Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials

Personalized ventilation adjustment in ARDS: A systematic review and meta-analysis of image, driving pressure, transpulmonary pressure, and mechanical power

BACKGROUND

Acute Respiratory Distress Syndrome (ARDS) necessitates personalized treatment strategies due to its heterogeneity, aiming to mitigate Ventilator-Induced Lung Injury (VILI). Advanced monitoring techniques, including imaging, driving pressure, transpulmonary pressure, and mechanical power, present potential avenues for tailored interventions.

OBJECTIVE

To review some of the most important techniques for achieving greater personalization of mechanical ventilation in ARDS patients as evaluated in randomized clinical trials, by analyzing their effect on three clinically relevant aspects: mortality, ventilator-free days, and gas exchange.

METHODS

Following PRISMA guidelines, we conducted a systematic review and meta-analysis of Randomized Clinical Trials (RCTs) involving adult ARDS patients undergoing personalized ventilation adjustments. Outcomes were mortality (primary end-point), ventilator-free days, and oxygenation improvement.

RESULTS

Among 493 identified studies, 13 RCTs (n = 1255) met inclusion criteria. No personalized ventilation strategy demonstrated superior outcomes compared to traditional protocols. Meta-analysis revealed no significant reduction in mortality with image-guided (RR 0.88, 95 % CI 0.70-1.11), driving pressure-guided (RR 0.61, 95 % CI 0.29-1.30), or transpulmonary pressure-guided (RR 0.85, 95 % CI 0.58-1.24) strategies. Ventilator-free days and oxygenation outcomes showed no significant differences.

CONCLUSION

Our study does not support the superiority of personalized ventilation techniques over traditional protocols in ARDS patients. Further research is needed to standardize ventilation strategies and determine their impact on mechanical ventilation outcomes.

Tracheal intubation in critically ill adults with a physiologically difficult airway. An international Delphi study

PURPOSE

Our study aimed to provide consensus and expert clinical practice statements related to airway management in critically ill adults with a physiologically difficult airway (PDA).

METHODS

An international Steering Committee involving seven intensivists and one Delphi methodology expert was convened by the Society of Critical Care Anaesthesiologists (SOCCA) Physiologically Difficult Airway Task Force. The committee selected an international panel of 35 expert clinician-researchers with expertise in airway management in critically ill adults. A Delphi process based on an iterative approach was used to obtain the final consensus statements.

RESULTS

The Delphi process included seven survey rounds. A stable consensus was achieved for 53 (87%) out of 61 statements. The experts agreed that in addition to pathophysiological conditions, physiological alterations associated with pregnancy and obesity also constitute a physiologically difficult airway. They suggested having an intubation team consisting of at least three healthcare providers including two airway operators, implementing an appropriately designed checklist, and optimizing hemodynamics prior to tracheal intubation. Similarly, the experts agreed on the head elevated laryngoscopic position, routine use of videolaryngoscopy during the first attempt, preoxygenation with non-invasive ventilation, careful mask ventilation during the apneic phase, and attention to cardiorespiratory status for post-intubation care.

CONCLUSION

Using a Delphi method, agreement among a panel of international experts was reached for 53 statements providing guidance to clinicians worldwide on safe tracheal intubation practices in patients with a physiologically difficult airway to help improve patient outcomes. Well-designed studies are needed to assess the effects of these practice statements and address the remaining uncertainties.

Comparing the impact of targeting limited driving pressure to low tidal volume ventilation on mortality in mechanically ventilated adults with COVID-19 ARDS: an exploratory target trial emulation

BACKGROUND

An association between driving pressure (∆P) and the outcomes of invasive mechanical ventilation (IMV) may exist. However, the effect of a sustained limitation of ∆P on mortality in patients with acute respiratory distress syndrome (ARDS), including patients with COVID-19 (COVID-19-related acute respiratory distress syndrome (C-ARDS)) undergoing IMV, has not been rigorously evaluated. The use of emulations of a target trial in intensive care unit research remains in its infancy. To inform future, large ARDS target trials, we explored using a target trial emulation approach to analyse data from a cohort of IMV adults with C-ARDS to determine whether maintaining daily ∆p<15 cm H2O (in addition to traditional low tidal volume ventilation (LTVV) (tidal volume 5-7 cc/PBW+plateau pressure (Pplat) ≤30 cm H2O), compared with LTVV alone, affects the 28-day mortality.

METHODS

To emulate a target trial, adults with C-ARDS requiring >24 hours of IMV were considered to be assigned to limited ∆P or LTVV. Lung mechanics were measured twice daily after ventilator setting adjustments were made. To evaluate the effect of each lung-protective ventilation (LPV) strategy on the 28-day mortality, we fit a stabilised inverse probability weighted marginal structural model that adjusted for baseline and time-varying confounders known to affect protection strategy use/adherence or survival.

RESULTS

Among the 92 patients included, 27 (29.3%) followed limited ∆P ventilation, 23 (25.0%) the LTVV strategy and 42 (45.7%) received no LPV strategy. The adjusted estimated 28-day survival was 47.0% (95% CI 23%, 76%) in the limited ∆P group, 70.3% in the LTVV group (95% CI 37.6%, 100%) and 37.6% (95% CI 20.8%, 58.0%) in the no LPV strategy group.

INTERPRETATION

Limiting ∆P may not provide additional survival benefits for patients with C-ARDS over LTVV. Our results help inform the development of future target trial emulations focused on evaluating LPV strategies, including reduced ∆P, in adults with ARDS.

Respiratory effects of prone position in COVID-19 acute respiratory distress syndrome differ according to the recruitment-to-inflation ratio: a prospective observational study

BACKGROUND

Improvements in oxygenation and lung mechanics with prone position (PP) in patients with acute respiratory distress syndrome (ARDS) are inconstant. The objectives of the study were (i) to identify baseline variables, including the recruitment-to-inflation ratio (R/I), associated with a positive response to PP in terms of oxygenation (improvement of the ratio of arterial oxygen partial pressure over the inspired oxygen fraction (PaO2/FiO2) ≥ 20 mmHg) and lung mechanics; (ii) to evaluate whether the response to the previous PP session is associated with the response to the next session.

METHODS

In this prospective, observational, single-center study in patients who underwent PP for ARDS due to COVID-19, respiratory variables were assessed just before PP and at the end of the session. Respiratory variables included mechanical ventilation settings and respiratory mechanics variables, including R/I, an estimate of the potential for lung recruitment compared to lung overinflation.

RESULTS

In 50 patients, 201 PP sessions lasting 19 ± 3 h were evaluated. Neuromuscular blockades were used in 116 (58%) sessions. The PaO2/FiO2 ratio increased from 109 ± 31 mmHg to 165 ± 65 mmHg, with an increase ≥ 20 mmHg in 142 (71%) sessions. In a mixed effect logistic regression, only pre-PP PaO2/FiO2 (OR 1.12 (95% CI [1.01-1.24])/every decrease of 10 mmHg, p = 0.034) in a first model and improvement in oxygenation at the previous PP session (OR 3.69 (95% CI [1.27-10.72]), p = 0.017) in a second model were associated with an improvement in oxygenation with PP. The R/I ratio (n = 156 sessions) was 0.53 (0.30-0.76), separating lower- and higher-recruiters. Whereas PaO2/FiO2 improved to the same level in both subgroups, driving pressure and respiratory system compliance improved only in higher-recruiters (from 14 ± 4 to 12 ± 4 cmH2O, p = 0.027, and from 34 ± 11 to 38 ± 13 mL/cmH2O, respectively, p = 0.014).

CONCLUSIONS

A lower PaO2/FiO2 at baseline and a positive O2-response at the previous PP session are associated with a PP-induced improvement in oxygenation. In higher-recruiters, lung mechanics improved along with oxygenation. Benefits of PP could thus be greater in these patients.

Understanding ventilator-induced lung injury: The role of mechanical power

Mechanical ventilation stands as a life-saving intervention in the management of respiratory failure. However, it carries the risk of ventilator-induced lung injury. Despite the adoption of lung-protective ventilation strategies, including lower tidal volumes and pressure limitations, mortality rates remain high, leaving room for innovative approaches. The concept of mechanical power has emerged as a comprehensive metric encompassing key ventilator parameters associated with the genesis of ventilator-induced lung injury, including volume, pressure, flow, resistance, and respiratory rate. While numerous animal and human studies have linked mechanical power and ventilator-induced lung injury, its practical implementation at the bedside is hindered by calculation challenges, lack of equation consensus, and the absence of an optimal threshold. To overcome the constraints of measuring static respiratory parameters, dynamic mechanical power is proposed for all patients, regardless of their ventilation mode. However, establishing a causal relationship is crucial for its potential implementation, and requires further research. The objective of this review is to explore the role of mechanical power in ventilator-induced lung injury, its association with patient outcomes, and the challenges and potential benefits of implementing a ventilation strategy based on mechanical power.

