Pulseoximetry: sufficient to diagnose severe sleep apnea

Application study of apnea-hypopnea duration for assessing adult obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is a common sleep disordered breathing disorder, which can cause serious damage to multiple human systems. Although polysomnography (PSG) is the current gold standard for diagnosis, it is complex and expensive. Therefore, it is of great significance to find a simple, economical and rapid primary screening and diagnosis method to replace PSG for the diagnosis of OSA.

OBJECTIVE

The purpose of this study is to propose a new method for the diagnosis and classification of OSA, which is used to automatically detect the duration of sleep apnea hypopnea events (AHE), so as to estimate the ratio(S) of the total duration of all-night AHE to the total sleep time only based on the sound signal of sleep respiration, and to identify OSA.

METHODS

We performed PSG tests on participants and extracted relevant sleep breathing sound signal data. This study is carried out in two stages. In the first stage, the relevant PSG report data of eligible subjects were recorded, the total duration of AHE in each subject's data was extracted, and the S value was calculated to evaluate the severity of OSA. In the second stage, only the sleep breath sound signal data of the same batch of subjects were used for automatic detection, and the S value in the sleep breath sound signal was extracted, and the S value was compared with the PSG diagnosis results to calculate the accuracy of the experimental method.

RESULTS

Among 225 subjects. Using PSG as the reference standard, the S value extracted from the PSG diagnostic data report can accurately diagnose OSA(accuracy rate 99.56%) and distinguish its severity (accuracy rate 95.11%). The accuracy of the S value detected in the sleep breathing sound signal in the diagnosis of severe OSA reached 100%.

CONCLUSION

The results show that the experimental parameter S value is feasible in OSA diagnosis and classification. OSA can be identified and evaluated only by sleep breathing sounds. This method helps to simplify the diagnostic grading of traditional OSA and lays a foundation for the subsequent development of simple diagnostic grading equipment.

The impact of study type and sleep measurement on oxygen desaturation index calculation

STUDY OBJECTIVES

The oxygen desaturation index (ODI) is an important measure of sleep-disordered breathing during polysomnography (PSG); however, the AASM Manual (V3) does not specify whether to include oxygen desaturations occurring during wake epochs. Additionally, an ODI obtained from PSG can differ from an ODI using home sleep apnea tests (HSATs) that do not measure sleep, hampering diagnostic and treatment decision reliability. This study aimed to (1) compare an ODI that included all desaturations with an ODI that excluded desaturations occurring during wake epochs in PSG and (2) compare ODIs obtained from PSG with HSAT.

METHODS

100 consecutive PSGs for investigation of obstructive sleep apnea were compared. ODIs were calculated including all desaturations (ODIall) and by excluding desaturations entirely during wake epochs (ODIsleep). Additionally, we compared ODIall with an ODI calculated using monitoring time as the denominator (ODIHSAT).

RESULTS

The median (interquartile range) 3% ODI for ODIall was 22.8 (13.1, 44.1) events/h and ODIsleep was 17.6 (11.5, 35.2) events/h (median difference: -3.9 events/h [-8.2, -0.9]; 21.0% [8.7%, 33.2%]). This discrepancy was larger with increasing ODI and decreasing sleep efficiency. The ODIHSAT was 17.4 (11.3, 35.2) events/h and the median reduction in ODIHSAT vs ODIall was -4.5 (-10.9, -2.0) events/h (21.6%; 11.1%, 33.8).

CONCLUSIONS

ODI was significantly reduced when desaturations in wake epochs were excluded, and when ODI was based on monitoring time rather than sleep time, with the potential for underestimation of disease severity. Results suggest that ODI can differ substantially depending on the calculation and study type used, and that there is a need for standardization to ensure consistent diagnosis and treatment outcomes.

CITATION

Whenn CB, Wilson DL, Ruehland WR, Churchward TJ, Worsnop C, Tolson J. The impact of study type and sleep measurement on oxygen desaturation index calculation. J Clin Sleep Med. 2024;20(5):709-717.

Portable evaluation of obstructive sleep apnea in adults: A systematic review

Obstructive sleep apnea (OSA) is a significant healthcare burden affecting approximately one billion people worldwide. The prevalence of OSA is rising with the ongoing obesity epidemic, a key risk factor for its development. While in-laboratory polysomnography (PSG) is the gold standard for diagnosing OSA, it has significant drawbacks that prevent widespread use. Portable devices with different levels of monitoring are available to allow remote assessment for OSA. To better inform clinical practice and research, this comprehensive systematic review evaluated diagnostic performances, study cost and patients' experience of different levels of portable sleep studies (type 2, 3, and 4), as well as wearable devices and non-contact systems, in adults. Despite varying study designs and devices used, portable diagnostic tests are found to be sufficient for initial screening of patients at risk of OSA. Future studies are needed to evaluate cost effectiveness with the incorporation of portable diagnostic tests into the diagnostic pathway for OSA, as well as their application in patients with chronic respiratory diseases and other comorbidities that may affect test performance.

Performance evaluation of a wrist-worn reflectance pulse oximeter during sleep

OBJECTIVES

To characterize and evaluate the estimation of oxygen saturation measured by a wrist-worn reflectance pulse oximeter during sleep.

METHODS

Ninety-seven adults with sleep disturbances were enrolled. Oxygen saturation was simultaneously measured using a reflectance pulse oximeter (Galaxy Watch 4 [GW4], Samsung, South Korea) and a transmittance pulse oximeter (polysomnography) as a reference. The performance of the device was evaluated using the root mean squared error (RMSE) and coverage rate. Additionally, GW4-derived oxygen desaturation index (ODI) was compared with the apnea-hypopnea index (AHI) derived from polysomnography.

