Differentiating responses to obstructive sleep apnoea using pulse transit time

Conventional overnight polysomnography (PSG) used to determine the respiratory behaviour during sleep can be a complex and expensive procedure. Pulse transit time analysis (PTT) has shown potential to detect obstructive apnoeic and hypopnoeic events in adults. This study was undertaken to determine the potential of PTT to differentiate responses to upper airway obstruction. 103 obstructive respiratory events occurred in PSG studies performed on 11 children (10 male and 1 female, mean age 7.5years). PTT measurements were evaluated against the corresponding PSG results pre-scored by 2 blinded observers. Broadly, there were 2 types of responses. They can be either short period of rapid PTT decreases (Type 1) or prolonged but gradual PTT decreases (Type 2). Type 1 obstructive events showed a mean change of 51.77% (p

Classification of oximetry signals using Bayesian neural networks to assist in the detection of obstructive sleep apnoea syndrome

In the present study, multilayer perceptron (MLP) neural networks were applied to help in the diagnosis of obstructive sleep apnoea syndrome (OSAS). Oxygen saturation (SaO2) recordings from nocturnal pulse oximetry were used for this purpose. We performed time and spectral analysis of these signals to extract 14 features related to OSAS. The performance of two different MLP classifiers was compared: maximum likelihood (ML) and Bayesian (BY) MLP networks. A total of 187 subjects suspected of suffering from OSAS took part in the study. Their SaO2 signals were divided into a training set with 74 recordings and a test set with 113 recordings. BY-MLP networks achieved the best performance on the test set with 85.58% accuracy (87.76% sensitivity and 82.39% specificity). These results were substantially better than those provided by ML-MLP networks, which were affected by overfitting and achieved an accuracy of 76.81% (86.42% sensitivity and 62.83% specificity). Our results suggest that the Bayesian framework is preferred to implement our MLP classifiers. The proposed BY-MLP networks could be used for early OSAS detection. They could contribute to overcome the difficulties of nocturnal polysomnography (PSG) and thus reduce the demand for these studies.

Regularity analysis of nocturnal oximetry recordings to assist in the diagnosis of sleep apnoea syndrome

The relationship between sleep apnoea–hypopnoea syndrome (SAHS) severity and the regularity of nocturnal oxygen saturation (SaO2) recordings was analysed. Three different methods were proposed to quantify regularity: approximate entropy (AEn), sample entropy (SEn) and kernel entropy (KEn). A total of 240 subjects suspected of suffering from SAHS took part in the study. They were randomly divided into a training set (96 subjects) and a test set (144 subjects) for the adjustment and assessment of the proposed methods, respectively. According to the measurements provided by AEn, SEn and KEn, higher irregularity of oximetry signals is associated with SAHS-positive patients. Receiver operating characteristic (ROC) and Pearson correlation analyses showed that KEn was the most reliable predictor of SAHS. It provided an area under the ROC curve of 0.91 in two-class classification of subjects as SAHS-negative or SAHS-positive. Moreover, KEn measurements from oximetry data exhibited a linear dependence on the apnoea–hypopnoea index, as shown by a correlation coefficient of 0.87. Therefore, these measurements could be used for the development of simplified diagnostic techniques in order to reduce the demand for polysomnographies. Furthermore, KEn represents a convincing alternative to AEn and SEn for the diagnostic analysis of noisy biomedical signals.

Obstructive sleep apnoea is associated with sight threatening retinopathy and predicts the developement of preproliferative and proliferative retinopathy in patients with type 2 diabetes:a longitudinal analysis

troduct I on . An observational longitudinal study. P ur P ose . Assess the relationship between obstructive sleep apnoea (OSA) and DR cross-sectionally and longitudinally. M ethods . Adults with Type 2 diabetes mellitus (T2DM), who were re - cruited from a hospital-based diabetes clinic in the UK. Patients with pre-existing OSA, end-stage renal disease and non-diabetic retinopa - thy were excluded. OSA (apnoea hypopnea index ≥ 5 events/hour) was assessed by a single overnight home-based cardio-respiratory study (Alice PDX, Philips Respironics, USA). DR was assessed us - ing retinal images between 2007 and 2012. Sight threatening diabetic retinopathy (STDR) was defined as presence of pre-proliferative or proliferative DR, maculopathy or photocoagulation. Advanced DR was defined as pre-proliferative or proliferative DR. r esults . 199 patients were included (57.3% (n=114) men, 47.7% (n=95) White Europeans). STDR and OSA prevalence were 38.7% (n=77) and 62.8% respectively. A t b A sel I ne . STR prevalence was higher in patients with OSA (OSA+) compared to those without OSA (OSA-) [48.8% n=61 vs. 21.6% n=16, p<0.001]. After adjustment for confounders, OSA remained independently associated with STR (OR 3.7, 95% CI 1.6-8.9, p=0.006), maculopathy (OR 4.5, 95% CI 1.8-11.4, p=0.002) and advanced DR (OR 3.9, 95% CI 1.02-15.3, p=0.047). Mild and moderate to severe OSA were independently associated with STR and maculopathy and only moderate to severe OSA was associated with advanced DR following adjustment for con - founders. l ong I tud I n A lly . Over the follow-up period of (4.4±1 years), more OSA+ patients progressed from no or background DR to advanced DR (15.3% (n=17) vs. 3% (n=2), p=0.01). OSA was an independent pre - dictor of advanced DR development after adjustment for confounders (OR 6.6, 95% CI 1.2-35.1, p=0.03). OSA did not predict the develop - ment of maculopathy. c onclus I ons . OSA is independently associated with STR and predicts the development of preproliferative and proliferative DR. Intervention - al studies are needed to assess the impact of OSA treatment on DR.

