Validation of a portable recording device (ApneaLink) for identifying patients with suspected obstructive sleep apnoea syndrome

Background: Polysomnography (PSG) is currently the standard diagnostic procedure for sleep apnoea. This study evaluates the diagnostic accuracy of a portable recording device, ApneaLink (AL; ResMed, Poway, CA, USA) for detection of sleep apnoea in comparisons against PSG.
Methods: The AL device is a three-channel screening tool that measures airflow through a nasal pressure transducer, oximetry and pulse, providing an apnoea–hypopnoea index (AHI) based on recording time. Nocturnal PSG (Alice 4; Healthdyne, Atlanta, GA, USA), with airflow measured by a nasal pressure transducer (ProTech PTAF2; ProTech, Woodinville, WA, USA) and AL recordings were carried out simultaneously in consecutive patients with suspected obstructive sleep apnoea syndrome (OSAS). The PSG recordings were analysed manually by a blinded investigator. The oxygen desaturation index of AL was also compared against the AHI based on PSG.
Results: Fifty consecutive subjects with symptoms of OSAS were recruited with mean age of 50 years and body mass index of 27.9 kg/m². The AHI obtained by the AL device correlated closely to that obtained by PSG (Pearson correlation, r = 0.978, P < 0.001), whereas the correlation between PSG AHI and oxygen desaturation index by AL was also strong ( r = 0.895, P < 0.001). Comparison of AHI based on the AL against the PSG demonstrated high sensitivity and specificity at AHI ≥10/h (sensitivity 0.977 and specificity 1.0) and at AHI ≥20/h (sensitivity 0.969 and specificity 1.0).
Conclusion: The AL portable monitoring device is highly sensitive and specific in quantifying the apnoea–hypopnoea index when compared against hospital based polysomnography in patients with suspected OSAS. The simple device may be useful for screening and diagnostic purpose when access to PSG is limited.     

Validation of Embletta portable diagnostic system for identifying patients with suspected obstructive sleep apnoea syndrome (OSAS)

Background and objectives: This study aimed to evaluate the diagnostic accuracy of Embletta portable diagnostic system (PDS, Medcare, Reykjavik, Iceland) for the screening of sleep apnoea in clinical practice. Methods: The Embletta PDS is a digital three‐channel recording device that measures airflow through a nasal cannula connected to a pressure transducer, oxygen saturation plus both respiratory and abdominal movements via built‐in effort and body position sensors. An AHI is determined based on recording time. Nocturnal polysomnography (Alice 4, Healthdyne, Atlanta, USA), with airflow measured by a nasal pressure transducer (PTAF2, Pro‐Tech, Woodinville, WA, USA)) and Embletta PDS recordings, was performed simultaneously in consecutive patients with suspected OSA syndrome. The PSG recordings were analysed manually by a blinded investigator. Results: Ninety subjects were recruited and 10 failed Embletta PDS studies due to measurement failure. Among the remaining 80 subjects, 63 were males. The mean age (SD) was 51.4 (11.9) years old, BMI 27.1(4.2) kg/m², neck circumference 38.6 (3.6) cm and Epworth Sleepiness Score 9.7 (5.3). The AHI obtained by the Embletta PDS correlated closely with that obtained by PSG (Pearson correlation, r = 0.979, P < 0.001). Comparison of AHI based on the Embletta PDS against the PSG demonstrated high sensitivity at AHI ≥ 5/h (sensitivity 0.924 and specificity 0.857) and high specificity at AHI ≥ 20/h (sensitivity 0.853 and specificity 0.957). Conclusions: The Embletta PDS is a highly sensitive and specific screening device in quantifying AHI when compared against PSG in patients with suspected OSA syndrome.     