Ventilatory pressure parameters impact the association between acute gastrointestinal injury and all-cause mortality in mechanically ventilated patients

Acute gastrointestinal injury (AGI) is common in mechanically ventilated (MV) patients, but the potential association between ventilatory pressure parameters and AGI grade and their impact on mortality remains unclear. This study aimed to explore the association between ventilatory pressure parameters and AGI grade, and their interaction on all-cause mortality in MV patients. This study was a secondary analysis of a multicenter, prospective, observational study that enrolled adult patients with an expected duration of mechanical ventilation ≥ 48 h from 14 general intensive care units in Zhejiang Province between March and August 2014. The AGI grade was assessed daily on the basis of gastrointestinal symptoms, intra-abdominal pressures, and feeding intolerance in the first week of admission to the ICU. This study included 331 patients (69.2% men; mean age, 64.6 ± 18.9 years). Multivariate regression analysis showed that plateau pressure (Pplat) (OR 1.044, 95% CI 1.009-1.081, P = 0.013), serum creatinine (OR 1.003, 95% CI 1.001-1.006, P = 0.042) and APACHE II score (OR 1.035, 95% CI 1.021-1.072, P = 0.045) were independently associated with global AGI grade III/IV within 7 days of ICU admission. Moreover, global AGI grade (HR 2.228, 95% CI 1.561-3.182, P < 0.001), serum creatinine (HR 1.002, 95% CI 1.001-1.003, P = 0.012) and APACHE II score (HR 1.039, 95% CI 1.015-1.063, P = 0.001) were independently associated with 60-day mortality. In addition, there were significant (Pint ≤ 0.028) interactions of Pplat and DP with AGI grade in relation to 60-days mortality, whereas no interaction (Pint = 0.061) between PEEP and AGI grade on 60-days mortality was observed. In the presence of Pplat ≥ 19 cmH2O, the patients with AGI grade III/IV had 60-day mortality rate of 72.2%, significantly higher than those with AGI grade I/II (48.7%, P = 0.018), whereas there were no significant differences (27.9% vs. 33.7%, P = 0.39) in 60-days mortality between AGI grade I/II and III/IV among the patients with Pplat < 19 cmH2O. In comparison with Pplat, DP had a similar interaction (Pint = 0.028) with AGI grade on 60-day mortality. Ventilatory pressure parameters (Pplat and DP) are independent risk factors of AGI grade III/IV. Pplat and DP interact with AGI grade on 60-days mortality, highlighting the importance of optimizing ventilatory pressure parameters to improve gastrointestinal function and survival outcomes of MV patients.Trial registration: ChiCTR-OCS-13003824.

TM9SF1 offers utility as an efficient predictor of clinical severity and mortality among acute respiratory distress syndrome patients

Introduction

Acute respiratory distress syndrome (ARDS) is a major cause of death among critically ill patients in intensive care settings, underscoring the need to identify biomarkers capable of predicting ARDS patient clinical status and prognosis at an early time point. This study specifically sought to explore the utility and clinical relevance of TM9SF1 as a biomarker for the early prediction of disease severity and prognostic outcomes in patients with ARDS.

Methods

This study enrolled 123 patients with severe ARDS and 116 patients with non-severe ARDS for whom follow-up information was available. The mRNA levels of TM9SF1 and cytokines in peripheral blood mononuclear cells from these patients were evaluated by qPCR. The predictive performance of TM9SF1 and other clinical indicators was evaluated using received operating characteristic (ROC) curves. A predictive nomogram was developed based on TM9SF1 expression and evaluated for its ability in the early prediction of severe disease and mortality in patients with ARDS.

Results

TM9SF1 mRNA expression was found to be significantly increased in patients with severe ARDS relative to those with non-severe disease or healthy controls. ARDS severity increased in correspondence with the level of TM9SF1 expression (odds ratio [OR] = 2.43, 95% confidence interval [CI] = 2.15-3.72, P = 0.005), and high TM9SF1 levels were associated with a greater risk of mortality (hazard ratio [HR] = 2.27, 95% CI = 2.20-4.39, P = 0.001). ROC curves demonstrated that relative to other clinical indicators, TM9SF1 offered superior performance in the prediction of ARDS severity and mortality. A novel nomogram incorporating TM9SF1 expression together with age, D-dimer levels, and C-reactive protein (CRP) levels was developed and was used to predict ARDS severity (AUC = 0.887, 95% CI = 0.715-0.943). A separate model incorporating TM9SF1 expression, age, neutrophil-lymphocyte ratio (NLR), and D-dimer levels (C-index = 0.890, 95% CI = 0.627-0.957) was also developed for predicting mortality.

Conclusion

Increases in ARDS severity and patient mortality were observed with rising levels of TM9SF1 expression. TM9SF1 may thus offer utility as a novel biomarker for the early prediction of ARDS patient disease status and clinical outcomes.

Novel Oxygenation and Saturation Indices for Mortality Prediction in COVID-19 ARDS Patients: The Impact of Driving Pressure and Mechanical Power

Background: The oxygenation index (OI) and oxygen saturation index (OSI) are proven mortality predictors in pediatric and adult patients, traditionally using mean airway pressure (Pmean). We introduce novel indices, replacing Pmean with DP (ΔPinsp), MPdyn, and MPtot, assessing their potential for predicting COVID-19 acute respiratory distress syndrome (ARDS) mortality, comparing them to traditional indices. Methods: We studied 361 adult COVID-19 ARDS patients for 7 days, collecting ΔPinsp, MPdyn, and MPtot, OI-ΔPinsp, OI-MPdyn, OI-MPtot, OSI-ΔPinsp, OSI-MPdyn, and OSI-MPtot. We compared these in surviving and non-surviving patients over the first 7 intensive care unit (ICU) days using Mann-Whitney U test. Logistic regression receiver operating characteristic (ROC) analysis assessed AUC and CI values for ICU mortality on day three. We determined cut-off values using Youden's method and conducted multivariate Cox regression on parameter limits. Results: All indices showed significant differences between surviving and non-surviving patients on the third day of ICU care. The AUC values of OI-ΔPinsp were significantly higher than those of P/F and OI-Pmean (P values .0002 and <.0001, respectively). Similarly, AUC and CI values of OSI-ΔPinsp and OSI-MPdyn were significantly higher than those of SpO2/FiO2 and OSI-Pmean values (OSI-ΔPinsp: P < .0001, OSI-MPdyn: P values .047 and .028, respectively). OI-ΔPinsp, OSI-ΔPinsp, OI-MPdyn, OSI-MPdyn, OI-MPtot, and OSI-MPtot had AUC values of 0.72, 0.71, 0.69, 0.68, 0.66, and 0.64, respectively, with cut-off values associated with hazard ratios and P values of 7.06 (HR = 1.84, P = .002), 8.04 (HR = 2.00, P ≤ .0001), 7.12 (HR = 1.68, P = .001), 5.76 (HR = 1.70, P ≤ .0001), 10.43 (HR = 1.52, P = .006), and 10.68 (HR = 1.66, P = .001), respectively. Conclusions: Critical values of all indices were associated to higher ICU mortality rates and extended mechanical ventilation durations. The OI-ΔPinsp, OSI-ΔPinsp, and OSI-MPdyn indices displayed the strongest predictive capabilities for ICU mortality. These novel indices offer valuable insights for intensivists in the clinical management and decision-making process for ARDS patients.

Endothelial cell-derived extracellular vesicles modulate the therapeutic efficacy of mesenchymal stem cells through IDH2/TET pathway in ARDS

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a severe and fatal disease. Although mesenchymal stem cell (MSC)-based therapy has shown remarkable efficacy in treating ARDS in animal experiments, clinical outcomes have been unsatisfactory, which may be attributed to the influence of the lung microenvironment during MSC administration. Extracellular vesicles (EVs) derived from endothelial cells (EC-EVs) are important components of the lung microenvironment and play a crucial role in ARDS. However, the effect of EC-EVs on MSC therapy is still unclear. In this study, we established lipopolysaccharide (LPS) - induced acute lung injury model to evaluate the impact of EC-EVs on the reparative effects of bone marrow-derived MSC (BM-MSC) transplantation on lung injury and to unravel the underlying mechanisms.

METHODS

EVs were isolated from bronchoalveolar lavage fluid of mice with LPS - induced acute lung injury and patients with ARDS using ultracentrifugation. and the changes of EC-EVs were analysed using nanoflow cytometry analysis. In vitro assays were performed to establish the impact of EC-EVs on MSC functions, including cell viability and migration, while in vivo studies were performed to validate the therapeutic effect of EC-EVs on MSCs. RNA-Seq analysis, small interfering RNA (siRNA), and a recombinant lentivirus were used to investigate the underlying mechanisms.