Obstructive sleep apnoea predicts the development of preproliferative and proliferative retinopathy in patients with type 2 diabetes:a longitudinal analysis

Background and aims: Diabetic Retinopathy (DR) is a leading cause of blindness. OSA is associated with increased oxidative and nitrosative stress and endothelial dysfunction in patients with type 2 diabetes (T2DM). Hence, it is plausible that OSA can promote the development and progression of DR. Materials and methods: An observational longitudinal study in adults with T2DM. Patients with pre-existing OSA, end-stage renal disease and non-diabetic retinopathy were excluded. OSA (apnoea hypopnea index ≥ 5 events/hour) was assessed by a single overnight home-based cardio-respiratory monitoring (Alice PDX, etc.). DR was assesses using retinal images between 2007 and 2012. Sight threatening retinopathy (STR) was defined as pre-proliferative or proliferative DR, maculopathy or photocoagulation. Advanced DR was defined as pre-proliferative or proliferative DR. Results: 199 patients were included (57.3% men, 47.7% White Europeans). STR and OSA prevalence were 38.7 % and 62.8% respectively. STR preva-lence was higher in patients with OSA (OSA+) compared to those with-out (OSA-) [48.8% vs. 21.6%, p <0.001]. After adjustment for confounders, OSA remained independently associated with STR (OR 3.7, 95%CI 1.6-8.9, p=0.006, maculopathy (OR 4.5, 1.8-11.4, p=0.002) and advanced DR (OR 3.9, 1.02-15.3, p=0.047). Over 4.4±1 years, more OSA+ patients progressed from no or background DR to advanced DR (15.3% vs. 3%, p=0.01). OSA was an independent predictor of advanced DR development after adjustment (OR 6.6, 95%CI 1.2-35.1, p=0.03). OSA did not predict the development of maculopathy. Patients received continuous positive airway pressure treatment were less likely to develop advanced DR. Conclusion: OSA is independently associated with STR and predicts the development of preproliferative and proliferative DR. Interventional studies are needed to assess the impact of OSA treatment on DR.Supported by: NIHR (UK) and The UK Novo Nordisk Research Foundation.

Use of CPAP to Reduce Arterial Stiffness in Moderate-to-Severe Obstructive Sleep Apnoea, Without Excessive Daytime Sleepiness (STIFFSLEEP): an Observational Cohort Study Protocol

INTRODUCTION: Sleepiness is a cardinal symptom in obstructive sleep apnoea (OSA) but most patients have unspecific symptoms. Arterial stiffness, evaluated by pulse wave velocity (PWV), is related to atherosclerosis and cardiovascular (CV) risk. Arterial stiffness was reported to be higher in patients with OSA, improving after treatment with continuous positive airway pressure (CPAP). This study aims to assess whether the same effect occurs in patients with OSA and without sleepiness. METHODS AND ANALYSIS: This observational study assesses the CV effect of CPAP therapy on a cohort of patients with moderate-to-severe OSA; the effect on the subcohorts of sleepy and non-sleepy patients will be compared. A systematic and consecutive sample of patients advised CPAP therapy will be recruited from a single outpatient sleep clinic (Centro Hospitalar de Lisboa Central-CHLC, Portugal). Eligible patients are male, younger than 65 years, with confirmed moderate-to-severe OSA and apnoea-hypopnea index (AHI) above 15/hour. Other sleep disorders, diabetes or any CV disease other than hypertension are exclusion criteria. Clinical evaluation at baseline includes Epworth Sleepiness Scale (ESS), and sleepiness is defined as ESS above 10. OSA will be confirmed by polygraphic study (cardiorespiratory, level 3). Participants are advised to undertake an assessment of carotid-femoral PWV (cf-PWV) and 24 hours evaluation of ambulatory blood pressure monitoring (ABPM), at baseline and after 4 months of CPAP therapy. Compliance and effectiveness of CPAP will be assessed. The main outcome is the variation of cf-PWV over time.

