human
***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: Objective To examine whether postoperative mechanical ventilation with lower tidal volumes ( VT ) has protective effects on inflammatory responses induced by  cardiopulmonary bypass ( CPB )  surgery in smokers and nonsmokers . Design and setting Prospect i ve , r and omized , controlled clinical trial in the intensive care unit of a university hospital . Patients and participants We examined 44 patients ( 22 smokers , 22 nonsmokers ) immediately after uncomplicated CPB surgery . Interventions Ventilation was applied for 6 h with either VT of either 6 or 12 ml/kg ideal body weight . Measurements and results The time course of serum tumor necrosis factor ( TNF ) α , interleukin ( IL ) 6 , and IL-8 determined 0 , 2 , 4 , and 6 h after r and omization did not differ significantly between the ventilatory strategies . By contrast , in bronchoalveolar lavage fluids sample d after 6 h only TNF-α levels were significantly higher in the high VT group than the low VT group ( 50±111 pg/ml vs. 1±7 pg/ml ) . IL-6 and IL-8 concentrations did not differ between groups . Subgroup analysis of patients with serum TNF-α level higher than 0 pg/ml after surgery revealed lower TNF-α serum levels during lower VT ventilation . All observed effects were small , independent of patients ’ history of smoking , and were not correlated with duration of ventilation and ICU stay . Conclusions Ventilation with lower VT had no or only minor effect on systemic and pulmonary inflammatory responses in patients with healthy lungs after uncomplicated CPB surgery . Our data do not suggest a clinical benefit of using low VT ventilation in these selected patients BACKGROUND Cardiac surgery-related pulmonary complications include alterations in lung mechanics and anomalies in gas exchange . Higher levels of positive end-expiratory pressure ( PEEP ) have been suggested to benefit cardiac surgical patients . We compared respiratory compliance , arterial oxygenation and time till tracheal extubation in 2 cohorts of patients weaned from mechanical ventilation with different levels of PEEP after elective and uncomplicated coronary artery bypass grafting ( CABG ) . We hypothesized that higher PEEP levels improve pulmonary compliance and gas exchange in the first hours of weaning from mechanical ventilation , but not to shorten time till tracheal extubation . METHODS Secondary retrospective analysis of 2 r and omized controlled trials : in the first trial patients were weaned with PEEP levels of 10 cmH2O for the first 4 hours followed by PEEP levels of 5 cmH2O until tracheal extubation ( high PEEP , HP ) ; and the second trial patients were weaned with PEEP levels of 5 cmH2O during the entire weaning phase ( low PEEP , LP ) . The primary endpoint was pulmonary compliance . Secondary endpoints included arterial oxygenation , duration of mechanical ventilation and postoperative pulmonary complications . RESULTS The analysis included 121 patients ; 60 HP patients and 61 LP patients . Baseline characteristics were similar . Compared to LP patients , HP patients had a better pulmonary compliance , 47.2±14.1 versus 42.7±10.2 ml/cmH2O ( P<0.05 ) , and higher levels of PaO2 , 18.5±6.6 ( 138.75±49.5 ) versus 16.7±5.4 ( 125.25±40.5 ) kPa ( mmHg ) ( P<0.05 ) . Patients in the HP group were less frequent in need of supplementary oxygen after ICU discharge . These differences remained present during the entire weaning phase , even after reduction of PEEP . However , HP patients had a longer time till tracheal extubation , 16.9±6.1 versus 10.5±5.0 hours ( P<0.001 ) . HP patients had longer duration s of postoperative infusion of propofol , 4.9 ( 2.6 - 7.4 ) versus 3.5 ( 1.8 - 5.8 ) hours ( P<0.05 ) . There were no differences in use of inotropes . Cumulative fluid balances were slightly higher in HP patients . CONCLUSION Use of higher PEEP levels after elective uncomplicated CABG improves pulmonary compliance and oxygenation but seems to be associated with a delay in tracheal extubation Introduction Mechanical ventilation ( MV ) with high tidal volumes may induce or aggravate lung injury in critical ill patients . We compared the effects of a protective versus a conventional ventilatory strategy , on systemic and lung production of tumor necrosis factor-α ( TNF-α ) and interleukin-8 ( IL-8 ) in patients without lung disease . Methods Patients without lung disease and su bmi tted to mechanical ventilation admitted to one trauma and one general adult intensive care unit of two different university hospitals were enrolled in a prospect i ve r and omized-control study . Patients were r and omized to receive MV either with tidal volume ( VT ) of 10 to 12 ml/kg predicted body weight ( high VT group ) ( n = 10 ) or with VT of 5 to 7 ml/kg predicted body weight ( low VT group ) ( n = 10 ) with an oxygen inspiratory fraction ( FIO2 ) enough to keep