***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 : The objective of the present analysis is to describe the outcomes of high-intensity non-invasive positive pressure ventilation ( NPPV ) aim ed at maximally decreasing PaCO2 as an alternative to conventional NPPV with lower ventilator setting s in stable hypercapnic COPD patients . Methods : Physiological parameters , exacerbation rates and long-term survival were assessed in 73 COPD patients ( mean FEV1 30±12 % predicted ) who were established on high-intensity NPPV due to chronic hypercapnic respiratory failure between March 1997 and May 2006 . Results : Controlled NPPV with breathing frequencies of 21±3 breath/min and mean inspiratory/expiratory positive airway pressures of 28±5/5±1 cmH2O led to significant improvements in blood gases , lung function and hematocrit after two months . Only sixteen patients ( 22 % ) required hospitalisation due to exacerbation during the first year , with anaemia increasing the risk for exacerbation . Two- and five-year survival rates of all patients were 82 % and 58 % , respectively . The five year survival rate was 32 % and 83 % in patients with low ( ≤39 % ) and high ( ≥55 % ) hematocrit , respectively . Conclusion : High-intensity NPPV  improves blood gases , lung function and hematocrit , and is also associated with low exacerbation rates and a favourable long-term outcome . The current report strongly emphasises the need for r and omised controlled trials evaluating the role of high-intensity NPPV in stable hypercapnic COPD patients To more systematic ally evaluate the effect of respiratory muscle rest on indices of ventilatory function , nine out patients with stable , severe COPD were treated with nasal pressure-support ventilation delivered via a nasal ventilatory support system ( BiPAP , Respironics , Inc ) for 2 h a day for 5 consecutive days . An additional eight control patients were treated with sham-BiPAP .  Maximum inspiratory pressure ( MIP ) , maximum expiratory pressure ( MEP ) , maximum voluntary ventilation ( MVV ) , arterial blood gas values , Borg dyspnea score , dyspnea-associated functional impairment scales , and distance walked in 6 min were measured in subjects prior to and following the week-long trial . Nasal BiPAP produced a 66.3 + /- 6 percent reduction in peak integrated diaphragmatic electromyographic ( EMG ) activity . There were no statistically significant changes in MIP , MEP , MVV , arterial pH , PaCO2 , or PaO2 or in objective measures of functional impairment from dyspnea in either group after ventilator or sham treatment . However , nasal BiPAP reduced the Borg category score during resting , spontaneous breathing from 2.0 + /- 0.4 to 0.7 + /- 0.3 ( p < 0.01 ) after 5 days of treatment . In contrast , sham BiPAP-treated patients had no change in their dyspnea score , which was 1.8 + /- 0.4 and 1.3 + /- 0.4 before and after sham treatment , respectively . Nasal BiPAP also increased distance walked in 6 min from 780 + /- 155 to 888 + /- 151 ft ( p < 0.01 ) ( 23,400 + /- 4,650 to 26,640 + /- 4,530 cm ) ( p < 0.01 ) , whereas sham-BiPAP had no effect ( 768 + /- 96 and 762 + /- 106 ft [ 23,040 + /- 2,880 and 22,860 + /- 3,180 cm ] ) before and after sham treatment , respectively ) . In conclusion , these results indicate that nasal pressure-support ventilation , delivered via nasal BiPAP , improves exercise capacity and reduces dyspnea over the short term in selected out patients with stable severe COPD . Whether such short-term improvement can be sustained merits further study BACKGROUND Pulmonary function may improve after surgical resection of the most severely affected lung tissue ( lung-reduction surgery ) in patients with diffuse emphysema . The basic mechanisms responsible for the improvement , however , are not known . METHODS We studied 20 patients with diffuse emphysema before and at least three months after either a unilateral or a bilateral lung-reduction procedure .  