RESULTS

The GW4 had an overall RMSE of 2.3% and negligible bias of -0.2%. A Bland-Altman density plot showed good agreement between the GW4 and the reference pulse oximeter. RMSEs were 1.65 ± 0.57%, 1.76 ± 0.65%, 1.93 ± 0.54%, and 2.93 ± 1.71% for normal (n = 18), mild (n = 21), moderate (n = 23), and severe obstructive sleep apnea (n = 35), respectively. The data rejection rate was 26.5%, which was caused by fluctuations in contact pressure and the discarding of data less than 70% of saturation. A GW4-ODI ≥5/h had the highest ability to predict AHI ≥15/h with sensitivity, specificity, accuracy, and area under the curve of 89.7%, 64.1%, 79.4%, and 0.908, respectively.

CONCLUSIONS

This study evaluated the estimation of oxygen saturation by the GW4 during sleep. This device complies with both Food and Drug Administration and International Organization for Standardization standards. Further improvements in the algorithms of wearable devices are required to obtain more accurate and reliable information about oxygen saturation measurements.

Differentiation Model for Insomnia Disorder and the Respiratory Arousal Threshold Phenotype in Obstructive Sleep Apnea in the Taiwanese Population Based on Oximetry and Anthropometric Features

Insomnia disorder (ID) and obstructive sleep apnea (OSA) with respiratory arousal threshold (ArTH) phenotypes often coexist in patients, presenting similar symptoms. However, the typical diagnosis examinations (in-laboratory polysomnography (lab-PSG) and other alternatives methods may therefore have limited differentiation capacities. Hence, this study established novel models to assist in the classification of ID and low- and high-ArTH OSA. Participants reporting insomnia as their chief complaint were enrolled. Their sleep parameters and body profile were accessed from the lab-PSG database. Based on the definition of low-ArTH OSA and ID, patients were divided into three groups, namely, the ID, low- and high-ArTH OSA groups. Various machine learning approaches, including logistic regression, k-nearest neighbors, naive Bayes, random forest (RF), and support vector machine, were trained using two types of features (Oximetry model, trained with oximetry parameters only; Combined model, trained with oximetry and anthropometric parameters). In the training stage, RF presented the highest cross-validation accuracy in both models compared with the other approaches. In the testing stage, the RF accuracy was 77.53% and 80.06% for the oximetry and combined models, respectively. The established models can be used to differentiate ID, low- and high-ArTH OSA in the population of Taiwan and those with similar craniofacial features.

Predictive performance of oximetry in detecting sleep apnea in surgical patients with cardiovascular risk factors

Introduction

In adults with cardiovascular risk factors undergoing major noncardiac surgery, unrecognized obstructive sleep apnea (OSA) was associated with postoperative cardiovascular complications. There is a need for an easy and accessible home device in predicting sleep apnea. The objective of the study is to determine the predictive performance of the overnight pulse oximetry in predicting OSA in at-risk surgical patients.

Methods

This was a planned post-hoc analysis of multicenter prospective cohort study involving 1,218 at-risk surgical patients without prior diagnosis of sleep apnea. All patients underwent home sleep apnea testing (ApneaLink Plus, ResMed) simultaneously with pulse oximetry (PULSOX-300i, Konica Minolta Sensing, Inc). The predictive performance of the 4% oxygen desaturation index (ODI) versus apnea-hypopnea index (AHI) were determined.

Results

Of 1,218 patients, the mean age was 67.2 ± 9.2 years and body mass index (BMI) was 27.0 ± 5.3 kg/m². The optimal cut-off for predicting moderate-to-severe and severe OSA was ODI ≥15 events/hour. For predicting moderate-to-severe OSA (AHI ≥15), the sensitivity and specificity of ODI ≥ 15 events per hour were 88.4% (95% confidence interval [CI], 85.7–90.6) and 95.4% (95% CI, 94.2–96.4). For severe OSA (AHI ≥30), the sensitivity and specificity were 97.2% (95% CI, 92.7–99.1) and 78.8% (95% CI, 78.2–79.0). The area under the curve (AUC) for moderate-to-severe and severe OSA was 0.983 (95% CI, 0.977–0.988) and 0.979 (95% CI, 0.97–0.909) respectively.

Discussion

ODI from oximetry is sensitive and specific in predicting moderate-to-severe or severe OSA in at-risk surgical population. It provides an easy, accurate, and accessible tool for at-risk surgical patients with suspected OSA.

Associations between sleep apnea and advanced brain aging in a large-scale population study

Advanced brain aging is commonly regarded as a risk factor for neurodegenerative diseases, for example, Alzheimer's dementia, and it was suggested that sleep disorders such as obstructive sleep apnea (OSA) are significantly contributing factors to these neurodegenerative processes. To determine the association between OSA and advanced brain aging, we investigated the specific effect of two indices quantifying OSA, namely the apnea-hypopnea index (AHI) and the oxygen desaturation index (ODI), on brain age, a score quantifying age-related brain patterns in 169 brain regions, using magnetic resonance imaging and overnight polysomnography data from 690 participants (48.8% women, mean age 52.5 ± 13.4 years) of the Study of Health in Pomerania. We additionally investigated the mediating effect of subclinical inflammation parameters on these associations via a causal mediation analysis. AHI and ODI were both positively associated with brain age (AHI std. effect [95% CI]: 0.07 [0.03; 0.12], p-value: 0.002; ODI std. effect [95% CI]: 0.09 [0.04; 0.13], p-value: < 0.0003). The effects remained stable in the presence of various confounders such as diabetes and were partially mediated by the white blood cell count, indicating a subclinical inflammation process. Our results reveal an association between OSA and brain age, indicating subtle but widespread age-related changes in regional brain structures, in one of the largest general population studies to date, warranting further examination of OSA in the prevention of neurodegenerative diseases.

