Mechanical ventilation strategies and inflammatory responses to cardiac surgery: a prospective randomized clinical trial Positive end-expiratory pressure following coronary artery bypass grafting. Mechanical ventilation with high tidal volume induces inflammation in patients without lung disease Effects of different PEEP levels on respiratory mechanics and oxygenation after coronary artery bypass grafting. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. Prevention of atelectasis during general anaesthesia Mechanical Ventilation with Lower Tidal Volumes and Positive End-expiratory Pressure Prevents Pulmonary Inflammation in Patients without Preexisting Lung Injury Ventilation with lower tidal volumes as compared with conventional tidal volumes for patients without acute lung injury: a preventive randomized controlled trial Increased apparatus dead space and tidal volume increase blood concentrations of oxygen and sevoflurane in overweight patients: a randomised controlled clinical study Effects of cyclic opening and closing at low- and high-volume ventilation on bronchoalveolar lavage cytokines* Effects of four intraoperative ventilatory strategies on respiratory compliance and gas exchange during laparoscopic gastric banding in obese patients. Protective ventilation attenuates postoperative pulmonary dysfunction in patients undergoing cardiopulmonary bypass. Are low tidal volumes safe? The routine use of positive end-expiratory pressure after open heart surgery. Respiratory mechanics in brain-damaged patients Biological Impact of Transpulmonary Driving Pressure in Experimental Acute Respiratory Distress Syndrome Mechanical ventilation affects inflammatory mediators in patients undergoing cardiopulmonary bypass for cardiac surgery: a randomized clinical trial. Effects of lung recruitment maneuver and positiveend‐expiratory pressure on lung volume, respiratory mechanics and alveolar gas mixing in patients ventilated after cardiac surgery The Effects of Body Mass on Lung Volumes, Respiratory Mechanics, and Gas Exchange During General Anesthesia Mechanical Ventilation with Lower Tidal Volumes and Positive End-expiratory Pressure Prevents Alveolar Coagulation in Patients without Lung Injury
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 , 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 Introduction Recent cohort studies have identified the use of large tidal volumes as a major risk factor for development of lung injury in mechanically ventilated patients without acute lung injury ( ALI ) . We compared the effect of conventional with lower tidal volumes on pulmonary inflammation and development of lung injury in critically ill patients without ALI at the onset of mechanical ventilation . Methods We performed a r and omized controlled nonblinded preventive trial comparing mechanical ventilation with tidal volumes of 10 ml versus 6 ml per kilogram of predicted body weight in critically ill patients without ALI at the onset of mechanical ventilation . The primary end point was cytokine levels in bronchoalveolar lavage fluid and plasma during mechanical ventilation . The secondary end point was the development of lung injury , as determined by consensus criteria for ALI , duration of mechanical ventilation , and mortality . Results One hundred fifty patients ( 74 conventional versus 76 lower tidal volume ) were enrolled and analyzed . No differences were observed in lavage fluid cytokine levels at baseline between the r and omization groups . Plasma interleukin-6 ( IL-6 ) levels decreased significantly more strongly in the lower-tidal-volume group ( ( from 51 ( 20 to 182 ) ng/ml to 11 ( 5 to 20 ) ng/ml versus 50 ( 21 to 122 ) ng/ml to 21 ( 20 to 77 ) ng/ml ; P = 0.01 ) ) . The trial was stopped prematurely for safety reasons because the development of lung injury was higher in the conventional tidal-volume group as compared with the lower tidal-volume group ( 13.5 % versus 2.6 % ; P = 0.01 ) . Univariate analysis showed statistical relations between baseline lung-injury score , r and omization group , level of positive end-expiratory pressure ( PEEP ) , the number of transfused blood products , the presence of a risk factor for ALI , and baseline IL-6 lavage fluid levels and the