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 Background and objective Induction of anaesthesia promotes collapse of dependent lung regions in both obese and nonobese patients . We hypothesized that end-expiratory lung volume ( EELV ) may be more sensitive than oxygenation to evaluate the effects of positive end-expiratory pressure ( PEEP ) after anaesthesia induction . Methods Forty patients ( 20 nonobese patients and 20 obese patients ) were prospect ively studied .  After anaesthesia induction , PEEP was adjusted in a stepwise fashion [ zero end-expiratory pressure ( ZEEP ) , PEEP 5 cmH2O and PEEP 10 cmH2O ] . At each step , we measured EELV , static elastance , gas exchange and dead space . Other than changing PEEP , respiratory setting s were kept constant throughout . Results Anaesthesia induction and ZEEP both lowered EELV by 39 % in nonobese patients and 59 % in obese patients ( both P < 0.05 ) , as well as oxygenation ( P < 0.05 ) . Compared with ZEEP , in nonobese patients , PEEP 5 cmH2O and PEEP 10 cmH2O improved EELV ( + 15 and + 40 % , respectively , P < 0.01 ) and elastance but not oxygenation . In obese patients , PEEP 10 cmH2O also improved EELV ( 49 % vs. ZEEP and 30 % vs. PEEP 5 cmH2O , P < 0.01 ) , elastance and dead-space fraction , with no effect on oxygenation . PEEP-induced changes of EELV correlated with changes of elastance ( r2 = 0.46 , P = 0.003 ) , but not with oxygenation . Conclusion After induction of anaesthesia , mechanical ventilation with ZEEP is associated with a profound reduction in EELV . PEEP improves efficiently EELV and respiratory mechanics , with no major effect on oxygenation . EELV may be a useful indicator to guide PEEP setting in the operating room Objective To assess the impact of the lung recruitment maneuver on circulation following cardiac surgery . Design and setting Prospect i ve r and omized cross-over study at the Departments of Anesthesia and Thoracic Surgery , Copenhagen University Hospital . Patients Ten adult undergoing coronary artery bypass surgery . Interventions Patients were r and omized to two duration s of lung recruitment maneuvers ( 40 cmH2O airway pressure for 10 s and 20 s or vice versa after 5 min ) administered immediately after surgery . Measurements and results Transesophageal echocardiography ( left ventricular short axis view ) , pulse contour cardiac output , and arterial blood pressure were monitored continuously . Systemic and pulmonary arterial blood gases were sample d before and after each lung recruitment maneuver to calculate the intrapulmonary shunt . Left ventricular end-diastolic areas decreased significantly during both the 10-s and the 20-s lung recruitment maneuvers . Cardiac output was 5.6±0.8 l/min at baseline , decreasing by 3.0±1.1 l/min and 3.6±1.2 l/min during lung recruitment maneuvers of 10 and 20 s , respectively . Shunt decreased from 20±5 % to 15±6 % after the first lung recruitment maneuver and from 15±6 % to 12±5 % after the second . Conclusions Lung recruitment maneuvers markedly reduced cardiac output and left ventricular end-diastolic areas in hemodynamically stable patients following cardiac surgery A major cause of impaired gas exchange during general anaesthesia is atelectasis , causing pulmonary shunt . A ' vital capacity ' ( VC ) manoeuvre ( i.e. inflation of the lungs up to 40 cm H2O , maintained for 15 s ) may re-exp and atelectasis and improve oxygenation . However , such a manoeuvre may cause adverse cardiovascular effects . Reducing the time of maximal inflation may improve the margin of safety . The aim of this study was to analyse the change over time in the amount of atelectasis during a VC manoeuvre in 12 anaesthetized adults with healthy lungs .  I.v . anaesthesia with controlled mechanical ventilation ( VT 9 ( SD 1 ) ml kg-1 ) was used . For the VC manoeuvre , the lungs were inflated up to an airway pressure ( Paw ) of 40 cm H2O . This pressure was maintained for 26 s. Atelectasis was assessed by analysis of computed x-ray tomography . The amount of atelectasis , measured at the base of the lungs , was 4.0 ( SD 2.7 ) cm2 after induction of anaesthesia . The decrease in the amount of atelectasis over time during the VC manoeuvre was described by a negative exponential function with a time constant of 2.6 s. At an inspired oxygen concentration of 40 % , PaO2 increased from 17.2 ( 4.0 ) kPa before to 22.2 ( 6.0 ) kPa ( P = 0.013 ) after the VC manoeuvre . Thus in anaesthetized adults undergoing mechanical ventilation with healthy lungs , inflation of the lungs to a Paw of 40 cm H2O , maintained for 7 - 8 s only , may re-exp and all previously collapsed lung tissue , as detected by lung computed tomography , and improve oxygenation . We conclude that the previously proposed time for a VC manoeuvre may be halved in such subjects Background : The authors studied the effects of the beach chair ( BC ) position , 10 cm H2O positive end-expiratory pressure ( PEEP ) , and pneumoperitoneum on respiratory function in morbidly obese patients undergoing laparoscopic gastric b and ing . Methods : The authors studied 20 patients ( body mass index 42 ± 5 kg/m2 ) during the supine and BC positions , before and after pneumoperitoneum was instituted ( 13.6 ± 1.2 mmHg ) .  