to show OSA after adenotonsillectomy (AT) suggests the presence of some other predisposing factor(s). We hypothesized that abnormal maxillofacial morphology may be a predisposing factor for residual OSA in pediatric patients.

METHODS

A total of 13 pediatric OSA patients (9 boys and 4 girls, age [median (interquartile range)] = 4.7 (4.0, 6.4) y, body mass index (BMI) z score = -0.3 (-0.8, 0.5)) who had undergone AT were recruited for this study. Maxillomandibular size was measured using an upright lateral cephalogram, and correlations between size and the apnea hypopnea index (AHI) values obtained before (pre AT AHI) and about 6 months after AT (post AT AHI) were analyzed.

RESULTS

AHI decreased from 12.3 (8.9, 26.5)/h to 3.0 (1.5, 4.6)/h after AT (p < 0.05). Residual OSA was seen in 11 of the 13 patients (84.6%) and their AHI after AT was 3.1 (2.7, 4.7)/h. The mandible was smaller than the Japanese standard value, and a significant negative correlation was seen between maxillomandibular size and post AT AHI (p < 0.05).

CONCLUSIONS

These findings suggest that the persistence of OSA after AT may be partly due to the smaller sizes of the mandible in pediatric patients. We propose that the maxillomandibular morphology should be carefully examined when a treatment plan is developed for OSA children.

Inhomogeneous neuromuscular injury of the genioglossus muscle in subjects with obstructive sleep apnea

PURPOSE

Muscle injury exists in the upper airway in subjects with obstructive sleep apnea (OSA). However, whether this injury is homogeneous remains unclear. The objective of this study was to measure neuromuscular changes in the anterior and posterior genioglossus muscle (GG) in subjects with OSA using motor unit potentials (MUPs).

METHODS

Male subjects underwent diagnostic sleep studies to obtain apnea/hypopnea index (AHI) and lowest oxygen saturation (LSAT) data. MUPs of the anterior and posterior GG were recorded. Mean values and outliers of MUP parameters were analyzed.

RESULTS

Seventeen subjects with severe OSA (AHI, 72.3 ± 16.7 events/h) and nine control subjects (AHI, 3.7 ± 0.4 events/h) were enrolled in this study. In the control group, the MUP values of amplitude, duration, area, area/amplitude, and size index did not differ significantly between the posterior and anterior GG. In the OSA group, these values were significantly higher in the posterior than anterior GG (amplitude: P = 0.011; duration: P = 0.007; area: P = 0.008; size index: P = 0.033). Posterior GG values were greater in the OSA group than in the control group, whereas anterior values were similar. A larger proportion of subjects with OSA had outlying values for the posterior GG than anterior GG (52.9 vs. 11.8%; P < 0.05). No significant correlation between MUP parameters and body mass index, AHI, or LSAT was observed in the OSA group.

CONCLUSIONS

Chronic neuromuscular injury in subjects with OSA was more severe in the posterior than in the anterior GG.

Change in upper airway geometry between upright and supine position during tidal nasal breathing

BACKGROUND

As the upper airway is the most important limiting factor for the deposition of inhalation medication in the lower airways, it is interesting to assess how its morphology varies between different postures. The goal of this study is to compare the upper airway morphology and functionality of healthy volunteers in the upright and supine positions during tidal nasal breathing and to search for baseline indicators for these changes. This is done by performing three-dimensional measurements on computed tomography (CT) and cone beam computed tomography (CBCT) scans.

METHODS

This prospective study was approved by all relevant institutional review boards. All patients gave their signed informed consent. In this study, 20 healthy volunteers (mean age, 62 years; age range, 37-78 years; mean body mass index, 29.26; body mass index range, 21.63-42.17; 16 men, 4 women) underwent a supine low-dose CT scan and an upright CBCT scan of the upper airway. The (local) average (Savg) and minimal (Smin) cross-sectional area, the position of the latter, the concavity, and the airway resistance were examined to determine if they changed from the upright to the supine position. If changes were found, baseline parameters were sought that were indicators for these differences.

