Institute for Breathing and Sleep

Melbourne, Australia

Institute for Breathing and Sleep

Melbourne, Australia
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Jackson M.L.,Washington State University | Howard M.E.,Institute for Breathing and Sleep | Barnes M.,Institute for Breathing and Sleep
Progress in Brain Research | Year: 2011

Sleep-related breathing disorders encompass a range of disorders in which abnormal ventilation occurs during sleep as a result of partial or complete obstruction of the upper airway, altered respiratory drive, abnormal chest wall movement, or respiratory muscle function. The most common of these is obstructive sleep apnea (OSA), occurring in both adults and children, and causing significant cognitive and daytime dysfunction and reduced quality of life. OSA patients experience repetitive brief cessation of breathing throughout the night, which causes intermittent hypoxemia (reductions in hemoglobin oxygen levels) and fragmented sleep patterns. These nocturnal events result in excessive daytime sleepiness, and changes in mood and cognition.Chronic excessive sleepiness during the day is a common symptom of sleep-related breathing disorders, which is assessed in sleep clinics both subjectively (questionnaire) and objectively (sleep latency tests). Mood changes are often reported by patients, including irritability, fatigue, depression, and anxiety. A wide range of cognitive deficits have been identified in untreated OSA patients, from attentional and vigilance, to memory and executive functions, and more complex tasks such as simulated driving. These changes are reflected in patient reports of difficulty in concentrating, increased forgetfulness, an inability to make decisions, and falling asleep at the wheel of a motor vehicle. These cognitive changes can also have significant downstream effects on daily functioning. Moderate to severe cases of the disorder are at a higher risk of having a motor vehicle accident, and may also have difficulties at work or school.A number of comorbidities may also influence the cognitive changes in OSA patients, including hypertension, diabetes, and stroke. These diseases can cause changes to neural vasculature and result in neural damage, leading to cognitive impairments. Examination of OSA patients using neuroimaging techniques such as structural magnetic resonance imaging and proton magnetic resonance spectroscopy has observed significant changes to brain structure and metabolism. The downstream effects of neural, cognitive, and daytime functional impairments can be significant if left untreated. A better understanding of the cognitive effects of these disorders, and development of more effective assessment tools for diagnosis, will aid early intervention and improve quality of life of the patient. © 2011 Elsevier B.V.

Peyton P.J.,Austin Health | Peyton P.J.,University of Melbourne | Peyton P.J.,Institute for Breathing and Sleep | Wu C.Y.,University of Melbourne
Anesthesiology | Year: 2014

BACKGROUND:: Inclusion of nitrous oxide in the gas mixture has been implicated in postoperative nausea and vomiting (PONV) in numerous studies. However, these studies have not examined whether duration of exposure was a significant covariate. This distinction might affect the future place of nitrous oxide in clinical practice. METHODS:: PubMed listed journals reporting trials in which patients randomized to a nitrous oxide or nitrous oxide-free anesthetic for surgery were included, where the incidence of PONV within the first 24 postoperative hours and mean duration of anesthesia was reported. Meta-regression of the log risk ratio for PONV with nitrous oxide (lnRR PONVN2O) versus duration was performed. RESULTS:: Twenty-nine studies in 27 articles met the inclusion criteria, randomizing 10,317 patients. There was a significant relationship between lnRR PONVN2O and duration (r = 0.51, P = 0.002). Risk ratio PONV increased 20% per hour of nitrous oxide after 45 min. The number needed to treat to prevent PONV by avoiding nitrous oxide was 128, 23, and 9 where duration was less than 1, 1 to 2, and over 2 h, respectively. The risk ratio for the overall effect of nitrous oxide on PONV was 1.21 (CIs, 1.04-1.40); P = 0.014. CONCLUSIONS:: This duration-related effect may be via disturbance of methionine and folate metabolism. No clinically significant effect of nitrous oxide on the risk of PONV exists under an hour of exposure. Nitrous oxide-related PONV should not be seen as an impediment to its use in minor or ambulatory surgery. © 2014 American Society of Anesthesiologists, Inc.

