Utility of actigraphy in the diagnosis of obstructive sleep apnea

STUDY OBJECTIVES: To determine whether adding actimetry to simplified polygraphy (respiratory-parameter monitoring without neurophysiologic variable recording) improves apnea-hypopnea index (AHI) evaluation as compared to simplified polygraphy alone. DESIGN: Comparison of AHI values obtained by all-night polysomnography and by simplified polygraphy with and without actimetry. SETTING: A teaching-hospital sleep laboratory in Garches, France. PATIENTS: 20 adults with suspected obstructive sleep apnea syndrome (OSAS). MEASUREMENTS AND RESULTS: Data were analyzed by two scorers working independently. AHI was calculated as the number of apneas and hypopneas per hour of sleep time (polysomnography: AHI-pg), per hour of time in bed (simplified polygraphy: AHI-tib), and per hour of actimetry-estimated total sleep time (AHI-act). AHI-pg showed that 12 patients had OSAS (AHI>10), which was severe (AHI > or =30) in eight. AHI-act was more closely correlated to AHI-pg (r=0.976) than was AHI-tib (r=0.940). According to the Bland and Altman method, AHI-tib underestimated the AHI in two patients and AHI-act overestimated the AHI in one patient. For the diagnosis of severe OSAS, sensitivity and negative predictive value were 50% and 75% with AHI-tib as compared to 88% and 92.5% with AHI-act. CONCLUSIONS: Actimetry, when added to simplified polygraphy, may assist in the diagnosis of OSAS.     

Accuracy of oximetry with thermistor (OxiFlow) for diagnosis of obstructive sleep apnea and hypopnea

OBJECTIVES: To evaluate the diagnostic accuracy for obstructive sleep apnea and hypopnea (OSAH) of the OxiFlow (OF) device which combines oximetry with recording of thermistor airflow. DESIGN & SETTING: Patients scheduled for overnight diagnostic polysomnography (PSG) were studied with OF either simultaneously during laboratory PSG (L-OF, n=86), at home on a separate night (H-OF, n=66), or both (n=55). PATIENTS: 97 patients with suspected OSAH, of whom 40 had OSAH defined as an apnea-hypopnea index (AHI) of more than 15 events per hour of sleep on PSG. INTERVENTIONS: NA. MEASUREMENTS & RESULTS: The automated respiratory disturbance index (RDI) generated by the OF software considerably underestimated the AHI by PSG for both L-OF and H-OF. Altering the parameters for hypopnea identification by the software did not improve this. Visual inspection of the computerized OF tracings added considerable diagnostic information, but a manual count of RDI during visual review overestimated AHI. For the identification of cases vs. non-cases of OSAH, receiver operating characteristic area-under-the-curve statistics ranged from 0.77-0.90 for L-OF and from 0.71-0.77 for H-OF. Combining automated analysis with subsequent visual inspection of OF tracings yielded an overall sensitivity of 86% and specificity of 74% for the diagnosis of OSAH during H-OF recordings. Analysis of potential technician time saved indicated a benefit from the use of OF. CONCLUSIONS: OF has diagnostic utility for the identification of OSAH. However, because of hardware and software limitations, it is unclear whether this device is superior to oximetry alone.     

The use of clinical prediction formulas in the evaluation of obstructive sleep apnea

STUDY OBJECTIVES: To prospectively study the utility of four clinical prediction models for either predicting the presence of obstructive sleep apnea (OSA, apnea-hypopnea index [AHI] > or = 10/hour), or prioritizing patients for a split-night protocol (AHI(3)20/hour). DESIGN: All patients presenting for OSA evaluation completed a research questionnaire that included questions from previously developed clinical prediction models. The probability of sleep apnea for each patient for each model was calculated based upon the equation used in the model. Based upon two cutoffs of apnea-hypopnea index, 10 and 20, the sensitivity, specificity, and positive predictive value were calculated. For the cutoffs AHI > or =10 and > or =20, receiver operating characteristic curves were generated and the areas under the curves calculated. Comparisons of demographic information and symptom response were compared between patients with and without OSA, and men vs. women. SETTING: Urban, accredited sleep disorders center. PATIENTS OR PARTICIPANTS: All patients referred for evaluation of OSA who underwent polysomnography. INTERVENTIONS: N/A. RESULTS: 370 patients (191 men, 179 women) completed the study. 248 of the 370 (67%) patients had an AHI(3)10; 180 of the 370 (49%) had an AHI> or =20. For AHI > or =10, the sensitivities ranged from 76 to 96%, specificities from 13%-54%, positive predictive values from 69%-77% using the probability cutoff of the original investigators; the areas under the curve from 0.669 to 0.736. For AHI(3)20, the areas under the ROC curves ranged from 0.700 to 0.757; using cutoffs to maximized specificity, the sensitivities ranged from 33%-39%, specificities from 87%-93%, and positive predictive values from 72%-85%. All the models performed better for men. CONCLUSIONS: The clinical prediction models tested are not be sufficiently accurate to discriminate between patients with or without OSA but could be useful in prioritizing patients for split-night polysomnography.     

