PEEP Levels Research Articles

Effect of prone positioning on cannula function and impaired oxygenation during extracorporeal circulation

Prone ventilation is an effective method for improving oxygenation in patients with acute respiratory failure. However, in extracorporeal circulation, there is a risk of cannula-related complications when changing the position. In this study, we investigated cannula-related complications when changing position for prone ventilation and the effect of prone ventilation on impaired oxygenation in patients who underwent extracorporeal membrane oxygenation (ECMO). The study subjects were patients who underwent prone ventilation during ECMO in the period from 2004 to 2011. Indication for prone ventilation was the presence of dorsal infiltration shown by lung computed tomography. Factors investigated were cannula insertion site, dislodgement or obstruction of the cannula, malfunction of vascular access and unplanned dislodgement of the catheters when changing position. Mean arterial pressure, PaO2/FiO2, PEEP level, blood flow and rotation speed of the pump were also determined before and after position change. Five patients were selected as study subjects. The mean duration of prone positioning was 15.3 ± 0.5 h. Strict management during position changes prevented cannula-related complications in the patients who underwent extracorporeal circulation. There were no significant changes in mean arterial pressure, PEEP level, blood flow and rotation speed of the pump when changing position. Low PaO2/FiO2 prior to prone ventilation was significantly increased after supine to prone and then prone to supine position. Prone positioning to improve impaired oxygenation is a safe procedure and not a contraindication in patients receiving extracorporeal circulation.

Respiratory induced dynamic variations of stroke volume and its surrogates as predictors of fluid responsiveness: applicability in the early stages of specific critical states

Respiratory induced dynamic variations of stroke volume and its surrogates are very sensitive and specific predictors of fluid responsiveness, but their use as targets for volume management can be limited. In a recent study, limiting factors were present in 53 % of surgical patients with inserted arterial line. In the intensive care unit (ICU) population the frequency is presumably higher, but the real prevalence is unknown. Our goal was to study the feasibility of dynamic variations guided initial volume resuscitation in specific critical states. We have performed a 5 year retrospective evaluation of patients admitted with diagnosis sepsis, polytrauma, after high risk surgery or cardiac arrest. Occurrence of major (sedation, mandatory ventilation and tidal volume, open chest and arrhythmias) and minor limiting factors (PEEP level, use of vasopressors and presence of arterial catheter) was screened within the first 24 h after admission. In the study period 1296 patients were hospitalized in our ICU with severe sepsis (n = 242), polytrauma (n = 561), after high risk surgery (n = 351) or cardiac arrest (n = 141). From these patients 549 (42.4 %) fulfilled all major criteria for applicability of dynamic variations. In our evaluation only limited number of patients admitted for polytrauma (51 %), sepsis (37 %), after cardiac arrest (39 %) or surgical procedure (33 %) fulfil all the major criteria for use of dynamic variations at the ICU admission. The prevalence was similar in patients with shock. Occurrence of minor factors can pose further bias in evaluation of these patients. General use of dynamic variations guided protocols for initial resuscitations seems not universally applicable.

Acute cor pulmonale in ARDS

Acute cor pulmonale in ARDS

Alveolar recruitment and optimal level of PEEP improves oxygenation and lung efficiency during one-lung ventilation. A pilot study

Hospital Clínico Universitario de Valencia, Dept of Anaesthesiology & Intensive Care, valencia, Spain

A Comparison of Leak Compensation in Acute Care Ventilators During Noninvasive and Invasive Ventilation: A Lung Model Study

