Oxidative stress and inflammatory markers in the exhaled breath condensate of children with OSA

Assessment of bone mineral density and bone metabolism in young men with obstructive sleep apnea: a cross-sectional study

BACKGROUND

Hypoxia in obstructive sleep apnea (OSA) patients during sleep may have an effect on bone metabolism. Few data regarding evaluation of bone metabolism in young individuals diagnosed with OSA. In this study, we aim to identify the association between bone mineral density and OSA in young men (≤ 40 years old of age).

METHODS

Consecutive male subjects who underwent polysomnography were enrolled. Serum calcium, 25-hydroxyvitamin-D3, β-isomerized form C-terminal telopeptide of type I collagen, osteocalcin and procollagen type 1 N-propeptide were measured in all participants, and bone mineral density (BMD) at lumbar spine (L1-L4), femoral neck and hip total were determined by dual energy X-ray absorption (DXA).

RESULTS

The population consisted of 85 subjects (mean age 35.53 years). The BMD at lumbar spine (L1-L4) in moderate OSA patients was higher than control and severe OSA group significantly (p = 0.036). After adjustment for confounding factors, stepwise multiple linear regression analyses showed LaSO₂ (β = 0.340, p = 0.008) as an independent explanatory variable for Lumbar L1-L4 BMD, LaSO₂ (β = 0.304, p = 0.037), BMI (β = 0.393, p = 0.008) for femur neck BMD and BMI (β = 0.720, p = 0.002) for hip total BMD.

CONCLUSIONS

Our finding indicated that there was a relationship between OSA and bone metabolism in younger men, and moderate OSA-related hypoxia positively related with BMD. This study also showed that different degrees of recurrent hypoxia had different effects on bone metabolism, a finding that required further investigation.

Can Weight Loss Improve the Cardiovascular Outcomes of Patients with Obesity and Obstructive Sleep Apnea?

Cardiovascular events are the primary cause of mortality in patients with obstructive sleep apnea and obesity. The rising prevalence of obstructive sleep apnea in recent decades has been linked to increasing rates of obesity. Obstructive sleep apnea has also been linked with many different cardiovascular diseases including coronary artery disease, stroke, heart failure, hypertension, and atrial fibrillation. Obesity is an increasing health concern globally, in part because obesity complications such as hypertension, diabetes, and obstructive sleep apnea increase the risk of cardiovascular diseases. More than 10% weight loss may be required to prevent or reverse obesity complications. Treatment approaches to obesity include nutritional therapy, exercise therapy, pharmacotherapy, and surgical therapies. This review intends to identify the effects of weight loss on cardiovascular outcomes in patients with obesity and obstructive sleep apnea. Despite the strong association between cardiovascular diseases and obstructive sleep apnea, randomized trials have failed to demonstrate that treatment of obstructive sleep apnea reduces cardiovascular events, even in patients with established cardiovascular diseases. Weight loss in patients with obstructive sleep apnea improves HbA1c, systolic blood pressure, HDL cholesterol, and triglycerides, but thus far no changes in cardiovascular events have been shown. The combination of weight loss with continuous positive airway pressure (CPAP) appears more beneficial than either treatment in isolation. Large well-controlled trials in patients with obstructive sleep apnea to assess the effects of different weight reduction programs on cardiovascular disease are still needed.

Prothrombotic Factors in Obstructive Sleep Apnea: A Systematic Review With Meta-Analysis

BACKGROUND

Previous studies revealed that the prothrombotic factors in patients with obstructive sleep apnea (OSA) remain controversial.

AIM/OBJECTIVE

The aim of the systematic review is to elucidate the relationship between prothrombotic factors and OSA.

MATERIALS AND METHODS

This systematic review was performed under the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The literature we investigated was extracted from 4 main medical databases (PubMed, Web of Science, Cochrane Library, and Chinese databases) as of February 2020. We used significant weighted mean differences (SMDs) with 95% CIs from random-effects model.

RESULTS

A total of 15 studies comprising 2190 patients were available for the meta-analysis. The pooled results showed that the levels of fibrinogen (SMD = 0.95, 95% CI = 0.26 to 1.65, P = .000), vascular endothelial growth factor (SMD = 0.37, 95% CI = -0.90 to 1.63, P = .000), and plasminogen activator inhibitor 1 (SMD = 0.61, 95% CI = 0.29 to 0.92, P = .040) increased in patients with OSA. There were no statistical differences between groups in terms of d-dimer (P = .108) and platelet counts (P = .233). Subgroup analyses demonstrated that specimen types and age could account for the heterogeneity.

CONCLUSIONS AND SIGNIFICANCE

This meta-analysis indicated the relationship between prothrombotic factors in OSA hypopnea. Obstructive sleep apnea-related effects may underline the importance of considering the dysfunction of the hemostatic system. The prothrombotic factors in OSA can influence making a choice of appropriate therapy.

