Examining the limits of cellular adaptation bursting mechanisms in biologically-based excitatory networks of the hippocampus.

Determining the biological details and mechanisms that are essential for the generation of population rhythms in the mammalian brain is a challenging problem. This problem cannot be addressed either by experimental or computational studies in isolation. Here we show that computational models that are carefully linked with experiment provide insight into this problem. Using the experimental context of a whole hippocampus preparation in vitro that spontaneously expresses theta frequency (3-12 Hz) population bursts in the CA1 region, we create excitatory network models to examine whether cellular adaptation bursting mechanisms could critically contribute to the generation of this rhythm. We use biologically-based cellular models of CA1 pyramidal cells and network sizes and connectivities that correspond to the experimental context. By expanding our mean field analyses to networks with heterogeneity and non all-to-all coupling, we allow closer correspondence with experiment, and use these analyses to greatly extend the range of parameter values that are explored. We find that our model excitatory networks can produce theta frequency population bursts in a robust fashion.Thus, even though our networks are limited by not including inhibition at present, our results indicate that cellular adaptation in pyramidal cells could be an important aspect for the occurrence of theta frequency population bursting in the hippocampus. These models serve as a starting framework for the inclusion of inhibitory cells and for the consideration of additional experimental features not captured in our present network models.

Modeling oscillatory dynamics in brain microcircuits as a way to help uncover neurological disease mechanisms: a proposal.

There is an undisputed need and requirement for theoretical and computational studies in Neuroscience today. Furthermore, it is clear that oscillatory dynamical output from brain networks is representative of various behavioural states, and it is becoming clear that one could consider these outputs as measures of normal and pathological brain states. Although mathematical modeling of oscillatory dynamics in the context of neurological disease exists, it is a highly challenging endeavour because of the many levels of organization in the nervous system. This challenge is coupled with the increasing knowledge of cellular specificity and network dysfunction that is associated with disease. Recently, whole hippocampus in vitro preparations from control animals have been shown to spontaneously express oscillatory activities. In addition, when using preparations derived from animal models of disease, these activities show particular alterations. These preparations present an opportunity to address challenges involved with using models to gain insight because of easier access to simultaneous cellular and network measurements, and pharmacological modulations. We propose that by developing and using models with direct links to experiment at multiple levels, which at least include cellular and microcircuit, a cycling can be set up and used to help us determine critical mechanisms underlying neurological disease. We illustrate our proposal using our previously developed inhibitory network models in the context of these whole hippocampus preparations and show the importance of having direct links at multiple levels.

Shift in sleep apnoea type in heart failure patients in the CANPAP trial.

In patients with heart failure (HF), the predominant type of sleep apnoea can change over time in association with alterations in circulation time. The aim of this study was to determine whether, in some patients with HF, a spontaneous shift from mainly central (>50% central events) to mainly obstructive (>50% obstructive events) sleep apnoea (CSA and OSA, respectively) over time coincides with improvement in left ventricular ejection fraction (LVEF). Therefore, sleep studies and LVEFs of HF patients with CSA from the control arm of the Canadian Continuous Positive Airway Pressure for Patients with Central Sleep Apnea and Heart Failure (CANPAP) trial were examined to determine whether some converted to mainly OSA and, if so, whether this was associated with an increase in LVEF. Of 98 patients with follow-up sleep studies and LVEFs, 18 converted spontaneously to predominantly OSA. Compared with those in the nonconversion group, those in the conversion group had a significantly greater increase in the LVEF (2.8% versus -0.07%) and a significantly greater fall in the lung-to-ear circulation time (-7.6 s versus 0.6 s). In patients with HF, spontaneous conversion from predominantly CSA to OSA is associated with an improvement in left ventricular systolic function. Future studies will be necessary to further examine this relationship.

Reduced recombination associated with the production of aneuploid sperm in an infertile man: a case report.