PEEP was applied during each combination of position and pneumoperitoneum . The authors measured elastance ( E , rs ) of the respiratory system , end-expiratory lung volume ( helium technique ) , and arterial oxygen tension . Pressure – volume curves were also taken ( occlusion technique ) . Patients were paralyzed  during total intravenous anesthesia . Tidal volume ( 10.5 ± 1 ml/kg ideal body weight ) and respiratory rate ( 11 ± 1 breaths/min ) were kept constant throughout . Results : In the supine position , respiratory function was abnormal : E , rs was 21.71 ± 5.26 cm H2O/l , and end-expiratory lung volume was 0.46 ± 0.1 l. Both the BC position and PEEP improved E , rs ( P < 0.01 ) . End-expiratory lung volume almost doubled ( 0.83 ± 0.3 and 0.85 ± 0.3 l , BC and PEEP , respectively ; P < 0.01 vs. supine zero end-expiratory pressure ) , with no evidence of lung recruitment ( 0.04 ± 0.1 l in the supine and 0.07 ± 0.2 in the BC position ) . PEEP was associated with higher airway pressures than the BC position ( 22.1 ± 2.01 vs. 13.8 ± 1.8 cm H2O ; P < 0.01 ) . Pneumoperitoneum further worsened E , rs ( 31.59 ± 6.73 ; P < 0.01 ) and end-expiratory lung volume ( 0.35 ± 0.1 l ; P < 0.01 ) . Changes of lung volume correlated with changes of oxygenation ( linear regression , R2 = 0.524 , P < 0.001 ) so that during pneumoperitoneum , only the combination of the BC position and PEEP improved oxygenation . Conclusions : The BC position and PEEP counteracted the major derangements of respiratory function produced by anesthesia and paralysis . During pneumoperitoneum , only the combination of the two maneuvers improved oxygenation Introduction Alveolar derecruitment may occur during low tidal volume ventilation and may be prevented by recruitment maneuvers ( RMs ) . The aim of this study was to compare two RMs in acute respiratory distress syndrome ( ARDS ) patients . Methods Nineteen patients with ARDS and protective ventilation were included in a r and omized crossover study . Both RMs were applied in each patient , beginning with either continuous positive airway pressure ( CPAP ) with 40 cm H2O for 40 seconds or extended sigh ( eSigh ) consisting of a positive end-expiratory pressure maintained at 10 cm H2O above the lower inflection point of the pressure-volume curve for 15 minutes . Recruited volume , arterial partial pressure of oxygen/fraction of inspired oxygen ( PaO2/FiO2 ) , and hemodynamic parameters were recorded before ( baseline ) and 5 and 60 minutes after RM . All patients had a lung computed tomography ( CT ) scan before study inclusion . Results Before RM , PaO2/FiO2 was 151 ± 61 mm Hg . Both RMs increased oxygenation , but the increase in PaO2/FiO2 was significantly higher with eSigh than CPAP at 5 minutes ( 73 % ± 25 % versus 44 % ± 28 % ; P < 0.001 ) and 60 minutes ( 68 % ± 23 % versus 35 % ± 22 % ; P < 0.001 ) . Only eSigh significantly increased recruited volume at 5 and 60 minutes ( 21 % ± 22 % and 21 % ± 25 % ; P = 0.0003 and P = 0.001 , respectively ) . The only difference between responders and non-responders was CT lung morphology . Eleven patients were considered as recruiters with eSigh ( 10 with diffuse loss of aeration ) and 6 with CPAP ( 5 with diffuse loss of aeration ) . During CPAP , 2 patients needed interruption of RM due to a drop in systolic arterial pressure . Conclusion Both RMs effectively increase oxygenation , but CPAP failed to increase recruited volume . When the lung is recruited with an eSigh adapted for each patient , alveolar recruitment and oxygenation are superior to those observed with CPAP UNLABELLED BACKGROUND AND METHDS : Alveolar recruitment maneuver ( ARM ) is indicated in the treatment of intraoperative atelectasis . The objective of the present study was to compare two techniques of ARM using the response of the PaO2/FiO2 ratio and [ PaO2 + PaCO2 ] in patients with grade III obesity . METHODS This was an open prospect i ve study with adult patients 
    Output:
    
