***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: Oxygen supplementation may improve exercise tolerance and the physiological response to exercise in cystic fibrosis ( CF ) patients . Elevated barometric pressure at low altitude is a simple means of increasing the quantity of inspired oxygen . Our objectives were to examine the effect of natural oxygen enrichment ( at the Dead Sea , 396 m below sea level ) on exercise capacity , and the physiological responses to maximal and submaximal exercise in CF patients . Patients were tested twice : at sea level ( barometric pressure , 754 + /- 6 mmHg , mean + /- SD ) , and at the Dead Sea ( barometric pressure , 791 + /- 3 mmHg ) , in a r and omized crossover design . We studied 14 CF patients ( 6 females , 8 males ) , aged 15 - 45 years , with moderate to severe lung disease ( mean forced expired volume in 1 sec = 50.0 + /- 11.2 % predicted ) . Tests at each site included resting spirometry , anthropometry , a grade d submaximal exercise test , a maximal exercise test on a treadmill , and a 6-min walk test . Tests were performed in identical order at both sites . Tests at the Dead Sea were performed 72 hr after arrival . No differences between sites were observed in lung function at rest . Peak oxygen consumption was significantly improved at the Dead Sea compared with sea level ( 1.68 + /- 0.73 vs. 1.57 + /- 0.74 l/min , respectively , P = 0.05 ) , along with an improvement in the ventilatory equivalent for oxygen ( 41.2 + /- 6.3 vs. 46.1 + /- 7.1 , respectively , P < 0.05 ) . During submaximal exercise , blood oxygen saturation improved at the Dead Sea compared with sea level at all exercise intensities ( P < 0.05 ) . In conclusion , these results suggest that even a brief stay at the Dead Sea area may have physiological benefits for CF patients with moderate to severe lung disease Patients with cystic fibrosis ( CF ) and advanced pulmonary disease have pulmonary limitation of exercise , often associated with arterial oxygen desaturation . Improving oxygenation during exercise by providing supplemental oxygen may improve exercise performance in these patients . To test this , we performed grade d exercise stress tests in 22 CF patients with severe pulmonary disease ( mean PaO2 , 64 + /- 2 mm Hg [ + /- SE ] ; PaCO2 46 + /- 2 mm Hg ; RV/TLC , 57 + /- 4 percent ; FEV1 , 38 + /- 4 percent of predicted ; FEF25 - 75 % , 13 + /- 2 percent of predicted ; median age , 26 years ) and compared them to 21 controls ( RV/TLC , 27 + /- 4 percent ; FEV1 , 112 + /- 2 percent of predicted ; FEF25 - 75 % , 80 + /- 4 percent of predicted ; median age , 29 years ) . Each subject performed grade d exercise stress tests while breathing FIO2 of 0.21 and FIO2 of 0.30 . Subjects were blinded to the composition of the inspired gas , and the order of testing was r and omized . We found that CF subjects exercised longer , had a higher maximal VO2 , higher O2 pulse , and less arterial oxygen desaturation when receiving supplemental O2 . Control subjects exercised longer when breathing supplemental O2 but had no significant change in maximal VO2 , O2 pulse , or SaO2 . Both CF and control subjects had increased end-tidal PCO2 when exercising while breathing supplemental O2 . We conclude that CF patients with advanced pulmonary disease have increased exercise tolerance and aerobic capacity when exercising while breathing supplemental O2 The effects of supplemental O2 on recovery from  supramaximal exercise  and subsequent performance remain unknown . If recovery from exercise could be enhanced in individuals with chronic lung disease , subsequent supramaximal exercise performance could also be improved . Recovery from  supramaximal exercise  and subsequent supramaximal exercise performance  were assessed after 10 min of breathing 100 % O2 or room air ( RA ) in 17 cystic fibrosis ( CF ) patients [ 25 + /- 10 ( SD ) yr old , 53 % men , forced expired volume in 1 s = 62 + /- 21 % predicted ] and 17 normal subjects ( 25 + /- 8 yr old , 59 % men , forced expired volume in 1 s = 112 + /- 15 % predicted ) .  Supramaximal performance  was assessed as the work of  sustained bicycling at a load of 130 % of the maximum load achieved during a grade d maximal exercise .  