Studies using gene-linkage analysis have suggested that abnormal recombination during meiosis may lead to the production of aneuploid gametes; however, there is little direct evidence of a link between the two in human males. We analysed spermatocytes in the pachytene stage from a man with extremely high aneuploidy rates in his sperm. Testicular tissue specimens of the infertile man and two vasectomy reversals were processed with immuofluorescent techniques to visualize synaptonemal complex and recombination foci and fluorescent in situ hybridization on spermatocytes and sperm with probes for chromosomes 13, 21, 18, X and Y. We observed no recombination between sex chromosomes in the infertile man, while in two controls, we observed recombination rates of 79.3 and 81.0% between the sex chromosomes. This was associated with a total sex aneuploidy rate of 41.61% in testicular sperm of the infertile man (0.44 and 0.62% in two controls). Recombination on chromosome 21 was reduced in the infertile man, with 10.62% of spermatocytes showing no recombination (0 and 1.67% in two controls), as well as chromosome 13, with 53.98% having < or =1 recombination foci (22.05 and 21.67% in two controls). This was associated with increased aneuploidy for those chromosomes. Chromosome 18 aneuploidy was slightly increased, although there was no apparent decrease in recombination. These results provide the first evidence of both recombination and non-disjunction abnormalities in the same individual. This is also the only reported case of an infertile man who shows no recombination between the sex chromosomes, despite the formation of the sex body.

Interinstitutional study to compare the effectiveness of a radiology-anatomy module of instruction.

RATIONALE AND OBJECTIVES: The purpose of this study was to validate the effectiveness of a proven radiology-anatomy instructional module during I st-year gross anatomy courses at Emory University College of Medicine and the University of Iowa College of Medicine. MATERIALS AND METHODS: This prospective study involved 108 Emory students and 177 Iowa students. The instructional content was the same at both institutions. Each student was randomly assigned into one of three groups at each institution, and each group received a unique, randomized, five-item pretest. All students were posttested as part of their gross anatomy laboratory examination, and the posttests consisted of all 15 items used in the three five-item pretests. RESULTS: No statistically significant pretest effects were demonstrated by t tests. Posttest performances across items ranged from 73% to 96% correct for Emory students and 67% to 98% for Iowa students. Performance levels on the posttests were significantly higher than on pretests, and few significant differences were found in the performance of the two populations. CONCLUSION: The radiology-anatomy instructional module integrated into the gross anatomy courses for 1st-year Emory University and University of Iowa students was not instructor or institution dependent.

Treatment, airway and compliance effects of a titratable oral appliance.

STUDY OBJECTIVES: To measure the effects of a titratable anterior mandibular repositioner on airway size and Obstructive Sleep Apnea (OSA) and to evaluate its compliance. DESIGN: Before and after insertion sleep studies were obtained in a total of 38 OSA patients of varying severity from three different sites. Covert compliance was measured by means of a newly-developed, miniaturized, temperature-sensitive, imbedded monitor. Validity testing was completed in six adult volunteers who wore monitors imbedded into small acrylic appliances. MEASUREMENTS AND RESULTS: The mean RDI before treatment was 32.6 (SEM 2.1) and after the insertion of the appliance, the RDI was reduced to 12.1 (SEM 1.7, p<0.001). RDI was reduced to less than 15/hour in 80% of a group of moderate OSA patients (RDI 15 to 30) and in 61% of a group of severe OSA patients (RDI > 30) with respect to baseline RDI. Fiber optic video endoscopy was performed on 9 OSA patients with and without the appliance. No significant differences in hypopharynx or oropharynx cross sectional areas were found, but at the level of the velopharynx, the airway size was significantly increased (p<0.05). The index of agreement was 0.99 between the monitor clock time and the subject's log sheets. Compliance data from eight OSA subjects instructed to wear the appliance during sleep indicated that it was worn for a mean of 6.8 hours with a range of 5.6 to 7.5 hours per night. CONCLUSION: The titratable adjustable mandibular advancement appliance, made from thermoelastic acrylic, significantly reduces RDI in moderate to severe OSA patients, has a direct effect on airway size and is well worn throughout the night.