Although leak compensation has been widely introduced to acute care ventilators to improve patient-ventilator synchronization in the presence of system leaks, there are no data on these ventilators' ability to prevent triggering and cycling asynchrony. The goal of this study was to evaluate the ability of leak compensation in acute care ventilators during invasive and noninvasive ventilation (NIV). Using a lung simulator, the impact of system leaks was compared on 7 ICU ventilators and 1 dedicated NIV ventilator during triggering and cycling at 2 respiratory mechanics (COPD and ARDS models) settings, various modes of ventilation (NIV mode [pressure support ventilation], and invasive mode [pressure support and continuous mandatory ventilation]), and 2 PEEP levels (5 and 10 cm H(2)O). Leak levels used were up to 35-36 L/min in NIV mode and 26-27 L/min in invasive mode. Although all of the ventilators were able to synchronize with the simulator at baseline, only 4 of the 8 ventilators synchronized to all leaks in NIV mode, and 2 of the 8 ventilators in invasive mode. The number of breaths to synchronization was higher during increasing than during decreasing leak. In the COPD model, miss-triggering occurred more frequently and required a longer time to stabilize tidal volume than in the ARDS model. The PB840 required fewer breaths to synchronize in both invasive and noninvasive modes, compared with the other ventilators (P < .001). Leak compensation in invasive and noninvasive modes has wide variations between ventilators. The PB840 and the V60 were the only ventilators to acclimate to all leaks, but there were differences in performance between these 2 ventilators. It is not clear if these differences have clinical importance.

Effect of Recruitment Maneuvers on Oxygen Saturation, End Tidal Carbon Dioxide and Lung Mechanics in Pressure Control Ventilation Versus Volume Control Ventilation for Patient Undergoing Laparoscopic Sleeve Gastrectomy

Background: Atelectasis occurs regularly after induction of general anesthesia in bariatric surgery, persists postoperatively, and may contribute to significant postoperative morbidity. Intraoperative recruitment maneuver improve lung ventilation, oxygenation and lung mechanics.&#x0D; Objectives: The aim of this study was to compare the effects of recruitment maneuver on oxygen saturation, end tidal carbon dioxide and lung mechanics in two Groups; the volume control group and pressure control group with fixed level of PEEP.&#x0D; Patient and Method: Forty patients, BMI &gt;35 kg/ m2, who have no major obstructive or restrictive respiratory disorders where allocated in two groups (volume group and pressure group). In both groups we tested the effect of recruitment maneuver on SpO2, ETCO2 and lung mechanics (The volume group of 20 patients and the pressure group of 20 patients).&#x0D; Results: We found that alveolar recruitment effectively decreased Intraoperative EtCO2 in pressure group ( P.value &lt;0.05) while ( P.value was&gt;0.05 ) for volume group and increase Intraoperative SpO2in BOTH groups ( P.value &lt; 0.05) with more effect seen in pressure group. BUT, soon after extubation SpO2 decreases again and P.value was &gt;0.05 for both groups.&#x0D; Also we found that pulmonary mechanics (PIP, EXPvt) were significantly improved after recruitment (BOTH P.value &lt; 0.05).&#x0D; Conclusions: our data suggest that the use of alveolar recruitment maneuver may be an effective mode of improving intraoperative oxygenation in morbidly obese patients. Our results showed that the effect is to be short lived and end after extubation. with significant improvement in lung mechanics.

Predictive value of pulse pressure variation for fluid responsiveness in septic patients using lung-protective ventilation strategies

BackgroundThe applicability of pulse pressure variation (ΔPP) to predict fluid responsiveness using lung-protective ventilation strategies is uncertain in clinical practice. We designed this study to evaluate the accuracy of this parameter in predicting the fluid responsiveness of septic patients ventilated with low tidal volumes (TV) (6 ml kg−1).MethodsForty patients after the resuscitation phase of severe sepsis and septic shock who were mechanically ventilated with 6 ml kg−1 were included. The ΔPP was obtained automatically at baseline and after a standardized fluid challenge (7 ml kg−1). Patients whose cardiac output increased by more than 15% were considered fluid responders. The predictive values of ΔPP and static variables [right atrial pressure (RAP) and pulmonary artery occlusion pressure (PAOP)] were evaluated through a receiver operating characteristic (ROC) curve analysis.ResultsThirty-four patients had characteristics consistent with acute lung injury or acute respiratory distress syndrome and were ventilated with high levels of PEEP [median (inter-quartile range) 10.0 (10.0–13.5)]. Nineteen patients were considered fluid responders. The RAP and PAOP significantly increased, and ΔPP significantly decreased after volume expansion. The ΔPP performance [ROC curve area: 0.91 (0.82–1.0)] was better than that of the RAP [ROC curve area: 0.73 (0.59–0.90)] and pulmonary artery occlusion pressure [ROC curve area: 0.58 (0.40–0.76)]. The ROC curve analysis revealed that the best cut-off for ΔPP was 6.5%, with a sensitivity of 0.89, specificity of 0.90, positive predictive value of 0.89, and negative predictive value of 0.90.ConclusionsAutomatized ΔPP accurately predicted fluid responsiveness in septic patients ventilated with low TV.