arterial oxygen saturation > 90 % with positive end-expiratory pressure ( PEEP ) of 5 cmH2O during 12 hours after admission to the study . TNF-α and IL-8 concentrations were measured in the serum and in the bronchoalveolar lavage fluid ( BALF ) at admission and after 12 hours of study observation time . Results Twenty patients were enrolled and analyzed . At admission or after 12 hours there were no differences in serum TNF-α and IL-8 between the two groups . While initial analysis did not reveal significant differences , st and ardization against urea of logarithmic transformed data revealed that TNF-α and IL-8 levels in bronchoalveolar lavage ( BAL ) fluid were stable in the low VT group but increased in the high VT group ( P = 0.04 and P = 0.03 ) . After 12 hours , BALF TNF-α ( P = 0.03 ) and BALF IL-8 concentrations ( P = 0.03 ) were higher in the high VT group than in the low VT group . Conclusions The use of lower tidal volumes may limit pulmonary inflammation in mechanically ventilated patients even without lung injury . Trial Registration Clinical Trial registration : OBJECTIVE To compare the effects of different levels of positive end-expiratory pressure on respiratory mechanics and oxygenation indexes in the immediate postoperative period of coronary artery bypass grafting . METHODS R and omized clinical trial in which 136 patients underwent coronary artery bypass grafting between January 2011 and March 2012 were divided into three groups and admitted to mechanical ventilation with different positive end-expiratory pressure levels : Group A , 5 cmH2O ( n=44 ) , Group B , 8 cmH2O ( n=47 ) and Group C , 10 cmH2O ( n=45 ) . Data about respiratory mechanics were obtained from mechanical ventilator monitor and oxygenation indexes from arterial blood gas sample s , collected twenty minutes after intensive care unit admission . Patients with chronic obstructive pulmonary disease and patients su bmi tted to off-pump , emergency or combined operations were not included . For statistical analysis , we used Kruskal-Wallis , G and Chi-square tests , considering results significant when P<0.05 . RESULTS Groups were homogeneous in terms of demographic , clinical and surgical variables . Patients ventilated with positive end-expiratory pressure of 10 cmH2O ( Group C ) had best compliance ( P=0.04 ) and airway resistance values , this , however , without statistical significance . They also had best oxygenation indexes , with statistical difference in all analyzed variables , and lower frequency of hypoxemia ( P=0.03 ) . CONCLUSION Higher levels of positive end-expiratory pressure in immediate postoperative period of coronary artery bypass grafting improved pulmonary compliance values and increased oxygenation indexes , result ing in lower frequency of hypoxemia BACKGROUND Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome . We therefore conducted a trial to determine whether ventilation with lower tidal volumes would improve the clinical outcomes in these patients . METHODS Patients with acute lung injury and the acute respiratory distress syndrome were enrolled in a multicenter , r and omized trial . The trial compared traditional ventilation treatment , which involved an initial tidal volume of 12 ml per kilogram of predicted body weight and an airway pressure measured after a 0.5-second pause at the end of inspiration ( plateau pressure ) of 50 cm of water or less , with ventilation with a lower tidal volume , which involved an initial tidal volume of 6 ml per kilogram of predicted body weight and a plateau pressure of 30 cm of water or less . The primary outcomes were death before a patient was discharged home and was breathing without assistance and the number of days without ventilator use from day 1 to day 28 . RESULTS The trial was stopped after the enrollment of 861 patients because  mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes ( 31.0 percent vs. 39.8 percent , P=0.007 ) , and the number of days without ventilator use during the first 28 days after r and omization was greater in this group ( mean [ + /-SD ] , 12+/-11 vs. 10+/-11 ; P=0.007 ) . The mean tidal volumes on days 1 to 3 were 6.2+/-0.8 and 11.8+/-0.8 ml per kilogram of predicted body weight ( P<0.001 ) , respectively , and the mean plateau pressures were 25+/-6 and 33+/-8 cm of water ( P<0.001 ) , respectively . CONCLUSIONS In patients with acute lung injury and the acute respiratory distress syndrome , mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use Atelectasis is an important cause of impaired gas exchange during general anaesthesia ; it causes pulmonary shunting . We studied the effects of gas composition on the formation of atelectasis and on gas exchange during the induction of general anaesthesia . In 12 adult patients , the lungs were ventilated with 30 % oxygen in nitrogen during anaesthesia induction , and in another 12 , a conventional technique was used ( 100 % oxygen during induction and 40 % oxygen in nitrogen thereafter ) . Extent of atelectasis was estimated by computed tomography and the ventilation-perfusion relation ( VA/Q ) by the multiple inert gas elimination technique . After anaesthesia induction , there was little atelectasis in the 30 % oxygen group ( mean 0.2 [ SD 0.4 ] cm2 ) and a significantly greater amount ( 4.2 [ 5 - 6 ] cm2 ; p < 0.001 ) in the 100 % oxygen group . Patients in the 30 % oxygen group were observed for another 40 min . 