Characterisation of Symptom and Polysomnographic Profiles Associated with Cardiovascular Risk in a Sleep Clinic Population with Obstructive Sleep Apnoea

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). In those without established CVD, the Framingham Risk Score (FRS) estimated 10-year absolute CVD risk, categorised as "low" (<6%), "intermediate" (6-20%), or "high" (>20%). Groups were compared on symptom and polysomnographic variables.

Results

629 patients (68% male; mean age 54.3 years, SD 11.6; mean BMI 32.3 kg/m2, SD 8.2) were included. CVD was reported in 12.2%. A further 14.3% had a low risk FRS, 38.8% had an intermediate risk FRS, and 34.7% had a high risk FRS. Groups differed with respect to age, sex and BMI. OSA severity increased with established CVD and increasing FRS. The symptom of waking too early was more prevalent in the higher FRS groups (p=0.004). CVD and FRS groups differed on multiple polysomnographic variables; however, none of these differences remained significant after adjusting for age, sex, and BMI.

Conclusion

Higher CVD risk was associated with waking too early in patients with OSA. Polysomnographic variations between groups were explained by demographic differences. Further work is required to explore the influence of OSA phenotypic characteristics on susceptibility to CVD.

Heart Rate Variability Analysis in Obstructive Sleep Apnoea Patients with Daytime Sleepiness

STUDY OBJECTIVES

Recent studies suggest sleepy patients with OSA are at higher risk for incident cardiovascular disease. This study assessed cardiac autonomic function in sleepy versus non-sleepy patients with obstructive sleep apnoea (OSA) using heart rate variability (HRV) analysis. We hypothesised that HRV profiles of sleepy patients would indicate higher cardiovascular risk.

METHODS

Electrocardiograms (ECG) derived from polysomnograms (PSG) collected by the Sydney Sleep Biobank were used to study HRV in groups of sleepy (ESS≥10) and non-sleepy OSA patients (ESS<10). HRV parameters were averaged across available ECG signal during N2 sleep.

RESULTS

A total of 421 patients were evaluated, with mean age of 54 (14) years, body mass index (BMI) of 33 (9) kg/m2, apnoea hypopnoea index (AHI) of 21 (28) events/h and, 66% male. The sleepy group consisted of 119 patients, and the non-sleepy group 302 patients. Sleepy patients exhibited lower HRV values for: root mean square successive difference (RMSSD, p= 0.028); total power (TP, p= 0.031); absolute low frequency (LF, p= 0.045); and high frequency (HF, p= 0.010) power compared to Non-Sleepy patients. Sleepy patients with moderate to severe OSA exhibited lower HRV values for: (RMSSD, p= 0.045; TP, p= 0.052) ; absolute LF (p= 0.051); and HF power (p= 0.025). There were no differences in other time and frequency domain HRV markers.

CONCLUSIONS

This study shows a trend towards parasympathetic withdrawal in sleepy OSA patients, particularly in moderate to severe cases, lending mechanistic support to the link between the sleepy phenotype and CVD risk in OSA.

A comparison of two obesity-related hypoventilation disorders: Impact on sleep, quality of life and neurocognitive outcomes and the effects of positive airway pressure therapy

Study Objectives

Symptom impact and neurocognitive function have not been previously compared between patients with obesity-associated hypoventilation disorders (obesity hypoventilation syndrome [OHS]) and hypoventilation in the setting of obesity and obstructive airways disease (OHAD). The aim of this study is to compare baseline sleep-related symptoms, health-related quality of life, and neurocognitive function between OHS and OHAD and the impact of PAP therapy on these outcomes.

Methods

Epworth Sleepiness Scale (ESS), Pittsburgh Sleepiness Quality Index (PSQI), SF36, and various neurocognitive tests, in addition to anthropometric, polysomnography, lung function, and blood gas data from participants with OHS and participants with OHAD, were included in the analysis. These data were originally collected in their respective randomized clinical trials, comparing the efficacy of different PAP modes (bilevel PAP vs. CPAP) in resolving hypercapnia. Between groups (OHS vs OHAD), pre- and post-treatment (with 3 months of positive airway pressure) comparisons were made using linear mixed modeling.

Results

45 OHS participants (mean age 51 years old, 33% female, BMI 52 kg/m2, FER 0.81, PaCO2 54 mmHg, AHI 87/h) and 32 OHAD participants (mean age 61years old, 31% female, BMI 43kg/m2, FER 0.60, PaCO2 54 mmHg, AHI 59/h) were included in the analysis. Both OHS and OHAD had similar baseline ESS (14(5.6) vs. 12(5.4)), Global PSQI (10(3.2) vs. 11(4.8)), SF36 and neurocognitive test performances (other than OHAD had lower digit symbol substitution test performance). Treatment with PAP therapy resulted in similar ESS, Global PSQI, and SF36 improvements in both groups. Neurocognitive performance did not significantly improve after PAP therapy in either group.

Conclusions

The symptom impact between two separate hypoventilation disorders (OHS and OHAD), in terms of sleepiness, sleep quality, quality of life, and cognitive function, were similar. OHS and OHAD had similar treatment responses in these parameters after 3 months of PAP therapy.Nocturnal ventilatory support in OHS.

Online Education Improves Confidence in Mechanical Insufflation-Exsufflation

BACKGROUND

Mechanical insufflation-exsufflation (MI-E) is a cough augmentation technique used to support people with an ineffective cough. MI-E can be complex due to the number of different pressure, flow, and temporal setting adjustments needed to optimize cough efficacy. Many clinicians identify inadequate training, limited experience, and low confidence as barriers to MI-E use. The purpose of this study was to determine if an online education course could improve confidence and competence in the delivery of MI-E.

METHODS

An e-mail invitation to participate was disseminated to physiotherapists with a caseload that involved airway clearance for adults. The exclusion criteria were self-reported confidence and clinical expertise in MI-E. The education was created by physiotherapists with extensive experience in the provision of MI-E. The education material reviewed theoretical and practical components and was designed to take 6 h to complete. Physiotherapists were randomized to either the intervention group, who had 3 weeks of access to the education or the control group who received no intervention. Respondents in both groups completed a baseline and a post-intervention questionnaire by using visual analog scales, 0 to 10, with the primary outcomes being confidence in the prescription and confidence in the application of MI-E. Ten multiple-choice questions that covered key components of MI-E fundamentals were also completed at baseline and post-intervention.

