Publications by authors named "Philip De Chazal"

Despite decades of research, defining insomnia remains challenging due to its complex and variable nature. Various diagnostic systems emphasize the chronic nature of insomnia and its impact on daily functioning, relying heavily on patient self-reporting due to limitations in objective measures like polysomnography (PSG). Discrepancies between subjective experiences and objective PSG results highlight the need for more nuanced approaches, such as electroencephalogram (EEG) spectral analysis, which reveals distinct patterns of high-frequency activity in individuals with insomnia.

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Article Synopsis
  • * Out of 66 ACS patients, 94% were diagnosed with OSA, with 68% having moderate-to-severe cases; however, common screening questionnaires were not effective in identifying these severe cases.
  • * Although increased arterial stiffness and carotid intima-media thickness were found in patients with moderate-to-severe OSA, these findings were not statistically significant after adjusting for other factors, indicating potential limitations in the study's conclusions.
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Purpose: In light of the reported association between REM-related obstructive sleep apnoea (OSA) and heightened cardiovascular risk, this study aims to compare cardiac autonomic function in patients with REM-OSA and OSA independent of sleep stage. We hypothesized that REM-OSA patients would exhibit higher sympathetic cardiac modulation based on heart rate variability (HRV) profiles.

Methods: HRV was compared between the OSA group (AHI ≥ 5 events/h, n = 252) and the REM-OSA group (AHI ≥ 5 events/h, AHIREM:AHINREM ≥ 2, n = 137).

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Aim: Recent data have identified specific symptom and polysomnographic profiles associated with cardiovascular disease (CVD) in patients with obstructive sleep apnoea (OSA). Our aim was to determine whether these profiles were present at diagnosis of OSA in patients with established CVD and in those with high cardiovascular risk. Participants in the Sydney Sleep Biobank (SSB) database, aged 30-74 years, self-reported presence of CVD (coronary artery disease, cerebrovascular disease, or heart failure).

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Background: There are strong associations between oxygen desaturations and cardiovascular outcomes. Additionally, oxygen resaturation rates are linked to excessive daytime sleepiness independent of oxygen desaturation severity. No studies have yet looked at the independent effects of comorbidities or medications on resaturation parameters.

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Article Synopsis
  • Recent research indicates that sleepy individuals with obstructive sleep apnea (OSA) may face an increased risk of developing cardiovascular disease (CVD).
  • The study compared heart rate variability (HRV) between sleepy and non-sleepy OSA patients to assess cardiac autonomic function, finding that sleepy patients generally had lower HRV values.
  • The results suggest that sleepy patients, especially those with moderate-to-severe OSA, experience reduced parasympathetic activity, which could help explain the connection between sleepiness and heightened CVD risk in OSA.
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Study Objectives: Excessive daytime sleepiness (EDS) is a major symptom of obstructive sleep apnea (OSA). Traditional polysomnographic (PSG) measures only partially explain EDS in OSA. This study analyzed traditional and novel PSG characteristics of two different measures of EDS among patients with OSA.

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  • Recent research highlights the potential of hypoxic burden (HB) as a new predictor for cardiovascular disease (CVD) outcomes, particularly focusing on oxygen desaturation during respiratory events.
  • The study explores how three methods of establishing the SpO2 baseline—pre-event, record-based, and fixed—affect the ability of HB to forecast cardiovascular mortality.
  • Results indicate that the record-based baseline method performed the best, with a significant hazard ratio of 1.83, suggesting it is more effective in predicting CVD risk compared to the other two baseline approaches.
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Polysomnograms (PSGs) contain a wealth of physiological information that is routinely recorded but not utilised in sleep studies. Intermittent hypoxia arising from obstructive sleep apnoea (OSA) events is an important risk in the later development of cardiovascular disease (CVD). Analysis of oximetry patterns from PSG studies may enable early assessment of CVD risk.

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Obstructive sleep apnoea (OSA) is a sleep disorder with repetitive collapse of the upper airway during sleep, which leads to intermittent hypoxic events overnight, adverse neurocognitive, metabolic complications, and ultimately an increased risk of cardiovascular disease (CVD). The standard diagnostic parameter for OSA, apnoea-hypopnoea index (AHI), is inadequate to predict CVD morbidity and mortality, because it focuses only on the frequency of apnoea and hypopnoea events, and fails to reveal other physiological information for the prediction of CVD events. Novel parameters have been introduced to compensate for the deficiencies of AHI.

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Purpose: This study aimed to evaluate the effect of mandibular advancement splint (MAS) therapy on cardiac autonomic function in patients with obstructive sleep apnoea (OSA) using heart rate variability (HRV) analysis.

Methods: Electrocardiograms (ECG) derived from polysomnograms (PSG) of three prospective studies were used to study HRV of patients with OSA before and after MAS treatment. HRV parameters were averaged across the entire ECG signal during N2 sleep using 2-min epochs shifted by 30 s.