Wavelet Analysis of Overnight Airflow to Detect Obstructive Sleep Apnea in Children

This study focused on the automatic analysis of the airflow signal (AF) to aid in the diagnosis of pediatric obstructive sleep apnea (OSA). Thus, our aims were: (i) to characterize the overnight AF characteristics using discrete wavelet transform (DWT) approach, (ii) to evaluate its diagnostic utility, and (iii) to assess its complementarity with the 3% oxygen desaturation index (ODI3). In order to reach these goals, we analyzed 946 overnight pediatric AF recordings in three stages: (i) DWT-derived feature extraction, (ii) feature selection, and (iii) pattern recognition. AF recordings from OSA patients showed both lower detail coefficients and decreased activity associated with the normal breathing band. Wavelet analysis also revealed that OSA disturbed the frequency and energy distribution of the AF signal, increasing its irregularity. Moreover, the information obtained from the wavelet analysis was complementary to ODI3. In this regard, the combination of both wavelet information and ODI3 achieved high diagnostic accuracy using the common OSA-positive cutoffs: 77.97%, 81.91%, and 90.99% (AdaBoost.M2), and 81.96%, 82.14%, and 90.69% (Bayesian multi-layer perceptron) for 1, 5, and 10 apneic events/hour, respectively. Hence, these findings suggest that DWT properly characterizes OSA-related severity as embedded in nocturnal AF, and could simplify the diagnosis of pediatric OSA.

Increased heart rate with sleep disordered breathing in hypertrophic cardiomyopathy

BACKGROUND

Current guidelines recommend medications with rate control properties for symptomatic patients with hypertrophic cardiomyopathy (HCM) based on the rationale that lowering heart rate (HR) improves their symptoms. Whether sleep disordered breathing (SDB) is associated with increased HR in HCM patients is not known.

METHOD

We diagnosed uncontrolled SDB (oxygen desaturation index ≥5) in consecutive echocardiographically confirmed HCM patients seen at Mayo Clinic, Rochester, and analyzed their HR as recorded by a 24-h Holter monitor. We compared mean, minimum, maximum HR between those with vs without SDB. In a pilot subanalysis of HCM patients with SDB who also underwent subsequent diagnostic polysomnography (PSG), we analyzed RR interval changes coinciding with obstructive sleep apnea and hypopnea episodes.

RESULTS

Of the 230 HCM patients included in this study (age 54 ± 16 years; 138 male; LVOT pressure gradient at rest 45 ± 39 mmHg), 115 (50%) patients had SDB. HCM patients with SDB were recorded to have higher mean HR (71 vs. 67 bpm; p = .002, adjusted p = .001), and this difference was most pronounced during night hours of 10 PM to 5 AM (61 vs. 67 bpm; p < .001). In the pilot analysis of the available PSG data, the release of obstructive sleep apneas and hypopneas coincided with fluctuation of HR.

CONCLUSIONS

SDB is independently associated with higher mean HR in patients with HCM, and this difference is most significant during sleep. Treatment of SDB, which is readily available, should be tested as a complementary modality to the currently recommended pharmacotherapy aimed at lowering HR in patients with symptomatic HCM.

Bispectral analysis of overnight airflow to improve the pediatric sleep apnea diagnosis

Pediatric Obstructive Sleep Apnea (OSA) is a respiratory disease whose diagnosis is performed through overnight polysomnography (PSG). Since it is a complex, time-consuming, expensive, and labor-intensive test, simpler alternatives are being intensively sought. In this study, bispectral analysis of overnight airflow (AF) signal is proposed as a potential approach to replace PSG when indicated. Thus, our objective was to characterize AF through bispectrum, and assess its performance to diagnose pediatric OSA. This characterization was conducted using 13 bispectral features from 946 AF signals. The oxygen desaturation index ≥3% (ODI3), a common clinical measure of OSA severity, was also obtained to evaluate its complementarity to the AF bispectral analysis. The fast correlation-based filter (FCBF) and a multi-layer perceptron (MLP) were used for subsequent automatic feature selection and pattern recognition stages. FCBF selected 3 bispectral features and ODI3, which were used to train a MLP model with ability to estimate apnea-hypopnea index (AHI). The model reached 82.16%, 82.49%, and 90.15% accuracies for the common AHI cut-offs 1, 5, and 10 events/h, respectively. The different bispectral approaches used to characterize AF in children provided complementary information. Accordingly, bispectral analysis showed that the occurrence of apneic events decreases the non-gaussianity and non-linear interaction of the AF harmonic components, as well as the regularity of the respiratory patterns. Moreover, the bispectral information from AF also showed complementarity with ODI3. Our findings suggest that AF bispectral analysis may serve as a useful tool to simplify the diagnosis of pediatric OSA, particularly for children with moderate-to-severe OSA.

Validation of Oximetry for Diagnosing Obstructive Sleep Apnea in a Clinical Setting

A large epidemiological study using oximetry to analyze obstructive sleep apnea (OSA) and metabolic comorbidities was performed in Japan; however, reliability and validity of oximetry in the Japanese population remains poorly understood. In this study, oximetry data from the epidemiological study were compared with data from clinically performed polysomnography (PSG) and out-of-center sleep testing (OCST) in epidemiological study participants who later attended our outpatient units. The oxygen desaturation index (ODI) from oximetry showed a moderate positive relationship (correlation coefficient r = 0.561, p < 0.001) with apnea/hypopnea data from PSG/OCST. The area under the receiver operating characteristic curve showed moderate accuracy of this method in the detection of moderate-to-severe or severe OSA. However, the optimal ODI thresholds to detect moderate-to-severe OSA and severe OSA were the same (ODI > 20.1). Oximetry may be a useful tool for screening moderate-to-severe or severe sleep apnea. However, it may be difficult to set an appropriate threshold to distinguish between moderate and severe sleep apnea by oximetry alone.