RESULTS

The intervention group had a significant improvement in the visual analog scale after the education period with a between-group difference of mean 3.6 (95% CI 4.5 to 2.7) for prescription confidence and mean 2.9 (95% CI 3.9 to 1.9) for application confidence. There was also an improvement in the multiple-choice questions with a between-group difference of mean 3.2 (95% CI 4.3 to 2).

CONCLUSIONS

Access to an evidence-based online education course improved confidence in the prescription and application of MI-E, and may be a valuable tool for training clinicians in the application of MI-E.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Cardiopulmonary coupling and serum cardiac biomarkers in obesity hypoventilation syndrome and obstructive sleep apnea with morbid obesity

STUDY OBJECTIVES

The main cause of death in patients with obesity hypoventilation syndrome (OHS) is cardiac rather than respiratory failure. Here, we investigated autonomic-respiratory coupling and serum cardiac biomarkers in patients with OHS and obstructive sleep apnea (OSA) with comparable body mass index (BMI) and apnea-hypopnea index (AHI).

METHODS

Cardiopulmonary coupling (CPC) and cyclic variation of heart rate (CVHR) analysis was performed on the electrocardiogram signal from the overnight polysomnogram. Cardiac serum biomarkers were obtained in patients with OHS and OSA with a BMI > 40kg/m². Samples were obtained at baseline and after 3 months of positive airway pressure (PAP) therapy in both groups.

RESULTS

Patients with OHS (n=15) and OSA (n=36) were recruited. No group differences in CPC, CVHR and serum biomarkers were observed at baseline and after 3 months of PAP therapy. An improvement in several CPC metrics, including the sleep apnea index, unstable sleep (low frequency coupling and elevated low frequency coupling narrow band [e-LFC_NB]) and CVHR were observed in both groups with PAP use. However, distinct differences in response characteristics were noted. e-LFC_NB coupling correlated with highly sensitive troponin (hs-troponin-T, p<0.05) in the combined cohort. Baseline hs-troponin-T inversely correlated with awake oxygen saturation in the OHS group (p<0.05).

CONCLUSIONS

PAP therapy can significantly improve CPC stability in obese patients with OSA or OHS, with key differences. e-LFC_NB may function as a surrogate biomarker for early subclinical cardiac disease. Low awake oxygen saturation could also increase this biomarker in OHS.

CLINICAL TRIAL REGISTRATION

Registry: Australian New Zealand Clinical Trials Registry; Name: Obesity Hypoventilation Syndrome and Neurocognitive Dysfunction; URL: https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=367492; Identifier: ACTRN12615000122550.

Cardiovascular disease in obesity hypoventilation syndrome - A review of potential mechanisms and effects of therapy

Cardiovascular disease is common in patients with obesity hypoventilation syndrome (OHS) and accounts in part for their poor prognosis. This narrative review article examines the epidemiology of cardiovascular disease in obesity hypoventilation syndrome, explores possible contributing factors and the effects of therapy. All studies that included cardiovascular outcomes and biomarkers were included. Overall, there is a higher burden of cardiovascular disease and cardiovascular risk factors among patients with obesity hypoventilation syndrome. In addition to obesity and sleep-disordered breathing, there are several other pathophysiological mechanisms that contribute to higher cardiovascular morbidity and mortality in OHS. There is evidence emerging that positive airway pressure therapy and weight loss have beneficial effects on the cardiovascular system in obesity hypoventilation syndrome patients, but further research is needed to clarify whether this translates to clinically important outcomes.

Long-Term Noninvasive Ventilation in Chronic Stable Hypercapnic Chronic Obstructive Pulmonary Disease. An Official American Thoracic Society Clinical Practice Guideline

Background: Noninvasive ventilation (NIV) is used for patients with chronic obstructive pulmonary disease (COPD) and chronic hypercapnia. However, evidence for clinical efficacy and optimal management of therapy is limited.

Target Audience: Patients with COPD, clinicians who care for them, and policy makers.

Methods: We summarized evidence addressing five PICO (patients, intervention, comparator, and outcome) questions. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach was used to evaluate the certainty in evidence and generate actionable recommendations. Recommendations were formulated by a panel of pulmonary and sleep physicians, respiratory therapists, and methodologists using the Evidence-to-Decision framework.

Recommendations:1) We suggest the use of nocturnal NIV in addition to usual care for patients with chronic stable hypercapnic COPD (conditional recommendation, moderate certainty); 2) we suggest that patients with chronic stable hypercapnic COPD undergo screening for obstructive sleep apnea before initiation of long-term NIV (conditional recommendation, very low certainty); 3) we suggest not initiating long-term NIV during an admission for acute-on-chronic hypercapnic respiratory failure, favoring instead reassessment for NIV at 2–4 weeks after resolution (conditional recommendation, low certainty); 4) we suggest not using an in-laboratory overnight polysomnogram to titrate NIV in patients with chronic stable hypercapnic COPD who are initiating NIV (conditional recommendation, very low certainty); and 5) we suggest NIV with targeted normalization of Pa_CO2 in patients with hypercapnic COPD on long-term NIV (conditional recommendation, low certainty).

Conclusions: This expert panel provides evidence-based recommendations addressing the use of NIV in patients with COPD and chronic stable hypercapnic respiratory failure.

The Effect of Hospital Discharge with Empiric Noninvasive Ventilation on Mortality in Hospitalized Patients with Obesity Hypoventilation Syndrome. An Individual Patient Data Meta-Analysis

Rationale: Hospitalized patients with acute-on-chronic hypercapnic respiratory failure due to obesity hypoventilation syndrome (OHS) have increased short-term mortality. It is unknown whether prescribing empiric positive airway pressure (PAP) at the time of hospital discharge reduces mortality compared with waiting for an outpatient evaluation (i.e., outpatient sleep study and outpatient PAP titration).Objectives: An international, multidisciplinary panel of experts developed clinical practice guidelines on OHS for the American Thoracic Society. The guideline panel asked whether hospitalized adult patients with acute-on-chronic hypercapnic respiratory failure suspected of having OHS, in whom the diagnosis has not yet been made, should be discharged from the hospital with or without empiric PAP treatment until the diagnosis of OHS is either confirmed or ruled out.Methods: A systematic review with individual patient data meta-analyses was performed to inform the guideline panel's recommendation. Grading of Recommendations, Assessment, Development, and Evaluation was used to summarize evidence and appraise quality.Results: The literature search identified 2,994 articles. There were no randomized trials. Ten studies met a priori study selection criteria, including two nonrandomized comparative studies and eight nonrandomized noncomparative studies. Individual patient data on hospitalized patients who survived to hospital discharge were obtained from nine of the studies and included a total of 1,162 patients (1,043 discharged with PAP and 119 discharged without PAP). Empiric noninvasive ventilation was prescribed in 91.5% of patients discharged on PAP, and the remainder received empiric continuous PAP. Discharge with PAP reduced mortality at 3 months (relative risk 0.12, 95% confidence interval 0.05-0.30, risk difference -14.5%). Certainty in the estimated effects was very low.Conclusions: Hospital discharge with PAP reduces mortality following acute-on-chronic hypercapnic respiratory failure in patients with OHS or suspected of having OHS. Well-designed clinical trials are needed to confirm this finding.

