Neural and anatomic factors related to upper airway occlusion during sleep

Residual upper airway obstruction during nocturnal noninvasive ventilation despite high positive expiratory pressure. Impact of oronasal mask to nasal mask switch

BACKGROUND

Nasal mask (NM) and oronasal masks (OM) can be used to provide noninvasive ventilation (NIV). Recent studies suggested that OM is the most used interface and that there is no difference in efficacy or in tolerance between OM and NM for chronic use. However, studies focusing on video laryngoscopy underlined the impact of OM in residual upper airway obstruction (UAO) under NIV. We sought to assess the real-life practice of switching from OM to NM when UAO events persist despite high EPAP levels.

METHODS

In an open-label single center prospective cohort study, data from files and full night polysomnography on NM and OM were collected for patients wearing OM and presenting an UAO index ≥15/h despite an EPAP level ≥ 10 cmH20.

RESULTS

Forty-four patients were included in the study. In 31 patients (74 %), switching to a NM reduced UAOi to ≥10/h. Interestingly, 92 % of these patients still had NM at 3 to 12 months of follow-up. Switching to a NM was also associated with a trend in paCO2 reduction and significant improvements in Epworth, sleep quality and NIV compliance. Successful interface switching was significantly associated with female gender, and a trend was observed in non-smokers.

CONCLUSION

As for CPAP, switching to a NM improved NIV efficacy in a selected group of patients presenting residual UAO events despite high EPAP levels. Additionally, this switch has an impact on compliance and subjective sleepiness. Thus, in patients with persisting UAO on OM, switching to a NM could be a first-line intervention before considering further investigation such as polygraphy or video laryngoscopy. We also derive an algorithm for mask allocation and adaptation in acute and chronic NIV use.

The Effect of Bite Raise on AHI Values in Adult Patients Affected by OSA: A Systematic Review with Meta-Regression

Obstructive sleep apnea (OSA) is a highly prevalent sleep breathing disorder characterized by the collapse of the pharyngeal walls that entails recurrent episodes of cessation of breathing or decrease in airflow while sleeping. This results in sleep fragmentation, decreased oxygen saturation and an increase in the partial pressure of carbon dioxide, causing excessive daytime sleepiness, hypertension and increased prevalence of cardiovascular morbidity and mortality. Mandibular advancement devices (MAD) represent a valid alternative therapy to Continuous Positive Airway Pressure, thrusting the mandible forward, increasing the lateral diameter of the pharynx and reducing the collapsibility of the airway. Several investigations have focused on the detection of the best mandibular advancement amount in terms of effectiveness and tolerance, but few and contrasting data are available on the role of occlusal bite raise in reducing the apnea/hypopnea index (AHI). The aim of this systematic review with meta-regression analysis was to investigate the effect of the bite raise of MAD on AHI values in adult patients affected by OSA. An electronic search was performed in MEDLINE, the Cochrane Database, Scopus, Web of Science and LILACS. Randomized controlled trials (RCT) investigating the effectiveness of MAD in OSA patients were included. The quality of evidence was evaluated with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) and the risk of bias with the Cochrane risk-of-bias tool for randomized trials (RoB2). Six RCT were included. The success rate of each study was computed: (mean baseline AHI - mean post treatment AHI)/mean baseline AHI. The GRADE scores indicated that the quality of evidence was very low. The meta-regression analysis showed that there was no correlation between the occlusal bite raise and the AHI improvement.

Correlating Nasal Patency with Obstructive Sleep Apnea in Obese Versus Non-Obese Patients: An Acoustic Rhinometry Study

The aim of this study was to correlate nasal patency with Obstructive Sleep Apnea (OSA) in obese versus non-obese patients using Acoustic Rhinometry (AR). Eccovision® Acoustic Rhinometer equipment was used to compare nasal cross-sectional areas (CSA1,2 & 3 corresponding to nasal valve region, anterior portion of middle & inferior turbinate and posterior portion of middle & inferior turbinate respectively) and volume in age and gender matched sample divided into three groups: Group 1: Non-obese patients without OSA (25 patients, 13 males and 12 females); Group 2: Non-obese patients with OSA (25 patients, 14 males and 11 females); Group 3: Obese patients with OSA (25 patients, 13 males and 12 females). The mean nasal cross-sectional areas and volume were lower in Group 2 compared to Group 1 but statistically non-significant (P value > 0.05 for all). The mean nasal cross-sectional areas and volume were significantly lower in Group 3 as compared to Groups 1 and 2 (P value < 0.05 for all). BMI showed a statistically significant positive (direct) correlation with AHI in Groups 2 and 3 (P value < 0.05 for both). The nasal cross-sectional areas and volume showed a statistically significant negative (inverse) correlation with AHI in Groups 2 and 3 (P value < 0.05 for both). OSA diagnosed cases with high BMI may not present with an obvious nasal obstruction; the nasal patency may still be compromised due to reduced nasal lumen secondary to obesity. AR, being cost-effective and non-invasive modality; is advocated to evaluate pre-treatment nasal patency, as well as follow up evaluation to ascertain improvement after the intervention.

A computational model of upper airway respiratory function with muscular coupling

A two dimensional finite element model of upper airway respiratory function was developed emphasizing the effects of dilator muscular activation on the human retro-lingual airway. The model utilized an upright mid-sagittal computed tomography of the human head and neck to reconstruct relevant structures of the tongue, mandible, and the hyoid-related soft tissues, along with the retro-lingual airway. The reconstructed geometry was divided into fluid and solid domains and discretized into finite element (FE) meshes used for the computational model. Three cases were investigated: standing position; supine position; and supine position coupled with dilator muscle activation. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatio-temporal deformation of the structures surrounding the airway wall were predicted to be in general agreement with known changes from upright to supine posture on luminal opening, as well as the distribution of airflow. The model effectively captured the effects of muscular stimulation on the upper airway anatomical changes, the flow characteristics relevant to airway reduction in the supine position and airway enlargement with muscle activation. The smallest airway opening in the retro-lingual section is predicted to occur at the epiglottic region in all the three cases considered, an unexpected vulnerable location of airway obstruction. The model also predicted that hyoid displacement would be associated with recovery from airway collapse. This information may be useful for building more complex models relevant to mechanisms and clinical interventions for obstructive sleep apnea.

The Importance of Mask Selection on Continuous Positive Airway Pressure Outcomes for Obstructive Sleep Apnea. An Official American Thoracic Society Workshop Report

Continuous positive airway pressure (CPAP) remains the major treatment option for obstructive sleep apnea (OSA). The American Thoracic Society organized a workshop to discuss the importance of mask selection for OSA treatment with CPAP. In this workshop report, we summarize available evidence about the breathing route during nasal and oronasal CPAP and the importance of nasal symptoms for CPAP outcomes. We explore the mechanisms of air leaks during CPAP treatment and possible alternatives for leak control. The impact of nasal and oronasal CPAP on adherence, residual apnea-hypopnea index, unintentional leaks, and pressure requirements are also compared. Finally, recommendations for patient and partner involvement in mask selection are presented, and future directions to promote personalized mask selection are discussed.

