Validation of a small cough detector.

Research question: The assessment of cough frequency in clinical practice relies predominantly on the patient's history. Currently, objective evaluation of cough is feasible with bulky equipment during a brief time (i.e. hours up to 1 day). Thus, monitoring of cough has been rarely performed outside clinical studies. We developed a small wearable cough detector (SIVA-P3) that uses deep neural networks for the automatic counting of coughs. This study examined the performance of the SIVA-P3 in an outpatient setting. Methods: We recorded cough epochs with SIVA-P3 over eight consecutive days in patients suffering from chronic cough. During the first 24 h, the detector was validated against cough events counted by trained human listeners. The wearing comfort and the device usage were assessed using a questionnaire. Results: In total, 27 participants (mean±sd age 50±14 years) with either chronic unexplained cough (n=12), COPD (n=4), asthma (n=5) or interstitial lung disease (n=6) were studied. During the daytime, the sensitivity of SIVA-P3 cough detection was 88.5±2.49% and the specificity was 99.97±0.01%. During the night-time, the sensitivity was 84.15±5.04% and the specificity was 99.97±0.02%. The wearing comfort and usage of the device was rated as very high by most participants. Conclusion: SIVA-P3 enables automatic continuous cough monitoring in an outpatient setting for objective assessment of cough over days and weeks. It shows comparable sensitivity or higher sensitivity than other devices with fully automatic cough counting. Thanks to its wearing comfort and the high performance for cough detection, it has the potential for being used in routine clinical practice.

Autoadjusted versus fixed CPAP for obstructive sleep apnoea: a multicentre, randomised equivalence trial.

BACKGROUND: The obstructive sleep apnoea syndrome (OSAS) is conventionally treated by continuous positive airway pressure set at a fixed level (fCPAP). Automatic mask pressure adjustment (autoCPAP) is increasingly used during home therapy. We investigated whether autoCPAP is equivalent to fCPAP in improving sleepiness in patients with OSAS in the long-term. METHODS: In this multicentre equivalence trial, 208 patients with OSAS, with median Epworth sleepiness score (ESS) 13, apnoea/hypopnoea index 48.4/hour, were randomised to treatment with autoCPAP (5-15 mbar) or fCPAP (pressure set at the 90th percentile applied by autoCPAP during 2-4 weeks adaptation). Coprimary outcomes were changes in subjective and objective sleepiness from baseline to 2 years after treatment. Equivalence ranges were ±2 points in ESS and ±3 min sleep resistance time evaluated by recording responses to light signals. RESULTS: At 2 years, in the intention to treat analysis, the reduction in sleepiness versus pretreatment baseline was similar in patients using autoCPAP (n=113, mean ESS-change -6.3, 95% CI -7.1 to -5.5; sleep resistance time +8.3 min, +6.9 to +9.7) and fCPAP (n=95, mean ESS-change -6.2, 95% CI -7.0 to -5.3; sleep resistance time +6.3 min, +4.7 to +7.8). The 95% CI of difference in ESS-reduction between autoCPAP and fCPAP was -0.9 to +1.4 and the 95% CI of difference in increase in sleep resistance time was -2.6 to +1.0 min. Blood pressure reduction and OSAS-related costs were similar between groups. CONCLUSIONS: AutoCPAP and fCPAP are equivalent within prespecified ranges in improving subjective and objective sleepiness in patients with OSAS over the course of 2 years. Costs of these treatments are similar. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov NCT00280800.

Effect of rituximab on pulmonary function in patients with rheumatoid arthritis.

