Conventional Protective Ventilation Research Articles

Low-Frequency Ventilation May Facilitate Weaning in Acute Respiratory Distress Syndrome Treated with Extracorporeal Membrane Oxygenation: A Randomized Controlled Trial.

Although extracorporeal membrane ventilation offers the possibility for low-frequency ventilation, protocols commonly used in patients with acute respiratory distress syndrome (ARDS) and treated with extracorporeal membrane oxygenation (ECMO) vary largely. Whether strict adherence to low-frequency ventilation offers benefit on important outcome measures is poorly understood. Background/Objectives: This pilot clinical study investigated the efficacy of low-frequency ventilation on ventilator-free days (VFDs) in patients suffering from ARDS who were treated with ECMO therapy. Methods: In this single-center randomized controlled trial, 44 (70% male) successive ARDS patients treated with ECMO (aged 56 ± 12 years, SAPS III 64 (SD ± 14)) were randomly assigned 1:1 to the control group (conventional ventilation) or the treatment group (low-frequency ventilation during first 72 h on ECMO: respiratory rate 4-5/min; PEEP 14-16 cm H2O; plateau pressure 23-25 cm H2O, tidal volume: <4 mL/kg). The primary endpoint was VFDs at day 28 after starting ECMO treatment. The major secondary endpoint was ICU mortality, 28-day mortality and 90-day mortality. Results: Twenty-three (52%) patients were successfully weaned from ECMO and were discharged from the intensive care unit (ICU). Twelve patients in the treatment group and five patients in the control group showed more than one VFD at day 28 of ECMO treatment. VFDs were 3.0 (SD ± 5.5) days in the control group and 5.4 (SD ± 6) days in the treatment group (p = 0.117). Until day 28 of ECMO initiation, patients in the treatment group could be successfully weaned off of the ventilator more often (OR of 0.164 of 0 VFDs at day 28 after ECMO start; 95% CI 0.036-0.758; p = 0.021). ICU mortality did not differ significantly (36% in treatment group and 59% in control group; p = 0.227). Conclusions: Low-frequency ventilation is comparable to conventional protective ventilation in patients with ARDS who have been treated with ECMO. However, low-frequency ventilation may support weaning from invasive mechanical ventilation in patients suffering from ARDS and treated with ECMO therapy.

Open lung approach versus conventional protective ventilation in obese patients undergoing open abdominal surgery: a randomized controlled trial

Purpose Open abdominal surgeries are associated with an increased risk of postoperative pulmonary complications, especially in obese patients, which seem to be related directly to intraoperative mechanical ventilation. The present study aimed to compare the effect of using conventional protective ventilation (CPV) [low tidal volume and fixed positive end expiratory pressure (PEEP)] with open lung approach (OLA) (recruitment maneuver followed by personalized PEEP) on postoperative pulmonary complications. Patients and methods A total of 56 obese patients undergoing open abdominal surgery under general anesthesia were enrolled and randomly assigned to either the CPV group in which they received a tidal volume of 7 ml/kg with fixed PEEP level of 5 cmH2O or the OLA group in which they had alveolar recruitment maneuver followed by individualized PEEP. The primary outcome was the early postoperative pulmonary complications during the first 5 days after surgery. Secondary outcomes included lung mechanics, gas exchange, and hemodynamics during the intraoperative period as well as length of hospital stay, postoperative extrapulmonary complications, and intrahospital mortality. Results Postoperative pulmonary complications in the first 5 days were significantly higher in the CPV than in the OLA group. During the intraoperative period, the static compliance, the PEEP, and plateau pressure were significantly higher in the OLA group than the CPV group. On the contrary, driving pressure was significantly lower in the OLA group. Better oxygenation was observed in the OLA group in the intraoperative period and postoperative days 1 and 3. Pulmonary function tests were significantly better among patients who received the OLA on the first and third postoperative days. Conclusion The OLA may be used as an acceptable alternative to CPV as it was associated with less postoperative pulmonary complications, better intraoperative and postoperative oxygenation, and better postoperative pulmonary functions.