Peak minute ventilation ( VE ) and heart rate ( HR ) were lower in CF patients at the end of each supramaximal bout than in controls . In CF patients , single-exponential time decay constants indicated faster recovery of HR ( tau HR = 86 + /- 8 and 73 + /- 6 s in RA and O2 , respectively , P < 0.01 ) . Similarly , fast and slow time constants of two-exponential equations providing the best fit for ventilatory recovery were improved in CF patients during O2 breathing ( tau 1VE = 132.1 + /- 10.5 vs. 82.5 + /- 10.4 s ; tau 2VE = 880.3 + /- 300.1 vs. 368.6 + /- 107.1 s , P < 0.01 ) . However , no such improvements occurred in controls . Supramaximal performance after O2 improved in CF patients ( 109 + /- 6 % of the 1st bout after O2 vs. 94 + /- 6 % in RA , P < 0.01 ) . O2 supplementation had no effect on subsequent performance in controls ( 97 + /- 3 % in O2 vs. 93 + /- 3 % in RA ) . We conclude that supplemental O2 after a short bout of supramaximal exercise accelerates recovery and preserves subsequent supramaximal performance in patients with CF We tested the hypothesis that maximal exercise performance in adults with cystic fibrosis is limited by arterial hypoxemia . In study 1 , patients completed two maximal exercise tests , a control and a test with 400 ml of added dead space .  Maximal O2 consumption was significantly lower in the added dead space study vs. control ( 1.04 + /- 0.15 vs. 1.20 + /- 0.11 l/min ; P < 0.05 ) , with no difference in peak ventilation . There was significant O2 desaturation during exercise that was equal in both control and added dead space studies . The decrease in maximal O2 consumption with added dead space suggests that maximal exercise in cystic fibrosis is limited by respiratory factors . We subsequently examined whether pulmonary mechanics or arterial hypoxemia limits maximal exercise performance . In study 2 , patients completed two maximal exercise tests , a control and a test with 400 ml of added dead space while also breathing 38 % O2 . Added dead space was used to overcome the suppressive effects of hyperoxia on minute ventilation . Maximal O2 consumption was significantly higher with added dead space and 38 % O2 vs. control ( 1.62 + /- 0.16 vs. 1.43 + /- 0.14 l/min ; P < 0.05 ) . Peak ventilation and O2 saturation were significantly greater in the added dead space and 38 % O2 test vs. control . The increase in maximal O2 consumption and peak ventilation with added dead space and 38 % O2 suggests that maximal exercise in cystic fibrosis is limited by arterial hypoxemia Background : The clinical benefits of domiciliary non-invasive positive pressure ventilation ( NIV ) have not been established in cystic fibrosis ( CF ) . We studied the effects of nocturnal NIV on quality of life ( QoL ) , functional and physiological outcomes in CF subjects with awake hypercapnia ( arterial carbon dioxide pressure Paco2>45 mm Hg ) . Methods : In a r and omised , placebo controlled , crossover study , eight subjects with CF , mean ( SD ) age 37 ( 8) years , body mass index 21.1 ( 2.6 ) kg/m2 , forced expiratory volume in 1 s 35 (8)% predicted and Paco2 52 ( 4 ) mm Hg received 6 weeks of nocturnal ( 1 ) air ( placebo ) , ( 2 ) oxygen and ( 3 ) NIV . The primary outcome measures were CF specific QoL , daytime sleepiness and exertional dyspnoea . Secondary outcome measures were awake and asleep gas exchange , sleep architecture , lung function and peak exercise capacity . Results : Compared with air , NIV improved the chest symptom score in the CF QoL Question naire ( mean difference 10 ; 95 % CI 5 to 16 ; p = 0.002 ) and the transitional dyspnoea index score ( mean difference 3.1 ; 95 % CI 1.2–5.0 ; p = 0.01 ) . It reduced maximum nocturnal pressure of transcutaneous CO2 ( Ptcco2 mean difference −17 mm Hg ; 95 % CI −7 to −28 mm Hg ; p = 0.005 ) and increased exercise performance on the Modified Shuttle Test ( mean difference 83 m ; 95 % CI 21 to 144 m ; p = 0.02 ) . NIV did not improve sleep architecture , lung function or awake Paco2 . Conclusion : 6 weeks of nocturnal NIV improves chest symptoms , exertional dyspnoea , nocturnal hypoventilation and peak exercise capacity in adult patients with stable CF with awake hypercapnia . Further studies are required to determine whether or not NIV can improve survival Objective The aim of the study was to evaluate the effect of the back-up rate on respiratory effort