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: The prediction of postoperative pulmonary complications is an underinvestigated field . We conducted a prospect i ve cohort study ( with postoperative pulmonary complications ascertained by an investigator blinded to perioperative variables ) to determine the risk factors for pulmonary complications after elective nonthoracic surgery . Of 1,055 consecutive patients attending the Pre-Admission Clinic of a university hospital ( mean age 55 years , 50 % men , 15 % with history of obstructive airways disease ) , 28 ( 2.7 % ) suffered a postoperative pulmonary complication within 7 days of surgery : 13 patients developed respiratory failure requiring ventilatory support , 9 pneumonia , 5 atelectasis requiring bronchoscopic intervention , and 1 pneumothorax requiring intervention . Mean lengths of stay were substantially prolonged for those patients who developed pulmonary complications within 7 days of surgery : 27.9 days versus 4.5 days , p = 0.006 . Eight variables were statistically significantly associated with pulmonary complications on bivariate analyses . Multivariate analyses revealed that four were independently associated with increased risk of pulmonary complications : age ( odds ratio [ OR ] 5.9 for age > /= 65 years , p < 0.001 ) , positive cough test ( OR 3.8 , P = 0.01 ) , perioperative nasogastric tube ( OR 7.7 , p < 0.001 ) , and duration of anesthesia ( OR 3.3 for operations lasting at least 2.5 hours , p = 0.008 ) . Thus , several perioperative factors predict an increased risk for pulmonary complications after elective nonthoracic surgery BACKGROUND : Atelectasis occurs regularly after induction of general anesthesia , persists postoperatively , and may contribute to significant postoperative morbidity and additional health care costs . Laparoscopic surgery has been reported to be associated with an increased incidence of postoperative atelectasis . It has been shown that during general anesthesia , obese patients have a greater risk of atelectasis than nonobese patients . Preventing atelectasis is important for all patients but is especially important when caring for obese patients . METHODS : We r and omly allocated 66 adult obese patients with a body mass index between 30 and 50 kg/m2 scheduled to undergo laparoscopic bariatric surgery  into 3 groups . According to the recruitment maneuver used , the zero end-expiratory pressure ( ZEEP ) group ( n = 22 ) received the vital capacity maneuver ( VCM ) maintained for 7–8 s applied immediately after intubation plus ZEEP ; the positive end-expiratory pressure ( PEEP ) 5 group ( n = 22 ) received the VCM maintained for 7–8 s applied immediately after intubation plus 5 cm H2O of PEEP ; and the PEEP 10 group ( n = 22 ) received the VCM maintained for 7–8 s applied immediately after intubation plus 10 cm H2O of PEEP . All other variables ( e.g. , anesthetic and surgical techniques ) were the same for all patients . Heart rate , noninvasive mean arterial blood pressure , arterial oxygen saturation , and alveolar-arterial Pao2 gradient ( A-a Pao2 ) were measured intraoperatively and postoperatively in the postanesthesia care unit ( PACU ) . Length of stay in the PACU and the use of a nonrebreathing O2 mask ( 100 % Fio2 ) or reintubation were also recorded . A computed tomographic scan of the chest was performed preoperatively and postoperatively after discharge from the PACU to evaluate lung atelectasis . RESULTS : Patients in the PEEP 10 group had better oxygenation both intraoperatively and postoperatively in the PACU , lower atelectasis score on chest computed tomographic scan , and less postoperative pulmonary complications than the ZEEP and PEEP 5 groups . There was no evidence of barotrauma in any patient in the 3 study groups . CONCLUSIONS : Intraoperative alveolar recruitment with a VCM followed by PEEP 10 cm H2O is effective at preventing lung atelectasis and is associated with better oxygenation , shorter PACU stay , and fewer pulmonary complications in the postoperative period in obese patients undergoing laparoscopic bariatric surgery Atelectasis caused by general anesthesia is increased in morbidly obese patients . We have shown that application of positive end-expiratory pressure ( PEEP ) during the induction of anesthesia prevents atelectasis formation in nonobese patients . We therefore studied the efficacy of PEEP in morbidly obese patients to prevent atelectasis .  