Obesity Hypoventilation Syndrome

The value of neck adipose tissue as a predictor for metabolic risk in health and type 2 diabetes

Upper-body adiposity is adversely associated with metabolic health whereas the opposite is observed for the lower-body. The neck is a unique upper-body fat depot in adult humans, housing thermogenic brown adipose tissue (BAT), which is increasingly recognised to influence whole-body metabolic health. Loss of BAT, concurrent with replacement by white adipose tissue (WAT), may contribute to metabolic disease, and specific accumulation of neck fat is seen in certain conditions accompanied by adverse metabolic consequences. Yet, few studies have investigated the relationships between neck fat mass (NFM) and cardiometabolic risk, and the influence of sex and metabolic status. Typically, neck circumference (NC) is used as a proxy for neck fat, without considering other determinants of NC, including variability in neck lean mass. In this study we develop and validate novel methods to quantify NFM using dual x-ray absorptiometry (DEXA) imaging, and subsequently investigate the associations of NFM with metabolic biomarkers across approximately 7000 subjects from the Oxford BioBank. NFM correlated with systemic insulin resistance (Homeostatic Model Assessment for Insulin Resistance; HOMA-IR), low-grade inflammation (plasma high-sensitivity C-Reactive Protein; hsCRP), and metabolic markers of adipose tissue function (plasma triglycerides and non-esterified fatty acids; NEFA). NFM was higher in men than women, higher in type 2 diabetes mellitus compared with non-diabetes, after adjustment for total body fat, and also associated with overall cardiovascular disease risk (calculated QRISK3 score). This study describes the development of methods for accurate determination of NFM at scale and suggests a specific relationship between NFM and adverse metabolic health.

Revisiting the Role of Serotonin in Sleep-Disordered Breathing

Serotonin or 5-hydroxytryptamine (5-HT) is a ubiquitous neuro-modulator-transmitter that acts in the central nervous system, playing a major role in the control of breathing and other physiological functions. The midbrain, pons, and medulla regions contain several serotonergic nuclei with distinct physiological roles, including regulating the hypercapnic ventilatory response, upper airway patency, and sleep-wake states. Obesity is a major risk factor in the development of sleep-disordered breathing (SDB), such as obstructive sleep apnea (OSA), recurrent closure of the upper airway during sleep, and obesity hypoventilation syndrome (OHS), a condition characterized by daytime hypercapnia and hypoventilation during sleep. Approximately 936 million adults have OSA, and 32 million have OHS worldwide. 5-HT acts on 5-HT receptor subtypes that modulate neural control of breathing and upper airway patency. This article reviews the role of 5-HT in SDB and the current advances in 5-HT-targeted treatments for SDB.

Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates

Chronic kidney disease (CKD) is caused by hypoxia in the renal tissue, leading to inflammation and increased migration of pathogenic cells. Studies showed that leukocytes directly sense hypoxia and respond by initiating gene transcription, encoding the 2-integrin adhesion molecules. Moreover, other mechanisms participate in hypoxia, including anemia. CKD-associated anemia is common, which induces and worsens hypoxia, contributing to CKD progression. Anemia correction can slow CKD progression, but it should be cautiously approached. In this comprehensive review, the underlying pathophysiology mechanisms and the impact of renal tissue hypoxia and anemia in CKD onset and progression will be reviewed and discussed in detail. Searching for the latest updates in PubMed Central, Medline, PubMed database, Google Scholar, and Google search engines were conducted for original studies, including cross-sectional studies, cohort studies, clinical trials, and review articles using different keywords, phrases, and texts such as "CKD progression, anemia in CKD, CKD, anemia effect on CKD progression, anemia effect on CKD progression, and hypoxia and CKD progression". Kidney tissue hypoxia and anemia have an impact on CKD onset and progression. Hypoxia causes nephron cell death, enhancing fibrosis by increasing interstitium protein deposition, inflammatory cell activation, and apoptosis. Severe anemia correction improves life quality and may delay CKD progression. Detection and avoidance of the risk factors of hypoxia prevent recurrent acute kidney injury (AKI) and reduce the CKD rate. A better understanding of kidney hypoxia would prevent AKI and CKD and lead to new therapeutic strategies.

