Positive End-expiratory Pressure Group Research Articles

Effect of Individualized PEEP Guided by Driving Pressure on Diaphragm Function in Patients Undergoing Laparoscopic Radical Resection of Colorectal Cancer: A Randomized Controlled Trial.

BACKGROUND The concept of driving pressure (ΔP) has been established to optimize mechanical ventilation-induced lung injury. However, little is known about the specific effects of setting individualized positive end-expiratory pressure (PEEP) with driving pressure guidance on patient diaphragm function. MATERIAL AND METHODS Ninety patients were randomized into 3 groups, with PEEP set to 0 in group C; 5 cmH₂O in group F; and individualized PEEP in group I, based on esophageal manometry. Diaphragm ultrasound was performed in the supine position at 6 consecutive time points from T0-T5: diaphragm excursion, end-expiratory diaphragm thickness (Tdi-ee), and diaphragm thickening fraction (DTF) were measured. Primary indicators included diaphragm excursion, Tdi-ee, and DTF at T0-T5, and the correlation between postoperative DTF and ΔP. Secondary indicators included respiratory mechanics, hemodynamic changes at intraoperative d0-d4 time points, and postoperative clinical pulmonary infection scores. RESULTS (1) Diaphragm function parameters reached the lowest point at T1 in all groups (P<0.001). (2) Compared with group C, diaphragm excursion decreased, Tdi-ee increased, and DTF was lower in groups I and F at T1-T5, with significant differences (P<0.05), but the differences between groups I and F were not significant (P>0.05). (3) DTF was significantly and positively correlated with mean intraoperative ΔP in each group at T3, and the correlation was stronger at higher levels of ΔP. CONCLUSIONS Individualized PEEP, achieved by esophageal manometry, minimizes diaphragmatic injury caused by mechanical ventilation based on lung protection, but its protection of the diaphragm during laparoscopic surgery is not superior to that of conventional ventilation strategies.

Individualized positive end-expiratory pressure reduces driving pressure in obese patients during laparoscopic surgery under pneumoperitoneum: a randomized clinical trial.

During pneumoperitoneum (PNP), airway driving pressure (ΔPRS) increases due to the stiffness of the chest wall and cephalic shift of the diaphragm, which favors atelectasis. In addition, depending on the mechanical power (MP) formulas, they may lead to different interpretations. Patients >18 years of age with body mass index >35kg/m2 were included in a single-center randomized controlled trial during their admission for bariatric surgery by abdominal laparoscopy. Intra-abdominal pressure was set at 15mmHg at the pneumoperitoneum time point (PNP). After the recruitment maneuver, the lowest respiratory system elastance (ERS) was detected during the positive end-expiratory pressure (PEEP) step-wise decrement. Patients were randomized to the 1) CTRL group: ventilated with PEEP of 5cmH2O and 2) PEEPIND group: ventilated with PEEP value associated with ERS that is 5% higher than its lowest level. Respiratory system mechanics and mean arterial pressure (MAP) were assessed at the PNP, 5min after randomization (T1), and at the end of the ventilation protocol (T2); arterial blood gas was assessed at PNP and T2. ΔPRS was the primary outcome. Three MP formulas were used: MPA, which computes static PEEP × volume, elastic, and resistive components; MPB, which computes only the elastic component; and MPC, which computes static PEEP × volume, elastic, and resistive components without inspiratory holds. Twenty-eight patients were assessed for eligibility: eight were not included and 20 patients were randomized and allocated to CTRL and PEEPIND groups (n = 10/group). The PEEPIND ventilator strategy reduced ΔPRS when compared with the CTRL group (PEEPIND, 13 ± 2cmH2O; CTRL, 22 ± 4 cmH2O; p < 0.001). Oxygenation improved in the PEEPIND group when compared with the CTRL group (p = 0.029), whereas MAP was comparable between the PEEPIND and CTRL groups. At the end of surgery, MPA and MPB were correlated in both the CTRL (rho = 0.71, p = 0.019) and PEEPIND (rho = 0.84, p = 0.020) groups but showed different bias (CTRL, -1.9J/min; PEEPIND, +10.0J/min). At the end of the surgery, MPA and MPC were correlated in both the CTRL (rho = 0.71, p = 0.019) and PEEPIND (rho = 0.84, p = 0.020) groups but showed different bias (CTRL, -1.9J/min; PEEPIND, +10.0J/min). Individualized PEEP was associated with a reduction in ΔPRS and an improvement in oxygenation with comparable MAP. The MP, which solely computes the elastic component, better reflected the improvement in ΔPRS observed in the individualized PEEP group. The protocol was registered at the Brazilian Registry of Clinical Trials (U1111-1220-7296).

Comparison of lung aeration loss in open abdominal oncologic surgeries after ventilation with electrical impedance tomography-guided PEEP versus conventional PEEP: a pilot feasibility study.