Application of automatic detection based on overnight airflow and blood oxygen in patients with sleep disordered breathing

PURPOSE

To explore the feasibility of automatic detection based on air flow and blood oxygen in patients with sleep disordered breathing.

METHODS

This study proposes a new automated detection method for sleep disordered breathing based on overnight airflow and blood oxygen saturation (SaO₂). In this regard, local range (LR) of the airflow was adopted to detect apnea events and the SaO₂ sudden drops were used to help determine hypopnea events. Pearson correlation index was used to evaluate the relationship between the two automated methods (this study vs. Remlogic software) and the manual reports. Error and mean absolute error (MAE) were used to assess the two automated methods.

RESULTS

For all patients, the apnea-hypopnea index (AHI), apnea index (AI) and hypopnea index (HI) for our automated scoring and manual reports were highly correlated (the Pearson correlation index were 0.996, 0.995 and 0.928, respectively, P < 0.001). However, HI for Remlogic automated scoring and clinical manual reports was poorly correlated (r = 0.316, P < 0.001). Compared with the manual reports, mean absolute error of AHI, AI and HI between the two automated methods (this study vs. Remlogic software) were statistically significant (P < 0.0001). Furthermore, among the three subgroups (group 1, AHI < 15/h, group 2, 15/h ≤ AHI < 30/h and group 3, AHI ≥ 30/h), the mean error and MAE of AHI between the two automated methods were also statistically significant (P < 0.01).

CONCLUSIONS

Generally, good agreements were shown between our automated detection and clinical reports. This procedure is robust and effective, which would significantly shorten the analysis time.

Artificial neural network analysis of the oxygen saturation signal enables accurate diagnostics of sleep apnea

The severity of obstructive sleep apnea (OSA) is classified using apnea-hypopnea index (AHI). Accurate determination of AHI currently requires manual analysis and complicated registration setup making it expensive and labor intensive. Partially for these reasons, OSA is a heavily underdiagnosed disease as only 7% of women and 18% of men suffering from OSA have diagnosis. To resolve these issues, we introduce an artificial neural network (ANN) that estimates AHI and oxygen desaturation index (ODI) using only the blood oxygen saturation signal (SpO2), recorded during ambulatory polygraphy, as an input. Therefore, hypopneas associated only with an arousal were not considered in this study. SpO2 signals from 1692 patients were used for training and 99 for validation. Two test sets were used consisting of 198 and 1959 patients. In the primary test set, the median absolute errors of ANN estimated AHI and ODI were 0.78 events/hour and 0.68 events/hour respectively. Based on the ANN estimated AHI and ODI, 90.9% and 94.4% of the test patients were classified into the correct OSA severity category. In conclusion, AHI and ODI can be reliably determined using neural network analysis of SpO2 signal. The developed method may enable a more affordable screening of OSA.

REM sleep in naps differentially relates to memory consolidation in typical preschoolers and children with Down syndrome

Sleep is recognized as a physiological state associated with learning, with studies showing that knowledge acquisition improves with naps. Little work has examined sleep-dependent learning in people with developmental disorders, for whom sleep quality is often impaired. We examined the effect of natural, in-home naps on word learning in typical young children and children with Down syndrome (DS). Despite similar immediate memory retention, naps benefitted memory performance in typical children but hindered performance in children with DS, who retained less when tested after a nap, but were more accurate after a wake interval. These effects of napping persisted 24 h later in both groups, even after an intervening overnight period of sleep. During naps in typical children, memory retention for object-label associations correlated positively with percent of time in rapid eye movement (REM) sleep. However, in children with DS, a population with reduced REM, learning was impaired, but only after the nap. This finding shows that a nap can increase memory loss in a subpopulation, highlighting that naps are not universally beneficial. Further, in healthy preschooler's naps, processes in REM sleep may benefit learning.

Evaluation of behavioral change after adenotonsillectomy for obstructive sleep apnea in children with autism spectrum disorder

BACKGROUND AND OBJECTIVE

Obstructive sleep apnea (OSA) may affect daily cognitive functioning in children. The aims of our study were two-fold. The first aim was to detect, using the Child Behavior Checklist (CBCL), whether adenotonsillectomy (AT) for the treatment of OSA improved the behavior of children with autism spectrum disorder (ASD). The second aim was to identify characteristics for behavioral improvement following the treatment of OSA in these children with ASD.

METHODS

The behaviors of ASD children aged 5-14 years diagnosed as having OSA (n=30) were evaluated using CBCL before and after AT. CBCL evaluation of ASD children without OSA at two time points with the same interval served as a control (n=24). We statistically examined the two groups. In addition, we conducted a paired t-test to assess changes in CBCL Tscores between the improved group and unchanged/deteriorated group to identify characteristics that may affect behavioral changes following OSA treatment.

RESULTS

After AT, T-scores of the CBCL scales were significantly improved in the OSA group, but no change was observed in the control. A paired t-test revealed that the improved group had significantly higher scores on the CBCL pre-AT than the unchanged/deteriorated group in ASD children with OSA after OSA treatment.

CONCLUSIONS

Behavioral problems were significantly improved following AT in ASD children with OSA. Early detection and treatment of children with OSA is essential to prevent behavioral problems and to support mental development.

Patient response to sleep apnea screening in a dental practice

OBJECTIVE

This study investigated patient response to a recommendation for physician evaluation following screening for obstructive sleep apnea (OSA) in a dental practice.

METHODS

In a community-based dental practice in Raleigh, North Carolina, 119 patients were recruited by nonprobability purposive sampling and administered both a validated subjective (STOP questionnaire) and objective (pulse oximeter) screening instrument for OSA. Patients who screened high-risk for OSA on either instrument were recommended to consult their physician within three months. All patients were contacted via telephone after three months to determine if they had consulted a physician regarding their screening results. Multivariate log-binomial models estimated prevalence ratios (PR) and 95 percent confidence limits (95% CL) for physician consultation according to OSA risk, adjusting for potential confounders.