Evaluation and Management of Obesity Hypoventilation Syndrome. An Official American Thoracic Society Clinical Practice Guideline

Background: The purpose of this guideline is to optimize evaluation and management of patients with obesity hypoventilation syndrome (OHS).

Methods: A multidisciplinary panel identified and prioritized five clinical questions. The panel performed systematic reviews of available studies (up to July 2018) and followed the Grading of Recommendations, Assessment, Development, and Evaluation evidence-to-decision framework to develop recommendations. All panel members discussed and approved the recommendations.

Recommendations: After considering the overall very low quality of the evidence, the panel made five conditional recommendations. We suggest that: 1) clinicians use a serum bicarbonate level <27 mmol/L to exclude the diagnosis of OHS in obese patients with sleep-disordered breathing when suspicion for OHS is not very high (<20%) but to measure arterial blood gases in patients strongly suspected of having OHS, 2) stable ambulatory patients with OHS receive positive airway pressure (PAP), 3) continuous positive airway pressure (CPAP) rather than noninvasive ventilation be offered as the first-line treatment to stable ambulatory patients with OHS and coexistent severe obstructive sleep apnea, 4) patients hospitalized with respiratory failure and suspected of having OHS be discharged with noninvasive ventilation until they undergo outpatient diagnostic procedures and PAP titration in the sleep laboratory (ideally within 2–3 mo), and 5) patients with OHS use weight-loss interventions that produce sustained weight loss of 25% to 30% of body weight to achieve resolution of OHS (which is more likely to be obtained with bariatric surgery).

Conclusions: Clinicians may use these recommendations, on the basis of the best available evidence, to guide management and improve outcomes among patients with OHS.

Slow-frequency electroencephalography activity during wake and sleep in obesity hypoventilation syndrome

Study Objective

Neurophysiological activity during wake and sleep states in obesity hypoventilation (OHS) and its relationship with neurocognitive function is not well understood. This study compared OHS with equally obese obstructive sleep apnea (OSA) patients, with similar apnea-hypopnea indices.

Methods

Resting wake and overnight sleep electroencephalography (EEG) recordings, neurocognitive tests, and sleepiness, depression and anxiety scores were assessed before and after 3 months of positive airway pressure (PAP) therapy in 15 OHS and 36 OSA patients.

Results

Pretreatment, greater slow frequency EEG activity during wake and sleep states (increased delta-alpha ratio during sleep, and theta power during awake) was observed in the OHS group compared to the OSA group. EEG slowing was correlated with poorer performance on the psychomotor vigilance task (slowest 10% of reciprocal reaction times, psychomotor vigilance test [PVT SRRT], primary outcome), and worse sleep-related hypoxemia measures in OHS. There was no between-group significant difference in PVT performance at pre or post-treatment. Similarly, despite both groups demonstrating improved sleepiness, anxiety and depression scores with PAP therapy, there were no differences in treatment response between the OSA and OHS groups.

Conclusion

Patients with OHS have greater slow frequency EEG activity during sleep and wake than equally obese patients with OSA. Greater EEG slowing was associated with worse vigilance and lower oxygenation during sleep.

Clinical Trial

This trial was registered with the Australian and New Zealand Clinical Trials Registry (ACTRN12615000122550).

Obesity Hypoventilation Syndrome: Choosing the Appropriate Treatment of a Heterogeneous Disorder

The obesity hypoventilation syndrome (OHS) is associated with significant morbidity and increased mortality compared with simple obesity and eucapnic obstructive sleep apnea. Accurate diagnosis and commencement of early and appropriate management is fundamental in reducing the significant personal and societal burdens this disorder poses. Sleep disordered breathing is a major contributor to the developmental of sleep and awake hypercapnia, which characterizes OHS, and is effectively addressed through the use of positive airway pressure (PAP) therapy. This article reviews the current evidence supporting different modes of PAP currently used in managing these individuals.

Non-invasive ventilation for cystic fibrosis

BACKGROUND

Non-invasive ventilation may be a means to temporarily reverse or slow the progression of respiratory failure in cystic fibrosis by providing ventilatory support and avoiding tracheal intubation. Using non-invasive ventilation, in the appropriate situation or individuals, can improve lung mechanics through increasing airflow and gas exchange and decreasing the work of breathing. Non-invasive ventilation thus acts as an external respiratory muscle. This is an update of a previously published review.

OBJECTIVES

To compare the effect of non-invasive ventilation versus no non-invasive ventilation in people with cystic fibrosis for airway clearance, during sleep and during exercise.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We searched the reference lists of each trial for additional publications possibly containing other trials.Most recent search: 08 August 2016.

SELECTION CRITERIA

Randomised controlled trials comparing a form of pressure preset or volume preset non-invasive ventilation to no non-invasive ventilation used for airway clearance or during sleep or exercise in people with acute or chronic respiratory failure in cystic fibrosis.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trials for inclusion criteria and methodological quality, and extracted data.