Predictors of Nocturnal Hypoxemic Burden in Patients Undergoing Elective Coronary Artery Bypass Grafting Surgery

Background: Nocturnal hypoxemia has been linked to increased cardiovascular morbidity and mortality. Several common diseases, such as sleep-disordered breathing (SDB), heart failure (HF), obesity, and pulmonary disease, coincide with an elevated nocturnal hypoxemic burden with and without repetitive desaturations. Research question: This study aimed to evaluate the association of relevant common diseases with distinctive metrics of nocturnal hypoxemic burden with and without repetitive desaturations in patients undergoing coronary artery bypass grafting surgery. Study design and methods: In this subanalysis of the prospective observational study, CONSIDER-AF (NCT02877745) portable SDB monitoring was performed on 429 patients with severe coronary artery disease the night before cardiac surgery. Pulse oximetry was used to determine nocturnal hypoxemic burden, as defined by total recording time spent with oxygen saturation levels < 90% (T90). T90 was further characterized as T90 due to intermittent hypoxemia (T90desaturation) and T90 due to nonspecific and noncyclic SpO2-drifts (T90non-specific). Results: Multivariable linear regression analysis identified SDB (apnea-hypopnea-index ≥ 15/h; B [95% CI]: 6.5 [0.4; 12.5], p = 0.036), obesity (8.2 [2.5; 13.9], p = 0.005), and mild-to-moderate chronic obstructive pulmonary disease (COPD, 16.7 [8.5; 25.0], p < 0.001) as significant predictors of an increased nocturnal hypoxemic burden. Diseases such as SDB, obesity and HF were significantly associated with elevated T90desaturation. In contrast, obesity and mild-to-moderate COPD were significant modulators of T90non-specific. Interpretation: SDB and leading causes for SDB, such as obesity and HF, are associated with an increased nocturnal hypoxemic burden with repetitive desaturations. Potential causes for hypoventilation syndromes, such as obesity and mild-to-moderate COPD, are linked to an increased hypoxemic burden without repetitive desaturations. Clinical Trial Registration: ClinicalTrials.gov identifier: NCT02877745.

Sleep Apnea Combined with Pulmonary Hypertension in a Veteran Patient Population

We have investigated the concurrence of sleep apnea and pulmonary hypertension in a Veteran population. We retrospectively reviewed 142 patients who underwent chest CT scans and had a dilated main pulmonary artery, defined as a width exceeding 29 mm on axial images. Approximately 40% of patients with pulmonary hypertension had associated sleep apnea. No significant difference in pulmonary artery diameters could be found between the group without sleep apnea and the group with sleep apnea (34.5 ± 4.2 mm vs. 34.7 ± 4.4 mm, p = 0.373).

Emerging Role of GLP-1 Agonists in Obesity: A Comprehensive Review of Randomised Controlled Trials

Obesity is a chronic disease with high prevalence and associated comorbidities, making it a growing global concern. These comorbidities include type 2 diabetes, hypertension, ventilatory dysfunction, arthrosis, venous and lymphatic circulation diseases, depression, and others, which have a negative impact on health and increase morbidity and mortality. GLP-1 agonists, used to treat type 2 diabetes, have been shown to be effective in promoting weight loss in preclinical and clinical studies. This review summarizes numerous studies conducted on the main drugs in the GLP-1 agonists class, outlining the maximum achievable weight loss. Our aim is to emphasize the active role and main outcomes of GLP-1 agonists in promoting weight loss, as well as in improving hyperglycemia, insulin sensitivity, blood pressure, cardio-metabolic, and renal protection. We highlight the pleiotropic effects of these medications, along with their indications, contraindications, and precautions for both diabetic and non-diabetic patients, based on long-term follow-up studies.