6 continued to receive 30 % oxygen ( subgroup A ) and 6 were ventilated with 100 % oxygen ( subgroup B ) . During this time , the amount of atelectasis increased to 1.6 ( 1.6 ) cm2 in subgroup A and to 4.7 ( 4.5 ) cm2 in subgroup B ( p = 0.047 for difference between groups ) . In subgroup A , the shunt ( VA/Q < 0.005 ) increased from 1.6 (2.0)% of cardiac output to 3.2 (2.7)% , but the arterial oxygen tension did not change . In subgroup B , the shunt increased from 2.6 (5.2)% to 9.8 (5.7)% of cardiac output . These results suggest that the composition of inspired gas is important in atelectasis formation during general anaesthesia . Use of a lower oxygen concentration than is now st and ard practice might prevent the early formation of atelectasis Background : Mechanical ventilation with high tidal volumes aggravates lung injury in patients with acute lung injury or acute respiratory distress syndrome . The authors sought to determine the effects of short-term mechanical ventilation on local inflammatory responses in patients without preexisting lung injury . Methods : Patients scheduled to undergo an elective surgical procedure ( lasting ≥5 h ) were r and omly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure ( PEEP ) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP . After induction of anesthesia and 5 h thereafter , bronchoalveolar lavage fluid and /or blood was investigated for polymorphonuclear cell influx , changes in levels of inflammatory markers , and nucleosomes . Results : Mechanical ventilation with lower tidal volumes and PEEP ( n = 21 ) attenuated the increase of pulmonary levels of interleukin (IL)-8 , myeloperoxidase , and elastase as seen with higher tidal volumes and no PEEP ( n = 19 ) . Only for myeloperoxidase , a difference was found between the two ventilation strategies after 5 h of mechanical ventilation ( P < 0.01 ) . Levels of tumor necrosis factor α , 
    Output:
    
agent
***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: Objective To examine whether postoperative mechanical ventilation with lower tidal volumes ( VT ) has protective effects on inflammatory responses induced by  cardiopulmonary bypass ( CPB )  surgery in smokers and nonsmokers . Design and setting Prospect i ve , r and omized , controlled clinical trial in the intensive care unit of a university hospital . Patients and participants We examined 44 patients ( 22 smokers , 22 nonsmokers ) immediately after uncomplicated CPB surgery . Interventions Ventilation was applied for 6 h with either VT of either 6 or 12 ml/kg ideal body weight . Measurements and results The time course of serum tumor necrosis factor ( TNF ) α , interleukin ( IL ) 6 , and IL-8 determined 0 , 2 , 4 , and 6 h after r and omization did not differ significantly between the ventilatory strategies . By contrast , in bronchoalveolar lavage fluids sample d after 6 h only TNF-α levels were significantly higher in the high VT group than the low VT group ( 50±111 pg/ml vs. 1±7 pg/ml ) . IL-6 and IL-8 concentrations did not differ between groups . Subgroup analysis of patients with serum TNF-α level higher than 0 pg/ml after surgery revealed lower TNF-α serum levels during lower VT ventilation . All observed effects were small , independent of patients ’ history of smoking , and were not correlated with duration of ventilation and ICU stay . Conclusions Ventilation with lower VT had no or only minor effect on systemic and pulmonary inflammatory responses in patients with healthy lungs after uncomplicated CPB surgery . Our data do not suggest a clinical benefit of using low VT ventilation in these selected patients BACKGROUND Cardiac surgery-related pulmonary complications include alterations in lung mechanics and anomalies in gas exchange . Higher levels of positive end-expiratory pressure ( PEEP ) have been suggested to benefit cardiac surgical patients . We compared respiratory compliance , arterial oxygenation and time till tracheal extubation in 2 cohorts of patients weaned from mechanical ventilation with different levels of PEEP after elective and uncomplicated coronary artery bypass grafting ( CABG ) . We hypothesized that higher PEEP levels improve pulmonary compliance and gas exchange in the first hours of weaning from mechanical ventilation , but not to shorten time till tracheal extubation . METHODS Secondary retrospective analysis of 2 r