Driving pressure-guided ventilation and postoperative pulmonary complications in thoracic surgery: a multicentre randomised clinical trial

BackgroundAirway driving pressure, easily measured as plateau pressure minus PEEP, is a surrogate for alveolar stress and strain. However, the effect of its targeted reduction remains unclear. MethodsIn this multicentre trial, patients undergoing lung resection surgery were randomised to either a driving pressure group (n=650) receiving an alveolar recruitment/individualised PEEP to deliver the lowest driving pressure or to a conventional protective ventilation group (n=650) with fixed PEEP of 5 cm H2O. The primary outcome was a composite of pulmonary complications within 7 days postoperatively. ResultsThe modified intention-to-treat analysis included 1170 patients (mean [standard deviation, sd]; age, 63 [10] yr; 47% female). The mean driving pressure was 7.1 cm H2O in the driving pressure group vs 9.2 cm H2O in the protective ventilation group (mean difference [95% confidence interval, CI]; −2.1 [−2.4 to −1.9] cm H2O; P<0.001). The incidence of pulmonary complications was not different between the two groups: driving pressure group (233/576, 40.5%) vs protective ventilation group (254/594, 42.8%) (risk difference −2.3%; 95% CI, −8.0% to 3.3%; P=0.42). Intraoperatively, lung compliance (mean [sd], 42.7 [12.4] vs 33.5 [11.1] ml cm H2O−1; P<0.001) and Pao2 (median [inter-quartile range], 21.5 [14.5 to 30.4] vs 19.5 [13.5 to 29.1] kPa; P=0.03) were higher and the need for rescue ventilation was less frequent (6.8% vs 10.8%; P=0.02) in the driving pressure group. ConclusionsIn lung resection surgery, a driving pressure-guided ventilation improved pulmonary mechanics intraoperatively, but did not reduce the incidence of postoperative pulmonary complications compared with a conventional protective ventilation. Clinical trial registrationNCT04260451.

Effects of Driving Pressure-Guided Ventilation on Postoperative Pulmonary Complications in Prone-Positioned Patients Undergoing Spinal Surgery: A Randomized Controlled Clinical Trial

Background Prolonged spinal surgery in the prone position may lead to postoperative pulmonary complications (PPCs). We aimed to compare the effects of driving pressure-guided ventilation versus conventional protective ventilation on postoperative pulmonary complications in patients undergoing spinal surgery in the prone position. We hypothesized that driving pressure-guided ventilation would be associated with a decreased incidence of PPC. Methods We enrolled 78 patients into this single-center, double-blind, randomized controlled trial. The driving pressure (DP) group (n = 40) received a tidal volume of 6 ml/kg of predicted body weight, individualized positive end-expiratory pressure (PEEP) which produced the lowest driving pressure (plateau pressure-PEEP), and a recruitment maneuver. The protective ventilation (PV) group (n = 38) received the same tidal volume and recruitment maneuver but with a fixed PEEP of 5 cm H2O. Our primary outcome was postoperative pulmonary complications based on Lung Ultrasound Scores (LUS) at the end of the surgery and the simplified Clinical Pulmonary Infection Score (sCPIS) on postoperative days (POD) 1 and 3. Results DP patients had lower LUS and POD1 sCPIS than the PV group (p < 0.01). DP patients had lower driving pressure during the surgery than PV patients (p < 0.01). Perioperative arterial blood gases and hemodynamic parameters were comparable between the two groups (p > 0.05). The visual pain score (VAS) in postoperative days, drainage, and lengths of stay (LOS) were also similar between the two groups (p > 0.05). Conclusions Driving pressure-guided ventilation during spinal surgery with a prolonged prone patient position may reduce the incidence of early postoperative pulmonary complications, compared with conventional protective ventilation.

Time-Controlled Adaptive Ventilation Does Not Induce Hemodynamic Impairment in a Swine ARDS Model.