Impact of hypoxia on male reproductive functions

Male reproductive functions, which include testicular steroidogenesis, spermatogenesis, and sexual/erectile functions are key in male fertility, but may be adversely altered by several factors, including hypoxia. This review demonstrates the impact of hypoxia on male reproductive functions. Acute exposure to hypoxia promotes testosterone production via stimulation of autophagy and upregulation of steroidogenic enzymes and voltage-gated L-type calcium channel, nonetheless, chronic exposure to hypoxia impairs steroidogenesis via suppression of the hypothalamic-pituitary-testicular axis. Also, hypoxia distorts spermatogenesis and reduces sperm count, motility, and normal forms via upregulation of VEGF and oxidative stress-sensitive signaling. Furthermore, hypoxia induces sexual and erectile dysfunction via a testosterone-dependent downregulation of NO/cGMP signaling and upregulation of PGE1/TGFβ1-driven penile endothelial dysfunction. Notably, hypoxia programs male sexual function and spermatogenesis/sperm quality via feminization and demasculinization of males and oxidative stress-mediated alteration in sperm DNA methylation. Since oxidative stress plays a central role in hypoxia-induced male reproductive dysfunction, studies exploring the effects of antioxidants and upregulation of transcription of antioxidants on hypoxia-induced male reproductive dysfunction are recommended.

Interactive Effect of Combined Intermittent and Sustained Hypoxia and High-Fat Diet on the Colonic Mucosal Microbiome and Host Gene Expression in Mice

Purpose

Gut dysbiosis can cause cardiometabolic disease. Gut dysbiosis can be independently caused by high-fat diet (HFD) and intermittent hypoxia (IH; characterizing obstructive sleep apnea), but the interactive effect of combined intermittent and sustained hypoxia (IH+SH) (characterizing obesity hypoventilation syndrome) and HFD on gut dysbiosis is unclear. We aimed to investigate the interactive effect of a combination of IH and SH and HFD on proximal colonic microbiota and colonic gene expression pattern.

Methods

Male mice (n=16) were randomly received four different combinations of diet (normal versus HFD) and oxygen conditions (normoxia versus IH+SH) for 4 weeks. Bacterial DNA and mucosal epithelial cell RNA from proximal colon were collected for analysis of adherent microbiome and host's gene expression analysis.

Results

HFD during IH+SH (22.6 ± 5.73; SD) led to greater Firmicutes: Bacteroidetes ratio than HFD during normoxia (5.89 ± 1.19; p=0.029). HFD significantly decreased microbial diversity as compared to normal diet, but the addition of IH+SH to HFD mildly reversed such effects. When compared to HFD during normoxia, HFD with combination of IH+SH resulted in changes to host mucosal gene expression for apical junctional complexes and adhesion molecules. Specifically, when compared to HFD during normoxia, HFD during IH+SH led to upregulation of Claudin 2 and Syk (tight junction dysfunction and increased mucosal permeability), while the barrier promoting claudin 4 was downregulated.

Conclusion

HFD during combined IH and SH causes greater gut dysbiosis and potentially adverse changes in colonic epithelial transcriptome than HFD during normoxia. The latter changes are suggestive of impaired gut barrier function.

Defining obesity hypoventilation syndrome

With increasing prevalence of obesity, the substantial contribution of obesity hypoventilation syndrome (OHS) to morbidity and mortality is likely to increase. It is therefore crucial that the condition has a clear definition to allow timely identification of patients. OHS was first described as “Pickwickian syndrome” in the 1950s; in subsequent decades, case reports did not clearly delineate between patients suffering from OHS and those suffering from obstructive sleep apnoea. In 1999, the American Academy of Sleep Medicine published a guideline that delineated the cause of daytime hypercapnia as either predominantly upper airway or predominantly hypoventilation. This was the first formal definition of OHS as the presence of daytime alveolar hypoventilation (arterial carbon dioxide tension >45 mmHg) in patients with body mass index >30 kg·m⁻² in the absence of other causes of hypoventilation. This definition is reflected in the most recent guidelines published on OHS. Recent developments in defining OHS include proposed classification systems of severity and demonstrating the value of using serum bicarbonate to exclude OHS in patients with a low index of suspicion.