Amiodarone pulmonary, neuromuscular and ophthalmological toxicity.

Amiodarone is an iodinated benzofuran derivative class III antiarrhythmic that is highly effective in suppressing ventricular and supraventricular arrhythmias. It is also associated with an imposing side effect profile, which often limits its use. Numerous adverse effects have been documented including skin discolouration, photosensitivity, hepatitis, thyroid dysfunction, corneal deposits, pulmonary fibrosis, bone marrow suppression and drug interactions. These side effects are thought to be correlated with the total cumulative dose of amiodarone, but idiopathic reactions have been reported. The majority of adverse reactions resolve with discontinuation of the drug; however, rapid progression may occur, which may be fatal. The present report documents a patient who had a combination of serious amiodarone toxicities that, once recognized, were treated and eventually resulted in a good outcome.

Implanted functional electrical stimulation system for mobility in paraplegia: a follow-up case report.

A 16-channel functional electrical stimulation (FES) system has been implanted in a person with T10 paraplegia for over a year. The system consists of two eight-channel radio frequency controlled receiver-stimulators delivering stimuli through a network of 14 epimysial and two intramuscular electrodes. Using this system and a walker for support, the subject was able to stand up for 8 min and walk regularly for 20 m. The standing duration was limited by arm fatigue since upper extremities supported an average of 25% of body weight. This was due to suboptimal hip extension and some undesired recruitment of rectus femoris and sartorius with stimulation of quadriceps electrodes. The left quadriceps exhibited rapid fatigue that limited walking distance and duration. The metabolic energy requirements were well within the aerobic limits of the sedentary paraplegic population. At one-year follow-up evaluation all electrodes are functional except one intramuscular electrode. The implant caused no adverse physiological effects and the individual reported health benefits such as increased energy and overall fitness as a result of the FES system use. With further improvements in muscle response through innovative surgical techniques, the 16-channel implanted FES system can be a viable addition to exercise and mobility function in persons with paraplegia.

Walking with a hybrid orthosis system.

OBJECTIVE: The purpose of this case study was to determine the functional effectiveness of the hybrid orthosis system (HOS) for sit-to-stand and walking compared with the reciprocal gait orthosis (RGO) alone in a subject with significant orthopedic abnormalities. DESIGN: A subject with complete T7 paraplegia and a 13 cm leg length discrepancy was implanted with 14 intramuscular electrodes and fitted with a custom isocentric RGO. The subject was instructed in the use of the HOS and a two wheeled walker in the home and community settings. MAIN OUTCOME MEASURES: Using the Functional Independence Measure (FIM), and the Borg exertion scale the subject's level of independence and his perceived exertion was determined as well as the safety and efficacy of system use in the community. RESULTS: Results show that the HOS provided safe, independent ambulation with a two wheeled walker and met established criteria for limited community use. Walking in the RGO alone was feasible, however, the addition of functional electrical stimulation (FES) allowed this subject to walk farther and with less perceived exertion. CONCLUSION: This case study suggests that a hybrid orthosis system can be an effective clinical option for individuals with significant orthopedic complications that might otherwise contra-indicate the prescription of either conventional braces or FES alone.

Cephalometric characteristics of nonobese patients with severe OSA.

The purpose of this study was to determine the facial characteristics of nonobese patients with obstructive sleep apnea (OSA). Observational data on a cohort of patients was analyzed retrospectively. The subjects were classified into four groups: nonobese mild, obese mild, nonobese severe, and obese severe. The nonobese mild group included patients with a body mass index (BMI = kilogram/meter2) <25 and an apnea-hypopnea index (AHI) >5 and <15; the obese mild patients had a BMI >35 and an AHI >5 and <15; the nonobese severe patients had a BMI <25 and an AHI >40; the obese severe group had a BMI >35 and AHI >40. Thirty-three male patients referred for overnight polysomnography and lateral cephalometry who met the selection criteria were included. Between-group differences were examined pairwise by analysis of variance (ANOVA) with Bonferroni correction. Only two variables--lower facial height and overbite--were significantly different at p<0.05 between the nonobese severe group and the obese mild group. A discriminant analysis on the cephalometric measurements revealed that patients in the nonobese severe group could be distinguished from patients in other groups by their facial characteristics. OSA patients do not have a homogenous bony structure of the face. In particular, OSA severity in nonobese severe patients may be associated with a vertical skeletal disharmony.