Obstructive sleep apnea in Costello syndrome

Costello syndrome (CS) was initially described by Costello in 1971; it is caused by a germline mutation in HRAS proto-oncogene. The aim of the present study was to evaluate the respiratory activity during sleep in a group of subjects with CS. We studied 10 consecutive patients, 4 males and 6 females, aged 3-29 years, affected by CS. All patients underwent clinical, neurological, otholaryngologic and radiologic evaluation, and a full-night polysomnography in the sleep laboratory. Polysomnography showed that seven patients presented a relevant number of respiratory events of obstructive type during sleep. The apnea-hypopnea index (AHI) ranged from 0 to 19.2 events per hour (mean index = 7.5 +/- 6.9 events/hr). In one patient AHI was not evaluable because of tracheostomy. Apnea induced mild or moderate hemoglobin desaturations (mean of lowest SpO2 values = 85.4 +/- 5.5%). Only sporadic respiratory pauses of central type were observed (mean number of central apnea per study: 7.2 +/- 6.8 events/hr). Sleep structure was fragmented, with a high number of awakenings (mean number of awakenings was 13.2 +/- 8.1; of these, 4.8 +/- 2.5 lasted longer than 2 min). In all patients, otolaryngologic and radiologic observations revealed one or more sites of narrowing in the upper airways. Our results suggest that Costello patients have a high prevalence of obstructive sleep-related respiratory disorders, which need to be assessed by means of polysomnography.     

Lateral sleeping position reduces severity of central sleep apnea / Cheyne-Stokes respiration

INTRODUCTION: The influence of sleeping position on obstructive sleep apnea severity is well established. However, in central sleep apnea with Cheyne Stokes respiration (CSA-CSR) in which respiratory-control instability plays a major pathophysiologic role, the effect of position is less clear. STUDY OBJECTIVES: To examine the influence of position on CSA-CSR severity as well as central and mixed apnea frequency. METHODS: Polysomnograms with digitized video surveillance of 20 consecutive patients with heart failure and CSA-CSR were analyzed for total apnea-hypopnea index, mean event duration, and mean oxygen desaturation according to sleep stage and position. Position effects on mixed and central apnea index, mean apnea duration, and mean desaturation were also examined in non-rapid eye movement sleep. RESULTS: Data are presented as mean +/- SEM unless otherwise indicated. Group age was 59.9 +/- 2.3 years, and total apnea-hypopnea index was 26.4 +/- 3.0 events per hour. Compared with supine position, lateral position reduced the apnea-hypopnea index in all sleep stages (Stage 1, 54.7 +/- 4.2 events per hour vs 27.2 +/- 4.1 events per hour [p < .001]; Stage 2, 43.3 +/- 6.1 events per hour vs 14.4 +/- 3.6 events per hour [p < .001]; slow-wave sleep, 15.9 +/- 6.4 events per hour vs 5.4 +/- 2.9 events per hour [p < .01]; rapid eye movement sleep, 38.0 +/- 7.3 events per hour vs 11.0 +/- 3.0 events per hour [p < .001]). Lateral position attenuated apnea and hypopnea associated desaturation (supine 4.7% +/- 0.3%, lateral 3.0% +/- 0.4%; p < .001) with no difference in event duration (supine 25.7 +/- 2.8 seconds, lateral 26.9 +/- 3.4 seconds; p = .921). Mixed apneas were longer than central (29.1 +/- 2.1 seconds and 19.3 +/- 1.1 seconds; p < .001) and produced greater desaturation (6.1% +/- 0.5% and 4.5% +/- 0.5%, p = .003). Lateral position decreased desaturation independent of apnea type (supine 5.4% +/- 0.5%, lateral 3.9% < or = 0.4%; p = .003). CONCLUSIONS: Lateral position attenuates severity of CSA-CSR. This effect is independent of postural effects on the upper airway and is likely to be due to changes in pulmonary oxygen stores. Further studies are required to investigate mechanisms involved.     

