A cost-effectiveness analysis of alternative at-home or in-laboratory technologies for the diagnosis of obstructive sleep apnea syndrome

Audio source separation to reduce sleeping partner sounds: a simulation study

Objective.When recording a subject in an at-home environment for sleep evaluation or for other breathing disorder diagnoses using non-contact microphones, the breathing recordings (audio signals) can be distorted by sounds such as TV, outside noise, or air-conditioners. If two people are sleeping together, both may produce breathing/snoring sounds that need to be separated. In this study, we present signal processing and source separation algorithms for the enhancement of individual breathing/snoring audio signals in a simulated environment.Approach.We developed a computer simulation of mixed signals derived from genuine nocturnal recordings of 110 subjects. Two main source separation approaches were tested: (1) changing the basis vectors for the mixtures in the time domain (principal and independent component analysis, PCA/ICA) and (2) converting the mixtures to their time-frequency representations (degenerate un-mixing estimation technique, DUET). In addition to these source separation techniques, a beamforming approach was tested.Main results.The separation results with a reverberation time of 0.15 s and zero SNR between signals showed good performance (mean source to interference ratio (SIR): DUET = 12.831 dB, ICA = 3.388 dB, PCA = 4.452 dB), and for beamforming (SIR = -0.304 dB). To evaluate our source separation results, we propose two new measures: an evaluation measure based on a spectral similarity score (mel-SID) between the target source and its estimation (after separation) and a breathing energy ratio measure (BER). The results with the new proposed measures yielded comparable conclusions (mel-SID: DUET = 1.320, ICA = 2.732, PCA = 1.927, and beamforming = 2.590, BER: DUET = 10.241 dB, ICA = 0.270 dB, PCA = -2.847 dB, and beamforming = -1.151 dB), but better differentiated the differences between the performance of the algorithms. The DUET is superior on all measures. Its main advantage is that it only uses two microphones for separation.Significance. The separated audio signal can thus contribute to a more informed diagnosis of sleep-related and non-sleep-related diseases. The Institutional Review Committee of Soroka University Medical Center approved this study protocol (protocol number 10141) and all methods were performed in accordance with the relevant guidelines and regulations.

Economic evaluation of diagnostic sleep studies for obstructive sleep apnoea: a systematic review protocol

BACKGROUND

Obstructive sleep apnoea (OSA) is a significant public health problem affecting a large proportion of the population and is associated with adverse health consequences and a substantial economic burden. Despite the existence of effective treatment, undiagnosed OSA remains a challenge. The gold standard diagnostic tool is polysomnography (PSG), yet the test is expensive, labour intensive and time-consuming. Home-based, limited channel sleep study testing (levels 3 and 4) can advance and widen access to diagnostic services. This systematic review aims to summarise available evidence regarding the cost-effectiveness of limited channel tests compared to laboratory and home PSG in diagnosing OSA.

METHODS

Eligible studies will be identified using a comprehensive strategy across the following databases from inception onwards: MEDLINE, PsychINFO, SCOPUS, CINAHL, Cochrane Library, Emcare and Web of Science Core Collection and ProQuest databases. The search will include a full economic evaluation (i.e. cost-effectiveness, cost-utility, cost-benefit, cost-consequences and cost-minimisation analysis) that assesses limited channel tests and PSG. Two reviewers will screen, extract data for included studies and critically appraise the articles for bias and quality. Meta-analyses will be conducted if aggregation of outcomes can be performed. Qualitative synthesis using a dominance ranking matrix will be performed for heterogeneous data.

DISCUSSION

This systematic review protocol uses a rigorous, reproducible and transparent methodology and eligibility criteria to provide the current evidence relating to the clinical and economic impact of limited channel and full PSG OSA diagnostic tests. Evidence will be examined using standardised tools specific for economic evaluation studies.

TRIAL REGISTRATION

PROSPERO (CRD42020150130).