Twenty-three adult morbidly obese patients ( body mass index > 35 kg/m2 ) were r and omly assigned to one of two groups . In the PEEP group , patients breathed 100 % oxygen ( 5 min ) with a continuous positive airway pressure of 10 cm H2O and , after the induction , mechanical ventilation via a face mask with a PEEP of 10 cm H2O . In the control group , the same induction was applied but without continuous positive airway pressure or PEEP .  Atelectasis , determined by computed tomography , and blood gas analysis were measured twice : before the induction and directly after intubation . After endotracheal intubation , patients of the control group showed an increase in the amount of atelectasis , which was much larger than in the PEEP group ( 10.4 % ± 4.8 % in control group versus 1.7 % ± 1.3 % in PEEP group ; P<0.001 ) . After intubation with a fraction of inspired oxygen of 1.0 , Pao2 was significantly higher in the PEEP group compared with the control group ( 457 ± 130 mm Hg versus 315 ± 100 mm Hg , respectively ; P = 0.035 ) We conclude that in morbidly obese patients  , atelectasis formation is largely prevented by PEEP applied during the anesthetic induction and is associated with a better oxygenation CONTEXT The need for lung protection is universally accepted , but the optimal level of positive end-expiratory pressure ( PEEP ) in patients with acute lung injury ( ALI ) or acute respiratory distress syndrome remains debated . OBJECTIVE To compare the effect on outcome of a strategy for setting PEEP aim ed at increasing alveolar recruitment while limiting hyperinflation to one aim ed at minimizing alveolar distension in patients with ALI . DESIGN , SETTING , AND PATIENTS A multicenter r and omized controlled trial of 767 adults ( mean [ SD ] age , 59.9 [ 15.4 ] years ) with ALI conducted in 37 intensive care units in France from September 2002 to December 2005 . INTERVENTION Tidal volume was set at 6 mL/kg of predicted body weight in both strategies . Patients were r and omly assigned to a moderate PEEP strategy ( 5 - 9 cm H(2)O ) ( minimal distension strategy ; n = 382 ) or to a level of PEEP set to reach a plateau pressure of 28 to 30 cm H(2)O ( increased recruitment strategy ; n = 385 ) . MAIN OUTCOME MEASURES The primary end point was mortality at 28 days . Secondary end points were hospital mortality at 60 days , ventilator-free days , and organ failure-free days at 28 days . RESULTS The 28-day mortality rate in the minimal distension group was 31.2 % ( n = 119 ) vs 27.8 % ( n = 107 ) in the increased recruitment group ( relative risk , 1.12 [ 95 % confidence interval , 0.90 - 1.40 ] ; P = .31 ) . The hospital mortality rate in the minimal distension group was 39.0 % ( n = 149 ) vs 35.4 % ( n = 136 ) in the increased recruitment group ( relative risk , 1.10 [ 95 % confidence interval , 0.92 - 1.32 ] ; P = .30 ) . The increased recruitment group compared with the minimal distension group had a higher median number of ventilator-free days ( 7 [ interquartile range { IQR } , 0 - 19 ] vs 3 [ IQR , 0 - 17 ] ; P = .04 ) and organ failure-free days ( 6 [ IQR , 0 - 18 ] vs 2 [ IQR , 0 - 16 ] ; P = .04 ) . This strategy also was associated with higher compliance values , better oxygenation , less use of adjunctive therapies , and larger fluid requirements . CONCLUSIONS A strategy for setting PEEP aim ed at increasing alveolar recruitment while limiting hyperinflation did not significantly reduce mortality . However , it did improve lung function and reduced the duration of mechanical ventilation and the duration of organ failure . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00188058 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 , IL-1α , IL-1β , IL-6 , macrophage inflammatory protein 1α , and macrophage inflammatory protein 1β in the bronchoalveolar lavage fluid were not affected by mechanical ventilation . Plasma levels of IL-6 and IL-8 increased with mechanical ventilation , but there were no differences between the two ventilation groups . Conclusion : The use of lower tidal volumes and PEEP may limit pulmonary inflammation in mechanically ventilated patients without preexisting lung injury . The specific contribution of both lower tidal volumes and PEEP on the protective effects of the lung should be further investigated General anesthesia promotes atelectasis formation , which is augmented by administration of large oxygen concentrations . We studied the efficacy of positive end-expiratory pressure ( PEEP ) application during the induction of general anesthesia ( fraction of inspired oxygen [ Fio2 ] 1.0 ) to prevent