Measurement of Alveolar Recruitment at the Bedside: The Beginning of a New Era in Respiratory Monitoring?

In this issue of respiratory care, Wallet and co-workers bring convincing evidence that PEEP-induced alveolar recruitment can be inferred from regional changes in lung densities computed on frontal bedside digital chest radiographies obtained at 2 different PEEP levels in patients with ARDS.[1][1]

Evaluation of Recruited Lung Volume at Inspiratory Plateau Pressure With PEEP Using Bedside Digital Chest X-ray in Patients With Acute Lung Injury/ARDS

We wanted to assess whether there was a significant relationship between recruited lung volume (V(rec)) and change in density on digital processed chest x-ray measured at 2 different levels of inspiratory plateau pressure corresponding to 2 PEEP levels in patients with acute lung injury or ARDS. In 14 subjects, PEEP 5 cm H2O and 15 cm H2O were prospectively applied in a random order for 10 min. At the end of each period, chest x-ray was taken using a digital portable device, and a pressure-volume curve of the respiratory system was performed. We also assessed P(aO2), and the static and the dynamic (C(dyn,rs)) compliance of the respiratory system. Change in end-expiratory lung volume between tidal breath and relaxation volume of the respiratory system was determined. Radiological attenuation was measured on chest x-rays in 4 regions of interest in the right lung, and in 3 regions of interest in the left lung, drawn in posterior intercostal spaces from top to bottom, by using dedicated software. The ratio of lung density in each region between PEEP 15 and PEEP 5 (rP15/P5) and their arithmetic mean (μP15/P5) were computed. V(rec) was determined from the pressure-volume curves. The median value of rP15/P5 in the 98 lung levels was 0.91 (0.80-1.01), which was significantly different from 1 (P < .001). The values of rP15/P5 were not significantly different between the lung levels. The median values of V(rec) and μP15/P5 were 288 (173-402) mL and 0.90 (0.80-0.97), respectively. There was a significant negative correlation between V(rec) and μP15/P5 (R = -0.77, P = .01). The reduction in μP15/P5 tended to correlate with the increase in C(dyn,rs) (R = -0.49, P = .077) or in P(aO2) (R = -0.53, P = .05) between PEEP 15 cm H2O and PEEP 5 cm H2O. Digital chest x-ray done at the bedside in acute lung injury/ARDS subjects was able to detect a reduction in density between PEEP 5 cm H2O and PEEP 15 cm H2O, which correlated with V(rec).

Individualized PEEP Setting in Subjects With ARDS: A Randomized Controlled Pilot Study

Low-tidal-volume ventilation may be associated with repetitive opening and closing of terminal airways. The use of PEEP is intended to keep the alveoli open. No method of adjusting the optimal PEEP has shown to be superior or to improve clinical outcomes. We conducted a pilot study to evaluate the effect of setting an individualized level of PEEP at the highest compliance on oxygenation, multiple-organ-dysfunction, and survival in subjects with ARDS. Subjects with ARDS ventilated with low tidal volumes and limitation of airway pressure to 30 cm H2O were randomized to either a compliance-guided PEEP group or an FIO2-guided group. Of the 159 patients with ARDS admitted during the study period, 70 met the inclusion criteria. Subjects in the compliance-guided group showed nonsignificant improvements in PaO2/FIO2 during the first 14 days, and in 28-day mortality (20.6% vs. 38.9%, P = .12). Multiple-organ-dysfunction-free days (median 6 vs 20.5 d, P = .02), respiratory-failure-free days (median 7.5 vs 14.5 d, P = .03), and hemodynamic-failure-free days (median 16 vs 22 d, P = .04) at 28 days were significantly lower in subjects with compliance-guided setting of PEEP. In ARDS subjects, protective mechanical ventilation with PEEP application according to the highest compliance was associated with less organ dysfunction and a strong nonsignificant trend toward lower mortality. ClinicalTrials.gov Number NCT01119872.

