Bronchial hyperreactivity and airway wall thickening in obstructive sleep apnea patients

Knowledge and Attitudes Toward Obstructive Sleep Apnea Among Korean Pulmonologists: A Nationwide Survey

BACKGROUND

Obstructive sleep apnea (OSA) significantly impacts cardiovascular, metabolic, and respiratory health. In Korea, OSA patients are treated by specialists in internal medicine, otolaryngology, neurology, and psychiatry, but the participation rate of pulmonologists in OSA management is relatively low compared to other specialties. This study investigated the knowledge and attitudes about OSA among Korean pulmonologists.

MATERIALS AND METHODS

An online survey was conducted, targeting respiratory specialists listed in the Korean Academy of Tuberculosis and Respiratory Diseases directory. The survey used the validated "Obstructive Sleep Apnea Knowledge and Attitudes" (OSAKA) questionnaire, which consists of questions about knowledge and attitudes on OSA. To maximize participation, email invitations were sent three times to the target audience.

RESULTS

Out of 634 queried pulmonologists, 127 (20%) responded to the survey. The mean age of respondents was 45.4 ± 8.6 years. The respondents' years of specialty acquisition ranged from the 1980s to the 2010s. Additionally, 74 (58.3%) held a doctor's degree, and 96 (75.6%) worked in hospitals with a sleep center. Furthermore, 71 (55.9%) of the pulmonologists reported having experience with OSA patients. Pulmonologists with experience managing OSA patients had significantly higher knowledge and attitude scores compared to those without such experience. Interestingly, older respondents and those who completed their pulmonology training earlier had higher attitude scores. In addition, the knowledge score significantly correlated with responses to the five items of the attitude questionnaire.

CONCLUSION

This study provides valuable insights into the knowledge and attitudes of Korean pulmonologists regarding OSA. The findings indicate that their knowledge levels are comparable to or better than those in previous studies. These results underscore the need for targeted educational programs and practical training, especially for younger pulmonologists, to enhance their proficiency in managing OSA and to encourage a more active role in its treatment.

Revisiting Asthma Obstructive Sleep Apnea Overlap: Current Knowledge and Future Needs

Asthma and obstructive sleep apnea are highly prevalent conditions with a high cost burden. In addition to shared risk factors, existing data suggest a bidirectional relationship between asthma and OSA, where each condition can impact the other. Patients with asthma often complain of sleep fragmentation, nocturnal asthma symptoms, daytime sleepiness, and snoring. The prevalence of OSA increases with asthma severity, as evidenced by multiple large studies. Asthma may lower the threshold for arousal in OSA, resulting in the hypopnea with arousal phenotype. Epidemiologic studies in adults have shown that OSA is associated with worse asthma severity, increased frequency of exacerbation, and poor quality of life. The current literature assessing the relationship among OSA, asthma, and CPAP therapy is heavily dependent on observational studies. There is a need for randomized controlled trials to minimize the interference of confounding shared risk factors.

Prevalence of bronchial wall thickening and collapse in brachycephalic dogs with and without brachycephalic obstructive airway syndrome and in nonbrachycephalic dogs

OBJECTIVE

To assess the prevalence of bronchial wall thickening (BWT) and collapse in brachycephalic dogs with and without brachycephalic obstructive airway syndrome (BOAS) and in nonbrachycephalic dogs.

ANIMALS

85 dogs with no history of lower respiratory tract disease that underwent CT of the thorax.

PROCEDURES

Electronical medical records for March 2011 through August 2019 were reviewed to identify brachycephalic dogs with BOAS (BOAS group) and brachycephalic dogs without BOAS (BDWB group) that did not have any evidence of lower respiratory tract disease and had undergone thoracic CT. A population of nonbrachycephalic dogs of similar weight (control dogs) was also retrospectively recruited.