Obesity hypoventilation syndrome is defined as daytime alveolar hypoventilation in obese patients in the absence of other causes of hypoventilation. Classifications of severity are now needed to target treatment at the most appropriate individuals.https://bit.ly/3yLuiL9

Experimental Setting for Applying Mechanical Stimuli to Study the Endothelial Response of Ex Vivo Vessels under Realistic Pathophysiological Environments

This paper describes the design, construction and testing of an experimental setting, making it possible to study the endothelium under different pathophysiological conditions. This novel experimental approach allows the application of the following stimuli to an ex vivo vessel in a physiological bath: (a) a realistic intravascular pressure waveform defined by the user; (b) shear stress in the endothelial layer since, in addition to the pressure waveform, the flow through the vessel can be independently controlled by the user; (c) conditions of hypo/hyperoxia and hypo/hypercapnia in an intravascular circulating medium. These stimuli can be applied alone or in different combinations to study possible synergistic or antagonistic effects. The setting performance is illustrated by a proof of concept in an ex vivo rabbit aorta. The experimental setting is easy to build by using very low-cost materials widely available. Online Supplement files provide all the technical information (e.g., circuits, codes, 3D printer drivers) following an open-source hardware approach for free replication.

Impact of obesity and SARS-CoV-2 infection: implications for host defence - a living review

The role of obesity in the pathophysiology of respiratory virus infections has become particularly apparent during the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, where obese patients are twice as likely to suffer from severe coronavirus disease 2019 (COVID-19) than healthy weight individuals. Obesity results in disruption of systemic lipid metabolism promoting a state of chronic low-grade inflammation. However, it remains unclear how these underlying metabolic and cellular processes promote severe SARS-CoV-2 infection. Emerging data in SARS-CoV-2 and Influenza A virus (IAV) infections show that viruses can further subvert the host's altered lipid metabolism and exploit obesity-induced alterations in immune cell metabolism and function to promote chronic inflammation and viral propagation. In this review, we outline the systemic metabolic and immune alterations underlying obesity and discuss how these baseline alterations impact the immune response and disease pathophysiology. A better understanding of the immunometabolic landscape of obese patients may aid better therapies and future vaccine design.

Disordered Leptin signaling in the retrotrapezoid nucleus is associated with the impaired hypercapnic ventilatory response in obesity

Sleep-disordered breathing is characterized by disruptions of normal breathing patterns during sleep. Obesity is closely related to hypoventilation or apnea and becomes a primary risk factor for sleep-disordered breathing. Leptin, a peptide secreted by adipose tissue, has been implicated in central control of breathing. Activation of the retrotrapezoid nucleus (RTN) neurons, a critical central respiratory chemoreceptor candidate, potentiates a central drive to breathing. Here, we ask whether the disordered leptin signaling in the RTN is responsible for obesity-related hypoventilation. In a diet induced obesity (DIO) mouse model, the hypercapnic ventilatory response (HCVR) was assessed and the cellular leptin signaling in the RTN was examined. Our main findings demonstrate that DIO mice exhibit overweight, hypercapnia, high levels of serum and cerebrospinal leptin. During exposure to room air, DIO mice manifest basal hypoventilation with a rapid and shallow breathing pattern. Exposure to CO₂ elicits the impaired HCVR in DIO mice. In addition, both the number of CO₂-activated neurons and expression of TASK-2 channels in the RTN are dramatically reduced in DIO mice. Moreover, there is leptin signaling disorder in RTN neurons in DIO mice, including a significant decrease in leptin-activated RTN neurons, downregulation of phosphorylated STAT3 and upregulation of SOCS3. Altogether, we suggest that the disordered leptin/STAT3/SOCS3 signaling pathway in the RTN plays a role in obesity-related hypoventilation.

Adult obesity complications: challenges and clinical impact

The complications associated with adult obesity are overwhelming national healthcare systems. No country has yet implemented a successful population-level strategy to reverse the rising trends of obesity. This article presents epidemiological data on the complications of adult obesity and discusses some of the challenges associated with managing this disease at a population and individual level.

