***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Chronic obstructive pulmonary disease ( COPD ) remains a significant public health burden . Non-invasive ventilation ( NIV ) is a method of supported breathing used as st and ard care for acutely unwell patients in hospital with COPD , but there is uncertainty around the potential benefits of using NIV in the treatment of stable patients in a non-hospital setting . This is a protocol for systematic review s of the clinical and cost-effectiveness of NIV in this context , being undertaken in support of a model based economic evaluation . Methods / Design St and ard systematic review methods aim ed at minimising bias will be employed for study identification , selection and data extraction for both the clinical and economic systematic review s. Bibliographic data bases ( for example MEDLINE , EMBASE ) and ongoing trials registers will be search ed from 1980 onwards . The search strategy will combine terms for the population with those for the intervention . Studies will be selected for review if the population includes adult patients with COPD and hypercapnic respiratory failure , however defined . Systematic review s , r and omised controlled trials and observational studies ( with n > 1 ) will be included , and quality assessment will be tailored to the different study design s. The primary outcome measures of interest are survival , quality of life , and healthcare utilisations ( hospitalisation and Accident and Emergency attendances ) . Meta-analyses will be undertaken where clinical and method ological homogeneity exists , supported by predefined subgroup analyses where appropriate . A systematic review of the evidence on the cost-effectiveness of non-hospital NIV will be completed , and a model-based cost-utility analysis undertaken to determine the cost-effectiveness of non-hospital-based NIV compared with st and ard care . Discussion These review s will attempt to clarify the clinical effectiveness of non-hospital NIV in COPD patients as well as the cost-effectiveness . The findings may indicate whether NIV in a non-hospital setting should be considered more routinely in this patient group , and what the likely cost implication s will be . PROSPERO registration 2012:CRD42012003286 Background Exacerbations of chronic obstructive pulmonary disease ( COPD ) are sporadic , acute worsening of symptoms . Identifying predictors of exacerbation frequency may facilitate medical interventions that reduce exacerbation frequency and severity . The objective of this study was to determine predictors of exacerbation frequency and mortality . Methods A total of 227 COPD patients were enrolled in a prospect i ve clinical study between January 2000 and December 2011 . Reported exacerbations were recorded for the year preceding enrollment and annually thereafter , and patients were grouped by median annual exacerbation frequency into those experiencing infrequent exacerbations ( less than one exacerbation annually ) and frequent exacerbations ( one or more exacerbation annually ) . Patients experiencing frequent exacerbations were further divided into those experiencing moderately frequent exacerbations ( fewer than two exacerbations per year ) and severely frequent exacerbations ( two or more exacerbations per year ) . The rate of clinical relapse and survival was recorded over a 10-year period . The mean of follow-up time was 5.15 years per patient . Results For patients experiencing infrequent , moderately frequent , and severely frequent exacerbations , median exacerbations in the year preceding enrollment were 0.0 , 0.5 , 1.0 , respectively , and more frequent exacerbations correlated with lower baseline forced expiratory volume in one second ( FEV1 ) ( 0.81 L , 0.75 L , and 0.66 L , respectively ) , higher comorbidity ( 70.7 % , 75.0 % , and 89.4 % , respectively ) , and greater NPPV use during hospitalization ( 16.4 % , 35.9 % and 51.1 % , respectively ) . FEV1 declined and mortality increased with increasing exacerbation frequency . Conclusions  Exacerbation frequency  can be used to generate discreet patient sub population s , supporting the hypothesis that multiple COPD phenotypes exist and can be used in patient risk stratification Background : Long-term non-invasive