RESULTS

BWT was identified in 28 of 30 (93.3%; 95% CI, 80.3% to 98.6%) dogs in the BOAS group, 15 of 26 (57.7%; 95% CI, 38.7% to 75.0%) dogs in the BDWB group, and 10 of 28 (35.7%; 95% CI, 20.1% to 54.2%) control dogs. On multivariable analysis, only brachycephalic conformation (P < 0.01) and body weight (P = 0.02) were significantly associated with the presence of BWT. Bronchial collapse was identified in 17 of 30 (56.7%; 95% CI, 39.0% to 73.1%) dogs in the BOAS group, 17 of 26 (65.4%; 95% CI, 46.3% to 81.3%) dogs in the BDWB group, and 3 of 28 (10.7%; 95% CI, 3.1% to 25.9%) control dogs. On multivariable analysis, only brachycephalic conformation was significantly (P < 0.01) associated with the presence of bronchial collapse.

CLINICAL RELEVANCE

A relationship between brachycephalic conformation and body weight with BWT was established, with heavier dogs having thicker bronchial walls. However, further studies are required to investigate the cause. Bronchial collapse was also more common in dogs with brachycephalic conformation, which is in agreement with the previously published literature.

Airway hyperresponsiveness induced by intermittent hypoxia in rats

This study investigated whether intermittent hypoxia (IH) induces airway hyperresponsiveness (AHR) and associated with lung inflammation. Male Brown Norway rats were exposed to 14-day IH or room air (RA) for 6 h/day. One day after the last exposure, total lung resistance to various doses of methacholine was measured as an index of bronchoconstrictive responses. Compared with RA controls, methacholine significantly induced an augmented bronchoconstriction in IH-exposed rats. Moreover, IH exposure evoked lung inflammation which was reflected by increased inflammatory cell infiltration, concentrations of interleukin-6 and prostaglandin E₂ in bronchoalveolar lavage fluid, and lung lipid peroxidation. IH-induced AHR and lung inflammation were completely abolished by daily intraperitoneal injection of N-acetylcysteine (an antioxidant) or ibuprofen (a cyclooxygenase inhibitor), but not by apocynin (an inhibitor of NADPH oxidase) or vehicle. In conclusion, AHR and lung inflammation occur after 14-day IH exposure, with endogenous reactive oxygen species and cyclooxygenase metabolites being responsible for these responses.

A community study of the risk for obstructive sleep apnea and respiratory inflammation in an adult Chinese population

Objectives: We aimed to investigate the relationship between obstructive sleep apnea (OSA) risk and respiratory inflammation evaluated by the exhaled breath condensate (EBC) interleukin-6 (IL-6) and plasma surfactant protein-D (SP-D), based on the Berlin questionnaire (BQ) screening values in an adult, urban community in Beijing, China.Methods: Volunteers aged >40 years were recruited from the Shichahai community of central Beijing (Registration number: NCT04832711). Their general information and disease history were recorded. OSA risk was assessed using the BQ. IL-6 in EBC and plasma SP-D were d etected by enzyme-linked immunoassay through specimens collected while fasting. The differences in IL-6 and SP-D values between high-risk and low-risk groups for OSA were compared, and the factors affecting their values were analyzed.Results: Among 1,239 participants, 18.8% of participants were in the high-risk group. There were more participants with higher body mass index, chronic hypertension, coronary heart disease, and diabetes in the high-risk group than in the low-risk group (P < 0.05). There were no significant differences in EBC IL-6 and plasma SP-D between the high- and low-OSA risk groups (p > 0.05). After adjustment for age, sex and chronic comorbidities, multivariate logistic regression showed that there was no correlation between risk of OSA and IL-6 in EBC. However, the risk of OSA (odds ratio [OR] [95% CI]: 1.69 [1.15,2.48]; β = 0.522) and BMI (OR [95%CI]: 0.94 [0.91,0.98]; β = -0.061) were independently associated with plasma SP-D level (p < 0.05 for both). Stratification analysis showed that OSA risk were independently associated with plasma SP-D levels in participants <65 years, or men, or participants with BMI<25.Conclusion: This study showed that plasma SP-D, an inflammation biomarker, was associated with risk of OSA and BMI in a Chinese central urban community.The relationship between the risk of OSA and respiratory inflammation in community populations needs to be further evaluated.