Atelectasis in Bariatric Surgery: Review Analysis and Key Practical Recommendations

Obesity is a condition that affects multiple organ systems, particularly the cardiovascular and respiratory system. In recent years, bariatric surgery has been reported to be the gold standard in the treatment of morbid obesity. Body mass index alone is insufficient to predict risks related to anaesthesia and surgery. Obesity contributes to significant postoperative atelectasis and is considered an independent risk factor for postoperative atelectasis owing to decreased functional residual capacity. The treatment and reversibility of atelectasis developed in obese patients undergoing bariatric surgery are challenging. Therefore, an optimisation of pulmonary functions before surgery, lung-sparing ventilation during the perioperative period, awareness of potential postoperative complications and knowledge about preventive measures and therapeutic approaches have become increasingly important in bariatric surgery. The aim of this review was to aid clinicians in the management of atelectasis in patients undergoing bariatric surgery during the perioperative and postoperative period.

Association of End-Tidal Carbon Dioxide Monitoring With Nurses' Confidence in Patient Readiness for Postanesthesia Discharge

PURPOSE

To determine if end-tidal carbon dioxide (etCO₂) value increased nurses' perceptions of confidence in patients' readiness for postanesthesia care unit (PACU) discharge.

DESIGN

Prospective, cross-sectional, comparative, one-group (pre-post) design.

METHODS

Nurses completed 2 assessments of confidence in readiness for discharge, before and after etCO₂ monitoring. Patient (discharge pain level, body mass index, sleep apnea history, and opioid use) and nurse factors were assessed. Analyses included descriptive and comparative statistics.

FINDINGS

Of 133 patients, mean (standard deviation) etCO₂ was 36.1 (5.7) mm Hg. Nurses' confidence in readiness for discharge differed before and after etCO₂ assessment. Confidence score decreased when etCO₂ was low (P = .003) or high (P = .005), compared with normal values. In linear regression, etCO₂ remained a factor in nurses' confidence in readiness for discharge (P < .001).

CONCLUSIONS

In a PACU, etCO₂ monitoring changed nurses' perceptions of confidence in patients' readiness for discharge.

A randomized control trial using intraoperative dexmedetomidine during Roux-en-Y gastric bypass surgery to reduce postoperative pain and narcotic use

BACKGROUND

Dexmedetomidine (DMET), a selective a2-adrenergic agonist, is an opioid-sparing adjuvant sedative that avoids respiratory depression and has been shown to be beneficial in bariatric surgery patients. Although benefit has been shown, prior studies have not evaluated the pain control effects of a single intraoperative bolus.

OBJECTIVES

To evaluate the postoperative effects of a single intraoperative dose of DMET.

SETTINGS

University Hospital, United States.

METHODS

This is a prospective, randomized, double-blinded study registered with clinicaltrials.gov (#NCT02604940). Patients undergoing laparoscopic Roux-en-Y gastric bypass surgery were randomized and given either a placebo or an intraoperative DMET bolus, where 1 mg/kg was delivered over 10 minutes at the time of surgical closure. Measured outcomes included the following: postoperative pain scores, patient-controlled analgesia (PCA) opioid consumption, PCA demand bolus attempts, duration of postanesthesia care unit (PACU) stay, and vital signs. Descriptive statistics were recorded as frequencies and compared using Χ² analysis, and a Welch's 2-sample t test was used to compare continuous variables.

RESULTS

Forty-six participants undergoing laparoscopic Roux-en-Y gastric bypass surgery were randomized into placebo (n = 20) or DMET (n = 26) groups. There were no statistical differences in age (45.1 versus 43.2 yr, P = .522), sex (80% versus 81% female, P = .948), and body mass index (46.1 versus 45.6 kg/m², P = .818) between the 2 groups. There were no statistically significant differences in vital signs (heart rate, blood pressure, oxygen saturation, and respiration rate) between DMET and placebo groups in the preoperative and intraoperative period. During the initial 4 hours in the PACU postoperatively, mean heart rate (70 ± 12 versus 86 ± 14, P < .001), systolic blood pressure (107 ± 17 versus 148 ± 16, P < .001), and diastolic blood pressure (56 ± 15 versus 79 ± 13, P < .001) were significantly lower in the DMET-treated group compared with placebo. During the initial 4 hours in the PACU, mean self-reported pain scores were significantly lower in the DMET-treated group (3.6 ± 2.8) compared with the placebo group (6.7 ± 3; P = .005). The lower pain scores occurred with no significant difference in the mean opioid dosage received in the PACU between DMET-treated (2.66 ± 2.02 mg) and placebo (3.7 ± 2.3 mg; P = .09) groups. Also, there was no statistically significant difference in the total number of PCA attempts for opioids between the DMET-treated and placebo groups (P = .49).