Neural network prediction of obstructive sleep apnea from clinical criteria.

STUDY OBJECTIVES: Clinical prediction models for the diagnosis of obstructive sleep apnea (OSA) have lacked the accuracy necessary to confidently replace polysomnography (PSG). Artificial neural networks are computer programs that can be trained to predict outcomes based on experience. This study was conducted to test the hypothesis that a generalized regression neural network (GRNN) could accurately classify patients with OSA from clinical data. STUDY DESIGN: Retrospective review. SETTING: Regional sleep referral center. PATIENTS: Randomly selected records of patients referred for possible OSA. MEASUREMENTS: The neural network was trained using 23 clinical variables from 255 patients, and the predictive performance was evaluated using 150 other patients. RESULTS: The prevalence of OSA in this series of 405 patients (293 men and 112 women) was 69%. The trained GRNN had an accuracy of 91.3% (95% confidence interval [CI], 86.8 to 95.8). The sensitivity was 98.9% for having OSA (95% CI, 96.7 to 100), and the specificity was 80% (95% CI, 70 to 90). The positive predictive value that the patient would have OSA was 88.1% (95% CI, 81.8 to 94.4), whereas the negative predictive value that the patient would not have OSA (if so classified) was 98% (95% CI, 94 to 100). CONCLUSIONS: Appropriately trained GRNN has the ability to accurately rule in OSA from clinical data, and GRNN did not misclassify patients with moderate to severe OSA. In this study, use of the neural network could have reduced the number of PSG studies performed. Prospective validation of the neural network for the diagnosis of OSA is now required.

A protocol for the initial management of unstable pelvic fractures.

The initial management of life-threatening hemorrhage associated with severe pelvic fractures has long been a source of debate. A review of the literature reveals that many advocate emergent orthopedic external fixation (EX-FIX) for severe pelvic fractures, whereas others claim greater success with angiographic embolization (ANGIO) as the first line of treatment. Although many have attempted to classify management options by fracture pattern, to date there has been no prospective trial comparing outcomes for each method of treatment. We offer a prospective study of all pelvic fracture patients admitted to our Level I trauma center between July 1994 and July 1995. Patients were classified according to fracture pattern and degree of hemodynamic instability. Those with primarily anterior pelvic ring fractures underwent emergent EX-FIX for control of hemorrhage, whereas those with primarily posterior pelvic ring fractures underwent emergent ANGIO to control hemorrhage. We found that blood product requirements and hospital stay were similar in each group. However, the complication rate was higher in patients who underwent initial emergency EX-FIX, primarily because of failure to adequately control hemorrhage. We conclude that patients with anterior-posterior compression type 2 and 3, lateral compression type 2 and 3, or vertical shear injuries, who are hemodynamically unstable as a result of their pelvic fracture, should undergo immediate ANGIO if laparotomy is not indicated. If laparotomy is indicated, EX-FIX should be placed intraoperatively, followed by postoperative ANGIO.

Prevalence of sleep disordered breathing in a population of Canadian grainworkers.