Cardiopulmonary Status in Adults with Osteogenesis Imperfecta: Intrinsic Lung Disease May Contribute More Than Scoliosis

BACKGROUND

Osteogenesis imperfecta (OI) is a heterogeneous group of collagen-related disorders characterized by osteopenia, bone fractures, spine deformities, and nonskeletal complications. Cardiopulmonary complications are the major cause of morbidity and mortality in adults with OI. The cause of such problems was often attributed solely to the presence of large scoliosis curves affecting pulmonary function and, indirectly, cardiovascular health. However, recent studies suggest this may not be the case. Therefore, determining the relationships and causative agents of cardiopulmonary problems in patients with OI, specifically pulmonary impairment, is important to improving the overall wellbeing, quality of life, and survival of these patients.

QUESTIONS/PURPOSES

(1) Is cardiopulmonary fitness in OI solely related to the presence of scoliosis? (2) What is the prevalence of heart and lung complications in this adult population? (3) Does the presence of pulmonary impairment impact quality of life in adults with OI?

METHODS

This is a prospective observational cross-sectional study. Within 1 year, each participant (n = 30) completed pulmonary function testing, echocardiogram, ECG, chest CT, AP spine radiography, and quality-of-life assessments (SF-36, St. George's Respiratory Questionnaire, Functional Outcomes of Sleep Questionnaire, and Pittsburgh Sleep Quality Index). In terms of pulmonary function, we differentiated restrictive and obstructive physiology using the ratio of forced expiratory volume over one second to forced vital capacity (FEV1/FVC), with restrictive lung physiology defined as FEV1/FVC > 0.8 and obstructive lung physiology as FEV1/FVC < 0.7. Spine radiographs were evaluated for scoliosis. Chest CT images were reviewed to qualitatively assess the lungs. The statistical analysis involved a Kruskall-Wallis test with Bonferroni's correction and a bivariate correlation analysis using Spearman's rho correlation coefficient (p < 0.05).

RESULTS

Sixteen of 23 participants with restrictive lung physiology had scoliosis; their ages ranged from 19 years to 67 years. There was no correlation between the magnitude of the scoliosis curve and deficient pulmonary function (R = 0.08; p = 0.68). Seven participants had normal pulmonary function. The average scoliosis curve was 44 ± 29°. Thirteen participants had abnormal ECG findings while 10 had abnormal echocardiogram results. All but two individuals with abnormal chest CT results were found to have bronchial wall thickening. There were no differences in pulmonary or cardiac findings between OI types, except for FVC and total lung capacity, which were lower in individuals with Type III OI than in those with other types of OI. FEV1/FVC correlated with St. George's Respiratory Questionnaire (R = 0.429; p = 0.02) but not with Functional Outcomes of Sleep Questionnaire (R = -0.26; p = 0.19) or SF-36 scores (physical component summary: R = -0.037, p = 0.85; mental component summary: R = -0.204, p = 0.29).

CONCLUSIONS

The lack of a relationship between decreased pulmonary function and the severity of scoliosis suggests that restrictive lung physiology in this population is likely because of factors intrinsic to OI and not entirely because of thoracic cage deformities. The fact that pulmonary impairment influences self-perceived quality of life exemplifies how detrimental such complications may be to everyday functioning. This also reinforces the importance of determining the underlying cause of cardiopulmonary impairment in this population to set clear clinical guidelines of care.

LEVEL OF EVIDENCE

Level II, prognostic study.

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.

Circulating fibrinogen levels are elevated in patients with obstructive sleep apnea: a systemic review and meta-analysis

OBJECTIVE

Fibrinogen is believed to play a role in the pathophysiology of obstructive sleep apnea (OSA) and many studies have assessed circulating fibrinogen concentrations in OSA patients. However, the results from these studies were not consistent. To assess the association of circulating fibrinogen levels and OSA, a meta-analysis was performed.