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***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 Background and objective Induction of anaesthesia promotes collapse of dependent lung regions in both obese and nonobese patients . We hypothesized that end-expiratory lung volume ( EELV ) may be more sensitive than oxygenation to evaluate the effects of positive end-expiratory pressure ( PEEP ) after anaesthesia induction . Methods Forty patients ( 20 nonobese patients and 20 obese patients ) were prospect ively studied .  After anaesthesia induction , PEEP was adjusted in a stepwise fashion [ zero end-expiratory pressure ( ZEEP ) , PEEP 5 cmH2O and PEEP 10 cmH2O ] . At each step , we measured EELV , static elastance , gas exchange and dead space . Other than changing PEEP , respiratory setting s were kept constant throughout . Results Anaesthesia induction and ZEEP both lowered EELV by 39 % in nonobese patients and 59 % in obese patients ( both P < 0.05 ) , as well as oxygenation ( P < 0.05 ) . Compared with ZEEP , in nonobese patients , PEEP 5 cmH2O and PEEP 10 cmH2O improved EELV ( + 15 and + 40 % , respectively , P < 0.01 ) and elastance but not oxygenation . In obese patients , PEEP 10 cmH2O also improved EELV ( 49 % vs. ZEEP and 30 % vs. PEEP 5 cmH2O , P < 0.01 ) , elastance and dead-space fraction , with no effect on oxygenation . PEEP-induced changes of EELV correlated with changes of elastance ( r2 = 0.46 , P = 0.003 ) , but not with oxygenation . Conclusion After induction of anaesthesia , mechanical ventilation with ZEEP is associated with a profound reduction in EELV . PEEP improves efficiently EELV and respiratory mechanics , with no major effect on oxygenation . EELV may be a useful indicator to guide PEEP setting in the operating room Objective To assess the impact of the lung recruitment maneuver on circulation following cardiac surgery . Design and setting Prospect i ve r and omized cross-over study at the Departments of Anesthesia and Thoracic Surgery , Copenhagen University Hospital . Patients Ten adult undergoing coronary artery bypass surgery . Interventions Patients were r and omized to two duration s of lung recruitment maneuvers ( 40 cmH2O airway pressure for 10 s and 20 s or vice versa after 5 min ) administered immediately after surgery . Measurements and results Transesophageal echocardiography ( left ventricular short axis view ) , pulse contour cardiac output , and arterial blood pressure were monitored continuously . Systemic and pulmonary arterial blood gases were sample d before and after each lung recruitment maneuver to calculate the intrapulmonary shunt . Left ventricular end-diastolic areas decreased significantly during both the 10-s and the 20-s lung recruitment maneuvers . Cardiac output was 5.6±0.8 l/min at baseline , decreasing by 3.0±1.1 l/min and 3.6±1.2 l/min during lung recruitment maneuvers of 10 and 20 s , respectively . Shunt decreased from 20±5 % to 15±6 % after the first lung recruitment maneuver and from 15±6 % to 12±5 % after the second . Conclusions Lung recruitment maneuvers markedly reduced cardiac output and left ventricular end-diastolic areas in hemodynamically stable patients following cardiac surgery A major cause of impaired gas exchange during general anaesthesia is atelectasis , causing pulmonary shunt . A ' vital capacity ' ( VC ) manoeuvre ( i.e. inflation of the lungs up to 40 cm H2O , maintained for 15 s ) may re-exp and atelectasis and improve oxygenation . However , such a manoeuvre may cause adverse cardiovascular effects . Reducing the time of maximal inflation may improve the margin of safety . The aim of this study was to analyse the change over time in the amount of atelectasis during a VC manoeuvre in 12 anaesthetized adults with healthy lungs .  I.v . anaesthesia with controlled mechanical ventilation ( VT 9 ( SD 1 ) ml kg-1 ) was used . For the VC manoeuvre , the lungs were inflated up to an airway pressure ( Paw ) of 40 cm H2O . This pressure was maintained for 26 s. Atelectasis was assessed by analysis of computed x-ray tomography . The amount of atelectasis , measured at the base of the lungs , was 4.0 ( SD 2.7 ) cm2 after induction of anaesthesia . The decrease in the amount of atelectasis over time during the VC manoeuvre was described by a negative exponential function with a time constant of 2.6 s. At an inspired oxygen concentration of 40 % , PaO2 increased from 17.2 ( 4.0 ) kPa before to 22.2 ( 6.0 ) kPa ( P = 0.013 ) after the VC manoeuvre . Thus in anaesthetized adults undergoing mechanical ventilation with healthy lungs , inflation of the lungs to a Paw of 40 cm H2O , maintained for 7 - 8 s only , may re-exp and all previously collapsed lung tissue , as detected by lung computed tomography , and improve oxygenation . We conclude that the previously proposed time for a VC manoeuvre may be halved in such subjects Background : The authors studied the effects of the beach chair ( BC ) position , 10 cm H2O positive end-expiratory pressure ( PEEP ) , and pneumoperitoneum on respiratory function in morbidly obese patients undergoing laparoscopic gastric b and ing . Methods : The authors studied 20 patients ( body mass index 42 ± 5 kg/m2 ) during the supine and BC positions , before and after pneumoperitoneum was instituted ( 13.6 ± 1.2 mmHg ) .  