***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 Supplemental oxygen in patients with chronic obstructive pulmonary disease ( COPD ) and exercise hypoxaemia improves exercise capacity and dyspnoea . However , the benefit of oxygen during pulmonary rehabilitation in these patients is still unknown . METHODS Twenty five patients with stable COPD ( mean ( SD ) forced expiratory volume in one second ( FEV1 ) 0.76 ( 0.29 ) l and 30.0 (9.89)% predicted , arterial oxygen tension ( Pao 2 ) 8.46 ( 1.22 ) kPa , arterial carbon dioxide tension ( Paco 2 ) 6.32 ( 1.01 ) kPa ) and significant arterial desaturation on exercise ( 82.0 (10.4)% ) were entered onto a pulmonary rehabilitation programme . Patients were r and omised to train whilst breathing oxygen ( OT ) ( n = 13 ) or air ( AT ) ( n = 12 ) , both at 4 l/min . Assessment s included exercise tolerance and associated dyspnoea using the shuttle walk test ( SWT ) and Borg dyspnoea score , health status , mood state , and performance during daily activities . RESULTS The OT group showed a significant reduction in dyspnoea after rehabilitation compared with the AT group ( Borg mean difference –1.46 ( 95 % CI –2.72 to –0.19 ) ) but there were no differences in other outcome measures : SWT difference –23.6 m ( 95 % CI –70.7 to 23.5 ) , Chronic Respiratory Disease Question naire 3.67 ( 95 % CI –7.70 to 15.1 ) , Hospital Anxiety and Depression Scale 1.73 ( 95 % CI –2.32 to 5.78 ) , and London Chest Activity of Daily Living Scale –2.18 ( 95 % CI –7.15 to 2.79 ) . At baseline oxygen significantly improved SWT ( mean difference 27.3 m ( 95 % CI 14.7 to 39.8 ) and dyspnoea ( –0.68 ( 95 % CI –1.05 to –0.31 ) ) compared with placebo air . CONCLUSIONS This study suggests that supplemental oxygen during training does little to enhance exercise tolerance although there is a small benefit in terms of dyspnoea . Patients with severe disabling dyspnoea may find symptomatic relief with supplemental oxygen Supplemental oxygen improves exercise tolerance of normoxemic and hypoxemic chronic obstructive pulmonary disease ( COPD ) patients . We determined whether nonhypoxemic COPD patients undergoing exercise training while breathing supplemental oxygen  achieve higher intensity and therefore improve exercise capacity more than patients breathing air . A double-blinded trial was performed involving 29 nonhypoxemic patients ( 67 years , exercise SaO2 > 88 % ) with COPD ( FEV1 = 36 % predicted ) . All exercised on cycle ergometers for 45 minutes , 3 times per week for 7 weeks at high-intensity targets . During exercise , they received oxygen ( 3 L/minute ) ( n = 14 ) or compressed air ( 3 L/minute ) ( n = 15 ) . Both groups had a higher exercise tolerance after training and when breathing oxygen . However , the oxygen-trained group increased the training work rate more rapidly than the air-trained group . The mean + /- SD work rate during the last week was 62 + /- 19 W ( oxygen-trained group ) and 52 + /- 22 W ( air-trained group ) ( p < 0.01 ) . After training , endurance in constant work rate tests increased more in the oxygen-trained group ( 14.5 minutes ) than in the air-trained group ( 10.5 minutes ) ( p < 0.05 ) . At isotime , the breathing rate decreased four breaths per minute in the oxygen-trained group and one breath per minute in the air-trained group ( p = 0.001 ) . We conclude that supplemental oxygen provided during high-intensity training yields higher training intensity and evidence of gains in exercise tolerance in laboratory testing PURPOSE To quantify the effects of acute oxygen supplementation on lower limb blood flow ( QLEG ) , O2 delivery ( QO2LEG ) , and O2 uptake ( VO2LEG ) during exercise and to determine whether the metabolic capacity of the lower limb is exhausted at peak exercise during room air breathing in patients with COPD . METHODS Oxygen ( FIO2 = 0.75 ) and air were r and omly administered to 14 patients with COPD ( FEV1 : 35 + /- 2 % pred , mean + /- SEM ) during two symptom-limited incremental cycle exercise tests . Before exercise , a cannula was installed in a radial artery and a thermodilution catheter