Early Acute Respiratory Distress Syndrome Research Articles

The impact and validity of the Berlin criteria on burn-induced ARDS: Examining mortality rates, and inhalation injury influences. A single center observational cohort study

BackgroundAs several recent studies have shown low mortality rates in burn injury induced ARDS early (≤7 days) after the burn, the Berlin criteria for the ARDS diagnosis in this setting may be disputed. Related to this issue, the present study investigated the incidence, trajectory and risk factors of early Acute Respiratory Distress Syndrome (ARDS) and outcome in burn patients, as per the Berlin criteria, along with the concurrent prevalence and influence of inhalation injury, and ventilator-acquired pneumonia (VAP). MethodsOver a 2.5-year period, burn patients with Total Burn Surface Area (TBSA) exceeding 10% admitted to a national burn center were included. The subgroup of interest comprised patients with more than 48 h of ventilatory support. This group was assessed for ARDS, inhalation injury, and VAP. ResultsOut of 292 admissions, 62 sustained burns > 10% TBSA. Of these, 28 (45%) underwent ventilatory support for over 48 h, almost all, 24 out of 28, meeting the criteria for ARDS early, within 7 days post-injury and with a PaO2/FiO2 (PF) ratio nadir at day 5. The mortality rate for this early ARDS group was under 10%, regardless of PF ratios (mean TBSA% 34,8%). Patients with concurrent inhalation injury and early ARDS showed significantly lower PF ratios (p < 0.001), and higher SOFA scores (p = 0.004) but without impact on mortality. Organ failure, indicated by SOFA scores, peaked early (day 3) and declined in the first week, mirroring PF ratio trends (p < 0.001). ConclusionsThe low mortality associated with early ARDS in burn patients in this study challenges the Berlin criteria’s for the early ARDS diagnosis, which for its validity relies on that higher mortality is linked to worsening PF ratios. The finding suggests alternative mechanisms, leading to the early ARDS diagnosis, such as the significant impact of inhalation injury on early PF ratios and organ failure, as seen in this study. The concurrence of early organ failure with declining PF ratios, supports, as expected, the hypothesis of trauma-induced inflammation/multi-organ failure mechanisms contributing to early ARDS. The study highlights the complexity in differentiating between the contributions of inhalation injury to early ARDS and the related organ dysfunction early in the burn care trajectory. The Berlin criteria for the ARDS diagnosis may not be fully applicable in the burn care setting, where the low mortality significantly deviates from that described in the original Berlin ARDS criteria publication but is as expected when considering the actual not very extensive burn injury sizes/Baux scores as in the present study.

Regional pulmonary perfusion, blood volume, and their relationship change in experimental early ARDS

Regional pulmonary perfusion (Q) has been investigated using blood volume (Fb) imaging as an easier-to-measure surrogate. However, it is unclear if changing pulmonary conditions could affect their relationship. We hypothesized that vascular changes in early acute respiratory distress syndrome (ARDS) affect Q and Fb differently. Five sheep were anesthetized and received lung protective mechanical ventilation for 20 h while endotoxin was continuously infused. Using dynamic 18F-FDG and 13NN Positron Emission Tomography (PET), regional Fb and Q were analysed in 30 regions of interest (ROIs) and normalized by tissue content (Fbn and Qn, respectively). After 20 h, the lung injury showed characteristics of early ARDS, including gas exchange and lung mechanics. PET images of Fbn and Qn showed substantial differences between baseline and lung injury. Lung injury caused a significant change in the Fbn-Qn relationship compared to baseline (p < 0.001). The best models at baseline and lung injury were Fbn = 0.32 + 0.690Qn and Fbn = 1.684Qn–0.538Qn2, respectively. Endotoxine-associated early ARDS changed the relationship between Fb and Q, shifting from linear to curvilinear. Effects of endotoxin exposure on the vasoactive blood flow regulation were most likely the key factor for this change limiting the quantitative accuracy of Fb imaging as a surrogate for regional Q.

A combination of mild-moderate hypoxemia and low compliance is highly prevalent in persistent ARDS: a retrospective study

BackgroundThe Acute Respiratory Distress Syndrome (ARDS) is characterized by lung inflammation and edema, impairing both oxygenation and lung compliance. Recent studies reported a dissociation between oxygenation and compliance (severe hypoxemia with preserved compliance) in early ARDS and COVID-19-related-ARDS (CARDS). During the pandemic, in patients requiring prolonged mechanical ventilation, we observed the opposite combination (mild-moderate hypoxemia but significantly impaired compliance). The purpose of our study was to investigate the prevalence of this combination of mild-moderate hypoxemia and impaired compliance in persistent ARDS and CARDS.MethodsFor this retrospective study, we used individual patient-level data from two independent cohorts of ARDS patients. The ARDSNet cohort included patients from four ARDS Network randomized controlled trials. The CARDS cohort included patients with ARDS due to COVID-19 hospitalized in two intensive care units in Greece. We used a threshold of 150 for PaO2/FiO2 and 30 ml/cmH2O for compliance, estimated the prevalence of each of the four combinations of oxygenation and compliance at baseline, and examined the change in its prevalence from baseline to day 21 in the ARDSNet and CARDS cohorts.ResultsThe ARDSNet cohort included 2909 patients and the CARDS cohort included 349 patients. The prevalence of the combination of mild-moderate hypoxemia and low compliance increased from baseline to day 21 both in the ARDSNet cohort (from 22.2 to 42.7%) and in the CARDS cohort (from 3.1 to 33.3%). Among surviving patients with low compliance, oxygenation improved over time. The 60-day mortality rate was higher for patients who had mild-moderate hypoxemia and low compliance on day 21 (28% and 56% in ARDSNet and CARDS), compared to those who had mild-moderate hypoxemia and high compliance (20% and 50%, respectively).ConclusionsAmong patients with ARDS who require prolonged controlled mechanical ventilation, regardless of ARDS etiology, a dissociation between oxygenation and compliance characterized by mild-moderate hypoxemia but low compliance becomes increasingly prevalent. The findings of this study highlight the importance of monitoring mechanics in patients with persistent ARDS.