atelectasis . Sixteen adult patients were r and omly assigned to one of two groups . Both groups breathed 100 % O2 for 5 min and , after a general anesthesia induction , mechanical ventilation via a face mask with a Fio2 of 1.0 for another 5 min before endotracheal intubation . Patients in the first group ( PEEP group ) had continuous positive airway pressure ( CPAP ) ( 6 cm H2O ) and mechanical ventilation via a face mask with a PEEP of 6 cm H2O . No CPAP or PEEP was applied in the control group . Atelectasis , determined by computed radiograph tomography , and analysis of blood gases were measured twice : before the beginning of anesthesia and directly after the intubation . There was no difference between groups before the anesthesia induction . After endotracheal intubation , patients in the control group showed an increase of the mean area of atelectasis from 0.8 % ± 0.9 % to 4.1 % ± 2.0 % ( P = 0.0002 ) , whereas the patients of the PEEP group showed no change ( 0.5 % ± 0.6 % versus 0.4 % ± 0.7 % ) . After the intubation with a Fio2 of 1.0 , Pao2 was significantly higher in the PEEP group than in the control ( 591 ± 54 mm Hg versus 457 ± 99 mm Hg ; P = 0.005 ) . Atelectasis formation is prevented by application of PEEP during the anesthesia induction despite the use of large oxygen concentrations , result ing in improved oxygenation Background Mechanical ventilation with high tidal volumes ( VT ) in contrast to mechanical ventilation with low VT has been shown to increase plasma levels of proinflammatory and antiinflammatory mediators in patients with acute lung injury . The authors hypothesized that , in patients without previous lung injury , a conventional potentially injurious ventilatory strategy with high VT and zero end-expiratory pressure ( ZEEP ) will not cause a cytokine release into systemic circulation . Methods A total of 39 patients with American Society of Anesthesiologists physical status I – II and without signs of systemic infection scheduled for elective surgery with general anesthesia were r and omized to receive mechanical ventilation with either ( 1 ) VT = 15 ml/kg ideal body weight on ZEEP , ( 2 ) VT = 6 ml/kg ideal body weight on ZEEP , or ( 3 ) VT = 6 ml/kg ideal body weight on positive end-exp 
    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: The prediction of postoperative pulmonary complications is an underinvestigated field . We conducted a prospect i ve cohort study ( with postoperative pulmonary complications ascertained by an investigator blinded to perioperative variables ) to determine the risk factors for pulmonary complications after elective nonthoracic surgery . Of 1,055 consecutive patients attending the Pre-Admission Clinic of a university hospital ( mean age 55 years , 50 % men , 15 % with history of obstructive airways disease ) , 28 ( 2.7 % ) suffered a postoperative pulmonary complication within 7 days of surgery : 13 patients developed respiratory failure requiring ventilatory support , 9 pneumonia , 5 atelectasis requiring bronchoscopic intervention , and 1 pneumothorax requiring intervention . Mean lengths of stay were substantially prolonged for those patients who developed pulmonary complications within 7 days of surgery : 27.9 days versus 4.5 days , p = 0.006 . Eight variables were statistically significantly associated with pulmonary complications on bivariate analyses . Multivariate analyses revealed that four were independently associated with increased risk of pulmonary complications : age ( odds ratio [ OR ] 5.9 for age > /= 65 years , p < 0.001 ) , positive cough test ( OR 3.8 , P = 0.01 ) , perioperative nasogastric tube ( OR 7.7 , p < 0.001 ) , and duration of anesthesia ( OR 3.3 for operations lasting at least 2.5 hours , p = 0.008 ) . Thus , several perioperative factors predict an increased risk for pulmonary complications after elective nonthoracic surgery BACKGROUND : Atelectasis occurs regularly after induction of general anesthesia , persists postoperatively , and may contribute to significant postoperative morbidity and additional health care costs . Laparoscopic surgery has been reported to be associated with an increased incidence of postoperative atelectasis . It has been shown that during general anesthesia , obese patients have a greater risk of atelectasis than nonobese patients . Preventing atelectasis is important for all patients but is especially important when caring for obese patients . METHODS : We r and omly allocated 66 adult obese patients with a body mass index between 