CONCLUSIONS

A single bolus of DMET (1 mg/kg delivered over 10 min) administered at the time of surgical closure did not reduce immediate PACU usage of opioids but significantly reduced reported pain scores and caused a significant decrease in the number of attempts made by patients; this is a trend of decreased attempts over time (P = .04) in the DMET group. The trend of the mean total medication used over time indicates that there is neither an increasing nor decreasing trend for the DMET group, but there is an increasing trend in the total used over time for the placebo group. There was no statistically or clinically significant bradycardia, hypotension, hypoxia, respiratory depression intraoperative duration, or PACU stay. Reduced single bolus dosing of DMET required for analgesia in bariatric surgery patients is optimal from physiologic, level of care, and cost perspectives.

Comparison between auto-trilevel and bilevel positive airway pressure ventilation for treatment of patients with concurrent obesity hypoventilation syndrome and obstructive sleep apnea syndrome

PURPOSE

Our study aims to compare the difference in clinical efficacy between auto-trilevel positive airway pressure (auto-trilevel PAP) ventilator and conventional fixed bilevel positive airway pressure (BiPAP) ventilator for obesity hypoventilation syndrome (OHS) patients with coexisting moderate or severe obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

Twenty-three OHS patients with moderate or severe OSAHS enrolled between January 2015 and September 2017 underwent ventilation by three different modes of positive airway pressure (PAP) for 8 h per night. A single variable mode was applied at the first night followed by two nights when no PAP therapy was carried out as a washout period between each mode. The inspiratory positive airway pressure (IPAP) decided by PaCO₂ was consistently used for modes 1, 2, and 3. In mode 1, the expiratory positive airway pressure (EPAP) issued by BiPAP was decided by the minimal PAP levels for cessation of snoring. However, in mode 2, the EPAP was fixed at 3 cmH₂O higher than this value. With the use of auto-trilevel PAP in mode 3, the EPAP was set to initially match that of mode 1 but the end of EPAP (EEPAP) was automatically regulated to be elevated according to upper airway patency condition. We also compared the following parameters including apnea hypopnea index (AHI), minimal SpO₂ (miniSpO₂), arousal index, and sleep efficiency during sleep; PaCO₂ in the morning and Epword sleepiness score (ESS) at daytime were measured prior to and during PAP treatment as well as between three selected PAP modes.

RESULTS

Compared with the parameters before ventilation therapies, all three variable modes of ventilation were associated with a higher nocturnal miniSpO₂ and sleep efficiency (all P < 0.01). Among the three variable modes, mode 3 resulted in not only the lowest arousal index and daytime ESS but also the highest sleep efficiency. Compared to mode 1, mode 2 demonstrated a significantly reduced AHI and an elevated miniSpO₂ and morning PaCO₂ (all P < 0.05), while mode 3 was associated with a decreased AHI, an increased miniSpO₂ (all P < 0.05), and no statistical change of PaCO₂ following the end of PAP treatment (P > 0.05). Comparison between mode 2 and mode 3 revealed that mode 3 had a significantly lower PaCO₂ (P < 0.05), but displayed no remarkable changes of AHI and miniSpO₂ (all P > 0.05).