Existing literature lacks high-quality evidence regarding the ideal intraoperative positive end-expiratory pressure (PEEP) to minimize postoperative pulmonary complications (PPCs). We hypothesized that applying individualized PEEP derived from electrical impedance tomography (EIT) would reduce the severity of postoperative lung aeration loss, deterioration in oxygenation, and PPC incidence. A pilot feasibility study was conducted on 36 patients who underwent open abdominal oncologic surgery. The patients were randomized to receive individualized PEEP or conventional PEEP at 4 cm H2O. The primary outcome was the impact of individualized PEEP on changes in the modified lung ultrasound score (MLUS) derived from preoperative and postoperative lung ultrasonography. A higher MLUS indicated greater lung aeration loss. The secondary outcomes were the PaO2/FIO2 ratio and PPC incidence. A significant increase in the postoperative MLUS (12 ± 3.6 vs 7.9 ± 2.1, P < 0.001) and a significant difference between the postoperative and preoperative MLUS values (7.0 ± 3.3 vs 3.0 ± 1.6, P < 0.001) were found in the conventional PEEP group, indicating increased lung aeration loss. In the conventional PEEP group, the intraoperative PaO2/FIO2 ratios were significantly lower but not the postoperative ratios. The PPC incidence was not significantly different between the groups. Post-hoc analysis showed the increase in lung aeration loss and deterioration of intraoperative oxygenation correlated with the deviation from the individualized PEEP. Individualized PEEP appears to protect against lung aeration loss and intraoperative oxygenation deterioration. The advantage was greater in patients whose individualized PEEP deviated more from the conventional PEEP.

Maintaining moderate versus lower PEEP after cardiac surgery: a propensity-scored matched analysis

BackgroundSetting positive end-expiratory pressure (PEEP) at around 5 cm H2O in the early postoperative period seems a common practice for most patients. It remains unclear if the routine application of higher levels of PEEP confers any meaningful clinical benefit for cardiac surgical patients. The aim of this study was to compare moderate versus conventional lower PEEP on patient-centered outcomes in the intensive care unit (ICU).MethodsThis is a single-center retrospective study involving patients receiving cardiac surgery from June 2022 to May 2023. Propensity-score matching (PSM) was used to balance the baseline differences. Primary outcomes were the duration of mechanical ventilation and ICU length of stay. Secondary outcomes included PaO2/FiO2 ratio at 24 h and the need for prone positioning during ICU stay.ResultsA total of 334 patients were included in the study, 102 (31%) of them received moderate PEEP (≥ 7 cm H2O) for the major time in the early postoperative period (12 h). After PSM, 79 pairs of patients were matched with balanced baseline data. The results showed that there was marginal difference in the distribution of mechanical ventilation duration (p = 0.05) and the Moderate PEEP group had a higher extubation rate at the day of T-piece trial (65 [82.3%] vs 52 [65.8%], p = 0.029). Applying moderate PEEP was also associated with better oxygenation. No differences were found regarding ICU length of stay and patients requiring prone positioning between groups.ConclusionIn selective cardiac surgical patients, using moderate PEEP compared with conventional lower PEEP in the early postoperative period correlated to better oxygenation, which may have potential for earlier liberation of mechanical ventilation.

Effects of individualized positive end-expiratory pressure on intraoperative oxygenation in thoracic surgical patients: study protocol for a prospective randomized controlled trial

BackgroundIntraoperative hypoxemia and postoperative pulmonary complications (PPCs) often occur in patients with one-lung ventilation (OLV), due to both pulmonary shunt and atelectasis. It has been demonstrated that individualized positive end-expiratory pressure (iPEEP) can effectively improve intraoperative oxygenation, increase lung compliance, and reduce driving pressure, thereby decreasing the risk of developing PPCs. However, its effect during OLV is still unknown. Therefore, we aim to investigate whether iPEEP ventilation during OLV is superior to 5 cmH2O PEEP in terms of intraoperative oxygenation and the occurrence of PPCs.MethodsThis study is a prospective, randomized controlled, single-blind, single-center trial. A total of 112 patients undergoing thoracoscopic pneumonectomy surgery and OLV will be enrolled in the study. They will be randomized into two groups: the static lung compliance guided iPEEP titration group (Cst-iPEEP Group) and the constant 5 cmH2O PEEP group (PEEP 5 Group). The primary outcome will be the oxygenation index at 30 min after OLV and titration. Secondary outcomes are oxygenation index at other operative time points, PPCs, postoperative adverse events, ventilator parameters, vital signs, pH value, inflammatory factors, and economic indicators.DiscussionThis trial explores the effect of iPEEP on intraoperative oxygenation during OLV and PPCs. It provides some clinical references for optimizing the lung protective ventilation strategy of OLV, improving patient prognosis, and accelerating postoperative rehabilitation.Trial registrationwww.Chictr.org.cnChiCTR2300073411. Registered on 10 July 2023.