Effects of miniscrew-assisted orthodontic treatment with premolar extractions on upper airway dimensions in adult patients with Class II high-angle malocclusion

INTRODUCTION

The primary aim of this study was to investigate the change in upper airway dimensions and in mandibular position after miniscrew-assisted treatment with premolar extractions in adult patients with Class II high-angle malocclusion. The secondary aim was to determine the correlation between changes in upper airway dimensions and changes in mandibular position in these patients.

METHODS

Eighteen adult patients with Class II high-angle malocclusion (mean ± standard deviation age = 21.2 ± 2.9 years) were selected retrospectively. All patients underwent 4 premolar extractions, and 2 miniscrews were implanted in the maxilla to intrude molar height. Cone beam computed tomography images were taken pretreatment and posttreatment for every patient. The primary outcome variable for the upper airway was the minimal cross-sectional area of the upper airway (CSA_min), and the primary outcome variables for the mandible were mandibular rotation (Mp-SN angle), mandibular horizontal position (SNB angle), and mandibular vertical position (ANS-Me distance).

RESULTS

The CSA_min significantly increased by 47.2 mm² (t = -2.26, P = 0.04) after orthodontic treatment. The mandible significantly rotated counterclockwise by 0.9° (t = 2.20, P = 0.04) after treatment, which consisted of forward movement of 1.2° (t = -4.30, P = 0.00) and upward movement of 1.3 mm (Z = -1.98, P = 0.05). Furthermore, the change of the CSA_min showed a significant correlation with the change of the ANS-Me (P = 0.01).

CONCLUSIONS

By using miniscrews to intrude maxillary molars, orthodontic premolar extraction treatment results in mandibular counterclockwise rotation, and upper airway dimensions increase in Class II high-angle young adult patients. The increase of the upper airway dimensions significantly correlates to the upward movement of the mandible.

Chronic Nasal Obstruction Causes Daytime Sleepiness and Decreased Quality of Life Even in the Absence of Snoring

Background

There has been a growing awareness that nasal obstruction may impair various daily and social activities. We performed a questionnaire survey in a working population to clarify the contribution made by snoring concomitant with nasal obstruction to daytime sleepiness and quality of life (QOL).

Methods

Seven thousand nine hundred eighty daytime workers were asked to complete questionnaires, 7702 responded, and the data from 3442 subjects were finally analyzed. Nasal obstruction and snoring were graded into three and four categories, respectively. Daytime sleepiness and QOL were assessed by the Epworth Sleepiness Scale (ESS) and the Medical Outcomes Study 36-Item Short-Form Health Survey, respectively.

Results

Subjects with chronic nasal obstruction, even if snoring was absent, reported significantly higher ESS scores and lower QOL scores than control subjects, and the presence of habitual snoring had an additive influence on these changes. The ESS and mental QOL scores adjusted for age, sex, and body mass index showed the same tendency.

Conclusion

Induction of sleep-disordered breathing (SDB) is a possible cause of excessive daytime sleepiness and impaired QOL in subjects with nasal obstruction. A variant of SDB such as silent upper respiratory resistance syndrome may participate in this phenomenon in the absence of snoring.

Comparison of the upper airway dynamics of oronasal and nasal masks with positive airway pressure treatment using cine magnetic resonance imaging

PURPOSE

It is known that oronasal masks are not as effective at opening the upper airway compared to nasal only continuous positive airway pressure (CPAP) masks in patients with sleep-disordered breathing. However, the physiological mechanism for this difference in efficacy is not known; although, it has been hypothesized to involve the retroglossal and/or retropalatal region of the upper airway. The objective of this study was to investigate differences in retroglossal and retropalatal anterior-posterior space with the use of oronasal vs. nasal CPAP masks using real-time cine magnetic resonance imaging (cMRI).

METHODS

Ten subjects (eight men, two women) with obstructive sleep apnea (OSA) were given cMRI with both nasal and oronasal CPAP masks. Each subject was imaged with each interface at pressures of 5, 10, and 15 cm of H2O, while in the supine position along the sagittal plane.

RESULTS

The oronasal mask produced significantly less airway opening in the retropalatal region of the upper airway compared to the nasal mask interface. During exhalation, mask style had a significant effect on anterior-posterior distance p = 0.016. No differences were found in the retroglossal region between mask styles.

CONCLUSIONS

Our study confirmed previous findings showing differences in treatment efficacy between oronasal and nasal mask styles. We have shown anatomic evidence that the nasal mask is more effective in opening the upper airway compared to the oronasal mask in the retropalatal region.

Effects of varying mandibular protrusion and degrees of vertical opening on upper airway dimensions in apneic dentate subjects

INTRODUCTION

Despite numerous studies investigating the dimensional and therapeutic effects of mandibular advancement splints (MASs), data regarding the effects of differently designed individual and non-adjustable MASs on the upper airway in fully dentate apneic subjects in the sagittal plane including comparison of these effects with a placebo device are sparse. The present study aimed to determine the dimensional changes in the sagittal plane created by differently designed MASs in the upper airway in fully dentate apneic subjects and to compare these changes with the effects of a placebo device.

MATERIALS AND METHODS

Magnetic resonance (MR) images of 9 dentate apneic subjects with 5 differently designed MASs and without a MAS were obtained. We measured the area of the entire pharynx (velopharynx, oropharynx, hypopharynx) on these MR images and compared the dimensional changes.

RESULTS

The dimensional changes triggered by two specific MASs (75% of the maximum mandibular protrusion with 5 mm vertical opening, and 75% of the maximum mandibular protrusion with 10 mm of vertical opening) in the entire pharynx in the sagittal plane were statistically significant compared to the other MASs (p < 0.05). The MAS effecting 75% of the maximum mandibular protrusion and 10 mm of vertical opening created a significant dimensional increase only in the velopharyngeal area among the three pharyngeal sites (p ≤ 0.003).

CONCLUSION

While the degree of mandibular protrusion created by the MAS affects the dimensions of the upper airway, the degree of the vertical opening exerts no significant dimensional effect in the sagittal plane in fully dentate apneic patients. The mandibular protrusion effect is comparatively larger in the velopharyngeal region.

Novel porous oral patches for patients with mild obstructive sleep apnea and mouth breathing: a pilot study

OBJECTIVES

Habitual open-mouth breathing (OMB) during sleep can cause snoring and obstructive sleep apnea (OSA). This study used a porous oral patch (POP) to treat patients with mild OSA and OMB during sleep. The subjective and objective outcomes were evaluated.

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Patients with ≥5 events hourly but <15 hourly on the apnea-hypopnea index (AHI) were enrolled. All patients slept with their mouths closed by using the POP, which is a porous skin pad consisting of 3 layers: silicone sheet, polyurethane foam, and polyurethane film. Before treatment and during treatment, subjective outcomes were assessed using the Epworth Sleepiness Scale (ESS) and visual analog scale (VAS) of snoring. Objective outcomes were assessed using polysomnography and cephalometry.