Comparison of limited monitoring using a nasal-cannula flow signal to full polysomnography in sleep-disordered breathing

STUDY OBJECTIVES: Evaluate the utility of overnight monitoring limited to nasal cannula airflow and oximetry in the diagnosis of obstructive sleep apnea-hypopnea syndrome (OSAHS). DESIGN: Prospective randomized study, blinded analysis. SETTING: Sleep disorder center, academic institution. PARTICIPANTS: 56 patients with suspected OSAHS, 10 normal volunteers. MEASUREMENTS AND RESULTS: In-laboratory full nocturnal polysomnography (NPSG) and unattended ambulatory study with monitoring of only airflow and oximetry performed in randomized order. Obstructive respiratory events were scored on the full NPSG while visualizing all signals and then rescored on the full NPSG and on the ambulatory study while visualizing only airflow and oximetry signals. Respiratory disturbance indexes (RDI) for the limited studies (RDIFlowNPSG and RDIFlowAmbulatory) were calculated as the sum of the apneas and hypopneas (defined using airflow amplitude and O2 desaturation) divided by the valid flow-signal time. The reference RDIFullNPSG was calculated from the sum of the apneas and hypopneas (defined using flow amplitude, O2 desaturation and electroencephalographic arousal) identified on the full NPSG divided by the total sleep time. RDIFullNPSG was greater than RDIFlowNPSG (bias = 5.6 events per hour) and RDIFlowAmbulatory (bias = 10.9 events per hour), but the differences were mainly in subjects with an RDI > 40 events per hour. The diagnostic sensitivity and specificity for the diagnosis of OSAHS using a cutoff of 18 events per hour were 96% and 93% using the flow signal from the NPSG and 88% and 92% using the flow signal from the ambulatory study performed on a separate night. CONCLUSIONS: In subjects with OSAHS, analysis of the flow signal from a nasal cannula can provide an RDI similar to that obtained in a full NPSG.     

Sleep-disordered breathing and cardiovascular disease in the Bay Area Sleep Cohort

STUDY OBJECTIVES: To examine the relationship between sleep-disordered breathing (SDB) and cardiovascular disease among community-dwelling older adults. Previous studies have suggested relatively stronger associations between SDB and such morbidity in middle-aged, relative to elderly, populations. DESIGN: Cross-sectional analysis of an elderly ambulatory, non-clinic-based cohort (Bay Area Sleep Cohort, BASC) SETTING: Community population studied in a sleep laboratory PARTICIPANTS: One hundred twenty-nine older adults (mean [+/- SD] age = 72.6 [8.3]) (78 women; 51 men). INTERVENTIONS: NA. MEASUREMENTS: Complete clinical history including list of current medications, physical examination, selected blood chemistries, multiple blood pressure measurements, 12-lead electrocardiogram, and 2 consecutive nights of polysomnography. RESULTS: Fifty-one individuals (40%) were taking 1 or more cardiovascular medications and 24 (19%) had an apnea-hypopnea index (AHI) of 10 or more per hour of sleep. Cardiovascular medication use was related to cardiac events or procedures, history of angina, higher systolic or diastolic blood pressure, and abnormal electrocardiogram. Logistic regression showed statistically significant association between cardiovascular medication use and AHI of 10 or greater per hour, independent of age, sex, and body mass index. Supplementary analyses indicated that rapid eye movement AHI of 10 or greater per hour was significantly associated with elevated diastolic blood pressure. CONCLUSIONS: The results suggest that sleep-disordered breathing may contribute to increased cardiovascular morbidity in older adults.     

