***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: We postulated that ventilatory assistance during exercise would improve cardiopulmonary function , relieve exertional symptoms , and increase exercise endurance ( T(lim ) ) in patients with chronic congestive heart failure ( CHF ) . After baseline pulmonary function tests , 12 stable patients with advanced CHF ( ejection fraction , 24 + /- 3 % [ mean + /- SEM ] ) performed constant-load exercise tests at approximately 60 % of their predicted maximal oxygen consumption ( V O(2)max ) while breathing each of control ( 1 cm H(2)O ) , continuous positive airway pressure optimized to the maximal tolerable level ( CPAP = 4.8 + /- 0.2 cm H(2)O ) or inspiratory pressure support ( PS = 4.8 + /- 0.2 cm H(2)O ) , in r and omized order . Measurements during exercise included cardioventilatory responses , esophageal pressure ( Pes ) , and Borg ratings of dyspnea and leg discomfort ( LD ) . At a st and ardized time near end-exercise , PS and CPAP reduced the work of breathing per minute by 39 + /- 8 and 25 + /- 4 % , respectively ( p < 0 . 01 ) . In response to PS : T(lim ) increased by 2.8 + /- 0.8 min or 43 + /- 14 % ( p < 0.01 ) ; slopes of LD-time , V O(2)-time , V CO(2)-time , and tidal Pes-time decreased by 24 + /- 10 , 20 + /- 11 , 28 + /- 8 , and 44 + /- 9 % , respectively ( p < 0.05 ) ; dyspnea and other cardioventilatory parameters did not change . CPAP did not significantly alter measured exercise responses . The increase in T(lim ) was explained primarily by the decrease in LD- time slopes ( r = -0.71 , p < 0.001 ) which , in turn , correlated with the reductions in V O(2)-time ( r = 0.61 , p < 0.01 ) and tidal Pes-time ( r = 0.52 , p < 0.01 ) . in conclusion , ventilatory muscle unloading with PS reduced exertional leg discomfort and increased exercise endurance in patients with stable advanced CHF Introduction Non-invasive ventilation may improve autonomic modulation and ventilatory parameters in severely disabled patients . The aim of the present study was to evaluate the physiological influence of acute treatment with different levels of continuous positive airway pressure ( CPAP ) on the autonomic balance of heart and respiratory responses in patients with stable chronic obstructive pulmonary disease ( COPD ) and chronic heart failure ( CHF ) . Material s and methods A COPD group ( n = 10 ) , CHF group ( n = 8) and healthy subjects ( n = 10 ) were evaluated . The participants were r and omized to receive three different levels of CPAP on the same day : sham ventilation ( Sham ) , 5 cmH20 ( CPAP5 ) and 10 cmH20 ( CPAP10 ) for 10 min . Respiratory rate , end tidal carbon dioxide ( ETCO2 ) , peripheral oxygen saturation ( SpO2 ) , heart rate ( HR ) , blood pressure and heart rate variability in the time and frequency domains were measured during spontaneous breathing and under the sham , CPAP5 and CPAP10 conditions . Results All groups experienced a reduction in ETCO2 values during treatment with CPAP ( p < 0.05 ) . CPAP increased SpO2 and HR in the COPD group ( p < 0.05 ) . The COPD group also had lower RMSSD values during treatment with different levels of CPAP when compared to the control group ( p < 0.05 ) . In the CHF group , CPAP5 and CPAP10 increased the SDNN value ( p < 0.05 ) . CPAP10 reduced the SDNN value in the COPD group ( p < 0.05 ) . Conclusion The findings suggest that CPAP may cause improvements in the neural control of heart rate in patients with stable COPD and CHF . For each patient , the “ best CPAP level ” should be defined as the best respiratory response and autonomic balance BACKGROUND AND STUDY OBJECTIVES Noninvasive positive airway pressure may play a significant role in treating patients with congestive heart failure ( CHF ) . We tested our hypothesis that noninvasive bilevel positive airway pressure improves left ventricular performance in patients with chronic CHF secondary to severe systolic dysfunction . OBJECTIVES To determine the cardiac performance of patients using bilevel positive airway pressure  , and to describe the hemodynamic effects of bilevel positive