Assessment of Severe Apnoea through Voice Analysis, Automatic Speech, and Speaker Recognition Techniques

This study is part of an ongoing collaborative effort between the medical and the signal processing communities to promote research on applying standard Automatic Speech Recognition (ASR) techniques for the automatic diagnosis of patients with severe obstructive sleep apnoea (OSA). Early detection of severe apnoea cases is important so that patients can receive early treatment. Effective ASR-based detection could dramatically cut medical testing time. Working with a carefully designed speech database of healthy and apnoea subjects, we describe an acoustic search for distinctive apnoea voice characteristics. We also study abnormal nasalization in OSA patients by modelling vowels in nasal and nonnasal phonetic contexts using Gaussian Mixture Model (GMM) pattern recognition on speech spectra. Finally, we present experimental findings regarding the discriminative power of GMMs applied to severe apnoea detection. We have achieved an 81% correct classification rate, which is very promising and underpins the interest in this line of inquiry.

Sleep and wakefulness disturbances in Swiss pharmacy customers

BACKGROUND AND OBJECTIVE: Sleep disturbances are prevalent but often overlooked or underestimated. We suspected that sleep disorders might be particularly common among pharmacy customers, and that they could benefit from counselling. Therefore, we described the prevalence and severity of symptoms associated with sleep and wakefulness disorders among Swiss pharmacy customers, and estimated the need for counselling and treatment. METHODS: In 804 Swiss pharmacies (49% of all community pharmacies) clients were invited to complete the Stanford Sleep Disorders Questionnaire (SDQ), and the Epworth Sleepiness Scale (EPW). The SDQ was designed to classify symptoms of sleep and wakefulness into the four most prevalent disorders: sleep apnoea syndrome (SAS), insomnia in psychiatric disorders (PSY), periodic leg movement disorders/restless legs (RLS) and narcolepsy (NAR). Data were entered into an internet-linked database for analysis by an expert system as a basis for immediate counselling by the pharmacist. RESULTS: Of 4901 participants, 3238 (66.1%) were female, and 1663 (33.9%) were male. The mean age (SD) of females and males was 52.4 (18.05), and 55.1 (17.10) years, respectively. The percentages of female and male individuals above cut-off of SDQ subscales were 11.4% and 19.8% for sleep apnoea, 40.9% and 38.7% for psychiatric sleep disorders, 59.3% and 46.8% for restless legs, and 10.4% and 9.4% for narcolepsy respectively. The prevalence of an Epworth Sleepiness Scale score >11 was 16.5% in females, and 23.9% in males. Reliability assessed by Cronbach's alpha was 0.65 to 0.78 for SDQ subscales, and for the Epworth score. CONCLUSIONS: Symptoms of sleep and wakefulness disorders among Swiss pharmacy customers were highly prevalent. The SDQ and the Epworth Sleepiness Scale score had a satisfactory reliability to be useful for identification of pharmacy customers who might benefit from information and counselling while visiting pharmacies. The internet-based system proved to be a helpful tool for the pharmacist when counselling his customers in terms of diagnostic classification and severity of symptoms associated with the sleeping and waking state.

Screening for sleep disorders in community pharmacies--evaluation of a campaign in Switzerland

BACKGROUND: In 2003 the Swiss federation of pharmacists organized a campaign "sleep disturbances--daytime sleepiness". The goal was to assist pharmacy clients in detecting likely causes of any sleep disturbance or daytime sleepiness through a free of charge screening, and to deliver targeted counselling. For pharmacy practice there are no screening or triage guidelines to assess the severity of sleep and wakefulness disturbances and potential causes for those disturbances. In this paper the outcome of the campaign in terms of feasibility, participation, observed response patterns, sale of over-the-counter (OTC) sleeping pills, and counselling activities is evaluated. METHODS: The Stanford sleep disorders questionnaire and the Epworth sleepiness scale served to identify patterns of symptoms suggestive of four major categories of sleep disorders. The questionnaires were posted on a web-site and the clients' data were entered online in the pharmacies. A report was automatically generated and immediately available online to the pharmacists. The pharmacists documented separately their counselling activities in a pharmacist's activity report. RESULTS: Six hundred and twenty-two (23%) of 2743 pharmacy clients had response patterns suggestive of obstructive sleep apnoea, 418 (15%) of restless-legs-syndrome, 39 (1%) of a sleep disorder potentially associated with a psychiatric condition and 79 (3%) of narcolepsy. An Epworth sleepiness score >10 points was found in 567 (21%). After screening, 2345 (86%) pharmacy clients received targeted counselling. Only 216 (8%) purchased an OTC sleeping pill and 704 (26%) were recommended to consult a physician, but of these, 446 (63%) were already under medical supervision. CONCLUSIONS: The online screening tool for sleep disorders and daytime sleepiness was successfully introduced in Swiss pharmacies. Pharmacies were able to assess the pattern of individual sleep disorders and to identify a possible cause in nearly one-third of the cases.