RESULTS

Overall, 18.5 percent of patients screened high-risk on the STOP questionnaire alone, 26.1 percent on pulse oximetry alone, and 31.9 percent on both instruments. Follow-up of 111 subjects (93.3%) found that 40 (47.1%) of those high-risk for OSA on one or both instruments sought physician evaluation. Patients who screened high-risk on pulse oximetry were 2.55 times as likely to seek physician evaluation compared with those who screened low-risk on both instruments (PR = 2.55, 95% CL: 1.02, 6.37). Screening high-risk on the STOP questionnaire did not significantly increase the likelihood of physician evaluation.

CONCLUSIONS

Nearly, half of dental patients who screen high-risk for OSA may be responsive to a recommendation to seek physician evaluation.

Sleep-disordered breathing following mandibular setback: a systematic review of the literature

INTRODUCTION

A mandibular setback reduces space in the pharyngeal airway, and it has been suggested that it might induce sleep-disordered breathing.

OBJECTIVES

An evidence-based literature review was conducted to identify the effect of mandibular setback on the respiratory function during sleep.

METHODS

The authors performed a systematic review of pertinent literature published up to 2014. A structured search of literature was performed, with predefined criteria. A survey of the PubMed, ScienceDirect, and Cochrane database was performed. A manual search of oral and maxillofacial surgery-related journals was accomplished. Potentially relevant studies then had their full-text publication reviewed.

RESULTS

A total of 1,780 publications were evaluated, through which nine papers (seven case series and two case-control studies) were selected for the final review. No evidence of sleep disorder after six months was related in 223 patients. In one study, two patients developed obstructive sleep apnea syndrome after surgery, and in another two studies, seven patients presented an increase of obstructive apneas/hypopneas events and oxygen desaturation index. Most of the patients analyzed were young and thin.

CONCLUSION

There was no evidence of postoperative sleep apnea syndrome after a mandibular setback surgery. However, one should always consider a potential reduction of the upper airway space during the treatment plan. Obese patients and those submitted to large amounts of mandibular setbacks present a higher chance to develop obstructive sleep apnea syndrome.

Decreased exercise capacity and sleep-disordered breathing in patients with hypertrophic cardiomyopathy

BACKGROUND

Mechanisms of decreased exercise capacity in patients with hypertrophic cardiomyopathy (HCM) are not well understood. Sleep-disordered breathing (SDB) is a highly prevalent but treatable disorder in patients with HCM. The role of comorbid SDB in the attenuated exercise capacity in HCM has not been studied previously.

METHODS

Overnight oximetry, cardiopulmonary exercise testing, and echocardiographic studies were performed in consecutive patients with HCM seen at the Mayo Clinic. SDB was considered present if the oxygen desaturation index (number of ≥ 4% desaturations/h) was ≥ 10. Peak oxygen consumption (VO2 peak) (the most reproducible and prognostic measure of cardiovascular fitness) was then correlated with the presence and severity of SDB.

RESULTS

A total of 198 patients with HCM were studied (age, 53 ± 16 years; 122 men), of whom 32% met the criteria for the SDB diagnosis. Patients with SDB had decreased VO2 peak compared with those without SDB (16 mL O2/kg/min vs 21 mL O2/kg/min, P < .001). SDB remained significantly associated with VO2 peak after accounting for confounding clinical variables (P < .001) including age, sex, BMI, atrial fibrillation, and coronary artery disease.

CONCLUSIONS

In patients with HCM, the presence of SDB is associated with decreased VO2 peak. SDB may represent an important and potentially modifiable contributor to impaired exercise tolerance in this unique population.

Reviewing the Systematic Reviews in OSA Surgery

Objective

There is an extensive amount of literature on surgeries as treatment for obstructive sleep apnea syndrome on adults. Previous systematic reviews have been performed to summarize the outcomes for sleep surgeries, with conflicting results. The objective of this study was to critically evaluate these systematic reviews to provide an overview of their quality, strengths, and conclusions.

Data Sources

MEDLINE, Scopus, and the Cochrane Collaboration databases were searched from inception to April 2013.

Review Methods

An overview of systematic reviews was undertaken. Studies included in this review are the systematic reviews whose primary objective was to evaluate the outcomes of sleep apnea surgery on adults. The methodological quality of the studies was analyzed with AMSTAR checklist, and the quality of evidence was evaluated using the GRADE assessment tool. Primary outcome measures assessed the effect of surgery on snoring, sleepiness, and the apnea-hypopnea index.

Results

A total of 11 studies were included in this study, and the pooled overview includes 378 studies. The systematic reviews were mostly graded as low quality using the GRADE tool and low to moderate according to the AMSTAR checklist. Outcome for apnea-hypopnea index demonstrated substantial variation leading to conflicting results. Despite a high amount of heterogeneity, outcomes for sleepiness and snoring demonstrated significant improvement across included reviews.

Conclusions

Although obstructive sleep apnea surgery is associated with improved outcomes in most studies, the level and quality of evidence reviews requires improvement.

Case-control studies of novel hemoglobin anomalies as differential diagnosis in sleep apnea syndrome

PURPOSE

Pulse oximetry plays an essential role in the diagnosis of sleep apnea syndrome. We discovered two novel hemoglobin anomalies, Hb Bonn and Hb Venusberg, which initially resulted in avoidable sleep disorder examinations and therapeutic consequences due to their low oxygen saturation levels as measured by pulse oximetry.

METHODS

Hematological as well as clinical chemical diagnosis was carried out. Hemoglobin anomalies were detected through electrophoresis, chromatography, spectrophotometry, and pulse oximetry as well as hemoglobin gene sequencing.