airway pressure and its use as a therapeutic adjunct in these patients . DESIGN Prospect i ve , cohort , nonr and omized study . SETTING Outpatient medicine clinic . PATIENTS Fourteen patients ( 9 men and 5 women ) with stable chronic CHF with left ventricular ejection fraction < or = 35 % ; mean age was 60.6 years ( range , 43 to 87 years ) . INTERVENTIONS Bilevel positive airway pressure via nasal mask at an inspiratory pressure of 5 cm H(2)O and an expiratory pressure of 3 cm H(2)O on spontaneous mode at room air for 1 h. MEASUREMENTS AND RESULTS Myocardial performance and changes were measured using clinical and echocardiographic parameters . Baseline clinical and echocardiographic parameters were compared with the same parameters after 1 h of bilevel positive airway pressure . Statistically significant ( p<0.05 , Wilcoxon matched pair signed-rank test ) decreases were noted in these mean values : systolic BP from 136.21 to 124.14 mm Hg ( p = 0.008 ) , heart rate from 85.07 to 74.71 beats/min ( p = 0.002 ) , respiratory rate from 23.07 to 15.43 breaths/min ( p = 0.001 ) , and systemic vascular resistance from 1671 . 46 to 1236.27 dyne . s. cm(3 ) ( p = 0.001 ) . Statistically significant increases were noted in these mean values : cardiac output from 5.09 to 6.37 L/min ( p = 0.004 ) , ejection fraction from 28.71 % to 34.36 % ( p = 0.001 ) , and end-diastolic volume from 224.36 to 246.21 mL ( p = 0.045 ) . CONCLUSION Bilevel positive airway pressure has excellent potential for improving left ventricular performance of patients with chronic CHF secondary to severe systolic dysfunction BACKGROUND Peak exercise oxygen uptake ( peak VO2 ) and ventilation to CO2 production ( VE/VCO2 ) slope are established prognostic indicators in patients with chronic heart failure ( CHF ) . A high VE/VCO2 slope , however , does not take into account the level of physical performance as expressed by peak VO2 . We hypothesized that the prognostic value of a high VE/VCO2 slope may be improved by normalization for peak VO2 ( VE/VCO2/VO2 ) . METHODS One hundred patients with CHF underwent  pulmonary function tests at rest ( spirometry and lung diffusion capacity ) and maximal cardiopulmonary exercise testing . The prognostic value of VE/VCO2 slope , peak VO2 and VE/VCO2/VO2 was probed prospect ively . RESULTS Twenty-one patients died from cardiac reasons during a mean follow-up of 26 + /- 19 months . Nonsurvivors , compared to survivors , showed a lower peak VO2 ( 13.6 + /- 4.0 vs 17.5 + /- 4.1 mL x min(-1 ) x kg(-1 ) , P < .01 ) and a steeper VE/VCO2 slope ( 43 + /- 11 vs 31.6 + /- 5.0 , P < .01 ) . Nonetheless , in patients whose VE/VCO2 slope exceeded 34 ( upper normal limit ) , there was no correlation with peak VO2 ( r = -35 , P = not significant ) . Interestingly 35 % of them showed a normal exercise performance ( peak VO2 > or = 18 mL x min(-1 ) x kg(-1 ) ) . At multivariate analysis , the VE/VCO2 slope showed a prognostic power stronger than that of peak VO2 ; however , the VE/VCO2/VO2 index retained a prognostic power greater than that of both VE/VCO2 slope and peak VO2 . A VE/VCO2/VO2 > or = 2.4 signaled cases at higher risk . CONCLUSIONS Discrepancies between VE/VCO2 slope and peak VO2 may generate uncertainty . Normalization of the former by the latter improves outcome prediction and may be considered a simple and effective way for maximizing the clinical applicability of these 2 indicators OBJECTIVE To compare the effects of an 8-week , high-intensity interval training protocol versus continuous training . DESIGN R and omized controlled trial . SETTING Cardiac rehabilitation center . PARTICIPANTS Patients ( N=26 ; mean age ± SD , 54±12y ) with chronic heart failure were enrolled in a cardiac rehabilitation program for 8 weeks . INTERVENTIONS Patients were r and omly assigned into 2 groups that performed either interval training ( IT ) or continuous training ( CT ) . IT consisted of 3 sessions of 12 repetitions of 30 seconds of exercise at very high intensity , followed by 60 seconds of complete rest . The CT group performed CT exercises , which consisted