Objective To investigate the effects of positive end-expiratory pressure (PEEP) level on end-expiratory lung volume (EELV) during assisted ventilation in chronic obstructive pulmonary disease （COPD） patients，to provide physiological evidence to guide optimal setting of PEEP level in clinical practice.Methods Eight intubated patients with acute exacerbation of COPD were recruited for the study when the patients were in relatively stable condition after treatment.The static intrinsic PEEP (PEEPistat) and dynamic intrinsic PEEP (PEEPidyn) were measured by using airway occlusion method and esophageal balloon-tipped catheter technique,respectively.Changes in EELV (ΔEELV) were measured with inspiratory capacity (IC) method.Relations between PEEP level and ΔEELV were analyzed by curve estimation method.Results ΔEELV as a function of level of PEEP was shown as a sigmoid model.The low inflection points of the curves when PEEP levels were expressed as PEEP/PEEPistat ratio，PEEP/PEEPidyn ratio or actual PEEP setting (PEEP-a) were 0.74，0.76 or 3.6 cm H2O,respectively.The corresponding ΔEELV expressed as ΔEELV/IC（%） were 9.6%，9.1% and 7.4%,respectively.Conclusions In AECOPD patients demanding mechanical ventilation，the changes of lung volume (ΔEELV) in response to progressive increase of PEEP level were shown to be a sigmoid model.Setting PEEP level at 0.74 of PEEPistat，or 0.76 of PEEPidyn can avoid the steep increase of lung volume.
Objective To compare the effects of high and low positive end-expiratory pressure( PEEP) levels on mortality and risk of barotrauma in patients with acute respiratory distress syndrome ( ARDS) . Methods Randomized controlled trials ( RCTs) were recruited from PubMed( 1966-2008. 9) ,EMBASE( 1980-2008. 9) , Cochrane Database ( Issue 2, 2008) , Chinese Cochrane Centre Database and CBMdisc ( 1978-2008. 9) . Related published and unpublished data and attached references were hand searched. All RCTs about ventilation with PEEP for patients with ARDS were included, then a systematic review were performed. Results Five eligible trials were enrolled in the systematic review. According to ventilation strategy, all trials were divided into subgroup A( low tidal volumes + high PEEP vs traditional tidal volumes + low PEEP) and subgroup B( low tidal volumes + high PEEP vs low tidal volumes + low PEEP) . In subgroup A, high PEEP was associated with a lower mortality[ RR 0. 59, 95%CI( 0. 43, 0. 82) ] and a lower prevalence of barotraumas [ RR 0. 24, 95% CI( 0. 09, 0. 70) ] in patients with ARDS. In subgroup B, the difference in mortality[ RR 0. 97, 95%CI( 0. 83, 1. 13) ] and barotraumas[ RR 1. 13, 95% CI( 0. 78, 1. 63) ]were not significant. Conclusions As compared with conventional ventilation, low tidal volumes and high PEEP ventilation strategy is associated with improved survival and a lower prevalence of barotraumas in patients with ARDS. It is necessary to further confirm the role of sole high PEEP in the ventilation strategy.
Objective To investigate whether pulse pressure variation( ΔPP) reflect the effects of PEEP and fluid resuscitation ( FR) on hemodynamic effects. Methods Twenty critical patients with acute lung injury was ventilated with volume control ( VT =8 mL/kg, Ti/Te = 1∶2) , and PaCO2 was kept at 35 to 45 mm Hg. PEEP was setted as 5 cm H2O and 15 cmH2O in randomized order. Hemodynamic parameters including cardiac index, pulse pressure, central venous pressure, etc. were monitered by PiCCO system.Measurements were performed after the application of 5 cmH2O PEEP ( PEEP5 group) and 15 cm H2OPEEP ( PEEP15 group) respectively. When the PEEP-induced decrease in cardiac index ( CI) was gt; 10% ,measurements were also performed after fluid resuscitation. Results Compared with PEEP5 group, CI was decreased significantly in PEEP15 group( P lt;0. 05) , and ΔPP was increased significantly( P lt; 0. 05) . In 14 patients whose PEEP-induced decrease in CI was gt; 10% , fluid resuscitation increased CI from ( 3. 01 ±0. 57) L·min - 1·m- 2 to ( 3. 62 ±0. 68) L·min- 1 ·m- 2 ( P lt;0. 01) , and decreased ΔPP from ( 17 ±3) % to ( 10 ±2) % ( P lt;0. 01) . PEEP15 -induced decrease in CI was correlated negatively with ΔPP on PEEP5 ( r= - 0.91, P lt;0. 01) and with the PEEP15 -induced increase in ΔPP ( r = - 0. 79, P lt;0. 01) . FR-induced changes in CI correlated with ΔPP before FR ( r =0. 96, P lt; 0. 01) and with the FR-induced decrease in ΔPP ( r= - 0. 95, P lt; 0. 01) . Conclusions In ventilated patients with ALI, ΔPP may be a simple anduseful parameter in predicting and assessing the hemodynamic effects of PEEP and FR.