Continuous positive airway pressure effectively ameliorates arrhythmias in patients with obstructive sleep apnea-hypopnea via counteracting the inflammation

INTRODUCTION

This work is aimed at evaluating the therapeutic effect of continuous positive airway pressure (CPAP) in treatment of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) combined with arrhythmias as well as clarifying the possible mechanism underpinning such an intervention.

METHODS

Through exclusions, a total of 108 OSAHS patients combined with arrhythmias were enrolled from June 2017 to June 2019 with full clinical information in this work. A computerized permuted block design with varying block stratification and size according to age, sex, AHI and type of arrhythmia was used to randomize 108 patients to CPAP versus sham CPAP for a period of 12-week. All were subjected to unchanged pharmacological anti-arrhythmia therapy combined with CPAP. Before and after CPAP treatment, the improvement of various arrhythmias was compared between the CPAP group and the sham-CPAP group. The levels of CRP, IL-6 and TNF-ɑ were measured simultaneously.

RESULTS

During follow-up, the mean (±SD) CPAP pressure used in the CPAP group was 12.3 (±3.1) cm H2O. The use of CPAP and sham CPAP was on average of 5.2 ± 0.56 and 5.1 ± 0.63 h/night, respectively. After 12 weeks of CPAP therapy, the AHI was significantly decreased and the lowest blood oxygen saturation was notably elevated in the CPAP group compared to the sham-CPAP group, P < 0.05. The CPAP therapy, compared with the sham-CPAP group, significantly reduced the incidence of all types of arrhythmia in patients with OSAHS. The level of the c-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) was significantly lower in the CPAP group than in the sham-CPAP group (P < 0.05). Pearson correlation analysis showed that the reduction in the incidence of total arrhythmias was positively correlated with the decrease of CRP, IL-6 and TNF-ɑ levels, respectively.

CONCLUSION

Findings from this work suggest that proper use of CPAP significantly benefits to OSAHS patients combined with arrhythmias, possibly via counteracting the inflammation.

Exhaled Breath Analysis in Obstructive Sleep Apnea Syndrome: A Review of the Literature

Background and Objectives: Obstructive sleep apnea syndrome (OSAS) represents an independent risk factor for cardiovascular, metabolic and neurological events. Polysomnography is the gold-standard for the diagnosis, however is expensive and time-consuming and not suitable for widespread use. Breath analysis is an innovative, non-invasive technique, able to provide clinically relevant information about OSAS. This systematic review was aimed to outline available evidence on the role of exhaled breath analysis in OSAS, taking into account the techniques’ level of adherence to the recently proposed technical standards. Materials and Methods: Articles reporting original data on exhaled breath analysis in OSAS were identified through a computerized and manual literature search and screened. Duplicate publications, case reports, case series, conference papers, expert opinions, comments, reviews and meta-analysis were excluded. Results: Fractional exhaled Nitric Oxide (FeNO) is higher in OSAS patients than controls, however its absolute value is within reported normal ranges. FeNO association with AHI is controversial, as well as its change after continuous positive airway pressure (C-PAP) therapy. Exhaled breath condensate (EBC) is acid in OSAS, cytokines and oxidative stress markers are elevated, they positively correlate with AHI and normalize after treatment. The analysis of volatile organic compounds (VOCs) by spectrometry or electronic nose is able to discriminate OSAS from healthy controls. The main technical issues regards the dilution of EBC and the lack of external validation in VOCs studies. Conclusions: Exhaled breath analysis has a promising role in the understanding of mechanisms underpinning OSAS and has demonstrated a clinical relevance in identifying individuals affected by the disease, in assessing the response to treatment and, potentially, to monitor patient’s adherence to mechanical ventilation. Albeit the majority of the technical standards proposed by the ERS committee have been followed by existing papers, further work is needed to uniform the methodology.

Circadian Dysregulation: The Next Frontier in Obstructive Sleep Apnea Research

OBJECTIVE

To review the effects of the circadian clock on homeostasis, the functional interaction between the circadian clock and hypoxia-inducible factors, and the role of circadian dysregulation in the progression of cardiopulmonary disease in obstructive sleep apnea (OSA).

DATA SOURCES

The MEDLINE database was accessed through PubMed.

REVIEW METHODS

A general review is presented on molecular pathways disrupted in OSA, circadian rhythms and the role of the circadian clock, hypoxia signaling, crosstalk between the circadian and hypoxia systems, the role of the circadian clock in cardiovascular disease, and implications for practice. Studies included in this State of the Art Review demonstrate the potential contribution of the circadian clock and hypoxia in animal models or human disease.

CONCLUSIONS

Molecular crosstalk between the circadian clock and hypoxia-inducible factors has not been evaluated in disease models of OSA.

IMPLICATIONS FOR PRACTICE

Pediatric OSA is highly prevalent and, if left untreated, may lead to cardiopulmonary sequelae. Changes in inflammatory markers that normally demonstrate circadian rhythmicity are also seen among patients with OSA. Hypoxia-inducible transcription factors interact with core circadian clock transcription factors; however, the interplay between these pathways has not been elucidated in the cardiopulmonary system. This gap in knowledge hinders our ability to identify potential biomarkers of OSA and develop alternative therapeutic strategies. A deeper understanding of the mechanisms by which OSA impinges on clock function and the impact of clock dysregulation on the cardiopulmonary system may lead to future advancements for the care of patients with OSA. The aim of this review is to shed light on this important clinical topic.