RESULTS

Thirty patients were enrolled in this study. All patients slept with their mouths closed while using a POP. The ESS and VAS of snoring scores were 8.1 ± 1.5 and 7.5 ± 2.0 before the POP, respectively, in contrast to 5.2 ± 1.6 and 2.4 ± 1.4 while using a POP, respectively (P < .05). The median AHI score was significantly decreased by using a POP from 12.0 per hour before treatment to 7.8 per hour during treatment (P < .01). The snoring intensity and median snoring index were 49.1 ± 10.8 dB and 146.7 per hour before the POP, respectively, which decreased to 41.1 ± 7.8 dB and 40.0 per hour while using a POP, respectively (P < .01). Cephalometry revealed that the retropalatal space and retrolingual space were 7.4 ± 1.6 mm and 6.8 ± 2.5 mm before the POP, respectively, compared with 8.6 ± 1.2 mm and 10.2 ± 1.8 mm during treatment, respectively (P < .01).

CONCLUSION

The POP is a useful device to treat patients with mild OSA and habitual OMB.

Nasal involvement in obstructive sleep apnea syndrome

Numerous studies have reported an association between nasal obstruction and obstructive sleep apnea syndrome (OSAS), but the precise nature of this relationship remains to be clarified. This paper aimed to summarize data and theories on the role of the nose in the pathophysiology of sleep apnea as well as to discuss the benefits of surgical and medical nasal treatments. A number of pathophysiological mechanisms can potentially explain the role of nasal pathology in OSAS. These include the Starling resistor model, the unstable oral airway, the nasal ventilatory reflex, and the role of nitric oxide (NO). Pharmacological treatment presents some beneficial effects on the frequency of respiratory events and sleep architecture. Nonetheless, objective data assessing snoring and daytime sleepiness are still necessary. Nasal surgery can improve the quality of life and snoring in a select group of patients with mild OSAS and septal deviation but is not an effective treatment for OSA as such. Despite the conflicting results in the literature, it is important that patients who are not perfectly adapted to CPAP are evaluated in detail, in order to identify whether there are obstructive factors that could be surgically corrected.

Mandible behaviour interpretation during wakefulness, sleep and sleep-disordered breathing

The mandible movement (MM) signal provides information on mandible activity. It can be read visually to assess sleep-wake state and respiratory events. This study aimed to assess (1) the training of independent scorers to recognize the signal specificities; (2) intrascorer reproducibility and (3) interscorer variability. MM was collected in the mid-sagittal plane of the face of 40 patients. The typical MM was extracted and classified into seven distinct pattern classes: active wakefulness (AW), quiet wakefulness or quiet sleep (QW/S), sleep snoring (SS), sleep obstructive events (OAH), sleep mixed apnea (MA), respiratory related arousal (RERA) and sleep central events (CAH). Four scorers were trained; their diagnostic capacities were assessed on two reading sessions. The intra- and interscorer agreements were assessed using Cohen's κ. Intrascorer reproducibility for the two sessions ranged from 0.68 [95% confidence interval (CI): 0.59-0.77] to 0.88 (95% CI: 0.82-0.94), while the between-scorer agreement amounted to 0.68 (95% CI: 0.65-0.71) and 0.74 (95% CI: 0.72-0.77), respectively. The overall accuracy of the scorers was 75.2% (range: 72.4-80.7%). CAH MMs were the most difficult to discern (overall accuracy 65.6%). For the two sessions, the recognition rate of abnormal respiratory events (OAH, CAH, MA and RERA) was excellent: the interscorer mean agreement was 90.7% (Cohen's κ: 0.83; 95% CI: 0.79-0.88). The discrimination of OAH, CAH, MA characteristics was good, with an interscorer agreement of 80.8% (Cohen's κ: 0.65; 95% CI: 0.62-0.68). Visual analysis of isolated MMs can successfully diagnose sleep-wake state, normal and abnormal respiration and recognize the presence of respiratory effort.

A randomised controlled trial on the effect of mask choice on residual respiratory events with continuous positive airway pressure treatment

INTRODUCTION

It has been found that mask style can affect the amount of continuous positive airway pressure (CPAP) required to reduce an apnoea/hyponoea index (AHI) to < 5/h on a titration study. However, it was not previously known whether switching from one CPAP mask style to another post titration could affect the residual AHI with CPAP. The purpose of this study was to investigate the differences in residual AHI with CPAP treatment between oronasal and nasal masks.

METHODS

Twenty-one subjects (age mean (M)=62.9, body mass index (BMI) M=29.6 kg/m2) were randomised (14 subjects completed the protocol) to undergo an in-laboratory CPAP titration with either a nasal mask or an oronasal mask. Subjects were then assigned this mask for 3weeks of at-home CPAP use with the optimal treatment pressure determined on the laboratory study (CPAP M=8.4 cm of H2O). At the end of this 3-week period, data were collected from the CPAP machine and the subject was given the other mask to use with the same CPAP settings for the next 3weeks at home (if the nasal mask was given initially, the oronasal one was given later and vice versa). On completion of the second 3-week period, data on residual AHI were again collected and compared with the first 3-week period on CPAP.

RESULTS

A Wilcoxon Signed-Rank Test (two-tailed) revealed that residual AHI with CPAP treatment was significantly higher with the oronasal compared with the nasal mask (z = -3.296, p<0.001). All 14 subjects had a higher residual AHI with the oronasal versus nasal mask, and 50% of the subjects had a residual AHI >10/h in the oronasal mask condition, even though all of these subjects were titrated to an AHI of < 5/h in the laboratory.

CONCLUSION

A higher residual AHI was seen in all patients with the use of an oronasal mask compared with a nasal mask. Switching to an oronasal mask post titration results in an increase in residual AHI with CPAP treatment, and pressure adjustment may be warranted.

The relationship between structural/MHC changes in upper airway palatopharyngeal muscle morphology and obstructive sleep apnea/hypopnea syndrome

The aim of this study is to explore the relationship between structural/MHC changes in upper airway palatopharyngeal muscle morphology and obstructive sleep apnea/hypopnea syndrome. Palatopharyngeal muscle specimens were taken from 51 patients with obstructive sleep apnea hypopnea syndrome (OSAHS) who underwent uvulopalatopharyngoplasty (UPPP) resection. Patients were divided into light, medium and severe in terms of the severity of their OSAHS. There were 17 patients in each severity group. Palatopharyngeal muscle specimens were also taken from 17 patients suffering from chronic tonsillitis for comparison as the control group. All specimens were stained using Masson and observed for structural changes, especially in muscle fiber morphology, density and arrangement, as well as intermuscular connective tissues, under light microscopy. All specimens were also analyzed for MHC-I, MHC-IIa and MHC-IIb phenotype and protein expression differences using mRNA quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence staining. The results from each group were then statistically analyzed using semi-quantitative analysis. Light microscopy with Masson staining revealed that in the control group, the muscle fibers are closely connected and arranged neatly. In specimens from patients suffering from OSAHS, the palatopharyngeal muscle fibers are larger with obvious hypertrophy and there was an increase in elastic fibers. The mucosal lamina propria was thickened, and the density of muscle fibers was reduced. Muscle fibers are not neatly arranged and degeneration was observed. The amount of muscular pathology and fibrosis corresponds to the severity of disease in the patients. In patients with severe OSAHS, the proportion of collagen to muscle fibers was increased significantly. Immunofluorescence results reveal that there were significantly more fast muscle fibers and less slow muscle fibers in the study group than the control group. mRNA quantitative reverse transcription polymerase chain reaction (RT-PCR) revealed similar results, i.e., the proportion of MHC-II palatopharyngeal muscle fibers is higher in the study group than the control group, and increases with the severity of OSAHS. Pathological change occurs in both the collagen and muscle of OSAHS patients and corresponds to the degree of severity of OSAHS. Pathological change in palatopharyngeal muscle tissues is therefore, likely to be related to the occurrence and development of OSAHS. The increase in the proportion of the MHC-1I type fibers in OSAHS patients is likely to have an effect on the amount of airway support conferred by the muscle. This is likely the reason behind the lack of clinical improvement in some patients with severe OSAHS despite surgical treatment.