Effects of nasal O2 on sleep-related disordered breathing in ambulatory patients with stable heart failure

OBJECTIVE: The purpose of this study was 1) to determine the effects of nasal O2 on periodic breathing, arterial oxyhemoglobin desaturation and nocturnal ventricular arrhythmias in patients with heart failure and 2) determine the characteristics of patients whose periodic breathing will be reversed by O2 administration; our hypothesis was that patients with more severe periodic breathing and desaturation, will respond more favorably to oxygen. DESIGN: Prospective study. SETTING: Referral sleep laboratory of a Department of Veterans Affairs Medical Center. PARTICIPANTS: 36 ambulatory male patients with heart failure whose initial polysomnograms showed periodic breathing with fifteen or more episodes of apnea (A) and hypopnea (H) per hour (AH index, AHI) were treated with nasal O2 during the subsequent full night polysomnography. INTERVENTIONS: Oxygen. MEASUREMENTS AND RESULTS: Arterial blood gases and hydrogen ion concentrations were measured, and cardiac radionuclide ventriculography, Holter monitoring, and polysomnography were done. The studies were scored blindly. Treatment with O2 resulted in a significant reduction in AHI (49+/-19 vs 29+/-29, means+/-SD), central apnea index (28+/-23 vs 13+/-18 per hour), and the percent of total sleep time below an arterial oxyhemoglobin saturation of 90% (23+/-21% vs 0.8+/-2.3%). In spite of virtual normalization of saturation with O2 therapy, the number of ventricular arrhythmias during sleep did not change significantly. In 39% of the patients (14 out of 36), O2 therapy resulted in reversal of central sleep apnea (defined by a reduction in AHI to less than 15/hr). In this group, the AHI decreased by 78% which was significantly (p=0.0001) more than improved (22%) in AHI of the remaining patients (n=22). The main differences between baseline characteristics of the two groups was a significantly higher mean PaCO2 in patients who did respond fully to O2 (39.3+/-5.4 vs 36.1+/-4.2 mm Hg, p=0.03). In both groups, however, O2 administration resulted in significant and similar improvement in arterial oxyhemoglobin saturation (saturation <90%, percent total sleep time 0.1+/-0.3% vs 1+/-3%). CONCLUSION: In patients with stable heart failure, administration of nasal O2 significantly improves periodic breathing and virtually eliminates clinically significant arterial oxyhemoglobin desaturation. The beneficial effects of O2, however, may be modulated by the level of arterial PCO2. Acute O2 therapy has important benefits on sleep apnea and nocturnal arterial oxyhemoglobin desaturation in heart failure patients. Long term benefits of O2 therapy in heart failure and sleep apnea need to be determined.     

Validation a portable monitoring device for sleep apnea diagnosis in a population based cohort using synchronized home polysomnography

SUBJECT OBJECTIVE: To assess the accuracy of a portable monitoring device based on peripheral arterial tonometry to diagnose obstructive sleep apnea (OSA). To propose a new standard for limited-channel device validation using synchronized polysomnography (PSG) home recordings and a population-based cohort. DESIGN: Single-night, unattended PSG and Watch_PAT 100 (WP_100). SETTING: Home environment. PARTICIPANTS: Ninety-eight subjects (55 men; age, 60 +/- 7 year; body mass index, 28 +/- 4 kg/m2) consecutively recruited from the Skaraborg Hypertension and Diabetes Project. MEASUREMENTS AND RESULTS: The WP_100 records peripheral arterial tone, heart rate, oxygen saturation and actigraphy for automatic analysis of respiratory disturbance index (RDI), apnea-hypopnea index (AHI), oxygen desaturation index (ODI), and sleep-wake state. The accuracy of WP_100 in RDI, AHI, ODI, and sleep-wake detection was assessed by comparison with data from simultaneous PSG recordings. The mean PSG-AHI in this population was 25.5 +/- 22.9 events per hour. The WP_100 RDI, AHI, and ODI correlated closely (0.88, 0.90, and 0.92; p < .0001, respectively) with the corresponding indexes obtained by PSG. The areas under the curve for the receiver-operator characteristic curves for WP_100 AHI and RDI were 0.93 and 0.90 for the PSG-AHI and RDI thresholds 10 and 20 (p < .0001, respectively). The agreement of the sleep-wake assessment based on 30-second bins between the 2 systems was 82 +/- 7%. CONCLUSIONS: The WP_100 was reasonably accurate for unattended home diagnosis of OSA in a population sample not preselected for OSA symptoms. The current design, including simultaneous home PSG recordings in population-based cohorts, is proposed as a reasonable validation standard for assessment of simplified recording tools for OSA diagnosis.     