BackgroundThe current standard of care during severe acute respiratory distress syndrome (ARDS) is based on low tidal volume (VT) ventilation, at 6 mL/kg of predicted body weight. The time-controlled adaptive ventilation (TCAV) is an alternative strategy, based on specific settings of the airway pressure release ventilation (APRV) mode. Briefly, TCAV reduces lung injury, including: (1) an improvement in alveolar recruitment and homogeneity; (2) reduction in alveolar and alveolar duct micro-strain and stress-risers. TCAV can result in higher intra-thoracic pressures and thus impair hemodynamics resulting from heart-lung interactions. The objective of our study was to compare hemodynamics between TCAV and conventional protective ventilation in a porcine ARDS model.MethodsIn 10 pigs (63–73 kg), lung injury was induced by repeated bronchial saline lavages followed by 2 h of injurious ventilation. The animals were then randomized into two groups: (1) Conventional protective ventilation with a VT of 6 mL/kg and PEEP adjusted to a plateau pressure set between 28 and 30 cmH2O; (2) TCAV group with P-high set between 27 and 29 cmH2O, P-low at 0 cmH2O, T-low adjusted to terminate at 75% of the expiratory flow peak, and T-high at 3–4 s, with I:E > 6:1.ResultsBoth lung elastance and PaO2:FiO2 were consistent with severe ARDS after 2 h of injurious mechanical ventilation. There was no significant difference in systemic arterial blood pressure, pulmonary blood pressure or cardiac output between Conventional protective ventilation and TCAV. Levels of total PEEP were significantly higher in the TCAV group (p < 0.05). Driving pressure and lung elastance were significantly lower in the TCAV group (p < 0.05).ConclusionNo hemodynamic adverse events were observed in the TCAV group compared as to the standard protective ventilation group in this swine ARDS model, and TCAV appeared to be beneficial to the respiratory system.

Use of Almitrine and Inhaled Nitric Oxide in ARDS Due to COVID-19.

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is manifested by an acute respiratory distress syndrome (ARDS) with intense inflammation and endothelial dysfunction leading to particularly severe hypoxemia. We hypothesized that an impaired hypoxic pulmonary vasoconstriction aggravates hypoxemia. The objective of the study was to test the effect of two pulmonary vasoactive drugs on patient oxygenation.Methods: Observational, single-center, open-label study in one intensive care unit (ICU) of the Paris area, realized in April 2020. Eligible patients had coronavirus disease 2019 (COVID-19) and moderate to severe ARDS [arterial partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2) <200 mmHg] despite conventional protective ventilation. Exclusion criteria included pulmonary artery hypertension defined by a pulmonary artery systolic pressure (PAPs) >45 mmHg. The assessment of oxygenation was based on PaO2/FiO2 at (1) baseline, then after (2) 30 min of inhaled nitric oxide (iNO) 10 ppm alone, then (3) 30 min combination of iNO + almitrine infusion 8 μg/kg/min, then (4) 30 min of almitrine infusion alone.Results: Among 20 patients requiring mechanical ventilation during the study period, 12 met the inclusion criteria. Baseline PaO2/FiO2 was 146 ± 48 mmHg. When iNO was combined with almitrine, PaO2/FiO2 rose to 255 ± 90 mmHg (+80 ± 49%, p = 0.005), also after almitrine alone: 238 ± 98 mmHg (+67 ± 75%, p = 0.02), but not after iNO alone: 185 ± 73 mmHg (+30 ± 5%, p = 0.49). No adverse events related to almitrine infusion or iNO was observed.Conclusion: Combining iNO and infused almitrine improved the short-term oxygenation in patients with COVID-19-related ARDS. This combination may be of interest when first-line therapies fail to restore adequate oxygenation. These findings argue for an impaired pulmonary hypoxic vasoconstriction in these patients.

Early signs of right ventricular systolic and diastolic dysfunction in acute severe respiratory failure: the importance of diastolic restrictive pattern.