METHODS

PubMed, Embase and Web of Science databases were searched for eligible studies. Data were extracted, and then weighted mean differences (WMDs) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 25 studies involving 1480 cases and 2312 controls were included in this meta-analysis. Combined data indicated that the circulating fibrinogen levels were higher in OSA patients than in controls (WMD: 0.38 g/L, 95% CI [0.29-0.47 g/L], p < 0.001; I² = 80.3%, p < 0.001). In the subgroup analyses by disease severity, there were similar results in mild-moderate OSA patients (WMD: 0.27 g/L, 95% CI [0.14-0.41 g/L], p < 0.001; I² = 29.3%, p = 0.185) and severe OSA patients (WMD: 0.54 g/L, 95% CI [0.28-0.79 g/L], p < 0.001; I² = 65.9%, p = 0.012). Furthermore, in another subgroup analysis, the circulating fibrinogen levels were higher in OSA patients than those in controls who were matched for important potential confounders (WMD: 0.41 g/L, 95% CI [0.21-0.60 g/L], p < 0.001; I² = 62.0%, p = 0.003).

CONCLUSIONS

This systematic review and meta-analysis reveals that circulating fibrinogen levels are elevated in patients with OSA.

Current opinions for the management of asthma associated with ear, nose and throat comorbidities

Ear, nose and throat (ENT) comorbidities are common in patients with asthma and are frequently associated with poorer asthma outcomes. All these comorbidities are "treatable traits" in asthma. Identification and management of these disorders may spare medication usage and contribute to improved asthma control and quality of life, and a decrease in exacerbation rates.This review summarises recent data about the prevalence, clinical impact and treatment effects of ENT comorbidities in asthma including allergic rhinitis, chronic rhinosinusitis with and without nasal polyposis, aspirin-exacerbated respiratory disease, obstructive sleep apnoea and vocal cord dysfunction.Many of these comorbidities are possible to be managed by the pulmonologist, but the collaboration with the ENT specialist is essential for patients with chronic rhinosinusitis or vocal cord dysfunction. Further rigorous research is needed to study the efficacy of comorbidity treatment to improve asthma outcomes, in particular with the development of biotherapies in severe asthma that can also be beneficial in some ENT diseases.

Estrogen Modulates the Sensitivity of Lung Vagal C Fibers in Female Rats Exposed to Intermittent Hypoxia

Obstructive sleep apnea is mainly characterized by intermittent hypoxia (IH), which is associated with hyperreactive airway diseases and lung inflammation. Sensitization of lung vagal C fibers (LVCFs) induced by inflammatory mediators may play a central role in the pathogenesis of airway hypersensitivity. In females, estrogen interferes with inflammatory signaling pathways that may modulate airway hyperreactivity. In this study, we investigated the effects of IH on the reflex and afferent responses of LVCFs to chemical stimulants and lung inflammation in adult female rats, as well as the role of estrogen in these responses. Intact and ovariectomized (OVX) female rats were exposed to room air (RA) or IH for 14 consecutive days. On day 15, IH enhanced apneic responses to right atrial injection of chemical stimulants of LVCFs (e.g., capsaicin, phenylbiguanide, and α,β-methylene-ATP) in intact anesthetized females. Rats subjected to OVX prior to IH exposure exhibited an augmented apneic response to the same dose of stimulants compared with rats subjected to other treatments. Apneic responses to the stimulants were completely abrogated by bilateral vagotomy or perivagal capsaicin treatment, which blocked the neural conduction of LVCFs. Electrophysiological experiments revealed that in IH-exposed rats, OVX potentiated the excitability of LVCFs to stimulants. Moreover, LVCF hypersensitivity in rats subjected to OVX prior to IH exposure was accompanied by enhanced lung inflammation, which was reflected by elevated inflammatory cell infiltration in bronchoalveolar lavage fluid, lung lipid peroxidation, and protein expression of inflammatory cytokines. Supplementation with 17β-estradiol (E2) at a low concentration (30 μg/ml) but not at high concentrations (50 and 150 μg/ml) prevented the augmenting effects of OVX on LVCF sensitivity and lung inflammation caused by IH. These results suggest that ovarian hormones prevent the enhancement of LVCF sensitivity and lung inflammation by IH in female rats, which are related to the effect of low-dose estrogen.