positive pressure ventilation ( NIPPV ) might improve the outcomes of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease ( COPD ) with chronic respiratory failure . A study was undertaken to investigate whether nocturnal NIPPV in addition to pulmonary rehabilitation improves health-related quality of life , functional status and gas exchange compared with pulmonary rehabilitation alone in patients with COPD with chronic hypercapnic respiratory failure . Methods : 72 patients with COPD were r and omly assigned to nocturnal NIPPV in addition to rehabilitation ( n = 37 ) or rehabilitation alone ( n = 35 ) . Outcome measures were assessed before and after the 3-month intervention period . Results : The Chronic Respiratory Question naire total score improved 15.1 points with NIPPV + rehabilitation compared with 8.7 points with rehabilitation alone . The difference of 7.5 points was not significant ( p = 0.08 ) . However , compared with rehabilitation alone , the difference in the fatigue domain was greater with NIPPV + rehabilitation ( mean difference 3.3 points , p<0.01 ) , as was the improvement in the Maugeri Respiratory Failure question naire total score ( mean difference −10 % , p<0.03 ) and its cognition domain ( mean difference −22 % , p<0.01 ) . Furthermore , the addition of NIPPV improved daytime arterial carbon dioxide pressure ( mean difference −0.3 kPa ; p<0.01 ) and daily step count ( mean difference 1269 steps/day , p<0.01 ) . This was accompanied by an increased daytime minute ventilation ( mean difference 1.4 l ; p<0.001 ) . Conclusion : Non-invasive ventilation augments the benefits of pulmonary rehabilitation in patients with COPD with chronic hypercapnic respiratory failure as it improves several measures of health-related quality of life , functional status and gas exchange . Trial registration number : NCT00135538 Introduction Noninvasive ventilation ( NIV ) is a well-established treatment for acute-on- chronic respiratory failure in hypercapnic COPD patients . Less is known about the effects of a long-term treatment with NIV in hypercapnic COPD patients and about the factors that may predict response in terms of improved oxygenation and lowered CO2 retention . Methods In this study , we r and omized 15 patients to a routine pharmacological treatment ( n = 5 , age 66 [ st and ard deviation ± 6 ] years , FEV1 30.5 [ ±5.1 ] % pred , PaO2 65 [ ±6 ] mmHg , PaCO2 52.4 [ ±6.0 ] mmHg ) or to a routine treatment and NIV ( using the Synchrony BiPAP device [ Respironics , Inc , Murrsville , PA ] ) ( n = 10 , age 65 [ ±7 ] years , FEV1 29.5 [ ±9.0 ] % pred , PaO2 59 [ ±13 ] mmHg , PaCO2 55.4 [ ±7.7 ] mmHg ) for 6 months . We looked at arterial blood gasses , lung function parameters and performed a low-dose computed tomography of the thorax , which was later used for segmentation ( providing lobe and airway volumes , iVlobe and iVaw ) and post-processing with computer methods ( providing airway resistance , iRaw ) giving overall a functional image of the separate airways and lobes . Results In both groups there was a nonsignificant change in FEV1  ( NIV group 29.5 [ 9.0 ] to 38.5 [ 14.6 ] % pred , control group 30.5 [ 5.1 ] to 36.8 [ 8.7 ] mmHg ) . PaCO2 dropped significantly only in the NIV group ( NIV : 55.4 [ 7.7 ] → 44.5 [ 4.70 ] , P = 0.0076 ; control : 52.4 [ 6.0 ] → 47.6 [ 8.2 ] , NS ) . Patients actively treated with NIV developed a more inhomogeneous redistribution of mass flow than control patients . Subsequent analysis indicated that in NIV-treated patients that improve their blood gases , mass flow was also redistributed towards areas with higher vessel density and less emphysema , indicating that flow was redistributed towards areas with better perfusion . There was a highly significant correlation between the % increase in mass flow towards lobes with a blood vessel density of > 9 % and the increase in PaO2 . Improved ventilation – perfusion match and recruitment of previously occluded small airways can explain the improvement in blood gases . Conclusion We can conclude that in hypercapnic COPD patients treated with long-term NIV over 6 months , a mass flow redistribution occurs , providing a better ventilation – perfusion match and hence better blood gases and lung function . Control patients