OSA severity assessment based on sleep breathing analysis using ambient microphone

In this paper, an audio-based system for severity estimation of obstructive sleep apnea (OSA) is proposed. The system estimates the apnea-hypopnea index (AHI), which is the average number of apneic events per hour of sleep. This system is based on a Gaussian mixture regression algorithm that was trained and validated on full-night audio recordings. Feature selection process using a genetic algorithm was applied to select the best features extracted from time and spectra domains. A total of 155 subjects, referred to in-laboratory polysomnography (PSG) study, were recruited. Using the PSG's AHI score as a gold-standard, the performances of the proposed system were evaluated using a Pearson correlation, AHI error, and diagnostic agreement methods. Correlation of R=0.89, AHI error of 7.35 events/hr, and diagnostic agreement of 77.3% were achieved, showing encouraging performances and a reliable non-contact alternative method for OSA severity estimation.

Comparison of a simple obstructive sleep apnea screening device with standard in-laboratory polysomnography

BACKGROUND

Obstructive sleep apnea (OSA) is a common underdiagnosed sleep disorder. Various strategies have been employed to easily screen for OSA. The ApneaStrip® (AS - S.L.P. Ltd, Tel Aviv, Israel) is an FDA approved OSA screening device applied to the upper lip at home. We evaluated the performance of this device against simultaneous in-laboratory polysomnography (PSG) in a group of well-characterized OSA patients.

METHODS

Diagnostic PSG was performed in 56 patients (29 M, 37 F; age 48.9 ± 14.6 years; body mass index [BMI] 37.5 ± 9.0 kg/m(2); apnea-hypopnea index-events/h-[AHI] 32.8 ± 22.9). The AS was applied and positioned to detect nasal and oral airflow. The AS gives a "positive" result for AHI ≥ 15. We examined the sensitivity and specificity of the AS against three thresholds derived from PSG: AHI ≥ 5, AHI ≥ 15 (company recommendation), and AHI ≥ 30.

RESULTS

For PSG AHI ≥ 15, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the AS were 80, 54.5, 87.8, and 40 %, respectively. For PSG AHI ≥ 5, the values were 75.1, 66.7, 97.1, and 13.3 %, respectively. For PSG AHI ≥ 30, the values were 86.9, 36.2, 48.8, and 80 %, respectively. There were no significant modifying effects of age, BMI, gender, hypertension, diabetes, lung disease, and heart disease.

CONCLUSION

The AS has a high sensitivity for detection of OSA with AHI ≥ 15, but only modest specificity. The AS could be a useful component of an OSA screening program; however, negative results should be interpreted cautiously.

Detection of Obstructive sleep apnea in awake subjects by exploiting body posture effects on the speech signal

Obstructive sleep apnea (OSA) is a common sleep disorder. OSA is associated with several anatomical and functional abnormalities of the upper airway. It was shown that these abnormalities in the upper airway are also likely to be the reason for increased rate of apneic events in the supine position. Functional and structural changes in the vocal tract can affect the acoustic properties of speech. We hypothesize that acoustic properties of speech that are affected by body position may aid in distinguishing between OSA and non-OSA patients. We aimed to explore the possibility to differentiate OSA and non-OSA patients by analyzing the acoustic properties of their speech signal in upright sitting and supine positions. 35 awake patients were recorded while pronouncing sustained vowels in the upright sitting and supine positions. Using linear discriminant analysis (LDA) classifier, accuracy of 84.6%, sensitivity of 92.7%, and specificity of 80.0% were achieved. This study provides the proof of concept that it is possible to screen for OSA by analyzing and comparing speech properties acquired in upright sitting vs. supine positions. An acoustic-based screening system during wakefulness may address the growing needs for a reliable OSA screening tool; further studies are needed to support these findings.

Cost-benefit Analysis of Polysomnography versus Clinical Assessment Score-15 (CAS-15) for Treatment of Pediatric Sleep-disordered Breathing

Objective

To determine the cost of medical care using the Clinical Assessment Score-15 (CAS-15) scale versus polysomnography (PSG) for children with sleep-disordered breathing in terms of benefit.

Study Design

Cost-benefit analysis.

Setting

Hospital-based pediatric otolaryngology practice.