Comparison of empirical continuous positive airway pressure (CPAP) treatment versus initial portable sleep monitoring followed by CPAP treatment for patients with suspected obstructive sleep apnoea

Background: Polysomnography is labour‐intensive for diagnosing obstructive sleep apnoea (OSA). We compared two algorithms for initiating continuous positive airway pressure (CPAP) treatment for patients with suspected OSA. Methods: Symptomatic OSA patients were randomised into either algorithm I or II. Algorithm I consisted of an empirical CPAP trial whereas algorithm II utilised an Apnea Risk Evaluation System, a wireless device applied on the forehead, for establishing a diagnosis before a CPAP trial for 3 weeks. Primary outcome was success of CPAP trial, defined as CPAP usage > 4 h/night and willingness to continue CPAP. Subjective usefulness of CPAP, accuracy of Apnea Risk Evaluation System versus polysomnography and CPAP adherence at 6 months were secondary end‐points. Results: Altogether 138 patients in algorithm I and 110 patients in algorithm II completed the CPAP trial. There were no significant differences between these algorithms with respect to the primary end‐point. The sensitivity and specificity of algorithm I versus II as a diagnostic test for OSA were 0.3, 0.8 versus 0.31, 1.00 respectively. In predicting CPAP adherence at 6 months, the likelihood ratio positive for algorithms I and II was 2.7 and 5.27 respectively. The mean (SE) time taken from the first consultation to the end of CPAP trial in algorithm I and algorithm II was 60 (2) and 98 (5) days, respectively, P < 0.01. Conclusion: An ambulatory approach with portable sleep monitoring for diagnosing OSA before a CPAP trial can identify more patients who would adhere to CPAP at 6 months than empirical CPAP treatment alone.     

Diagnostic accuracy of a questionnaire and simple home monitoring device in detecting obstructive sleep apnoea in a Chinese population at high cardiovascular risk

Background and objective: OSA is a common condition associated with cardiovascular (CV) morbidity. It remains underdiagnosed globally in part due to the limited availability and technical requirements of polysomnography (PSG). The aim of this study was to test the accuracy of two simple methods for diagnosing OSA. Methods: Consecutive subjects identified from a community register with high CV risk were invited to complete the Berlin Sleep Questionnaire and undergo simultaneous, home, overnight PSG and ApneaLink device oximetry and nasal pressure recordings. The relative accuracies of the Berlin Questionnaire, oximetry and nasal pressure results in diagnosing PSG‐defined moderate‐severe OSA were assessed. Results: Of 257 eligible high CV risk subjects enrolled, 190 completed sleep studies and 143 subjects' studies were of sufficient quality to include in final analyses. Moderate‐severe OSA was confirmed in 43% of subjects. The Berlin Questionnaire had low overall diagnostic accuracy in this population. However, ApneaLink recordings of oximetry and nasal pressure areas had high diagnostic utility with areas under the receiver operating characteristic curves of 0.933 and 0.933, respectively. At optimal diagnostic thresholds, oximetry and nasal pressure measurements had similar sensitivity (84% vs 86%) and specificity (84% vs 85%). Technical failure was lower for oximetry than nasal pressure (5.8% vs 18.9% of tests). Conclusions: In patients with high CV risk overnight single‐channel oximetry and nasal pressure measurements may provide high diagnostic accuracy and offer an accessible alternative to full PSG.     

New acoustic method for detecting upper airway obstruction in patients with sleep apnoea

Background and objective: OSA is a common disorder resulting in health and economic burdens. Currently identifying OSA in patients involves expensive techniques that require overnight studies in a laboratory setting with qualified staff. This paper tests a new acoustic device (AirwayClear (AC)) for assessing upper airway patency in human subjects with OSA. We hypothesize that obstructive apnoeas would be detected equally well with AC and polysomnography (PSG). Methods: Twenty‐three patients with severe OSA underwent an overnight CPAP titration study. We introduced pseudorandom noise (600–1200 Hz) using AC to the patient's nasal mask during 1 h of subtherapeutic CPAP. AC determined a measure of airway patency based on the level of pseudorandom noise reaching a sternal notch sensor. The ability of AC to detect obstructive respiratory events was compared with standard PSG. Results: Three hundred and twenty‐two obstructive events (obstructive and mixed apnoeas) were identified by PSG. AC scored 80% as complete obstructions and 16% as partial obstructions. Conversely, AC detected 281 complete obstructions. PSG recognized 84% as apnoeas and scored 11% as hypopnoeas. Of the 204 hypopnoeas identified with PSG, AC indicated the airway was partially or completely obstructed in 69% of patients. A Bland–Altman analysis for the apnoeas from the two measures showed a mean difference of 2.3 events/h and 95% confidence intervals of ±15.5 events/h. Conclusions: We conclude that AC is able to track airway patency and to identify airway closure in patients with OSA.     