30 and 50 kg/m2 scheduled to undergo laparoscopic bariatric surgery  into 3 groups . According to the recruitment maneuver used , the zero end-expiratory pressure ( ZEEP ) group ( n = 22 ) received the vital capacity maneuver ( VCM ) maintained for 7–8 s applied immediately after intubation plus ZEEP ; the positive end-expiratory pressure ( PEEP ) 5 group ( n = 22 ) received the VCM maintained for 7–8 s applied immediately after intubation plus 5 cm H2O of PEEP ; and the PEEP 10 group ( n = 22 ) received the VCM maintained for 7–8 s applied immediately after intubation plus 10 cm H2O of PEEP . All other variables ( e.g. , anesthetic and surgical techniques ) were the same for all patients . Heart rate , noninvasive mean arterial blood pressure , arterial oxygen saturation , and alveolar-arterial Pao2 gradient ( A-a Pao2 ) were measured intraoperatively and postoperatively in the postanesthesia care unit ( PACU ) . Length of stay in the PACU and the use of a nonrebreathing O2 mask ( 100 % Fio2 ) or reintubation were also recorded . A computed tomographic scan of the chest was performed preoperatively and postoperatively after discharge from the PACU to evaluate lung atelectasis . RESULTS : Patients in the PEEP 10 group had better oxygenation both intraoperatively and postoperatively in the PACU , lower atelectasis score on chest computed tomographic scan , and less postoperative pulmonary complications than the ZEEP and PEEP 5 groups . There was no evidence of barotrauma in any patient in the 3 study groups . CONCLUSIONS : Intraoperative alveolar recruitment with a VCM followed by PEEP 10 cm H2O is effective at preventing lung atelectasis and is associated with better oxygenation , shorter PACU stay , and fewer pulmonary complications in the postoperative period in obese patients undergoing laparoscopic bariatric surgery Atelectasis caused by general anesthesia is increased in morbidly obese patients . We have shown that application of positive end-expiratory pressure ( PEEP ) during the induction of anesthesia prevents atelectasis formation in nonobese patients . We therefore studied the efficacy of PEEP in morbidly obese patients to prevent atelectasis .  Twenty-three adult morbidly obese patients ( body mass index > 35 kg/m2 ) were r and omly assigned to one of two groups . In the PEEP group , patients breathed 100 % oxygen ( 5 min ) with a continuous positive airway pressure of 10 cm H2O and , after the induction , mechanical ventilation via a face mask with a PEEP of 10 cm H2O . In the control group , the same induction was applied but without continuous positive airway pressure or PEEP .  Atelectasis , determined by computed tomography , and blood gas analysis were measured twice : before the induction and directly after intubation . After endotracheal intubation , patients of the control group showed an increase in the amount of atelectasis , which was much larger than in the PEEP group ( 10.4 % ± 4.8 % in control group versus 1.7 % ± 1.3 % in PEEP group ; P<0.001 ) . After intubation with a fraction of inspired oxygen of 1.0 , Pao2 was significantly higher in the PEEP group compared with the control group ( 457 ± 130 mm Hg versus 315 ± 100 mm Hg , respectively ; P = 0.035 ) We conclude that in morbidly obese patients  , atelectasis formation is largely prevented by PEEP applied during the anesthetic induction and is associated with a better oxygenation CONTEXT The need for lung protection is universally accepted , but the optimal level of positive end-expiratory pressure ( PEEP ) in patients with acute lung injury ( ALI ) or acute respiratory distress syndrome remains debated . OBJECTIVE To compare the effect on outcome of a strategy for setting PEEP aim ed at increasing alveolar recruitment while limiting hyperinflation to one aim ed at minimizing alveolar distension in patients with ALI . DESIGN , SETTING , AND PATIENTS A multicenter r and omized controlled trial of 767 adults ( mean [ SD ] age , 59.9 [ 15.4 ] years ) with ALI conducted in 37 intensive care units in France from September 2002 to December 2005 . INTERVENTION Tidal volume was set at 6 mL/kg of predicted body weight in both strategies . Patients were r and omly assigned to a moderate PEEP strategy ( 5 - 9 cm H(2)O ) ( minimal distension strategy ; n = 382 ) or to a level of PEEP set to reach a plateau pressure of 28 to 30 cm H(2)O ( increased recruitment strategy ; n = 385 ) . MAIN OUTCOME MEASURES The primary end point was mortality at 28 days . Secondary end points were hospital mortality at 