OBJECTIVES: To determine the prevalence of sleep disordered breathing (SDB) in a Canadian population of industrial workers (grainworkers). To determine the clinical features that are predictive of SDB and the validity of self-reported snoring. DESIGN: Cross-sectional, interviewer-administered questionnaire with selective recruitment of subjects for home sleep monitoring. SETTING: Community setting, Vancouver, British Columbia. PARTICIPANTS: All male grainworkers at grain elevators in Vancouver were approached for completion of a questionnaire. Eighty-three per cent of 524 subjects completed the questionnaire and were divided by presumed risk for SDB into four groups. All subjects in the highest risk group (group 1- frequent snoring and witnessed apneas) and a random sample of 40 subjects in the other three groups (group 2 - frequent snoring without witnessed apneas; group 3 - infrequent snoring rare; group 4 - nonsnoring) were approached for home sleep monitoring and 42% consented. INTERVENTIONS: Interviewer-administered questionnaire and home sleep monitoring. RESULTS: The overall prevalence of SDB in this relatively overweight group was estimated to be 25%, with a stepwise increase from group 4 to group 1 (7%, 29%, 40%, 60%). Presence of snoring and witnessed apneas, a greater body-mass index and a larger neck circumference were associated with SDB. Self-reported snoring was not found to be predictive. CONCLUSIONS: This first study of the prevalence of SDB in Canada suggests that SDB is at least as prevalent in Canada as in other industrialized nations and may actually be more common than previously thought. Further studies are required to determine the morbidity, mortality and economic loss associated with SDB in industrial workers.

Effect of mandibular and tongue protrusion on upper airway size during wakefulness.

Oral appliances for the treatment of obstructive sleep apnea (OSA) produce either mandibular or tongue protrusion, and are thought to enlarge the upper airway (UA). We used videoendoscopy to measure UA cross-sectional area (CSA) and shape in the hypopharynx, oropharynx, and velopharynx during various stages of active mandibular and tongue protrusion during wakefulness in 10 patients with OSA and nine control subjects. Measurements were made in the supine position at end-tidal expiration, and were normalized to the CSA in the normal bite position. Airway shape was expressed as the anteroposterior/lateral (AP/L) diameter ratio. There were no differences between OSA patients and controls in the effects of mandibular and tongue protrusion on UA caliber. Both mandibular and tongue protrusion increased CSA in the hypopharynx and oropharynx (p < 0.001), whereas only tongue protrusion increased CSA in the velopharynx (p < 0.001). Tongue protrusion caused a greater increase in oropharyngeal and velopharyngeal CSA than did mandibular protrusion (p < 0.05). Mandibular protrusion caused a greater increase in CSA in the hypopharynx than in the oropharynx or velopharynx (p < 0.05). Obese patients had a larger relative increase in oropharyngeal CSA with mandibular and tongue protrusion than did subjects of normal weight. Tongue protrusion increased the AP/L diameter ratio in the oropharynx and velopharynx (p < 0.001), and mandibular protrusion did so to a lesser extent in the oropharynx (p < 0.01), resulting in a more circular airway shape. We conclude that mandibular and tongue protrusion increase the CSA and alter the shape of the UA during wakefulness.

A short-term controlled trial of an adjustable oral appliance for the treatment of mild to moderate obstructive sleep apnoea.

BACKGROUND: Although oral appliances are effective in some patients with obstructive sleep apnoea (OSA), they are not universally effective. A novel anterior mandibular positioner (AMP) has been developed with an adjustable hinge that allows progressive advancement of the mandible. The objective of this prospective crossover study was to compare efficacy, side effects, patient compliance, and preference between AMP and nasal continuous positive airway pressure (nCPAP) in patients with symptomatic mild to moderate OSA. METHODS: Twenty four patients of mean (SD) age 44.0 (10.6) years were recruited with a mean (SD) body mass index of 32.0 (8.2) kg/m2, Epworth sleepiness score 10.7 (3.4), and apnoea/hypopnoea index 26.8 (11.9)/hour. There was a two week wash-in and a two week wash-out period and two treatment periods (AMP and nCPAP) each of four months. Efficacy, side effects, compliance, and preference were evaluated by a questionnaire and home sleep monitoring. RESULTS: One patient dropped out early in the study and three refused to cross over so treatment results are presented on the remaining 20 patients. The apnoea/hypopnoea index (AHI) was lower with nasal CPAP 4.2 (2.2)/hour than with the AMP 13.6 (14.5)/hour (p < 0.01). Eleven of the 20 patients (55%) who used the AMP were treatment successes (reduction of AHI to < 10/hour and relief of symptoms), one (5%) was a compliance failure (unable or unwilling to use the treatment), and eight (40%) were treatment failures (failure to reduce AHI to < 10/hour and/or failure to relieve symptoms). Fourteen of the 20 patients (70%) who used nCPAP were treatment successes, six (30%) were compliance failures, and there were no treatment failures. There was greater patient satisfaction with the AMP (p < 0.01) than with nCPAP but no difference in reported side effects or compliance. CONCLUSIONS: AMP is an effective treatment in some patients with mild to moderate OSA and is associated with greater patient satisfaction than nCPAP.