inserted in the right femoral vein . At each exercise step , five-breath averages of respiratory rate , tidal volume , and ventilation ( VE ) , dyspnea and leg fatigue scores , arterial and venous blood gases , and QLEG were obtained . From these measurements , VO2LEG was calculated . RESULTS Peak exercise capacity increased from 46 + /- 3 W in room air to 59 + /- 5 W when supplemental oxygen was used ( P < 0.001 ) . QLEG , QO2LEG , and VO2LEG were greater at peak exercise with O2 than with air ( P < 0.05 ) . During submaximal exercise , dyspnea score and VE were significantly reduced with O2 ( P < 0.05 ) , whereas QLEG , VO2LEG , and leg fatigue were similar under both experimental conditions . The improvement in peak exercise work rate correlated with the increase in peak QO2LEG ( r = 0.66 , P < 0.01 ) , peak VO2LEG ( r = 0.53 , P < 0.05 ) , and reduction in dyspnea at iso-exercise intensity ( r = 0.56 , P < 0.05 ) . CONCLUSION The improvement in peak exercise capacity with oxygen supplementation could be explained by the reduction in dyspnea at submaximal exercise and the increases in QO2LEG and VO2LEG , which enabled the exercising muscles to perform more external work . These data indicate that the metabolic capacity of the lower limb muscles was not exhausted at peak exercise during room air breathing in these patients with COPD BACKGROUND Oxygen conserving devices may lead to substantial increases in the duration of oxygen provided . A study was undertaken to compare the performance of a pulsed dose oxygen delivery ( PDOD ) system with continuous flow oxygen or air during a maximal walking test . METHODS Fourteen patients with chronic obstructive pulmonary disease ( COPD ) and arterial oxygen desaturation on exercise ( mean ( SD ) forced expiratory volume in one second ( FEV1 ) 0.83 ( 0.28 ) l , arterial oxygen pressure ( Pao 2 ) 8.38 ( 1.24 ) kPa , arterial carbon dioxide pressure ( Paco 2 ) 5.95 ( 0.86 ) kPa ) were r and omised to perform a walking test using air administered via a cylinder or continuous flow oxygen at 2 l/min or by a PDOD system . RESULTS There was no significant difference in the mean arterial oxygen saturation ( Sao 2 ) using the PDOD system or with continuous flow oxygen ( p = 0.33 ) . Patients showed greatest desaturation whilst walking with the air cylinder ( Sao 2 79.2 (8.59)% ) which was significantly different from the desaturation with both continuous flow oxygen ( 87.6 (5.85)% , p = 0.001 ) and PDOD ( 85.6 (7.36)% , p = 0.004 ) . There was no significant difference between the distance walked using oxygen delivered at 2 l/min by continuous flow or via the PDOD ( p = 0.72 ; CI 0.34 to 1.08 ) . The mean ( SD ) distance walked on continuous flow oxygen ( 203.6 ( 106.1 ) m ) and PDOD ( 207.9 ( 109.8 ) m ) was significantly greater than the distance walked with the air cylinder ( 188.6 ( 110.02 ) m ) ; ( 1.12 fold increase in distance , CI 1.01 to 1.23 , p = 0.02 , and 1.14 fold increase in distance , CI 1.01 to 1.28 , p = 0.03 , respectively ) . CONCLUSIONS These findings suggest that the pulsed dose oxygen conserving device was as effective as continuous flow oxygen in maintaining arterial oxygen saturation and that the use of this device was associated with similar improvements in exercise tolerance to patients taking continuous flow oxygen therapy A r and omized , controlled , single-blind study was performed on 20 patients with chronic obstructive pulmonary disease and exercise-induced hypoxaemia . Ten patients each were r and omly assigned to one of two groups , one training with air and the other training with oxygen . There were no significant differences between the groups regarding values measured prior to the study . The patients trained 3 times per week for 30 minutes each time for a duration of 8 weeks . The training consisted of interval walking on a treadmill ( intensity set according to Borg ratings ) with either air or oxygen administered through a nasal cannula at a rate of 5 l/min . Training significantly improved the 6-minute walking distance by 20 % and 14 % in the air and oxygen group , respectively , when the