ObjectiveTo evaluate the effect of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in acute lung injury (ALI) with intra-abdominal hypertension (IAH). MethodsSix pigs were anesthetized and received mechanical ventilation (MV). Volume controlled ventilation was set with tidal volumn(VT) of 8 mL/kg,respiratory rate(RR) of 16 bpm,inspired oxygen concentration (FiO2) of 0.40,and PEEP of 5 cm H2O. ALI was induced by repeated lung lavage with diluted hydrochloric acid (pH<2.5) until PaO2/FiO2 declined to 150 mm Hg or less to established ALI model. Intra-abdominal hypertension was induced by an nitrogen inflator to reach intra-abdominal pressure of 20 mm Hg. Respiratory parameters and hemodynamics were continuously recorded at different PEEP levels(5,10,15,and 20 cm H2O). Every level was maintained for one hour. ResultsPaO2/FiO2 in PEEP5,10,15 and 20 were 90±11,102±10,172±23 and 200±34 mm Hg respectively. PaO2/FiO2 in PEEP15 and 20 were significantly higher than those in PEEP5 and 10 (P<0.05). Chest wall compliance (Ccw) in PEEP5,15 and 20 were 26±3,76±15 and 85±14 mL/cm H2O respectively. Ccw in PEEP15 and 20 were significantly higher than those in PEEP5 (P<0.05). There was no significant difference in lung compliance (CL) in different PEEP levels (P>0.05). Plateau pressure(Pplat) in PEEP5,10,15 and 20 were 30±3,31±2,36±2 and 38±4 cm H2O respectively. Pplat in PEEP15 and 20 were significantly higher than those in PEEP5 and 10 (P<0.05). There was no significant difference in Pplat between PEEP15 and 20 (P>0.05). Heart rate (HR) in PEEP5,15 and 20 were 113±17,147±30,and 160±30 beat/min respectively. HR in PEEP15 and 20 were significantly higher than those in PEEP5 (P<0.05). There was no significant difference in HR between PEEP15 and 20 (P>0.05).Cardiac index (CI) in PEEP5 and 20 were 4.5±0.6 and 3.5±0.6 L·min-1·m-2 respectively. CI in PEEP20 was significantly lower than that in PEEP5 (P<0.05). There was no significant difference in CI in PEEP5,10 or 15(P>0.05). Central venous pressure(CVP) in PEEP5,15 and 20 were 12±2,17±2,and 18±3 mm Hg respectively. CVP in PEEP15 and 20 were significantly higher than those in PEEP5 (P<0.05). There was no significant difference in CVP between PEEP15 and 20 (P>0.05). There were no significant differences in MAP,SVRI,ITBVI,GEDI,PVPI,or EVLWI between different PEEP levels. ConclusionConcomitant ALI and IAH can induce great impairments in respiratory physiology. When PEEP is gradually increased,oxygenation and the respiratory function are improved without significant secondary hemodynamic disturbances.