Cephalometric comparisons of craniofacial and upper airway structure by skeletal subtype and gender in patients with obstructive sleep apnea.

To investigate whether patients with obstructive sleep apnea (OSA) have abnormalities in their craniofacial and upper airway (UA) structures compared with normal subjects, cephalometric comparisons were systematically performed in both the upright and the supine positions in subjects with and without OSA, who were then grouped according to their craniofacial skeletal type and gender. A total of 347 patients with OSA and 101 control subjects were divided into male and female groups and then classified into Class I (CI), Class II, Division 1 (CII/1), Class II, Division 2 (CII/2), and Class III (CIII) skeletal subtypes. In the upright position, the most atypical craniofacial and UA structure was shown in male patients with CI OSA. In patients with OSA, the degree of UA abnormalities was less in the supine position regardless of skeletal subtype. In the supine position, the most atypical craniofacial and UA structure was also shown in male patients with CI OSA; there were no significant differences between male patients with CII/2 OSA and control subjects or between female patients with CI OSA and control subjects. With a change in body position from upright to supine, distinctive changes in the UA structure in both patients with OSA and control subjects occurred, according to skeletal subtype and gender. We conclude that there are a series of characteristics of craniofacial and UA structure that differ between patients with OSA and control subjects matched for skeletal subtype and gender. These differences may predispose to UA obstruction during sleep in patients with OSA.

Oral appliance therapy for the treatment of obstructive sleep apnea.

A variety of oral appliances (OA) are now available for the treatment of obstructive sleep apnea (OSA), OA therapy is effective in some patients with mild to moderate OSA and is associated with greater patient satisfaction than nasal CPAP. Adjustable OA are associated with improved treatment success and fewer compliance failures compared to non-adjustable OA. Large randomized clinical trials are necessary to further determine the precise indications, benefits, and risks of each OA in the treatment of OSA.

Sleep-disordered breathing in amyotrophic lateral sclerosis.

OBJECTIVE: The purpose of this study was to assess sleep and breathing in patients with amyotrophic lateral sclerosis (ALS) with bulbar muscle involvement. DESIGN: Prospective, controlled study of sleep and breathing measured during polysomnography. SETTING: University teaching hospital and referral center. PATIENTS: Patients with definite ALS and healthy age-matched control subjects. INTERVENTIONS: Eighteen ALS patients and 10 age-matched control subjects underwent one night of polysomnography. Thirteen patients with ALS were studied for a second night. RESULTS: The ALS patients had more arousals per hour (p = 0.008), more stage 1 sleep (p = 0.01), and a shorter total sleep time (TST) (279 +/- 69 vs 331.4 +/- 55.9 min, mean +/- SD, p = 0.04) than the control subjects. The ALS patients had mild sleep-disordered breathing with a greater apnea/hypopnea index (AHI) than the control subjects (p = 0.005). On the second night of polysomnography, there was an increase in TST (p = 0.003) and rapid eye movement (REM) sleep (p = 0.009), an improvement in sleep efficiency (p = 0.02), and less stage 1 sleep (p = 0.04). Eight ALS patients had sleep-disordered breathing consisting of periods of hypoventilation, predominantly during REM sleep. CONCLUSIONS: Sleep-disordered breathing occurs in patients with ALS and is similar to patients without ALS with respiratory muscle weakness. No obstructive sleep apnea was observed. One potential reason for its absence might be the inability of patients with respiratory muscle weakness to generate an inspiratory pressure greater than the upper airway closing pressure. This hypothesis should be addressed in future studies.