BACKGROUND: Rituximab (RTX), a B-cell depleting monoclonal antibody is increasingly used in several antibody-mediated diseases. It has been reported to cause pulmonary toxicity, though mainly during polychemotherapy of malignant lymphoma. Prospective data on RTX-induced pulmonary complications in patients with rheumatoid arthritis (RA) are lacking. METHODS AND METHODS: Serial spirometries and measurements of diffusion capacity of the lung for carbon monoxide (DLCO) in patients with RA before and 2, 4, 8, and 26 weeks after treatment with RTX were performed. A reduction from baseline of forced vital capacity (FVC) of ≥10%, or ≥15% of DLCO was defined as indicative for pulmonary toxicity. RESULTS: Thirty-three patients (mean (SD) age 59 (12) years, 27% males) were included. Mean (SD) FVC predicted and DLCO predicted at baseline were 108% (18%) and 88% (18%), respectively. In contrast to FVC, DLCO showed a progressive decline during follow-up with a maximum reduction of 6.1% (95%CI 2.5%, 9.7%; p = 0.001) at 26 weeks compared with baseline. After 26 weeks, 22% of the patients had a ≥15% DLCO decline. None of the patients reported increased dyspnea during follow-up. Risk factors for pulmonary function changes after treatment with RTX were cigarette smoking, repeated administration of the drug, and co-medication with Prednisone. CONCLUSION: Although no cases of symptomatic lung injury were observed, the progressive DLCO decline seems to indicate the presence of subclinical RTX-induced pulmonary toxicity.

[E-Cigarettes ­ Friend or Foe?]. / E-Zigaretten - Fluch oder Segen?

Not nicotine, but an abundant amount of toxic chemicals produced by the combustion of tobacco are the cause of well-known health problems. E-cigarette vapor contains no or only minimal quantities of potentially harmful substances. Hence it can be assumed that vaping in adults is much less harmful than smoking of cigarettes. Furthermore, no data exist that e-cigarettes will encourage youngsters to become cigarette smokers. E-cigarette vaping has the potential to reduce the daily number of cigarettes smoked or facilitates cessation of smoking in heavily nicotine-dependent smokers, who keep on smoking despite a structured smoking cessation program. Health professionals should be aware of this type of nicotine substitution, since the controversial discussion is often emotional and not evidence-based.

Causal and synthetic associations of variants in the SERPINA gene cluster with alpha1-antitrypsin serum levels.

Several infrequent genetic polymorphisms in the SERPINA1 gene are known to substantially reduce concentration of alpha1-antitrypsin (AAT) in the blood. Since low AAT serum levels fail to protect pulmonary tissue from enzymatic degradation, these polymorphisms also increase the risk for early onset chronic obstructive pulmonary disease (COPD). The role of more common SERPINA1 single nucleotide polymorphisms (SNPs) in respiratory health remains poorly understood. We present here an agnostic investigation of genetic determinants of circulating AAT levels in a general population sample by performing a genome-wide association study (GWAS) in 1392 individuals of the SAPALDIA cohort. Five common SNPs, defined by showing minor allele frequencies (MAFs) >5%, reached genome-wide significance, all located in the SERPINA gene cluster at 14q32.13. The top-ranking genotyped SNP rs4905179 was associated with an estimated effect of ß = -0.068 g/L per minor allele (P = 1.20*10(-12)). But denser SERPINA1 locus genotyping in 5569 participants with subsequent stepwise conditional analysis, as well as exon-sequencing in a subsample (N = 410), suggested that AAT serum level is causally determined at this locus by rare (MAF<1%) and low-frequent (MAF 1-5%) variants only, in particular by the well-documented protein inhibitor S and Z (PI S, PI Z) variants. Replication of the association of rs4905179 with AAT serum levels in the Copenhagen City Heart Study (N = 8273) was successful (P<0.0001), as was the replication of its synthetic nature (the effect disappeared after adjusting for PI S and Z, P = 0.57). Extending the analysis to lung function revealed a more complex situation. Only in individuals with severely compromised pulmonary health (N = 397), associations of common SNPs at this locus with lung function were driven by rarer PI S or Z variants. Overall, our meta-analysis of lung function in ever-smokers does not support a functional role of common SNPs in the SERPINA gene cluster in the general population.

Determinants of endothelial function in patients with COPD.