RESULTS

There were five dropouts due to movement artifacts in the CBCT scans. Savg and Smin were 9.76% and 26.90% larger, respectively, in the CBCT scan than in the CT scan, whereas the resistance decreased by 26.15% in the upright position. The Savg of the region between the hard palate and the bottom of the uvula increased the most (49.85%). In people with a high body mass index, this value changed the least. The airway resistance in men decreased more than in women.

CONCLUSIONS

This study demonstrated that there are differences in upper airway morphology and functionality between the supine and upright positions and that there are baseline indicators for these differences.

The effect of posture on Cheyne-Stokes respirations and hemodynamics in patients with heart failure

STUDY OBJECTIVES

Cheyne-Stokes respirations occur in 40% of patients with heart failure. Orthopnea is a cardinal symptom of heart failure and may affect the patient's sleeping angle. The objective of this study was to assess the respiratory and hemodynamic response to sleeping angle in a group of subjects with stable heart failure.

DESIGN

Twenty-five patients underwent overnight polysomnography with simultaneous and continuous impedance cardiographic monitoring. Sleeping polysomnographic and impedance cardiographic data were recorded.

SETTING

The study was conducted in a sleep center.

PATIENTS

All 25 patients had clinically stable heart failure and left ventricular ejection fractions < 40%.

INTERVENTIONS

The patients slept at 0 degrees, 15 degrees, 30 degrees, and 45 degrees in random order.

MEASUREMENTS AND RESULTS

Seventeen patients had Cheyne-Stokes apneas (index > 5/h) and 23 patients had hypopneas (index > 5/h). The hypopnea index showed no response to sleeping angle. The Cheyne-Stokes apnea index decreased with increasing sleeping angle (P < 0.001). This effect was seen only during supine sleep and non-rapid eye movement sleep and was absent in non-supine sleep, rapid eye movement sleep, and during periods of wakefulness. Thoracic fluid content index and left ventricular hemodynamics measured by impedance cardiography showed no response to sleeping angle.

CONCLUSIONS

Changing the heart failure patient's sleeping angle from 0 degrees to 45 degrees results in a significant decrease in Cheyne-Stokes apneas. This decrease occurs on a constant base of hypopneas. The changes in Cheyne-Stokes apneas are not related to changes in lung congestion and left ventricular hemodynamics.

Comparison of speech production in upright and supine position

Speech is usually produced in an upright sitting or standing posture. Measurements and judgments of speech may be made in conditions requiring a supine position, however. These conditions include MRI recordings, and oral procedures, such as, adjustments to dental appliances, medical and surgical procedures. It is of interest, therefore, to see whether gravity has strong or systematic effects on tongue behavior. In the present study, 13 subjects repeated several words, which contained extreme consonant and vowel tongue positions, during upright and supine condition. Ultrasound imaging provided midsagittal tongue contours, in each condition, for comparison. A neck brace was used to stabilize transducer placement and the palate was used as a physiological reference to register the data sets. Results showed a significant subject effect. In supine position the tongue was more posterior than upright for seven subjects, more anterior for two subjects and varied by phoneme for four subjects. However, there was no significant phoneme effect. The direction of change and the amount of change were not directly related. Most subjects had small upright-supine differences. The largest differences, less than 3 mm on average, were in the posterior tongue.

Oral appliance titration and nasal resistance in nonapneic subjects

Initial mandibular position might be a key factor leading to rapid therapeutic outcome in oral appliance therapy for patients with obstructive sleep apnea (OSA). The purpose of this study was to investigate the effects of an adjustable oral appliance on nasal resistance in 7 nonapneic patients. Upright and supine nasal resistance was measured for each subject with an adjustable oral appliance in place in 3 mandibular positions: most retruded (MAX0), maximum protrusion (MAX100), and 67% of MAX100 (MAX67). A significant decrease in upright and supine nasal resistance was observed between MAX0 and MAX67 (P < .01), and between MAX0 and MAX100 (P < .01), but not between MAX67 and MAX100. In addition, there was a positive correlation between the nasal resistance at MAX0 and the nasal resistance change from MAX0 to MAX67 (P < .01), indicating that when the mandible was advanced from MAX0 to MAX67, the more nasal resistance at MAX0, the greater the reduction in nasal resistance at MAX67. These findings suggest that MAX67 might be indicated as the initial mandibular position and that gradual anterior titration of mandibular position beyond MAX67 would give OSA patients rapid therapeutic effects by reducing the nasal resistance. Moreover, OSA patients with augmented nasal resistance at MAX0 might have a greater reduction in nasal resistance in response to MAX67 in oral appliance therapy.