Death by a thousand cuts in Alzheimer's disease: hypoxia--the prodrome

A wide range of clinical consequences may be associated with obstructive sleep apnea (OSA) including systemic hypertension, cardiovascular disease, pulmonary hypertension, congestive heart failure, cerebrovascular disease, glucose intolerance, impotence, gastroesophageal reflux, and obesity, to name a few. Despite this, 82 % of men and 93 % of women with OSA remain undiagnosed. OSA affects many body systems, and induces major alterations in metabolic, autonomic, and cerebral functions. Typically, OSA is characterized by recurrent chronic intermittent hypoxia (CIH), hypercapnia, hypoventilation, sleep fragmentation, peripheral and central inflammation, cerebral hypoperfusion, and cerebral glucose hypometabolism. Upregulation of oxidative stress in OSA plays an important pathogenic role in the milieu of hypoxia-induced cerebral and cardiovascular dysfunctions. Strong evidence underscores that cerebral amyloidogenesis and tau phosphorylation--two cardinal features of Alzheimer's disease (AD), are triggered by hypoxia. Mice subjected to hypoxic conditions unambiguously demonstrated upregulation in cerebral amyloid plaque formation and tau phosphorylation, as well as memory deficit. Hypoxia triggers neuronal degeneration and axonal dysfunction in both cortex and brainstem. Consequently, neurocognitive impairment in apneic/hypoxic patients is attributable to a complex interplay between CIH and stimulation of several pathological trajectories. The framework presented here helps delineate the emergence and progression of cognitive decline, and may yield insight into AD neuropathogenesis. The global impact of CIH should provide a strong rationale for treating OSA and snoring clinically, in order to ameliorate neurocognitive impairment in aged/AD patients.

New protocol to prevent TMJ reankylosis and potentially life threatening complications in triad patients

The management of patients with the triad of temporomandibular joint (TMJ) ankylosis, micrognathia and obstructive sleep apnea syndrome is challenging for the oral and maxillofacial surgeon because it involves achieving the desired oral opening, correction of micrognathia, and correction of the obstructed airway. Seven of the authors' triad patients, in whom only the release of ankylosis was performed, developed bradycardia and respiratory distress during postoperative jaw physiotherapy, leading to their non-compliance for active jaw physiotherapy and subsequent reankylosis. This paper suggests a new surgical protocol for the management of patients with the triad, to achieve correction of the obstructed airway, relief of the respiratory distress symptoms, correction of micrognathia and restricted mouth opening. It also provides a logical reason for the occurrence of bradycardia following ankylosis release and its potential role in TMJ reankylosis. It emphasizes that the occurrence of bradycardia in triad patients during jaw exercises is dictated by the severity of their apnea-hypopnea index and the degree of narrowing of their posterior airway space. The recognition and prevention of this by the new protocol is discussed in 7 patients.

The efficacy of three different mask styles on a PAP titration night

BACKGROUND

This study compared the efficacy of three different masks, nasal pillows, nasal masks and full face (oronasal) masks, during a single night of titration with continuous positive airway pressure (CPAP).

METHODS

Fifty five subjects that included men (n=33) and women (n=22) were randomly assigned to one of three masks and underwent a routine titration with incremental CPAP applied through the different masks.

RESULTS

CPAP applied through the nasal pillows and nasal mask was equally effective in treating mild, moderate, and severe sleep apnea. However, CPAP applied through the oronasal mask required a significantly higher pressure compared to nasal masks to treat moderately severe (2.8 cm of H(2)O ± 2.1 SD) and severe (6.0 cm of H(2)O ± 3.2 SD) obstructive sleep apnea.

CONCLUSION

CPAP applied with either nasal mask was effective in treating mild, moderate, and severe sleep apnea. The oronasal mask required significantly higher pressures in subjects with moderate to severe disease. Therefore, when changing from a nasal to an oronasal mask, a repeat titration is required to ensure effective treatment of sleep apnea, especially in patients with moderate to severe disease.

Equivalence of nasal and oronasal masks during initial CPAP titration for obstructive sleep apnea syndrome

STUDY OBJECTIVE

Continuous positive airway pressure (CPAP) titration studies are commonly performed using a nasal mask but some patients may prefer a full-face or oronasal mask. There is little evidence regarding the equivalence of different mask interfaces used to initiate treatment. We hypothesized that oronasal breathing when using an oronasal mask increases upper airway collapsibility and that a higher pressure may be required to maintain airway patency. We also assessed patient preferences for the 2 mask interfaces.

DESIGN

Prospective, randomized, cross-over design with 2 consecutive CPAP titration nights.

SETTING

Accredited laboratory in a university hospital.

PATIENTS OR PARTICIPANTS

Twenty-four treatment-naive subjects with obstructive sleep apnea syndrome and respiratory disturbance index of greater than 15 events per hour.

INTERVENTIONS

CPAP titration was performed using an auto-titrating machine with randomization to a nasal or oronasal mask, followed by a second titration night using the alternate mask style.

MEASUREMENTS AND RESULTS

There was no significant difference in the mean pressures determined between nasal and oronasal masks, although 43% of subjects had nasal-to-oronasal mask-pressure differences of 2 cm H(2)O or more. Residual respiratory events, arousals, and measured leak were all greater with the oronasal mask. Seventy-nine percent of subjects preferred the nasal mask.

CONCLUSIONS

Patients with obstructive sleep apnea syndrome can generally switch between nasal and oronasal masks without changing machine pressure, although there are individual differences that may be clinically significant. Measured leak is greater with the oronasal mask. Most patients with obstructive sleep apnea syndrome prefer a nasal mask as the interface for initiation of CPAP.

CLINICAL TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN: ACTRN12611000243910. URL: http://www.ANZCTR.org.au/ACTRN12611000243910.aspx

Effects of head-neck extension on abnormality of laryngeal mask airway function resulting from opening the mouth

PURPOSE

This study investigated the effects of head-neck extension on abnormalities of laryngeal mask airway (LMA) function resulting from opening the mouth.

PATIENTS AND METHODS

A single, experienced LMA user inserted the LMA in 15 patients scheduled for elective oral surgery. Oropharyngeal leak pressure and intracuff pressure were sequentially documented in 5 mouth conditions in order (0 minutes, mouth closed plus 0° extension; 3 minutes, mouth open plus 0° extension; 6 minutes, mouth open plus 15° extension; 9 minutes, mouth open plus 30° extension; and 12 minutes, mouth open plus 45° extension).