Chronic obstructive pulmonary disease (COPD) is associated with increased cardiovascular mortality. Endothelial dysfunction may underpin this association. This cross-sectional study aimed to determine the impact of airflow obstruction, systemic inflammation, oxidative stress, sympathetic activation, hypoxaemia and physical activity on endothelial function in COPD. In stable COPD patients, assessments of endothelial function by flow-mediated dilatation (FMD), cardiovascular risk (Pocock score), airflow obstruction (forced expiratory volume in 1 s (FEV1)), systemic inflammation (high-sensitivity C-reactive protein and interleukin-6), oxidative stress (malondialdehyde), sympathetic activation (baroreflex sensitivity), hypoxaemia (arterial oxygen tension), hypercapnia (arterial carbon dioxide tension (PaCO2)), physical activity (steps per day) and exercise capacity (6-min walking distance) were performed. Associations between FMD and potential determinants were assessed in univariate and multivariate analyses. 106 patients (Global Initiative for Chronic Obstructive Lung Disease stage I/II 35%, stage III 25% and stage IV 40%) were included. In multivariate analysis FEV1 was positively associated with FMD, independent of other significant FMD determinants from univariate analysis (sex, smoking, combined inhaled long-acting ß-adrenergic and steroid medication, heart rate, baroreflex sensitivity and PaCO2) and adjusted for potential confounders (cardiovascular risk and age). In addition, the FMD and FEV1 association was modified by physical activity. The findings of this study demonstrate that the severity of airflow obstruction is a significant determinant of endothelial function in patients with COPD. A high level of physical activity seems to have a favourable effect on this association.

Predicting daily physical activity in patients with chronic obstructive pulmonary disease.

BACKGROUND: Objectively measuring daily physical activity (PA) using an accelerometer is a relatively expensive and time-consuming undertaking. In routine clinical practice it would be useful to estimate PA in patients with chronic obstructive pulmonary disease (COPD) with more simple methods. OBJECTIVES: To evaluate whether PA can be estimated by simple tests commonly used in clinical practice in patients with COPD. METHODS: The average number of steps per day was measured for 7 days with a SenseWear Pro™ accelerometer and used as gold standard for PA. A physical activity level (PAL) of <1.4 was considered very inactive. Univariate and multivariate analyses were used to examine the relationship between the 6-minute walking distance (6MWD), the number of stands in the Sit-to-Stand Test (STST), hand-grip strength and the total energy expenditure as assessed by the Zutphen Physical Activity Questionnaire (TEE(ZPAQ)). ROC curve analysis was used to identify patients with an extremely inactive lifestyle (PAL<1.4). RESULTS: In 70 patients with COPD (21 females) with a mean [SD] FEV(1) of 43.0 [22.0] %predicted, PA was found to be significantly and independently associated with the 6MWD (r = 0.69, 95% CI 0.54 to 0.80, p<0.001), STST (r = 0.51, 95% CI 0.31 to 0.66, p = 0.001) and TEEZPAQ (r = 0.50, 95% CI 0.30 to 0.66, p<0.001) but not with hand-grip strength. However, ROC curve analysis demonstrated that these tests cannot be used to reliably identify patients with an extremely inactive lifestyle. CONCLUSIONS: In patients with COPD simple tests such as the 6-Minute Walk Test, the Sit-to-Stand Test and the Zutphen Physical Activity Questionnaire cannot be used to reliably predict physical inactivity.

SERPINA1 PiZ and PiS heterozygotes and lung function decline in the SAPALDIA cohort.