Subjects and Methods

Ninety-three patients from our original CAS-15 study were included. Four clinical measures were used and payment data were obtained. Cost-benefit analysis was performed for 2 clinical pathways. In pathway 1, all children had PSG; those with positive studies were referred for adenotonsillectomy. In pathway 2, children with CAS-15 ≥ 32 were referred for adenotonsillectomy regardless of PSG. Paired t test compared intrasubject mean total cost (pathway 1 vs pathway 2). Further analyses computed a change score for the clinical measures (follow-up minus baseline); these were divided by estimated treatment cost, producing 4 cost-benefit ratios for each pathway. Paired t tests compared the mean of these ratios between the pathways.

Results

Of 65 PSG+ (15 CAS–), 54 underwent surgery; of 28 PSG– (17 CAS–), 7 underwent surgery. Model estimated costs demonstrate a mean cost benefit of $US1172 (SE = $214) for pathway 2 versus pathway 1 ( P < .001). CAS-15 is also cost-beneficial versus PSG in 3 of 4 clinical measures (Child Behavior Checklist total problem T score, P = .008, mean OSA-18 survey score, P < .001, apnea hypopnea index, P < .001).

Conclusions

We present evidence that a CAS-15–based treatment decision criterion is superior to PSG in terms of monetary cost and in benefit per unit cost for 3 of 4 clinical measures evaluated.

The economic impact of obstructive sleep apnea

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) has a substantial economic impact on healthcare systems. We reviewed parameters affecting healthcare costs (race, low education, and socioeconomic status) on OSA comorbidity, and costs and the effect of OSA treatment on medical costs.

RECENT FINDINGS

OSA is associated with increased cardiovascular disease (CVD) morbidity and substantially increased medical costs. Risk for OSA and resulting CVD are associated with obesity, tobacco smoking, black race, and low socioeconomic status; all these are associated with poor continuous positive airway pressure (CPAP) adherence. Healthcare costs are not normally distributed, that is, the costliest and the sickest upper third of patients consume 65-82% of all medical costs. Only a limited number of studies have explored the effect of CPAP on medical costs.

SUMMARY

Costs of untreated OSA may double the medical expenses mainly because of CVD. Identifying the costliest, sickest upper third of OSA patients will reduce expenses to healthcare systems. Studies exploring the effect of CPAP on medical costs are essential. In addition, tailoring intervention programs to reduce barriers to adherence have the potential to improve CPAP treatment, specially in at-risk populations that are sicker and consume more healthcare costs.

Diagnosis of obstructive sleep apnea using pulse oximeter derived photoplethysmographic signals

OBJECTIVES

Increasing awareness of the high prevalence of obstructive sleep apnea (OSA) and its impact on health in conjunction with high cost, inconvenience, and short supply of in-lab polysomnography (PSG) has led to the development of more convenient, affordable, and accessible diagnostic devices. We evaluated the reliability and accuracy of a single-channel (finger pulse-oximetry) photoplethysmography (PPG)-based device for detection of OSA (Morpheus Ox).

METHODS

Among a cohort of 73 patients referred for in-laboratory evaluation of OSA, 65 were simultaneously monitored with the PPG based device while undergoing PSG. Among these, 19 had significant cardiopulmonary comorbidities. Using the PSG as the "gold standard," the sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), as well as the positive likelihood ratio (+LR) for an apnea hypopnea index (AHI)PSG > 5/h and AHIPSG > 15/h were calculated for the PPG.

RESULTS

Valid results were available for 65 subjects. Mean age: 52.1 ± 14.2, Male: 52%, and BMI: 36.3 ± 9.7 kg/m(2). Positive correlation was found between PPG-derived and PSG-derived AHI (r = 0.81, p < 0.001). For AHIPSG > 5/h, sensitivity was 80%, specificity 86%, PPV 93%, NPV 68%, and +LR was 5.9. For AHIPSG > 15/h, sensitivity was 70%, specificity 91%, PPV 80%, NPV 85%, and +LR was 7.83. The corresponding areas under the receiver operator curves were 0.91 and 0.9.