Oral airway resistance during wakefulness in eucapnic and hypercapnic sleep apnea syndrome

The purpose of this study was to evaluate whether there was an abnormal increase of upper airway resistance in the sitting and supine positions in hypercapnic obstructive sleep apnea syndrome (OSAS) patients compared with eucapnic OSAS or normal controls as measured by impulse oscillometry (IOS) while awake. Twenty subjects without OSAS served as controls (group I), and 20 patients with moderate or severe eucapnic OSAS (group II) and another eight hypercapnic severe OSAS patients (group III) were studied. Group II was further divided into two subgroups. Group IIa consisted of 14 subjects whose BMI was less than 35 and group IIb of six subjects whose BMI was greater than 35. All subjects also had an overnight sleep study. Oral airway resistance (AR) (including impedance (Zrs), resistance (R) and reactance (X)) was measured by impulse oscillometry (IOS) (MasterScreen IOS, VIASYS Healthcare GmbH, Germany) in the upright (seated) position and then in the supine position while awake. The results demonstrated that in both group I and group II, Zrs was normal in the sitting position. However, there was a high Zrs in the supine position for group II patients. In contrast, in group III patients, there was a high Zrs in both the sitting and supine positions. In conclusion, upper airway resistance was increased both sitting and supine in the hypercapnic OSAS patients; this would presumably increase the work of breathing and might explain why these subjects were hypercapnic while awake, while eucapnic OSAS patients and normal controls were not. Secondly, the increased upper airway resistance in the supine position in the eucapnic OSAS patients may contribute to their OSAS.

Supine-dependent changes in upper airway size in awake obstructive sleep apnea patients

The purpose of this study was to define the changes in upper airway size in response to a body position change from upright to supine. A total of 15 male Caucasian obstructive sleep apnea (OSA) patients with a mean apnea hypopnea index of 31.0 +/- 13.9/hr were recruited for this study. A set of upright and supine cephalograms was traced and digitized for each patient. The most constricted site in the upright position was located in the velopharynx. When the body position was changed from upright to supine, a significant reduction in the anteroposterior dimension was observed only at the level of the velopharynx (p < 0.05). Sagittal cross-sectional areas of the velopharynx and the oropharynx significantly decreased (p < 0.05), but the soft palate area increased (p < 0.05). We conclude that the velopharynx is not only the narrowest site in both upright and supine body positions but also the most changeable site in response to an alteration in body position during wakefulness. Backward displacement of the soft palate with a change in shape may reflect less functional compensation in the velopharynx than that in the oropharynx and the hypopharynx and partly explain why upper airway occlusion occurs primarily in the velopharynx in OSA patients.

Influence of mandibular protruding device on airway passages and dentofacial characteristics in obstructive sleep apnea and snoring

The aim of the study was to evaluate the influence of a mandibular protruding device (MPD) after 2 years of nocturnal use on the upper airway and its surrounding structures. Lateral cephalograms in the upright position were taken of patients with obstructive sleep apnea (OSA) and of patients with snoring problems at the beginning of treatment and at the 2-year follow-up. Two computer programs were used to analyze the cephalograms. A total of 65 patients, 44 with OSA and 21 snorers, were analyzed. The linear distances in the pharynx had increased significantly at the 2-year follow-up; the calculated pharyngeal area had increased on average by 9% (mean, +58.3 mm(2)). The velum area had decreased (mean, -31.5 mm(2)), which accounts for about half the increase in the relative area of the pharynx. The average linear distances between the hyoid bone and the 2 reference lines, ie, nasal line (NL) and mandibular line (ML), had increased significantly. Mandibular protrusion (SNB) was slightly reduced, on average -0.4 degrees (P <.01), and the lower incisors were proclined (ILi/ML), on average +1.5 degrees (P <.05). In conclusion, nocturnal use of an MPD for 2 years increased the airway passage because of an increase in the relative area of the pharynx by a mean of 9% in OSA patients and snorers. A mandibular posterior rotation and a proclination of the lower incisors were observed but considered modest.