BACKGROUND: Severe alpha1-antitrypsin (AAT) deficiency is a strong risk factor for COPD. But the impact of gene variants resulting in mild or intermediate AAT deficiency on the longitudinal course of respiratory health remains controversial. There is indication from experimental studies that pro-inflammatory agents like cigarette smoke can interact with these variants and thus increase the risk of adverse respiratory health effects. Therefore, we tested the effect of the presence of a protease inhibitor (Pi) S or Z allele (PiMS and PiMZ) on the change in lung function in different inflammation-exposed subgroups of a large, population-based cohort study. METHODOLOGY AND PRINCIPAL FINDINGS: The SAPALDIA population includes over 4600 subjects from whom SERPINA1 genotypes for S and Z alleles, spirometry and respiratory symptoms at baseline and after 11 years follow-up, as well as proxies for inflammatory conditions, such as detailed smoking history, obesity and high sensitivity C-reactive protein (hs-CRP), were available. All analyses were performed by applying multivariate regression models. There was no overall unfavourable effect of PiMS or PiMZ genotype on lung function change. We found indication that PiZ heterozygosity interacted with inflammatory stimuli leading to an accelerated decline in measures in use as indices for assessing mild airway obstruction. Obese individuals with genotype PiMM had an average annual decline in the forced mid expiratory flow (ΔFEF25-75%) of 58.4 ml whereas in obese individuals with PiMZ it amounted to 92.2 ml (p = 0.03). Corresponding numbers for persistent smokers differed even more strongly (66.8 ml (PiMM) vs. 108.2 ml (PiMZ), p = 0.005). Equivalent, but less strong associations were observed for the change in the FEV1/FVC ratio. CONCLUSIONS: We suggest that, in addition to the well established impact of the rare PiZZ genotype, one Z allele may be sufficient to accelerate lung function decline in population subgroups characterized by elevated levels of low grade inflammation.

Different genes interact with particulate matter and tobacco smoke exposure in affecting lung function decline in the general population.

BACKGROUND: Oxidative stress related genes modify the effects of ambient air pollution or tobacco smoking on lung function decline. The impact of interactions might be substantial, but previous studies mostly focused on main effects of single genes. OBJECTIVES: We studied the interaction of both exposures with a broad set of oxidative-stress related candidate genes and pathways on lung function decline and contrasted interactions between exposures. METHODS: For 12679 single nucleotide polymorphisms (SNPs), change in forced expiratory volume in one second (FEV(1)), FEV(1) over forced vital capacity (FEV(1)/FVC), and mean forced expiratory flow between 25 and 75% of the FVC (FEF(25-75)) was regressed on interval exposure to particulate matter <10 µm in diameter (PM10) or packyears smoked (a), additive SNP effects (b), and interaction terms between (a) and (b) in 669 adults with GWAS data. Interaction p-values for 152 genes and 14 pathways were calculated by the adaptive rank truncation product (ARTP) method, and compared between exposures. Interaction effect sizes were contrasted for the strongest SNPs of nominally significant genes (p(interaction)<0.05). Replication was attempted for SNPs with MAF>10% in 3320 SAPALDIA participants without GWAS. RESULTS: On the SNP-level, rs2035268 in gene SNCA accelerated FEV(1)/FVC decline by 3.8% (p(interaction) = 2.5×10(-6)), and rs12190800 in PARK2 attenuated FEV1 decline by 95.1 ml p(interaction) = 9.7×10(-8)) over 11 years, while interacting with PM10. Genes and pathways nominally interacting with PM10 and packyears exposure differed substantially. Gene CRISP2 presented a significant interaction with PM10 (p(interaction) = 3.0×10(-4)) on FEV(1)/FVC decline. Pathway interactions were weak. Replications for the strongest SNPs in PARK2 and CRISP2 were not successful. CONCLUSIONS: Consistent with a stratified response to increasing oxidative stress, different genes and pathways potentially mediate PM10 and tobacco smoke effects on lung function decline. Ignoring environmental exposures would miss these patterns, but achieving sufficient sample size and comparability across study samples is challenging.

Low-dose CT of the lung: potential value of iterative reconstructions.