Background:The incidence and pathophysiology of right ventricular failure in patients with severe respiratory insufficiency has been largely investigated. However, there is a lack of early signs suggesting right ventricular systolic and diastolic dysfunction prior to acute cor pulmonale development.Methods:We conducted a retrospective analytical cohort study of patients for acute respiratory distress syndrome undertaking an echocardiography during admission in the cardiothoracic intensive care unit. Patients were divided according to treatment: conventional protective ventilation (38 patients, 38%); interventional lung assist (23 patients, 23%); veno-venous extracorporeal membrane oxygenation (37 patients, 37%). Systolic and diastolic function was studied assessing, respectively: right ventricular systolic longitudinal function (tricuspid annular plane systolic excursion) and systolic contraction duration (tricuspid annular plane systolic excursion length); right ventricular diastolic filling time and right ventricular diastolic restrictive pattern (presence of pulmonary valve presystolic ejection wave). Correlation between the respiratory mechanics and systo-diastolic parameters were analysed.Results:In 98 patients studied, systolic dysfunction (tricuspid annular plane systolic excursion <16 mm) was present in 33.6% while diastolic restrictive pattern was present in 64%. A negative correlation was found between tricuspid annular plane systolic excursion and tricuspid annular plane systolic excursion length (P<0.0001; r −0.42). Tricuspid annular plane systolic excursion and tricuspid annular plane systolic excursion length correlated with right ventricular diastolic filling time (P<0.001; r −0.39). Pulmonary valve presystolic ejection wave was associated with tricuspid annular plane systolic excursion (P<0.0001), tricuspid annular plane systolic excursion length (P<0.0001), right ventricular diastolic filling time (P<0.0001), positive end-expiratory pressure (P<0.0001) and peak inspiratory pressure (P<0.0001).Conclusion:Diastolic restrictive pattern is present in a remarkable percentage of patients with respiratory distress syndrome. Bedside echocardiography allows a mechanistic evaluation of systolic and diastolic interaction of the right ventricle.

Effects of Intraoperative Ventilation Strategy on Perioperative Atelectasis Assessed by Lung Ultrasonography in Patients Undergoing Open Abdominal Surgery: a Prospective Randomized Controlled Study.

BackgroundProtective mechanical ventilation using low tidal volume has been introduced to surgical patients to reduce the incidence of postoperative pulmonary complications. We investigated the effects of protective ventilation (PV) techniques on anesthesia-induced atelectasis identified via lung ultrasonography in patients undergoing abdominal surgery.MethodsA total of 42 adult patients who were scheduled for open abdominal surgery with an expected duration > 2 hours were included in the study. Patients were randomized to receive either conventional ventilation (CV; tidal volume of 9–10 mL/kg predicted body weight [PBW] with no positive end-expiratory pressure [PEEP]) or PV (tidal volume of 6–8 mL/kg PBW and 5 cmH2O PEEP) via pressure-controlled ventilation with volume guaranteed. Lung ultrasonography was performed at four predefined time points to assess perioperative atelectasis by dividing each hemithorax into six quadrants based on a modified lung ultrasound (LUS) scoring system.ResultsThe tidal volume delivered to patients was 9.65 ± 1.65 mL/kg PBW in the CV group and 6.31 ± 0.62 mL/kg PBW in the PV group. Ventilation using low tidal volume led to similar LUS scores in all lung areas and at all time points compared to ventilation using high tidal volume. There was no significant difference between the groups in the number of patients requiring recruitment maneuvers at the end of surgery.ConclusionVentilation with low tidal volume combined with 5 cmH2O PEEP did not cause further loss of aeration compared to ventilation with high tidal volume. Low tidal volume ventilation can be used in patients without lung injury based on lung assessment by bedside lung ultrasonography.Trial RegistrationClinical Research Information Service Identifier: KCT0003746

Driving Pressure during Thoracic Surgery: A Randomized Clinical Trial.