Age-related changes in cerebral lactate metabolism in sleep-disordered breathing

Thirty-one patients, aged 22-71 years, with nocturnal apneic episodes and/or habitual snoring were studied with magnetic resonance spectroscopy (MRS) and diagnostic polysomnography separately to determine whether accumulation of lactate caused by cerebral hypoxia during sleep is associated with sleep-disordered breathing (SDB), aging and co-morbidities related to SDB. Eight proton magnetic resonance spectra for sleep and two for periods of arousal were obtained from the right centrum semiovale. All patients were evaluated for the presence or absence of co-morbidities including hypertension, cardiac disease, diabetes mellitus, and hyperlipidemia. Significant lactate signals were found in seven patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) during sleep periods, and none during periods of arousal. Aging was significantly related to the presence or absence of significant lactate signals during sleep periods as determined by logistic regression analysis (beta=0.2480; 95% confidence interval, 0.0905-0.5094; P=0.0001). Apnea index (AI), apnea-hypopnea index (AHI), and minimum value of peripheral oxyhemoglobin saturation each significantly interacted with age (P=0.0081, 0.0284, and 0.0302, respectively). Our findings suggest that SDB combined with aging is related to accumulation of lactate during sleep.     

Rapid maxillary expansion in children with obstructive sleep apnea syndrome

OBJECTIVE: To evaluate the effect of rapid maxillary expansion on children with nasal breathing and obstructive sleep apnea syndrome. METHOD: Recruitment of children with maxillary contraction, without of adenoid hypertrophy, with a body mass index < 24 kg/m2, with obstructive sleep apnea syndrome demonstrated by polysomnography, and whose parents signed informed consent. Otolaryngologic and orthognathic-odontologic evaluation with clinical evaluation, anterior rhinometry and nasal fibroscopy, panoramic radiographs, anteroposterior and laterolateral telecephalometry were performed at entry and follow-up. Intervention: Rapid maxillary expansion (ie, active phase of treatment) was performed for 10 to 20 days; maintenance of device (for consolidation) and orthodontic treatment on teeth lasted 6 to 12 months. RESULTS: 31 children (19 boys), mean age 8.7 years, participated in the study. The mean apnea-hypopnea index was 12.2 events per hour. At the 4-month follow-up, the anterior rhinometry was normal, and all children had an apnea-hypopnea index < 1 event per hour. The mean cross-sectional expansion of the maxilla was 4.32 +/- 0.7 mm. There was a mean increase of the pyriform opening of 1.3 +/- 0.3 mm. CONCLUSION: Rapid maxillary expansion may be a useful approach in dealing with abnormal breathing during sleep.     

Severity of sleep-disordered breathing improves following parturition

STUDY OBJECTIVE: Changes in sleep-disordered breathing associated with late pregnancy have not previously been systematically investigated; however, a number of case reports indicate exacerbation of obstructive sleep apnea in late pregnancy, often in association with maternal hypertension. We aimed to compare the severity of sleep-disordered breathing and associated maternal blood-pressure responses in late pregnancy with the nonpregnant state. DESIGN: Case-controlled, longitudinal study of sleep-disordered breathing during late pregnancy and postpartum. Study Patients: Ten women referred for suspected sleep-disordered breathing during the third trimester of pregnancy. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Full overnight polysomnography and continuous systemic blood pressure were measured during the third trimester of pregnancy and 3 months following delivery. Parameters of sleep-disordered breathing, including apnea hypopnea index and minimum overnight arterial oxyhemoglobin saturation, were compared between antenatal and postnatal studies. An improvement in both apnea-hypopnea index and minimum arterial oxyhemoglobin saturation occurred consistently in all subjects postnatally. In non-rapid eye movement sleep, mean apnea-hypopnea index was reduced from 63 +/- 15 per hour antenatally to 18 +/- 4 per hour postnatally (P = .03), and in rapid eye movement sleep, from 64 +/- 11 per hour to 22 +/- 4 per hour (P = .002). Minimum arterial oxyhemoglobin saturation was increased from 86% +/- 2% antenatally to 91% +/- 1% postnatally (P = .01). Arterial blood-pressure responses to apnea peaked at 170 to 180 mm Hg antenatally, while they only peaked at 130 to 140 mm Hg postnatally. CONCLUSION: This study indicates that late pregnancy may be associated with increased severity of sleep-disordered breathing and associated blood-pressure responses.     