Non-volatile compounds in exhaled breath condensate: review of methodological aspects

In contrast to bronchial and nasal lavages, the analysis of exhaled breath condensate (EBC) is a promising, simple, non-invasive, repeatable, and diagnostic method for studying the composition of airway lining fluid with the potential to assess lung inflammation, exacerbations, and disease severity, and to monitor the effectiveness of treatment regimens. Recent investigations have revealed the potential applications of EBC analysis in systemic diseases. In this review, we highlight the analytical studies conducted on non-volatile compounds/biomarkers in EBC. In contrast to other related articles, this review is classified on the basis of analytical techniques and includes almost all the applied methods and their methodological limitations for quantification of non-volatile compounds in EBC samples, providing a guideline for further researches. The studies were identified by searching the SCOPUS database with the keywords "biomarkers," "non-volatile compounds," "determination method," and "EBC."

Sleep-Wake Disorders of Childhood

PURPOSE OF REVIEW

Sleep-wake disorders occur in 10% to 28% of children and differ somewhat in pathophysiology and management from sleep-wake disorders in adults. This article discusses the diagnosis and management of key childhood sleep disorders.

RECENT FINDINGS

The role of sleep in memory consolidation and in the facilitation of learning has been increasingly recognized, even at the toddler stage. Cataplexy, a key feature of narcolepsy type 1, may be subtle in childhood and characterized by transient muscle weakness isolated to the face. Children with obstructive sleep apnea and restless legs syndrome display prominent neurobehavioral symptoms such as daytime inattentiveness and hyperactivity, so it is important to elicit a sleep history when these symptoms are encountered. Systemic iron deficiency occurs in about two-thirds of children with restless legs syndrome and is easily treatable. Parasomnias arising out of non-rapid eye movement (REM) sleep, such as confusional arousals and sleepwalking, may be difficult to distinguish from nocturnal seizures, and, in many cases, video-EEG polysomnography is required to differentiate between causes.

SUMMARY

Clinicians should routinely integrate the assessment of sleep-wake function into their practices of neurology and child neurology because of the opportunity to improve the quality of life of their patients.

Cough hypersensitivity in patients with obstructive sleep apnea hypopnea syndrome

PURPOSE

The purpose of this study was to investigate cough hypersensitivity and its potential mechanisms in patients with obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

Fifteen OSAHS patients, 12 simple snoring patients, and 15 healthy volunteers received cough sensitivity test and induced sputum cytology. Cough thresholds C2 and C5 (the minimum of capsaicin inducing ≥ 2 and ≥ 5 coughs, respectively), total cell count, cell differentials and the levels of bradykinin, histamine, prostaglandin E₂, substance P, calcitonin gene-related peptide, pepsin, and interleukin-2 in the induced sputum detected by enzyme-linked immunosorbent assay were compared. The linear correlation between lgC2 and lgC5 and apnea hypopnea index, cell differentials, and inflammatory mediators in the induced sputum was calculated in OSAHS patients.

RESULTS

OSAHS patients presented with a significant lower C2 and C5 (P < 0.01), increased lymphocyte but decreased macrophage and neutrophil proportions in the induced sputum (P < 0.01), and higher contents of substance P, calcitonin gene-related peptide and interleukin-2 (P < 0.01) but similar levels of bradykinin, pepsin, prostaglandin E₂, and histamine (P > 0.05) in the supernatant of induced sputum, when compared with simple snoring patients and healthy volunteers. However, theses variable were comparable between simple snoring patients and healthy volunteers (P > 0.05). Finally, lgC2 or lgC5 was negatively related to apnea hypopnea index, lymphocyte percentage, and the levels of substance P, calcitonin gene-related peptide or interleukin-2 in the sputum (P < 0.01). There was a positive linear correlation between lymphocyte percentage and interleukin-2 level in the induced sputum (r = 0.63, P = 0.00).

CONCLUSION

OSAHS patients have a predisposition of cough hypersensitivity associated with airway inflammation.

Comparison of two exhaled biomarkers in children with and without sleep disordered breathing

OBJECTIVE

Airway oxidative stress and inflammation are likely to be involved in sleep disordered breathing (SDB) in children. We aimed to measure concentrations of 8-isoprostane (8-IsoP) in the exhaled breath condensate (EBC) and exhaled nitric oxide (FE_NO) in patients with SBD and healthy children, in order to assess the relationship between these two biomarkers, disease severity, and overnight changes.

METHODS

Patients with SDB (n = 46) and healthy controls (n = 20) aged 4.5-15.1 years (M/F: 36/30) underwent exhaled measurements. Patients with SDB underwent standard polysomnography to define primary snoring (PS: AHI < 1) and obstructive sleep apnea (OSA). Upon awakening the following morning, FE_NO was measured and EBC was collected for the measurement of EBC 8-IsoP.