RESULTS

Compared with that in non-ARDS patients, the quantity of EC-EVs in the lung microenvironment was significantly greater in patients with ARDS. EVs derived from lipopolysaccharide-stimulated endothelial cells (LPS-EVs) significantly decreased the viability and migration of BM-MSCs. Furthermore, engrafting BM-MSCs pretreated with LPS-EVs promoted the release of inflammatory cytokines and increased pulmonary microvascular permeability, aggravating lung injury. Mechanistically, LPS-EVs reduced the expression level of isocitrate dehydrogenase 2 (IDH2), which catalyses the formation of α-ketoglutarate (α-KG), an intermediate product of the tricarboxylic acid (TCA) cycle, in BM-MSCs. α-KG is a cofactor for ten-eleven translocation (TET) enzymes, which catalyse DNA hydroxymethylation in BM-MSCs.

CONCLUSIONS

This study revealed that EC-EVs in the lung microenvironment during ARDS can affect the therapeutic efficacy of BM-MSCs through the IDH2/TET pathway, providing potential strategies for improving the therapeutic efficacy of MSC-based therapy in the clinic.

Association between mechanical power during one-lung ventilation and pulmonary complications after thoracoscopic lung resection surgery: a prospective observational study

BACKGROUND

The role of mechanical power on pulmonary outcomes after thoracic surgery with one-lung ventilation was unclear. We investigated the association between mechanical power and postoperative pulmonary complications in patients undergoing thoracoscopic lung resection surgery.

METHODS

In this single-center, prospective observational study, 622 patients scheduled for thoracoscopic lung resection surgery were included. Volume control mode with lung protective ventilation strategies were implemented in all participants. The primary endpoint was a composite of postoperative pulmonary complications during hospital stay. Multivariable logistic regression models were used to evaluate the association between mechanical power and outcomes.

RESULTS

The incidence of pulmonary complications after surgery during hospital stay was 24.6% (150 of 609 patients). The multivariable analysis showed that there was no link between mechanical power and postoperative pulmonary complications.

CONCLUSIONS

In patients undergoing thoracoscopic lung resection with standardized lung-protective ventilation, no association was found between mechanical power and postoperative pulmonary complications.

TRIAL REGISTRATION

Trial registration number: ChiCTR2200058528, date of registration: April 10, 2022.

Diaphragmatic morphological post-mortem findings in critically ill COVID-19 patients: an observational study

Our study investigates the post-mortem findings of the diaphragm's muscular structural changes in mechanically ventilated COVID-19 patients. Diaphragm samples of the right side from 42 COVID-19 critically ill patients were analyzed and correlated with the type and length of mechanical ventilation (MV), ventilatory parameters, prone positioning, and use of sedative drugs. The mean number of fibers was 550±626. The cross-sectional area was 4120±3280 μm2, while the muscular fraction was 0.607±0.126. The overall population was clustered into two distinct populations (clusters 1 and 2). Cluster 1 showed a lower percentage of slow myosin fiber and higher fast fiber content than cluster 2, 68% versus 82%, p<0.00001, and 29.8% versus 18.8%, p=0.00045 respectively. The median duration of MV was 180 (41-346) hours. In cluster 1, a relationship between assisted ventilation and fast myosin fiber percentage (R2=-0.355, p=0.014) was found. In cluster 2, fast fiber content increased with increasing the length of the controlled MV (R2=0.446, p=0.006). A high grade of fibrosis was reported. Cluster 1 was characterized by fibers' atrophy and cluster 2 by hypertrophy, supposing different effects of ventilation on the diaphragm but without excluding a possible direct viral effect on diaphragmatic fibers.

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

Introduction

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.

Methods

Patients >18 years of age with body mass index >35 kg/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 15 mmHg 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 5 cmH2O 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, 5 min 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.

Results

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 ± 2 cmH2O; 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, -1.9 J/min; PEEPIND, +10.0 J/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, -1.9 J/min; PEEPIND, +10.0 J/min).

Conclusion

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.

Clinical Trial Registration

The protocol was registered at the Brazilian Registry of Clinical Trials (U1111-1220-7296).

Driving pressure in mechanical ventilation: A review

Driving pressure (∆P) is a core therapeutic component of mechanical ventilation (MV). Varying levels of ∆P have been employed during MV depending on the type of underlying pathology and severity of injury. However, ∆P levels have also been shown to closely impact hard endpoints such as mortality. Considering this, conducting an in-depth review of ∆P as a unique, outcome-impacting therapeutic modality is extremely important. There is a need to understand the subtleties involved in making sure ∆P levels are optimized to enhance outcomes and minimize harm. We performed this narrative review to further explore the various uses of ∆P, the different parameters that can affect its use, and how outcomes vary in different patient populations at different pressure levels. To better utilize ∆P in MV-requiring patients, additional large-scale clinical studies are needed.

Comprehensive study of mechanical power in controlled mechanical ventilation: Prevalence of elevated mechanical power and component analysis

OBJECTIVE

To determine the prevalence of elevated mechanical power (MP) values (>17J/min) used in routine clinical practice.

DESIGN

Observational, descriptive, cross-sectional, analytical, multicenter, international study conducted on November 21, 2019, from 8:00 AM to 3:00 PM. NCT03936231.

SETTING

One hundred thirty-three Critical Care Units.

PATIENTS

Patients receiving invasive mechanical ventilation for any cause.

INTERVENTIONS

None.

MAIN VARIABLES OF INTEREST

Mechanical power.

RESULTS

A population of 372 patients was analyzed. PM was significantly higher in patients under pressure-controlled ventilation (PC) compared to volume-controlled ventilation (VC) (19.20±8.44J/min vs. 16.01±6.88J/min; p<0.001), but the percentage of patients with PM>17J/min was not different (41% vs. 35%, respectively; p=0.382). The best models according to AICcw expressing PM for patients in VC are described as follows: Surrogate Strain (Driving Pressure) + PEEP+Surrogate Strain Rate (PEEP/Flow Ratio) + Respiratory Rate. For patients in PC, it is defined as: Surrogate Strain (Expiratory Tidal Volume/PEEP) + PEEP+Surrogate Strain Rate (Surrogate Strain/Ti) + Respiratory Rate+Expiratory Tidal Volume+Ti.

CONCLUSIONS

A substantial proportion of mechanically ventilated patients may be at risk of experiencing elevated levels of mechanical power. Despite observed differences in mechanical power values between VC and PC ventilation, they did not result in a significant disparity in the prevalence of high mechanical power values.

Intraoperative Mechanical Power and Postoperative Pulmonary Complications in Noncardiothoracic Elective Surgery Patients: A 10-Year Retrospective Cohort Study

BACKGROUND

Postoperative pulmonary complications is a major issue that affects outcomes of surgical patients. The hypothesis was that the intraoperative ventilation parameters are associated with occurrence of postoperative pulmonary complications.

METHODS

A single-center retrospective cohort study was conducted at the Lille University Hospital, France. The study included 33,701 adults undergoing noncardiac, nonthoracic elective surgery requiring general anesthesia with tracheal intubation between January 2010 and December 2019. Intraoperative ventilation parameters were compared between patients with and without one or more postoperative pulmonary complications (respiratory infection, respiratory failure, pleural effusion, atelectasis, pneumothorax, bronchospasm, and aspiration pneumonitis) within 7 days of surgery.

RESULTS

Among 33,701 patients, 2,033 (6.0%) had one or more postoperative pulmonary complications. The lower tidal volume to predicted body weight ratio (odds ratio per -1 ml·kgPBW-1, 1.08; 95% CI, 1.02 to 1.14; P < 0.001), higher mechanical power (odds ratio per 4 J·min-1, 1.37; 95% CI, 1.26 to 1.49; P < 0.001), dynamic respiratory system compliance less than 30 ml·cm H2O (1.30; 95% CI, 1.15 to 1.46; P < 0.001), oxygen saturation measured by pulse oximetry less than 96% (odds ratio, 2.42; 95% CI, 1.97 to 2.96; P < 0.001), and lower end-tidal carbon dioxide (odds ratio per -3 mmHg, 1.06; 95% CI, 1.00 to 1.13; P = 0.023) were independently associated with postoperative pulmonary complications. Patients with postoperative pulmonary complications were more likely to be admitted to the intensive care unit (odds ratio, 12.5; 95% CI, 6.6 to 10.1; P < 0.001), had longer hospital length of stay (subhazard ratio, 0.43; 95% CI, 0.40 to 0.45), and higher in-hospital (subhazard ratio, 6.0; 95% CI, 4.1 to 9.0; P < 0.001) and 1-yr mortality (subhazard ratio, 2.65; 95% CI, 2.33 to 3.02; P < 0.001).