Quanjer P.H.,Erasmus Medical Center | Pretto J.J.,John Hunter Hospital | Pretto J.J.,University of Newcastle | Brazzale D.J.,Austin Hospital | And 2 more authors.
European Respiratory Journal | Year: 2014

The objective of this study was to redesign the current grading of obstructive lung disease so that it is clinically relevant and free of biases related to age, height, sex and ethnic group. Spirometric records from 17 880 subjects (50.4% female) from hospitals in Australia and Poland, and 21 191 records (53.0% female) from two epidemiological studies (age range 18-95 years) were analysed. We adopted the American Thoracic Society(ATS)/European Respiratory Society (ERS) criteria for airways obstruction based on an forced expiratory volume in 1 s (FEV1)/(forced) vital capacity ((F)VC) ratio below the fifth percentile and graded the severity of pulmonary function impairment using z-scores for FEV1, which signify how many standard deviations a result is from the mean predicted value. Using the lower limit of normal for FEV1/(F)VC and z-scores for FEV1 of -2, -2.5, -3 and -4 to delineate severity grades of airflow limitation leads to close agreement with ATS/ERS severity classifications and removes age, sex and height related bias. The new classification system is simple, easily memorised and clinically valid. It retains previously established associations with clinical outcomes and avoids biases due to the use of per cent predicted FEV1. Combined with the Global Lung Function prediction equations it provides a worldwide diagnostic standard, free of bias due to age, height, sex and ethnic group. Copyright © ERS 2014.

Jordan A.S.,University of Melbourne | Jordan A.S.,Institute for Breathing and Sleep | McSharry D.G.,Harvard University | McSharry D.G.,Letterkenny General Hospital | And 2 more authors.
The Lancet | Year: 2014

Obstructive sleep apnoea is an increasingly common disorder of repeated upper airway collapse during sleep, leading to oxygen desaturation and disrupted sleep. Features include snoring, witnessed apnoeas, and sleepiness. Pathogenesis varies; predisposing factors include small upper airway lumen, unstable respiratory control, low arousal threshold, small lung volume, and dysfunctional upper airway dilator muscles. Risk factors include obesity, male sex, age, menopause, fluid retention, adenotonsillar hypertrophy, and smoking. Obstructive sleep apnoea causes sleepiness, road traffic accidents, and probably systemic hypertension. It has also been linked to myocardial infarction, congestive heart failure, stroke, and diabetes mellitus though not definitively. Continuous positive airway pressure is the treatment of choice, with adherence of 60-70%. Bi-level positive airway pressure or adaptive servo-ventilation can be used for patients who are intolerant to continuous positive airway pressure. Other treatments include dental devices, surgery, and weight loss.

Berlowitz D.J.,Institute for Breathing and Sleep | Shafazand S.,University of Miami
Journal of Clinical Sleep Medicine | Year: 2013