CONCLUSIONS

PPG-derived data compare well with simultaneous in-lab PSG in the diagnosis of suspected OSA among patients with and without cardiopulmonary comorbidities.

CITATION

Romem A; Romem A; Koldobskiy D; Scharf SM. Diagnosis of obstructive sleep apnea using pulse oximeter derived photoplethysmographic signals.

Automated sleep apnea quantification based on respiratory movement

Obstructive sleep apnea (OSA) is a prevalent and treatable disorder of neurological and medical importance that is traditionally diagnosed through multi-channel laboratory polysomnography(PSG). However, OSA testing is increasingly performed with portable home devices using limited physiological channels. We tested the hypothesis that single channel respiratory effort alone could support automated quantification of apnea and hypopnea events. We developed a respiratory event detection algorithm applied to thoracic strain-belt data from patients with variable degrees of sleep apnea. We optimized parameters on a training set (n=57) and then tested performance on a validation set (n=59). The optimized algorithm correlated significantly with manual scoring in the validation set (R2=0.73 for training set, R2=0.55 for validation set; p<0.05). For dichotomous classification, the AUC was >0.92 and >0.85 using apnea-hypopnea index cutoff values of 5 and 15, respectively. Our findings demonstrate that manually scored AHI values can be approximated from thoracic movements alone. This finding has potential applications for automating laboratory PSG analysis as well as improving the performance of limited channel home monitors.

Effectiveness of three sleep apnea management alternatives

RATIONALE

Home respiratory polygraphy (HRP) may be a cost-effective alternative to polysomnography (PSG) for diagnosis and treatment election in patients with high clinical probability of obstructive sleep apnea (OSA), but there is conflicting evidence on its use for a wider spectrum of patients.

OBJECTIVES

To determine the efficacy and cost of OSA management (diagnosis and therapeutic decision making) using (1) PSG for all patients (PSG arm); (2) HRP for all patients (HRP arm); and (3) HRP for a subsample of patients with high clinical probability of being treated with continuous positive airway pressure (CPAP) and PSG for the remainder (elective HRP arm).

METHODS

Multicentric study of 366 patients with intermediate-high clinical probability of OSA, randomly subjected to HRP and PSG. We explored the diagnostic and therapeutic decision agreements between the PSG and both HRP arms for several HRP cutoff points and calculated costs for equal diagnostic and/or therapeutic decision efficacy.

RESULTS

For equal diagnostic and therapeutic decision efficacy, PSG arm costs were 18% higher than HRP arm costs and 20% higher than elective HRP arm costs. HRP arm costs tended to be lower than elective HRP arm costs, and both tended to be lower than PSG arm costs if patient costs were omitted.

CONCLUSION

Home respiratory polygraphy is a less costly alternative than polysomnography for the diagnosis and therapeutic decision making for patients with suspected obstructive sleep apnea. We found no advantage in cost terms, however, in using home respiratory polygraphy for all patients or home respiratory polygraphy for the most symptomatic patients and polysomnography for the rest.

Obstructive apnea hypopnea index estimation by analysis of nocturnal snoring signals in adults

STUDY OBJECTIVE

To develop a whole-night snore sounds analysis algorithm enabling estimation of obstructive apnea hypopnea index (AHI(EST)) among adult subjects.

DESIGN

Snore sounds were recorded using a directional condenser microphone placed 1 m above the bed. Acoustic features exploring intra-(mel- cepstability, pitch density) and inter-(running variance, apnea phase ratio, inter-event silence) snore properties were extracted and integrated to assess AHI(EST).

SETTING

University-affiliated sleep-wake disorder center and biomedical signal processing laboratory.

PATIENTS

Ninety subjects (age 53 ± 13 years, BMI 31 ± 5 kg/m(2)) referred for polysomnography (PSG) diagnosis of OSA were prospectively and consecutively recruited. The system was trained and tested on 60 subjects. Validation was blindly performed on the additional 30 consecutive subjects.