[Alterations of respiratory resistance in patients with obstructive sleep apnea hypopnea syndrome]

OBJECTIVE

To evaluate the association between the components of airway resistance and severity of obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

A total of 234 patients with snoring during sleep underwent full-night polysomnography in our center between January, 2015 and September, 2017. According to the apnea-hypopnea index (AHI) scores, the patients were divided into non-OSAHS group (AHI scores <5), mild or moderate OSAHS group (5-30) group, and severe OSAHS group (>30). The pulmonary function and respiratory resistance of the patients were assessed using spirometry and impulse oscillometry, respectively, and the correlation between the parameters of respiratory resistance and the severity of AHI were analyzed.

RESULTS

The non-OSAHS, mild or moderate OSAHS, and severe OSAHS groups consisted of 31, 90 and 113 patients, respectively. The patients with severe OSAHS had significantly higher levels of respiratory resistance at 5 Hz (R5) and 20 Hz (R20), FEF_50% and MMEF than those in the other two groups (P<0.05). Bivariate correlation analysis identified positive correlations of R5 (r=0.259, P=0.000), R20 (r=0.298, P=0.000) and FEF_50% (r=0.176, P=0.007) with AHI scores of the patients.

CONCLUSION

Patients with OSAHS have increased respiratory resistance in the large airways and compensatory reduction in small airway resistance.

Intermittent Hypoxia Contributes to the Lung Damage by Increased Oxidative Stress, Inflammation, and Disbalance in Protease/Antiprotease System

INTRODUCTION

Intermittent hypoxia as a surrogate of obstructive sleep apnea is associated with different cardiovascular complications. However, the effects of intermittent hypoxia on the lung tissue are less known. Therefore, the aim of our present study was to investigate if intermittent hypoxia may influence oxidative stress, inflammation, and protease/antiprotease system in the lung. Additionally, potential protective properties of anti-inflammatory and anti-oxidative drugs have been evaluated.

METHODS

32 mice were divided into four groups: (1) intermittent hypoxia, (2) intermittent hypoxia with infliximab, (3) intermittent hypoxia with L-glutathione, and (4) normoxia. After 4 weeks, lungs and blood were collected. Levels of reactive oxygen species in the lung were calculated by L-O12-enhanced chemiluminescence. CD68-positive lung macrophages were detected by immunofluorescence. Concentrations of elastase and desmosine in lung and of alpha-1-antitrypsin in blood were calculated by means of enzyme-linked immunosorbent assay.

RESULTS

Compared to a control, intermittent hypoxia augmented the release of free oxygen radicals, expression of CD68+ macrophages, and concentration of elastase in the lung tissue. Despite increased blood levels of protective alpha-1-antitrypsin, concentrations of desmosine-degradation product of elastin were higher versus control. The application of anti-inflammatory infliximab und anti-oxidative L-glutathione prevented at least partly the above-observed hypoxia-associated changes.

CONCLUSIONS

Intermittent hypoxia contributes to the lung damage by increased oxidative stress, inflammation, and disbalance in protease/antiprotease system. Infliximab and L-glutathione may prevent adverse hypoxia-induced lung alternations.

The clinical impact of non-obstructive chronic bronchitis in current and former smokers

BACKGROUND

As the clinical significance of chronic bronchitis among smokers without airflow obstruction is unclear, we sought to determine morbidity associated with this disorder.

METHODS

We examined subjects from the COPDGene study and compared those with FEV1/FVC ≥ 0.70, no diagnosis of asthma and chronic bronchitis as defined as a history of cough and phlegm production for ≥ 3 months/year for ≥ 2 years (NCB) to non-obstructed subjects without chronic bronchitis (CB-). Multivariate analysis was used to determine factors associated with and impact of NCB.