CONCLUSION

Compared to fixed BiPAP ventilation, auto-trilevel PAP ventilation could more effectively correct hypercapnia, achieve lower index of nocturnal apnea and hypopnea, more improved sleep quality, and lower daytime sleepiness score. Auto-trilevel PAP ventilation is therefore more efficacious than conventional BiPAP ventilation in non-invasive ventilation therapy for OHS patients with concurrent moderate or severe OSAHS.

Efficacy of bilevel ventilatory support in the treatment of stable patients with obesity hypoventilation syndrome: systematic review and meta-analysis

OBJECTIVE

To systematically review the effects of bilevel ventilatory support (BVS) in patients with Obesity Hypoventilation Syndrome (OHS).

METHODS

A search of databases (MEDLINE accessed by PubMed, Cochrane CENTRAL, EMBASE and LILACS) was conducted from inception to June 2018. Randomized trials comparing BVS to other therapeutic modalities such as lifestyle counseling, continuous positive airway pressure (PAP) or BVS with average volume assured pressure support for the treatment of patients with OHS were included. The primary outcome was a change in daytime arterial carbon dioxide levels (PaCO₂). Secondary outcome measures included arterial partial pressure of oxygen (PaO₂), blood bicarbonate (HCO₃), percentage of total sleep time (TST) with oxygen saturation <90%, transcutaneous pressure of carbon dioxide (PtcCO₂), Epworth Sleepiness Scale (ESS), Medical Outcome Survey Short Form (SF36), Functional Outcomes of Sleep Questionnaire (FOSQ), Severe Respiratory Insufficiency Questionnaire (SRI), compliance with treatment, and weight loss.

RESULTS

Of 176 articles identified, seven studies were included. When BVS was compared to lifestyle counseling, the intervention was superior in improving PaCO₂ (-2.90 mmHg; 95%CI -4.28 to -1.52), PaO₂ (2.89 mmHg; 95%CI 0.33 to 5.46), HCO₃ (-2.55 mmol/L; 95%CI -3.28 to -1.81), percentage of TST<90% (-30.55%; 95%CI -37.98 to -23.12), ESS (-2.52; 95%CI -4.16 to -0.88) and FOSQ (6.33; 95%CI 1.78 to 10.88). However, when BVS was compared to other PAP modalities, there was no difference in any of the outcomes evaluated.

CONCLUSIONS

Treatment using BVS therapy is superior to lifestyle counseling. Different PAP modalities appear to be equally effective in improving outcomes. CRD42017065326.

Efficacy of bilevel positive airway pressure and continuous positive airway pressure therapy in patients with obesity hypoventilation syndrome: protocol for systematic review and meta-analysis

INTRODUCTION

Obesity hypoventilation syndrome (OHS) is a major respiratory complication caused by severe obesity, being associated with significant morbidity, negative impacts on quality of life and reduced survival if not treated appropriately. Positive airway pressure therapy is the first-line treatment for OHS although the optimal modality remains unclear. The goal of this study is to identify the efficacy of home bilevel positive airway pressure therapy by comparison to continuous positive airway pressure therapy and determine the best strategy for patients with OHS.

METHODS AND ANALYSIS

This study will be conducted following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols 2015 statement. We will search the following databases: PubMed, Web of Science, EMBASE, Cochrane Central Register of Controlled Trials and CINAHL. Ongoing studies will be identified through the ClinicalTrials.gov and WHO International Clinical Trials Registry Platform Search Portal. Grey literature will be recognised through Google Scholar and other search engines. Only randomised controlled trials meeting the eligibility criteria will be included. The risk of bias of the included studies will be evaluated through the Cochrane Collaboration's tool. RevMan V.5.3.5 software will be used for data analysis. The Q statistic and I² index will be used for investigating heterogeneity, and subgroup analysis or sensitivity analysis will be used to explore the source of heterogeneity. In addition, the Grading of Recommendations Assessment, Development and Evaluation system will be used to inspect the quality of evidence.

ETHICS AND DISSEMINATION

Ethics approval is not required because this study contains no primary data collected from humans. This systematic review and meta-analysis will be submitted to a peer-reviewed journal for publication.

PROSPERO REGISTRATION NUMBER

CRD42017078369.