Meta-Analysis of Higher PEEP Strategies' Effects on Mortality Rates and Inflammatory Mediators in Patients with ARDS: A Perspective Review on Patients with Severe COVID-19-Associated ARDS

&lt;strong&gt;Background: &lt;/strong&gt;Different strategies of positive end-expiratory pressure (PEEP) in mechanical ventilation are crucial for patients with coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS). PEEP acts as a “double-edged sword” for ARDS patients. PEEP could recover pulmonary atelectasis but can induce alveolar hyperinflation.&lt;p&gt;&lt;strong&gt;Objective: &lt;/strong&gt;This review aimed to evaluate the effect of higher PEEP in patients with severe COVID-19-associated ARDS.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Method: &lt;/strong&gt;This meta-analysis included randomized controlled trial (RCT) studies to assess the mortality rates, barotrauma events, and inflammatory mediators modulation due to higher PEEP strategies. The pooled effect of the mortality rates and barotrauma events were presented as risk ratios (RR) with 95% confidence of interval (CI) using random-effects model (REM) or fixed-effects model (FEM).&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;We identified twelve RCTs comparing higher versus lower PEEP in ARDS patients. There was unsignificant result in overall mortality rates group [RR=0.94,95%CI(85,1.03),p=0.21] but not in mortality after positive response of oxygenation group [RR=0.88,95%CI(0.81,0.95),p=0.002] in higher PEEP group. In terms of patients without positive response of oxygenation, higher PEEP group had significantly higher mortality rates [RR=1.07,95%CI(1.00,1.15),p=0.06]. Higher PEEP significantly reduced the mortality rates in ARDS patients with PaO&lt;sub&gt;2&lt;/sub&gt;/FiO&lt;sub&gt;2&lt;/sub&gt;&amp;lt;150 mmHg [RR=0.867,95%CI(0.74,1.00),p=0.04] instead of patients with moderate ARDS (PaO&lt;sub&gt;2&lt;/sub&gt;/FiO&lt;sub&gt;2 &lt;/sub&gt;≥150 mmHg) [RR=1.12, 95%CI(0.85,1.47), p=0.44]. There were no differences in overall barotrauma events [RR=1.03,95%CI(0.78,1.36),p=0.85] between higher and lower PEEP group. The use of higher and lower PEEP also contribute to the modulation of inflammatory mediators including TNF-α, IL-6, IL-1RA, and IL-8.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;Higher PEEP could reduce the mortality of patients with ARDS who responded to the oxygenation. Higher PEEP does not increase the risk of overall barotrauma events. Higher PEEP can modulate the inflammatory mediators.&lt;/p&gt;

High versus low positive end-expiratory pressure setting in patients receiving veno-venous extracorporeal membrane oxygenation support for severe acute respiratory distress syndrome: study protocol for the multicentre, randomised ExPress SAVER Trial

IntroductionWhile limiting the tidal volume to 6 mL/kg during veno-venous extracorporeal membrane oxygenation (V-V ECMO) to ameliorate lung injury in patients with acute respiratory distress syndrome (ARDS) is widely accepted,...

Preintubation Machine-Delivered Pressure Support Ventilation With Positive End-Expiratory Pressure Versus Manual Bag-Mask Ventilation for Oxygenation in Overweight and Obese Patients: A Randomized, Pilot Study.

Noninvasive positive pressure ventilation (NIPPV) maintains mean airway pressures well, and its usability for preoxygenation is well described. Anesthesia machine-delivered NIPPV-based preoxygenation has recently been evaluated against the traditional manual bag-mask ventilation (BMV). The efficiency of such a technique over the traditional one is yet to be established well. The present study evaluated the feasibility of machine-delivered preoxygenation using pressure support ventilation (PSV) with positive end-expiratory pressure (PEEP) and compared the effectiveness with BMV. Thirty overweight and obese adults belonging to the American Society of Anesthesiologist's physical status I-II were randomized to receive PSV+PEEP or BMV for preintubation preoxygenation targeted to a fraction of expired oxygen (FeO2)of 85% and 90% or for a maximum period of five minutes, whichever came first. Postintubation, the patient was observed for the time taken until 1% desaturation without ventilation. Arterial blood gases, respiratory variables, FeO2 achieved, and different times were collected and compared. The baseline characteristics and arterial blood gases were similar between the two groups. The PSV+PEEP group had consistent and favorable tidal volume and airway pressure delivery. The difference in time to reach aFeO2 of 85% between the two groups was not statistically different. Only two patients achieved a FeO2 of 90% in the PSV+PEEP group versus none in the BMV group. However, partial pressure of oxygenat 1% desaturation (217.42±109.47 versus 138.073±71.319 mmHg, p 0.0259) was higher in thePSV+PEEP group. Similarly, the time until1% desaturation was significantly prolonged in the PSV+PEEP group (206.6±76.952 versus 140.466±54.245 seconds, p 0.0111). The present pilot study findings indicate that preintubation machine-delivered PSV+PEEP-based preoxygenation is feasible and might be more effective than traditional BMV in overweight and obese patients.