during non-invasive mechanical ventilation . Design An in vitro study evaluated the inspiratory trigger in seven  domiciliary ventilators . Then , a prospect i ve , r and omized , crossover trial compared the effect on respiratory effort of three different back-up rates during pressure support ( PS ) and assist-control/volume-targeted ( AC/VT ) ventilation . Setting A research unit and a tertiary referral pediatric center . Patients Ten patients with cystic fibrosis ( CF ) . Interventions During the in vivo study , the back-up rate was progressively increased to the maximum that patients could tolerate ( Fmax ) and respiratory effort , as judged by pressure/time product of the diaphragm ( PTPdi/min ) , was compared between the two ventilatory modes . Results Differences were observed between trigger pressure , trigger time delay , trigger pressure/time product and the slope between flow and pressure in the seven ventilators . PS and AC/VT ventilation were associated with a decrease in respiratory effort ( PTPdi/min was 518±172 , 271±119 and 291±138 cmH2O . s−1 . min-1 , for spontaneous breathing , PS and AC/VT ventilation , respectively , p=0.05 ) . During the two modes , increasing the back-up rate to Fmax result ed in a greater reduction in PTPdi/min ( p=0.001 ) , which was more pronounced during AC/VT ventilation , due to the automatic adjustment of the inspiratory/expiratory time ratio . Conclusions Increasing the back-up rate during PS and AC/VT ventilation decreases respiratory effort in young patients with CF , but this effect was more marked with AC/VT ventilation Recombinant human deoxyribonuclease I ( dornase alfa ) is currently used as an inhaled mucoactive agent in the treatment of cystic fibrosis . In a r and omized , placebo-controlled , double-blind clinical study in 100 infants , we investigated whether the therapeutic use of dornase alfa can be extended to ventilated , fluid-restricted children to reduce reintubation rate , ventilation duration , pediatric intensive care unit ( PICU ) stay , and ventilation complications . While reintubation rates were similar for dornase alfa 7 % vs. placebo 9 % ( odds ratio , 0.77 ; confidence interval , 0.11 - 4.9 ) , the incidence of atelectasis ( 6 vs. 17 , respectively ; P-value 0.051 ) , median ventilation time ( 2.2 vs. 3.4 days , respectively ; P-value 0.043 ) , median length of PICU stay ( 7 vs. 8 days , respectively ; P-value 0.051 ) , and mean costs ( 4,830 vs. 6,320 , respectively ) were lower in the dornase alfa group . No adverse effects were observed , even in critically ill patients . We found that dornase alfa was beneficial and safe . Our findings also indicate that dornase alfa is possibly of value from the first day of mechanical ventilation onward , particularly when longer ventilation ( > 3 days ) is expected in fluid-restricted children after cardiac surgery We measured ventilation in all sleep stages in patients with cystic fibrosis ( CF ) and moderate to severe lung disease , and compared the effects of low-flow oxygen ( LFO2 ) and bilevel ventilatory support ( BVS ) on ventilation and gas exchange during sleep . Thirteen subjects , age 26 + /- 5.9 yr ( mean + /- 1 SD ) , body mass index ( BMI ) 20 + /- 3 kg/m2 , FEV1 32 + /- 11 % predicted , underwent three sleep studies breathing , in r and om order , room air ( RA ) , LFO2 , and BVS + /- O2 with recording of oxyhemoglobin saturation ( SpO2 ) ( 
    Output:
    
There was no statistically significant improvement in survival , lung , or cardiac health .
Although oxygenation improved , mild hypercapnia was noted .
Participants fell asleep quicker and spent a reduced percentage of total sleep time in rapid eye movement sleep , but there were no demonstrable improvements in qualitative sleep parameters .
Again , oxygenation improved , but mild hypercapnia result ed .
Other exercise parameters were not altered by the use of oxygen .
There are no published data to guide the prescription of chronic oxygen supplementation to people with advanced lung disease due to CF .
Short-term oxygen therapy during sleep and exercise improves oxygenation but is associated with modest and probably clinical ly inconsequential hypercapnia .
There are improvements in exercise duration , time to fall asleep and regular attendance at school or work .