MEASUREMENTS AND RESULTS

AHI(EST) correlated with AHI (AHI(PSG); r(2) = 0.81, P < 0.001). Area under the receiver operating characteristic curve of 85% and 92% for thresholds of 10 and 20 events/h, respectively, were obtained for OSA detection. Both Altman-Bland analysis and diagnostic agreement criteria revealed 80% and 83% agreements of AHI(EST) with AHI(PSG), respectively.

CONCLUSIONS

Acoustic analysis based on intra- and inter-snore properties can differentiate subjects according to AHI. An acoustic-based screening system may address the growing needs for reliable OSA screening tool. Further studies are needed to support these findings.

Impact of sleep apnea on economics

Obstructive sleep apnea syndrome (OSA) alters sleep quality and is associated with sleepiness and decreased cognitive functioning. It has therefore always been recognized as a major public health issue with potential societal consequences: accidents, increased morbidity, and cognitive deficits impairing work efficiency. The number of patients diagnosed and treated for OSA has increased drastically in the last few years. In response to this epidemic, health authorities have encouraged studies investigating how patients cope with OSA and also its diagnosis, comparing ambulatory to hospital-based polysomnography. Based on epidemiological knowledge, this review aims to carefully describe the possible links between sleep apnea and public health concerns along with identifying the certitudes and missing data concerning the consequences of sleep apnea on accidents, work, economics and health-related quality of life.

The role of polysomnography in diagnosing and treating obstructive sleep apnea in pediatric patients

Obstructive sleep apnea in children is associated with serious neurocognitive and cardiovascular morbidity, systemic inflammation, and increased health care use, yet remains underdiagnosed. Although the prevalence of obstructive sleep apnea is 1-3% in the pediatric population, the prevalence of primary snoring (PS) is estimated to be 3-12%. The challenge for pediatricians is to differentiate PS from obstructive sleep apnea in a cost-effective, reliable, and accurate manner before recommending invasive or intrusive therapies, such as surgery or continuous positive airway pressure. The validity of polysomnography as the gold standard for diagnosing obstructive sleep apnea has been challenged, primarily related to concerns that abnormalities on polysomnography do not correlate well with adverse outcomes, that those abnormalities have statistical more than clinical significance, and that performing polysomnograms on all children who snore is a practical impossibility. The aim of this article is to review the clinical utility of diagnostic tests other than polysomnography to diagnose obstructive sleep apnea, to highlight the limitations and strengths of polysomnography, to underscore the threshold levels of abnormalities detected on polysomnography that correlate with morbidity, and to discuss what the practical implications are for treatment.

Portable monitoring devices in the diagnosis of obstructive sleep apnea: current status, advantages, and limitations

Recent years have seen a growing interest in the use of portable monitoring devices for the diagnosis of obstructive sleep apnea syndrome. These have the potential to be used in lieu of the more complicated and uncomfortable alternative, polysomnography, which has long been considered to be the gold standard for the diagnosis of this relatively prevalent condition. Following their approval in 2008 by the Center of Medicare and Medicaid Services, the federal agency which administers Medicare and Medicaid in the United States, there has been extensive discussion about the utility and validity of these devices for use in the diagnosis of obstructive sleep apnea syndrome. Although there are various models of portable monitoring devices, the literature contains little information regarding how each device should be used in specific age groups, patients presenting comorbidities, and asymptomatic patients. Additionally, studies about the cost-effectiveness of this diagnostic method are scarce and conflicting. Therefore, this objective of this study was to review what has been learned about portable monitoring devices over time, as well as to examine the recent progress, advantages, limitations, and applications of these devices in the diagnosis of obstructive sleep apnea syndrome in different groups of patients.

