John A. Fleetham

Suppression of Central Sleep Apnea by Continuous Positive Airway Pressure and Transplant-Free Survival in Heart Failure A Post Hoc Analysis of the Canadian Continuous Positive Airway Pressure for Patients With Central Sleep Apnea and Heart Failure Trial (CANPAP)

Background— In the main analysis of the Canadian Continuous Positive Airway Pressure (CPAP) for Patients with Central Sleep Apnea (CSA) and Heart Failure Trial (CANPAP), CPAP had no effect on heart transplant–free survival; however, CPAP only reduced the mean apnea-hypopnea index to 19 events per hour of sleep, which remained above the trial inclusion threshold of 15. This stratified analysis of CANPAP tested the hypothesis that suppression of CSA below this threshold by CPAP would improve left ventricular ejection fraction and heart transplant–free survival. Methods and Results— Of the 258 heart failure patients with CSA in CANPAP, 110 of the 130 randomized to the control group and 100 of the 128 randomized to CPAP had sleep studies 3 months later. CPAP patients were divided post hoc into those whose apnea-hypopnea index was or was not reduced below 15 at this time (CPAP-CSA suppressed, n=57, and CPAP-CSA unsuppressed, n=43, respectively). Their changes in left ventricular ejection fraction and heart transplant–free survival were compared with those in the control group. Despite similar CPAP pressure and hours of use in the 2 groups, CPAP-CSA–suppressed subjects experienced a greater increase in left ventricular ejection fraction at 3 months (P=0.001) and significantly better transplant-free survival (hazard ratio [95% confidence interval] 0.371 [0.142 to 0.967], P=0.043) than control subjects, whereas the CPAP-CSA–unsuppressed group did not (for left ventricular ejection fraction, P=0.984, and for transplant-free survival, hazard ratio 1.463 [95% confidence interval 0.751 to 2.850], P=0.260). Conclusions— These results suggest that in heart failure patients, CPAP might improve both left ventricular ejection fraction and heart transplant–free survival if CSA is suppressed soon after its initiation.

Facial morphology and obstructive sleep apnea.

In a sample of 25 adult male subjects with moderate to severe obstructive sleep apnea, the interaction among craniofacial, airway, tongue, and hyoid variables was quantified by means of a canonical correlation analysis. One lateral cephalometric radiograph with the teeth in occlusion was obtained for each subject together with overnight polysomnographic measurements before the initiation of therapy. A principal component analysis reduced the data base and one significant canonical correlation (r1 = 0.994) was identified for the 22 variables. Sleep apnea subjects showed a posteriorly positioned maxilla and mandible, a steep occlusal plane, overerupted maxillary and mandibular teeth, proclined incisors, a steep mandibular plane, a large gonial angle, high upper and lower facial heights, and an anterior open bite in association with a long tongue and a posteriorly placed pharyngeal wall. A multivariate statistical analysis extracted clinically significant associations among craniofacial, tongue, and airway variables. Subjects with sleep apnea demonstrated several alterations in craniofacial form that may reduce the upper airway dimensions and subsequently impair upper airway stability.

Cephalometric and computed tomographic predictors of obstructive sleep apnea severity.

The interaction between craniofacial structure assessed by lateral cephalometry, and tongue, soft palate, and upper airway size determined from computed tomography (CT) scans was examined in 25 control subjects and 80 patients with obstructive sleep apnea (OSA). On the basis of the cephalometric analyses, the patients with OSA had retruded mandibles with larger ANB angle differences, elongated maxillary and mandibular incisors and mandibular molars, and high total upper and lower face heights The computed tomographic evaluations revealed that patients with OSA also had larger tongue, soft palate, and upper airway volumes. Men with OSA and skeletal Class I malocclusions had significantly larger soft palates than comparable controls. Both tongue and soft palate volumes were positively correlated with body mass index. A principal component analysis reduced the database, and one significant correlation was identified. Subjects with high total, upper and lower face heights, elongated maxillary and mandibular teeth, and proclined lower incisors were observed to have large tongue, soft palate, and upper airway volumes, to have a higher apnea index and to be obese. Linear regression analysis indicated that a high apnea index was seen in association with large tongue and soft palate volumes, a retrognathic mandible, an anteroposterior discrepancy between the maxilla and mandible, an open bite tendency between the incisors, and obesity.