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This article presents the near-infrared spectroscopy (NIRS) dataset of cerebral (StOc) and splanchnic (StOs) oxygenation in 29 stable premature infants admitted to a tertiary neonatal intensive care unit who received elective packed red blood cell transfusion (PRBCT) to treat anemia of prematurity. StOc and StOs data were prospectively recorded continuously from at least 4 hours before the beginning of PRBCT until 24 hours after its completion, using a 4-wavelength near-infrared spectroscopy (NIRS) monitor (FORE-SIGHT® absolute cerebral oximeter, CASMED, Branford, Connecticut, 06405 USA). StO data were downloaded as an analog output at a sampling rate of 1000Hz and aligned along the time axis in LabChart reader format (.

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Background: Splanchnic-cerebral oxygenation ratio (SCOR), the ratio of splanchnic tissue oxygen (StO s) to simultaneously measured cerebral tissue oxygen (StO c), has been described as a surrogate to detect impaired splanchnic oxygenation associated with hypoperfusion status such as necrotizing enterocolitis. This concept is based on the presumption that any change in SCOR indicates a corresponding change in splanchnic tissue oxygenation as the numerator, whereas cerebral tissue oxygenation as the denominator remains stable. However, it is questionable to utilise this concept to detect splanchnic oxygenation changes in the context of packed red blood cell transfusion (PRBCT).

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Study Objectives: Autonomic function is impaired in obstructive sleep apnea (OSA) and may mediate the association between OSA and cardiovascular risk. We investigated the effect of OSA therapy on autonomic function through a systematic review and meta-analysis of intervention studies.

Methods: A systematic search using three databases (Medline, Embase, and Scopus) was performed up to December 9, 2020.

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Study Objectives: Intermittent hypoxia is a key mechanism linking Obstructive Sleep Apnea (OSA) to cardiovascular disease (CVD). Oximetry analysis could enhance understanding of which OSA phenotypes are associated with CVD risk. The aim of this study was to compare associations of different oximetry patterns with incident CVD in men and women with OSA.

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Background: It is well established that counter-regulation to hypoxia follows a hierarchical pattern, with brain-sparing in preference to peripheral tissues. In contrast, it is unknown if the same hierarchical sequence applies to recovery from hypoxia after correction of anemia with packed red blood cell transfusion (PRBCT).

Objective: To understand the chronology of cerebral and splanchnic tissue oxygenation resulting after correction of anemia by PRBCT in preterm infants using near-infrared spectroscopy (NIRS).

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Purpose: The autonomic nervous system may mediate acute apnoea-induced atrial fibrillation (AF). We compared cardiac autonomic function in paroxysmal atrial fibrillation (PAF) patients with and without obstructive sleep apnoea (OSA).

Methods: Case control study of 101 patients with PAF recruited at two tertiary centres.

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A new method for calculation of an overnight oximetry signal metric which is predictive of cardiovascular disease (CVD) outcomes in individuals undergoing an overnight sleep test is presented. The metric - the respiratory event desaturation transient area (REDTA) - quantifies the desaturation associated with respiratory events. Data from the Sleep Heart Health Study, which includes overnight oximetry signals and long-term CVD outcomes, was used to develop and test the parameter.

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We propose a novel method for deriving ground truth labels for regression problems that considers the precision of annotators separately for each label. This method ensures that higher performing annotators contribute more to the final landmark position which is in contrast to conventional methods that assume all annotators are equally accurate in completing the set task. In addition to describing the novel method, a set of preliminary experimental results is also provided, comparing the performance of the precision method to that of the global mean.

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Knowledge regarding the site-of-collapse in the upper airway in obstructive sleep apnoea (OSA) has implications for treatment options and their outcomes. However, current methods to identify the site-of-collapse are not suitable for clinical practice due to the invasive nature, the time/cost of the tests and the inconsistency of the obstruction site identified with natural and drug-induced sleep. In this study, we adopted an unsupervised algorithm to identify the predominant site-of-collapse of the upper airway during natural sleep using nocturnal audio recordings.

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Obstructive sleep apnea (OSA) is a highly prevalent and underdiagnosed medical condition, which is associated with various cardiovascular and metabolic diseases. The current mainstay of therapy is continuous positive airway pressure (CPAP); however, CPAP is known to be poorly accepted and tolerated by patients. In randomized controlled trials evaluating CPAP in cardiovascular outcomes, the average usage was less than 3.

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Study Objectives: Acoustic analysis of isolated events and snoring by previous researchers suggests a correlation between individual acoustic features and individual site of collapse events. In this study, we hypothesized that multiparameter evaluation of snore sounds during natural sleep would provide a robust prediction of the predominant site of airway collapse.

Methods: The audio signals of 58 obstructive sleep apnea patients were recorded simultaneously with full-night polysomnography.

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Obstructive sleep apnea (OSA) is an independent risk factor for hypertension and cardiovascular disease. Effects of OSA on the autonomic nervous system may mediate this association. We performed a systematic literature review to determine the profile of autonomic function associated with OSA.

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Study Objectives: Patients with obstructive sleep apnea (OSA) exhibit heterogeneous heart rate variability (HRV) during wakefulness and sleep. We investigated the influence of OSA severity on HRV parameters during wakefulness in a large international clinical sample.

Methods: 1247 subjects (426 without OSA and 821 patients with OSA) were enrolled from the Sleep Apnea Global Interdisciplinary Consortium.

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