60 days , ventilator-free days , and organ failure-free days at 28 days . RESULTS The 28-day mortality rate in the minimal distension group was 31.2 % ( n = 119 ) vs 27.8 % ( n = 107 ) in the increased recruitment group ( relative risk , 1.12 [ 95 % confidence interval , 0.90 - 1.40 ] ; P = .31 ) . The hospital mortality rate in the minimal distension group was 39.0 % ( n = 149 ) vs 35.4 % ( n = 136 ) in the increased recruitment group ( relative risk , 1.10 [ 95 % confidence interval , 0.92 - 1.32 ] ; P = .30 ) . The increased recruitment group compared with the minimal distension group had a higher median number of ventilator-free days ( 7 [ interquartile range { IQR } , 0 - 19 ] vs 3 [ IQR , 0 - 17 ] ; P = .04 ) and organ failure-free days ( 6 [ IQR , 0 - 18 ] vs 2 [ IQR , 0 - 16 ] ; P = .04 ) . This strategy also was associated with higher compliance values , better oxygenation , less use of adjunctive therapies , and larger fluid requirements . CONCLUSIONS A strategy for setting PEEP aim ed at increasing alveolar recruitment while limiting hyperinflation did not significantly reduce mortality . However , it did improve lung function and reduced the duration of mechanical ventilation and the duration of organ failure . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00188058 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 , IL-1α , IL-1β , IL-6 , macrophage inflammatory protein 1α , and macrophage inflammatory protein 1β in the bronchoalveolar lavage fluid were not affected by mechanical ventilation . Plasma levels of IL-6 and IL-8 increased with mechanical ventilation , but there were no differences between the two ventilation groups . Conclusion : The use of lower tidal volumes and PEEP may limit pulmonary inflammation in mechanically ventilated patients without preexisting lung injury . The specific contribution of both lower tidal volumes and PEEP on the protective effects of the lung should be further investigated General anesthesia promotes atelectasis formation , which is augmented by administration of large oxygen concentrations . We studied the efficacy of positive end-expiratory pressure ( PEEP ) application during the induction of general anesthesia ( fraction of inspired oxygen [ Fio2 ] 1.0 ) to prevent atelectasis . Sixteen adult patients were r and omly assigned to one of two groups . Both groups breathed 100 % O2 for 5 min and , after a general anesthesia induction , mechanical ventilation via a face mask with a Fio2 of 1.0 for another 5 min before endotracheal intubation . Patients in the first group ( PEEP group ) had continuous positive airway pressure ( CPAP ) ( 6 cm H2O ) and mechanical ventilation via a face mask with a PEEP of 6 cm H2O . No CPAP or PEEP was applied in the control group . Atelectasis , determined by computed radiograph tomography , and analysis of blood gases were measured twice : before the beginning of anesthesia and directly after the intubation . There was no difference between groups before the anesthesia induction . After endotracheal intubation , patients in the control group showed an increase of the mean area of atelectasis from 0.8 % ± 0.9 % to 4.1 % ± 2.0 % ( P = 0.0002 ) , whereas the patients of the PEEP group showed no change ( 0.5 % ± 0.6 % versus 0.4 % ± 0.7 % ) . After the intubation with a Fio2 of 1.0 , Pao2 was significantly higher in the PEEP group than in the control ( 591 ± 54 mm Hg versus 457 ± 99 mm Hg ; P = 0.005 ) . Atelectasis formation is prevented by application of PEEP during the anesthesia induction despite the use of large oxygen concentrations , result ing in improved oxygenation Background Mechanical ventilation with high tidal volumes ( VT ) in contrast to mechanical ventilation with low VT has been shown to increase plasma levels of proinflammatory and antiinflammatory mediators in patients with acute lung injury . The authors hypothesized that , in patients without previous lung injury , a conventional potentially injurious ventilatory strategy with high VT and zero end-expiratory pressure ( ZEEP ) will not cause a cytokine release into systemic circulation . Methods A total of 39 patients with American Society of Anesthesiologists physical status I – II and without signs of systemic infection scheduled for elective surgery with general anesthesia were r and omized to receive mechanical ventilation with either ( 1 ) VT = 15 ml/kg ideal body weight on ZEEP , ( 2 ) VT = 6 ml/kg ideal body weight on ZEEP , or ( 3 ) VT = 6 ml/kg ideal body weight on positive end-exp 
    Output:
    