CONCLUSIONS

In the study's population, decreased rather than increased tidal volume, decreased compliance, increased mechanical power, and decreased end-tidal carbon dioxide were independently associated with postoperative pulmonary complications.

EDITOR’S PERSPECTIVE

Effects on mechanical power of different devices used for inhaled sedation in a bench model of protective ventilation in ICU

BACKGROUND

Inhaled sedation during invasive mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) has received increasing attention. However, inhaled sedation devices increase dead-space ventilation and an undesirable effect is the increase in minute ventilation needed to maintain CO2 removal. A consequence of raising minute ventilation is an increase in mechanical power (MP) that can promote lung injury. However, the effect of inhaled sedation devices on MP remains unknown.

METHODS

We conducted a bench study to assess and compare the effects of three devices delivering inhaled sevoflurane currently available in ICU (AnaConDa-50 mL (ANA-50), AnaConDa-100 mL (ANA-100), and MIRUS) on MP by using a test lung model set with three compliances (20, 40, and 60 mL/cmH2O). We simulated lung-protective ventilation using a low tidal volume and two levels of positive end-expiratory pressure (5 and 15 cmH2O) under ambient temperature and dry conditions. Following the insertion of the devices, either the respiratory rate or tidal volume was increased in 15%-steps until end-tidal CO2 (EtCO2) returned to the baseline value. MP was calculated at baseline and after EtCO2 correction using a simplified equation.

RESULTS

Following device insertion, the EtCO2 increase was significantly greater with MIRUS (+ 78 ± 13%) and ANA-100 (+ 100 ± 11%) than with ANA-50 (+ 49 ± 7%). After normalizing EtCO2 by adjusting minute ventilation, MP significantly increased by more than 50% with all inhaled sedation devices compared to controls. The lowest increase in MP was observed with ANA-50 (p < 0.05 versus ANA-100 and MIRUS). The Costa index, another parameter assessing the mechanical energy delivered to the lungs, calculated as driving pressure × 4 + respiratory rate, significantly increased by more than 20% in all experimental conditions. Additional experiments performed under body temperature, ambient pressure, and gas saturated with water vapor conditions, confirmed the main results with an increase in MP > 50% with all devices after normalizing EtCO2 by adjusting minute ventilation.

CONCLUSION

Inhaled sedation devices substantially increased MP in this bench model of protective ventilation, which might limit their benefits in ARDS.

Risk Factors for Death of Burn Patients With Acute Respiratory Distress Syndrome

The aim of this study was to investigate factors independently affecting outcomes of post-burn ARDS patients at the time of ARDS onset. A prospective study was conducted on 66 patients with ARDS, treated in the ICU at the Le Huu Trac National Burns Hospital in Hanoi, Viet Nam, from 2014 to 2017. Patients were divided into a survivor and non-survivor group. Demographic criteria, burn severity, inhalation injury, clinical and subclinical features at ARDS onset were compared between the two groups. The results showed that overall mortality of ARDS patients was 62.12%. Logistic regression analysis indicated that at the time of ARDS onset, serum lactate level (OR=6.71), blood platelet count (OR=.99), static lung compliance (OR=.73) and driving pressure (OR=1.69) were independent risk factors for death, while patients' demographics, burn severity and ARDS severity did not significantly affect the mortality rate.

The Use of the Oxygenation Stretch Index to Predict Outcomes in Mechanically Ventilated Patients With COVID-19 ARDS

BACKGROUND

In ARDS caused by COVID-19 pneumonia, appropriate adjustment of physiologic parameters based on lung stretch or oxygenation may optimize the ventilatory strategy. This study aims to describe the prognostic performance on 60-d mortality of single and composite respiratory variables in subjects with COVID-19 ARDS who are on mechanical ventilation with a lung-protective strategy, including the oxygenation stretch index combining oxygenation and driving pressure (ΔP).

METHODS

This single-center observational cohort study enrolled 166 subjects on mechanical ventilation and diagnosed with COVID-19 ARDS. We evaluated their clinical and physiologic characteristics. The primary study outcome was 60-d mortality. Prognostic factors were evaluated through receiver operating characteristic analysis, Cox proportional hazards regression model, and Kaplan-Meier survival curves.

RESULTS

Mortality at day 60 was 18.1%, and hospital mortality was 22.9%. Oxygenation, ΔP, and composite variables were tested: oxygenation stretch index ([Formula: see text]/[Formula: see text] divided by ΔP) and ΔP × 4 + breathing frequency (f) (ΔP × 4 + f). At both day 1 and day 2 after inclusion, the oxygenation stretch index had the best area under the receiver operating characteristic curve (oxygenation stretch index on day 1 0.76 (95% CI 0.67-0.84) and on day 2 0.83 (95% CI 0.76-0.91) to predict 60-d mortality, although without significant difference from other indexes. In multivariable Cox regression, ΔP, [Formula: see text]/[Formula: see text], ΔP × 4 + f, and oxygenation stretch index were all associated with 60-d mortality. When dichotomizing the variables, ΔP ≥ 14, [Formula: see text]/[Formula: see text] ≤ 152 mm Hg, ΔP × 4 + f ≥ 80, and oxygenation stretch index < 7.7 showed lower 60-d survival probability. At day 2, after optimization of ventilatory settings, the subjects who persisted with the worse cutoff values for the oxygenation stretch index showed a lower probability of survival at 60 d compared with day 1; this was not the case for other parameters.

CONCLUSIONS

The oxygenation stretch index, which combines [Formula: see text]/[Formula: see text] and ΔP, is associated with mortality and may be useful to predict clinical outcomes in COVID-19 ARDS.

Mechanical Power of Ventilation: From Computer to Clinical Implications

Mechanical ventilation is a lifesaving intervention that may also induce further lung injury by exerting excessive mechanical forces on susceptible lung tissue, a phenomenon termed ventilator-induced lung injury (VILI). The concept of mechanical power (MP) aims to unify in one single variable the contribution of the different ventilatory parameters that could induce VILI by measuring the energy transfer to the lung over time. Despite an increasing amount of evidence demonstrating that high MP values can be associated with VILI development in experimental studies, the evidence regarding the association of MP and clinical outcomes remains controversial. In the present review, we describe the different determinants of VILI, the concept and computation of MP, and discuss the experimental and clinical studies related to MP. Currently, due to different limitations, the clinical application of MP is debatable. Further clinical studies are required to enhance our understanding of the relationship between MP and the development of VILI, as well as its potential impact on clinical outcomes.

Physiologic Markers of Disease Severity in ARDS

Despite its significant limitations, the PaO2 /FIO2 remains the standard tool to classify disease severity in ARDS. Treatment decisions and research enrollment have depended on this parameter for over 50 years. In addition, several variables have been studied over the past few decades, incorporating other physiologic considerations such as ventilation efficiency, lung mechanics, and right-ventricular performance. This review describes the strengths and limitations of all relevant parameters, with the goal of helping us better understand disease severity and possible future treatment targets.

The impact of the new acute respiratory distress syndrome (ARDS) criteria on Berlin criteria ARDS patients: a multicenter cohort study

OBJECTIVE

The European Society of Intensive Care Medicine (ESICM) recently recommended changes to the criteria of acute respiratory distress syndrome (ARDS), patients with high-flow oxygen were included, however, the effect of these changes remains unclear. Our objectives were to evaluate the performance of these new criteria and to compare the outcomes of patients meeting the new ARDS criteria with those meeting the Berlin ARDS criteria.

METHODS

This was a retrospective cohort. The patients admitted to the intensive care unit (ICU) were diagnosed with ARDS. Patients were classified as meeting Berlin criteria ARDS (n = 4279), high-flow nasal oxygen (HFNO) criteria ARDS (n = 559), or new criteria ARDS (n = 4838).

RESULTS

In comparison with HFNO criteria ARDS and new criteria ARDS, patients with Berlin criteria ARDS demonstrated lower blood oxygen levels assessed by PaO2/FiO2, SpO2/FiO2, and ROX (SpO2/FiO2/respiratory rate) (p < 0.001); and higher severity of illness assessed by the Sequential Organ Failure Assessment (SOFA) score, Acute Physiology And Chronic Health Evaluations (APACHE II), Simplified Acute Physiology Score (SAPS II) (p < 0.001), (p < 0.001), and longer ICU and hospital stays (p < 0.001). In comparison with the HFNO criteria, patients meeting Berlin criteria ARDS had higher hospital mortality (10.6% vs. 16.9%; p = 0.0082), 28-day mortality (10.6% vs. 16.5%; p = 0.0079), and 90-day mortality (10.7% vs. 17.1%; p = 0.0083). ARDS patients with HFNO did not have severe ARDS; Berlin criteria ARDS patients with severe ARDS had the highest mortality rate (approximately 33%). PaO2/FiO2, SpO2/FiO2, and ROX negatively correlated with the SOFA and APACHE II scores. The SOFA and APACHE II scores had high specificity and sensitivity for prognosis in patients with new criteria ARDS.