MAIN RESULTS

Ten trials met the inclusion criteria with a total of 191 participants. Seven trials evaluated single treatment sessions, one evaluated a two-week intervention, one evaluated a six-week intervention and one a three-month intervention. It is only possible to blind trials of airway clearance and overnight ventilatory support to the outcome assessors. In most of the trials we judged there was an unclear risk of bias with regards to blinding due to inadequate descriptions. The six-week trial was the only one judged to have a low risk of bias for all other domains. One single intervention trial had a low risk of bias for the randomisation procedure with the remaining trials judged to have an unclear risk of bias. Most trials had a low risk of bias with regard to incomplete outcome data and selective reporting.Six trials (151 participants) evaluated non-invasive ventilation for airway clearance compared with an alternative chest physiotherapy method such as the active cycle of breathing techniques or positive expiratory pressure. Three trials used nasal masks, one used a nasal mask or mouthpiece and one trial used a face mask and in one trial it is unclear. Three of the trials reported on one of the review's primary outcome measures (quality of life). Results for the reviews secondary outcomes showed that airway clearance may be easier with non-invasive ventilation and people with cystic fibrosis may prefer it. We were unable to find any evidence that non-invasive ventilation increases sputum expectoration, but it did improve some lung function parameters.Three trials (27 participants) evaluated non-invasive ventilation for overnight ventilatory support compared to oxygen or room air using nasal masks (two trials) and nasal masks or full face masks (one trial). Trials reported on two of the review's primary outcomes (quality of life and symptoms of sleep-disordered breathing). Results for the reviews secondary outcome measures showed that they measured lung function, gas exchange, adherence to treatment and preference, and nocturnal transcutaneous carbon dioxide. Due to the small numbers of participants and statistical issues, there were discrepancies in the results between the RevMan and the original trial analyses. No clear differences were found between non-invasive ventilation compared with oxygen or room air except for exercise performance, which significantly improved with non-invasive ventilation compared to room air over six weeks.One trial (13 participants) evaluated non-invasive ventilation on exercise capacity (interface used was unclear) and did not reported on any of the review's primary outcomes. The trial found no clear differences between non-invasive ventilation compared to no non-invasive ventilation for any of our outcomes.Three trials reported on adverse effects. One trial, evaluating non-invasive ventilation for airway clearance, reported that a participant withdrew at the start of the trial due to pain on respiratory muscle testing. One trial evaluating non-invasive ventilation for overnight support reported that one participant could not tolerate an increase in inspiratory positive airway pressure. A second trial evaluating non-invasive ventilation in this setting reported that one participant did not tolerate the non-invasive ventilation mask, one participant developed a pneumothorax when breathing room air and two participants experienced aerophagia which resolved when inspiratory positive airway pressure was decreased.

AUTHORS' CONCLUSIONS

Non-invasive ventilation may be a useful adjunct to other airway clearance techniques, particularly in people with cystic fibrosis who have difficulty expectorating sputum. Non-invasive ventilation, used in addition to oxygen, may improve gas exchange during sleep to a greater extent than oxygen therapy alone in moderate to severe disease. The effect of NIV on exercise is unclear. These benefits of non-invasive ventilation have largely been demonstrated in single treatment sessions with small numbers of participants. The impact of this therapy on pulmonary exacerbations and disease progression remain unclear. There is a need for long-term randomised controlled trials which are adequately powered to determine the clinical effects of non-invasive ventilation in cystic fibrosis airway clearance and exercise.

How will cancer survivors use survivorship care plans?

BACKGROUND

Survivorship care plans (SCPs) are internationally endorsed as an important tool to enhance post-treatment survivorship care. To support broad implementation of SCPs, we investigated survivors' preferences regarding SCPs.

MATERIAL AND METHODS

The study was conducted at a comprehensive cancer center. Eligible patients from 10 clinical services, generally up to 12 months following end of treatment (EOT) were approached in clinics or via telephone. A purpose-designed survey assessed survivors' intended use of a SCP and preferences regarding format and content. Intended minimum sample size of 200.

RESULTS

Two hundred and thirty surveys were returned (response rate 68%). Of the 230 participants, over 55% had completed treatment within six months, 35% between six and 12 months, and 10% were receiving ongoing treatments. Most (82%) had not received a SCP and more than one third (42%) reported receiving no information resources at EOT. Almost all (98%) desired further information. Most common information elements desired in a SCP: 'list of symptoms to watch out for and report' (76%), 'summary of treatment received' (70%) and 'things I can do to look after myself' (67%). Most common suggested uses were as: 'a record of cancer treatment' (63%), 'a reminder of things to do to look after myself ' (57%) and 'to help me understand my cancer experience' (56%). Over half (52%) would share the information with their general practitioner. Most indicated preference for paper-based SCPs (91%). There was support for both brief (36%) and detailed versions (42%). Over half requested the information be delivered in a face-to-face discussion with a health professional. Regular telephone support from the treating health care team was most commonly suggested as an additional service to support survivors after EOT.

CONCLUSIONS

Although similar to international findings, results suggest alternate ways of providing the information that survivors desire. Most desired SCP elements have been defined. A flexible approach to SCP interventions is justified.

Non-invasive ventilation used as an adjunct to airway clearance treatments improves lung function during an acute exacerbation of cystic fibrosis: a randomised trial

QUESTION

During an acute exacerbation of cystic fibrosis, is non-invasive ventilation beneficial as an adjunct to the airway clearance regimen?

DESIGN

Randomised controlled trial with concealed allocation and intention-to-treat analysis.

PARTICIPANTS

Forty adults with moderate to severe cystic fibrosis lung disease and who were admitted to hospital for an acute exacerbation.

INTERVENTION

Comprehensive inpatient care (control group) compared to the same care with the addition of non-invasive ventilation during airway clearance treatments from Day 2 of admission until discharge (experimental group).

OUTCOME MEASURES

Lung function and subjective symptom severity were measured daily. Fatigue was measured at admission and discharge on the Schwartz Fatigue Scale from 7 (no fatigue) to 63 (worst fatigue) points. Quality of life and exercise capacity were also measured at admission and discharge. Length of admission and time to next hospital admission were recorded.

RESULTS

Analysed as the primary outcome, the experimental group had a greater rate of improvement in forced expiratory volume in 1 second (FEV1) than the control group, but this was not statistically significant (MD 0.13% predicted per day, 95% CI -0.03 to 0.28). However, the experimental group had a significantly higher FEV1 at discharge than the control group (MD 4.2% predicted, 95% CI 0.1 to 8.3). The experimental group reported significantly lower levels of fatigue on the Schwartz fatigue scale at discharge than the control group (MD 6 points, 95% CI 1 to 11). There was no significant difference between the experimental and control groups in subjective symptom severity, quality of life, exercise capacity, length of hospital admission or time to next hospital admission.

CONCLUSION

Among people hospitalised for an acute exacerbation of cystic fibrosis, the use of non-invasive ventilation as an adjunct to the airway clearance regimen significantly improves FEV1 and fatigue.

TRIAL REGISTRATION

ANZCTR 12605000437662.

Sleep disorders and respiratory function in amyotrophic lateral sclerosis

Sleep disorders in amyotrophic lateral sclerosis (ALS) present a significant challenge to the management of patients. Issues include the maintenance of adequate ventilatory status through techniques such as non-invasive ventilation, which has the ability to modulate survival and improve patient quality of life. Here, a multidisciplinary approach to the management of these disorders is reviewed, from concepts about the underlying neurobiological basis, through to current management approaches and future directions for research.