development of lung injury . Multivariate analysis revealed the r and omization group and the level of PEEP as independent predictors of the development of lung injury . Conclusions Mechanical ventilation with conventional tidal volumes is associated with sustained cytokine production , as measured in plasma . Our data suggest that mechanical ventilation with conventional tidal volumes contributes to the development of lung injury in patients without ALI at the onset of mechanical ventilation . Trial registration IS RCT Background and objective General anaesthesia impairs respiratory function in overweight patients . We wanted to determine whether increased tidal volume ( VT ) , with unchanged end-tidal carbon dioxide partial pressure ( PETCO2 ) , affects blood concentrations of oxygen and sevoflurane in overweight patients . Methods The present study is a prospect i ve , r and omised , clinical study . American Society of Anesthesiologists physical status I and II patients with BMI over 25 scheduled for elective surgery of the lower abdomen were r and omly assigned to one of two groups with 10 patients in each . One group was ventilated with normal VT ( NVT ) and one group with increased VT ( IVT ) achieved by increasing inspired plateau pressure 0.04 cmH2O kg−1 above initial plateau pressure . Extra apparatus dead space was added to maintain PETCO2 at 4.5 kPa . Respiratory rate was set at 15 min−1 , and sevoflurane was delivered to the fresh gas by a vaporiser set at 3 % . Arterial oxygenation , sevoflurane tensions ( Pasevo , Fisevo , PETsevo ) , paCO2 , PETCO2 , Vt and airway pressure were measured . Results The two groups of patients were similar with regard to sex , age , weight , height and BMI . Arterial oxygen tension ( mean ± SD ) was significantly higher in the IVT group ( 15 ± 4.3 vs. 10 ± 2.7 kPa after 60 min of anaesthesia , P < 0.05 ) . Mean PETsevo did not differ between the groups , whereas arterial sevoflurane tension ( mean ± SD ) was significantly higher in the IVT group ( 1.74 ± 0.18 vs. 1.43 ± 0.19 kPa after 60 min of anaesthesia , P < 0.05 ) . Conclusion Ventilation with larger tidal volumes with isocapnia maintained with added apparatus dead space increases the tension of oxygen and sevoflurane in arterial blood in overweight patients Objective To examine the mechanisms of ventilator-induced lung injury at low and high lung volumes . Design Prospect i ve , r and omized , laboratory study . Setting University research laboratory . SubjectsEighty-eight adult male Sprague-Dawley rats . Interventions Mechanical ventilation using low and high lung volumes . Measurements and Main Results An ex vivo rat lung model was used . In study I ( ventilation at low lung volumes ) , rat lungs ( n = 40 ) were r and omly assigned to various modes of ventilation : a ) opening and closing with positive end-expiratory pressure ( PEEP ; control ) : tidal volume 7 mL/kg and PEEP 5 cm H2O ; b ) opening and closing from zero end-expiratory pressure ( ZEEP ) : tidal volume 7 mL/kg and PEEP 0 ; or c ) atelectasis .  Peak inspiratory pressure was monitored at the beginning and end of 3 hrs of ventilation . At the end of 3 hrs of ventilation , the lungs were lavaged , and the concentrations of tumor necrosis factor-&agr ; , macrophage inflammatory protein-2 , and interleukin-6 cytokines were measured in the lavage . In study II ( ventilation at high volumes ) , rat lungs ( n = 45 ) were r and omly assigned to a ) cyclic lung stretch : pressure-controlled ventilation , peak inspiratory pressure 50 cm H2O , and PEEP 8 cm H2O ; b ) continuous positive airway pressure at 50 cm H2O ( CPAP50 ) ; or c ) CPAP at the mean airway pressure of the cyclic stretch group ( CPAP 31 cm H2O ) . Bronchoalveolar lavage cytokine concentrations ( tumor necrosis factor-&agr ; , macrophage inflammatory protein-2 , and interleukin-6 ) were measured at the end of 3 hrs of ventilation . In the low volume study , there was no difference in bronchoalveolar lavage cytokine concentrations between the PEEP group and the atelectatic group . All cytokines were significantly higher in the ZEEP group compared with the atelectasis group . Macrophage inflammatory protein-2 was significantly higher in the ZEEP group compared with the PEEP