CONCLUSION

The new criteria of ARDS reduced the severity of illness, length of stay in the ICU, length of hospital stays, and overall mortality. SOFA and APACHE II scores remain important in assessing the prognosis of patients with new criteria ARDS.

TRIAL REGISTRATION

Registration number: ChiCTR2200067084.

Association between ventilatory ratio and mortality in patients with acute respiratory distress syndrome and COVID 19: A multicenter, retrospective cohort study

BACKGROUND

Mortality rates in patients with COVID-19 undergoing mechanical ventilation in the intensive care unit are high. The causes of this mortality have been rigorously investigated. The aim of the present study is to establish mortality risk factors related to lung mechanics measured at days 1 and 5 in patients with covid-19 ARDS managed with invasive mechanical ventilation in the intensive care unit.

METHODS

A retrospective observational multicenter study including consecutive patients with a confirmed diagnosis of COVID-19-induced ARDS, admitted to three institutions and seven intensive care units in the city of Bogota between May 20, 2020 and May 30, 2022 who required mechanical ventilation for at least five days. Data were collected from the medical records of patients who met the inclusion criteria on day 1 and day 5 of mechanical ventilation. The primary outcome assessed was mortality at day 30.

RESULTS

A total of 533 consecutive patients admitted with ARDS with COVID-19 were included. Ventilatory ratio, plateau pressure and driving pressure measured on day 5 were significantly higher in non-survivors (p < 0.05). Overall, 30-day follow-up mortality was 48.8%. The increases between day 1 and day 5 in the ventilatory ratio (OR 1.42, 95%CI 1.03-2.01, p = 0.04), driving pressure (OR 1.56, 95%CI 1.10-2.22, p = 0.01); and finally plateau pressure (OR 1.9, 95%CI 1.34-2.69, p = 0.001) were associated with an increased risk of death. There was no association between deterioration of PaO2/FIO2 index and mortality (OR 1.34, 95%CI 0.96-1.56, p = 0.053).

CONCLUSIONS

Ventilatory ratio, plateau pressure, driving pressure, and age were identified as independent risk factors for 30-day mortality in patients with ARDS due to COVID-19 on day 5 of invasive mechanical ventilation.

Quality Review of Prone Patient Transport Protocol

OBJECTIVE

This is a retrospective quality review of LifeFlight Nova Scotia's prone patient transport protocol.

METHODS

Electronic patient care records were queried for acute respiratory distress syndrome, prone position, proning, supine to prone, and prone to prone between February 2017 and June 2022. Eligible electronic patient care records were reviewed for demographics (sex, age, and weight); method of transports (ambulance, rotor wing, or fixed wing); duration of transports; mechanical ventilation parameters; medication infusions; arterial blood gases; occurrences of mild hypoxemia (any oxygen saturation [SpO2] < 88% or decrease in SpO2 > 5%); hypotension (any episode of MAP < 65 mm Hg); severe hypoxemia (any SpO2 < 80% or decrease in SpO2 > 10%); refractory hypotension (mean arterial pressure < 65 mm Hg not responsive to vasopressor/inotropes); cardiac arrests; and displacement of central lines, arterial lines, and endotracheal tubes.

RESULTS

Seventeen prone patients were transported by ambulance, rotor wing, and fixed wing with 4 occurrences of mild hypotension, 4 occurrences of mild hypoxemia, and 1 occurrence of refractory hypotension.

CONCLUSION

Interfacility transfer of prone patients by a dedicated critical care team is feasible with minimal adverse occurrences while ensuring patients have access to the specialized lifesaving care they require.

The Impact of Mechanical Energy Assessment on Mechanical Ventilation: A Comprehensive Review and Practical Application

Mechanical ventilation (MV) provides basic organ support for patients who have acute hypoxemic respiratory failure, with acute respiratory distress syndrome as the most severe form. The use of excessive ventilation forces can exacerbate the lung condition and lead to ventilator-induced lung injury (VILI); mechanical energy (ME) or power can characterize such forces applied during MV. The ME metric combines all MV parameters affecting the respiratory system (ie, lungs, chest, and airways) into a single value. Besides evaluating the overall ME, this parameter can be also related to patient-specific characteristics, such as lung compliance or patient weight, which can further improve the value of ME for characterizing the aggressiveness of lung ventilation. High ME is associated with poor outcomes and could be used as a prognostic parameter and indicator of the risk of VILI. ME is rarely determined in everyday practice because the calculations are complicated and based on multiple equations. Although low ME does not conclusively prevent the possibility of VILI (eg, due to the lung inhomogeneity and preexisting damage), individualization of MV settings considering ME appears to improve outcomes. This article aims to review the roles of bedside assessment of mechanical power, its relevance in mechanical ventilation, and its associations with treatment outcomes. In addition, we discuss methods for ME determination, aiming to propose the most suitable method for bedside application of the ME concept in everyday practice.

A closed-loop ventilation mode that targets the lowest work and force of breathing reduces the transpulmonary driving pressure in patients with moderate-to-severe ARDS

INTRODUCTION

The driving pressure (ΔP) has an independent association with outcome in patients with acute respiratory distress syndrome (ARDS). INTELLiVENT-Adaptive Support Ventilation (ASV) is a closed-loop mode of ventilation that targets the lowest work and force of breathing.

AIM

To compare transpulmonary and respiratory system ΔP between closed-loop ventilation and conventional pressure controlled ventilation in patients with moderate-to-severe ARDS.

METHODS

Single-center randomized cross-over clinical trial in patients in the early phase of ARDS. Patients were randomly assigned to start with a 4-h period of closed-loop ventilation or conventional ventilation, after which the alternate ventilation mode was selected. The primary outcome was the transpulmonary ΔP; secondary outcomes included respiratory system ΔP, and other key parameters of ventilation.

RESULTS

Thirteen patients were included, and all had fully analyzable data sets. Compared to conventional ventilation, with closed-loop ventilation the median transpulmonary ΔP with was lower (7.0 [5.0-10.0] vs. 10.0 [8.0-11.0] cmH₂O, mean difference - 2.5 [95% CI - 2.6 to - 2.1] cmH₂O; P = 0.0001). Inspiratory transpulmonary pressure and the respiratory rate were also lower. Tidal volume, however, was higher with closed-loop ventilation, but stayed below generally accepted safety cutoffs in the majority of patients.

CONCLUSIONS

In this small physiological study, when compared to conventional pressure controlled ventilation INTELLiVENT-ASV reduced the transpulmonary ΔP in patients in the early phase of moderate-to-severe ARDS. This closed-loop ventilation mode also led to a lower inspiratory transpulmonary pressure and a lower respiratory rate, thereby reducing the intensity of ventilation. Trial registration Clinicaltrials.gov, NCT03211494, July 7, 2017. https://clinicaltrials.gov/ct2/show/NCT03211494?term=airdrop&draw=2&rank=1 .

Development and Internal Validation of a Novel Prognostic Score to Predict Mortality in Acute Respiratory Distress Syndrome - Driving Pressure, Oxygenation and Nutritional Evaluation - "DRONE Score"

Introduction

There are few scores for mortality prediction in acute respiratory distress syndrome (ARDS) incorporating comprehensive ventilatory, acute physiological, organ dysfunction, oxygenation, and nutritional parameters. This study aims to determine the risk factors of ARDS mortality from the above-mentioned parameters at 48 h of invasive mechanical ventilation (IMV), which are feasible across most intensive care unit settings.

Methods

Prospective, observational, single-center study with 150 patients with ARDS defined by Berlin definition, receiving IMV with lung protective strategy.

Results

Our study had a mortality of 41.3% (62/150). We developed a 9-point novel prediction score, the driving pressure oxygenation and nutritional evaluation (DRONE) score comprising of driving pressure (DP), oxygenation accessed by the ratio of partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2) ratio and nutritional evaluation using the modified nutrition risk in the critically ill (mNUTRIC) score. Each component of the DRONE score with the cutoff value to predict mortality was assigned a particular score (the lowest DP within 48 h in a patient being always ≥15 cmH2O a score of 2, the highest achievable PaO2/FiO2 <208 was assigned a score of 4 and the mNUTRIC score ≥4 was assigned a score of (3). We obtained the DRONE score ≥4, area under the curve 0.860 to predict mortality. Cox regression for the DRONE score >4 was highly associated with mortality (P < 0.001, hazard ratio 5.43, 95% confidence interval [2.94-10.047]). Internal validation was done by bootstrap analysis. The clinical utility of the DRONE score ≥4 was assessed by Kaplan-Meier curve which showed significance.

Conclusions

The DRONE score ≥4 could be a reliable predictor of mortality at 48 h in ARDS patients receiving IMV.