Hypercapnia is a key correlate of EEG activation and daytime sleepiness in hypercapnic sleep disordered breathing patients

BACKGROUND

The key determinants of daytime drowsiness in sleep disordered breathing (SDB) are unclear. Hypercapnia has not been examined as a potential contributor due to the lack of reliable measurement during sleep. To overcome this limitation, we studied predominantly hypercapnic SDB patients to investigate the role of hypercapnia on EEG activation and daytime sleepiness.

METHODS

We measured overnight polysomnography (PSG), arterial blood gases, and Epworth Sleepiness Scale in 55 severe SDB patients with obesity hypoventilation syndrome or overlap syndrome (COPD+ obstructive sleep apnea) before and ∼3 months after positive airway pressure (PAP) treatment. Quantitative EEG analyses were performed, and the Delta/ Alpha ratio was used as an indicator of EEG activation.

RESULTS

After the PAP treatment, these patients showed a significant decrease in their waking pCO(2), daytime sleepiness, as well as all key breathing/oxygenation parameters during sleep. Overnight Delta/Alpha ratio of EEG was significantly reduced. There is a significant cross-correlation between a reduced wake pCO(2), a faster (more activated) sleep EEG (reduced Delta/Alpha ratio) and reduced daytime sleepiness (all p < 0.05) with PAP treatment. Multiple regression analyses showed the degree of change in hypercapnia to be the only significant predictor for both ESS and Delta/ Alpha ratio.

CONCLUSIONS

Hypercapnia is a key correlate of EEG activation and daytime sleepiness in hypercapnic SDB patients. The relationship between hypercapnia and sleepiness may be mediated by reduced neuro-electrical brain activity.

Non-invasive ventilation during exercise training for people with chronic obstructive pulmonary disease

BACKGROUND

Exercise training as a component of pulmonary rehabilitation improves health-related quality of life (HRQL) and exercise capacity in people with chronic obstructive pulmonary disease (COPD). However, some individuals may have difficulty performing exercise at an adequate intensity. Non-invasive ventilation (NIV) during exercise improves exercise capacity and dyspnoea during a single exercise session. Consequently, NIV during exercise training may allow individuals to exercise at a higher intensity, which could lead to greater improvement in exercise capacity, HRQL and physical activity.

OBJECTIVES

To determine whether NIV during exercise training (as part of pulmonary rehabilitation) affects exercise capacity, HRQL and physical activity in people with COPD compared with exercise training alone or exercise training with sham NIV.

SEARCH METHODS

We searched the following databases between January 1987 and November 2013 inclusive: The Cochrane Airways Group specialised register of trials, AMED, CENTRAL, CINAHL, EMBASE, LILACS, MEDLINE, PEDro, PsycINFO and PubMed. 

SELECTION CRITERIA

Randomised controlled trials that compared NIV during exercise training versus exercise training alone or exercise training with sham NIV in people with COPD were considered for inclusion in this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion in the review, extracted data and assessed risk of bias. Primary outcomes were exercise capacity, HRQL and physical activity; secondary outcomes were training intensity, physiological changes related to exercise training, dyspnoea, dropouts, adverse events and cost.

MAIN RESULTS

Six studies involving 126 participants who completed the study protocols were included. Most studies recruited participants with severe to very severe COPD (mean forced expiratory volume in one second (FEV1) ranged from 26% to 48% predicted). There was an increase in percentage change peak and endurance exercise capacity with NIV during training (mean difference in peak exercise capacity 17%, 95% confidence interval (CI) 7% to 27%, 60 participants, low-quality evidence; mean difference in endurance exercise capacity 59%, 95% CI 4% to 114%, 48 participants, low-quality evidence). However, there was no clear evidence of a difference between interventions for all other measures of exercise capacity. The results for HRQL assessed using the St George's Respiratory Questionnaire do not rule out an effect of NIV (total score mean 2.5 points, 95% CI -2.3 to 7.2, 48 participants, moderate-quality evidence). Physical activity was not assessed in any study. There was an increase in training intensity with NIV during training of 13% (95% CI 1% to 27%, 67 participants, moderate-quality evidence), and isoload lactate was lower with NIV (mean difference -0.97 mmol/L, 95% CI -1.58mmol/L to -0.36 mmol/L, 37 participants, moderate-quality evidence). The effect of NIV on dyspnoea or the number of dropouts between interventions was uncertain, although again results were imprecise. No adverse events and no information regarding cost were reported. Only one study blinded participants, whereas three studies used blinded assessors. Adequate allocation concealment was reported in four studies.

AUTHORS' CONCLUSIONS

The small number of included studies with small numbers of participants, as well as the high risk of bias within some of the included studies, limited our ability to draw strong evidence-based conclusions. Although NIV during lower limb exercise training may allow people with COPD to exercise at a higher training intensity and to achieve a greater physiological training effect compared with exercise training alone or exercise training with sham NIV, the effect on exercise capacity is unclear. Some evidence suggests that NIV during exercise training improves the percentage change in peak and endurance exercise capacity; however, these findings are not consistent across other measures of exercise capacity. There is no clear evidence that HRQL is better or worse with NIV during training. It is currently unknown whether the demonstrated benefits of NIV during exercise training are clinically worthwhile or cost-effective.

Non-invasive ventilation for cystic fibrosis

BACKGROUND

Non-invasive ventilation may be a means to temporarily reverse or slow the progression of respiratory failure in cystic fibrosis.

OBJECTIVES

To compare the effect of non-invasive ventilation versus no non-invasive ventilation in people with cystic fibrosis.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We searched the reference lists of each trial for additional publications possibly containing other trials.Most recent search: 22 February 2013.

SELECTION CRITERIA

Randomised controlled trials comparing a form of pressure preset or volume preset non-invasive ventilation to no non-invasive ventilation in people with acute or chronic respiratory failure in cystic fibrosis.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trials for inclusion criteria and methodological quality, and extracted data.

MAIN RESULTS

Fifteen trials were identified; seven trials met the inclusion criteria with a total of 106 participants. Six trials evaluated single treatment sessions and one evaluated a six-week intervention.Four trials (79 participants) evaluated non-invasive ventilation for airway clearance compared with an alternative chest physiotherapy method and showed that airway clearance may be easier with non-invasive ventilation and people with cystic fibrosis may prefer it. We were unable to find any evidence that NIV increases sputum expectoration, but it did improve some lung function parameters.Three trials (27 participants) evaluated non-invasive ventilation for overnight ventilatory support, measuring lung function, validated quality of life scores and nocturnal transcutaneous carbon dioxide. Due to the small numbers of participants and statistical issues, there were discrepancies in the results between the RevMan and the original trial analyses. No clear differences were found between non-invasive ventilation compared with oxygen or room air except for exercise performance, which significantly improved with non-invasive ventilation compared to room air over six weeks.