RESULTS

Oropharyngeal leak pressures with the mouth open plus 0° extension (30.7 ± 5.6 cm H(2)O, P < .001), mouth open plus 15° extension (29.1 ± 6.8 cm H(2)O, P < .001), and mouth open plus 30° extension (25.7 ± 6.1 cm H(2)O, P < .001) were significantly higher than with the mouth closed plus 0° extension (19.7 ± 2.8 cm H(2)O). Compared with the position with the mouth closed plus 0° extension (60.0 ± 0 cm H(2)O), intracuff pressures were also higher with the mouth open plus 0° extension (84.5 ± 14.1 cm H(2)O, P < .001), mouth open plus 15° extension (77.4 ± 11.0 cm H(2)O, P < .001), and mouth open plus 30° extension (73.6 ± 9.6 cm H(2)O, P < .001). Both measurement values returned to control levels when the position with the mouth open plus 45° extension was assumed (oropharyngeal leak pressure, 64.5 ± 6.5 cm H(2)O [P = .212]; intracuff pressure, 20.2 ± 4.9 cm H(2)O [P = .969]).

CONCLUSIONS

In procedures requiring the patient to have an open mouth under general anesthesia using LMA, 45° head-neck extension achieves acceptable airway conditions.

Optimal degree of mouth opening for laryngeal mask airway function during oral surgery

PURPOSE

This study was performed to determine the optimal degree of mouth opening in anesthetized patients requiring laryngeal mask airway (LMA) during oral surgery.

PATIENTS AND METHODS

A single, experienced LMA user inserted the LMA in 15 patients who were scheduled for elective oral surgery. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were sequentially documented in 5 mouth conditions-opening of 1.4 (neutral position), 2, 3, 4, and 5 cm-and any resulting ventilatory difficulties were recorded.

RESULTS

Oropharyngeal leak pressure with the mouth open 4 cm (21.8 ± 3.2 cm H(2)O, P = .025) and 5 cm (27.3 ± 7.2 cm H(2)O, P < .001) was significantly higher than in the neutral position (18.1 ± 1.5 cm H(2)O), as was intracuff pressure (neutral position, 60.0 ± 0 cm H(2)O; 4 cm, 72.6 ± 5.1 cm H(2)O [P < .001]; and 5 cm, 86.9 ± 14.4 cm H(2)O [P < .001]). LMA position, observed by fiberoptic bronchoscopy, was unchanged by mouth opening, being similar in the 5 mouth conditions (P = .999). In addition, ventilation difficulties (abnormal capnograph curves or inadequate tidal volume) occurred in 2 of 15 patients (13%) and 7 of 15 patients (53%) (P < .001) with the mouth opening of 4 and 5 cm, respectively.

CONCLUSIONS

This study showed that a mouth opening over 4 cm led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution, because gastric insufflation, sore throat, and ventilation difficulties may occur. A mouth opening of 3 cm achieves acceptable airway conditions for anesthetized patients requiring LMA.

The influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position with the laryngeal mask airway

PURPOSE

The aim of this study was to investigate the influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position of the laryngeal mask airway (LMA).

PATIENTS AND METHODS

Fifteen patients who were scheduled for elective oral surgery were recruited into this study. A single, experienced LMA user inserted the LMA according to the manufacturer's recommended technique. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were documented under 3 mouth conditions: neutral position (1.4-cm distance between upper and lower incisors), mouth open (5- to 6-cm distance between upper and lower incisors), and return to the neutral position. Any ventilation difficulties under the 3 mouth conditions were recorded.

RESULTS

Oropharyngeal leak pressure with the mouth open was higher than in the neutral position (P < .001). Compared with the neutral position, intracuff pressure was also higher with the mouth open (P < .001). Both measurement values returned to control levels when the neutral position was once again assumed. The LMA position observed by fiberoptic bronchoscopy was unchanged by mouth opening and was similar in the 3 mouth conditions (P = .998). Although ventilatory difficulties occurred after mouth opening in 8 of 15 patients (P < .001), it did not occur when the neutral position was reassumed.

CONCLUSIONS

This study showed that mouth opening led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution because gastric insufflation, sore throat, and ventilation difficulties may occur.

Functional treatment of snoring based on the tongue-repositioning manoeuvre

Orofacial biofunction comprises muscular and physical effects, which may contribute to stabilization of the oropharyngeal airway. The tongue-repositioning manoeuvre (TRM) provides physical stabilization of the tongue and the soft palate together with, as a prerequisite, a nasal breathing mode. The aim of the present study was to evaluate the influence of a TRM treatment concept on primary snoring. The TRM was used to achieve a closed biofunctional rest position of the orofacial system and to re-educate the nasal breathing pattern. Pressure indicating oral shields were used for home exercises as a biofeedback instrument and to support nocturnal mouth closure. Treatment was undertaken on 125 consecutive primary snorers [101 males, mean age 52.4 years, range 34-75, mean body mass index (BMI) 28.1, range 18.9-38.5, and 24 females, mean age 55.2 years, range 36-70, mean BMI 26.8, range 22.7-31.9]. Bed partner ranking was performed, and snoring was judged using a 10-cm visual analogue scale (VAS). The VAS score was 8.4 (range 6-10) before treatment and decreased to 4.1 (range 0-10) after treatment [mean observation time 4.6 months (1-10)]. Analysis of variance showed a significant influence of treatment in subjects with a normal body weight (BMI 18.5-25). The data provide evidence that dynamic stabilization of the orofacial system with the TRM in conjunction with nocturnal wear of an oral shield is beneficial for reducing the symptoms in primary snorers with a normal BMI.

Daytime sleepiness relates to snoring independent of the apnea-hypopnea index in women from the general population

OBJECTIVES

The aim was to investigate the significance of snoring and sleep apnea on daytime symptoms in a population-based sample of women.

METHOD

From the general population, 400 women aged 20 to 70 years were randomly selected, with oversampling of habitually snoring women. The women were investigated using full-night polysomnography and a questionnaire. The apnea-hypopnea index (AHI) was calculated, and women who acknowledged snoring loudly and disturbingly often or very often were considered habitual snorers.

RESULTS

Habitual snoring was independently related to excessive daytime sleepiness (odds ratio [OR], 2.28; 95% confidence interval [CI], 1.31 to 3.99), to falling asleep involuntarily during the day (OR, 2.11; 95% CI, 1.06 to 4.21), to waking up unrefreshed (OR, 2.14; 95% CI, 1.30 to 3.52), to daytime fatigue (OR, 2.77; 95% CI, 1.54 to 4.99), and to a dry mouth on awakening (OR, 2.00; 95% CI, 1.22 to 3.27) after adjustment for AHI, age, body mass index (BMI), smoking, total sleep time, percentage of slow-wave sleep, and percentage of rapid eye movement (REM) sleep. An AHI > or = 15/h was only related to a dry mouth on awakening after adjustment for snoring, age, BMI, smoking, total sleep time, percentage of slow-wave sleep, and percentage of REM sleep (OR, 2.24; 95% CI, 1.14 to 4.40). An AHI of 5 to 15/h was not related to any daytime symptom.