The effect intraoperative positive end expiratory pressure and tidal volume on postoperative acute kidney injury after orthopedic surgery.

To test whether higher intraoperative PEEP levels and/or higher TV levels are associated with higher incidence of postoperative AKI within the first postoperative week, in adult patients having orthopedic surgeries under general anesthesia. We conducted a sub analysis of a non-randomized alternating intervention cross over study performed in patients undergoing orthopedic surgery under general anesthesia at Cleveland Clinic, Cleveland, OH. We included four different combinations of PEEP (5 or 8 cm H2 O) and TV (6 or 10 mL/kg of PBW) that alternated each week in the six orthopedic operating rooms. Our primary outcome was postoperative AKI defined by the KDIGO criteria with baseline creatinine as the closest preoperative value to the time of surgery obtained within 30 days and postoperative value as the highest creatinine value within 7 days after surgery. Secondary outcome was the maximum postoperative in-hospital creatinine level within seven postoperative days. A total of 1933 patients were included in the analysis. The incidence of AKI was 6.8% in the study population and similar in high TV versus low TV group and high PEEP versus low PEEP group. Neither TV nor PEEP significantly impacted AKI incidence. The estimated odds ratio of AKI comparing TV = 6 mL/kg to TV = 10 mL/kg was 0.96 (97.5% CI: 0.63, 1.46; p = .811); while the estimated odds ratio of AKI comparing PEEP = 5cm H2 O to PEEP = 8cm H2 O was 0.92 (97.5% CI: 0.60, 1.39; p = .623). No interaction was found between TV and PEEP on AKI. Additionally, neither TV nor PEEP had a significant effect on the seven postoperative day creatinine levels. Higher levels of PEEP or TV during mechanical ventilation in adult patients undergoing orthopedic surgeries under general anesthesia do not increase the odds of developing postoperative AKI within the narrow limits studied.

Effect of Lung Compliance-Based Optimum Pressure Versus Fixed Positive End-Expiratory Pressure on Lung Atelectasis Assessed by Modified Lung Ultrasound Score in Laparoscopic Gynecological Surgery: A Prospective Randomized Controlled Trial.

Lung protective ventilation during the intraoperative period is now well established. However, the additional role of positive end-expiratory pressure (PEEP) during the intraoperative period remains uncertain in major laparoscopic gynecological surgery. The authors hypothesized that compliance-based optimum PEEP titration reduces postoperative lung atelectasis and improves outcomes. Patients undergoing major laparoscopic pelvic gynecological surgeries with healthy lungs were randomized to the fixed PEEP group (PEEP 5 cm H2O and recruitment maneuver {RM}) and optimum PEEP group (compliance-based PEEP and RM). Lung ultrasound and arterial blood gas analysis were performed at four time points. Modified lung ultrasound scoring was done, and the same was used as means of assessing lung aeration and the amount of lung atelectasis. Postoperative supplemental oxygen requirement and duration were also assessed and compared. Lung ultrasound score (LUS) 30 minutes after extubation in fixed (Group F) and optimum (Group O) PEEP groups were median (interquartile range {IQR}) 3 (2-3) versus 1 (1-2),p=0.0001. Ventilatory parameters between Group F and Group Oafter lung recruitmentwere tidal volume (mean357 mL {SD: 35} versus 362 mL {SD: 22}, p=0.46), PEEP (median, 5 cm H2O {IQR: 5-5} versus median 16 cm H2O {IQR: 14-18}), peak airway pressure (median 26 cm H2O {IQR: 24-28} versus median30 cm H2O {IQR: 28-32} p<0.0001), plateau pressure (median22 cm H2O {IQR: 20-24} versus median26 cm H2O {IQR: 24-28} p<0.0001), static compliance (32.07±8.36 mL cm H2O-1 versus 39.58±8.99 mL cm H2O-1, p=0.0002). The number of patients requiring postoperative oxygen therapy to maintain SpO2>94% after extubation in postanesthesia care unit (PACU) was statistically significantly greater in group F (39/41 {95%} versus 30/41 {73%}, p=0.007). Median (IQR) duration of oxygenation therapy in the first 24 hours of the postoperative period between Group F and Group O differed with statistical significance, with the median (IQR) values being 25 (20-30) minutes versus 10 (0-15) minutes (p<0.0001). The modified lung ultrasound score significantly differed intraoperatively between the two groups, with lower scores in the optimum PEEP group. This has reflected improved postoperative outcomes in optimum PEEP group patients, with fewer patients requiring postoperative oxygen supplementation and reduced supplemental oxygen requirement duration.