Clinical benefit was assessed by measurement of the six-minute walking distance and the transitional-dyspnea index , which is a subjective rating of the change from base line in functional impairment and the threshold for effort- and task- dependent dyspnea . Pressure-volume relations in the lungs were measured with static expiratory esophageal-balloon techniques , and right ventricular systolic function was assessed by echocardiography . RESULTS The patients had significant improvement in the transitional-dyspnea index after surgery ( P<0.001 ) . The mean ( + /-SD ) coefficient of retraction , an indicator of elastic recoil of the lung , improved ( from 1.3+/-0.6 cm of water per liter before surgery to 1.8+/-0.8 after , P<0.001 ) . Sixteen patients with increased elastic recoil had a greater increase in the distance walked in six minutes than the other four patients , in whom recoil did not increase ( P=0.02 ) . The improved lung recoil led to disproportionate decreases in residual volume as compared with total lung capacity ( 16 percent vs. 6 percent ) , but the decreases in both values were significant ( P<0.001 ) . Forced expiratory volume in one second increased ( from 0.87+/-0.36 to 1.11+/-0.45 liters , P<0.001 ) . End-expiratory esophageal pressure also decreased ( P=0.002 ) . These improvements in lung mechanics led to a decrease in arterial partial pressure of carbon dioxide form 42+/-6 to 38+/-5 mm Hg ( P=0.006 ) . Furthermore , the fractional change in right ventricular area , an indicator of systolic function , increased from 0.33+/-0.11 to 0.38+/-0.010 ( P=0.02 ) . CONCLUSIONS Lung-reduction surgery can produce increases in the elastic recoil of the lung in patients with diffuse emphysema , leading to short-term improvement in dyspnea and exercise tolerance 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 patients undergoing NNV . In comparison to the follow back HS significantly decreased in both groups ( from 37 + /- 29 to 15 + /- 12 and from 32 + /- 18 to 17 + /- 11 days/pt/yr in Groups 1 and 2 respectively , P < 0.001 ) whereas IA significantly decreased only in patients performing also NNV ( from 1.0 + /- 0.7 to 0.2 + /- 0.3/pt/yr , P < 0.0001 ) . Addition of NNV by pressure support modality to LTOT does not improve long term survival but significantly reduces ICU admissions and improves exercise capacity in severe COPD with hypercapnia STUDY OBJECTIVES To determine the 1-year efficacy of noninvasive positive pressure ventilation ( NPPV ) added to long-term oxygen therapy ( LTOT ) in patients with stable severe COPD . PATIENT SELECTION AND METHODS : We prospect ively r and omized 52 patients with severe COPD ( FEV(1 ) < 45 % ) to either NPPV plus " st and ard care " ( 96 % patients with LTOT ) or to st and ard care alone ( 93 % patients with LTOT ) . The outcomes measured included the following : rate of acute COPD exacerbations ; hospital admissions ; intubations ; and mortality at 3 months , 6 months , and 12 months . The patients were also evaluated at 3 months and 6 months for dyspnea using the Medical Research Council and Borg scales , gas exchange , hematocrit , pulmonary function , cardiac function with echocardiogram , and neuropsychological performance . RESULTS One-year survival was similar in both groups ( 78 % ) . The number of acute exacerbations was similar at all time points in patients receiving NPPV , compared with control subjects . The number of hospital admissions was decreased at 3 months in the NPPV group ( 5 % vs 15 % of patients , p < 0.05 ) , but this difference was not seen at 6 months ( 18 % vs 19 % , respectively ) . The only beneficial differences were observed in the Borg dyspnea rating , which dropped from 6 to 5 ( p < 0.039 ) , and in one of the neuropsychological tests ( psychomotor coordination ) for the NPPV group at 6 months . CONCLUSIONS Our study indicates that over 1 year , NPPV does not affect the natural course of the disease and is of marginal benefit in out patients with severe COPD who are in stable condition Chronic obstructive pulmonary disease ( COPD ) patients with chronic ventilatory failure ( CVF ) are more likely to develop exacerbations , which are an important determinant of health-related quality of life ( HRQL ) . Long-term noninvasive positive-pressure ventilation ( NPPV ) has been proposed in addition to long-term oxygen therapy ( LTOT ) to treat CVF but little information is available on its effects on HRQL and re source consumption . Therefore 
    Output:
    
Nocturnal-NIPPV at home for at least three months in hypercapnic patients with stable COPD had no consistent clinical ly or statistically significant effect on gas exchange , exercise tolerance , HRQoL , lung function , respiratory muscle strength or sleep efficiency .
Meta- analysis of the two new long-term studies did not show significant improvements in blood gases , HRQoL or lung function after 12 months of NIPPV .
However , the small sample sizes of these studies preclude a definite conclusion regarding the effects of NIPPV in COPD