Dynamic Hysteresis Behaviour of Respiratory System Mechanics

Article Dynamic Hysteresis Behaviour of Respiratory System Mechanics was published on September 7, 2013 in the journal Biomedical Engineering / Biomedizinische Technik (volume 58, issue SI-1-Track-D).

Effects of different PEEP levels on respiratory mechanics and oxygenation after coronary artery bypass grafting

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. Randomized 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 samples, collected twenty minutes after intensive care unit admission. Patients with chronic obstructive pulmonary disease and patients submitted 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. 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). Higher levels of positive end-expiratory pressure in immediate postoperative period of coronary artery bypass grafting improved pulmonary compliance values and increased oxygenation indexes, resulting in lower frequency of hypoxemia.

Prone to survive and the priority rule in science

In 2005 we published the first study to show that mortality can be reduced by prone ventilation [1]. This study followed the large trial by the Prone-Supine Study Group of Gattinoni and colleagues published in the NEJM in 2001 [2] and another in 2005 that failed to show benefit [3]. We have speculated that the earlier trials failed to show benefit because the protocols of these studies stipulated that physicians do not change ventilator settings during the period of prone ventilation (in order to standardize the changes in gas exchange induced by this maneuver). As per protocol, both the prone and supine groups were subjected to the same mean airway pressures (MAP) and tidal volumes even after it was noted that the PaO2:FiO2 had improved in the prone group and they could be managed with lower MAP [4]. Gattinoni responded to our criticism of his study and conceded that, in retrospect, our approach of reducing ventilation as oxygenation improved was more appropriate [4]. Now a new study by the PROSEVA group has found that prone ventilation does indeed save lives. The stated rationale for the new study by the PROSEVA Study Group of Guerin and colleagues, in severe acute respiratory syndrome (ARDS) [5], was the meta-analysis data showing improved survival with prone position in patients with severe hypoxemic ARDS. The authors overcame the drawback of the older studies by targeting the a tidal volume of 6 ml per kilogram and the PEEP level selected from a PEEP-FiO2 table and they have demonstrated a survival advantage for prone ventilation. However, analysis stratified according to quartile of PaO2:FiO2 ratio at enrollment showed no significant differences in outcome in this study. They assumed a priori that benefits will accrue only to those with severe ARDS and so they report that prone ventilation helps this group, although their analysis shows severity of ARDS has little to do with improved survival. The authors do not acknowledge our previous communications in the literature. We point to more than a matter of priority in science, which is important in itself. Our findings suggest that prone ventilation may be beneficial in reducing ventilator-induced lung injury in all ventilated patients and this needs to be investigated in a wider context.

The Effect of Alveolar Dead Space on the Measurement of End-Expiratory Lung Volume by Modified Nitrogen Wash-Out/Wash-In in Lavage-Induced Lung Injury

The accuracy of end-expiratory lung volume measurement by the modified nitrogen wash-out/wash-in method (EELV-N(2)) depends on the precise determination of carbon dioxide elimination (V(CO(2))), which is affected by alveolar dead space (V(D-alv)). The purpose of this study was to investigate the influence of V(D-alv) on EELV-N(2). Six piglets with lavage-induced acute lung injury were mechanically ventilated in a decremental PEEP trial that was reduced from 20 to 4 cm H(2)O in steps of 4 cm H(2)O every 10 min. EELV was measured by the modified EELV-N(2) method and computed tomography scan (EELV-CT), volumetric capnography, blood gas measurements, and hemodynamic data were recorded at each PEEP level. The data were divided into higher and lower PEEP groups. During the decremental PEEP trial, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of -48.6 ± 150.7 mL (1 ± 18%). In the higher PEEP group, EELV-N(2) was not correlated with EELV-CT, with a bias of -168.1 ± 171.5 mL (-14 ± 14%). However, in the lower PEEP group, EELV-N(2) exhibited a high correlation (r(2) = 0.86, P < .001) with EELV-CT, with a bias of 11.2 ± 97.2 mL (6 ± 17%). The measurement bias was negatively correlated with V(D-alv) (r(2) = 0.44, P = .04) and V(CO(2)) (r(2) = 0.47, P = .03) in the higher PEEP group. In this surfactant-depleted model, EELV measurement by the modified EELV-N(2) method reveals a systematic underestimation at high PEEP levels that is partly due to an increase in V(D-alv).