Question: What is the effect of continuous positive airway pressure (CPAP) therapy versus Sham CPAP therapy on neurocognitive function in patients with obstructive sleep apnea (OSA)? Design: Multi-center, randomized, double blinded, sham controlled trial; Identifier: NCT00051363. Allocation: The Data Coordinating Center used a computerized permuted block design to randomize participants to the 2 study arms. Blinding: Participants and most personnel were blinded to treatment assignments, with the exception of site coordinators, polysomnography (PSG) technologists, and the database administrator/data manager. Follow-up period: 6 month follow-up; the first participant was enrolled in 11/2003 and the final completion month was 8/2008. Setting: 5 clinical sleep centers in the United States (academic and private settings). Subjects: 1,098 participants (556 active CPAP, 542 sham CPAP, 35% women, mean age 52 years in active CPAP group) who were diagnosed with OSA with apnea hypopnea index (AHI) ≥ 10 events per hour were randomized. The primary exclusion criteria were: 1) prior OSA treatment with CPAP or surgery; 2) anyone in the household with current/past CPAP use; 3) sleepiness-related automobile accident within past year; 4) oxygen saturation < 75% for > 10% of the diagnostic PSG total sleep time; and/or 5) conditions (including known neurocognitive impairment), disorders, medications, or substances that could potentially affect neurocognitive function and/or alertness. Subjects were recruited primarily from patients scheduled in a regular sleep clinic for evaluation of possible OSA and from local advertising. Although recruitment source was not tracked, it was estimated that initial contact with ∼70% of the subjects occurred as a result of advertisement. Intervention: Participants were randomized to receive CPAP treatment or sham CPAP. Outcomes: The primary outcomes were 3 neurocognitive variables, each representing a neurocognitive domain: 1) Pathfinder Number Test-Total Time assesses attention and psychomotor function; 2) Buschke Selective Reminding Test-Sum Recall assesses verbal learning and memory; and 3) Sustained Working Memory Test-Overall Mid-Day Index assesses an executive and frontal-lobe function (E/F). The secondary outcomes were 7 neurocognitive and 2 sleepiness measures (the maintenance of wakefulness test and the Epworth Sleepiness Scale). The sample size was based on pilot study results for the Pathfinder Number Test. A target of 1,100 total participants (assuming 90% power, 2-sided α = 0.05, 20% study dropout, and allowing for 3 interim analyses) was estimated to achieve an effect size of 0.2, translating to the clinically significant difference of 26 msec in reaction time between the Active and Sham CPAP groups. An effect size of ≥ 0.2 is also a clinically significant between group difference for the other two primary outcome measures. Patient Follow-Up: intention to treat analysis, 79% completed follow-up in active arm, 74% in sham arm. Main Results: There was no statistically significant difference between the groups in the primary outcomes at 6 months. When stratified by measures of OSA severity (AHI or oxygen saturation parameters), the primary E/F variable and one secondary E/F neurocognitive variable revealed transient differences between study arms for those with the most severe OSA that did not persist at 6 months. When primary neurocognitive analyses were restricted to CPAP-adherent individuals (mean nightly active or sham CPAP adherence ≥ 4 h for the 2 months prior to each neurocognitive testing visit), no differences in means were detected between arms for any of the primary outcomes at any visit. Participants in the active CPAP group had a significantly greater ability to remain awake whether measured subjectively by the Epworth Sleepiness Scale or objectively by the maintenance of wakefulness test. Conclusion: In adults with OSA, CPAP therapy did not improve neurocognitive measures at 6 months compared with those on sham CPAP therapy.

Antoniades N.C.,Institute for Breathing and Sleep
Telemedicine journal and e-health : the official journal of the American Telemedicine Association | Year: 2012

Remote in-home monitoring (RM) of symptoms and physiological variables may allow early detection and treatment of exacerbations of chronic obstructive pulmonary disease (COPD). It is unclear whether RM improves patient outcomes or healthcare resource utilization. This study determined whether RM is feasible in patients with COPD and if RM reduces hospital admissions or length of stay (LOS) or improves health-related quality of life (HRQOL). Forty-four patients were randomized to standard best practice care (SBP) (n=22) or SBP+RM (n=22). RM involved daily recording of physiological variables, symptoms, and medication usage. There were no differences (mean±SD, SBP versus SBP+RM) in age (68±8 versus 70±9 years), gender (male:female 10:12 in both groups), or previous computer familiarity (59% versus 50%) between groups. The SBP group had a lower forced expiratory volume in 1 s (0.66±0.24 versus 0.91±0.34 L, p<0.01) and more current smokers (six versus none, p<0.05). There were no differences in number of COPD-related admissions/year (1.5±1.8 versus 1.3±1.7, p=0.76), COPD-related LOS days/year (15.6±19.4 versus 11.4±19.6, p=0.66), total admissions/year (2.2±2.1 versus 2.0±2.3, p=0.86), total LOS days/year (22.1±29.9 versus 21.6±30.4, p=0.88), or HRQOL between the two groups. The addition of RM to SBP was feasible but did not reduce healthcare utilization or improve quality of life in this group of patients already receiving comprehensive respiratory care.