Sleep disorders: a potential role in New Zealand motor vehicle accidents

Background: The potential role of sleep disorders in New Zealand motor vehicle accidents (MVA) has not been systematically studied. Aims: To trial a recruitment method and document the frequency of sleep disorders in drivers attending an emergency department with injury following MVA. Methods: Injured drivers admitted to Wellington Hospital Emergency Department were prospectively recruited by letter and follow‐up telephone call. Data from a traffic accident, health and sleep questionnaire and polysomnography were collected and analysed using the SPSS statistical package. Results: Of 120 eligible drivers, 40 (33%) completed the study protocol. The mean age of participants was 44 ± 17 years. Non‐participants were younger (mean age 33 ± 14 years, P < 0.01) and more often of Asian or Pacific Island ethnicity (P < 0.01). Twenty‐seven (67%) felt unrefreshed on waking and 10 (25%) had an elevated Epworth Sleepiness Score (> 10/24). Six (15%) felt drowsy or fell asleep prior to the accident. Sleep disorders were common (40%): obstructive sleep apnoea 14 (35.9%), periodic limb movements of sleep three (7.7%), sleep restriction (< 6 h sleep on a regular basis) five (12.5%), and insomnia one (2.5%). Conclusions: Daytime somnolence and sleep disorders were commonly found in drivers attending the Emergency Department after accidents resulting in injury. Driver fatigue and sleep disorders should be considered as a potential contributing factor in New Zealand MVAs. Recruitment of drivers following a MVA via the Emergency Department is challenging. Strategies to improve recruitment are discussed. (Intern Med J 2002; 32: 297?304)     

Ambulatory models of care for obstructive sleep apnoea: Diagnosis and management

The high prevalence of obstructive sleep apnoea (OSA) and increasing awareness of its potential health consequences has placed significant pressure on laboratory‐based sleep services leading to growing waiting lists and delays in diagnosis and treatment. Consequently, there has been increasing interest in the use of simplified, ambulatory models of care involving clinical prediction tools, portable sleep monitoring and home autotitrating continuous positive airway pressure. Researchers are also exploring the potential role for a wider range of health‐care providers, including trained nurses and general practitioners, in the primary management of OSA. Recent randomized, controlled studies evaluating the clinical effectiveness of ambulatory management strategies versus traditional laboratory‐based care for patients with OSA have consistently demonstrated that comparable patient outcomes can be achieved. The cost‐effectiveness of these strategies is currently being debated, and further research examining the long‐term economic implications of ambulatory models of care is needed.     

A high prevalence of sleep disordered breathing in men with mild symptomatic chronic heart failure due to left ventricular systolic dysfunction

BACKGROUND: Sleep disordered breathing (SDB) is common in severe chronic heart failure (CHF) and is associated with increased morbidity and mortality. The prevalence of SDB in mild symptomatic CHF is unknown. AIM: The aim of this study was to determine the prevalence and characteristics of SDB in male patients with NYHA class II symptoms of CHF. METHODS AND RESULTS: 55 male patients with mild symptomatic CHF underwent assessment of quality of life, echocardiography, cardiopulmonary exercise, chemoreflex testing and polysomnography. 53% of the patients had SDB. 38% had central sleep apnoea (CSA) and 15% had obstructive sleep apnoea. SDB patients had steeper VE/VCO(2) slope [median (inter-quartile range) 31.1 (28-37) vs. 28.1 (27-30) respectively; p=0.04], enhanced chemoreflexes to carbon dioxide during wakefulness [mean+/-sd: 2.4+/-1.6 vs. 1.5+/-0.7 %VE Max/mmHg CO(2) respectively; p=0.03], and significantly higher levels of brain natriuretic peptide and endothelin-1 compared to patients without SDB. No differences in left ventricular ejection fraction, percent predicted peak oxygen uptake, or symptoms of SDB were observed. CONCLUSIONS: A high prevalence of SDB was found in men with mild symptomatic CHF. Patients with SDB could not be differentiated by symptoms or by routine cardiac assessment making clinical diagnosis of SDB in CHF difficult.     