CONCLUSIONS

Excessive daytime sleepiness and daytime fatigue are related to habitual snoring independent of the apnea-hypopnea frequency, age, obesity, smoking, and sleep parameters in a population-based sample of women, but not to the AHI. This indicates that snoring is an independent cause of excess daytime sleepiness and not merely a proxy for sleep apnea.

Objective measurement of nasal airway dimensions and resistance using acoustic rhinometry and rhinomanometry in habitual snorers compared with non-snorers

Snorers represent a heterogeneous group that requires adequate assessment before recommending surgical treatment. Most studies of the pathophysiology of snoring and obstructive sleep apnea have emphasized anatomical abnormalities in the oropharyngeal and hypopharyngeal airways. It is still unclear if nasal airway restriction plays an important role in sleep-disordered breathing and there is no general consensus if treatment of nasal pathology should be included in the management of patients with snoring or sleep apnea. The aim of this study was to compare nasal dimensions and airflow resistance of habitual snorers with non-snoring individuals by means of acoustic rhinometry and rhinomanometry. Sixty individuals were enrolled in this analytical cross-sectional study. They were divided in two groups: group A (case) consisted of 30 patients with a main complaint of chronic snoring referred to ear, nose, and throat (ENT) clinic of Hazrat-e-Rasoul University Hospital, Tehran, Iran. Group B (control) consisted of 30 individuals without any complaint of snoring. The subjects were assessed objectively with acoustic rhinometry and rhinomanometry. Nasal dimensions and airflow resistance were recorded for all individuals. The most common site of minimum cross-sectional area (MCA) was at the left concha-notch in both snoring and non-snoring individuals. Significant reduction of cross-sectional area of both isthmus and concha notches was seen in habitual snorers (P < 0.05). The mean total airflow resistances in both pressures of 75 and 150 Pa was higher in habitual snorers. Whereas, these differences were not statistically significant (P > 0.05). The results of our study illustrate that acoustic rhinometry, rhinomanometry may be helpful methods for quantitative assessments of nasal airway respiratory function, and configuration in snorers; especially to evaluate site of MCA, decreased nasal cross-sectional area and increased nasal airflow resistance in habitual snorers which may lead to OSA.

Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

The velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P < 0.0001). Coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone dilated the VP and made Pcrit more negative (P < 0.0001), but only in the caudal VP. In the rat, the caudal VP is more collapsible than the rostral VP, and either coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone makes this region more difficult to close. Thus, tongue muscle contraction protects the caudal VP, which appears to be a particularly vulnerable segment of the nasopharyngeal airway. With suitable modification, the methods described here, including tongue muscle stimulation at different pharyngeal pressures, may be appropriate for experiments in human subjects.

Activation patterns of the tongue muscles with selective stimulation of the hypoglossal nerve

The upper airways were imaged in anesthetized beagles to investigate the effect of selective stimulation of the hypoglossal nerve (HG) with a multi-contact peripheral nerve electrode. A fiberscope lead (diam. 5 mm) was inserted through the proximal end of the tracheostomy and fixed at 1 cm behind the uvula to image the oro- and nasopharynx while the head was fixed at either 30 degrees or 60 degrees from the horizontal with the mouth open or closed. Images of the tongue were recorded with a camera in open mouth positions. These images show that stimulations delivered through the electrode contacts placed around the HG nerve trunk can generate several different activation patterns of the tongue muscles. Some of these patterns translate into a substantial increase in the pharyngeal opening size while some others decrease it. The activation patterns vary as a function of the head position and the lower jaw. These results suggest that selective stimulation of the HG nerve can be a useful technique to maximize the effects of HG nerve stimulation in removing the obstructions in sleep apnea patients.

Snoring noise pollution—the need for objective quantification of annoyance, regulatory guidelines and mandatory therapy for snoring

Habitual snoring without episodes of apnea or hypoventilation and without respiratory related arousals is considered to be annoying and without any need for treatment. However, studies seem to suggest an enormous psychosocial impact of annoyance for the bed partner. Apart from subjective questionnaires there still exists no generally accepted mode of measurement that can describe snoring objectively. We therefore adapted methods developed for environmental medicine and established a new snore score using psycho-acoustic parameters. For quantification of snoring noise we conducted nocturnal measurements in 19 habitual snorers. Free-field snore sounds were acquired with two low-cost non-contact microphones and transferred to a PC (sampling frequency 11 kHz). The data were recorded, analysed and stored automatically using a MATLAB script. Following the analysis of sound characteristics and levels, the score was computed from relevant parameters containing the rating level (L(R)), maximum level, two percentile levels for frequent maxima (L(5)S; L(1)) and snoring time. The determined values substantially exceeded the prescribed limits defined by WHO noise guidelines, and mainly affected the equivalent continuous sound exposure level, rating level and the immission standard values of brief noise peaks, whose maximum was exceeded by up to 32 dB(A). The Berlin snore score illustrated the objective acoustic annoyance on a scale from 0 to 100. It allows inter-individual comparison and objectifies the need for therapy. The clinical applicability of evaluating the reduction of snoring after surgical therapy is discussed exemplarily. The presented measuring method was found to be suitable for quantifying snoring noise and can be easily integrated into existing polysomnographic applications. In the case of habitual snoring with objective evidence of psychosocially disturbing acoustic annoyance, health fund providers should assume the costs of mandatory medical therapy.

Pharyngeal critical pressure in children with mild sleep-disordered breathing

There is evidence that narrowing or collapse of the pharynx can contribute to obstructive sleep-disordered breathing (SDB) in adults and children. However, studies in children have focused on those with relatively severe SDB who generally were recruited from sleep clinics. It is unclear whether children with mild SDB who primarily have hypopneas, and not frank apnea, also have more collapsible airways. We estimated airway collapsibility in 10 control subjects (9.4 ± 0.5 yr old; 1.9 ± 0.2 hypopneas/h) and 7 children with mild SDB (10.6 ± 0.5 yr old; 11.5 ± 0.1 hypopneas/h) during stable, non-rapid eye movement sleep. None of the subjects had clinically significant enlargement of the tonsils or adenoids, nor had any undergone previous tonsillectomy or adenoidectomy. Airway collapsibility was measured by brief (2-breath duration) and sudden reductions in pharyngeal pressure by connecting the breathing mask to a negative pressure source. Negative pressure applications ranging from −1 to −20 cmH2O were randomly applied in each subject while respiratory airflow and mask pressure were measured. Flow-pressure curves were constructed for each subject, and the x-intercept gave the pressure at zero flow, the so-called critical pressure of the upper airway (Pcrit). Pcrit was significantly higher in children with SDB than in controls (−10.8 ± 2.8 vs. −15.7 ± 1.2 cmH2O; P < 0.05). There were no significant differences in the slopes of the pressure-flow relations or in baseline airflow resistance. These data support the concept that intrinsic pharyngeal collapsibility contributes to mild SDB in children.

Combined open rhinoplasty with spreader grafts and laser-assisted uvuloplasty for sleep-disordered breathing: long-term subjective outcomes

PURPOSE

To subjectively assess the long-term outcomes of combined functional open rhinoplasty with spreader grafts and laser-assisted uvuloplasty (LAUP) for polysomnogram (PSG)-confirmed sleep-disordered breathing (SDB).