RESULTS

Hb Bonn is a novel hemoglobin mutation of the proximal α1 globin with an additional absorption maximum of the oxyhemoglobin at 668 nm. This results in pulse oximetry measurements of false low oxygen saturation due to incorrect calculations at the pulse oximetry measuring point 660 m. Hb Venusberg is a novel oxygen-affine hemoglobin mutation of the β-globin which is electrophoretically silent. Clinical symptoms include intermittent low oxygen saturation levels, cyanosis of lips and nail beds, and limited physical resistance to stress.

CONCLUSIONS

Hemoglobin anomalies, such as Hb Bonn and Hb Venusberg, should be included in differential diagnosis as potential causes of low oxygen saturation especially in case of nonspecific or conflicting findings.

Effects of obstructive sleep apnea on serum brain-derived neurotrophic factor protein, cortisol, and lipid levels

OBJECTIVES

Obstructive sleep apnea (OSA) is a sleep-disordered breathing leading to vascular endothelial cells dysfunction, cognitive impairment, and abnormal lipid metabolism. serum brain-derived neurotrophic factor (BDNF) protein, cortisol, and lipid levels in OSA were investigated.

MATERIALS AND METHODS

All middle-aged subjects including healthy individuals without signs and symptoms of apnea-hypopnea and ear nose throat (ENT) outpatients were randomly recruited and screened by overnight polysomnogram (PSG). Apnea-hypopnea index (AHI) was used as a criteria to determine subjects to enroll in this program. According to AHI, they were separated into control and OSA groups. A group of 39 OSA patients (AHI ≥ 10 events/h) and 24 control subjects (AHI < 5 events/h) were selected. Serum BDNF protein was analyzed by enzyme-linked immunosorbent assay (ELISA) from venous blood collection at 8:00 a.m. following PSG. Serum cortisol was assayed by enzyme-chemiluminescense immuno assay (ECLIA). Serum lipid profile levels were determined by enzymatic colorimetric and homogeneous method.

RESULTS

Characteristics of OSA patients and control groups including gender, age, AHI, body weight, height, and BMI showed significant differences. Serum BDNF protein, cortisol, triglyceride, and total cholesterol levels in OSA and control groups were not significantly different. High density lipoprotein-cholesterol (HDL-c) in OSA was significantly lower than that of control (p = 0.008) while low density lipoprotein-cholesterol (LDL-c) was significantly higher than that of control (p = 0.04).

CONCLUSIONS

OSA had no significant effect on serum BDNF, cortisol, triglyceride, or total cholesterol levels while LDL-c and HDL-c levels in OSA patients compared to control were significantly different at p = 0.04, and p = 0.008, respectively.

Interactions between sleep disordered breathing and atrial fibrillation in patients with hypertrophic cardiomyopathy

The aim of this study was to investigate whether patients with hypertrophic cardiomyopathy (HC) and sleep disordered breathing (SDB) have a higher prevalence of atrial fibrillation (AF) compared to patients with HC without SDB. HC is associated with a high prevalence of AF that contributes to increased morbidity and mortality. SDB is strongly associated with a higher incidence, prevalence, and recurrence of AF in patients without HC. Whether this association also applies to patients with HC is not known. Overnight oximetry was prospectively performed on 91 consecutive patients with echocardiographically confirmed HC. The presence or absence of AF in this population was correlated with the oximetric findings. SDB was associated with a higher prevalence of AF (40% vs 11%, p = 0.005). In addition, SDB was accompanied by significantly increased left atrial volume index (58 +/- 19 vs 42 +/- 13 ml/m(2), p = 0.0002). Increasing severity of SDB was correlated with higher AF prevalence and with increase in left atrial volume index. These associations remained significant even after accounting for potential confounders in a multivariate analysis. In conclusion, these findings suggest that the presence and severity of SDB may influence left atrial volume index and the prevalence of AF in patients with HC. SDB may therefore be an important and potentially modifiable cause of morbidity and mortality in this population.

Undiagnosed sleep-related breathing disorders are associated with focal brainstem atrophy in the elderly

BACKGROUND

Sleep-related breathing disorders (SRBDs) affect as many as 40% of elderly people. The association of SRBDs with structural brain abnormalities remains unclear. In this observational study, we evaluated gray matter changes in the brain associated with sleep abnormalities in volunteers and their relationship with the severity of SRBDs.

METHODS

One hundred fifty two healthy subjects aged 66.0 +/- 0.6 years-old underwent tridimensional brain MRI and nocturnal polygraphic recording during which apnea/hypopnea index (AHI) and the oxyhemoglobin desaturation index (ODI) were measured. Using voxel-based morphometry, we investigated the presence of gray matter abnormalities in association with AHI and ODI.

FINDINGS

Seventy-six subjects (50%) had SRBDs defined by an AHI > or = to 15 and 25 subjects (16%) SRBDs defined by an ODI > or = 15, in the absence of systematic excessive daytime sleepiness. A significant symmetrical loss of gray matter in the intermediate reticular zone of the bulbopontine area was found to correlate with both AHI and ODI (P < 0.05 corrected for multiple comparisons for cluster significance).

INTERPRETATION

This gray matter volume decrease in brain regions involved in breathing/autonomic functions, as well as their correlation with the severity of the disorder, suggests a pathophysiological link between structural changes and SRBDs.

Pulse oximetric thresholds for tonsillectomy and adenotomy in children: significance of 1-2% decline in oxyhemoglobin saturation

OBJECTIVES

We aimed to establish optimal overnight pulse oximetric thresholds for determining the indication of tonsillectomy and adenotomy (TA) in children by revising the definition of 'desaturation'.