RESULTS

OSA patients yielded higher awakening levels of 8-IsoP in EBC than PS patients and control subjects. The 8-IsoP levels, though not FE_NO, correlated with AHI (r = 0.40, p = 0.003) and SaO2 (r = -0.50, p = 0.001). Cut-off levels of 8-IsoP predicted OSA with a high AUC value (0.84, p = 0.000). Sensitivity and specificity for 8-IsoP levels above the percentile 50 (33.3 pg/mL) were 76.5% and 78.1%, respectively. 8-IsoP levels did not change from the evening to morning session, whereas morning FE_NO levels rose significantly only in patients with mild OSA (p = 0.03).

CONCLUSION

Levels of 8-IsoP, though not FE_NO, distinguish children with OSA from those with PS or healthy, correlate with disease severity and closely predict OSA in the whole sample.

Role of lung volume and airway inflammation in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent disorder that affects not only the upper airways but also the intrathoracic airways. In this review, we summarize the results of studies on lung function and airway inflammation. We provide evidence that the alterations in intrathoracic airways observed in OSA are not purely consequences of mechanical trauma and oxidative stress during apneic events but have a causal role in the structural changes associated with OSA and increasing severity of this disorder.

Red cell distribution width as a novel predictor of postoperative respiratory adverse events after adenotonsillectomy

BACKGROUND

Respiratory adverse events are commonly observed after adenotonsillectomy in children with sleep-disordered breathing. Preoperative prediction of these events enhances quality of care and resource management in facilities while encouraging precautions against them. Red cell distribution width, a measure of erythrocyte size variability, has recently been linked to adverse outcomes in a variety of disorders. Red cell distribution width has also been found to be associated with severity of obstructive sleep apnea in adults due to hypoxia-mediated inflammation.

AIM

The objective of this study was to evaluate whether elevated red cell distribution width is associated with postoperative respiratory adverse events in children with symptoms of sleep-disordered breathing.

METHODS

A prospective, observational, assessor-blinded study was conducted with consecutive children undergoing elective adenotonsillectomy for treatment of sleep-disordered breathing. Under general anesthesia, adenoidectomy was performed by curettage, and tonsillectomy was carried out by dissection. The primary outcome was the occurrence of an adverse event during emergence or in the postanesthesia care unit (PACU).

RESULTS

Among 287 patients, with mean ± sd age 7.49 ± 3.21, the frequency of respiratory complications during emergence was 62 (22.30%) and in PACU was 56 (20.14%). Mean ± sd red cell distribution width was 14.36 ± 1.06 in patients with complications and higher than that in those without complications 13.53 ± 0.59. Red cell distribution width had an adjusted odds ratio 7.28 (95% CI: 4.30-13.28) and area under the curve value 0.74 (95% CI: 0.67-0.81) to predict postoperative complications. A cutoff value for red cell distribution width was found to be 14.7.

CONCLUSION

Our study showed that preoperative elevated red cell distribution width is associated with an increased risk of respiratory adverse events in children undergoing adenotonsillectomy for sleep-disordered breathing.

A novel method for evaluation of oxidative stress in children with OSA

OBJECTIVES

To evaluate the role of adenotonsillar hypertrophy and the outcomes of adenotonsillectomy (AT) on oxidative stress for obstructive sleep apnea (OSA) in children using a new method; thiol/disulfide homeostasis.

METHODS

The study is consisted of 45 children with OSA and 38 healthy control subjects with similar age and sex. Children 3-12 years of age with OSA, defined as having an apnea/hypopnea index (AHI) of 5 or more in an overnight polysomnography, underwent adenotonsillectomy. OSA was classified as mild (1 ≤ AHI<10), moderate (10 ≤ AHI<20) or severe (AHI≥20). Venous blood samples were taken preoperatively and one month after surgery. The blood levels of thiol/disulfide homeostasis were assessed and compared between patients and control group, before and after adenotonsillectomy.

RESULTS

Body mass index (BMI), mean age and gender distribution were similar between the study and control groups. Statistically significant higher disulfide levels and ratios were found in the study group compared to the control group; in patients with moderate to severe OSA compared to mild OSA; in the preoperative period compared to postoperative period (p < 0.001, for all).

CONCLUSIONS

The current study provides preliminary evidence between oxidative stress and OSA in children with adenotonsillar. Adenotonsillectomy for OSA may result in a dramatic improvement in oxidative stress as measured by thiol/disulfide homeostasis.

Nocturnal hypoxia-induced oxidative stress promotes progression of pediatric non-alcoholic fatty liver disease

BACKGROUND & AIMS

Oxidative stress is proposed as a central mediator in NAFLD pathogenesis, but the specific trigger for reactive oxygen species generation has not been clearly delineated. In addition, emerging evidence shows that obesity related obstructive sleep apnea (OSA) and nocturnal hypoxia are associated with NAFLD progression in adults. The aim of this study was to determine if OSA/nocturnal hypoxia-induced oxidative stress promotes the progression of pediatric NAFLD.