RESULTS

We identified 597 NCB and 4283 CB- subjects. NCB participants were younger (55.4 vs. 57.2 years, p < 0.001) with greater tobacco exposure (42.9 vs. 37.8 pack-years, p < 0.001) and more often current smokers; more frequently reported occupational exposure to fumes (52.8% vs. 42.2%, p < 0.001), dust for ≥ 1 year (55.3% vs. 42.0%, p < 0.001) and were less likely to be currently working. NCB subjects demonstrated worse quality-of-life (SGRQ 35.6 vs. 15.1, p < 0.001) and exercise capacity (walk distance 415 vs. 449 m, p < 0.001) and more frequently reported respiratory "flare-ups" requiring treatment with antibiotics or steroids (0.30 vs. 0.10 annual events/subject, p < 0.001) prior to enrollment and during follow-up (0.34 vs. 0.16 annual events/subject, p < 0.001). In multivariate analysis, current smoking, GERD, sleep apnea and occupational exposures were significantly associated with NCB.

CONCLUSIONS

While longitudinal data will be needed to determine whether NCB progresses to COPD, NCB patients have poorer quality-of-life, exercise capacity and frequent respiratory events. Beyond smoking cessation interventions, further research is warranted to determine the benefit of other therapeutics in this population. Clinical Trials Registration # NCT00608764 (http://clinicaltrials.gov/show/NCT00608764). Link to study protocol: http://www.copdgene.org/sites/default/files/COPDGeneProtocol-5-0_06-19-2009.pdf.

Serum inflammatory markers in obstructive sleep apnea: a meta-analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) has been linked to and is associated with increased cardiovascular and cerebrovascular morbidity. Ongoing inflammatory responses play an important role in this association. Multiple small size studies addressing the profile of the inflammatory markers in OSA are available therefore we performed a meta-analysis.

METHODS

Systematic review of medical literature was conducted using PubMed, Cochrane, and EMBASE databases from 1968 to 2011 by utilizing the key words obstructive sleep apnea, C-Reactive protein, tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 8 (IL-8), intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM) and Selectins. Inclusion criteria were: full text English articles; studies with adult population; reported values for at least one of the markers of interest; with at least two separate groups (subjects with OSA and control group); OSA was defined as AHI of ≥ 5/h.

RESULTS

Five hundred and twelve studies were reviewed for inclusion with 51 studies pooled for analysis (30 studies for CRP, 19 studies for TNF-α, 8 studies for ICAM, 18 studies for IL-6, six studies for VCAM and 5 studies for Selectins). The levels of inflammatory markers were higher in patients with OSA compared to control group. Standardized pooled Mean differences were calculated to be 1.77 for CRP, 1.03 for TNF-α, 2.16 for IL-6, 4.22 for IL-8, 2.93 for ICAM, 1.45 for Selectins and 2.08 for VCAM.

CONCLUSIONS

In this meta-analysis, the levels of systemic inflammatory markers were found to be higher in OSA patients compared to control subjects.

Obstructive sleep apnea and asthma: associations and treatment implications

Obstructive sleep apnea (OSA) and asthma are highly prevalent respiratory disorders and are frequently co-morbid. Risk factors common to the two diseases include obesity, rhinitis, and gastroesophageal reflux (GER). Observational and experimental evidence implicates airways and systemic inflammation, neuromechanical effects of recurrent upper airway collapse, and asthma-controlling medications (corticosteroids) as additional explanatory factors. Therefore, undiagnosed or inadequately treated OSA may adversely affect control of asthma and vice versa. It is important for clinicians to be vigilant and specifically address weight-control, nasal obstruction, and GER in these populations. Utilizing validated screening instruments to affirm high risk of co-morbid OSA or asthma in persistently symptomatic patients will allow clinicians to cost-effectively test and treat appropriate patients, potentially improving outcomes. While non-invasive ventilation in acute asthma improves outcomes, the role of chronic continuous positive airway pressure (CPAP; the first-line treatment for OSA) in improving long-term asthma control is not known. Future research should focus on the impact of optimal CPAP therapy and adherence on asthma symptoms and outcomes.

