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: 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 : The impact of intraoperative ventilation on postoperative pulmonary complications is not defined . The authors aim ed at determining the effectiveness of protective mechanical ventilation during open abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function . Methods : Prospect i ve r and omized , open-label , clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive end-expiratory pressure ( st and ard ventilation strategy ) or tidal volumes of 7 ml/kg ideal body weight , 10 cm H2O positive end-expiratory pressure , and recruitment maneuvers ( protective ventilation strategy ) . Modified Clinical Pulmonary Infection Score , gas exchange , and pulmonary functional tests were measured preoperatively , as well as at days 1 , 3 , and 5 after surgery . Results : Patients ventilated protectively showed better pulmonary functional tests up to day 5 , fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1 , 3 , and 5 ( mmHg ; mean ± SD ) : 77.1 ± 13.0 versus 64.9 ± 11.3 ( P = 0.0006 ) , 80.5 ± 10.1 versus 69.7 ± 9.3 ( P = 0.0002 ) , and 82.1 ± 10.7 versus 78.5 ± 21.7 ( P = 0.44 ) respectively . The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3 . The percentage of patients in hospital at day 28 after surgery was not different between groups ( 7 vs. 15 % respectively , P = 0.42 ) . Conclusion : A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay STUDY OBJECTIVE To determine the effect of positive end-expiratory pressure ( PEEP ) on the respiratory system and on cardiac function . DESIGN Prospect i ve r and omized study . SETTING Operating room . PATIENTS 60 ASA physical status 1 women scheduled for pelvic laparoscopic surgery . INTERVENTIONS Patients were ventilated normally during surgery ; PEEP was modified depending on patient group allocation . Group A was the control group and did not receive PEEP . Group B received PEEP 5 cmH2O and Group C received PEEP 10 cmH2O . MEASUREMENTS Respiratory parameters measured were partial pressure of arterial oxygen ( PaO2 ) , partial pressure of carbon dioxide ( PaCO2 ) , and end-tidal carbon dioxide tension ( ETCO2 ) . Cardiac parameters measured were left ventricular end-diastolic volume index ( LVEDVI ) , ie , ratio of LVEDV/body surface area ( BSA ; [ LVEDVI = end-diastolic volume [EDV]/BSA ) ; left ventricular ( LV ) systolic function , tricuspid annular plane systolic excursion ( TAPSE ) , right ventricular ( RV ) fractional area change ( FAC ) , RV dimensions in the apical 4-chamber view , tracing basal and mid-cavity minor dimensions and longitudinal dimension , cardiac index , systolic pulmonary artery pressure ( PASP ) , and systolic RV pressure ( RVSP ) . Respiratory and cardiac measurements were recorded at T0 ( baseline ) ; T1 ( after anesthesia induction , before pneumoperitoneum induction ) ; at 10 ( T2 ) , 20 ( T3 ) , and 30 ( T4 ) minutes after CO2 insufflation ; and at the end of surgery ( T5 ) . MAIN RESULTS Ventilation with PEEP at 10 cm H2O led to significant improvement in both respiratory and cardiac parameters . A reduction in pulmonary vascular resistance and enhanced washout of expiratory CO2 occurred . Ten and , to a lesser extent , 5 cm H2O of PEEP decreased LV stroke work . CONCLUSIONS Ventilation with PEEP ( up to 10 cm H2O ) recruits the hypoventilated areas of the lungs and reduces cardiac afterload 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 ate 
    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: 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 : The impact of intraoperative ventilation on postoperative pulmonary complications is not defined . The authors aim ed at determining the effectiveness of protective mechanical ventilation during open abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function . Methods : Prospect i ve r and omized , open-label , clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive end-expiratory pressure ( st and ard ventilation strategy ) or tidal volumes of 7 ml/kg ideal body weight , 10 cm H2O positive end-expiratory pressure , and recruitment maneuvers ( protective ventilation strategy ) . Modified Clinical Pulmonary Infection Score , gas exchange , and pulmonary functional tests were measured preoperatively , as well as at days 1 , 3 , and 5 after surgery . Results : Patients ventilated protectively showed better pulmonary functional tests up to day 5 , fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1 , 3 , and 5 ( mmHg ; mean ± SD ) : 77.1 ± 13.0 versus 64.9 ± 11.3 ( P = 0.0006 ) , 80.5 ± 10.1 versus 69.7 ± 9.3 ( P = 0.0002 ) , and 82.1 ± 10.7 versus 78.5 ± 21.7 ( P = 0.44 ) respectively . The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3 . The percentage of patients in hospital at day 28 after surgery was not different between groups ( 7 vs. 15 % respectively , P = 0.42 ) . Conclusion : A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay STUDY OBJECTIVE To determine the effect of positive end-expiratory pressure ( PEEP ) on the respiratory system and on cardiac function . DESIGN Prospect i ve r and omized study . SETTING Operating room . PATIENTS 60 ASA physical status 1 women scheduled for pelvic laparoscopic surgery . INTERVENTIONS Patients were ventilated normally during surgery ; PEEP was modified depending on patient group allocation . Group A was the control group and did not receive PEEP . Group B received PEEP 5 cmH2O and Group C received PEEP 10 cmH2O . MEASUREMENTS Respiratory parameters measured were partial pressure of arterial oxygen ( PaO2 ) , partial pressure of carbon dioxide ( PaCO2 ) , and end-tidal carbon dioxide tension ( ETCO2 ) . Cardiac parameters measured were left ventricular end-diastolic volume index ( LVEDVI ) , ie , ratio of LVEDV/body surface area ( BSA ; [ LVEDVI = end-diastolic volume [EDV]/BSA ) ; left ventricular ( LV ) systolic function , tricuspid annular plane systolic excursion ( TAPSE ) , right ventricular ( RV ) fractional area change ( FAC ) , RV dimensions in the apical 4-chamber view , tracing basal and mid-cavity minor dimensions and longitudinal dimension , cardiac index , systolic pulmonary artery pressure ( PASP ) , and systolic RV pressure ( RVSP ) . Respiratory and cardiac measurements were recorded at T0 ( baseline ) ; T1 ( after anesthesia induction , before pneumoperitoneum induction ) ; at 10 ( T2 ) , 20 ( T3 ) , and 30 ( T4 ) minutes after CO2 insufflation ; and at the end of surgery ( T5 ) . MAIN RESULTS Ventilation with PEEP at 10 cm H2O led to significant improvement in both respiratory and cardiac parameters . A reduction in pulmonary vascular resistance and enhanced washout of expiratory CO2 occurred . Ten and , to a lesser extent , 5 cm H2O of PEEP decreased LV stroke work . CONCLUSIONS Ventilation with PEEP ( up to 10 cm H2O ) recruits the hypoventilated areas of the lungs and reduces cardiac afterload 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 ate 
    Output:
    