Automated frequency domain analysis of oxygen saturation as a screening tool for SAHS

Sleep apnea-hypopnea syndrome (SAHS) is significantly underdiagnosed and new screening systems are needed. The analysis of oxygen desaturation has been proposed as a screening method. However, when oxygen saturation (SpO(2)) is used as a standalone single channel device, algorithms working in time domain achieve either a high sensitivity or a high specificity, but not usually both. This limitation arises from the dependence of time-domain analysis on absolute SpO(2) values and the lack of standardized thresholds defined as pathological. The aim of this study is to assess the degree of concordance between SAHS screening using offline frequency domain processing of SpO(2) signals and the apnea-hypopnea index (AHI), and the diagnostic performance of such a new method. SpO(2) signals from 115 subjects were analyzed. Data were divided in a training data set (37) and a test set (78). Power spectral density was calculated and related to the desaturation index scored by physicians. A frequency desaturation index (FDI) was then estimated and its accuracy compared to the classical desaturation index and to the apnea-hypopnea index. The findings point to a high diagnostic agreement: the best sensitivity and specificity values obtained were 83.33% and 80.44%, respectively. Moreover, the proposed method does not rely on absolute SpO(2) values and is highly robust to artifacts.     

Tongue-muscle training by intraoral electrical neurostimulation in patients with obstructive sleep apnea

STUDY OBJECTIVES: To investigate the efficacy of tongue-muscle training by electrical neurostimulation of the upper-airway muscles as an alternative therapy option for obstructive sleep apnea syndrome. DESIGN: A randomized, placebo-controlled, double-blind study. SETTING: Department of pneumology and sleep laboratory, University of Witten/Herdecke, Germany. PATIENTS: 67 patients with an apnea-hypopnea index of 10 to 40 per hour were randomly assigned to 2 groups: a treatment group of 33 patients (mean age, 50.8 +/- 12.1 years; mean body mass index, 29.1 +/- 4.4 kg/m2) and a placebo group of 34 patients (mean age, 53.3 +/- 11.3 years; mean body mass index, 28.9 +/- 4.9 kg/m2). Fifty-seven patients completed the study. INTERVENTIONS: Tongue-muscle training during the daytime for 20 minutes twice a day for 8 weeks. MEASUREMENTS AND RESULTS: Treatment efficacy was examined by polysomnography. Snoring, but not apnea-hypopnea index, improved with stimulation (snoring baseline, 63.9 +/- 23.1 epochs per hour; stimulation training, 47.5 +/- 31.2; P < .05) but not with placebo training (snoring baseline, 62.4 +/- 26.1 epochs per hour; placebo, 62.1 +/- 23.8; NS.). CONCLUSIONS: Although tongue-muscle training cannot generally be recommended for the treatment of sleep apnea, the method has proven to be effective in the treatment of snoring.     

Periodic limb movements in children: prevalence in a referred population

STUDY OBJECTIVES: To determine the prevalence of periodic limb movements of sleep (PLMS) in children referred for evaluation of sleep disorders. DESIGN: A retrospective analysis of all overnight polysomnograms (PSG) performed at a tertiary-level pediatric care facility. SETTING: All PSG studies were performed in the pediatric sleep laboratory associated with the Alberta Children's Hospital in Calgary, AB, Canada. The pediatric sleep laboratory was situated in the Foothills Hospital Alberta Lung Association Sleep Center until August 2002. At that time, the pediatric sleep laboratory was relocated to the Alberta Children's Hospital. PARTICIPANTS: All children of any age undergoing PSG for any reason between October 1999 and March 2003. MEASUREMENTS AND RESULTS: All PSG records were reviewed, and the following data was extracted: periodic limb movement index (PLM index), periodic limb movements with arousal index (PLM w/arousal index), apnea-hypopnea index (AHI), and patient demographics (age, sex, comorbidities). A total of 591 PSG studies were reviewed. Thirty-three of the 591 children (5.6%) had evidence of PLMs > 5 per hour. Twenty of the 33 (60.0%) had coexistent obstructive sleep apnea (AHI > 1/hour). Only 7 of the 591 children studied (1.2%) had evidence of PLM > 5 per hour with no other comorbidity. Two of 13 children with PLM > 5 per hour and no evidence of obstructive sleep apnea had attention-deficit/hyperactivity disorder. The prevalence of PLMS in the 28 of the 591 subjects with a preexisting diagnosis of ADHD was increased at 7.1%. CONCLUSIONS: PLMS is an uncommon disorder of childhood. In a select population at increased risk for having a sleep disorder, the prevalence of isolated PLMS is only 1.2%.     