Lung Ultrasound to Determine the Effect of Lower vs. Higher PEEP on Lung Aeration in Patients without ARDS—A Substudy of a Randomized Clinical Trial

Background: Ventilation with lower positive end–expiratory pressure (PEEP) may cause loss of lung aeration in critically ill invasively ventilated patients. This study investigated whether a systematic lung ultrasound (LUS) scoring system can detect such changes in lung aeration in a study comparing lower versus higher PEEP in invasively ventilated patients without acute respiratory distress syndrome (ARDS). Methods: Single center substudy of a national, multicenter, randomized clinical trial comparing lower versus higher PEEP ventilation strategy. Fifty–seven patients underwent a systematic 12–region LUS examination within 12 h and between 24 to 48 h after start of invasive ventilation, according to randomization. The primary endpoint was a change in the global LUS aeration score, where a higher value indicates a greater impairment in lung aeration. Results: Thirty–three and twenty–four patients received ventilation with lower PEEP (median PEEP 1 (0–5) cm H2O) or higher PEEP (median PEEP 8 (8–8) cm H2O), respectively. Median global LUS aeration scores within 12 h and between 24 and 48 h were 8 (4 to 14) and 9 (4 to 12) (difference 1 (–2 to 3)) in the lower PEEP group, and 7 (2–11) and 6 (1–12) (difference 0 (–2 to 3)) in the higher PEEP group. Neither differences in changes over time nor differences in absolute scores reached statistical significance. Conclusions: In this substudy of a randomized clinical trial comparing lower PEEP versus higher PEEP in patients without ARDS, LUS was unable to detect changes in lung aeration.

An investigation on the respiratory mechanics of mechanically ventilated patients during spontaneous breathing trials with enhanced low-level pressure support ventilation.

Low-level pressure support ventilation (PSV) is most commonly adopted in spontaneous breathing trials (SBTs), and some have proposed setting the positive end-expiratory pressure (PEEP) to 0cmH2 O in order to shorten the observation time of SBTs. This study aims to investigate the effects of two PSV protocols on the patients' respiratory mechanics. A prospective randomized self-controlled crossover design was adopted in this study, which involved enrolling 30 difficult-to-wean patients who were admitted to the intensive care unit of the First Affiliated Hospital of Guangzhou Medical University between July 2019 and September 2021. Patients were subjected to the S group (pressure support: 8cmH2 O, PEEP: 5cmH2 O) and S1 group (PS: 8cmH2 O, PEEP: 0cmH2 O) for 30 min in a random order, and respiratory mechanics indices were dynamically monitored via a four-lumen multi-functional catheter with an integrated gastric tube. Among the 30 enrolled patients, 27 were successfully weaned. The S group showed higher airway pressure (Paw), intragastric pressure (Pga) and airway pressure-time product (PTP) than the S1 group. The S group also showed a shorter inspiratory trigger delay, (93.80 ± 47.85) versus (137.33 ± 85.66) ms (P = 0.004); and fewer abnormal triggers, (0.97 ± 2.65) versus (2.67 ± 4.48) (P = 0.042) compared with the S1 group. Stratification based on the causes of mechanical ventilation revealed that under the S1 protocol, patients with chronic obstructive pulmonary disease (COPD) had a longer inspiratory trigger delay compared to both post-thoracic surgery (PTS) patients and patients with acute respiratory distress syndrome. Despite providing greater respiratory support, S group led to significant reductions in inspiratory trigger delay and less abnormal triggers compared to S1 group, especially among patients with chronic obstructive pulmonary disease. These findings suggest that the zero PEEP group was more likely to induce a higher number of patient-ventilator asynchronies in difficult-to-wean patients.

PEEP application during mechanical ventilation contributes to fibrosis in the diaphragm

BackgroundPositive end-expiratory airway pressure (PEEP) is a potent component of management for patients receiving mechanical ventilation (MV). However, PEEP may cause the development of diaphragm remodeling, making it difficult for patients to be weaned from MV. The current study aimed to explore the role of PEEP in VIDD.MethodsEighteen adult male New Zealand rabbits were divided into three groups at random: nonventilated animals (the CON group), animals with volume-assist/control mode without/ with PEEP 8 cmH2O (the MV group/ the MV + PEEP group) for 48 h with mechanical ventilation. Ventilator parameters and diaphragm were collected during the experiment for further analysis.ResultsThere was no difference among the three groups in arterial blood gas and the diaphragmatic excursion during the experiment. The tidal volume, respiratory rate and minute ventilation were similar in MV + PEEP group and MV group. Airway peak pressure in MV + PEEP group was significantly higher than that in MV group (p < 0.001), and mechanical power was significantly higher (p < 0.001). RNA-seq showed that genes associated with fibrosis were enriched in the MV + PEEP group. This results were further confirmed on mRNA expression. As shown by Masson’s trichrome staining, there was more collagen fiber in the MV + PEEP group than that in the MV group (p = 0.001). Sirius red staining showed more positive staining of total collagen fibers and type I/III fibers in the MV + PEEP group (p = 0.001; p = 0.001). The western blot results also showed upregulation of collagen types 1A1, III, 6A1 and 6A2 in the MV + PEEP group compared to the MV group (p < 0.001, all). Moreover, the positive immunofluorescence of COL III in the MV + PEEP group was more intense (p = 0.003). Furthermore, the expression of TGF-β1, one of the most potent fibrogenic factors, was upregulated at both the mRNA and protein levels in the MV + PEEP group (mRNA: p = 0.03; protein: p = 0.04).ConclusionsWe demonstrated that PEEP application for 48 h in mechanically ventilated rabbits will cause collagen deposition and fibrosis in the diaphragm. Moreover, activation of the TGF-β1 signaling pathway and myofibroblast differentiation may be the potential mechanism of this diaphragmatic fibrosis. These findings might provide novel therapeutic targets for PEEP application-induced diaphragm dysfunction.