Thornton A.T.,Royal Adelaide Hospital | Singh P.,Royal Adelaide Hospital | Ruehland W.R.,Institute for Breathing and Sleep | Rochford P.D.,Institute for Breathing and Sleep
Sleep | Year: 2012

Study Objectives: To examine the impact of using a nasal pressure sensor only vs the American Academy of Sleep Medicine (AASM) recommended combination of thermal and nasal pressure sensors on (1) the apnea index (AI), (2) the apnea-hypopnea index (AH I), where the AH I is calculated using both AASM definitions of hypopnea, and (3) the accuracy of a diagnosis of obstructive sleep apnea (OSA). Design: Retrospective review of previously scored in-laboratory polysomnography. Setting: A tertiary-hospital clinical sleep laboratory. Patients or Participants: One hundred sixty-four consecutive adult patients with a potential diagnosis of OSA, who were examined during a 3-month period. Interventions: N/A. Measurements and Results: Studies were scored with and without the use of the oronasal thermal sensor. AIs and AH Is, using the nasal pressure sensor alone (AI np and AHI np), were compared with those using both a thermal sensor for the detection of apnea and a nasal pressure transducer for the detection of hypopnea (AI th and AHI th). Comparisons were repeated using the AASM recommended (AASM rec) and alternative (AASM alt) hypopnea definitions. AI was significantly different when measured from the different sensors, with AI np being 51% higher on average. Using the AASM rec hypopnea definition, the mean AHI np was 15% larger than the AHI th; with large interindividual differences and an estimated 9.8% of patients having a false-positive OSA diagnosis at a cutpoint of 15 events and 4.3% at 30 events per hour. Using AASM alt hypopnea definition, the mean AHI np was 3% larger than the AHI th, with estimated false-positive rates of 4.6% and 2.4%, respectively. The false-negative rate was negligible at 0.1% for both hypopnea definitions. Conclusions: This study demonstrates that using only a nasal pressure sensor for the detection of apnea resulted in higher values of AI and AHI than when the AASM recommended thermal sensor was added to detect apnea. When the AASM alt hypopnea definition was used, the differences in AHI and subsequent OSA diagnosis were small and less than when the AASM rec hypopnea definition was used. In situations in which a thermal sensor cannot be used, for example, in limited-channel diagnostic devices, the AHI obtained with a nasal pressure sensor alone differs less from the AHI obtained from a polysomnogram that includes a thermal sensor when the AASM alt definition rather than the AASM rec definition of hypopnea is used. Thus, diagnostic accuracy is impacted both by the absence of the thermal sensor and by the rules used to analyze the polysomnography. Furthermore, where the thermal sensor is unreliable for sections of a study, it is likely that use of the nasal pressure signal to detect apnea will have modest impact.

Berlowitz D.J.,Institute for Breathing and Sleep
The Cochrane database of systematic reviews | Year: 2013

Cervical spinal cord injury (SCI) severely comprises respiratory function due to paralysis and impairment of the respiratory muscles. Various types of respiratory muscle training (RMT) to improve respiratory function for people with cervical SCI have been described in the literature. A systematic review of this literature is needed to determine the effectiveness of RMT (either inspiratory or expiratory muscle training) on pulmonary function, dyspnoea, respiratory complications, respiratory muscle strength, and quality of life for people with cervical SCI. To evaluate the efficacy of RMT versus standard care or sham treatments in people with cervical SCI. We searched the Cochrane Injuries and Cochrane Neuromuscular Disease Groups' Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 1), MEDLINE, EMBASE, CINAHL, ISI Web of Science, PubMed, and clinical trials registries (Australian New Zealand Clinical Trials Registry, ClinicalTrials, Controlled Trials metaRegister) on 5 to 8 March 2013. We handsearched reference lists of relevant papers and literature reviews. We applied no date, language, or publication restrictions. All randomised controlled trials that involved an intervention described as RMT versus a control group using an alternative intervention, placebo, usual care, or no intervention for people with cervical SCI were considered for inclusion. Two review authors independently selected articles for inclusion, evaluated the methodological quality of the studies, and extracted data. We sought additional information from the trial authors when necessary. We presented results using mean differences (MD) (using post-test scores) and 95% confidence intervals (CI) for outcomes measured using the same scale or standardised mean differences (SMD) and 95% CI for outcomes measured using different scales. We included 11 studies with 212 participants with cervical SCI. The meta-analysis revealed a statistically significant effect of RMT for three outcomes: vital capacity (MD mean end point 0.4 L, 95% CI 0.12 to 0.69), maximal inspiratory pressure (MD mean end point 10.50 cm/H2O, 95% CI 3.42 to 17.57), and maximal expiratory pressure (MD mean end point 10.31 cm/H2O, 95% CI 2.80 to 17.82). There was no effect on forced expiratory volume in one second or dyspnoea. We could not combine the results from quality of life assessment tools from three studies for meta-analysis. Respiratory complication outcomes were infrequently reported and thus we could not include them in the meta-analysis. Instead, we described the results narratively. We identified no adverse effects as a result of RMT in cervical SCI. In spite of the relatively small number of studies included in this review, meta-analysis of the pooled data indicates that RMT is effective for increasing respiratory muscle strength and perhaps also lung volumes for people with cervical SCI. Further research is needed on functional outcomes following RMT, such as dyspnoea, cough efficacy, respiratory complications, hospital admissions, and quality of life. In addition, longer-term studies are needed to ascertain optimal dosage and determine any carryover effects of RMT on respiratory function, quality of life, respiratory morbidity, and mortality.