Nocturnal sound analysis for the diagnosis of obstructive sleep apnea

A novel method for screening obstructive sleep apnea syndrome (OSAs) based on nocturnal acoustic signal is proposed. Full-night audio signals from sixty subjects were segmented into snore, noise and silence events using semi-automatic algorithm based on Gaussian mixture models which achieves more than 90% (92%) sensitivity (specificity) and produces an average of 2,000 snores per subject. A classification into 3 groups is proposed for the diagnosis: comparison group - non-OSA subjects (apnea hypopnea index, AHI < 10), mild to moderate OSA (10 < AHI < 30) and severe OSA (AHI>30). A Bayes classifier was implemented, fed with five acoustic features, all correlated with the severity of the syndrome: (1) Inter Event Silence, which quantifies segments suspicious as apnea; (2) Mel Cepstability, measures the entire night stability of the spectrum, expressed using mel-frequency cepstrum; (3) Energy Running Variance, a criterion for the variation of the nocturnal acoustic pattern; (4) Apneic Phase Ratio, exploiting the finding that snores around apnea events expressing larger acoustic variation; and (5) Pitch Density. Correct classification of 92% for resubstitution method and 80% for 5-fold cross validation method was achieved. Moreover, in a case of two groups with a threshold of AHI=10, a sensitivity (specificity) of 96.5% (90.6%) and 87.5% (82.1%) for resubstitution and cross-validation respectively were obtained.

Automatic detection of obstructive sleep apnea using speech signals

Obstructive sleep apnea (OSA) is a common disorder associated with anatomical abnormalities of the upper airways that affects 5% of the population. Acoustic parameters may be influenced by the vocal tract structure and soft tissue properties. We hypothesize that speech signal properties of OSA patients will be different than those of control subjects not having OSA. Using speech signal processing techniques, we explored acoustic speech features of 93 subjects who were recorded using a text-dependent speech protocol and a digital audio recorder immediately prior to polysomnography study. Following analysis of the study, subjects were divided into OSA (n=67) and non-OSA (n=26) groups. A Gaussian mixture model-based system was developed to model and classify between the groups; discriminative features such as vocal tract length and linear prediction coefficients were selected using feature selection technique. Specificity and sensitivity of 83% and 79% were achieved for the male OSA and 86% and 84% for the female OSA patients, respectively. We conclude that acoustic features from speech signals during wakefulness can detect OSA patients with good specificity and sensitivity. Such a system can be used as a basis for future development of a tool for OSA screening.

Ambulatory management of patients with sleep apnea: is there a place for portable monitor testing?

Portable monitor testing is being increasingly used as an alternative strategy for the diagnosis and treatment of patients with obstructive sleep apnea. Portable monitors have become progressively sophisticated but lack standardization. Recent studies comparing clinical outcomes of ambulatory management pathways using portable monitor testing support their use in patients with a high pretest probability for obstructive sleep apnea. Whether ambulatory management is cost-effective and will improve patient access to diagnosis and treatment requires further investigation.

Validation study of a portable monitoring device for identifying OSA in a symptomatic patient population

BACKGROUND AND OBJECTIVE

Obstructive sleep apnoea syndrome (OSAS) is a common disorder associated with early atherosclerosis, diabetes mellitus, ischaemic heart disease and cerebrovascular disease. The gold standard for confirming OSAS is based on an attended overnight polysomnography (PSG) in a sleep laboratory; however lack of health-care resources creates long waiting times for patient access to this diagnostic test. This study evaluated the ability of a portable sleep-monitoring device to identify patients in Hong Kong with suspected OSAS.

METHODS

Patients with symptoms of OSAS were invited to use the ARES (apnoea risk evaluation system) concurrently with an attended inpatient PSG. Several sets of AHI were generated by the ARES provider based on different oxygen desaturation criteria and surrogate parameters of arousal. The results were compared against PSG to determine the optimal sensitivity and specificity.

RESULTS

There were 141 patients who completed the study successfully. Results of AHI from the ARES study were presented in the order of different scoring criteria--4% oxygen desaturation alone, obstructive events with 3% oxygen desaturation and obstructive events with 1% desaturation plus surrogate arousal criteria. The sensitivity was 0.84 (95% confidence interval (CI): 0.77-0.90), 0.89 (95% CI: 0.89-0.94) and 0.97 (95% CI: 0.94-0.99), respectively. The specificity was 1, 1 and 0.63 (95% CI: 0.55-0.71), respectively. The receiver operating curve had an area of 0.96, 0.97 and 0.98, respectively. The kappa coefficient varied from 0.24 to 0.55 for agreement of severity between PSG and ARES. The likelihood ratio positive and the likelihood ratio negative were 2.61, infinity, infinity and 0.16, 0.11, 0.05, respectively, in the order of oxygen desaturation described earlier.