and omized controlled trials : in the first trial patients were weaned with PEEP levels of 10 cmH2O for the first 4 hours followed by PEEP levels of 5 cmH2O until tracheal extubation ( high PEEP , HP ) ; and the second trial patients were weaned with PEEP levels of 5 cmH2O during the entire weaning phase ( low PEEP , LP ) . The primary endpoint was pulmonary compliance . Secondary endpoints included arterial oxygenation , duration of mechanical ventilation and postoperative pulmonary complications . RESULTS The analysis included 121 patients ; 60 HP patients and 61 LP patients . Baseline characteristics were similar . Compared to LP patients , HP patients had a better pulmonary compliance , 47.2±14.1 versus 42.7±10.2 ml/cmH2O ( P<0.05 ) , and higher levels of PaO2 , 18.5±6.6 ( 138.75±49.5 ) versus 16.7±5.4 ( 125.25±40.5 ) kPa ( mmHg ) ( P<0.05 ) . Patients in the HP group were less frequent in need of supplementary oxygen after ICU discharge . These differences remained present during the entire weaning phase , even after reduction of PEEP . However , HP patients had a longer time till tracheal extubation , 16.9±6.1 versus 10.5±5.0 hours ( P<0.001 ) . HP patients had longer duration s of postoperative infusion of propofol , 4.9 ( 2.6 - 7.4 ) versus 3.5 ( 1.8 - 5.8 ) hours ( P<0.05 ) . There were no differences in use of inotropes . Cumulative fluid balances were slightly higher in HP patients . CONCLUSION Use of higher PEEP levels after elective uncomplicated CABG improves pulmonary compliance and oxygenation but seems to be associated with a delay in tracheal extubation Introduction Mechanical ventilation ( MV ) with high tidal volumes may induce or aggravate lung injury in critical ill patients . We compared the effects of a protective versus a conventional ventilatory strategy , on systemic and lung production of tumor necrosis factor-α ( TNF-α ) and interleukin-8 ( IL-8 ) in patients without lung disease . Methods Patients without lung disease and su bmi tted to mechanical ventilation admitted to one trauma and one general adult intensive care unit of two different university hospitals were enrolled in a prospect i ve r and omized-control study . Patients were r and omized to receive MV either with tidal volume ( VT ) of 10 to 12 ml/kg predicted body weight ( high VT group ) ( n = 10 ) or with VT of 5 to 7 ml/kg predicted body weight ( low VT group ) ( n = 10 ) with an oxygen inspiratory fraction ( FIO2 ) enough to keep arterial oxygen saturation > 90 % with positive end-expiratory pressure ( PEEP ) of 5 cmH2O during 12 hours after admission to the study . TNF-α and IL-8 concentrations were measured in the serum and in the bronchoalveolar lavage fluid ( BALF ) at admission and after 12 hours of study observation time . Results Twenty patients were enrolled and analyzed . At admission or after 12 hours there were no differences in serum TNF-α and IL-8 between the two groups . While initial analysis did not reveal significant differences , st and ardization against urea of logarithmic transformed data revealed that TNF-α and IL-8 levels in bronchoalveolar lavage ( BAL ) fluid were stable in the low VT group but increased in the high VT group ( P = 0.04 and P = 0.03 ) . After 12 hours , BALF TNF-α ( P = 0.03 ) and BALF IL-8 concentrations ( P = 0.03 ) were higher in the high VT group than in the low VT group . Conclusions The use of lower tidal volumes may limit pulmonary inflammation in mechanically ventilated patients even without lung injury . Trial Registration Clinical Trial registration : OBJECTIVE To compare the effects of different levels of positive end-expiratory pressure on respiratory mechanics and oxygenation indexes in the immediate postoperative period of coronary artery bypass grafting . METHODS R and omized clinical trial in which 136 patients underwent coronary artery bypass grafting between January 2011 and March 2012 were divided into three groups and admitted to mechanical ventilation with different positive end-expiratory pressure levels : Group A , 5 cmH2O ( n=44 ) , Group B , 8 cmH2O ( n=47 ) and Group C , 10 cmH2O ( n=45 ) . Data about respiratory mechanics were obtained from mechanical ventilator monitor and oxygenation indexes from arterial blood gas sample s , collected twenty minutes after intensive care unit admission . Patients with chronic obstructive pulmonary disease and patients su bmi tted to off-pump , emergency or combined operations were not included . For statistical analysis , we used Kruskal-Wallis , G and Chi-square tests , considering results significant when P<0.05 . RESULTS Groups were homogeneous in terms of demographic , clinical and surgical variables . Patients ventilated with positive end-expiratory pressure of 10 cmH2O ( Group C ) had best compliance ( P=0.04 ) and airway resistance values , this , however , without statistical significance . They also had best oxygenation indexes , with