group . Lung compliance , as reflected by change in peak inspiratory pressure , was also significantly worse in the ZEEP compared with the PEEP group . In the high-volume study , tumor necrosis factor-&agr ; and interleukin-6 were significantly higher in the cyclic stretch group compared with the CPAP 31 group . There was no significant difference between the cytokine concentrations in the cyclic stretch group compared with the CPAP 50 group . Conclusion We conclude that at low lung volumes , cyclic opening and closing from ZEEP leads to greater increases in bronchoalveolar lavage cytokines than atelectasis . With high-volume ventilation , over time , the degree of overdistension is more associated with increases in bronchoalveolar lavage cytokines than cyclic opening and closing alone BACKGROUND Respiratory function is impaired in obese patients undergoing laparoscopic surgery . This study was performed to determine whether repeated lung recruitment combined with PEEP improves respiratory compliance and arterial partial pressure of oxygen ( Pa(O2 ) ) in obese patients undergoing laparoscopic gastric b and ing . METHODS Sixty patients with BMI > 30 kg m(-2 ) were r and omized , after induction of pneumoperitoneum  , to receive either PEEP of 10 cm H2O ( Group P ) , inspiratory pressure of 40 cm H2O for 15 s once ( Group R ) , Group R recruitment followed by PEEP 10 cm H2O ( Group RP ) , or Group RP recruitment but with the inspiratory manoeuvre repeated every 10 min ( Group RRP ) . Static respiratory compliance and Pa(O2 ) were determined after intubation , 10 min after pneumoperitoneum ( before lung recruitment ) , and every 10 min thereafter ( after recruitment ) . Results are presented as mean ( SD ) . RESULTS Pneumoperitoneum decreased respiratory compliance from 48 ( 3 ) to 30 ( 1 ) ml cm H2O(-1 ) and decreased Pa(O2 ) from 12.4 ( 0.3 ) to 8.8 ( 0.3 ) kPa in all groups ( P<0.01 ) . Immediately after recruitment , compliance was 32 ( 1 ) , 32 ( 2 ) , 40 ( 2 ) , and 40 ( 1 ) ml cm H2O(-1 ) and Pa(O2 ) was 9.1 ( 0.3 ) , 9.1 ( 0.1 ) , 11.9 ( 0.1 ) , and 11.9 ( 0.1 ) kPa in Groups P , R , RP , and RRP , respectively ( P<0.01 ) . Ten and 20 min later , Pa(O2 ) in Group R decreased to 9.2 ( 0.1 ) kPa and compliance in Group PR decreased to 33 ( 2 ) ml cm H2O(-1 ) , respectively ( P<0.01 ) . CONCLUSIONS Group RRP recruitment strategy was associated with the best intraoperative respiratory compliance and Pa(O2 ) in obese patients undergoing laparoscopic gastric b and ing OBJECTIVE To ascertain if protective ventilation can attenuate the damaging postoperative pulmonary effects of cardiopulmonary bypass ( increases in airway pressure , decreases in lung compliance , and increases in shunt ) . DESIGN Prospect i ve , r and omized clinical trial . SETTING Single university hospital . PARTICIPANTS Twenty-five patients undergoing elective coronary artery bypass graft procedure and early extubation . INTERVENTIONS Thirteen patients received conventional mechanical ventilation ( CV ; respiratory rate , 8 breaths/min ; tidal volume , 12 mL/kg ; fraction of inspired oxygen [ FIO2 ] , 1.0 ; positive end-expiratory pressure [ PEEP ] , + 5 ) , and 12 patients received protective mechanical ventilation ( PV ; respiratory rate , 16 breaths/min ; tidal volume , 6 mL/kg ; FIO2 , 1.0 ; PEEP , + 5 ) . Perioperative anesthetic and surgical management were st and ardized . Various pulmonary parameters were determined twice perioperatively : 10 minutes after intubation and 60 minutes after arrival in the intensive care unit . MEASUREMENTS AND MAIN RESULTS The mean postoperative increase in peak airway pressure in group CV was significantly larger than the mean postoperative increase in peak airway pressure in group PV ( 7.1 v 2.4 cm H2O ; p < 0.001 ) . Group CV experienced significant postoperative increases in plateau airway pressure ( p = 0.007 ) , but group PV did not ( p = 0.644 ) . The mean postoperative decrease in dynamic lung compliance in group CV was significantly larger than the mean postoperative decrease in dynamic lung compliance in group PV ( 14.9 v 5.5 mL/cm H2O ; p = 0.002 ) . Group CV experienced significant postoperative decreases in static lung compliance ( p = 0.014 ) , but group PV did not ( p = 