ObjectiveTo investigate different levels of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in patients with acute respiratory distress syndrome (ARDS) complicated with intra-abdominal hypertension(IAH). MethodsThirty patients with moderate ARDS admitted in ICU between January 2012 and December 2014 were recruited in the study. They were divided into three groups according to intra-abdominal pressure (IAP),including 10 patients with normal abdominal pressure as a normal IAP group,10 patients with IAP of 12-15 mm Hg as an IAPⅠ group,and 10 patients with IAP of 16-20 mm Hg as an IAPⅡ group. The optimal level of PEEP was titrated according to the best oxygenation methods. The changes of oxygenation index (OI),respiratory mechanics and hemodynamics before and after the optimal level of PEEP were monitored and compared in all groups. The 28-day mortality and ICU stay were also compared. ResultsThe OI after titration was significantly improved compared to baseline in all groups (all P<0.01). The OI after titration in the IAPⅡ group was significantly higher than that in other two groups (all P<0.05). The static lung compliance (Cst) after titration significantly improved than baseline in all groups(all P<0.05),but no significant difference was revealed among three groups (all P>0.05). In the IAPⅡ group,the levels of PEEP,IAP,blood lactate,heart rate and airway plateau pressure after titration were significantly increased than baseline but higher than those in other two groups(all P<0.05),while the level of mean arterial pressure was significantly decreased and significantly lower than those in other two groups(all P<0.01). Meanwhile,the ICU stay was longest in the IAPⅡ group (P<0.01). There was no significant difference in 28-day mortality among three groups(all P>0.05). ConclusionsPEEP can significantly improve oxygenation in patients with ARDS complicated with IAH. The higher the IAP is,the higher the PEEP level is required. However the higher PEEP will significantly increase IAP which will cause adverse impacts on hemodynamics and can not improve the prognosis.
ObjectiveTo explore whether positive end-expiratiory pressure (PEEP) guided by the esophageal balloon manometry is better than the ARDS Network standard of care recommendations during treating traumatic acute respiratory distress syndrome (ARDS) patients with mechanical ventilation. MethodsTwelve traumatic ARDS patients selected from September 2013 to March 2015 in ICU of Xiamen No. 3 Hospital were administrated esophageal balloor catheter and underwent mechanical ventilation with PEEP adjusted according to measurements of esophageal pressure and the ARDS Network standard of care recommendations simultaneously. According to the selection method of PEEP, the patients were divided into two groups:the esophageal pressure guided group and the ARDS Network recommendations guided group (the control group). The changes of peak inspiratory pressure, esophageal pressure, transpulmonary end-expiratory pressure, transpulmonary end-inpiratory pressure, lung compliance at 0 h, 24 h, 48 h, 72 h following different PEEP treatments were observed and compared between two groups of patients. ResultsA mean PEEP in the esophageal pressure guided group of (10.98±4.36)cm H2O was significantly higher than the control group of (7.13±2.21)cm H2O (P<0.01). The transpulmonary end-expiratory pressure was significantly higher in the esophageal pressure guided group (0.71±0.62)cm H2O than the control group (-2.29±3.49) cm H2O. And all of the mean transpulmonary end-expiratory pressure remained above zero in the esophageal pressure guided group, whereas in the control group 73% patients remained negative (P<0.01). ConclusionsEsophageal pressure method adjusts PEEP for traumatic ARDS patients with mechanical ventilation through estimating pleural pressure so as to calculate transpulmonary pressure. It can identify traumatic ARDS patients who would benefit from the high PEEP, adjust PEEP individually and meet patients' need more satisfactorily.
ObjectiveTo systematically evaluate the benefits and harms of intraoperative positive end-expiratory pressure (PEEP) to all adult patients suffered surgery, especially on the postoperative mortality and pulmonary outcomes. MethodsWe electronically searched PubMed, EMbase, The Cochrane library (Issue 3, 2012), CBM, CNKI from inception to January 2013, for randomized controlled trials (RCTs) about PEEP for the prevention of pulmonary complications. Two reviewers independently screened literature according to the inclusion and exclusion criteria, extracted the data, and evaluated the quality of the included studies. Then meta-analysis was conducted using RevMan 5.1 software. ResultsA total of 8 RCTs involving 336 patients were finally included. The results of meta-analysis showed that there was no difference between two groups in mortality (OR=0.95, 95%CI 0.13 to 6.92, P=0.96). However, the PEEP group had a higher PaO2/FiO2 the first day after surgery (MD=22.98, 95%CI 4.40 to 41.55, P=0.02), while there was no difference 2-3 days after surgery (MD=12.59, 95%CI-6.78 to 31.96, P=0.31). Meanwhile, postoperative atelectasis was less in the PEEP group (OR=0.27, 95%CI 0.08 to 0.9, P=0.03). ConclusionChoosing PEEP mode during general anaesthesia may improve postoperative oxygenation index in the first day after surgery, and reduce pulmonary complications, which has a protective effect on patients pulmonary function. However, it has no marked influence on the prognosis. Because of the limited quality and sampling size of the induced studies, this conclusion still needs to be further proved by more large-scale, multicenter and perspective RCTs.