The effect of the tongue retaining device on awake genioglossus muscle activity in patients with obstructive sleep apnea.

Knowledge of how dental appliances alter upper airway muscle activity when they are used for the treatment of snoring and/or obstructive sleep apnea (OSA) is very limited. The purpose of this study was to define the effect of a tongue retaining device (TRD) on awake genioglossus (GG) muscle activity in 10 adult subjects with OSA and in 6 age and body mass index (BMI) matched symptom-free control subjects. The TRD is a custom-made appliance designed to allow the tongue to remain in a forward position between the anterior teeth by holding the tongue in an anterior bulb with negative pressure, during sleep. This pulls the tongue forward to enlarge the volume of the upper airway and to reduce upper airway resistance. In this study, two customized TRDs were used for each subject. The TRD-A did not have an anterior bulb but incorporated lingual surface electrodes to record the GG electromyographic (EMG) activity. The TRD-B contained an anterior bulb and two similar electrodes. The GG EMG activity was also recorded while patients used the TRD-B but were instructed to keep their tongue at rest outside the anterior bulb; this condition is hereafter referred to as TRD-X. The GG EMG activity and nasal airflow were simultaneously recorded while subjects used these customized TRDs during spontaneous awake breathing in both the upright and supine position. The following results were obtained and were consistent whether subjects were in the upright or the supine position. The GG EMG activity was greater with the TRD-B than with the TRD-A in control subjects (p < 0.05), whereas the GG EMG activity was less with the TRD-B than with the TRD-A in subjects with OSA (p < 0.01). Furthermore, there was no significant difference between the GG EMG activity of the TRD-A and the TRD-X in control subjects, whereas there was less activity with the TRD-X than with the TRD-A in subjects with OSA (p < 0.05). On the basis of these findings, it was concluded that the TRD has different effects on the awake GG muscle activity in control subjects and patients with OSA. The resultant change in the anatomic configuration of the upper airway caused by the TRD may be important in the treatment of OSA because such a change may alleviate the impaired upper airway function.

Associations among upper airway structure, body position, and obesity in skeletal Class I male patients with obstructive sleep apnea.

Interactions between upper airway structure and posture in relation to obesity were studied in a sample of 61 adult Class I skeletal type male patients with obstructive sleep apnea (OSA) and 10 homologous control subjects. A pair of upright and supine lateral cephalometric films were taken for each subject. A Pearson correlation analysis identified significant r values for several demographic variables in patients with OSA such as apnea and hypopnea index, percentage of predicted neck circumference, minimum arterial oxygen saturation, and body mass index (BMI). The difference between cephalometric variables identified in upright and supine subjects was calculated. When patients with OSA changed their posture from upright to supine, significant correlations were observed between the cranial base to upper cervical column angle and the hypopharynx cross-sectional area and BMI. Moreover, the mandibular plane angle and the sella-nasion plane was significantly correlated with BMI. This occurred along with a significant positive correlation between the sella-nasion plane angle and BMI and a significant inverse correlation between the mandibular plane angle in reference to the absolute vertical and horizontal planes, with BMI after the positional change. Such correlations were not observed in control subjects. No correlations were observed between the variables related to the position of the hyoid bone with BMI in either patients with OSA or control subjects after the change in posture. On the basis of these findings, we propose that when patients with OSA change their body position from upright to supine (1) the patient's neck is more extended, and (2) the hyoid bone moves more anterosuperiorly in conjunction with an upward and forward rotation of the mandible. This change in craniofacial structure may be a compensatory geometrical change in the upper airway to secure its patency.