OBJECTIVES: To prospectively assess the impact of sinogram-affirmed iterative reconstruction (SAFIRE) on image quality of nonenhanced low-dose lung CT as compared to filtered back projection (FBP). METHODS: Nonenhanced low-dose chest CT (tube current-time product: 30 mAs) was performed on 30 patients at 100 kVp and on 30 patients at 80 kVp. Images were reconstructed with FBP and SAFIRE. Two blinded, independent readers measured image noise; two readers assessed image quality of normal anatomic lung structures on a five-point scale. Radiation dose parameters were recorded. RESULTS: Image noise in datasets reconstructed with FBP (57.4 ± 15.9) was significantly higher than with SAFIRE (31.7 ± 9.8, P < 0.001). Image quality was significantly superior with SAFIRE than with FBP (P < 0.01), without significant difference between FBP at 100 kVp and SAFIRE at 80 kVp (P = 0.68). Diagnostic image quality was present with FBP in 96% of images at 100 kVp and 88% at 80 kVp, and with SAFIRE in 100% at 100 kVp and 98% at 80 kVp. There were significantly more datasets with diagnostic image quality with SAFIRE than with FBP (P < 0.01). Mean CTDI(vol) and effective doses were 1.5 ± 0.7 mGy·cm and 0.7 ± 0.2 mSv at 100 kVp, and 1.4 ± 2.8 mGy · cm and 0.5 ± 0.2 mSv at 80 kVp (P < 0.001, both). CONCLUSIONS: Use of SAFIRE in low-dose lung CT reduces noise, improves image quality, and renders more studies diagnostic as compared to FBP. KEY POINTS: Low-dose computed tomography is an important thoracic investigation tool. Radiation dose can be less than 1 mSv with iterative reconstructions. Iterative reconstructions render more low-dose lung CTs diagnostic compared to conventional reconstructions.

Occupational exposure to dusts, gases, and fumes and incidence of chronic obstructive pulmonary disease in the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults.

RATIONALE: There is limited evidence from population-based studies demonstrating incidence of spirometric-defined chronic obstructive pulmonary disease (COPD) in association with occupational exposures. OBJECTIVES: We evaluated the association between occupational exposures and incidence of COPD in the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA). MEASUREMENTS AND MAIN RESULTS: Prebronchodilator ratio of forced expiratory volume in 1 second over forced vital capacity (FEV(1)/FVC) was measured in 4,267 nonasthmatic SAPALDIA participants ages 18-62 at baseline in 1991 and at follow-up in 2001-2003. COPD was defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criterion (FEV(1)/FVC < 0.70) and Quanjer reference equation (FEV(1)/FVC < lower limit of normal [LLN]), and categorized by severity (≥ 80% and <80% predicted FEV(1) for stage I and stage II+, respectively). Using a job-exposure matrix, self-reported occupations at baseline were assigned exposures to biological dusts, mineral dusts, gases/fumes, and vapors, gases, dusts, or fumes (VGDF) (high, low, or unexposed as reference). Adjusted incident rate ratios (IRRs) of stage I and stage II+ COPD were estimated in mixed Poisson regression models. Statistically significant (P < 0.05) IRRs of stage II+ GOLD and LLN-COPD, indicating risks between two- and fivefold, were observed for all occupational exposures at high levels. Occupational exposure-associated risk of stage II+ COPD was observed mainly in males and ages ≥ 40 years, and remained elevated when restricted to nonsmokers. CONCLUSIONS: In a Swiss working adult population, occupational exposures to biological dusts, mineral dusts, gases/fumes, and VGDF were associated with incidence of COPD of at least moderate severity.

Serum levels and genotype distribution of α1-antitrypsin in the general population.