Driving pressure (plateau minus end-expiratory airway pressure) is a target in patients with acute respiratory distress syndrome, and is proposed as a target during general anesthesia for patients with normal lungs. It has not been reported for thoracic anesthesia where isolated, inflated lungs may be especially at risk. In a double-blinded, randomized trial (292 patients), minimized driving pressure compared with standard protective ventilation was associated with less postoperative pneumonia or acute respiratory distress syndrome. Recently, several retrospective studies have suggested that pulmonary complication is related with driving pressure more than any other ventilatory parameter. Thus, the authors compared driving pressure-guided ventilation with conventional protective ventilation in thoracic surgery, where lung protection is of the utmost importance. The authors hypothesized that driving pressure-guided ventilation decreases postoperative pulmonary complications more than conventional protective ventilation. In this double-blind, randomized, controlled study, 292 patients scheduled for elective thoracic surgery were included in the analysis. The protective ventilation group (n = 147) received conventional protective ventilation during one-lung ventilation: tidal volume 6 ml/kg of ideal body weight, positive end-expiratory pressure (PEEP) 5 cm H2O, and recruitment maneuver. The driving pressure group (n = 145) received the same tidal volume and recruitment, but with individualized PEEP which produces the lowest driving pressure (plateau pressure-PEEP) during one-lung ventilation. The primary outcome was postoperative pulmonary complications based on the Melbourne Group Scale (at least 4) until postoperative day 3. Melbourne Group Scale of at least 4 occurred in 8 of 145 patients (5.5%) in the driving pressure group, as compared with 18 of 147 (12.2%) in the protective ventilation group (P = 0.047, odds ratio 0.42; 95% CI, 0.18 to 0.99). The number of patients who developed pneumonia or acute respiratory distress syndrome was less in the driving pressure group than in the protective ventilation group (10/145 [6.9%] vs. 22/147 [15.0%], P = 0.028, odds ratio 0.42; 95% CI, 0.19 to 0.92). Application of driving pressure-guided ventilation during one-lung ventilation was associated with a lower incidence of postoperative pulmonary complications compared with conventional protective ventilation in thoracic surgery.

A perioperative surgeon-controlled open-lung approach versus conventional protective ventilation with low positive end-expiratory pressure in cardiac surgery with cardiopulmonary bypass (PROVECS): study protocol for a randomized controlled trial

BackgroundPostoperative pulmonary complications (PPCs) are frequent after on-pump cardiac surgery. Cardiac surgery results in a complex pulmonary insult leading to high susceptibility to perioperative pulmonary atelectasis. For technical reasons, ventilator settings interact with the surgical procedure and traditionally, low levels of positive end-expiratory pressure (PEEP) have been used. The objective is to compare a perioperative, multimodal and surgeon-controlled open-lung approach with conventional protective ventilation with low PEEP to prevent PPCs in patients undergoing cardiac surgery.Methods/designThe perioperative open-lung protective ventilation in cardiac surgery (PROVECS) trial is a multicenter, two-arm, randomized controlled trial. In total, 494 patients scheduled for elective cardiac surgery with cardiopulmonary bypass (CPB) and aortic cross-clamp will be randomized into one of the two treatment arms. In the experimental group, systematic recruitment maneuvers and perioperative high PEEP (8 cmH2O) are associated with ultra-protective ventilation during CPB. In this group, the settings of the ventilator are controlled by surgeons in relation to standardized protocol deviations. In the control group, no recruitment maneuvers, low levels of PEEP (2 cmH2O) and continuous positive airway pressure during CPB (2 cmH2O) are used. Low tidal volumes (6–8 mL/kg of predicted body weight) are used before and after CPB in each group. The primary endpoint is a composite of the single PPCs evaluated during the first 7 postoperative days.DiscussionThe PROVECS trial will be the first multicenter randomized controlled trial to evaluate the impact of a perioperative and multimodal open-lung ventilatory strategy on the occurrence of PPCs after on-pump cardiac surgery. The trial design includes standardized surgeon-controlled protocol deviations that guarantee a pragmatic approach. The results will help anesthesiologists and surgeons aiming to optimize ventilatory settings during cardiac surgery.Trial registrationClinical Trials.gov, NCT 02866578. Registered on 15 August 2016. Last updated 11 July 2017.

A novel risk score for severe ARDS patients undergoing ECMO after retrieval from peripheral hospitals.