METHODS

Subjects with biopsy proven NAFLD and lean controls were studied. Subjects underwent polysomnograms, liver histology scoring, laboratory testing, urine F(2)-isoprostanes (measure of lipid peroxidation) and 4-hydroxynonenal liver immunohistochemistry (in situ hepatic lipid peroxidation).

RESULTS

We studied 36 adolescents with NAFLD and 14 lean controls. The OSA/hypoxia group (69% of NAFLD subjects) had more severe fibrosis (64% stage 0-2; 36% stage 3) than those without OSA/hypoxia (100% stage 0-2), p=0.03. Higher F(2)-isoprostanes correlated with apnea/hypoxia index (r=0.39, p=0.03), % time SaO2 <90% (r=0.56, p=0.0008) and inversely with SaO2 nadir (r=-0.46, p=0.008). OSA/hypoxia was most severe in subjects with the greatest 4HNE staining (p=0.03). Increasing F(2)-isoprostanes(r=0.32, p=0.04) and 4HNE hepatic staining (r=0.47, p=0.007) were associated with worsening steatosis. Greater oxidative stress occurred in subjects with definite NASH as measured by F(2)-isoprostanes (p=0.06) and hepatic 4HNE (p=0.03) compared to those with borderline/not NASH.

CONCLUSIONS

These data support the role of nocturnal hypoxia as a trigger for localized hepatic oxidative stress, an important factor associated with the progression of NASH and hepatic fibrosis in obese pediatric patients.

LAY SUMMARY

Obstructive sleep apnea and low nighttime oxygen are associated with NAFLD progression in adults. In this study, we show that adolescents with NAFLD who have OSA and low oxygen have significant scar tissue in their livers. NAFLD subjects affected by OSA and low oxygen have a greater imbalance between the production of free radicals and their body's ability to counteract their harmful effects than subjects without OSA and low oxygen. This study shows that low oxygen levels may be an important trigger in the progression of pediatric NASH.

Update on paediatric obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is one of the most common causes of sleep-disordered breathing (SDB) in children. It is associated with significant morbidity, potentially impacting on long-term neurocognitive and behavioural development, as well as cardiovascular outcomes and metabolic homeostasis. The low grade systemic inflammation and increased oxidative stress seen in this condition are believed to underpin the development of these OSA-related morbidities. The significant variance in degree of end organ morbidity in patients with the same severity of OSA highlights the importance of the interplay of genetic and environmental factors in determining the overall OSA phenotype. This review seeks to summarize the current understanding of the aetiology and mechanisms underlying OSA, its risk factors, diagnosis and treatment.

Chronic Intermittent Hypoxia Induces Chronic Low-Grade Neuroinflammation in the Dorsal Hippocampus of Mice

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) induces cognitive impairment that involves intermittent hypoxia (IH). Because OSA is recognized as a low-grade systemic inflammatory disease and only some patients develop cognitive deficits, we investigated whether IH-related brain consequences shared similar pathophysiology and required additional factors such as systemic inflammation to develop.

DESIGN

Nine-week-old male C57BL/6J mice were exposed to 1 day, 6 or 24 w of IH (alternating 21-5% FiO2 every 30 sec, 8 h/day) or normoxia. Microglial changes were assessed in the functionally distinct dorsal (dH) and ventral (vH) regions of the hippocampus using Iba1 immunolabeling. Then the study concerned dH, as vH only tended to be lately affected. Seven proinflammatory and anti-inflammatory cytokine messenger RNA (mRNA) were assessed at all time points using semiquantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Similar mRNA analysis was performed after 6 w IH or normoxia associated for the past 3 w with repeated intraperitoneal low-dose lipopolysaccharide or saline.

MEASUREMENTS AND RESULTS

Chronic (6, 24 w) but not acute IH induced significant microglial changes in dH only, including increased density and morphological features of microglia priming. In dH, acute but not chronic IH increased IL-1β and RANTES/CCL5 mRNA, whereas the other cytokines remained unchanged. In contrast, chronic IH plus lipopolysaccharide increased interleukin (IL)-6 and IL10 mRNA whereas lipopolysaccharide alone did not affect these cytokines.

CONCLUSION

The obstructive sleep apnea component intermittent hypoxia (IH) causes low-grade neuroinflammation in the dorsal hippocampus of mice, including early but transient cytokine elevations, delayed but long-term microglial changes, and cytokine response alterations to lipopolysaccharide inflammatory challenge. These changes may contribute to IH-induced cognitive impairment and pathological brain aging.