of 45 minutes of aerobic exercise . MAIN OUTCOME MEASURES Parameters of gas exchanges : peak oxygen consumption ( Vo(2)peak ) , first ventilator threshold ( VT1 ) , distance at six-minute walk test ( 6MWT ) , and level of anxiety and depression were measured . RESULTS The IT group increased significantly their Vo(2)peak , the duration of the exercise test , the oxygen pulse , oxygen consumption at the VT1 , and the distance walked during the 6MWT . The CT group only increased the time at the VT1 and the distance performed at the 6MWT . The improvement in the time at the VT1 was significantly higher for the IT group than for the CT group . CONCLUSIONS This study shows that IT at very high intensity for patients with heart failure appears to be more effective than CT in improving indices of submaximal exercise capacity STUDY OBJECTIVES Continuous positive airway pressure ( CPAP ) has been used to improve cardiopulmonary function and reduce pulmonary edema symptoms in patients with congestive heart failure ( CHF ) . The objective of this study was to evaluate the efficacy of CPAP therapy on pulmonary function and exercise tolerance in patients with CHF . DESIGN Prospect i ve blind r and omized clinical study . PARTICIPANTS Twenty-four patients with class II or III CHF and dilated cardiomyopathy were r and omly assigned to 30 min of CPAP therapy and respiratory exercises ( CPAP group ) or respiratory exercise only ( control group ) once a day for 14 days . MEASUREMENTS AND RESULTS Evaluation of pulmonary function was performed measuring FEV1 and FVC . Exercise tolerance was assessed measuring the distance walked during the 6-min walking test ( 6MWT ) . These parameters were measured before treatment and 4 days , 9 days , and 14 days later . CPAP therapy caused a progressive increase ( p < 0.05 ) in both FVC ( maximum of 16 % after 9 days ) and FEV1 ( maximum of 14 % after 14 days ) compared to basal values , without significant changes in the control group . The 6MWT showed a progressive improvement in the distance walked in the CPAP group , reaching approximately 28 % above the basal values in the CPAP group and without significant changes in the control group . CONCLUSIONS These data show that the use of CPAP therapy for 2 weeks on a daily basis is able to enhance pulmonary function and consequently improve the tolerance to physical activities in patients with CHF . The clinical implication of this finding is that CPAP therapy could potentially be used as an adjunct to the treatment of CHF patients OBJECTIVE To compare the effects of 3 types of noninvasive respiratory support systems in the treatment of acute pulmonary edema :  oxygen therapy ( O2 ) , continuous positive airway pressure , and bilevel positive pressure ventilation . METHODS We studied prospect ively 26 patients with acute pulmonary edema , who were r and omized into 1 of 3 types of respiratory support groups . Age was 69+/-7 years . Ten patients were treated with oxygen , 9 with continuous positive airway pressure , and 7 with noninvasive bilevel positive pressure ventilation . All patients received medicamentous therapy according to the Advanced Cardiac Life Support protocol . Our primary aim was to assess the need for orotracheal intubation .  We also assessed the following : heart and respiration rates , blood pressure , PaO2 , PaCO2 , and pH at beginning , and at 10 and 60 minutes after starting the protocol . RESULTS At 10 minutes , the patients in the bilevel positive pressure ventilation group had the highest PaO2 and the lowest respiration rates ; the patients in the O2 group had the highest PaCO2 and the lowest pH ( p<0.05 ) . Four patients in the O2 group , 3 patients in the continuous positive pressure group , and none in the bilevel positive pressure ventilation group were intubated ( p<0.05 ) . CONCLUSION Noninvasive bilevel positive pressure ventilation was effective in the treatment of acute cardiogenic pulmonary edema , accelerated the recovery of vital signs and 
    Output:
    
The use of NIV prior to the 6MWT in patients with HF may promote increased distance .