RATIONALE: α1-Antitrypsin (AAT) deficiency is one of the commonest rare respiratory disorders worldwide. Diagnosis, assessment of risk for developing chronic obstructive pulmonary disease (COPD), and management of replacement therapy require the availability of precise and updated ranges for protein serum levels. OBJECTIVE: This paper aims to provide ranges of serum AAT according to the main genotype classes in the general population. METHODS: The authors correlated mean AAT serum levels with the main SERPINA1 variants (M1Ala/M1Val (rs6647), M3 (rs1303), M2/M4 (rs709932), S (rs17580) and Z (rs28929474)) in 6057 individuals enrolled in the Swiss Cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) cohort. RESULTS: The following ranges (5th-95th percentile) of AAT were found in the serum (g/litre): 1.050-1.640 for PI*MM, 0.880-1.369 for PI*MS, 0.730-1.060 for PI*SS, 0.660-0.997 for PI*MZ and 0.490-0.660 for PI*SZ. There was very little overlap in AAT serum levels between genotype classes generally not believed to confer an enhanced health risk (MM and MS) and those associated with an intermediate AAT deficiency and a potentially mildly enhanced health risk (SS, MZ). CONCLUSION: This work resulted in three important findings: technically updated and narrower serum ranges for AAT according to PI genotype; a suggestion for a population-based 'protective threshold' of AAT serum level, used in decision-making for replacement therapy; and more precise ranges framing the intermediate AAT deficiency area, a potential target for future primary prevention.

Cardiac autonomic function and cardiovascular response to exercise in patients with chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with impaired exercise tolerance, but it has not been established to what extent cardiac autonomic function impacts on exercise capacity. OBJECTIVE: To evaluate whether there is an association between airflow limitation and cardiac autonomic function and whether cardiac autonomic function plays a role in exercise intolerance and daily physical activity (PA) in patients with COPD. METHODS: Univariate and multivariate analyses were performed to evaluate the association between both 6-minute walking test (6MWT) and PA (steps per day) and pulmonary function, cardiac autonomic function (HR at rest, HRR and heart rate variability, HRV) in patients with COPD. RESULTS: In 154 COPD patients (87 females, mean [SD]: age 62.5 [10.7] years, FEV(1) %predicted (43.0 [19.2]%), mean HR at rest was elevated (86.4 [16.4] beats/min) and HRV was reduced (33.69 [28.96] ms) compared to published control data. There was a significant correlation between FEV(1) and HR at rest (r = -0.32, p < 0.001), between HR at rest and 6MWD (r = -0.26, p = 0.001) and between HR at rest and PA (r = -0.29, p = 0.010). No correlation was found between HRV and 6MWD (r = 0.089, p = 0.262) and PA (r = 0.075, p = 0.322). In multivariate analysis both HR and FEV(1) were independent predictors of exercise capacity in patients with COPD. CONCLUSIONS: In patients with COPD the degree of airflow limitation is associated with HR at rest. The degree of airflow limitation and cardiac autonomic function, as quantified by HR at rest, are independently associated with exercise capacity in patients with COPD.

Randomised controlled trial for emphysema with a selective agonist of the γ-type retinoic acid receptor.

Palovarotene is an oral γ-selective retinoid agonist. In animal emphysema models, palovarotene reduced inflammation, promoted structural repair and functional improvement. REPAIR (Retinoid treatment of Emphysema in Patients on the α(1)-antitrypsin International Registry), was an investigator-initiated, double-blind, placebo-controlled randomised study to assess the safety and efficacy of 5 mg·day(-1) palovarotene given for 1 year to 262 patients with severe α(1)-antitrypsin deficiency and emphysema confirmed by computed tomography. Change in volume-adjusted 15th percentile point lung density from baseline in 1 year was the primary end-point; functional end-points were also regularly assessed. We randomly assigned 133 and 129 patients to placebo or palovarotene, respectively. Both groups were well matched for all baseline characteristics, including respiratory medications. 88% and 85% of patients completed 1 year of treatment with placebo and palovarotene, respectively. Palovarotene was generally well tolerated. In the study completers population, the placebo-corrected difference of lung density was -0.45 HU at week 28 (p=0.64) and -0.25 HU at week 52 (p=0.94). A nonsignificant treatment difference in most functional parameters of the lung in favour of the drug was observed over time suggesting potential pharmacological effects of palovarotene. Palovarotene 5 mg·day(-1) over 1 yr failed to show a significant benefit on lung density in moderate-to-severe emphysema secondary to severe α(1)-antitrypsin deficiency.