Evolution of sleep and sleep EEG after hemispheric stroke

The evolution of subjective sleep and sleep electroencephalogram (EEG) after hemispheric stroke have been rarely studied and the relationship of sleep variables to stroke outcome is essentially unknown. We studied 27 patients with first hemispheric ischaemic stroke and no sleep apnoea in the acute (1-8 days), subacute (9-35 days), and chronic phase (5-24 months) after stroke. Clinical assessment included estimated sleep time per 24 h (EST) and Epworth sleepiness score (ESS) before stroke, as well as EST, ESS and clinical outcome after stroke. Sleep EEG data from stroke patients were compared with data from 11 hospitalized controls and published norms. Changes in EST (>2 h, 38% of patients) and ESS (>3 points, 26%) were frequent but correlated poorly with sleep EEG changes. In the chronic phase no significant differences in sleep EEG between controls and patients were found. High sleep efficiency and low wakefulness after sleep onset in the acute phase were associated with a good long-term outcome. These two sleep EEG variables improved significantly from the acute to the subacute and chronic phase. In conclusion, hemispheric strokes can cause insomnia, hypersomnia or changes in sleep needs but only rarely persisting sleep EEG abnormalities. High sleep EEG continuity in the acute phase of stroke heralds a good clinical outcome.

Sleep-related breathing disorder in Duchenne muscular dystrophy: Disease spectrum in the paediatric population

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease with death usually occurring because of respiratory failure. Signs of early respiratory insufficiency are usually first detectable in sleep. Objective: To study the presentation of sleep-related breathing disorder (SRBD) in patients with DMD. Method:> A retrospective review of patients with DMD attending a tertiary paediatric sleep disorder clinic over a 5-year period. Symptoms, lung function and polysomnographic indices were reviewed. Results: A total of 34 patients with DMD were referred for respiratory assessment (1-15 years). Twenty-two (64%) reported sleep-related symptomatology. Forced vital capacity (FVC) was between 12 and 107% predicted (n = 29). Thirty-two progressed to have polysomnography of which 15 were normal studies (median age: 10 years) and 10 (31%) were diagnostic of obstructive sleep apnoea (OSA) (median age: 8 years). A total of 11 patients (32%) showed hypoventilation (median age: 13 years) during the 5-year period and non-invasive ventilation (NIV) was offered to them. The median FVC of this group was 27% predicted. There was a significant improvement in the apnoea/hypopnoea index (AHI) (mean difference = 11.31, 95% CI = 5.91-16.70, P = 0.001) following the institution of NIV. Conclusions: The prevalence of SRBD in DMD is significant. There is a bimodal presentation of SRBD, with OSA found in the first decade and hypoventilation more commonly seen at the beginning of the second decade. Polysomnography is recommended in children with symptoms of OSA, or at the stage of becoming wheelchair-bound. In patients with the early stages of respiratory failure, assessment with polysomnography-identified sleep hypoventilation and assisted in initiating NIV.

Screening of obstructive and central apnoea/hypopnoea in children using variability: A preliminary study

Aim: Polysomnography (PSG) is the current standard protocol for sleep disordered breathing (SDB) investigation in children. Presently, there are limited reliable screening tests for both central (CE) and obstructive (OE) respiratory events. This study compared three indices, derived from pulse oximetry and electrocardiogram ( ECG), with the PSG gold standard. These indices were heart rate (HR) variability, arterial blood oxygen de-saturation (SaO(2)) and pulse transit time (PTT). Methods: 15 children (12 male) from routine PSG studies were recruited (aged 3 - 14 years). The characteristics of the three indices were based on known criteria for respiratory events (RPE). Their estimation singly and in combination was evaluated with simultaneous scored PSG recordings. Results: 215 RPE and 215 tidal breathing events were analysed. For OE, the obtained sensitivity was HR (0.703), SaO(2) (0.047), PTT (0.750), considering all three indices (0) and either of the indices (0.828) while specificity was (0.891), (0.938), (0.922), (0.953) and (0.859) respectively. For CE, the sensitivity was HR (0.715), SaO(2) (0.278), PTT (0.662), considering all indices (0.040) and either of the indices (0.868) while specificity was (0.815), (0.954), (0.901), (0.960) and (0.762) accordingly. Conclusions: Preliminary findings herein suggest that the later combination of these non-invasive indices to be a promising screening method of SDB in children.