AUTHORS' CONCLUSIONS

Non-invasive ventilation may be a useful adjunct to other airway clearance techniques, particularly in people with cystic fibrosis who have difficulty expectorating sputum. Non-invasive ventilation, used in addition to oxygen, may improve gas exchange during sleep to a greater extent than oxygen therapy alone in moderate to severe disease. These benefits of non-invasive ventilation have largely been demonstrated in single treatment sessions with small numbers of participants. The impact of this therapy on pulmonary exacerbations and disease progression remain unclear. There is a need for long-term randomised controlled trials which are adequately powered to determine the clinical effects of non-invasive ventilation in cystic fibrosis airway clearance and exercise.

Obesity hypoventilation syndrome: mechanisms and management

Obesity hypoventilation syndrome describes the association between obesity and the development of chronic daytime alveolar hypoventilation. This syndrome arises from a complex interaction between sleep-disordered breathing, diminished respiratory drive, and obesity-related respiratory impairment, and is associated with significant morbidity and mortality. Therapy directed toward reversing these abnormalities leads to improved daytime breathing, with available treatment options including positive pressure therapy, weight loss, and pharmacological management. However, a lack of large-scale, well-designed studies evaluating these various therapies has limited the development of evidence-based treatment recommendations. Although treatment directed toward improving sleep-disordered breathing is usually effective, not all patients tolerate mask ventilation and awake hypercapnia may persist despite effective use. In the longer term, weight loss is desirable, but data on the success and sustainability of this approach in obesity hypoventilation are lacking. The review outlines the major mechanisms believed to underlie the development of hypoventilation in this subgroup of obese patients, their clinical presentation, and current therapy options.

Nocturnal hypoventilation - identifying & treating syndromes

Nocturnal hypoventilation is a common feature of disorders affecting the function of the diaphragm or central respiratory drive mechanisms. The ensuing change in gas exchange is initially confined to rapid eye movement (REM) sleep, but over time buffering of the raised carbon dioxide produces a secondary depression of respiratory drive that will further reduce ventilation not only during sleep but eventually during wakefulness as well. Failure to identify and treat nocturnal hypoventilation results in impairments in daytime function, quality of life and premature mortality. While some simple daytime tests of respiratory function can identify at risk individuals, these cannot predict the nature or severity of any sleep disordered breathing present. Nocturnal monitoring of gas exchange with or without full polysomnography is the only way to comprehensively assess this disorder, especially in the early stages of its evolution. Non invasive ventilation used during sleep is the most appropriate approach to reverse the consequences of nocturnal hypoventilation, although continuous positive airway pressure (CPAP) may be effective in those individuals where a significant degree of upper airway obstruction is present. When appropriately selected patients use therapy on a regular basis, significant improvements in quality of life, exercise capacity and survival can be achieved, irrespective of the underlying disease process.

Big breathing: the complex interaction of obesity, hypoventilation, weight loss, and respiratory function

Obesity places a significant load on the respiratory system, affecting lung volumes, respiratory muscle function, work of breathing, and ventilatory control. Despite this, most morbidly obese individuals maintain eucapnia. However, a subgroup of morbidly obese individuals will develop chronic daytime hypercapnia, described as the obesity hypoventilation syndrome (OHS). While obesity is obviously a crucial component of this syndrome, the relationship between excess fat accumulation and the development of awake hypercapnia is complex and extends beyond simply impairments of pulmonary mechanics and lung volumes as a consequence of obesity. Various compensatory mechanisms operate to maintain eucapnia even in the presence of extreme obesity. However, if compensation is impaired, hypoventilation will ensue. While obesity alone does not account for the development of hypoventilation, weight loss will produce significant improvements in lung function and awake gas exchange. Such improvements have the potential to substantially reduce morbidity and mortality in these individuals. Nevertheless, many individuals remain overweight despite substantial weight loss, with persistence of upper airway obstruction. Attention to this residual abnormality is important given the high incidence of cardiovascular abnormalities, including pulmonary hypertension, in individuals with OHS.

Bilevel ventilation during exercise in acute on chronic respiratory failure: a preliminary study

To determine the immediate effects of bilevel non-invasive ventilation plus oxygen (NIV+O(2)) during exercise compared to exercise with O(2) alone in people recovering from acute on chronic hypercapnic respiratory failure (HRF), a randomised crossover study with repeated measures was performed. Eighteen participants performed six minute walk tests (6MWT) and 16 participants performed unsupported arm exercise (UAE) tests with NIV+O(2) and with O(2) alone in random order. Distance walked increased by a mean of 43.4m (95% CI 14.1 to 72.8, p=0.006) with NIV+O(2) compared to exercise with O(2) alone. In addition, isotime oxygen saturation increased by a mean of 5% (95% CI 2-7, p=0.001) and isotime dyspnoea was reduced [median 2 (interquartile range (IQR) 1-4) versus 4 (3-5), p=0.028] with NIV+O(2). A statistically significant increase was also observed in UAE endurance time with NIV+O(2) [median 201s (IQR 93-414) versus 157 (90-342), p=0.033], and isotime perceived exertion (arm muscle fatigue) was reduced by a mean of 1.0 on the Borg scale (95% CI -1.9 to -0.1, p=0.037) compared with O(2) alone. Non-invasive ventilation plus O(2) during walking resulted in an immediate improvement in distance walked and oxygen saturation, and a reduction in dyspnoea compared to exercise with O(2) alone in people recovering from acute on chronic HRF. The reduction of dyspnoea during walking and arm muscle fatigue during UAE observed with NIV+O(2) may allow patients to better tolerate exercise early in the recovery period.

Non-invasive ventilation for cystic fibrosis

BACKGROUND

Non-invasive ventilation (NIV) may be a means to temporarily reverse or slow the progression of respiratory failure in cystic fibrosis (CF).

OBJECTIVES

To compare the effect of NIV versus no NIV in people with CF.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We searched the reference lists of each trial for additional publications possibly containing other trials.Most recent search: June 2008.