0.645 ) . Group CV experienced significant postoperative increases in shunt ( 15.5 % to 21.4 % ; p = 0.021 ) , but group PV did not ( 18.4 % to 21.2 % ; p = 0.265 ) . CONCLUSIONS Data indicate that protective ventilation decreases pulmonary damage caused by mechanical ventilation in normal and abnormal lungs . The results of this investigation indicate that protective ventilation may also help attenuate the postoperative pulmonary dysfunction ( increases in airway pressure , decreases in lung compliance , and increases in shunt ) commonly seen in patients after exposure to cardiopulmonary bypass High airway pressure may be injurious to lung parenchyma , but lowering airway pressure using conventional mechanical ventilation necessitates lowering tidal volume ( VT ) . Intubated patients in the surgical intensive care unit ( SICU ) were r and omly assigned to group 1 ( VT = 12 ml/kg , n = 56 ) or group 2 ( VT = 6 ml/kg , n = 47 ) . Variables recorded included acute physiology and chronic health evaluation ( APACHE II ) score , mean peak airway pressure ( MPAP ) , mean PaO2/FIO2 , incidence of pulmonary infectious complications ( PIC ) , duration of intubation ( DOI ) , and duration of SICU stay ( DOS ) . Results in the table are means + /- SE . ( table ; see text ) The incidence of pulmonary infection tended to be lower and DOI and DOS tended to be shorter for nonneurosurgical and noncardiac surgical patients r and omized to low VT , suggesting that morbidity may be decreased . The use of low VT was associated with a statistically significant but clinical ly irrelevant decrease in oxygenation . The routine use of low VT appeared to be safe in a selected population of patients in the SICU Because atelectasis of the left lower lobe is a frequent complication of open heart surgery , we evaluated the efficacy of routine therapy with positive end-expiratory pressure ( PEEP ) to prevent this complication . Twenty-four patients were r and omly assigned to either a group receiving therapy with PEEP ( ten patients ) or to a group with no PEEP ( 14 patients ) . The two groups could not be distinguished by age , weight , the forced expiratory volume in one second ( FEV1 ) , the ratio of FEV1 over the forced vital capacity , the time on the pump , the units of blood transfused , the tidal volume , or the hours of mechanical ventilation . There was no significant roentgenographic difference between the two groups in either the degree or frequency of left lower lobe atelectasis . While the arterial-alveolar ratios tended to improve over time in those patients receiving therapy with PEEP , this improvement was not clinical ly significant . No complications were encountered with the use of PEEP . We conclude that the routine use of PEEP following open heart surgery is safe but offers no advantage over st and ard ventilatory techniques Objective To assess respiratory mechanics on the 1st and 5th days of mechanical ventilation in a cohort of brain-damaged patients on positive end-expiratory pressure ( PEEP ) of 8 cmH2O or zero PEEP ( ZEEP ) . Design and setting Physiological study with r and omized control trial design in a multidisciplinary intensive care unit of a university hospital . Patients and measurements Twenty-one consecutive mechanically ventilated patients with severe brain damage and no acute lung injury were r and omly assigned to be ventilated with ZEEP ( n = 10 ) or with 8 cmH2O of PEEP ( n = 11 ) . Respiratory mechanics and arterial blood gases were assessed on days 1 and day 5 of mechanical ventilation . Results In the ZEEP group on day 1 static elastance and minimal resistance were above normal limits ( 18.9 ± 3.8 cmH2O/l and 5.6 ± 2.2 cmH2O/l per second , respectively ) ; on day 5 static elastance and iso-CO2 minimal resistance values were higher than on day 1 ( 21.2 ± 4.1 cmH2O/l ; 7.0 ± 1.9 cmH2O/l per second , respectively ) . In the PEEP group these parameters did not change significantly . One of the ten patients on ZEEP developed acute lung injury . On day 5 there was a significant decrease in PaO2/FIO2 in both groups . Conclusions On day 1 of mechanical ventilation patients with brain damage exhibit abnormal respiratory mechanics . After 5 days of mechanical ventilation on ZEEP static