The effect of posture and a mandibular protruding device on pharyngeal dimensions: a cephalometric study

The objectives were to evaluate the impact of body posture on cephalometric measures and the level and the extent to which treatment with a mandibular protruding device (MPD) affects pharyngeal width. The study was composed of 77 patients: 50 were diagnosed with obstructive sleep apnea (OSA) and 27 snored. After each patient underwent a baseline medical (including a somnographic registration), dental and stomatognathic examination, an MPD that would protrude the mandible 75% of the maximal protrusion range was fabricated. In a radiographic examination, four cephalograms were taken: two in the upright position with and without the MPD and two in the supine position with and without the MPD. The cephalometric measures focused on the pharyngeal structures. MPD treatment significantly increased the relative pharyngeal area (at the level of the oropharynx and the hypopharynx) by a mean of +89.6 mm2 (P < 0.01) in the upright posture. The relative pharyngeal area, however, was reduced by more than 50% in the supine position compared with the upright position, independent of MPD treatment. In the supine position, compared with upright, most pharyngeal measures decreased significantly; the hyoid was significantly lower and displaced posteriorly, and the area of the velum increased by a mean of +201.2 mm2 (P < 0.001). We conclude that the MPD significantly increased most pharyngeal measures except the linear distance between the hyoid bone and the third vertebra and decreased the area of the velum.

Mandibular Advancement Modulates Respiratory-Related Genioglossus Electromyographic Activity

The purpose of this study was to determine if mandibular advancement had any effects on the respiratory-related electromyographic (EMG) activity of the genioglossus (GG) muscle in normal adults for both the upright and supine positions. Spontaneous GG EMG activity during quiet nasal breathing was recorded in 5 mandibular positions: centric occlusion (CO), maximal protrusion (MAX), 25% (MAX25), 50%(MAX50), and 75%(MAX75) of MAX. The maximal GG EMG activities during inspiration (GGinsp) and minimal GG EMG activities during expiration (GGexp) were compared. The GGinsp and GGexp significantly increased with mandibular advancement in both body positions. Furthermore, there were significant differences in both GGinsp and GGexp between CO and more protruded mandibular positions. However, no significant differences were found in the GGinsp at MAX compared to that at MAX75, and in the GGexp at MAX compared to those at MAX75 and MAX50. These results suggest that augmentation of the respiratory-related GG EMG activity with mandibular advancement diminishes the propensity of the upper airway to collapse. Moreover, the lack of any remarkable difference between the GGinsp at MAX75 and that at MAX may be relevant to the effectiveness of oral appliances in the treatment of obstructive sleep apnea.

Supine Cephalometric Analyses of an Adjustable Oral Appliance Used in the Treatment of Obstructive Sleep Apnea

OBJECTIVE: To investigate the effects of the Klearway(TM) appliance on the upper airway in patients with obstructive sleep apnea (OSA) in the supine position. METHODS: Sixteen subjects (12 males and 4 females) were recruited on the basis of baseline polysomnography with a documented Apnea and Hypopnea Index (AHI) >15 per hour. A second overnight sleep study was performed for each subject with the appliance in place. Baseline supine cephalometry was performed for each subject before the initial insertion of the appliance, and follow-up supine cephalometry was undertaken with the appliance in place. RESULTS: The polysomnographic variables improved significantly, and the mean changes in overbite and overjet were 5.15 mm and 6.26 mm after insertion of the Klearway(TM) appliance. The supine sagittal cross-sectional areas of the pharynx and the tongue significantly increased, while the linear distance from the hyoid position to the mandibular plane or the RGN-C3 line significantly decreased after insertion of the appliance. The ratio of the vertical pharyngeal length to the sagittal cross-sectional area of nasopharynx or tongue decreased significantly. When the subjects were evaluated on the basis of the after-insertion AHI, the group with good response (n = 11) was found to be significantly younger than the group with the poor response (n = 5). Similarly, the good responders revealed less prominent chins, larger tongue heights, and an increase in hypopharyngeal sagittal cross-sectional area after insertion of the appliance. There was a significant correlation between the improvement in AHI (%) and the supine middle airway space (r = -0.52, p < 0.05). CONCLUSION: The mechanical effect of the Klearway(TM) appliance on the upper airway and the stabilization of jaw posture may be important determinants of the efficacy of the appliance.