Outcome of Adults Acute Lung Injury in High vs Low Positive End-Expiratory Pressure: Systematic Review

Background: Studies contrasting higher and lower PEEP in individuals with ALI have not been sufficiently powered to examine differences or identify subtle but potentially significant impacts on mortality. Our objective was to evaluate the association between high versus low PEEP and patient-important outcomes in individuals with ALI receiving low TVs ventilation. Method: The PRISMA statement was followed in the course of this systematic review investigation. Randomized trials that qualified for this review examined higher and lower PEEP levels in critically ill patients diagnosed with ALI. To locate relevant trials, we performed an electronic search of MEDLINE, Cochrane, and EMBASE (all from 2000 to 2011). We only included English-language randomized controlled trials. Results: Four trials yielded 2394 patients met our eligibility criteria. In the Assessment of Low TV and Elevated End-Expiratory Pressure to ALI and the Lung Open Ventilation to Reduce Mortality in the ARDS, PEEP levels were titrated to oxygenation using equivalent PEEP to FIO2 charts. The Expiratory Pressure Study's experimental strategy titrated PEEP levels based on plateau pressure data, regardless of the effect on oxygenation. Conclusion: Higher PEEP levels associated with a lower hospital death rate in patients with ARDS. Additionally, our findings suggest that this is unlikely to be beneficial for patients with less severe lung injuries; in fact, treating these patients with high PEEP levels may be harmful.

Adaptive support ventilation with and without end-tidal CO2 closed loop control versus conventional ventilation

Our aim was to compare adaptive support ventilation with and without closed loop control by end tidal CO2 (ASVCO2, ASV) with pressure (PC) and volume control ventilation (VC) during simulated clinical scenarios [normal lungs (N), COPD, ARDS, brain injury (BI)]. A lung model was used to simulate representative compliance (mL/cmH2O): resistance (cmH2O/L/s) combinations, 45:5 for N and BI, 60:7.7 for COPD, 15:7.7 and 35:7.7 for ARDS. Two levels of PEEP (cmH2O) were used for each scenario, 12/16 for ARDS, and 5/10 for others. The CO2 productions of 2, 3, 4 and 5 mL/kg predicted body weight/min were simulated. Tidal volume was set to 6 mL/kg during VC and PC. Outcomes of interest were end tidal CO2 (etCO2) and plateau pressure (P Plat). EtCO2 levels in N and BI and COPD were similar for all modes. In ARDS, etCO2 was higher in ASVCO2 than in other modes (p < 0.001). Under all mechanical conditions ASVCO2 revealed a narrower range of etCO2. P Plat was similar for all modes in all scenarios but ARDS where P Plat in ASV and ASVCO2 were lower than in VC (p = 0.001). When P Plat was ≥ 28 cmH2O, P plat in ASV and ASVCO2 were lower than in VC and PC (p = 0.024). All modes performed similarly in most cases. Minor differences observed were in favor of the closed loop modes. Overall, ASVCO2 maintained tighter CO2 control. The ASVCO2 had the greatest impact during ARDS allowing etCO2 to increase and protecting against hypocapnia evident with other modes while ensuring lower P plat and tidal volumes.

Lungenersatzverfahren – Welche Therapie für welchen Patienten? Wahl der Beatmungsstrategie im akuten Lungenversagen

Ventilator-induced lung injury (VILI) contributes to the high mortality of ALI/ARDS. Lung protective ventilation with a tidal volume of 6 ml / kgIBW (Ideal Body Weight) and a plateau pressure <30 cm H2O has shown to reduce mortality and was thus selected as one of ten quality indicators for critical care in Germany. The optimal level of PEEP is currently unclear; however, patients with severe disorders of gas exchange seem to benefit from higher PEEP levels.Adjusting the respirator settings to the mechanical properties of the individual patient will change the treatment of ARDS in the next few years. Measurements of transpulmonary pressure by an oesophageal probe or electrical impedance tomography (EIT) are promising approaches, but still need to proof their superiority. Until then, every clinician must aim to translate the recommendations of lung protective ventilation into daily practice.