patients were tested on air . In the same test the air group significantly decreased Borg ratings for perceived exertion . Borg ratings for dyspnoea and perceived exertion significantly decreased in the oxygen group when they were tested on oxygen . It was concluded that oxygen supplementation did not further improve the training effect , compared with training with air , in patients with chronic obstructive pulmonary disease and exercise-induced hypoxaemia Supplemental oxygen has acute beneficial effects on exercise performance in patients with chronic obstructive pulmonary disease ( COPD ) . The purpose of this study was to investigate whether oxygen-supplemented training enhances the effects of training while breathing room air in patients with severe COPD . A r and omized controlled trial was performed in 24 patients with severe COPD who developed hypoxaemia during incremental cycle exercise ( arterial oxygen saturation ( Sa , O2 ) < 90 % at peak exercise ) . All patients participated in an in-patient pulmonary rehabilitation programme of 10 weeks duration . They were assigned either to general exercise training while breathing room air ( GET/RA group : forced expiratory volume in one second ( FEV1 ) 38 % of predicted ; arterial oxygen tension ( Pa , O2 ) 10.5 kPa at rest ; Pa , O2 7.3 kPa at peak exercise ) , or to GET while breathing supplemental oxygen ( GET/O2 group : FEV1 29 % pred ; Pa , O2 10.2 kPa at rest ; Pa , O2 7.2 kPa at peak exercise ) . Sa , O2 was not allowed to fall below 90 % during the training . The effects on exercise performance while breathing air and oxygen , and on quality of life were compared . Maximum workload ( Wmax ) significantly increased in the GET/RA group ( mean ( SD ) 17 ( 15 ) W , p<0.01 ) , but not in the GET/O2 group ( 7 ( 25 ) W ) . Six minute walking distance ( 6MWD ) , stair-climbing , weight-lifting exercise ( all while breathing room air ) and quality of life significantly increased in both groups . Acute administration of oxygen improved exercise performance before and after training . Training significantly increased Wmax , peak carbon dioxide production ( V'CO2 ) and 6MWD while breathing oxygen in both groups . Differences between groups were not significant . Pulmonary rehabilitation improved exercise performance and quality of life in both groups . Supplementation of oxygen during the training did not add to the effects of training on room air In 159 chronic obstructive pulmonary disease ( COPD ) patients ( 139 males , mean age 62 + /- 8 yrs , arterial oxygen tension ( PaO2 ) 7.2 + /- 0.9 kPa ) , on long-term oxygen therapy ( LTOT ) , we evaluated the effects of portable oxygen therapy both on the daily duration of oxygen therapy and on daily activities . They were given two types of LTOT at r and om : group A ( n = 75 ) , oxygen concentrators only ( OC ) ; group B ( n = 84 ) , either small oxygen cylinders plus OC ( B1 = 51 ) or liquid oxygen ( B2 = 33 ) . The patients were followed-up for one year by means of : a ) medical examination every three months ; b ) monthly home interviews concerning the daily duration of oxygen therapy , the utilization of the devices and the daily activities of the patients ; c ) a measurement of the  daily oxygen usage .  The results show that : 1 ) there are no significant clinical and functional differences between groups A and B at the onset of and throughout the study ; 2 ) in group B the daily use of oxygen therapy is significantly longer than in group A ( 17 + /- 3.5 h.day-1 vs 14 + /- 3 h.day-1 , p less than 0.01 ) without any difference between groups B1 and B2 ; 3 ) outdoor walking activities are different between groups A and B , at least in those patients using oxygen more than 18 h.day-1 . Only 60 % of patients in group B ( 55 % of B1 ; 67 
    Output:
    
Oxygen improved breathlessness , SaO2/PaO2 and VE at isotime with endurance exercise testing .
Oxygen improved SaO2/PaO2 and reduced VE at Isotime .
This review provides some evidence from small , single assessment studies that ambulatory oxygen improves exercise performance in people with moderate to severe COPD .