SELECTION CRITERIA

Randomised controlled trials comparing a form of pressure preset or volume preset NIV to no NIV in people with acute or chronic respiratory failure in CF.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trials for inclusion criteria and methodological quality, and extracted data.

MAIN RESULTS

Fifteen trials were identified; seven trials met the inclusion criteria with a total of 106 participants. Six trials evaluated single treatment sessions and one evaluated a six-week intervention.Four trials (79 participants) evaluated NIV for airway clearance compared with an alternative chest physiotherapy method and showed that airway clearance may be easier with NIV and people with CF may prefer it. We were unable to find any evidence that NIV increases sputum expectoration, but it did improve some lung function parameters.Three trials (27 participants) evaluated NIV for overnight ventilatory support, measuring lung function, validated quality of life scores and nocturnal transcutaneous carbon dioxide. Due to the small numbers of participants and statistical issues, there were discrepancies in the results between the RevMan and the original trial analyses. No clear differences were found between NIV compared with oxygen or room air except for exercise performance, which significantly improved with NIV compared to room air over six weeks.

AUTHORS' CONCLUSIONS

Non-invasive ventilation may be a useful adjunct to other airway clearance techniques, particularly in people with CF who have difficulty expectorating sputum. Non-invasive ventilation, used in addition to oxygen, may improve gas exchange during sleep to a greater extent than oxygen therapy alone in moderate to severe disease. These benefits of NIV have largely been demonstrated in single treatment sessions with small numbers of participants. The impact of this therapy on pulmonary exacerbations and disease progression remain unclear. There is a need for long-term randomised controlled trials which are adequately powered to determine the clinical effects of non-invasive ventilation in CF airway clearance and exercise.

Obesity and the lung: 2. Obesity and sleep-disordered breathing

As the prevalence of obesity increases in both the developed and the developing world, the respiratory consequences are often underappreciated. This review discusses the presentation, pathogenesis, diagnosis and management of the obstructive sleep apnoea, overlap and obesity hypoventilation syndromes. Patients with these conditions will commonly present to respiratory physicians, and recognition and effective treatment have important benefits in terms of patient quality of life and reduction in healthcare utilisation. Measures to curb the obesity epidemic are urgently required.

Randomised trial of CPAP vs bilevel support in the treatment of obesity hypoventilation syndrome without severe nocturnal desaturation

BACKGROUND

Untreated, obesity hypoventilation is associated with significant use of health care resources and high mortality. It remains unclear whether continuous positive airway pressure (CPAP) or bilevel ventilatory support (BVS) should be used as initial management. The aim of this study was to determine if one form of positive pressure is superior to the other in improving daytime respiratory failure.

METHODS

A prospective randomised study was performed in patients with obesity hypoventilation referred with respiratory failure. After exclusion of patients with persisting severe nocturnal hypoxaemia (Spo(2) < 80% for > 10 min) or carbon dioxide retention (> 10 mm Hg) despite optimal CPAP, the remaining patients were randomly assigned to receive either CPAP or BVS over a 3-month period. The primary outcome was change in daytime carbon dioxide level. Secondary outcome measures included daytime sleepiness, quality of life, compliance with treatment and psychomotor vigilance testing.

RESULTS

Thirty-six patients were randomised to either home CPAP (n = 18) or BVS (n = 18). The two groups did not differ significantly at baseline with regard to physiological or clinical characteristics. Following 3 months of treatment, daytime carbon dioxide levels decreased in both groups (CPAP 6 (8) mm Hg; BVS 7 (7) mm Hg) with no between-group differences. There was no difference in compliance between the two treatment groups (5.8 (2.4) h/night CPAP vs 6.1 (2.1) h/night BVS). Although both groups reported an improvement in daytime sleepiness, subjective sleep quality and psychomotor vigilance performance were better with BVS.

CONCLUSIONS

Both CPAP and BVS appear to be equally effective in improving daytime hypercapnia in a subgroup of patients with obesity hypoventilation syndrome without severe nocturnal hypoxaemia.

TRIAL REGISTRATION NUMBER

Australian Clinical Trials Registry ACTRN01205000096651.

Current perspectives on the obesity hypoventilation syndrome

PURPOSE OF REVIEW

Identifying and treating obesity hypoventilation syndrome is an important therapeutic goal, especially given the high morbidity and mortality associated with untreated disease. Significant weight loss or effective treatment of upper airway obstruction will reverse daytime hypoventilation, suggesting that these two mechanisms play key roles in the development and progression of this disorder. Only a subset of morbidly obese patients will develop awake hypercapnia, however, even in the presence of sleep disordered breathing. This implies that complex interplay between a number of known and unknown mechanisms is needed to produce daytime respiratory failure in this patient population.

RECENT FINDINGS

Work in the mouse model of obesity has been central in advancing our understanding of the role leptin plays in stimulating ventilation. Leptin deficiency or development of leptin resistance in obesity leads to alterations in central respiratory drive and reduced ventilatory responsiveness, permitting development of carbon dioxide retention. Changes in neuromodulators resulting from the effects of hypoxia may further exacerbate the problem by depressing arousal from sleep in the face of abnormal breathing.

SUMMARY

Understanding the various mechanisms contributing to development of obesity hypoventilation is important in order to identify new approaches to effective long-term management of this disorder.

Electroencephalographic arousals during sleep do not alter the pressor response to Cheyne-Stokes respiration in subjects with chronic heart failure

This study examined the influence of electroencephalographic (EEG) arousal on the magnitude and morphology of the pressor response to Cheyne-Stokes respiration (CSR) in subjects with congestive heart failure (CHF). Thirteen subjects with stable CHF (left ventricular ejection fraction, 26 +/- 7%) and CSR (apnea-hypopnea index 52 +/- 15 h(-1)) underwent overnight polysomnography with beat-to-beat measurement of systemic arterial blood pressure (BP). CSR events were divided into those with or without an EEG arousal defined according to the criteria of the American Sleep Disorders Association. The pressor response was quantified in terms of the delta BP change (difference between the minimum BP during apnea and maximum BP during hyperpnea). Changes in the morphology of the pressor response were assessed by subdividing individual respiratory events into six periods (three during apnea: A1, A2, A3; and three during hyperpnea: H1, H2, H3). Considerable fluctuations in BP and heart rate (HR) were observed across the CSR cycle (delta mean BP 20.2 +/- 6.5 mmHg). The presence of an EEG arousal did not alter the amplitude of fluctuations in BP. Mean blood pressure (MBP) increased 21.0 +/- 7.5 mmHg with arousal versus 19.3 +/- 5.8 mmHg without arousal (NS). A repeated measures ANOVA showed no significant interaction between the presence of arousal and the proportional change in mean BP across the six periods, indicating that an EEG arousal had no effect on the morphology of MBP change during CSR [F(5,60) = 1.44, P = 0.22]. This study showed that EEG-defined arousal does not amplify the pressor response to CSR in CHF.