Mechanical power normalized to aerated lung predicts noninvasive ventilation failure and death and contributes to the benefits of proning in COVID-19 hypoxemic respiratory failure

Background

Concern exists that noninvasive ventilation (NIV) may promote ventilation-induced lung injury(VILI) and worsen outcome in acute hypoxemic respiratory failure (AHRF). Different individual ventilatory variables have been proposed to predict clinical outcomes, with inconsistent results.Mechanical power (MP), a measure of the energy transfer rate from the ventilator to the respiratory system during mechanical ventilation, might provide solutions for this issue in the framework of predictive, preventive and personalized medicine (PPPM). We explored (1) the impact of ventilator-delivered MP normalized to well-aerated lung (MP_WAL) on physio-anatomical and clinical responses to NIV in COVID-19-related AHRF and (2) the effect of prone position(PP) on MP_WAL.

Methods

We analyzed 216 noninvasively ventilated COVID-19 patients (108 patients receiving PP + NIV and 108 propensity score-matched patients receiving supine NIV) with moderate-to-severe(paO2/FiO2 ratio < 200) AHRF enrolled in the PRO-NIV controlled non-randomized study (ISRCTN23016116).Quantification of differentially aerated lung volumes by lung ultrasonography (LUS) was validated against CT scans. Respiratory parameters were hourly recorded, ABG were performed 1 h after each postural change. Time-weighed average values of ventilatory variables, including MP_WAL, and gas exchange parameters (paO2/FiO2 ratio, dead space indices) were calculated for each ventilatory session. LUS and circulating biomarkers were assessed daily.

Results

Compared with supine position, PP was associated with a 34% MP_WAL reduction, attributable largely to an absolute MP reduction and secondly to an enhanced lung reaeration.Patients receiving a high MP_WAL during the 1^st 24 h of NIV [MP_WAL(day 1)] had higher 28-d NIV failure (HR = 4.33,95%CI:3.09 - 5.98) and death (HR = 5.17,95%CI: 3.01 - 7.35) risks than those receiving a low MP_WAL(day 1).In Cox multivariate analyses, MP_WAL(day 1) remained independently associated with 28-d NIV failure (HR = 1.68,95%CI:1.15-2.41) and death (HR = 1.69,95%CI:1.22-2.32).MP_WAL(day 1) outperformed other power measures and ventilatory variables as predictor of 28-d NIV failure (AUROC = 0.89;95%CI:0.85-0.93) and death (AUROC = 0.89;95%CI:0.85-0.94).MP_WAL(day 1) predicted also gas exchange, ultrasonographic and inflammatory biomarker responses, as markers of VILI, on linear multivariate analysis.

Conclusions

In the framework of PPPM, early bedside MP_WAL calculation may provide added value to predict response to NIV and guide subsequent therapeutic choices i.e. prone position adoption during NIV or upgrading to invasive ventilation, to reduce hazardous MP_WAL delivery, prevent VILI progression and improve clinical outcomes in COVID-19-related AHRF.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00325-5.

Effects of obesity, pneumoperitoneum, and body position on mechanical power of intraoperative ventilation: an observational study

Mechanical power can describe the complex interaction between the respiratory system and the ventilator and may predict lung injury or pulmonary complications, but the power associated with injury of healthy human lungs is unknown. Body habitus and surgical conditions may alter mechanical power but the effects have not been measured. In a secondary analysis of an observational study of obesity and lung mechanics during robotic laparoscopic surgery, we comprehensively quantified the static elastic, dynamic elastic, and resistive energies comprising mechanical power of ventilation. We stratified by body mass index (BMI) and examined power at four surgical stages: level after intubation, with pneumoperitoneum, in Trendelenburg, and level after releasing the pneumoperitoneum. Esophageal manometry was used to estimate transpulmonary pressures. Mechanical power of ventilation and its bioenergetic components increased over BMI categories. Respiratory system and lung power were nearly doubled in subjects with class 3 obesity compared with lean at all stages. Power dissipated into the respiratory system was increased with class 2 or 3 obesity compared with lean. Increased power of ventilation was associated with decreasing transpulmonary pressures. Body habitus is a prime determinant of increased intraoperative mechanical power. Obesity and surgical conditions increase the energies dissipated into the respiratory system during ventilation. The observed elevations in power may be related to tidal recruitment or atelectasis, and point to specific energetic features of mechanical ventilation of patients with obesity that may be controlled with individualized ventilator settings.NEW & NOTEWORTHY Mechanical power describes the complex interaction between a patient's lungs and the ventilator and may be useful in predicting lung injury. However, its behavior in obesity and during dynamic surgical conditions is not understood. We comprehensively quantified ventilation bioenergetics and effects of body habitus and common surgical conditions. These data show body habitus is a prime determinant of intraoperative mechanical power and provide quantitative context for future translation toward a useful perioperative prognostic measurement.

Effect of different titration methods on right heart function and prognosis in patients with acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a common disease in intensive critical care(ICU), and the use of positive end-expiratory pressure(PEEP) during mechanical ventilation can increase the right heart afterload and eventually cause right heart dysfunction. For these factors causing acute cor pulmonale(ACP), especially inappropriate mechanical ventilation settings, it is important to explore the effect of PEEP on right heart function.

OBJECTIVE

To investigate the effects of three titration methods on right heart function and prognosis in patients with ARDS.

METHODS

Observational, prospective study in which ARDS patients were enrolled into three distinct PEEP-titration strategies groups: guide, transpulmonary pressure-oriented and driving pressure-oriented. Prognostic indicators, right heart systolic and diastolic echocardiographic function indices, ventilatory parameters, blood gas analysis results, and respiratory mechanics Monitoring indices were collated and analyzed statistically by STATA 15 software.

RESULTS

A total of 62 ARDS patients were enrolled into guide (G) group (n=40) for whom titrated PEEP values were 9±2cm H₂O, driving pressure-oriented (DPO) group (n=12) with titrated PEEP values of 10±2cm H₂O and transpulmonary pressure-oriented (TPO) group (n=10) with titrated PEEP values of 12±3cm H₂O. Values were significantly higher for TPO than for G (p=0.616) or DPO (p=0.011). Compliance was significantly increased after 72 h in the TPO and DPO groups compared with the G group (p<0.001). Mean airway pressure at end-inspiratory obstruction (p=0.047), tricuspid annular plane systolic excursion (TAPSE, p<0.001) and right ventricular area change fraction (RVFAC, p=0.049) were all higher in the TPO and DPO groups than in the G group. E/A indices were significantly better in the TPO group than in the G or DPO groups (p=0.046). No significant differences in 28 day mortality were found among the three groups. Multivariate logistic regression analysis revealed that lung compliance and transpulmonary pressure-oriented PEEP titration method was negatively correlated to the increase in right ventricular systolic dysfunction.

CONCLUSION

Transpulmonary pressure-oriented PEEP titration improves oxygenation and pulmonary function and causes less right heart strain when compared to other PEEP-titration methods during mechanical ventilation of ARDS patients.

Role of Changes in Driving Pressure and Mechanical Power in Predicting Mortality in Patients with Acute Respiratory Distress Syndrome

Driving pressure (ΔP) and mechanical power (MP) are associated with increased mortality in patients with acute respiratory distress syndrome (ARDS). We aimed to investigate which was better to predict mortality between changes in ΔP and MP. We reanalyzed data from a prospective observational cohort study of patients with ARDS in our hospital. Serial ΔP and MP values were calculated. The factors associated with survival were analyzed. Binary logistic regression showed that age (odds ratio (OR), 1.012; 95% confidence interval (CI), 1.003-1.022), Sequential Organ Failure assessment (SOFA) score (OR, 1.144; 95% CI, 1.086-1.206), trauma (OR, 0.172; 95% CI, 0.035-0.838), ΔP (OR, 1.077; 95% CI, 1.044-1.111), change in ΔP (OR, 1.087; 95% CI, 1.054-1.120), and change in MP (OR, 1.018; 95% CI, 1.006-1.029) were independently associated with 30-day mortality. Change in MP, change in ΔP, and SOFA scores were superior to ΔP in terms of the accuracy of predicting 30-day mortality. In conclusion, calculating change in ΔP is easy for respiratory therapists in clinical practice and may be used to predict mortality in patients with ARDS.

Mechanical power of ventilation and driving pressure: two undervalued parameters for pre extracorporeal membrane oxygenation ventilation and during daily management?