Exhaled Breath Condensate: Technical and Diagnostic Aspects

Purpose. The aim of this study was to evaluate the 30-year progress of research on exhaled breath condensate in a disease-based approach. Methods. We searched PubMed/Medline, ScienceDirect, and Google Scholar using the following keywords: exhaled breath condensate (EBC), biomarkers, pH, asthma, gastroesophageal reflux (GERD), smoking, COPD, lung cancer, NSCLC, mechanical ventilation, cystic fibrosis, pulmonary arterial hypertension (PAH), idiopathic pulmonary fibrosis, interstitial lung diseases, obstructive sleep apnea (OSA), and drugs. Results. We found 12600 related articles in total in Google Scholar, 1807 in ScienceDirect, and 1081 in PubMed/Medline, published from 1980 to October 2014. 228 original investigation and review articles were eligible. Conclusions. There is rapidly increasing number of innovative articles, covering all the areas of modern respiratory medicine and expanding EBC potential clinical applications to other fields of internal medicine. However, the majority of published papers represent the results of small-scale studies and thus current knowledge must be further evaluated in large cohorts. In regard to the potential clinical use of EBC-analysis, several limitations must be pointed out, including poor reproducibility of biomarkers and absence of large surveys towards determination of reference-normal values. In conclusion, contemporary EBC-analysis is an intriguing achievement, but still in early stage when it comes to its application in clinical practice.

Nasal nitric oxide in sleep-disordered breathing in children

BACKGROUND

Inflammation plays a role in the pathogenesis and consequences of sleep-disordered breathing (SDB). The nasal mucosa and paranasal sinuses produce high levels of nitric oxide (NO). In asthma, exhaled NO is a marker of airway inflammation. There is only limited information whether nasal NO (nNO) accompanies also chronic upper airway obstruction, specifically, SDB. The objective of this study was to investigate nNO levels in children with SDB in comparison to healthy non-snoring children.

METHODS

Nasal NO was measured in children who underwent overnight polysomnographic studies due to habitual snoring and suspected SDB and in healthy non-snoring controls.

RESULTS

One hundred and eleven children participated in the study: 28 with obstructive sleep apnea (OSA), 60 with primary snoring (PS), and 23 controls. Nasal NO levels were significantly higher in children with OSA and PS compared to controls (867.4 ± 371.5, 902.0 ± 330.9, 644.1 ± 166.5 ppb, respectively, p = 0.047). No difference was observed between children with OSA and PS. No correlations were found between nNO levels and any of the PSG variables, nor with age, BMI percentile or tonsils size.

CONCLUSIONS

Compared to healthy controls, nNO is increased in children with SDB, but it is not correlated with disease severity. This is probably due to the local mechanical processes and snoring.

Diagnostic capability of biological markers in assessment of obstructive sleep apnea: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review is to evaluate the diagnostic value of biological markers (exhaled breath condensate, blood, salivary and urinary) in the diagnosis of OSA in comparison to the gold standard of nocturnal PSG.

METHODS

Studies that differentiated OSA from controls based on PSG results, without age restriction, were eligible for inclusion. The sample of selected studies could include studies in obese patients and with known cardiac disease. A detailed individual search strategy for each of the following bibliographic databases was developed: Cochrane, EMBASE, MEDLINE, PubMed, and LILACS. The references cited in these articles were also crosschecked and a partial grey literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies.

RESULTS

After a two-step selection process, nine articles were identified and subjected to qualitative and quantitative analyses. Among them, only one study conducted in children and one in adults found biomarkers that exhibit sufficiently satisfactory diagnostic accuracy that enables application as a diagnostic method for OSA.

CONCLUSION

Kallikrein-1, uromodulin, urocotin-3, and orosomucoid-1 when combined have enough accuracy to be an OSA diagnostic test in children. IL-6 and IL-10 plasma levels have potential to be good biomarkers in identifying or excluding the presence of OSA in adults.

Biomarkers associated with obstructive sleep apnea: A scoping review

The overall validity of biomarkers in the diagnosis of obstructive sleep apnea (OSA) remains unclear. We conducted a scoping review to provide assessments of biomarkers characteristics in the context of obstructive sleep apnea (OSA) and to identify gaps in the literature. A scoping review of studies in humans without age restriction that evaluated the potential diagnostic value of biological markers (blood, exhaled breath condensate, salivary, and urinary) in the OSA diagnosis was undertaken. Retained articles were those focused on the identification of biomarkers in subjects with OSA, the latter being confirmed with a full overnight or home-based polysomnography (PSG). Search strategies for six different databases were developed. The methodology of selected studies was classified using an adaptation of the evidence quality criteria from the American Academy of Pediatrics. Additionally the biomarkers were classified according to their potential clinical application. We identified 572 relevant studies, of which 117 met the inclusion criteria. Eighty-two studies were conducted in adults, 34 studies involved children, and one study had a sample composed of both adults and children. Most of the studies evaluated blood biomarkers. Potential diagnostic biomarkers were found in nine pediatric studies and in 58 adults studies. Only nine studies reported sensitivity and specificity, which varied substantially from 43% to 100%, and from 45% to 100%, respectively. Studies in adults have focused on the investigation of IL-6, TNF-α and hsCRP. There was no specific biomarker that was tested by a majority of authors in pediatric studies, and combinatorial urine biomarker approaches have shown preliminary promising results. In adults IL-6 and IL-10 seem to have a favorable potential to become a good biomarker to identify OSA.