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.

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

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

Dental considerations in upper airway sleep disorders: A review of the literature

STATEMENT OF PROBLEM

Upper airway sleep disorders are becoming recognized as common medical concerns. Multiple treatment options have been advocated, including the use of dental devices. Dental practitioners are being asked by the medical profession to become a part of the treatment team. This may be a challenging task because of the large number of dental devices available, rapid advancement in the understanding of this disease, and numerous publications.

PURPOSE

This article reviews the anatomic features and etiologic factors of upper airway sleep disorders and medical and dental treatment options.

METHODS

The literature review was conducted with an accepted literature research tool, PubMed, developed by the National Library of Medicine. Key words searched included "obstructive sleep apnea," "sleep apnea," "sleep disorders," and "snoring".

CONCLUSION

Dental devices are indicated in snoring and mild-to-moderate obstructive sleep apnea patients after medical evaluation and referral.

Oral airway resistance during wakefulness in patients with obstructive sleep apnoea

BACKGROUND

Patients with obstructive sleep apnoea (OSA) have a number of upper airway structural abnormalities which may influence the resistance of the oral airway to airflow. There have been no systematic studies of the flow dynamics of the oral cavity in such patients.

METHODS

Inspiratory oral airway resistance to airflow (RO) was measured in 13 awake patients with OSA in both the upright and supine positions (neck position constant). Each subject breathed via a mouthpiece while the nasal airway was occluded with a nasal mask.

RESULTS

In the upright position the mean (SE) RO was 1.26 (0. 19) cm H2O/l/s (at 0.4 l/s) which increased to 2.01 (0.43) cm H2O/l/s when supine (p<0.05, paired t test). The magnitude of this change correlated negatively with the respiratory disturbance index (r = -0.60, p = 0.03).

CONCLUSION

In awake patients with OSA RO is normal when upright but abnormally raised when in the supine position.

The effect of body posture on sleep-related breathing disorders: facts and therapeutic implications

The aggravating effect of the supine body position on breathing abnormalities during sleep was recognized from the earliest studies on sleep breathing disorders. Most of the anatomical and physiological correlates of this phenomenon appear to be due to the effect of gravity on the upper airway. Although few articles have been published on this topic, it has been shown in a large population of obstructive sleep apnoea (OSA) patients that more than half of them are Positional Patients, i.e. they have at least twice as many apnoeas/hypopnoeas during sleep in the supine posture as in the lateral position. This positional phenomenon is influenced by factors such as Respiratory Disturbances Index (RDI), Body Mass Index (BMI), age and sleep stages. The sleep supine posture not only increases the frequency of the abnormal breathing events but also their severity. This sleep posture also has a detrimental effect on snoring, as well as on the optimal CPAP pressure. Positional Therapy, i.e. the avoidance of the supine posture during sleep, is a simple behavioural therapy for many mild to moderate OSA patients. Unfortunately, only a few studies, including only a few patients, have investigated this form of therapy. Although the results of these studies are promising, the lack of a reliable long-term evaluation of its efficacy is perhaps an important reason why this form of therapy has not been widely accepted. Since mild to moderate OSA patients are the majority of the OSA patients and since without treatment, a large percentage of them will develop a more severe form of the disease, a thorough evaluation with a major emphasis on the long-term effectiveness of this form of therapy is urgently needed.