statistical difference in all analyzed variables , and lower frequency of hypoxemia ( P=0.03 ) . CONCLUSION Higher levels of positive end-expiratory pressure in immediate postoperative period of coronary artery bypass grafting improved pulmonary compliance values and increased oxygenation indexes , result ing in lower frequency of hypoxemia BACKGROUND Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome . We therefore conducted a trial to determine whether ventilation with lower tidal volumes would improve the clinical outcomes in these patients . METHODS Patients with acute lung injury and the acute respiratory distress syndrome were enrolled in a multicenter , r and omized trial . The trial compared traditional ventilation treatment , which involved an initial tidal volume of 12 ml per kilogram of predicted body weight and an airway pressure measured after a 0.5-second pause at the end of inspiration ( plateau pressure ) of 50 cm of water or less , with ventilation with a lower tidal volume , which involved an initial tidal volume of 6 ml per kilogram of predicted body weight and a plateau pressure of 30 cm of water or less . The primary outcomes were death before a patient was discharged home and was breathing without assistance and the number of days without ventilator use from day 1 to day 28 . RESULTS The trial was stopped after the enrollment of 861 patients because  mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes ( 31.0 percent vs. 39.8 percent , P=0.007 ) , and the number of days without ventilator use during the first 28 days after r and omization was greater in this group ( mean [ + /-SD ] , 12+/-11 vs. 10+/-11 ; P=0.007 ) . The mean tidal volumes on days 1 to 3 were 6.2+/-0.8 and 11.8+/-0.8 ml per kilogram of predicted body weight ( P<0.001 ) , respectively , and the mean plateau pressures were 25+/-6 and 33+/-8 cm of water ( P<0.001 ) , respectively . CONCLUSIONS In patients with acute lung injury and the acute respiratory distress syndrome , mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use Atelectasis is an important cause of impaired gas exchange during general anaesthesia ; it causes pulmonary shunting . We studied the effects of gas composition on the formation of atelectasis and on gas exchange during the induction of general anaesthesia . In 12 adult patients , the lungs were ventilated with 30 % oxygen in nitrogen during anaesthesia induction , and in another 12 , a conventional technique was used ( 100 % oxygen during induction and 40 % oxygen in nitrogen thereafter ) . Extent of atelectasis was estimated by computed tomography and the ventilation-perfusion relation ( VA/Q ) by the multiple inert gas elimination technique . After anaesthesia induction , there was little atelectasis in the 30 % oxygen group ( mean 0.2 [ SD 0.4 ] cm2 ) and a significantly greater amount ( 4.2 [ 5 - 6 ] cm2 ; p < 0.001 ) in the 100 % oxygen group . Patients in the 30 % oxygen group were observed for another 40 min . 6 continued to receive 30 % oxygen ( subgroup A ) and 6 were ventilated with 100 % oxygen ( subgroup B ) . During this time , the amount of atelectasis increased to 1.6 ( 1.6 ) cm2 in subgroup A and to 4.7 ( 4.5 ) cm2 in subgroup B ( p = 0.047 for difference between groups ) . In subgroup A , the shunt ( VA/Q < 0.005 ) increased from 1.6 (2.0)% of cardiac output to 3.2 (2.7)% , but the arterial oxygen tension did not change . In subgroup B , the shunt increased from 2.6 (5.2)% to 9.8 (5.7)% of cardiac output . These results suggest that the composition of inspired gas is important in atelectasis formation during general anaesthesia . Use of a lower oxygen concentration than is now st and ard practice might prevent the early formation of atelectasis Background : Mechanical ventilation with high tidal volumes aggravates lung injury in patients with acute lung injury or acute respiratory distress syndrome . The authors sought to determine the effects of short-term mechanical ventilation on local inflammatory responses in patients without preexisting lung injury . Methods : Patients scheduled to undergo an elective surgical procedure ( lasting ≥5 h ) were r and omly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure ( PEEP ) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP . After induction of anesthesia and 5 h thereafter , bronchoalveolar lavage fluid and /or blood was investigated for polymorphonuclear cell influx , changes in levels of inflammatory markers , and nucleosomes . Results : Mechanical ventilation with lower tidal volumes and PEEP ( n = 21 ) attenuated the increase of pulmonary levels of interleukin (IL)-8 , myeloperoxidase , and elastase as seen with higher tidal volumes and no PEEP ( n = 19 ) . Only for myeloperoxidase , a difference was found between the two ventilation strategies after 5 h of mechanical ventilation ( P < 0.01 ) . Levels of tumor necrosis factor α , 
    Output:
    