Effect of continuous positive airway pressure on day/night rhythm of prothrombotic markers in obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with an increased risk of atherothrombotic events. A prothrombotic state might partially explain this link. This study investigated OSA patients' day/night rhythm of several prothrombotic markers and their potential changes with therapeutic continuous positive airway pressure (CPAP).

METHODS

The study included 51 OSA patients [apnea hypopnea index (AHI) ⩾10] and 24 non-OSA controls (AHI<10). Of the 51 OSA patients, 25 were randomized to CPAP and 26 to placebo-CPAP. Twelve blood samples were collected over a 24h period to measure prothrombotic markers. For the apneic patients these samples were collected before treatment and after 3weeks of treatment with either CPAP or placebo-CPAP. Day/night variation in prothrombotic markers was examined using a cosinor analysis.

RESULTS

Compared with controls, OSA patients showed lower mesor (mean) and amplitude (difference between maximum and minimum activity) of D-dimer. In unadjusted (but not in adjusted) analysis, patients showed higher mesor of plasminogen activator inhibitor-1 (p<0.05 in all cases). No significant group differences were seen in mesor and amplitude for either soluble tissue factor or von Willebrand factor, or the acrophase (time of the peak) and periodic pattern for any prothrombotic markers. There were no significant differences in changes of periodic pattern and in day/night rhythm parameters of prothrombotic markers pre- to post-treatment between the CPAP and placebo condition.

CONCLUSIONS

There may be altered day/night rhythm of some prothrombotic markers in OSA patients compared with controls. CPAP treatment for 3weeks did not affect day/night rhythm of prothrombotic markers in OSA patients differently from placebo-CPAP.

Analysis of systemic and airway inflammation in obstructive sleep apnea

PURPOSE

The presence of both systemic and airway inflammation has been suggested in obstructive sleep apnea (OSA) by increased levels of inflammatory biomarkers in the circulation and respiratory specimens. We aimed to investigate the relationship between systemic and airway inflammation in OSA.

METHODS

This study was conducted by simultaneously measuring various biomarkers both in serum and induced sputum of 43 patients. We compared the relationships of these biomarker levels with polysomnographic data and obesity measurements and also investigated their interrelationships between systemic and local compartments. We also assessed the relation of inflammatory markers with proximal airway resistance measured by impulse oscillometry.

RESULTS

In multiple regression analyses, each measured serum biomarker [leptin, interleukin-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF)] significantly correlated with waist circumference or fat area determined by computed tomography. In contrast, regarding airway inflammation, sputum IL-6, IL-8, TNF-α, and VEGF significantly correlated with OSA severity as indicated by the respiratory disturbance index or oxygen desaturation indices. Sputum IL-6, IL-8, TNF-α, and VEGF were significantly related to sputum neutrophil number, and sputum IL-8 and TNF-α were related to proximal airway resistance independently of body mass index. There were no significant interrelationships between the same biomarkers in serum and induced sputum.

CONCLUSIONS

Systemic and airway inflammation in OSA might be differently regulated by OSA itself and comorbid obesity, depending on the type of cytokine. Although we did not find apparent interrelationships between systemic and local compartments, further studies are needed to clarify this concept.

Chronic cough and OSA: a new association?