Effects of Individualised High Positive End-Expiratory Pressure and Crystalloid Administration on Postoperative Pulmonary Function in Patients Undergoing Robotic-Assisted Radical Prostatectomy: A Prospective Randomised Single-Blinded Pilot Study

Robotic-assisted laparoscopic prostatectomy (RALP) is typically conducted in steep Trendelenburg position (STP). The aim of the study was to evaluate whether crystalloid administration and individual management of positive end-expiratory pressure (PEEP) improve peri- and post-operative pulmonary function in patients undergoing RALP. Prospective randomised single-centre single-blinded explorative study. Patients were either allocated to a standard PEEP (5 cmH2O) group or an individualised high PEEP group. Furthermore, each group was divided into a liberal and a restrictive crystalloid group (8 vs. 4 mL/kg/h predicted body weight). Individualised PEEP levels were determined by means of preoperative recruitment manoeuvre and PEEP titration in STP. Informed consent was obtained from 98 patients scheduled for elective RALP. The following intraoperative parameters were analysed in each of the four study groups: ventilation setting (peak inspiratory pressure [PIP], plateau pressure, driving pressure [Pdriv], lung compliance [LC] and mechanical power [MP]) and postoperative pulmonary function (bed-side spirometry). The spirometric parameters Tiffeneau index (FEV1/FVC ratio) and mean forced expiratory flow (FEF25-75) were measured pre- and post-operatively. Data are shown as mean ± standard deviation (SD), and groups were compared with ANOVA. A p-value of <0.05 was considered significant. The two individualised high PEEP groups (mean PEEP 15.5 [±1.71 cmH2O]) showed intraoperative significantly higher PIP, plateau pressure and MP levels but significantly decreased Pdriv and increased LC. On the first and second postoperative day, patients with individualised high PEEP levels had a significantly higher mean Tiffeneau index and FEF25-75. Perioperative oxygenation and ventilation and postoperative spirometric parameters were not influenced by restrictive or liberal crystalloid infusion in either of the two respective PEEP groups. Individualised high PEEP levels (≥14 cmH2O) during RALP improved intraoperative blood oxygenation and resulted in more lung-protective ventilation. Furthermore, postoperative pulmonary function was improved for up to 48 h after surgery in the sum of the two individualised high PEEP groups. Restrictive crystalloid infusion during RALP seemed to have no effect on peri- and post-operative oxygenation and pulmonary function.

Effect of recruitment manoeuvres under lung ultrasound-guidance and positive end-expiratory pressure on postoperative atelectasis and hypoxemia in major open upper abdominal surgery: A randomized controlled trial

BackgroundPostoperative pulmonary complications (PPCs) especially atelectasis and hypoxemia are common during abdominal surgery. Studies on the effect of either recruitment manoeuvres (RMs) or positive end-expiratory pressure (PEEP) on PPCs are controversial. The objective of this study is to evaluate the effect of perioperative lung ultrasound (LUS)-guided RMs combined with PEEP on the reduction of postoperative atelectasis and hypoxemia in major open upper abdominal surgery. MethodsIn this randomized controlled trial, 122 adult patients undergoing major open upper abdominal surgery were allocated into three groups: control (C) group (n = 42); PEEP (P) group (n = 40); RMs combined with PEEP (RP) group (n = 40). All patients were scheduled for general anaesthesia using the lung-protective ventilation (LPV) strategy. The levels of PEEP in the three groups were 0 cmH2O, 5 cmH2O and 5 cmH2O. LUS examination was carried out at 3 predetermined time points in each group: 5 min after intubation (T1), at the end of surgery (T2) and 15 min after extubation (T3). Patients with atelectasis on the sonogram in the RP group received LUS-guided RMs at point T2. LUS scores were used to estimate the severity of aeration loss. The P/F ratio (PaO2/FiO2) at 15min after extubation was used to assess the incidence of postoperative hypoxemia. Primary outcomes were the incidences of postoperative atelectasis and hypoxemia (PaO2/FiO2 < 300 mmHg). The secondary outcome was the distribution of LUS scores in each lung area. ResultsFrom July 2021 to December 2021, 122 consecutive patients were enrolled. No typical atelectasis was observed 5 min after intubation. The incidence of atelectasis was 52.4%, 50.0% and 42.5% in the C group, P group and RP group at the end of surgery, respectively. The rate of atelectasis in the C group, P group and RP group (after RMs) was 52.4%, 50.0% and 17.5%, respectively, 15 min after extubation (P < 0.01). The frequency of postoperative hypoxemia was 27.5%, 15.0% and 5.0% in the C group, P group and RP group, respectively (P < 0.017). The increased LUS scores mainly occurred in the superoposterior and inferoposterior quadrants at the end of surgery. Only in the RP group demonstrated a decreased LUS score in the posteriorquadrants after extubation. ConclusionsIn patients undergoing major open upper abdominal surgery, an intraoperative mechanical ventilation strategy without PEEP or with PEEP alone did not reduce PPCs. However, PEEP of 5 cmH2O combined with LUS-guided RMs proved feasible and beneficial to decrease the occurrence of postoperative atelectasis and hypoxemia in major open upper abdominal surgeries.