Total duration of apnea and hypopnea events and average desaturation show significant variation in patients with a similar apnea–hypopnea index

Obstructive sleep apnea (OSA) is commonly diagnosed based on the apnea-hypopnea index (AHI). Presently, novel indices were introduced for sleep apnea severity: total duration of sleep apnea and hypopnea events (TAHD%) and a combined index including duration and severity of the events (TAHD% × average desaturation). Two hundred and sixty-seven subjects were divided based on their AHI into four categories (normal, mild, moderate, severe OSA). In the most severe cases TAHD% exceeded 70% of the recorded time. This is important as excessive TAHD% may increase mortality and cerebro-vascular complications. Moreover, simultaneous increase in duration and frequency of apnea and hypopnea events leads to a paradoxical situation where AHI cannot increase along severity of the disease. Importantly, the combined index including duration and severity of the events showed significant variation between patients with similar apnea-hypopnea indices. To conclude, the present results suggest that the novel parameters could give supplementary information to AHI when diagnosing the severity of OSA.     

Association between atrial fibrillation and central sleep apnea

BACKGROUND: We previously described an association between atrial fibrillation and central sleep apnea in a group of patients with congestive heart failure. We hypothesized that the prevalence of atrial fibrillation might also be increased in patients with central sleep apnea in the absence of other cardiac disease. METHODS AND RESULTS: We compared the prevalence of atrial fibrillation in a series of 60 consecutive patients with idiopathic central sleep apnea (apnea-hypopnea index > 10 events per hour, > 50% central events) with that in 60 patients with obstructive sleep apnea (apnea-hypopnea index > 10, > 50% obstructive events) and 60 patients without sleep apnea (apnea-hypopnea index < 10), matched for age, sex, and body mass index. Subjects with a history of congestive heart failure, coronary artery disease, or stroke were excluded from the study. The prevalence of atrial fibrillation among patients with idiopathic central sleep apnea was found to be significantly higher than the prevalence among patients with obstructive sleep apnea or no sleep apnea (27%, 1.7%, and 3.3%, respectively, P < .001). However, hypertension was most common and oxygen desaturation most extreme among patients with obstructive sleep apnea. CONCLUSIONS: We conclude that there is a markedly increased prevalence of atrial fibrillation among patients with idiopathic central sleep apnea in the absence of congestive heart failure. Moreover, the high prevalence of atrial fibrillation among patients with idiopathic central sleep apnea is not explainable by the presence of hypertension or nocturnal oxygen desaturation, since both of these were more strongly associated with obstructive sleep apnea.     

Screening for subclinical sleep-disordered breathing

We evaluated self-administered questionnaires and short sleep studies in screening for sleep-disordered breathing (SDB) in 40 hypertensive men ages 36-66 unselected for symptoms. Each subject completed a questionnaire including questions on sleep-related symptoms and underwent overnight polysomnography in which we evaluated the apnea-hypopnea index (AHI) and the percentage of time during which arterial O2 saturation was less than 90% (T90). The first 90 min of overnight study was evaluated separately, and 10 subjects with an AHI greater than or equal to 10 also underwent late afternoon nap study. By overnight polysomnography, 48% of the cohort had an AHI greater than or equal to 10, and 35% had a T90 greater than or equal to 10%. Using linear regression, we found no features of the symptom questionnaire that strongly predicted AHI. Only self-reported snoring and baseline arterial Po2 significantly predicted T90. The AHI and T90 were not significantly correlated. Considering an AHI greater than or equal to 10 in the overnight study as "abnormal" and an AHI greater than or equal to 10 on the short study as a "positive" test, the specificity of the AHI in the first 90 min was 100% (21/21), and the sensitivity was 42% (8/19). The sensitivity of the nap study was 60% (6/10). We conclude that in a cohort unselected for symptoms, the ability of self-administered questionnaires to predict SDB was low; short studies were only moderately sensitive for detecting an AHI greater than or equal to 10, and the AHI was not a major determinant of nocturnal desaturation.     