improve homogeneously in iVaw and iRaw , without improvement in gas exchange since there is no improved ventilation/perfusion ratio or increased alveolar ventilation . These differences in response can be detected through functional imaging , which gives a more detailed report on regional lung volumes and resistances than classical lung function tests do . Possibly only patients with localized small airway disease are good c and i date s for long-term NIV treatment . To confirm this and to see if better arterial blood gases also lead to better health related quality of life and longer survival , we have to study a larger population Background : Sleep hypoventilation has been proposed as a cause of progressive hypercapnic respiratory failure and death in patients with severe chronic obstructive pulmonary disease ( COPD ) . A study was undertaken to determine the effects of nocturnal non-invasive bi-level pressure support ventilation ( NIV ) on survival , lung function and quality of life in patients with severe hypercapnic COPD . Method : A multicentre , open-label , r and omised controlled trial of NIV plus long-term oxygen therapy ( LTOT ) versus LTOT alone was performed in four Australian University Hospital sleep/respiratory medicine departments in patients with severe stable smoking-related COPD ( forced expiratory volume in 1 s ( FEV1.0 ) < 1.5 litres or < 50 % predicted and ratio of FEV1.0 to forced vital capacity ( FVC ) < 60 % with awake arterial carbon dioxide tension ( Paco2 ) > 46 mm Hg and on LTOT for at least 3 months ) and age < 80 years . Patients with sleep apnoea ( apnoea-hypopnoea index > 20/h ) or morbid obesity ( body mass index > 40 ) were excluded . Outcome measures were survival , spirometry , arterial blood gases , polysomnography , general and disease-specific quality of life and mood . Results : 144 patients were r and omised ( 72 to NIV + LTOT and 72 to LTOT alone ) .  NIV  improved sleep quality and sleep-related hypercapnia acutely , and patients complied well with therapy ( mean ( SD ) nightly use 4.5 ( 3.2 ) h ) . Compared with LTOT alone , NIV ( mean follow-up 2.21 years , range 0.01–5.59 ) showed an improvement in survival with the adjusted but not the unadjusted Cox model ( adjusted hazard ratio ( HR ) 0.63 , 95 % CI 0.40 to 0.99 , p = 0.045 ; unadjusted HR 0.82 , 95 % CI 0.53 to 1.25 , p = NS ) . FEV1.0 and Paco2 measured at 6 and 12 months were not different between groups . Patients assigned to NIV + LTOT had reduced general and mental health and vigour . Conclusions : Nocturnal NIV in stable oxygen-dependent patients with hypercapnic COPD may improve survival , but this appears to be at the cost of worsening quality of life . Trial registration number : The role of non-invasive nocturnal domiciliary ventilation ( NNV ) in chronic obstructive pulmonary disease ( COPD ) patients with chronic hypercapnia is still discussed . The aims of this study were to evaluate the long-term survival , the clinical effectiveness and side-effects of NNV in these patients . Forty-nine stable hypercapnic COPD patients on long-term oxygen therapy ( LTOT ) were assigned to two groups : in Group 1 , 28 patients performed  NNV by pressure support modality in addition to LTOT ; in Group 2 , 21 patients continued their usual LTOT regimen . Treatment was assigned according to the compliance to NNV , after an in hospital period . Mortality rate , hospital stay ( HS ) and ICU admissions ( IA ) were recorded in the two groups . HS and IA were compared to those recorded in a similar period of follow-back . Lung and respiratory muscle function , dyspnoea , and exercise capacity ( by 6-min walk test ) were evaluated baseline and every 3 - 6 months up to 3 yr . Mean follow-up time was 35 + /- 7 months . Mortality rate was not different between the two groups : 16 , 33 , 46 % and 13 , 28 , 50 % at 1 , 2 and 3 yr in Groups 1 and 2 respectively . Lung and respiratory muscle function did not significantly change over time . A significant increase in 6-min walk test ( from 245 + /- 78 to 250 + /- 88 , 291 + /- 75 , 284 + /- 89 m after 1 , 2 and 3 yr respectively , P < 0.01 ) was observed only in 
    Output:
    
CONCLUSION The effectiveness of domiciliary NIV remains uncertain ; however , some patients may benefit .