Individualized positive end-expiratory pressure guided by respiratory mechanics during anesthesia for the prevention of postoperative pulmonary complications: a systematic review and meta-analysis.

The optimization of positive end-expiratory pressure (PEEP) according to respiratory mechanics [driving pressure or respiratory system compliance (Crs)] is a simple and straightforward strategy. However, its validity to prevent postoperative pulmonary complications (PPCs) remains unclear. Here, we performed a meta-analysis to assess such efficacy. We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared personalized PEEP based on respiratory mechanics and constant PEEP to prevent PPCs in adults. The primary outcome was PPCs. Fourteen studies with 1105 patients were included. Compared with those who received constant PEEP, patients who received optimized PEEP exhibited a significant reduction in the incidence of PPCs (RR = 0.54, 95% CI 0.42 to 0.69). The results of commonly happened PPCs (pulmonary infections, hypoxemia, and atelectasis but not pleural effusion) also supported individualized PEEP group. Moreover, the application of PEEP based on respiratory mechanics improved intraoperative respiratory mechanics (driving pressure and Crs) and oxygenation. The PEEP titration method based on respiratory mechanics seems to work positively for lung protection in surgical patients undergoing general anesthesia.

Impact of positive end-expiratory pressure with alveolar recruitment maneuver on respiratory and oxygenation parameters of patients during laparoscopic bariatric surgery.

Laparoscopic bariatric surgery is frequently associated with disturbances in respiratory mechanics. An alveolar recruitment maneuver (ARM) with positive end-expiratory pressure (PEEP) is a strategy to overcome such respiratory conditions. This study aimed to evaluate the effect of ARM+PEEP on intraoperative and postoperative respiratory and hemodynamic parameters of patients with laparoscopic bariatric surgery. Patients who underwent laparoscopic bariatric surgery between 2009 and 2016 were retrospectively evaluated. The study sample was divided into four groups based on PEEP values and the presence of ARM: Group PEEP 5 (5 cm H2O PEEP only), Group PEEP 5/RM (5 cm H2O PEEP plus ARM), Group PEEP 10 (10 cm H2O PEEP only), Group PEEP 10/RM (10 cm H2O PEEP plus ARM). Patients' demographic characteristics, ventilatory, respiratory, and oxygenation parameters were recorded. Oxygenation index (PaO2/FiO2) was the study's primary outcome. There were 156, 158, 299, and 210 patients in Groups PEEP 5, PEEF 5/RM, PEEP 10, and PEEP 10/RM, respectively. Tidal volume, driving tidal volume/compliance, PaO2, PaO2/FiO2, and PaCO2 were significantly lower in Groups PEEP 5 and PEEP 5/RM, whereas SpO2 and FiO2 were significantly higher in Groups PEEP 5 and PEEP 5/RM (p<0.05). Patients in Group PEEP 5 had significantly higher end-tidal carbon dioxide (EtCO2) values than those of other groups (p<0.001). Patients in Group PEEP 5/RM had significantly higher SpO2 values than those in Group PEEP 5 (p<0.001). Rate of postoperative atelectasis was significantly higher in Group PEEP 5/RM compared to the other groups (p=0.011). A PEEP level of at least 10 cm H2O with ARM improved intraoperative respiratory parameters and caused a significant reduction in postoperative atelectasis.

Ventilator hyperinflation – what settings generate an expiratory flow rate bias?