elastance and minimal resistance increased significantly , perhaps reflecting “ low lung volume ” injury . Both could be prevented by administration of moderate levels of PEEP Background : Ventilator-induced lung injury has been attributed to the interaction of several factors : tidal volume ( VT ) , positive end-expiratory pressure ( PEEP ) , transpulmonary driving pressure ( difference between transpulmonary pressure at end-inspiration and end-expiration , & Dgr;P , L ) , and respiratory system plateau pressure ( Pplat , rs ) . Methods : Forty-eight Wistar rats received Escherichia coli lipopolysaccharide  intratracheally . After 24 h , animals were r and omized into combinations of VT and PEEP , yielding three different & Dgr;P , L levels : & Dgr;P , LLOW ( VT = 6 ml/kg , PEEP = 3 cm H2O ) ; & Dgr;P , LMEAN ( VT = 13 ml/kg , PEEP = 3 cm H2O or VT = 6 ml/kg , PEEP = 9.5 cm H2O ) ; and & Dgr;P , LHIGH ( VT = 22 ml/kg , PEEP = 3 cm H2O or VT = 6 ml/kg , PEEP = 11 cm H2O ) . In other groups , at low VT , PEEP was adjusted to obtain a Pplat , rs similar to that achieved with & Dgr;P , LMEAN and & Dgr;P , LHIGH at high VT . Results : At & Dgr;P , LLOW , expressions of interleukin (IL)-6 , receptor for advanced glycation end products ( RAGE ) , and amphiregulin were reduced , despite morphometric evidence of alveolar collapse . At & Dgr;P , LHIGH ( VT = 6 ml/kg and PEEP = 11 cm H2O ) , lungs were fully open and IL-6 and RAGE were reduced compared with & Dgr;P , LMEAN ( 27.4 ± 12.9 vs. 41.6 ± 14.1 and 0.6 ± 0.2 vs. 1.4 ± 0.3 , respectively ) , despite increased hyperinflation and amphiregulin expression . At & Dgr;P , LMEAN ( VT = 6 ml/kg and PEEP = 9.5 cm H2O ) , when PEEP was not high enough to keep lungs open , IL-6 , RAGE , and amphiregulin expression increased compared with & Dgr;P , LLOW ( 41.6 ± 14.1 vs. 9.0 ± 9.8 , 1.4 ± 0.3 vs. 0.6 ± 0.2 , and 6.7 ± 0.8 vs. 2.2 ± 1.0 , respectively ) . At Pplat , rs similar to that achieved with & Dgr;P , LMEAN and & Dgr;P , LHIGH , higher VT and lower PEEP reduced IL-6 and RAGE expression . Conclusion : In the acute respiratory distress syndrome model used in this experiment , two strategies minimized ventilator-induced lung injury : ( 1 ) low VT and PEEP , yielding low & Dgr;P , L and Pplat , rs ; and ( 2 ) low VT associated with a PEEP level sufficient to keep the lungs open OBJECTIVES Respiratory support for patients recovering from cardiopulmonary bypass and cardiac surgery uses large tidal volumes and a minimal level of positive end-expiratory pressure . Recent data indicate that these ventilator setting s might cause pulmonary and systemic inflammation in patients with acute lung injury . We examined the hypothesis that high tidal volumes and low levels of positive end-expiratory pressure might worsen the inflammatory response associated to cardiopulmonary bypass . METHODS Forty patients undergoing elective coronary artery bypass were r and omized to be ventilated after cardiopulmonary bypass disconnection  with high tidal volume/low positive end-expiratory pressure ( 10 - 12 mL/kg and 2 - 3 cm H2O , respectively ) or low tidal volume/high positive end-expiratory pressure ( 8 mL/kg and 10 cm H2O , respectively ) . Interleukin 6 and interleukin 8 levels were measured in the bronchoalveolar lavage fluid and plasma . Sample s were taken before sternotomy ( time 0 ) , immediately after cardiopulmonary bypass separation ( time 1 ) , and after 6 hours of mechanical ventilation ( time 2 ) . RESULTS Interleukin 6 and interleukin 8 levels in the bronchoalveolar lavage fluid and plasma significantly increased at time 1 in both groups but further increased at time 2 only in patients ventilated with high tidal volume/low positive end-expiratory pressure . Interleukin 6 and interleukin 8 levels in the bronchoalveolar lavage fluid and in the plasma at time 2 were higher with high tidal volume/low positive end-expiratory pressure than with low tidal volume/high positive end-expiratory pressure . CONCLUSION Mechanical ventilation might be a cofactor able to influence the inflammatory response after cardiac surgery Background : It is unclear whether positive end‐expiratory pressure ( PEEP ) is needed to maintain the improved oxygenation and lung volume achieved after a