Neural respiratory drive and cardiac function in patients with obesity hypoventilation syndrome following initiation of non-invasive ventilation

Background

Chronic hypercapnic respiratory failure (HRF) in obesity hypoventilation syndrome (OHS) is commonly treated using non-invasive ventilation (NIV). We hypothesised that treatment of OHS would improve neural respiratory drive index (NRDI) and cardiac function.

Methods

Fourteen patients (8 females) with OHS, who were admitted for initiation of domiciliary NIV, were prospectively studied. Patients had (mean ± SD): age (53±10 years), body mass index (BMI) (50.1±10.8 kg/m²), and pCO₂ (7.3±0.9 kPa). NRDI was assessed by surface electromyogram of the parasternal intercostals. Cardiac function was assessed by transthoracic echocardiography (TTE). All measurements were performed at baseline, 6 weeks, and 3 months.

Results

NRDI improved on day one following NIV set-up comparing to baseline (484.2±214.8 vs. 316.5±106.5 AU) and this improvement was maintained at 6 weeks (369.1±173.2 AU) and at 3 months (351.2±167.1 AU) (P=0.004). No significant differences were identified in terms of cardiac function between baseline and 3 months [tricuspid annular plane systolic excursion (TAPSE) (24.6±5.8 vs. 23.0±4.0 mm, P=0.317); systolic pulmonary artery (PA) pressures (36.7±15.2 vs. 44.5±23.9 mmHg, P=0.163].

Conclusions

NIV improves NRDI in patients with OHS, while the cardiac function over a three-month period remains unchanged.

Precapillary Pulmonary Hypertension and Sleep-Disordered Breathing: Is There a Link?

Among patients with sleep apnea the reported prevalence of precapillary pulmonary hypertension (PH) has varied largely, depending on patient selection, disease definition, and associated conditions, in particular chronic pulmonary disease. However, in the absence of comorbidities, PH seems to be rare in patients with sleep apnea. Conversely, sleep-related breathing disorders have been commonly found in patients with PH and they have been associated with an impaired quality of life. Since sleep-related breathing disorders may affect the pulmonary circulation and vice versa, patients with sleep-related breathing disorders should be evaluated for risk factors, symptoms and clinical signs of PH and right ventricular heart failure and patients with PH should be evaluated for sleep apnea. Therapeutic options for patients with sleep apnea and PH may include supplemental oxygen, drugs and positive pressure ventilation. Both nocturnal oxygen administration and acetazolamide have been shown to improve sleep apnea in patients with PH. In addition, oxygen therapy also improved exercise performance. Further studies are needed to corroborate the efficacy of these and other treatments.

Sleep Duration and Diabetes Risk: Population Trends and Potential Mechanisms

Sleep is important for regulating many physiologic functions that relate to metabolism. Because of this, there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. This research spans epidemiologic and laboratory studies. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor. This review describes the evidence linking sleep and diabetes risk at the population and laboratory levels.

Obesity: systemic and pulmonary complications, biochemical abnormalities, and impairment of lung function

Obesity is currently one of the major epidemics of this millennium and affects individuals throughout the world. It causes multiple systemic complications, some of which result in severe impairment of organs and tissues. These complications involve mechanical changes caused by the accumulation of adipose tissue and the numerous cytokines produced by adipocytes. Obesity also significantly interferes with respiratory function by decreasing lung volume, particularly the expiratory reserve volume and functional residual capacity. Because of the ineffectiveness of the respiratory muscles, strength and resistance may be reduced. All these factors lead to inspiratory overload, which increases respiratory effort, oxygen consumption, and respiratory energy expenditure. It is noteworthy that patterns of body fat distribution significantly influence the function of the respiratory system, likely via the direct mechanical effect of fat accumulation in the chest and abdominal regions. Weight loss caused by various types of treatment, including low-calorie diet, intragastric balloon, and bariatric surgery, significantly improves lung function and metabolic syndrome and reduces body mass index. Despite advances in the knowledge of pulmonary and systemic complications associated with obesity, longitudinal randomized studies are needed to assess the impact of weight loss on metabolic syndrome and lung function.