Oropharyngeal collapse predicts treatment response with oral appliance therapy in obstructive sleep apnea

STUDY OBJECTIVES: To examine whether primary oropharyngeal collapse of the upper airway during sleep predicts treatment success with oral appliance therapy in patients with obstructive sleep apnea. DESIGN: Prospective physiologic study. SETTING: Multidisciplinary sleep disorders clinic in a university teaching hospital. PATIENTS: Twelve treatment-na?ve adult patients with obstructive sleep apnea (apnea-hypopnea index > or = 10/h and at least 2 of the following symptoms: snoring, fragmented sleep, witnessed apneas, or daytime sleepiness). INTERVENTION: Custom-made mandibular advancement splint (MAS). MEASUREMENTS AND RESULTS: A baseline diagnostic polysomnogram confirmed AHI > or = 10 per hour. During the following acclimatization period, a custom-made adjustable MAS was incrementally advanced until maximum comfortable mandibular protrusion was reached. A second polysomnogram with MAS in situ determined efficacy. Following a 1-week washout period, a final sleep study was performed using multisensor catheters (with and without MAS, in random order during the same night) to determine upper-airway closing pressures and the site or sites of upper-airway collapse. MAS resulted in significant improvements, mean +/- SEM, in AHI (22.0 +/- 2.6 vs 9.2 +/- 1.9/h, p < .01) and upper-airway closing pressures during stage 2 non-rapid eye movement sleep (-1.1 +/- 0.3 vs -2.8 +/- 0.5 cm H2O, p < .01). All 4 patients with primary oropharyngeal collapse achieved an AHI < 5 per hour. Only 1 of the 8 patients with primary velopharyngeal collapse achieved an AHI < 5 per hour. Oropharyngeal collapse, compared with velopharyngeal collapse, predicted treatment success with MAS (p < .02). CONCLUSIONS: These preliminary data suggest that primary oropharyngeal collapse of the upper airway during sleep is an important predictor of treatment outcome with MAS therapy.     

Children with obstructive sleep-disordered breathing generate high-frequency inspiratory sounds during sleep

STUDY OBJECTIVES: We observed that some children with adenotonsillar hypertrophy and obstructive sleep-disordered breathing (SDB) make high-frequency inspiratory sounds (HFIS) during sleep. Our objective was to determine whether HFIS occur in most children with obstructive SDB and adenotonsillar hypertrophy and whether adenotonsillectomy reduces HFIS. DESIGN: Prospective consecutive-entry trial. SETTING: Sleep laboratory. PARTICIPANTS: Twenty-six children between 6 and 12 years of age with adenotonsillar hypertrophy suspected of having obstructive SDB. MEASUREMENTS AND RESULTS: We performed polysomnography and measured sounds during sleep with a microphone suspended above the bed. Sounds were recorded on a computer at 44 kHz, analyzed with fast Fourier transformation for frequency content. HFIS were sounds occurring during an inspiration with frequencies greater than 2 kHz. HFIS were different from the low-frequency (< 2 kHz) sounds described in snoring adults. HFIS usually occurred in consecutive breaths, occasionally exceeding 100. We counted the number of HFIS that occurred per hour of sleep. Children who made more HFIS had more obstructive SDB than did those who did not make the HFIS, and there was a significant positive correlation between the number of HFIS and the obstructive apnea-hypopnea index. Children with more than 3 apneas and hypopneas per hour of sleep all made at least 10 HFIS per hour, and all children who had more than 10 HFIS per hour had obstructive apnea-hypopnea index values greater than 1. Children with adenotonsillar hypertrophy made more HFIS than did those children whose tonsils and adenoids had been removed. CONCLUSIONS: HFIS may be a marker of disturbed breathing during sleep in children with adenotonsillar hypertrophy.