Oxidative stress in children with obstructive sleep apnea syndrome

STUDY OBJECTIVES

Pediatric obstructive sleep apnea (OSA) is associated with cardiovascular consequences, including accelerated atherosclerosis and endothelial dysfunction. Increased lipid peroxidation, a marker of oxidative stress, has been identified in adults with OSA in a severity-dependent manner, with attenuation following treatment with continuous positive airway pressure therapy. Studies on oxidative stress in children with OSA are sparse and results are inconclusive. The objective of this study was to compare lipid peroxidation in children with OSA to non-OSA children.

METHODS

A prospective cross-sectional study of 26 children with polysomnography-confirmed OSA (oAHI ≥ 5/h TST) was conducted. Thirty age- and body mass index z-score-matched children with primary snoring (PS) served as a comparison group (oAHI ≤ 1/h TST). Fasting blood samples were obtained on the morning following the sleep study. Plasma oxidized low-density lipoprotein (oxLDL) concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

There were no group differences in patient characteristics and their lipid profiles. The mean oxLDL levels of the OSA group were significantly higher than those of the comparison group (53.1 ± 13.0 vs. 45.7 ± 10.0 U/L, respectively, p = 0.02). There was a significant positive correlation between plasma oxLDL and the apnea hypopnea index (r = 0.29, p = 0.03) and between oxLDL and the oxygen desaturation index (r = 0.51, p = 0.003), and a significant negative correlation between SpO2 nadir and oxLDL (r = -0.29, p = 0.03).

CONCLUSIONS

OSA in children is associated with increased lipid peroxidation in a severity-dependent manner. Lipid peroxidation levels correlate with the degree of intermittent hypoxia.

Inflammatory markers and obstructive sleep apnea in obese children: the NANOS study

Introduction. Obesity and obstructive sleep apnea syndrome (OSA) are common coexisting conditions associated with a chronic low-grade inflammatory state underlying some of the cognitive, metabolic, and cardiovascular morbidities. Aim. To examine the levels of inflammatory markers in obese community-dwelling children with OSA, as compared to no-OSA, and their association with clinical and polysomnographic (PSG) variables. Methods. In this cross-sectional, prospective multicenter study, healthy obese Spanish children (ages 4–15 years) were randomly selected and underwent nocturnal PSG followed by a morning fasting blood draw. Plasma samples were assayed for multiple inflammatory markers. Results. 204 children were enrolled in the study; 75 had OSA, defined by an obstructive respiratory disturbance index (RDI) of 3 events/hour total sleep time (TST). BMI, gender, and age were similar in OSA and no-OSA children. Monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) levels were significantly higher in OSA children, with interleukin-6 concentrations being higher in moderate-severe OSA (i.e., AHI > 5/hrTST; P < 0.01), while MCP-1 levels were associated with more prolonged nocturnal hypercapnia (P < 0.001). Conclusion. IL-6, MCP-1, and PAI-1 are altered in the context of OSA among community-based obese children further reinforcing the proinflammatory effects of sleep disorders such as OSA. This trial is registered with ClinicalTrials.gov NCT01322763.

Exhaled biomarker pattern is altered in children with obstructive sleep apnoea syndrome

OBJECTIVES

Obstructive sleep apnoea syndrome (OSAS) is a common disorder in children, which is associated with enhanced inflammatory status. Inflammation-associated changes could be monitored by the assessment of exhaled biomarker profile. This study aimed to compare the exhaled biomarker profile in children with OSAS and habitual snorers.

METHODS

Eighteen children with OSAS (8 ± 2 years, mean ± SD) and ten non-OSAS subjects with habitual snoring (9 ± 2 years) were recruited. Exhaled breath was collected from the lower airways, processed using an electronic nose (E-nose) and analyzed off-line using principal component analysis, followed by discrimination analysis and logistic regression to build a receiver operating characteristic (ROC) curve.

RESULTS

Exhaled biomarker pattern of OSAS patients was discriminated from that of control subjects (p = 0.03, cross-validation accuracy: 64%), ROC curve analysis (area: 0.83) showed 78% sensitivity and 70% specificity.

CONCLUSIONS

The altered exhaled biomarker pattern in OSAS might reflect accelerated airway and/or systemic inflammation in diseased state. Breath pattern analysis by an E-nose can serve as a new tool to monitor inflammation in children with OSAS.

Pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent sleep disorder, characterized by repeated disruptions of breathing during sleep. This disease has many potential consequences including excessive daytime sleepiness, neurocognitive deterioration, endocrinologic and metabolic effects, and decreased quality of life. Patients with OSAS experience repetitive episodes of hypoxia and reoxygenation during transient cessation of breathing that provoke systemic effects. Furthermore, there may be increased levels of biomarkers linked to endocrine-metabolic and cardiovascular alterations. Epidemiological studies have identified OSAS as an independent comorbid factor in cardiovascular and cerebrovascular diseases, and physiopathological links may exist with onset and progression of heart failure. In addition, OSAS is associated with other disorders and comorbidities which worsen cardiovascular consequences, such as obesity, diabetes, and metabolic syndrome. Metabolic syndrome is an emerging public health problem that represents a constellation of cardiovascular risk factors. Both OSAS and metabolic syndrome may exert negative synergistic effects on the cardiovascular system through multiple mechanisms (e.g., hypoxemia, sleep disruption, activation of the sympathetic nervous system, and inflammatory activation). It has been found that CPAP therapy for OSAS provides an objective improvement in symptoms and cardiac function, decreases cardiovascular risk, improves insulin sensitivity, and normalises biomarkers. OSAS contributes to the pathogenesis of cardiovascular disease independently and by interaction with comorbidities. The present review focuses on indirect and direct evidence regarding mechanisms implicated in cardiovascular disease among OSAS patients.

Current treatment of selected pediatric sleep disorders

While pediatric sleep disorders are relatively common, treatments are often not straightforward. There is often a paucity of gold standard studies and data available to guide clinicians, treatments may yield arguably incomplete results, interventions may require chronic use, and/ or involve multiple modalities including behavioral interventions that require high parental and family commitment. This review points out diagnostic differences compared to adults and focuses on current therapy for selected common pediatric sleep disorders including sleep disordered breathing/ obstructive sleep apnea, narcolepsy, and restless legs syndrome. Other common pediatric sleep disorders, such as insomnia and parasomnias, are not covered.

Lung oxidative damage by hypoxia

One of the most important functions of lungs is to maintain an adequate oxygenation in the organism. This organ can be affected by hypoxia facing both physiological and pathological situations. Exposure to this condition favors the increase of reactive oxygen species from mitochondria, as from NADPH oxidase, xanthine oxidase/reductase, and nitric oxide synthase enzymes, as well as establishing an inflammatory process. In lungs, hypoxia also modifies the levels of antioxidant substances causing pulmonary oxidative damage. Imbalance of redox state in lungs induced by hypoxia has been suggested as a participant in the changes observed in lung function in the hypoxic context, such as hypoxic vasoconstriction and pulmonary edema, in addition to vascular remodeling and chronic pulmonary hypertension. In this work, experimental evidence that shows the implied mechanisms in pulmonary redox state by hypoxia is reviewed. Herein, studies of cultures of different lung cells and complete isolated lung and tests conducted in vivo in the different forms of hypoxia, conducted in both animal models and humans, are described.

Obstructive sleep apnea and dyslipidemia: evidence and underlying mechanism

INTRODUCTION

Over the past half century, evidence has been accumulating on the emergence of obstructive sleep apnea (OSA), the most prevalent sleep-disordered breathing, as a major risk factor for cardiovascular disease. A significant body of research has been focused on elucidating the complex interplay between OSA and cardiovascular risk factors, including dyslipidemia, obesity, hypertension, and diabetes mellitus that portend increased morbidity and mortality in susceptible individuals.

CONCLUSION

Although a clear causal relationship of OSA and dyslipidemia is yet to be demonstrated, there is increasing evidence that chronic intermittent hypoxia, a major component of OSA, is independently associated and possibly the root cause of the dyslipidemia via the generation of stearoyl-coenzyme A desaturase-1 and reactive oxygen species, peroxidation of lipids, and sympathetic system dysfunction. The aim of this review is to highlight the relationship between OSA and dyslipidemia in the development of atherosclerosis and present the pathophysiologic mechanisms linking its association to clinical disease. Issues relating to epidemiology, confounding factors, significant gaps in research and future directions are also discussed.

Bone mineral density in patients with obstructive sleep apnea syndrome

PURPOSE

Obstructive sleep apnea syndrome (OSAS) is a disorder that is characterized by repetitive pauses in breathing during sleep. Airway obstruction episodes can lead to ischemia or hypoxia in tissues. Hypoxia may also have an effect on bone metabolism. In this study, we aim to investigate both the bone metabolic abnormalities and bone mineral density (BMD) in OSAS patients compared to individuals without OSAS.

METHODS

Twenty-one male patients with OSAS and 26 control subjects, also male, enrolled in this study. Serum calcium, phosphorus, alkaline phosphatase, and urinary desoxypiridinoline levels were measured in all participants, and BMD was evaluated using DEXA (Hologic QDR 2000). The BMD was measured in the lumbar spine (L1-L4), the femoral neck, and total femur region.

RESULTS

No statistically significant difference was noted between the two groups with respect to demographic data, except for body mass index (BMI). We adjusted the statistical analyses in line with the BMI and noted significant differences between OSAS patients and control subjects with regard to lumbar L1-L4 t score, lumbar L1-L4 BMD, and femoral neck BMD values (p ≤ 0.001). We find significant correlations with lumbar L1-L4 BMD (r = -0.4; p = 0.023) and lumbar L1-L4 t score values (r = -0.5; p = 0.012).

CONCLUSION

Our study indicates that there is a relationship between OSAS and osteoporosis. However, further controlled studies comprising a greater number of patients are needed to investigate the relationship between osteoporosis and OSAS.