PEEP was applied during each combination of position and pneumoperitoneum . The authors measured elastance ( E , rs ) of the respiratory system , end-expiratory lung volume ( helium technique ) , and arterial oxygen tension . Pressure – volume curves were also taken ( occlusion technique ) . Patients were paralyzed  during total intravenous anesthesia . Tidal volume ( 10.5 ± 1 ml/kg ideal body weight ) and respiratory rate ( 11 ± 1 breaths/min ) were kept constant throughout . Results : In the supine position , respiratory function was abnormal : E , rs was 21.71 ± 5.26 cm H2O/l , and end-expiratory lung volume was 0.46 ± 0.1 l. Both the BC position and PEEP improved E , rs ( P < 0.01 ) . End-expiratory lung volume almost doubled ( 0.83 ± 0.3 and 0.85 ± 0.3 l , BC and PEEP , respectively ; P < 0.01 vs. supine zero end-expiratory pressure ) , with no evidence of lung recruitment ( 0.04 ± 0.1 l in the supine and 0.07 ± 0.2 in the BC position ) . PEEP was associated with higher airway pressures than the BC position ( 22.1 ± 2.01 vs. 13.8 ± 1.8 cm H2O ; P < 0.01 ) . Pneumoperitoneum further worsened E , rs ( 31.59 ± 6.73 ; P < 0.01 ) and end-expiratory lung volume ( 0.35 ± 0.1 l ; P < 0.01 ) . Changes of lung volume correlated with changes of oxygenation ( linear regression , R2 = 0.524 , P < 0.001 ) so that during pneumoperitoneum , only the combination of the BC position and PEEP improved oxygenation . Conclusions : The BC position and PEEP counteracted the major derangements of respiratory function produced by anesthesia and paralysis . During pneumoperitoneum , only the combination of the two maneuvers improved oxygenation Introduction Alveolar derecruitment may occur during low tidal volume ventilation and may be prevented by recruitment maneuvers ( RMs ) . The aim of this study was to compare two RMs in acute respiratory distress syndrome ( ARDS ) patients . Methods Nineteen patients with ARDS and protective ventilation were included in a r and omized crossover study . Both RMs were applied in each patient , beginning with either continuous positive airway pressure ( CPAP ) with 40 cm H2O for 40 seconds or extended sigh ( eSigh ) consisting of a positive end-expiratory pressure maintained at 10 cm H2O above the lower inflection point of the pressure-volume curve for 15 minutes . Recruited volume , arterial partial pressure of oxygen/fraction of inspired oxygen ( PaO2/FiO2 ) , and hemodynamic parameters were recorded before ( baseline ) and 5 and 60 minutes after RM . All patients had a lung computed tomography ( CT ) scan before study inclusion . Results Before RM , PaO2/FiO2 was 151 ± 61 mm Hg . Both RMs increased oxygenation , but the increase in PaO2/FiO2 was significantly higher with eSigh than CPAP at 5 minutes ( 73 % ± 25 % versus 44 % ± 28 % ; P < 0.001 ) and 60 minutes ( 68 % ± 23 % versus 35 % ± 22 % ; P < 0.001 ) . Only eSigh significantly increased recruited volume at 5 and 60 minutes ( 21 % ± 22 % and 21 % ± 25 % ; P = 0.0003 and P = 0.001 , respectively ) . The only difference between responders and non-responders was CT lung morphology . Eleven patients were considered as recruiters with eSigh ( 10 with diffuse loss of aeration ) and 6 with CPAP ( 5 with diffuse loss of aeration ) . During CPAP , 2 patients needed interruption of RM due to a drop in systolic arterial pressure . Conclusion Both RMs effectively increase oxygenation , but CPAP failed to increase recruited volume . When the lung is recruited with an eSigh adapted for each patient , alveolar recruitment and oxygenation are superior to those observed with CPAP UNLABELLED BACKGROUND AND METHDS : Alveolar recruitment maneuver ( ARM ) is indicated in the treatment of intraoperative atelectasis . The objective of the present study was to compare two techniques of ARM using the response of the PaO2/FiO2 ratio and [ PaO2 + PaCO2 ] in patients with grade III obesity . METHODS This was an open prospect i ve study with adult patients 
    Output:
    