Mandibular advancement oral appliance therapy for obstructive sleep apnoea: effect on awake calibre of the velopharynx

BACKGROUND The mechanisms of action of oral appliance therapy in obstructive sleep apnoea are poorly understood. Videoendoscopy of the upper airway was used during wakefulness to examine whether the changes in pharyngeal dimensions produced by a mandibular advancement oral appliance are related to the improvement in the severity of obstructive sleep apnoea. METHODS Fifteen patients with mild to moderate obstructive sleep apnoea (median (range) apnoea index (AI) 4(0–38)/h, apnoea-hypopnoea index (AHI) 28(9–45)/h) underwent overnight polysomnography and imaging of the upper airway before and after insertion of the oral appliance. Images were obtained in the hypopharynx, oropharynx, and velopharynx at end tidal expiration during quiet nasal breathing in the supine position. The cross sectional area and diameters of the upper airway were measured using image processing software with an intraluminal catheter as a linear calibration. RESULTS AI decreased to a median (range) value of 0 (0–6)/h (p<0.01) and AHI to 8 (1–28)/h (p<0.001) following insertion of the oral appliance. The median (95% confidence interval) cross sectional area of the upper airway increased by 18% (3 to 35) (p<0.02) in the hypopharynx and by 25% (11 to 69) (p<0.005) in the velopharynx, but not significantly in the oropharynx. Although in general the shape of the pharynx did not change following insertion of the oral appliance, the lateral diameter of the velopharynx increased to a greater extent than the anteroposterior diameter. Following insertion of the oral appliance the reduction in AHI was related to the increase in cross sectional area of the velopharynx (p = 0.01). CONCLUSIONS A mandibular advancement oral appliance increases the cross sectional area of the upper airway during wakefulness, particularly in the velopharynx. Assuming this effect on upper airway calibre is not eliminated by sleep, mandibular advancement oral appliances may reduce the severity of obstructive sleep apnoea by maintaining patency of the velopharynx, particularly in its lateral dimension.

Three-dimensional CT reconstructions of tongue and airway in adult subjects with obstructive sleep apnea

The interaction between airway and tongue structures in a sample of 25 adult men with obstructive sleep apnea was quantified on the basis of a series of preoperative CT slices obtained for each subject. Tracings were completed for tongue, and right and left nasal, nasopharynx, oropharynx, and hypopharynx structures; computer graphics were used to obtain superior and lateral three-dimensional reconstructions of all structures for each subject. In addition, cross-sectional areas of specific sites of airway constriction, surface area, volume, and ratio calculations were completed. The majority of the constrictions occurred in the oropharynx (0.52 +/- 0.18 cm2), but six subjects had two constrictions--one in the oropharynx and one in the hypopharynx. The airway had a mean volume of 13.89 +/- 5.33 cm3, whereas tongue volume ranged from 44.03 to 99.56 cm3 with a mean of 71.96 +/- 13.41 cm3. Subjects with more severe obstructive sleep apnea tended to have larger tongue and smaller airway volumes. The more obese subjects showed larger tongue surface areas and smaller airway surface areas. To determine the structural relationships between airway and tongue variables, a series of logarithmic plots was determined. An isometric relationship characterized tongue surface area and tongue volume. A logarithmic plot of oropharyngeal airway vs. tongue volume showed a negative allometric relationship. Tongue volume increased more rapidly than airway volume in subjects with obstructive sleep apnea. Subjects with large tongue volumes were observed to experience significant complications at the time of surgical treatment. Quantification of the volume of the oropharynx and its relationship to tongue volume provide an overview of the interaction between these structures.

A cephalometric and electromyographic study of upper airway structures in the upright and supine positions

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep, usually in the supine position. To investigate the relationship between upper airway size and genioglossus (GG) muscle activity, upright and supine cephalograms were obtained in 20 OSA patients and 10 symptom-free control subjects. Tongue electromyographic (EMG) recordings were obtained with surface electrodes, and pressure transducers were placed in the 10 symptom-free controls. The tongue cross-sectional area increased 4.3% (p < 0.05), and the oropharyngeal area decreased 36.5% (p < 0.01) when the OSA patients changed their body position from upright to supine. No changes were observed in the tongue area, but soft palate thickness increased (p < 0.01) when the control subjects changed from the upright to the supine position. Furthermore, the oropharyngeal cross-sectional area decreased 28.8% (p < 0.01) despite a 34% increase (p < 0.05) in resting GG EMG activity. Posterior tongue pressure increased 17% (p < 0.05) with the change from upright to supine. On the basis of these findings, we propose that body posture has a substantial effect on upper airway structure and muscle activity. This postural effect should be taken into account when assessing upper airway size in the erect posture (conventional cephalography) and in the supine position (computed tomography). The vertical and anteroposterior position of the tongue and its relationship to airway size may be more important than soft palate size in the pathogenesis of OSA.

The Economic Impact of Obstructive Sleep Apnea

Untreated obstructive sleep apnea (OSA) increases healthcare utilization and is associated with reduced work performance and occupational injuries. The economic burden related to untreated OSA is substantial, accounting for billions of dollars per year. Furthermore, therapy of OSA is an extremely cost-efficient use of healthcare resources, comparing highly favorably with other commonly funded medical therapies. Governments, transportation agencies, industry, and insurance companies need to be better informed concerning the economic impact of untreated OSA and the benefits of therapy.