METHODS

Postoperative Epworth Sleepiness Scale (ESS) questionnaires were given to 30 patients and compared with preoperative ESS. Patients were also asked questions concerning postoperative improvement in upper airway breathing, nasal appearance, and snoring. Statistical analysis used 2-tailed parametric and nonparametric tests.

RESULTS

Thirty patients (average age 55 years) with an average (+/- standard deviation) preoperative apnea-hypopnea index (AHI) of 37 +/- 27 and mean follow-up times of 21 months were evaluated. A statistically significant 50% (P < .001) postoperative decrease in average ESS was observed. Patients with severe (AHI > 30) and very severe obstructive sleep apnea (OSA) (AHI > 60) also had statistically significant (61% and 66%, respectively, P < .001) postoperative decreases in average ESS. In all patients, subjective upper airway breathing was statistically improved (P < .008), graded as significantly in 47% and moderately in 33% of patients. According to the patient's bed partner, snoring was improved and/or decreased in 76% of patients (P = .008). All patients were satisfied with the postoperative cosmetic appearance of their nose (P < .0001). Finally, 90% of patients stated that they would have the procedure again (P = .009) and 90% stated that they would recommend the procedure to a friend or relative with the same condition (P = .009).

CONCLUSION

Subjective assessment at long-term follow-up for combined open rhinoplasty with spreader grafts and LAUP for PSG-confirmed SDB produced a statistically significant decrease in excessive daytime sleepiness, even in patients with very high AHI, with high patient satisfaction.

Effect of cervical headgear wear on dynamic measurement of head position

The aim of this study was to identify the effect of cervical headgear (CHG) wear on dynamic measurement of head posture during walking. Six male and 10 female patients (mean age, 11.9 +/- 1.9 years) who were receiving CHG therapy for correction of a Class II molar relationship as part of their orthodontic treatment were included in this study. Dynamic head posture measurements were recorded using an inclinometer and data logger apparatus during a walking session of 5 minutes. This procedure was repeated before (T1) and after (T2) insertion of CHG. The T1 and T2 measurements were repeated twice at 30-minute intervals. The mean dynamic head posture was calculated for each subject using the collected data. The means of these measurements were statistically compared using a paired t-test. Of the 16 subjects, 14 showed a cranial flexion with CHG wear in relation to T1 (1.4 to 8.9 degrees). The other two subjects showed a cranial extension of -1.6 and -3.8 degrees. The mean values at T1, T2 and T1-T2 were 1.4, -1.8, and 3.1 degrees, respectively, which indicated a mean cranial flexion at T2 in relation to T1. According to the paired sample t-test, there were statistically significant differences between the two measurements of dynamic head posture recorded before and after CHG insertion (P < 0.001). CHG wear causes a significant cranial flexion which may be responsible for its effects on the mandible.

Mouth-opening increases upper-airway collapsibility without changing resistance during midazolam sedation

Sedative doses of anesthetic agents affect upper-airway function. Oral-maxillofacial surgery is frequently performed on sedated patients whose mouths must be as open as possible if the procedures are to be accomplished successfully. We examined upper-airway pressure-flow relationships in closed mouths, mouths opened moderately, and mouths opened maximally to test the hypothesis that mouth-opening compromises upper-airway patency during midazolam sedation. From these relationships, upper-airway critical pressure (Pcrit) and upstream resistance (Rua) were derived. Maximal mouth-opening increased Pcrit to -3.6 +/- 2.9 cm H2O compared with -8.7 +/- 2.8 (p = 0.002) for closed mouths and -7.2 +/- 4.1 (p = 0.038) for mouths opened moderately. In contrast, Rua was similar in all three conditions (18.4 +/- 6.6 vs. 17.7 +/- 7.6 vs. 21.5 +/- 11.6 cm H2O/L/sec). Moreover, maximum mouth-opening produced an inspiratory airflow limitation at atmosphere that was eliminated when nasal pressure was adjusted to 4.3 +/- 2.7 cm H2O. We conclude that maximal mouth-opening increases upper-airway collapsibility, which contributes to upper-airway obstruction at atmosphere during midazolam sedation.

Effects of gender on upper airway collapsibility and severity of obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) is far more common in males than females. The discrepancy between the lower prevalence of OSA, the greater frequency of obesity and the smaller airway size in women compared to men suggests that a gender difference underlies this condition. We hypothesized that due to differences in tissue linkage women have more stable and less mobile upper airway structures than men, providing protection against severe forms of OSA.

METHODS

Seventy-one consecutive patients with OSA, defined as having apnea-hypopnea index > or =5 events per hour, were enrolled into the study. The median (range) apnea-hypopnea index was 20 (5-132) events/h. In addition, measurements of upper airway dimensions were made, using an acoustic reflectance method, while the lower jaw was in the resting position and during retrusive posture. Measurements of upper airway dimensions were used during wakefulness to examine whether changes in pharyngeal dimensions, resulting from retrusive movement of the mandible commonly occurring during sleep, would explain the gender differences in the characteristics of OSA.

RESULTS

OSA was much more positional and severe in men than women as indicated by the higher apnea-hypopnea index in supine position compared with sleeping on the side (difference between supine and side apnea-hypopnea index: 43.7+/-5.2 (SEM) events/h in men versus 10.7+/-7.6 events/h in women, P=0.0015). The position dependency of OSA was most pronounced in those patients who demonstrated the largest decrease in pharyngeal cross-sectional area with retrusive movement of the mandible. There was no significant change in pharyngeal cross-sectional area as a result of retrusive movement of the mandible in women.

CONCLUSIONS

Men tend to have a larger but more collapsible airway during mandibular movement than women and this, in part, may play a role in the positional dependency and severity of OSA in men.

Assessment of upper airway stabilizing forces with the use of phrenic nerve stimulation in conscious humans

Phrenic nerve stimulation (PNS) applied at end-expiration allows the investigation of passive upper airway (UA) dynamic during wakefulness. Assuming that phasic UA dilating/stabilizing forces should modify the UA properties when twitches are applied during inspiration, we compared the UA dynamic responses to expiratory and inspiratory twitches (2 s and 200 ms after expiratory and inspiratory onset, respectively) in nine men (mean age 28 yr). This procedure was repeated with a 2-cm mouth opening provided with a closed mouthpiece. The percentage of flow-limited (FL) twitches was significantly higher when PNS was realized during expiration than during inspiration. Maximal inspiratory flow (Vi(max)) of FL twitches was significantly higher for inspiratory twitches (1,383 +/- 42 and 1,185 +/- 40 ml/s). With mouth aperture, Vi(max) decreased with an increase in the corresponding pharyngeal resistance values, and the percentage of twitch with a FL regimen increased but only for inspiratory twitches. We conclude that 1) UA dynamics are significantly influenced by the inspiratory/expiratory timing at which PNS is applied, 2) the improvement in UA dynamic properties observed from expiratory to inspiratory PNS characterizes the overall inspiratory stabilizing effects, and 3) mouth aperture alters the stability of UA structures during inspiration.