METHODS

One hundred and thirty four children scheduled for TA (TA group, 5.3 +/- 1.4 years old) and 112 otherwise healthy children scheduled for elective minor surgery (control group, 5.4 +/- 1.5 years old) were enrolled into this prospective study. Data were recorded and stored every 10 s using Nellcor N-395. Desaturation/resaturation events were defined as x% change (x = 1-4) of SpO2 (oxyhemoglobin saturation by pulse oximetry) in 10 s. The desaturation/resaturation indices were calculated as events per hour of total sleeping time. For each index, a wide range of temporary thresholds was set. The optimal thresholds for TA were the ones that maximized the weighted average for sensitivity, specificity (based on whether the index improved or not after TA), and the percentage of the control children whose indices were below the threshold.

RESULTS

For all the indices, the optimal thresholds that fulfilled the above condition were determined. Compared with the x = 3-4% results, the application of x = 1-2% approximately doubled the TA patients whose preoperative 'positive' indices improved after TA, with the weighted averages of 84.3-92.3% as described above.

CONCLUSIONS

By defining desaturation/resaturation as a 1-2% change in SpO2 from the preceding value, children with adenotonsillar hypertrophy whose pulse oximetric indices are expected to improve after TA can be detected by pulse oximetry with relatively high sensitivity and specificity.

Multimodal detection of sleep apnoea using electrocardiogram and oximetry signals

A method for the detection of sleep apnoea, suitable for use in the home environment, is presented. The method automatically analyses night-time electrocardiogram (ECG) and oximetry recordings and identifies periods of normal and sleep-disordered breathing (SDB). The SDB is classified into one of six classes: obstructive, mixed and central apnoeas, and obstructive, mixed and central hypopnoeas. It also provides an estimated apnoea, hypopnoea and apnoea-hypopnoea index. The basis of the method is a pattern recognition system that identifies episodes of apnoea by analysing the heart variability, an ECG-derived respiration signal and blood oximetry values. The method has been tested on 183 subjects with a range of apnoea severities who have undergone a full overnight polysomnogram study. The results show that the method separates control subjects from subjects with clinically significant sleep apnoea with a specificity of 83 per cent and sensitivity of 95 per cent. These results demonstrate that home-based screening for sleep apnoea is a viable alternative to hospital-based tests with the added benefit of low cost and minimal waiting times.

Validation of the WristOx 3100 oximeter for the diagnosis of sleep apnea/hypopnea syndrome

OBJECTIVE

To evaluate the diagnostic accuracy of the Nonin WristOx 3100 and its software (nVision 5.0) in patients with suspicion of sleep apnea/hypopnea syndrome (SAHS).

METHODS

All participants (168) had the oximetry and polysomnography simultaneously. The two recordings were interpreted blindly. The software calculated: adjusted O(2) desaturation index [ADI]-mean number of O(2) desaturation per hour of total recording analyzed time of > or = 2%, 3%, 4%, 5%, and 6% (ADI2, 3, 4, 5, and 6) and AT90-accumulated time at SO(2) < 90%. The ADI2, 3, 4, 5, and 6 and the AT90 cutoff points that better discriminated between subjects with or without SAHS arose from the receiver operating characteristic curve analysis. The sensitivity (S), specificity (E), and positive and negative likelihood ratio (LR+, LR-) for the different thresholds for ADI were calculated.

RESULTS

One hundred and fifty-four patients were included (119 men, mean age 51, median apnea/hypopnea index [AHI] 14, median body mass index [BMI] 28.3 kg/m(2)). The best cutoff points of ADI were: SAHS = AHI > or = 5: ADI2 > 19.3 (S 89%, E 94%, LR+ 15.5 LR- 0.11); SAHS =AHI > or = 10: ADI3 > 10.5 (S 88%, E 94%, LR+ 15 LR- 0.12); SAHS = AHI > or = 15: ADI3 > 13.4 (S 88%, E 90%, LR+ 8.9, LR- 0.14). AT90 had the lowest diagnosis accuracy. An ADI2 < or = 12.2 excluded SAHS (AHI > or = 5 and 10; S 100%, LR- 0) and ADI3 > 4.3 (AHI > or = 5 and 10) or 32 (AHI > or = 15) confirmed SAHS (E 100%).

CONCLUSIONS

A negative oximetry defined as ADI2 < or = 12.2 excluded SAHS defined as AHI > or = 5 or 10 with a sensitivity and negative likelihood ratio of 100% and 0%, respectively. Furthermore, a positive oximetry defined as an ADI3 > 32 (SAHS = AHI > or = 15) had a specificity of 100% to confirm the pathology.

Plasma thioredoxin, a novel oxidative stress marker, in patients with obstructive sleep apnea before and after nasal continuous positive airway pressure

Obstructive sleep apnea (OSA) is associated with increased cardiovascular mortality, and oxidative stress was suggested to play an important role. We hypothesized that the plasma TRX level, a novel oxidative stress marker, is elevated in OSA patients. Plasma TRX and adiponectin levels, which are significantly associated with cardiovascular mortality, were measured in 41 patients with severe OSA before (n = 41) and after (n = 27) nasal continuous positive airway pressure therapy (nCPAP) for 1 month and in 12 subjects without OSA (non-OSA group). The TRX level was significantly higher (p = 0.02) and the adiponectin level was significantly lower (p = 0.02) in the OSA group than in the non-OSA group. After 1 month of nCPAP (n = 27), the TRX level significantly decreased (p = 0.03), and the adiponectin level significantly increased (p = 0.03). Among the 14 patients with untreated OSA, the TRX and adiponectin levels did not significantly change over a 1-month interval. Among the 53 (41 OSA + 12 non-OSA) subjects, the TRX level was positively correlated with the respiratory disturbance index (p = 0.001) and percentage of time with SaO(2) <90% (p = 0.0002). The adiponectin level, but not the TRX level, was correlated with the BMI (n = 53; p = 0.02). Plasma TRX may be a unique marker for evaluating oxidative stress and monitoring the effectiveness of nCPAP in OSA patients.