Update on the use of portable monitoring system for the diagnosis of sleep apnea in specific population

The prevalence and severity of obstructive sleep apnea (OSA) is higher in specific population: children, elderly, obese and patients with pulmonary and cardiovascular diseases, compared to the general population. OSA is associated with greater morbidity and mortality in these patients. Although full-night polysomnography is still the gold standard diagnostic sleep study for OSA, it is a time consuming, expensive and technically demanding exam. Over the last few years, there is growing evidence on the use of portable monitors (PM) as an alternative for the diagnosis of OSA. These devices were developed specially for sleep evaluation at home, at a familiar environment, with easy self-application of monitoring, unattended. The use of PM is stablished for populations with high pre-test probability of OSA. However, there is a lack of studies on the use of PM in age extremes and patients with comorbidities. The purpose of this review is to present the studies that evaluated the use of PM in specific population, as well as to describe the advantages, limitations and applications of these devices in this particular group of patients. Although the total loss rate of recordings is variable in different studies, the agreement with full-night polysomnography justifies the use of PM in this population.     

Comparison of existing symptom-based questionnaires for identifying COPD in the general practice setting

OBJECTIVE: Underdiagnosis of COPD is widespread, at least in part due to underuse of spirometry. Symptom-based questionnaires may be helpful as an adjunct to spirometry. The aim of this study was to determine which types of questions might aid in identifying COPD. METHODOLOGY: Questionnaires were identified by literature review and input from a multinational advisory board of primary care providers. Questions were placed into groups and evaluated with respect to their ability to perform in two scenarios: (i) to identify persons with COPD from a general population (Case-finding scenario); and (ii) to distinguish persons with COPD from those with asthma (Differential Diagnosis scenario). Questions were retrospectively validated using the Third National Health and Nutrition Examination Survey data. Potential predictive ability was examined in bivariate and multivariate frameworks. RESULTS: Four published question sets and six additional documents were included. There was agreement in the use of smoking and symptom-based questions, but important differences in the use of demographic, personal history and other information. Most question types had significant bivariate relationships with airway obstruction. In multivariate analysis, age, BMI, smoking status and pack-years, symptoms (cough, phlegm, dyspnoea, wheeze), and prior diagnosis consistent with asthma or COPD all showed significant ability to discriminate between persons with and without obstruction in a general population. CONCLUSION: Simple self-administered questionnaires can be used to identify persons for whom spirometric testing may be especially appropriate. Development of such questionnaires will require additional study, including prospective validation of items in an appropriate clinical setting and policy recommendations on the use of these tools.     

The minimum period of polysomnography required to confirm a diagnosis of severe obstructive sleep apnoea

Background and objective: To combine the diagnosis of OSA with titration of positive airway pressure (PAP), current guidelines recommend that split‐night polysomnography (PSG) be performed if an AHI of ≥40/h is recorded over 2 h. However, the diagnostic validity of partial‐night PSG is uncertain. This study aimed to test the validity of partial‐night PSG and to determine the optimum AHI cut‐off points. Methods: Patients who visited the sleep centre at a tertiary medical centre between January and December 2008, for symptoms related to sleep disorders (sleepiness, snoring, sleep disturbance), and who completed full‐night PSG, were evaluated for this study. Full‐night PSG data were processed to obtain partial‐night PSG data, from which AHI were computed as a reference for diagnosing severe OSA. Full‐night and partial‐night PSG data obtained over different recording times (expressed as x‐h PSG, where x = 1–6) were compared using receiver operating characteristic (ROC) curve analysis. The diagnostic validity of 2‐h PSG with different AHI cut‐off points (25/h to 45/h) was also calculated. Results: Data from 198 PSG recordings was processed. For 2‐h PSG, an AHI cut‐off point of 30/h gave the highest accuracy of 90.9%. Comparing areas under the ROC curves (AUC), 2‐h PSG (AUC = 0.97) was as good as 2.5‐h PSG (AUC = 0.977, P = 0.057) and 3‐h PSG (AUC = 0.978, P = 0.125), but was better than 1.5‐h PSG (AUC = 0.955, P = 0.016). Conclusions: Partial‐night PSG is effective for diagnosing severe OSA. If there is an unabridged PSG recording indicating an AHI of ≥30/h for 2 h, severe OSA can be diagnosed and PAP titration initiated.