Tamplin J.,University of Melbourne | Berlowitz D.J.,University of Melbourne | Berlowitz D.J.,Institute for Breathing and Sleep
Spinal Cord | Year: 2014

Study design:Systematic reviewObjectives:To determine the effect of respiratory muscle training (RMT) on pulmonary function in tetraplegia.Methods:A comprehensive search of the research literature included MEDLINE, EMBASE, CINAHL, ISI Web of Science, PubMed, the relevant Cochrane and clinical trials registers and hand-searching the reference lists of appropriate papers. There was no language restriction. All randomised controlled trials that involved RMT vs control were considered for inclusion. Two reviewers independently selected articles for inclusion, evaluated the methodological quality and extracted data. Additional information was sought from the authors when necessary.Results: Eleven studies (212 participants) were included. A significant benefit of RMT was revealed for five outcomes: vital capacity (mean difference (95% confidence interval))=0.41(0.17-0.64) l, maximal inspiratory pressure=10.66(3.59, 17.72) cmH 2 O, maximal expiratory pressure=10.31(2.80-17.82) cmH 2 O, maximum voluntary ventilation=17.51(5.20, 29.81) l min -1 and inspiratory capacity=0.35(0.05, 0.65) l. No effect was found for total lung capacity, peak expiratory flow rate, functional residual capacity, residual volume, expiratory reserve volume or forced expiratory volume in 1 second.Conclusion:RMT increases respiratory strength, function and endurance during the period of training. Further research is needed to determine optimum dosages and duration of effect. This article is based in part on a Cochrane review published in the Cochrane Database of Systematic Reviews (CDSR) 2013, DOI:10.1002/14651858.CD008507.pub2. Cochrane reviews are regularly updated as new evidence emerges and in response to feedback, and the CDSR should be consulted for the most recent version of the review. © 2014 International Spinal Cord Society.

Study design:Retrospective study.Objectives:To determine the accuracy of a previously described Dutch clinical prediction rule for ambulation outcome in routine clinical practice.Setting:Adult (⩾18 years) patients who were admitted to the Austin Hospital with a traumatic spinal cord injury between January 2006 and August 2014.Methods:Data from medical records were extracted to determine the score of the Dutch clinical ambulation prediction rule proposed by van Middendorp et al. in 2011. A receiver-operating characteristics (ROC) curve was generated to investigate the performance of the prediction rule. Univariate analyses were performed to investigate which factors significantly influence ambulation after a traumatic spinal cord injury.Results:The area under the ROC curve (AUC) obtained during the current study (0.939, 95% confidence interval (CI) (0.892, 0.986)) was not significantly different from the AUC from the original Dutch clinical prediction model (0.956, 95% CI (0.936, 0.976)). Factors that were found to have a significant influence on ambulation outcome were time spent in the ICU, number of days hospitalised and injury severity. Age at injury initially showed a significant influence on ambulation however, this effect was not apparent after inclusion of the 24 patients who died due to the trauma (and therefore did not walk after their injuries).Conclusion:The Dutch ambulation prediction rule performed similarly in routine clinical practice as in the original, controlled study environment in which it was developed. The potential effect of survival bias in the original model requires further investigation.Spinal Cord advance online publication, 10 November 2015; doi:10.1038/sc.2015.201. © 2015 International Spinal Cord Society

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