ObjectiveTo evaluate the effect of driving pressure-guided lung protective ventilation strategy on lung function in adult patients under elective cardiac surgery with cardiopulmonary bypass.MethodsIn this randomized controlled trial, 106 patients scheduled for elective valve surgery via median sternal incision under cardiopulmonary bypass from July to October 2020 at West China Hospital of Sichuan University were included in final analysis. Patients were divided into two groups randomly. Both groups received volume-controlled ventilation. A protective ventilation group (a control group, n=53) underwent traditional lung protective ventilation strategy with positive end-expiratory pressure (PEEP) of 5 cm H2O and received conventional protective ventilation with tidal volume of 7 mL/kg of predicted body weight and PEEP of 5 cm H2O, and recruitment maneuver. An individualized PEEP group (a driving pressure group, n=53) received the same tidal volume and recruitment, but with individualized PEEP which produced the lowest driving pressure. The primary outcome was oxygen index (OI) after ICU admission in 30 minutes, and the secondary outcomes were the incidence of OI below 300 mm Hg, the severity of OI descending scale (the Berlin definition), the incidence of pulmonary complications at 7 days after surgery and surgeons’ satisfaction on ventilation.ResultsThere was a statistical difference in OI after ICU admission in 30 minutes between the two groups (273.5±75.5 mm Hg vs. 358.0±65.3 mm Hg, P=0.00). The driving pressure group had lower incidence of postoperative OI<300 mm Hg (16.9% vs. 49.0%, OR=0.21, 95%CI 0.08-0.52, P=0.00) and less severity of OI classification than the control group (P=0.00). The incidence of pulmonary complications at 7 days after surgery was comparable between the driving pressure group and the control group (28.3% vs. 33.9%, OR=0.76, 95%CI 0.33-1.75, P=0.48). The atelectasis rate was lower in the driving pressure group (1.0% vs. 15.0%, OR=0.10, 95%CI 0.01-0.89, P=0.01).ConclusionApplication of driving pressure-guided ventilation is associated with a higher OI and less lung injury after ICU admission compared with the conventional protective ventilation in patients having valve surgery.
ObjectiveTo evaluate the correlation between positive end-expiratory pressure (PEEP) level and postoperative pulmonary complications (PPCs) in patients undergoing thoracoscopic lung surgery. MethodsThe clinical data of patients who underwent elective thoracoscopic lung surgery at West China Hospital of Sichuan University from January 2022 to June 2023 were retrospectively analyzed. Patients were divided into 2 groups according to intraoperative PEEP levels: a PEEP 5 cm H2O group and a PEEP 10 cm H2O group. The incidence of PPCs in the two groups after matching was compared using a nearest neighbor matching method with a ratio of 1∶1, setting the clamp value as 0.02. ResultsA total of 538 patients were screened, and after propensity score-matching, a total of 229 pairs (458 patients) were matched, with an average age of 53.9 years and 69.4% (318/458) females. A total of 118 (25.8%) patients had PPCs during hospitalization after surgery, including 60 (26.2%) patients in the PEEP 5 cm H2O group and 58 (25.3%) patients in the PEEP 10 cm H2O group, with no statistically significant difference between the two groups [OR=0.997, 95%CI (0.495, 1.926), P=0.915]. Multivariate logistic regression analysis showed that PEEP was not an independent risk factor for PPCs [OR=0.920, 95%CI (0.587, 1.441), P=0.715]. ConclusionFor patients undergoing thoracoscopic lung surgery, intraoperative PEEP (5 cm H2O or 10 cm H2O) is not associated with the risk of PPCs during hospitalization after surgery, which needs to be further verified by prospective, large-sample randomized controlled studies.