ObjectivesTo determine which mechanical ventilation settings influence the attainment of expiratory flow rate characteristics that may promote secretion mobilisation during ventilator hyperinflation (VHI). DesignProspective, single centre study. SettingIntensive care unit, tertiary metropolitan hospital. ParticipantsTwenty-four patients receiving mechanical ventilation. InterventionsPatients were recruited to either a low PEEP or high PEEP group (5–9 cmH2O or 10–15 cmH2O PEEP respectively). Each group had three hyperinflation protocols applied. Main outcome measuresPeak inspiratory flow rates (PIFR) and peak expiratory flow rates (PEFR) were measured and reported as PIFR/PEFR of less than or equal to 0.9; a PEFR-PIFR greater than or equal to 33 L/min; and PEFR greater than or equal to 40 L/min. ResultsIn both the low and high PEEP groups, VHI protocols using volume-controlled ventilation were significantly better at generating expiratory flow rate bias compared to pressure-controlled or Pressure Support ventilation. An expiratory flow rate bias was also achieved when VHI was performed in volume-controlled ventilation with either a peak inspiratory pressure target of 35 cmH2O or a driving pressure of 20 cmH2O. Median heart rate and blood pressure values did not change during VHI, but transient reductions in blood pressure were present in six participants (25%). ConclusionsVHI performed using volume-controlled ventilation was more effective than pressure-controlled or Pressure Support ventilation to generate an expiratory flow rate bias. Contribution of the PaperMechanical ventilator settings can be altered to perform hyperinflation and achieve expiratory flow rate properties that may increase the mobilisation of airway secretions. The results demonstrate that to achieve these properties:•Volume-controlled ventilation appears superior to pressure-controlled and Pressure Support ventilation.•Delivering volume-controlled breaths to a volume that result in a peak pressure of 35 cmH2O or using a driving pressure of 20 cmH2O appear to be equally effective.•Limiting the change in pressure to 20 cmH2O results in significantly lower tidal volumes and may still be effective for airway clearance in people on mechanical ventilation with either high or low PEEP.

Association between driving pressure and postoperative pulmonary complications in patients undergoing lung resection surgery: A randomised clinical trial

BackgroundIt is uncertain whether an association exists for decreases in driving pressure and the occurrence of postoperative pulmonary complications (PPCs) in patients undergoing selective lung resection surgery. Thus, we designed this study to determine whether the positive end-expiratory pressure (PEEP) titration to the lowest driving pressure compared with conventional low PEEP level during one-lung ventilation (OLV) in patients undergoing selective lung resection surgery decreases PPCs. MethodsThis single-centre, randomised trial approved by the Ethical Committee of the Sun Yat-Sen University Cancer Center involved patients who signed written consent. Patients were randomised to the PEEP titration to the lowest driving pressure group (n = 104), or to the conventional low level of PEEP group (n = 103), consisting a PEEP level of 4 cm H2O during OLV. All patients received volume-controlled ventilation with a tidal volume of 6 mL/kg of predicted body weight. The primary outcome was defined as positive if 4 or more of eight Melbourne Group Scale (MGS) variables developed within the first 3 days after surgery. The incidence of major PPCs occurring during postoperative 7 days was also recorded. ResultsAmong 222 patients who were randomised, 207 (93%) completed the trial (109 men [53%]; mean age, 56.9 years). The primary outcome occurred in 4 of 104 patients (4%) in the PEEP titration to the lowest driving pressure group compared with 13 of 103 patients (13%) in the conventional low level of PEEP group (risk ratio, 0.32 [95% CI, 0.10−0.90]; P = 0.021). ConclusionsAmong patients undergoing selective lung surgery, intraoperative OLV with PEEP titration to the lowest driving pressure compared with conventional low PEEP level (4 cm H2O) significantly reduced PPCs within the first 3 postoperative days, however, did not significantly reduce PPCs within the first 7 postoperative days.

Effects of Positive End-Expiratory Pressure on Intraocular Pressure during One-Lung Ventilation in the Lateral Decubitus Position-A Prospective Randomized Trial.

Background and Objectives: The effect of positive end-expiratory pressure (PEEP) on intraocular pressure (IOP) is debatable. There have been no studies investigating the effects of PEEP on IOP during one-lung ventilation (OLV). We aimed to investigate the effects of PEEP on IOP in patients undergoing OLV for video-assisted thoracoscopic surgery (VATs). Materials and Methods: Fifty-two patients undergoing VATs were divided into a zero-PEEP (ZEEP) and a 6 cmH2O of PEEP (PEEP) groups. IOP, ocular perfusion pressure (OPP), and respiratory and hemodynamic parameters were measured before induction (T1), immediately following endotracheal intubation (T2), 30 min (T3) and 60 min (T4) after a position change to the lateral decubitus position (LDP) and OLV, and 10 min following two-lung ventilation near the end of the surgery (T5). Results: There was no significant difference in IOP and OPP between the two groups. The IOP of the dependent eye was significantly higher than that of the non-dependent eye during LDP in both groups. Peak inspiratory pressure was significantly higher in the PEEP group than in the ZEEP group at T3–T5. Dynamic compliance was significantly higher in the PEEP group than in the ZEEP group at T2–T5. The ratio of arterial oxygen partial pressure to fractional inspired oxygen was significantly higher in the PEEP group than in the ZEEP group at T4. Conclusions: Applying 6 cmH2O of PEEP did not increase IOP but enhanced dynamic compliance and oxygenation during OLV. These results suggest that 6 cmH2O of PEEP can be safely applied during OLV in LDP.