The current ARDS guidelines highly recommend lung protective ventilation which include plateau pressure (P_plat < 30 cm H₂O), positive end expiratory pressure (PEEP > 5 cm H₂O) and tidal volume (V_t of 6 ml/kg) of predicted body weight. In contrast, the ELSO guidelines suggest the evaluation of an indication of veno-venous extracorporeal membrane oxygenation (ECMO) due to hypoxemic or hypercapnic respiratory failure or as bridge to lung transplantation. Finally, these recommendations remain a wide range of scope of interpretation. However, particularly patients with moderate-severe to severe ARDS might benefit from strict adherence to lung protective ventilation strategies. Subsequently, we discuss whether extended physiological ventilation parameter analysis might be relevant for indication of ECMO support and can be implemented during the daily routine evaluation of ARDS patients. Particularly, this viewpoint focus on driving pressure and mechanical power.

Intraoperative Ventilator Management of the Critically Ill Patient

Strategies for the intraoperative ventilator management of the critically ill patient focus on parameters used for lung protective ventilation with acute respiratory distress syndrome, preventing or limiting the deleterious effects of mechanical ventilation, and optimizing anesthetic and surgical conditions to limit postoperative pulmonary complications for patients at risk. Patient conditions such as obesity, sepsis, the need for laparoscopic surgery, or one-lung ventilation may benefit from intraoperative lung protective ventilation strategies. Anesthesiologists can use risk evaluation and prediction tools, monitor advanced physiologic targets, and incorporate new innovative monitoring techniques to develop an individualized approach for patients.

Hospital Variation in Mortality and Ventilator Management among Mechanically Ventilated Patients with ARDS

RATIONALE

Acute Respiratory Distress Syndrome (ARDS) is associated with significant mortality. Despite the mortality benefits of lung protective ventilation, adherence rates to evidence-based ventilator practice have remained low and ARDS mortality has remained high.

OBJECTIVE

Determine variation in ARDS mortality and adherence to low tidal volume ventilation (LTV) across US hospitals.

MATERIALS AND METHODS

We identified mechanically ventilated patients with ARDS using data from Philips eICU (2014-2015). We then used multi-variable hierarchical logistic regression models with hospital site as the random effect and patient and hospital level factors as fixed effects to assess the hospital risk adjusted mortality rate and median odds ratio for the association between mortality and hospital site. We then assessed associations between adherence to LTV (defined as 4-8 mL/kg PBW) and hospital risk adjusted mortality rates using Spearman correlation.

RESULTS

Among 4441 patients admitted at 110 hospitals with ARDS, the hospital risk-adjusted mortality rate ranged from 19% to 39%, and the MOR for hospital of admission was 1.33 (95% CI 1.25-1.41). Among 3070 patients at 72 hospitals with available ventilator data, 73% of patients had a median set Vt between 4 to 8 mL/kg PBW; hospital adherence rates to LTV ranged from 13% to 95%. There was no association between hospital adherence to LTV and risk-adjusted mortality rate (spearman correlation coefficient -0.01, p = .93). Similarly, among 956 patients who started with a Vt > 8 mL/kg PBW, there was no association between the percent of patients at each hospital whose Vt was decreased to ≤ 8 mL/kg PBW and risk adjusted mortality rate (spearman correlation coefficient .05, p = .73).

CONCLUSION

Risk adjusted mortality and use of LTV for patients with ARDS varied widely across hospitals. However, hospital adherence to LTV was not associated with ARDS mortality rates. Further evaluation of hospital practices associated with lower ARDS mortality are warranted.

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

BACKGROUND

Airway 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.

METHODS

In 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.

RESULTS

The 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 Pa_o2 (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.

CONCLUSIONS

In 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 REGISTRATION

NCT04260451.

Effect of facemask oxygenation with and without positive pressure ventilation on gastric volume during anesthesia induction in patients undergoing laparoscopic cholecystectomy or partial hepatectomy: a randomized controlled trial

BACKGROUND

Studies focusing on the relationship between gastric volume and facemask oxygenation without ventilation during apnea in anesthesia induction are scarce. This study compared the change in gastric volume during apnea in anesthesia induction using facemask ventilation and facemask oxygenation without ventilation in adults undergoing laparoscopic surgery.

METHODS

In this prospective, randomized, double-blinded trial, 70 adults undergoing laparoscopic surgery under general anesthesia were divided into two groups to receive facemask oxygenation with and without ventilation for 60 seconds after loss of consciousness. Before anesthesia induction and after endotracheal intubation, the gastric antral cross-sectional area was measured with ultrasound imaging. Arterial blood gases were tested at baseline (T1), after preoxygenation (T2), after loss of consciousness (T3), and before and after endotracheal intubation (T4 and T5, respectively).

RESULTS

Sixty patients were included (ventilation n = 30; non ventilation n = 30, 10 patients were excluded). The median [IQR] change of gastric antral cross-sectional area in ventilation group was significantly higher than in non ventilation group (0.83 [0.20 to 1.54] vs. 0.10 [- 0.11 to 0.56] cm₂, P = 0.001). At T4 and T5, the PaO₂ in ventilation group was significantly higher than in non ventilation group (T4: 391.83 ± 61.53 vs. 336.23 ± 74.99 mmHg, P < 0.01; T5: 364.00 ± 58.65 vs. 297.13 ± 86.95 mmHg, P < 0.01), while the PaCO₂ in non ventilation group was significantly higher (T4: 46.57 ± 5.78 vs. 37.27 ± 6.10 mmHg, P < 0.01; T5: 48.77 ± 6.59 vs. 42.63 ± 6.03 mmHg, P < 0.01) and the pH value in non ventilation group was significantly lower (T4: 7.35 ± 0.029 vs 7.42 ± 0.047, P < 0.01; T5: 7.34 ± 0.033 vs 7.39 ± 0.044, P < 0.01). At T4, the HCO₃^- in non ventilation group was significantly higher (25.79 ± 2.36 vs. 23.98 ± 2.18 mmol l^- 1, P < 0.01).

CONCLUSIONS

During apnoea, the increase in gastric volume was milder in patients undergoing facemask oxygenation without ventilation than with positive pressure ventilation.

TRIAL REGISTRATION

ChiCTR2100054193, 10/12/2021, Title: "Effect of positive pressure and non-positive pressure ventilation on gastric volume during induction of general anesthesia in laparoscopic surgery: a randomized controlled trial". Website: https://www.chictr.ogr.cn .

The impact of driving pressure on postoperative pulmonary complication in patients with different respiratory spirometry

Risk factors for postoperative pulmonary complication (PPC) have not been determined according to preoperative respiratory spirometry. Thus, we aimed to find contributors for PPC in patients with restrictive or normal spirometric pattern. We analyzed 654 patients (379 with normal and 275 with restrictive spirometric pattern). PPCs comprised respiratory failure, pleural effusion, atelectasis, respiratory infection, and bronchospasm. We analyzed the association between perioperative factors and PPC using binary logistic regression. In particular, we conducted subgroup analysis on the patients stratified according to preoperative spirometry. Of 654 patients, 27/379 patients (7.1%) with normal spirometric pattern and 33/275 patients (12.0%) with restrictive spirometric pattern developed PPCs. Multivariable analysis demonstrated that high driving pressure was the only intraoperative modifiable factor increasing PPC risk (OR = 1.13 [1.02-1.25], p = 0.025). In the subgroup of patients with restrictive spirometric pattern, intraoperative driving pressure was significantly associated with PPC (OR = 1.21 [1.05-1.39], p = 0.009), whereas driving pressure was not associated with PPC in patients with normal spirometric pattern (OR = 1.04 [0.89-1.21], p = 0.639). In patients with restrictive spirometric pattern, greater intraoperative driving pressure is significantly associated with increased PPC risk. In contrast, intraoperative driving pressure is not associated with PPC in patients with normal spirometric pattern.

Protective ventilation in a pig model of acute lung injury: timing is as important as pressure

Ventilator-induced lung injury (VILI) is a significant risk for patients with acute respiratory distress syndrome (ARDS). Management of the patient with ARDS is currently dominated by the use of low tidal volume mechanical ventilation, the presumption being that this mitigates overdistension (OD) injury to the remaining normal lung tissue. Evidence exists, however, that it may be more important to avoid cyclic recruitment and derecruitment (RD) of lung units, although the relative roles of OD and RD in VILI remain unclear. Forty pigs had a heterogeneous lung injury induced by Tween instillation and were randomized into four groups (n = 10 each) with higher (↑) or lower (↓) levels of OD and/or RD imposed using airway pressure release ventilation (APRV). OD was increased by setting inspiratory airway pressure to 40 cmH2O and lessened with 28 cmH2O. RD was attenuated using a short duration of expiration (∼0.45 s) and increased with a longer duration (∼1.0 s). All groups developed mild ARDS following injury. RD ↑ OD↑ caused the greatest degree of lung injury as determined by [Formula: see text]/[Formula: see text] ratio (226.1 ± 41.4 mmHg). RD ↑ OD↓ ([Formula: see text]/[Formula: see text]= 333.9 ± 33.1 mmHg) and RD ↓ OD↑ ([Formula: see text]/[Formula: see text] = 377.4 ± 43.2 mmHg) were both moderately injurious, whereas RD ↓ OD↓ ([Formula: see text]/[Formula: see text] = 472.3 ± 22.2 mmHg; P < 0.05) was least injurious. Both tidal volume and driving pressure were essentially identical in the RD ↑ OD↓ and RD ↓ OD↑ groups. We, therefore, conclude that considerations of expiratory time may be at least as important as pressure for safely ventilating the injured lung.NEW & NOTEWORTHY In a large animal model of ARDS, recruitment/derecruitment caused greater VILI than overdistension, whereas both mechanisms together caused severe lung damage. These findings suggest that eliminating cyclic recruitment and derecruitment during mechanical ventilation should be a preeminent management goal for the patient with ARDS. The airway pressure release ventilation (APRV) mode of mechanical ventilation can achieve this if delivered with an expiratory duration (TLow) that is brief enough to prevent derecruitment at end expiration.