Impact of impaired nasal breathing on sleep-disordered breathing

OBJECTIVE

The role of the nose and its importance in the development and severity of sleep-disordered breathing (SDB) is still a matter of discussion. In the first part of this study, often-controversial data and theories about the nose are reviewed concerning its influence on the pathophysiology of SDB and to interpret certain clinical findings connected with impaired nasal breathing. In the second part, the effectiveness of some nonsurgical and surgical therapies is evaluated.

METHOD

A worldwide literature research (Medline) was the basis for this review.

RESULTS

The study of the literature on nasal resistance and clinical findings about the effects of incomplete or complete nasal blockage, particularly in comparison of healthy persons and persons with SDB, allows the assumption of the existence of two different groups of responders: a larger group where the importance of the nose for SDB is negligible and a smaller group where the influence of the nose on SDB is crucial. The same seems to hold true for the responses to nonsurgical and surgical treatments with only a few surgical results available in the literature. While the success rate of nasal surgery for patients with obstructive sleep apnea, for instance, seems to be less than 20%, the normalization of nasal resistance often leads to a positive impact on the well-being and the sleep quality of these patients. However, because criteria to identify responders are lacking, the prediction of success of any treatment for the individual with SDB is not possible.

Evidence-based medicine in sleep apnea surgery

Since the first description of sleep apnea as a clinical entity, the understanding of it within the medical community has increased significantly. Much research has explored the causes, assessment, and treatment of this disease. This research has resulted in a variety of tools for assessment and approaches to treatment. As research progresses, new data have shed light on the strengths of traditional approaches and their limitations. This article gives background for current approaches and charts a potential future course for sleep apnea assessment and treatment.

The role of oral appliances in treating obstructive sleep apnea

BACKGROUND

Sleep-related breathing disorders are common and often are associated with vascular complications such as arterial hypertension, coronary heart disease and stroke. The most widely studied form of these disorders is obstructive sleep apnea. Patients usually are diagnosed with obstructive sleep apnea years after the onset of symptoms, which generally are nonspecific and include excessive daytime sleepiness, chronic fatigue and habitual snoring. The risk factors for sleep apnea are obesity, advancing age, male sex and maxillofacial abnormalities. This review focuses on the diagnosis and treatment of obstructive sleep apnea and, specifically, on the utility of oral appliances in the management of this disorder.

METHODS

The review is based on a MEDLINE search for articles in English on this topic. The article discusses results of randomized studies and prospective case series.

CLINICAL IMPLICATIONS

Several treatment options are quite effective. Nasal continuous positive airway pressure, with an overall acceptance rate of 70 percent, is the most widely used treatment modality. Maxillofacial surgery, although effective, is reserved for patients who have not responded to the more conventional therapies. Newer methods include application of oral appliances. Oral appliances have been shown to alleviate the severity of respiratory disturbances during sleep by about 60 percent, with an overall acceptance rate of 75 percent. The long-term complications generally are minor and are related to occlusal changes and temporomandibular joint discomfort.

CONCLUSIONS

With the advent of oral appliances, dentists are increasingly involved in managing the care of patients with sleep-related breathing disorders. Further studies are needed to determine the long-term complications of this type of intervention for the treatment of sleep-related breathing disorders.

Effect of vertical dimension on efficacy of oral appliance therapy in obstructive sleep apnea

The aim of this study was to assess the effect of bite opening induced by a mandibular advancement splint (MAS) on efficacy and side effects in the treatment of obstructive sleep apnea. In a randomized crossover fashion, 23 adult patients received either MAS-1 (4 mm of interincisal opening) or MAS-2 (14 mm of interincisal opening) for 2 weeks, followed by the alternate treatment for 2 weeks, with an intervening 1-week washout. Complete response was defined as a resolution of symptoms and a reduction in apnea/hypopnea index (AHI) to less than 5 per hour. Partial response was defined as improved symptoms and a reduction in AHI of 50% or more, with the AHI remaining at a value of 5 or more per hour. Both MAS-1 and MAS-2 produced similar reductions in mean (+/- SEM) AHI from baseline: 21 +/- 2 versus 8 +/- 1/hour and 21 +/- 2 versus 10 +/- 2/hour, respectively (p < 0.001). Either complete response or partial response occurred in 74 and 61% of patients with MAS-1 and MAS-2, respectively. Subjective improvements were reported with both appliances by the majority of patients. Patients preferred MAS-1 (78 versus 22%, p = 0.007). This study suggests that the amount of bite opening induced by MAS does not have a significant impact on treatment efficacy but does have an impact on patient acceptance.

Effects of neck flexion and mouth opening on inspiratory flow dynamics in awake humans

Phrenic nerve stimulation (PNS) can assess airflow dynamics of the upper airway (UA) during wakefulness in man. Using PNS, we aimed to assess the impact of neck flexion and mouth opening in promoting UA unstability. Measurements were made during nasal breathing in seven healthy subjects (ages = 23-39 yr; one woman). Surface diaphragm electromyogram, esophageal pressure referenced to mask pressure, and flow were recorded during diaphragm twitches with neck in neutral position and mouth closed and then with neck flexion and/or mouth opening. Twitches always exhibited a flow-limited pattern. Flow-limiting driving pressure (Pd) and peak Pd were increased by neck flexion (P < 0.01) without significant change in the corresponding flows. UA resistances at these flow values were higher with the neck flexed (P < 0.05). Mouth opening alone did not exert any significant influence. We conclude that the position of the neck has a discernible impact on the flow behavior through the nonphasically active UA faced with a negative Pd.

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.

Closed-loop stimulation of hypoglossal nerve in a dog model of upper airway obstruction

Electrical stimulation of upper airway (UAW) muscles has been under investigation as a treatment method for obstructive sleep apnea (OSA). Particular attention has been given to the electrical activation of the genioglossal muscle, either directly or via the stimulation of the hypoglossal nerve (HG), since the genioglossus is the main tongue protrusor muscle. Regardless of the stimulation site or method, an implantable electrical stimulation device for OSA patients will require a reliable method for detection of obstructive breaths to apply the stimulation when needed. In this paper, we test the hypothesis that the activity of the HG nerve can be used as a feedback signal for closed-loop stimulation of the HG nerve in an animal model of UAW obstruction where a force is applied on the submental region to physically narrow the airways. As an advantage, the method uses a single electrode for both recording and stimulation of the HG nerve. Simple linear filtering techniques were found to be adequate for producing the trigger signal for the electrical stimulation from the HG recordings. Esophageal pressure, which was used to estimate the size of the UAW passage, returned to the preloading values during closed-loop stimulation of the HG nerve. The data demonstrate the feasibility of the closed-loop stimulation of the HG nerve using its activity as the feedback signal.

An Overview of Sleep Disordered Breathing for the Otolaryngologist

Sleep disordered breathing was first described in ancient times. It is the result of a three-way interaction between the sleep/wake state-specific mechanisms of respiratory control, the interfacing of these mechanisms during times of state change, and the physical properties of the head and neck. Sleep disordered breathing results in pathological daytime sleepiness and is associated with significant cardiovascular morbidity. This paper reviews the history of the field, the physiologic and structural factors that result in sleep disordered breathing, and the implications of these factors for therapy.