Automated detection of obstructive apnea and hypopnea events from oxygen saturation signal

Our objective is to automate the detection of apnea and hypopnea events in obstructive sleep apnea hypopnea (OSAH) syndrome based on analysis of arterial oxygen saturation signal alone. This is the first attempt where wavelet is used to detect OSAH events. Detection of OSAH events through wavelet depends on the fluctuations in the magnitude of the transformed coefficients, thus circumventing the problem of variability in the criteria on the magnitude and duration of the signal. Our work evaluates the performance of the wavelet transform to detect OSAH events against three conventional amplitude and duration algorithms. High performance in the detection of OSAH events can be achieved through the wavelet algorithm (score 96.55%, sensitivity 95.74% and specificity 97.02%) if the threshold on wavelet coefficients is individually tuned for each study. However, this is impossible in clinical practice. It is interesting to observe that the conventional methods based on amplitude and duration are able to attain a performance as close as this. The Nervus algorithm obtains the best result (score 96.66%, sensitivity 95.26% and specificity 97.46%) compared to the amplitude duration algorithm, the drop duration algorithm and the wavelet algorithm with global threshold, in descending order of performance.

Effect of amplitude criteria on operating characteristic of detection for OSAH events with oxygen saturation

Effect of amplitude criteria on the operating characteristics of algorithms for detecting OSAH events based on the analysis of oxygen saturation alone is investigated. The objective is to establish that there exists an oxygen desaturation level that leverages these algorithms to be more sensitive or more specific, irrespective of the differences in detection mechanism and database, a first ever attempt. Linear classification of algorithms from previous studies discovered that a drop in oxygen saturation of 3% or less makes the detection algorithms more sensitive while a drop of 4% or more makes it more specific. Results from two algorithms developed here also supported this. This finding explains the contradiction cited in the performance of algorithms from the different authors, which casts doubts on their detection ability. It could lead to the establishment of standard oxygen desaturation levels for screening and diagnosis of moderate/severe OSA, thus providing a more credible comparison basis for automated detection algorithms or even clinical tests.

Choice of Oximeter Affects Apnea-Hypopnea Index

STUDY OBJECTIVES

Current Medicare guidelines include an apnea-hypopnea index (AHI) > or = 15 events per hour, in which all hypopneas must be associated with 4% desaturation, to qualify for reimbursement for therapy with continuous positive airway pressure (CPAP). The present data demonstrate the effect of pulse oximeter differences on AHI.

DESIGN

Prospective study, blinded analysis.

SETTING

Academic sleep disorder center.

PATIENTS

One hundred thirteen consecutive patients (84 men and 29 women) undergoing diagnostic sleep studies and being evaluated for CPAP based on the Medicare indications for reimbursement.

INTERVENTIONS

Patients had two of four commonly used oximeters with signal averaging times of 4 to 6 s placed on different digits of the same hand during nocturnal polysomnography.

MEASUREMENTS AND RESULTS

Apneas and candidate hypopneas (amplitude reduction, > 30%) were scored from the nasal cannula airflow signal without reference to oximetry. Candidate hypopneas then were reclassified as hypopneas by each oximeter if they were associated with a 4% desaturation. Although the use of three oximeters resulted in a similar AHI (bias, < 1 event per hour), the fourth oximeter showed an overall increase in AHI of 3.7 events per hour. This caused 7 of 113 patients to have an AHI of > or = 15 events per hour (meeting the Medicare criteria for treatment) by one oximeter but not when a different oximeter was used. More importantly, when our analysis was limited to those patients whose number of candidate hypopneas made them susceptible to the threshold value of 15 events per hour, 7 of 35 patients who did not meet the Medicare AHI standard for treatment by one oximeter were reclassified when a different oximeter was used.

CONCLUSION

In the present study, oximeter choice affected whether the AHI reached the critical cutoff of 15 events per hour, particularly in those with disease severity that was neither very mild nor very severe. As oximetry is not a technique that produces a generic result, there are significant limitations to basing the definition of hypopnea on a fixed percentage of desaturation in determining the eligibility for CPAP therapy.

Clinical significance of pulse rate rise during sleep as a screening marker for the assessment of sleep fragmentation in sleep-disordered breathing

OBJECTIVE

To assess the clinical utility of the frequencies of transient increases of pulse rate, non-invasively measured with a pulseoximeter, as an indirect indication of the degree of cortical arousal, measured conventionally on an electroencephalogram (EEG), in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients.

PATIENTS AND METHODS

Thirty-three consecutive patients referred with suspected OSAHS were studied. Polysomnography (PSG) with determination of esophageal pressure (Pes) and pulseoximetry was monitored to identify breathing-related EEG arousal (B-Ar) associated with apnea, hypopnea or respiratory effort and the frequencies of pulse rate increases. We also assessed the association of B-ArI (defined as the number of B-Ar per hour) with the pulse rate rise index (PRRI)-X(X=4-10) (defined as the number of pulse rate increases per hour). In addition, the sensitivity and specificity of PRRI for the assessment of a B-ArI cutoff point of 30 were calculated.

RESULTS

The sensitivity and specificity of pulseoximetry for different thresholds of PRRI-X(X=4-10) demonstrated that the greatest diagnostic accuracy for detecting frequent arousal (B-ArI > or =30) occurs at a cutoff point of 40 PRRI-6 with a sensitivity of 0.88 and specificity of 0.86. This point shows a significant area under the curve of 0.84. In addition, a statistically significant correlation between PRRI-6 and B-ArI (r=0.68, P<0.0001) was observed.

CONCLUSIONS

The transient increases in pulse rate measured by pulseoximetry during sleep may be a useful clinical marker for predicting the degree of arousal in OSAHS patients, and may, in addition, prevent cases with frequent respiratory effort related arousals from being overlooked. However, further studies are required to improve the confidence level of the PRRI and to investigate the causes of overestimation of EEG arousals.