lung recruitment maneuver in patients ventilated after cardiac surgery performed in the cardiopulmonary bypass ( CPB ) We investigated the effects of body mass index ( BMI ) on functional residual capacity ( FRC ) , respiratory mechanics ( compliance and resistance ) , gas exchange , and the inspiratory mechanical work done per liter of ventilation during general anesthesia . We used the esophageal balloon technique , together with rapid airway occlusion during constant inspiratory flow , to partition the mechanics of the respiratory system into its pulmonary and chest wall components . FRC was measured by using the helium dilution technique . We studied 24 consecutive and unselected patients during general anesthesia , before surgical intervention , in the supine position ( 8 normal subjects with a BMI < or = to25 kg/m2 , 8 moderately obese patients with a BMI > 25 kg/m2 and < 40 kg/m2 , and 8 morbidly obese patients with a BMI > or = to40 kg/m2 ) . We found that , with increasing BMI : 1.FRC decreased exponentially ( r = 0.86 ; P < 0.01 ) 2.the compliance of the total respiratory system and of the lung decreased exponentially ( r = 0.86 ; P < 0.01 and r = 0.81 ; P < 0.01 , respectively ) , whereas the compliance of the chest wall was only minimally affected ( r = 0.45 ; P < 0.05 ) 3.the resistance of the total respiratory system and of the lung increased ( r = 0.81 ; P < 0.01 and r = 0.84 ; P < 0.01 , respectively ) , whereas the chest wall resistance was unaffected ( r = 0.06 ; P = not significant ) 4.the oxygenation index ( PaO2/PAo2 ) decreased exponentially ( r = 0.81 ; P < 0.01 ) and was correlated with FRC ( r = 0.62 ; P < 0.01 ) , whereas PaCO2 was unaffected ( r = 0.06 ; P = not significant ) 5.the work of breathing of the total respiratory system increased , mainly due to the lung component ( r = 0.88 ; P < 0.01 and r = 0.81 ; P < 0.01 , respectively ) . In conclusion , BMI is an important determinant of lung volumes , respiratory mechanics , and oxygenation during general anesthesia with patients in the supine position . Implication s : The aim of this study was to investigate the influence of body mass on lung volumes , respiratory mechanics , and gas exchange during general anesthesia . ( Anesth Analg 1998;87:654 - 60 Background : Alveolar fibrin deposition is a hallmark of acute lung injury , result ing from activation of coagulation and inhibition of fibrinolysis . Previous studies have shown that mechanical ventilation with high tidal volumes may aggravate lung injury in patients with sepsis and acute lung injury . The authors sought to determine the effects of mechanical ventilation on the alveolar hemostatic balance in patients without preexistent lung injury . Methods : Patients scheduled for 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 later bronchoalveolar lavage fluid and blood sample s were obtained , and markers of coagulation and fibrinolysis were measured . Results : In contrast to mechanical ventilation with lower tidal volumes and PEEP ( n = 21 ) , the use of higher tidal volumes without PEEP ( n = 19 ) caused activation of bronchoalveolar coagulation , as reflected by a marked increase in thrombin – antithrombin complexes , soluble tissue factor , and factor VIIa after 5 h of mechanical ventilation . Mechanical ventilation with higher tidal volumes without PEEP caused an increase in soluble thrombomodulin in lavage fluids and lower levels of bronchoalveolar activated protein C in comparison with lower tidal volumes and PEEP . Bronchoalveolar fibrinolytic activity did not change by either ventilation strategy . Conclusions : Mechanical ventilation with higher tidal volumes and no PEEP promotes procoagulant changes , which are largely prevented by the use of lower tidal volumes and PEEP
Background It has been shown that the application of a lung-protective mechanical ventilation strategy can improve the prognosis of patients with acute lung injury ( ALI ) or acute respiratory distress syndrome ( ARDS ) .
However , the optimal mechanical ventilation strategy for intensive care unit ( ICU ) patients without ALI or ARDS is uncertain .
Therefore , we performed a network meta- analysis to identify the optimal mechanical ventilation strategy for these patients .