Dead Space Fraction Changes During PEEP Titration Following Lung Recruitment in Patients With ARDS

Elevated dead space fraction (the ratio of dead space to tidal volume [V(D)/V(T)]) is a feature of ARDS. PEEP can partially reverse atelectasis, prevent alveoli recollapse, and improve lung compliance and gas exchange in patients with ARDS. However, whether V(D)/V(T) variables have a close relationship with PEEP and collapse alveolar recruitment remains under recognized. Meanwhile, few clinicians titrate PEEP in consideration of changes in V(D)/V(T). Therefore, we performed the study to evaluate V(D)/V(T), arterial oxygenation, and compliance changes during PEEP titration following lung recruitment in ARDS patients. Twenty-three ARDS patients ventilated in volume-controlled mode were enrolled in the study. Sustained inflation (40 cm H₂O, 30 s) was used as a recruitment maneuver, followed by decremental PEEP changes from 20 to 6 cm H₂O, in steps of 2 cm H₂O, and then to 0 cm H₂O. V(D)/V(T), pulmonary mechanics parameters, gas exchange parameters, and hemodynamic parameters were recorded after 20 min at each PEEP step. Compared with V(D)/V(T) at the PEEP levels of 20 cm H₂O and 0 cm H₂O, V(D)/V(T) was significantly lower at 12 cm H₂O (P = .02), and compliance of the static respiratory system (C(RS)) was significantly higher at pressure step 12/10 cm H₂O (P < .001). Compared with P(aCO₂) at the PEEP level of 20 cm H₂O, P(aCO₂) was significantly lower at 12 cm H₂O (P < .001). Arterial oxygenation values and functional residual capacity were reduced gradually during PEEP, decreasing from 20 cm H₂O to 0 cm H₂O. A significant change of V(D)/V(T), compliance and arterial oxygenation could be induced by PEEP titration in subjects with ARDS. Optimal PEEP in these subjects was 12 cm H₂O, because at this pressure level the highest compliance in conjunction with the lowest V(D)/V(T) indicated a maximum amount of effectively expanded alveoli. Monitoring of V(D)/V(T) was useful for detecting lung collapse and for establishing open-lung PEEP after a recruitment maneuver.

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

BackgroundAcute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART).Methods/DesignART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH2O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure ≤30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle.DiscussionIf the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Trial registrationClinicalTrials.gov Identifier: NCT01374022

Optimal Method for Selecting Peep Level in Ali/Ards Patients under Mechanical Ventilation

The PEEP in ALI/ARDS had been used since its' description (1967). Up-to-date no optimal approach to PEEP setting had been introduced, however common approaches that had been introduced included Pressure volume curves, increasing PEEP trial, decreasing PEEP trial & PEEP/FiO2 tables adopted by ARDS network. The present work assessed the safety and efficacy of three introduced approaches for PEEP setting namely increasing PEEP trial, decreasing PEEP trial and PEEP/FiO2 table. Sixty patients fulfilling the American-European Consensus Conference (AECC) criteria for ALI/ARDS were enrolled in this study, patients were randomly allocated into three equal groups (n = 20) 1, 2 & 3 using closed envelope technique. In GA: patients received an increasing PEEP trial, GB: patients received a decreasing PEEP trial and GC: PEEP was set according to PEEP/FiO2 tables of the ARDS network trial. Hemodynamic parameters (mean arterial blood pressure (MAP) and heart rate (Hr) were recorded. Respiratory & oxygenation parameters (peak airway pressure (Paw), plateau pressure (Pplat), mean airway pressure (Pmean), PEEP, PaO2, PaO2/FiO2 and arterial oxygen saturation (Sao2) were also recorded at eight specific times, prior to randomization (baseline), following PEEP setting and twice daily for 72 hours. Both increasing and decreasing PEEP trials were considered superior to PEEP/FiO2 tables in identifying desired PEEP level. Although increasing and decreasing PEEP trials had demonstrated increased PaO2, and decreased FiO2 and better PaO2/FiO2 ratios compared to baseline values, however increasing PEEP trial was associated with lower Paw and Pplat due to lower PEEP values compared to decreasing PEEP trial. Decremental trial was associated with best PaO2, FiO2, and PaOz/FiO2 compared to increasing PEEP trial and PEEP/FiO2 tables.