CONCLUSIONS

The ARES device has reasonable sensitivity and specificity for diagnosing severe OSAS in symptomatic Chinese patients. There is moderate agreement between ARES and PSG in the diagnosis of severe disease, but less agreement in patients with mild/moderate disease.

Estimated cost of crashes in commercial drivers supports screening and treatment of obstructive sleep apnea

Sleep apnea among commercial drivers may increase the risk of fall-asleep crashes, which incur large expenses. Drivers of passenger cars whose apnea is treated experience lower crash risk. Among community-based holders of commercial driver's licenses, we considered three methods for identifying sleep apnea syndrome: (1) in-lab polysomnography; (2) selective in-lab polysomnography for high-risk drivers, where high risk is first identified by body mass index, age and gender, followed by oximetry in a subset of drivers; (3) not screening. The costs for each of these three programs equaled the sum of the costs of testing, treatment of identified cases, and crashes. Assuming that treatment prevents apnea-related crashes, polysomnography is not cost-effective, because it was more expensive than the cost of crashes when no screening is done. Screening with BMI, age and gender, however, with confirmatory in-lab polysomnography only on high-risk drivers was cost-effective, as long as a high proportion (73.8%) of screened drivers accepts treatment. These findings indicate that strategies that reduce reliance on in-laboratory polysomnography may be more cost-effective than not screening, and that treatment acceptance may need to be a condition of employment for affected drivers.

Role of portable sleep studies for diagnosis of obstructive sleep apnea

PURPOSE OF REVIEW

There is growing awareness of the significance of obstructive sleep apnea in the general population and in the medical community and, as a result, there is a growing demand for diagnosis and treatment. Attended, in-laboratory polysomnography is resource intensive and not readily available in some communities. Alternate diagnostic strategies have been proposed including the use of home sleep studies. Although these portable systems have been in use for many years, only in the past few years have a significant number of studies been performed to evaluate these systems in the home setting. The use of actigraphy and peripheral arterial tonometry for diagnostic purposes has also recently been investigated.

RECENT FINDINGS

In the laboratory setting, measurements of sleep-disordered breathing with specific portable sleep systems correspond well with measurements provided by standard polysomnography. In the home setting, portable systems demonstrate several important limitations including lost or inadequate data collection, logistic concerns, and mildly reduced diagnostic accuracy. Data regarding the potential cost benefit of home studies is inconclusive.

SUMMARY

Home polysomnography is a viable option for evaluating patients with moderate or high clinical suspicion for sleep-disordered breathing. However, patients with failed or equivocal home studies and those with negative studies but persistent symptoms should undergo standard polysomnography. Further investigations are needed to compare long-term outcomes in patients evaluated using portable devices versus standard polysomnography.

Obstructive sleep apnoea

Obstructive sleep apnoea is a disease of increasing importance because of its neurocognitive and cardiovascular sequelae. Abnormalities in the anatomy of the pharynx, the physiology of the upper airway muscle dilator, and the stability of ventilatory control are important causes of repetitive pharyngeal collapse during sleep. Obstructive sleep apnoea can be diagnosed on the basis of characteristic history (snoring, daytime sleepiness) and physical examination (increased neck circumference), but overnight polysomnography is needed to confirm presence of the disorder. Repetitive pharyngeal collapse causes recurrent arousals from sleep, leading to sleepiness and increased risk of motor vehicle and occupational accidents. The surges in hypoxaemia, hypercapnia, and catecholamine associated with this disorder have now been implicated in development of hypertension, but the association between obstructive sleep apnoea and myocardial infarction, stroke, and congestive heart failure is not proven. Continuous positive airway pressure, the treatment of choice for obstructive sleep apnoea, reduces sleepiness and improves hypertension.