Non-invasive ventilation for cystic fibrosis

BACKGROUND

Non-invasive ventilation (NIV) may be a means to temporarily reverse or slow the progression of respiratory failure in cystic fibrosis (CF).

OBJECTIVES

To compare the effect of NIV versus no NIV in people with CF.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching relevant journals and abstract books of conference proceedings. We searched the reference lists of each trial for additional publications possibly containing other trials. Most recent search: October 2006.

SELECTION CRITERIA

Randomised controlled trials comparing a form of pressure preset or volume preset NIV to no NIV in people with acute or chronic respiratory failure in CF.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed trials for inclusion criteria and methodological quality, and extracted data.

MAIN RESULTS

Fifteen trials were identified; seven trials met the inclusion criteria with a total of 106 participants. Six trials evaluated single treatment sessions only and one evaluated a six-week intervention. Four trials (79 participants) evaluated NIV for airway clearance compared with an alternative chest physiotherapy method and showed that airway clearance may be easier with NIV and people with CF may prefer it. We were unable to find any evidence that NIV increases sputum expectoration, but it did improve some lung function parameters.Three trials (27 participants) evaluated NIV for overnight ventilatory support. Lung function and nocturnal transcutaneous carbon dioxide were evaluated within two trials. Due to the small numbers of participants and statistical issues, there were discrepancies in the results between the RevMan and the original trial analyses. No clear differences were found between NIV compared with oxygen or room air except for exercise performance, which significantly improved with NIV compared to room air over six weeks.

AUTHORS' CONCLUSIONS

Non-invasive ventilation may be a useful adjunct to other airway clearance techniques, particularly in people with CF who have difficulty expectorating sputum. Non-invasive ventilation, when used in addition to oxygen, may improve gas exchange during sleep to a greater extent than oxygen therapy alone in moderate to severe disease. These benefits of NIV have largely been demonstrated in single treatment sessions with small numbers of participants. The impact of this therapy on pulmonary exacerbations and disease progression remain unclear. There is a need for long-term randomised controlled trials which are adequately powered to determine the clinical effects of non-invasive ventilation in CF airway clearance and exercise.

Obesity hypoventilation syndrome: hypoxemia during continuous positive airway pressure

BACKGROUND

Polysomnography findings between matched groups with obstructive sleep apnea (OSA) and OSA plus obesity-hypoventilation syndrome (OHS) before and after continuous positive airway pressure (CPAP), particularly in the extremely severe obese (body mass index [BMI] >or= 50 kg/m2), are unclear.

DESIGN

Prospective study of subjects (BMI >or= 50 kg/m2) undergoing diagnostic polysomnography. Subjects with an apnea-hypopnea index (AHI) >or= 15/h underwent a second polysomnography with CPAP. The effect of 1 night of CPAP on sleep architecture, AHI, arousal indexes, and nocturnal oxygenation was assessed. OHS was defined as those subjects with obesity, PaCo2 > 45 mm Hg, and PaO2 < 70 mm Hg in the absence of lung disease.

RESULTS

Twenty-three subjects with moderate-to-severe OSA and 23 subjects with moderate-to-severe OSA plus OHS underwent a 1-night trial of CPAP. Both groups were matched for spirometry, BMI, and AHI, but oxygen desaturation was worse in the OSA-plus-OHS group. CPAP significantly improved rapid eye movement (REM) duration (p < 0.005), AHI (p < 0.005), arousal indexes (p < 0.005), and percentage of total sleep time (TST) with oxygen saturation (SpO2) < 90% (p < 0.005) in both groups. In subjects with OSA plus OHS, 43% continued to spend > 20% of TST with SpO2 < 90%, compared to 9% of the OSA group, despite the adequate relief of upper airway obstruction.

CONCLUSIONS

Extremely severe obese subjects (BMI >or= 50 kg/m2) with moderate-to-severe OSA plus OHS exhibit severe oxygen desaturation but similar severities of AHI, arousal indexes, and sleep architecture abnormalities when compared to matched subjects without OHS. CPAP significantly improves AHI, REM duration, arousal indexes, and nocturnal oxygen desaturation. Some subjects with OHS continued to have nocturnal desaturation despite the control of upper airway obstruction; other mechanisms may contribute. Further long-term studies assessing the comparative role of CPAP and bilevel ventilatory support in such subjects with OHS is warranted.

Treatment of obesity hypoventilation syndrome and serum leptin

BACKGROUND

Leptin is a protein produced by adipose tissue that circulates to the brain and interacts with receptors in the hypothalamus to inhibit eating. In obese humans, serum leptin is up to four times higher than in lean subjects, indicating that human obesity is associated with a central resistance to the weight-lowering effects of leptin. Although the leptin-deficient mouse (ob/ob) develops obesity hypoventilation syndrome (OHS), in humans with OHS, serum leptin is a better predictor of awake hypercapnia in obesity than the body mass index (BMI). This suggests that central leptin resistance may promote the development of OHS in humans. We speculated that the reversal of OHS by regular non-invasive ventilation (NIV) therapy decreases leptin levels.

OBJECTIVES

The aim of this study was to investigate whether ventilatory treatment of OHS would alter circulating leptin concentrations.

METHOD

We measured fasting serum leptin levels, BMI, spirometry and arterial blood gases in 14 obese hypercapnic subjects undergoing a diagnostic sleep study.

RESULTS

The average age of the subjects was (mean +/- SE) 62 +/- 13 years, BMI 40.9 +/- 2.2 kg/m(2), PaCO(2) 6.7 +/- 0.2 kPa, PaO(2 )8.9 +/- 0.4 kPa and total respiratory disturbance index 44 +/- 35 events/hour. Subjects were clinically reviewed after a median of 2.3 years (range 1.6-3) with repeat investigations. Nine patients were regular NIV users and 5 were non-users. NIV users had a significant reduction in serum leptin levels (p = 0.001), without a change in BMI. In these patients, there was a trend towards an improved daytime hypercapnia and hypoxemia, while in the 5 non-users, no changes in serum leptin, BMI or arterial blood gases occurred.

CONCLUSION

Regular NIV use reduces serum leptin in OHS. Leptin may be a modulator of respiratory drive in patients with OHS.