Risk and severity of motor vehicle crashes in patients with obstructive sleep apnoea/hypopnoea

Background: Obstructive sleep apnoea/hypopnoea (OSAH) appears to be associated with an increased risk of motor vehicle crashes (MVCs). However, its impact on crash patterns, particularly the severity of crashes, has not been well described. A study was undertaken to determine whether OSAH severity influenced crash severity in patients referred for investigation of suspected sleep-disordered breathing. Methods: Objective crash data (including the nature of crashes) for 783 patients with suspected OSAH for the 3 years prior to polysomnography were obtained from provincial insurance records and compared with data for 783 age- and sex-matched controls. The patient group was 71% male with a mean age of 50 years, a mean apnoea-hypopnoea index (AHI) of 22 events/h and a mean Epworth Sleepiness Scale score of 10. Results: There were 375 crashes in the 3-year period, 252 in patients and 123 in controls. Compared with controls, patients with mild, moderate and severe OSAH had an increased rate of MVCs with relative risks of 2.6 (95% CI 1.7 to 3.9), 1.9 (95% CI 1.2 to 2.8) and 2.0 (95% CI 1.4 to 3.0), respectively. Patients with suspected OSAH and normal polysomnography (AHI 0–5) did not have an increased rate of MVC (relative risk 1.5 (95% CI 0.9 to 2.5), p = 0.21). When the impact of OSAH on MVC associated with personal injury was examined, patients with mild, moderate and severe OSAH had a substantially higher rate of MVCs than controls with relative risks of 4.8 (95% CI 1.8 to 12.4), 3.0 (95% CI 1.3 to 7.0) and 4.3 (95% CI 1.8 to 8.9), respectively, whereas patients without OSAH had similar crash rates to controls with a relative risk of 0.6 (95% CI 0.2 to 2.5). Very severe MVCs (head-on collisions or those involving pedestrians or cyclists) were rare, but 80% of these occurred in patients with OSAH (p = 0.06). Conclusion: Patients with OSAH have increased rates of MVCs, and disproportionately increased rates of MVCs are associated with personal injury.

Sleep bruxism in patients with sleep-disordered breathing

The aim was to test the hypothesis of a direct association between sleep-disordered breathing and sleep bruxism. The frequency of masseter contraction (MC) episodes and rhythmic jaw movements (RJM) was measured in patients with mild and moderate obstructive sleep apnoea (OSA). The diagnosis of sleep bruxism was made from a combination of questionnaire, clinical observation and all-night polysomnographic recording which included masseter electromyography. A total of 21 patients (19 males/two females, mean age 40.0 years+/-9.2 SD) were randomly selected from a provisional diagnosis of snoring and OSA by a sleep physician. In the patients with mild OSA [n=11, mean apnoea hypopnoea index (AHI)=8.0+/-4.1 SD, body mass index (BMI)=29.1+/-5.0], the diagnosis of sleep bruxism was made in six out of 11 patients (54%); similarly, four out of 10 patients (40%) with moderate OSA (n=10, mean AHI=34.7+/-19.1, BMI=30.6+/-5.0) were identified as bruxists. Although the combination of clinical, subjective estimation and nocturnal electromyographic recording of masseter muscle might provide a more solid base for the diagnosis of sleep bruxism, the result is biased by the variation in the bruxing activity. MC episodes were associated with the termination of apnoea or hypopnoea episodes in only 3.5% of the mild group and 14.4% of the moderate group (p<0.05). It appears that sleep bruxism is rarely directly associated with apnoeic events, but is rather related to the disturbed sleep of OSA patients.

Canadian Thoracic Society guidelines: Diagnosis and treatment of sleep disordered breathing in adults

The Canadian Thoracic Society (CTS) guidelines for the diagnosis and treatment of sleep disordered breathing in adults were developed over the past year. A one-day meeting was held in Montreal, Quebec, on October 28, 2005, just before the annual CTS meeting. The meeting was facilitated by Dr R Davies (Oxford, United Kingdom), and speakers included D Morrison (Halifax, Nova Scotia), J Kimoff (Montreal), J Fleetham (Vancouver, British Columbia), C George (London, Ontario), M Kryger (Winnipeg, Manitoba), P Hanly (Calgary, Alberta), F Hill (Saskatoon, Saskatchewan), D Bradley (Toronto, Ontario), N Ayas (Vancouver), M Fitzpatrick (Kingston, Ontario), F Series (Quebec City, Quebec), K Ferguson (London) and W Tsai (Calgary). This meeting was attended by 28 Canadian physicians with an interest in sleep disordered breathing. A draft of an Executive Summary was developed, and then reviewed and finalized by the CTS Sleep Disordered Breathing Committee at a one-day meeting in Toronto on February 17, 2006. The Committee members then individually ranked the level of evidence as: grade A – high-quality meta-analysis or single randomized clinical trial (RCT) that had a low risk of bias; grade B – high-quality systematic review of cohort studies or single cohort study with a low risk of bias or extrapolated evidence from high-quality RCTs or RCTs with a risk of bias; grade C – case-control studies or cohort studies with a risk of bias; or grade D – case series, case reports or expert opinion. The Committee members also ranked their agreement with each statement (strongly agree, agree, neutral, disagree or strongly disagree). No statement was included unless at least 90% of the Committee either strongly agreed or agreed with it.