In-line miniature 3D-printed pressure-cycled ventilator maintains respiratory homeostasis in swine with induced acute pulmonary injury

The COVID-19 pandemic demonstrated the need for inexpensive, easy-to-use, rapidly mass-produced resuscitation devices that could be quickly distributed in areas of critical need. In-line miniature ventilators based on principles of fluidics ventilate patients by automatically oscillating between forced inspiration and assisted expiration as airway pressure changes, requiring only a continuous supply of pressurized oxygen. Here, we designed three miniature ventilator models to operate in specific pressure ranges along a continuum of clinical lung injury (mild, moderate, and severe injury). Three-dimensional (3D)-printed prototype devices evaluated in a lung simulator generated airway pressures, tidal volumes, and minute ventilation within the targeted range for the state of lung disease each was designed to support. In testing in domestic swine before and after induction of pulmonary injury, the ventilators for mild and moderate injury met the design criteria when matched with the appropriate degree of lung injury. Although the ventilator for severe injury provided the specified design pressures, respiratory rate was elevated with reduced minute ventilation, a result of lung compliance below design parameters. Respiratory rate reflected how well each ventilator matched the injury state of the lungs and could guide selection of ventilator models in clinical use. This simple device could help mitigate shortages of conventional ventilators during pandemics and other disasters requiring rapid access to advanced airway management, or in transport applications for hands-free ventilation.

Acute respiratory distress syndrome in adults: diagnosis, outcomes, long-term sequelae, and management

Acute respiratory distress syndrome (ARDS) is characterised by acute hypoxaemic respiratory failure with bilateral infiltrates on chest imaging, which is not fully explained by cardiac failure or fluid overload. ARDS is defined by the Berlin criteria. In this Series paper the diagnosis, management, outcomes, and long-term sequelae of ARDS are reviewed. Potential limitations of the ARDS definition and evidence that could inform future revisions are considered. Guideline recommendations, evidence, and uncertainties in relation to ARDS management are discussed. The future of ARDS strives towards a precision medicine approach, and the framework of treatable traits in ARDS diagnosis and management is explored.

Ventilation during Lung Resection and Critical Care: Comparative Clinical Outcomes

Recent evidence suggests that outcomes do not meaningfully differ between thoracic surgery patients who are ventilated with a low or higher tidal volume and the effects of low versus higher positive end-expiratory pressure are unclear.

Effects of ultrasound-guided alveolar recruitment manoeuvres compared with sustained inflation or no recruitment manoeuvres on atelectasis in laparoscopic gynaecological surgery as assessed by ultrasonography: a randomized clinical trial

Background

The majority of patients may experience atelectasis under general anesthesia, and the Trendelenburg position and pneumoperitoneum can aggravate atelectasis during laparoscopic surgery, which promotes postoperative pulmonary complications. Lung recruitment manoeuvres have been proven to reduce perioperative atelectasis, but it remains controversial which method is optimal. Ultrasonic imaging can be conducive to confirming the effect of lung recruitment manoeuvres. The purpose of our study was to assess the effects of ultrasound-guided alveolar recruitment manoeuvres by ultrasonography on reducing perioperative atelectasis and to check whether the effects of recruitment manoeuvres under ultrasound guidance (visual and semiquantitative) on atelectasis are superior to sustained inflation recruitment manoeuvres (classical and widely used) in laparoscopic gynaecological surgery.

Methods

In this randomized, controlled, double-blinded study, women undergoing laparoscopic gynecological surgery were enrolled. Patients were randomly assigned to receive either lung ultrasound-guided alveolar recruitment manoeuvres (UD group), sustained inflation alveolar recruitment manoeuvres (SI group), or no RMs (C group) using a computer-generated table of random numbers. Lung ultrasonography was performed at four predefined time points. The primary outcome was the difference in lung ultrasound score (LUS) among groups at the end of surgery.

Results

Lung ultrasound scores in the UD group were significantly lower than those in both the SI group and the C group immediately after the end of surgery (7.67 ± 1.15 versus 9.70 ± 102, difference, -2.03 [95% confidence interval, -2.77 to -1.29], P < 0.001; 7.67 ± 1.15 versus 11.73 ± 1.96, difference, -4.07 [95% confidence interval, -4.81 to -3.33], P < 0.001;, respectively). The intergroup differences were sustained until 30 min after tracheal extubation (9.33 ± 0.96 versus 11.13 ± 0.97, difference, -1.80 [95% confidence interval, -2.42 to -1.18], P < 0.001; 9.33 ± 0.96 versus 10.77 ± 1.57, difference, -1.43 [95% confidence interval, -2.05 to -0.82], P < 0.001;, respectively). The SI group had a significantly lower LUS than the C group at the end of surgery (9.70 ± 1.02 versus 11.73 ± 1.96, difference, -2.03 [95% confidence interval, -2.77 to -1.29] P < 0.001), but the benefit did not persist 30 min after tracheal extubation.

Conclusions

During general anesthesia, ultrasound-guided recruitment manoeuvres can reduce perioperative aeration loss and improve oxygenation. Furthermore, these effects of ultrasound-guided recruitment manoeuvres on atelectasis are superior to sustained inflation recruitment manoeuvres.

Trial registration

Chictr.org.cn, ChiCTR2100042731, Registered 27 January 2021, www.chictr.org.cn.

Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) occurs in up to 10% of patients with respiratory failure admitted through the emergency department. Use of noninvasive respiratory support has proliferated in recent years; clinicians must understand the relative merits and risks of these technologies and know how to recognize signs of failure. The cornerstone of ARDS care of the mechanically ventilated patient is low-tidal volume ventilation based on ideal body weight. Adjunctive therapies, such as prone positioning and neuromuscular blockade, may have a role in the emergency department management of ARDS depending on patient and department characteristics.

ARDS Clinical Practice Guideline 2021

BACKGROUND

The joint committee of the Japanese Society of Intensive Care Medicine/Japanese Respiratory Society/Japanese Society of Respiratory Care Medicine on ARDS Clinical Practice Guideline has created and released the ARDS Clinical Practice Guideline 2021.

METHODS

The 2016 edition of the Clinical Practice Guideline covered clinical questions (CQs) that targeted only adults, but the present guideline includes 15 CQs for children in addition to 46 CQs for adults. As with the previous edition, we used a systematic review method with the Grading of Recommendations Assessment Development and Evaluation (GRADE) system as well as a degree of recommendation determination method. We also conducted systematic reviews that used meta-analyses of diagnostic accuracy and network meta-analyses as a new method.

RESULTS

Recommendations for adult patients with ARDS are described: we suggest against using serum C-reactive protein and procalcitonin levels to identify bacterial pneumonia as the underlying disease (GRADE 2D); we recommend limiting tidal volume to 4-8 mL/kg for mechanical ventilation (GRADE 1D); we recommend against managements targeting an excessively low SpO2 (PaO2) (GRADE 2D); we suggest against using transpulmonary pressure as a routine basis in positive end-expiratory pressure settings (GRADE 2B); we suggest implementing extracorporeal membrane oxygenation for those with severe ARDS (GRADE 2B); we suggest against using high-dose steroids (GRADE 2C); and we recommend using low-dose steroids (GRADE 1B). The recommendations for pediatric patients with ARDS are as follows: we suggest against using non-invasive respiratory support (non-invasive positive pressure ventilation/high-flow nasal cannula oxygen therapy) (GRADE 2D), we suggest placing pediatric patients with moderate ARDS in the prone position (GRADE 2D), we suggest against routinely implementing NO inhalation therapy (GRADE 2C), and we suggest against implementing daily sedation interruption for pediatric patients with respiratory failure (GRADE 2D).

CONCLUSIONS

This article is a translated summary of the full version of the ARDS Clinical Practice Guideline 2021 published in Japanese (URL: https://www.jsicm.org/publication/guideline.html ). The original text, which was written for Japanese healthcare professionals, may include different perspectives from healthcare professionals of other countries.