***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: The beneficial effects of nocturnal oxygen therapy ( NOT ) in chronic obstructive pulmonary disease ( COPD ) patients with mild-to-moderate daytime hypoxaemia ( arterial oxygen tension ( Pa , O2 ) in the range 7.4 - 9.2 kPa ( 56 - 69 mmHg ) ) and exhibiting sleep-related oxygen desaturation remains controversial . The effectiveness of NOT in that category of COPD patients was studied . The end points included pulmonary haemodynamic effects after 2 yrs of follow-up , survival and requirement for long-term oxygen therapy ( LTOT ) .  Seventy-six patients could be r and omized , 41 were allocated to NOT and 35 to no NOT ( control ) . The goal of NOT was to achieve an arterial oxygen saturation of > 90 % throughout the night . All these patients underwent polysomnography to exclude an associated obstructive sleep apnoea syndrome . The two groups exhibited an identical meansD daytime Pa , O2 of 8.4+/-0.4 kPa ( 63+/-3 mmHg ) at baseline . Twenty-two patients ( 12 in the NOT group and 10 in the control group , p=0.98 ) required LTOT during the whole follow-up ( 35+/-14 months ) . Sixteen patients died , nine in the NOT group and seven in the control group ( p=0.84 ) . Forty-six patients were able to undergo pulmonary haemodynamic re-evaluation after 2 yrs , 24 in the NOT and 22 in the control group . In the control group , mean resting pulmonary artery pressure increased from 19.8+/-5.6 to 20.5 + 6.5 mmHg , which was not different from the change in mean pulmonary artery pressure in the NOT group , from 18.3+/-4.7 to 19.5+/-5.3 mmHg ( p= 0.79 ) . Nocturnal oxygen therapy did not modify the evolution of pulmonary haemodynamics and did not allow delay in the prescription of long-term oxygen therapy . No effect of NOT on survival was observed , but the small number of deaths precluded any firm conclusion . These results suggest that the prescription of nocturnal oxygen therapy in isolation is probably not justified in chronic obstructive pulmonary disease patients BACKGROUND : To date only two controlled studies have been published on the effects of domiciliary oxygen treatment on survival in patients with chronic obstructive pulmonary disease ( COPD ) with advanced respiratory failure . The survival in such patients despite oxygen treatment remains poor . The prescription of long term oxygen therapy ( LTOT ) in less severe disease remains controversial . The aim of this study was to evaluate the rationale for prescribing oxygen to patients with COPD with moderate hypoxaemia . METHODS : One hundred and thirty five patients with COPD , with PaO2 7.4 - 8.7 kPa ( 56 - 65 mmHg ) and advanced airflow limitation ( mean ( SD ) forced expiratory volume in one second ( FEV1 ) 0.83 ( 0.28 ) 1 ) , were r and omly allocated to a control ( n = 67 ) and LTOT ( n = 68 ) group . The patients were followed every three months for at least three years or until death . RESULTS : The cumulative survival rate was 88 % at one year , 77 % at two years , and 66 % at three years . No significant differences were found in survival rates between patients treated with LTOT and controls , nor did longer oxygen use ( over 15 hours per day ) improve survival . Younger age , better spirometric values , and higher body mass index predicted better survival . CONCLUSIONS : Domiciliary oxygen treatment does not prolong survival in patients with COPD with moderate hypoxaemia . Airway limitation seems to determine survival in this group of patients The efficacy of nasal oxygen during sleep was evaluated in patients with COPD , episodic rapid eye movement sleep desaturation , and a daytime PaO2 greater than 60 mm Hg . The double-blind , r and omized 3-yr trial used nasal oxygen versus room air in two groups of nocturnal sleep desaturating subjects . The setting was the outpatient chest clinic of a Veterans Affairs Medical Center . There were 51 patients with moderate to severe COPD , daytime PaO2 greater than or equal to 60 mm Hg : 38 with proven REM sleep desaturation and 13 without desaturation .  Nocturnal oxygen at 3 L/min was delivered by concentrator to 19 desaturating subjects , and room air at 3 L/min was delivered by defective concentrator to the remaining 19 desaturating subjects . There was no gas therapy for the 13 nondesaturating subjects . The nocturnal desaturator group who received supplemental oxygen during sleep over 36 months showed a significant downward trend in pulmonary artery pressure ( -3.7 mm Hg ) compared with desaturating patients treated with room air ( + 3.9 mm Hg ) . Nonvascular parameters of hypoxia , such as hemoglobin and red blood cell mass , did not differ between the sham- and oxygen-treated groups . Mortality was decidedly higher in the desaturating patients compared with non-desaturating subjects , but there was no significant difference between oxygen- and sham-treated desaturating subjects . We conclude that nasal supplemental oxygen used during sleep to reverse episodic desaturation in COPD patients whose daytime PaO2 is above 60 mm Hg has a beneficial effect in reducing pulmonary artery pressure . ( ABSTRACT TRUNCATED AT 250 WORDS At six centers , 203 patients with stabilized hypoxemic chronic obstructive pulmonary disease were evaluated hemodynamically during a continuous or 12-hour oxygen therapy program . Neither oxygen therapy program result ed in correction or near-correction of the baseline hemodynamic abnormalities . The continuous oxygen therapy group did show improvement in pulmonary vascular resistance , pulmonary arterial pressure , and stroke volume index . The improvement in pulmonary vascular resistance was associated with improved cardiac function , as evidence d by an increase in baseline and exercise stroke volume index . The nocturnal oxygen therapy group showed stable hemodynamic variables . For both groups , changes in mean pulmonary artery pressure during the first 6 months were associated with subsequent survival after adjustment for association with the baseline mean pulmonary artery pressure . Continuous oxygen therapy can improve the hemodynamic abnormalities of patients with hypoxic chronic obstructive pulmonary disease . The hemodynamic response to this treatment is predictive of survival 
    Output:
    
REVIEW ER 'S CONCLUSIONS Long term oxygen therapy improved survival in a selected group of COPD patients with severe hypoxaemia ( arterial PO2 less than 8.0 kPa ) .
Long term oxygen did not appear to improve survival in patients with moderate hypoxaemia or in those with only arterial desaturation at night