Chronic cough is defined as cough lasting more than 2 months. Common causes for chronic cough in nonsmokers with normal chest radiographs and pulmonary functions include gastroesophageal reflux disease (GERD), cough-variant asthma (CVA), and upper airway cough syndrome (UACS). Current guidelines recommend diagnosing the etiology of chronic cough based upon the results of therapy for suspected GERD, CVA, and UACS. Despite following current recommendations for diagnosis and treatment, the cause for a significant proportion of chronic cough remains unexplained.Recent reports indicate the resolution of chronic cough following treatment of concomitantly diagnosed obstructive sleep apnea (OSA). Whether this represents a co-occurrence of two commonly prevalent disorders or a pathophysiologic relationship between OSA and cough remains unknown. This review offers insights into a pathophysiologic link between OSA and the commonly purported etiologies for cough, namely, GERD, UACS, and CVA. In addition, evidence for a relationship between airway inflammation that can trigger or perpetuate cough and OSA is discussed. This review explores mechanisms by which nocturnal continuous positive airway therapy resolves cough by improving underlying airway inflammation secondary to OSA and impacts upon GERD, CVA, and UACS.

Increased sleep latency and reduced sleep duration in children with asthma

STUDY OBJECTIVE

Sleep disturbance is reported to be more prevalent in children and adolescents with asthma than those without. However, this has not been described adequately using objective measures. The aim of this study was to objectively characterise sleep disturbance in asthmatic and non-asthmatic children and adolescents.

METHODS

A retrospective analysis of polysomnography recordings from children aged 5-17 years old, with (n = 113) and without asthma (n = 104), referred for a sleep study over the period 2005-2010 at the Paediatric Sleep Unit, John Hunter Children's Hospital in Newcastle, NSW Australia, was carried out.

RESULTS

Polysomnographic recordings were analysed to compare sleep quality and quantity between asthmatic and non-asthmatic children. Sleep latency was significantly longer in asthmatic children compared to controls. However, this result was significant for females only (46.2 (5.6) vs 33.2 (2.7) min, p < 0.05). Male asthmatics had significantly shorter sleep duration (425.9 (5.4) vs 441.8 (5.4) min, p < 0.05) than male controls.

CONCLUSIONS

Sleep disturbance exists in children with asthma and manifests differently in males and females. Further investigation into the clinical implication of increased sleep latency and reduced sleep duration upon daytime functioning and lifestyle behaviours in children and adolescents with asthma is warranted.

Nocturnal asthma

PURPOSE OF REVIEW

The aim is to review pathophysiological mechanisms and treatment of nocturnal asthma.

RECENT FINDINGS

Physiologic changes accompanying sleep, as well as the nocturnal phase of circadian rhythms, may have an adverse effect on asthma control. Chronotherapeutic principles, which consider circadian variation in relevant biologic rhythms, may improve asthma outcomes. Administration of long-acting bronchodilators and inhaled corticosteroids which achieve maximum efficacy at night may improve nocturnal asthma. Comorbid conditions that may contribute to nocturnal asthma should be considered. The prevalence of obstructive sleep apnea is greater in a cohort of patients with severe asthma than in moderate asthma and in BMI and age matched nonasthmatic controls, suggesting a link between these diseases. A large trial concluded that esomeprazole did not improve asthma control even with comorbid acid reflux, questioning the importance of acid reflux in asthma. The role of polymorphisms of the β2-adrenergic receptor and their relationship with nocturnal asthma remain controversial.

SUMMARY

Sleep is a time of vulnerability to respiratory compromise, especially in asthma patients experiencing nocturnal exacerbations. This asthma phenotype is associated with poorer control, reduced sleep quality, daytime somnolence and increased morbidity and mortality. Nocturnal asthma is a common but under-recognized problem.

Brain natriuretic peptide and acute hypobaric hypoxia in humans

In animal models, the secretion of the cardiac hormone, brain natriuretic peptide (BNP), and its closely related peptide, atrial natriuretic peptide (ANP), are stimulated by acute hypoxia. There is extensive human evidence for a rise in ANP under acute hypoxic conditions but very little evidence regarding the BNP response to acute hypoxia in humans. We therefore subjected seven healthy subjects to an acute hypobaric hypoxic stimulus to examine if BNP secretion increases rapidly. Significant hypoxaemia (mean nadir oxygen saturation 62.3%) was induced but no significant rise in BNP occurred. This suggests that either such acute hypoxaemia is well tolerated by the healthy human heart or it is not a stimulus for BNP secretion.