Extracorporeal Membrane Oxygenation in severe ARDS unresponsive to conventional protective ventilation is associated with elevated costs, resource and complications, and appropriate risk stratification of candidate patients could be useful to recognize those more likely to benefit from ECMO. We aimed to derive a new outcome prediction score for patientsretrieved by our ECMO team from peripheral centers, including systematic echocardiographic evaluation before ECMO start. Sixty-nine consecutive patients with refractory ARDS requiring ECMO transferred from peripheral centers to our ICU (a tertiary ECMO referral center), from 1 October 2009 to 31 December 2015, were assessed. All patients were transported on ECMO (distance, median 77, range 4-456km) The mortality rate was 41% (28/69). Our new risk score included age ≥42years, BMI <31kg/m2 , RV dilatation, and pH <7.35. The proposed cut off (Youden's index method) of nine had a sensitivity of 96% and a specificity of 30% (AUC-ROC: 0.85, 95% CI: 0.76-0.94, P<0.001). When assessing the discriminatory ability of our risk score in the population of local patients, survivors had a mean value of 15.4±8.6, whereas non-survivors showed a mean value of 20.1±7.4 (P<0.001). Our new risk score shows good discriminatory ability both in patients retrieved from peripheral centers and in those implanted at our center. This score includes variables easily available at bedside, and, for the first time, a pathophysiologic element, RV dilatation.

Is high-frequency oscillatory ventilation more effective and safer than conventional protective ventilation in adult acute respiratory distress syndrome patients? A meta-analysis of randomized controlled trials.

IntroductionComprehensively evaluating the efficacy and safety of high-frequency oscillatory ventilation (HFOV) is important to allow clinicians who are using or considering this intervention to make appropriate decisions.MethodsTo find randomized controlled trials (RCTs) comparing HFOV with conventional mechanical ventilation (CMV) as an initial treatment for adult ARDS patients, we searched electronic databases (including PubMed, MedLine, Springer Link, Elsevier Science Direct, ISI web of knowledge, and EMBASE) with the following terms: “acute respiratory distress syndrome”, “acute lung injury”, and “high frequency oscillation ventilation”. Additional sources included reference lists from the identified primary studies and relevant meta-analyses. Two investigators independently screened articles and extracted data. Meta-analysis was conducted using random-effects models.ResultsWe included 6 RCTs with a total of 1,608 patients in this meta-analysis. Compared with CMV, HFOV did not significantly reduce the mortality at 30 or 28 days. The pooled relative risk (RR) was 1.051 (95% confidence interval (CI) 0.813 to 1.358). ICU mortality was also not significantly reduced in HFOV group, with a pooled RR of 1.218 (95% CI 0.925 to 1.604). The pooled effect sizes of HFOV for oxygenation failure, ventilation failure and duration of mechanical ventilation were 0.557 (95% CI 0.351 to 0.884), 0.892 (95% CI 0.435 to 1.829) and 0.079 (95% CI −0.045 to 0.203), respectively. The risk of barotrauma and hypotension were similar between the CMV group and HFOV group, with a RR of 1.205 (95% CI 0.834 to 1.742) and a RR of 1.326 (95% CI 0.271 to 6.476), respectively.ConclusionsAlthough HFOV seems not to increase the risk of barotrauma or hypotension, and reduces the risk of oxygenation failure, it does not improve survival in adult acute respiratory distress syndrome patients.

Extracorporeal Membrane Oxygenation for Adult Respiratory Distress Syndrome after Near-drowning

Background: Near-drowning victims surviving the initial period of asphyxia may develop life-threatening adult respiratory distress syndrome (ARDS). We highlight current understanding of extracorporeal membrane oxygenation (ECMO) for successful clinical management of severe ARDS in adult near-drowning victims with reference to a recent case of accidental submersion. Patient: Previously healthy 18-year-old female near-drowning victim with progressive hypoxaemia, hypercapnaemia, acidaemia and multiple organ failure. Results: Rapid restitution of respiratory function during a three-day period of treatment with venovenous ECMO. Conclusion: Extracorporeal membrane oxygenation is a feasible option in near-drowning adult victims with progressive ARDS not responding appropriately to conventional protective ventilation.