The effects of controlled breathing during pulmonary rehabilitation in patients with COPD.

BACKGROUND: Conventional pulmonary rehabilitation programs improve exercise tolerance but have no effect on pulmonary function in patients with chronic obstructive pulmonary disease (COPD). The role of controlled breathing using respiratory biofeedback during rehabilitation of patients with COPD remains unclear. OBJECTIVES: To compare the effects of a conventional 4-week pulmonary rehabilitation program with those of rehabilitation plus controlled breathing interventions. METHODS: A randomized controlled trial was performed. Pulmonary function (FEV1), exercise capacity (6-min walking distance, 6 MWD), health-related quality of life (chronic respiratory questionnaire, CRQ) and cardiac autonomic function (rMSSD) were evaluated. RESULTS: Forty COPD patients (mean±SD age 66.1±6.4, FEV1 45.9±17.4% predicted) were randomized to rehabilitation (n=20) or rehabilitation plus controlled breathing (n=20). There were no statistically significant differences between the two groups regarding the change in FEV1 (mean difference -0.8% predicted, 95% CI -4.4 to 2.9% predicted, p=0.33), 6 MWD (mean difference 12.2 m, 95% CI -37.4 to 12.2 m, p=0.16), CRQ (mean difference in total score 0.2, 95% CI -0.1 to 0.4, p=0.11) and rMSSD (mean difference 2.2 ms, 95% CI -20.8 to 25.1 ms, p=0.51). CONCLUSIONS: In patients with COPD undergoing a pulmonary rehabilitation program, controlled breathing using respiratory biofeedback has no effect on exercise capacity, pulmonary function, quality of life or cardiac autonomic function.

Effects of continuous positive airway pressure therapy withdrawal in patients with obstructive sleep apnea: a randomized controlled trial.

RATIONALE: To establish a new approach to investigate the physiological effects of obstructive sleep apnea (OSA), and to evaluate novel treatments, during a period of continuous positive airway pressure (CPAP) withdrawal. OBJECTIVES: To determine the effects of CPAP withdrawal. METHODS: Forty-one patients with OSA and receiving CPAP were randomized to either CPAP withdrawal (subtherapeutic CPAP), or continued CPAP, for 2 weeks. Polysomnography, sleepiness, psychomotor performance, endothelial function, blood pressure (BP), heart rate (HR), urinary catecholamines, blood markers of systemic inflammation, and metabolism were assessed. MEASUREMENTS AND MAIN RESULTS: CPAP withdrawal led to a recurrence of OSA within a few days and a return of subjective sleepiness, but was not associated with significant deterioration of psychomotor performance within 2 weeks. Endothelial function, assessed by flow-mediated dilatation, decreased significantly in the CPAP withdrawal group compared with therapeutic CPAP (mean difference in change, -3.2%; 95% confidence interval [CI], -4.5, -1.9%; P < 0.001). Compared with continuing CPAP, 2 weeks of CPAP withdrawal was associated with a significant increase in morning systolic BP (mean difference in change, +8.5 mm Hg; 95% CI, +1.7, +15.3 mm Hg; P = 0.016), morning diastolic BP (mean difference in change, +6.9 mm Hg; 95% CI, +1.9, +11.9 mm Hg; P = 0.008), and morning HR (mean difference in change, +6.3 bpm, 95% CI, +0.4, +12.2 bpm; P = 0.035). CPAP withdrawal was associated with an increase in urinary catecholamines but did not lead to an increase in markers of systemic inflammation, insulin resistance, or blood lipids. CONCLUSIONS: CPAP withdrawal usually leads to a rapid recurrence of OSA, a return of subjective sleepiness, and is associated with impaired endothelial function, increased urinary catecholamines, blood pressure, and heart rate. Thus the proposed study model appears to be suitable to evaluate physiological and therapeutic effects in OSA. Clinical trial registered with www.controlled-trials.com (ISRCTN93153804).