Expression and significance of serum KL-6 in patients with acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is a common and serious complication that occurs in the ICU. the determination of early ARDS indicators, along with timely treatment, can potentially diminish medical costs and reduce ARDS-related mortality. In this report, we evaluated the clinical significance of circulating Krebs von den Lungen-6 (KL-6) content among patients with intra- and extrapulmonary ARDS to investigate the clinical significance of serum KL-6. Patients who met the ARDS Berlin criteria and were hospitalized in the intensive care unit of the China-Japan Union Hospital of Jilin University between September 2021 and September 2022 were recruited for analysis. ARDS patients were divided into an intrapulmonary ARDS group (n=23) and an extrapulmonary ARDS group (n=27) based on their primary diagnosis. Baseline demographic data, including age and sex, and clinical data, including underlying diseases and mortality, of the two groups were collected and analyzed. Peripheral venous blood was collected on Day 0 (baseline), Day 1, Day 3, and Day 7. The kinetic levels of serum KL-6 were compared between patients who survived and those who died within one week of ARDS diagnosis. The prognosis, survival times, and status of patients within 28 days after diagnosis were evaluated. In the intrapulmonary ARDS group, patients who died had significantly higher serum KL-6 levels in the seven days following diagnosis than those who survived. In contrast, in the extrapulmonary group, the difference in KL-6 values between patients who survived and died was only significant on the first day after diagnosis. The peak levels of serum KL-6 in the death group were significantly higher than those in the survival group for both intra- and extrapulmonary ARDS (P=0.0253). The optimal cutoff value of the serum KL-6 level was 1,452.3 U/mL in intrapulmonary ARDS patients and 828.2 U/mL in extrapulmonary patients. Serum KL-6 levels higher than the cutoff levels were confirmed to be a significant prognostic predictor of poor survival within 28 days of diagnosis in patients with intra- and extrapulmonary ARDS. The serum KL-6 level is potentially a good indicator for predicting the prognosis of patients with ARDS.

An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.

Background: This document updates previously published Clinical Practice Guidelines for the management of patients with acute respiratory distress syndrome (ARDS), incorporating new evidence addressing the use of corticosteroids, venovenous extracorporeal membrane oxygenation, neuromuscular blocking agents, and positive end-expiratory pressure (PEEP). Methods: We summarized evidence addressing four "PICO questions" (patient, intervention, comparison, and outcome). A multidisciplinary panel with expertise in ARDS used the Grading of Recommendations, Assessment, Development, and Evaluation framework to develop clinical recommendations. Results: We suggest the use of: 1) corticosteroids for patients with ARDS (conditional recommendation, moderate certainty of evidence), 2) venovenous extracorporeal membrane oxygenation in selected patients with severe ARDS (conditional recommendation, low certainty of evidence), 3) neuromuscular blockers in patients with early severe ARDS (conditional recommendation, low certainty of evidence), and 4) higher PEEP without lung recruitment maneuvers as opposed to lower PEEP in patients with moderate to severe ARDS (conditional recommendation, low to moderate certainty), and 5) we recommend against using prolonged lung recruitment maneuvers in patients with moderate to severe ARDS (strong recommendation, moderate certainty). Conclusions: We provide updated evidence-based recommendations for the management of ARDS. Individual patient and illness characteristics should be factored into clinical decision making and implementation of these recommendations while additional evidence is generated from much-needed clinical trials.

Mesenchymal stem cell therapy modulates macrophage dynamics in ARDS-associated liver injury in rats

Acute Respiratory Distress Syndrome (ARDS) is a life-threatening pulmonary condition characterized by severe hypoxemia and respiratory failure. Beyond its devastating impact on the lungs, ARDS often triggers systemic responses affecting vital organs throughout the body. One such organ commonly affected is the liver, which experiences various degrees of injury during the course of ARDS. Pathophysiological changes in liver during ARDS, particularly polarization of Kupffer cells during the disease and its treatment, have drawn increasing attention. Purpose. To explore the macrophage transformation in liver injury associated with ARDS and investigate the potential of mesenchymal stem cell (MSC) therapy as a means to modulate macrophage responses and mitigate liver injury. Materials and methods. 72 mature male Wistar rats were randomly allocated to nine experimental groups as follows: the control group, groups assessed at 3 days, 7 days, and 28 days following intranasal LPS administration, groups that received 24 hours of LPS followed by 2 days of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs), groups exposed to 4 days of LPS and 3 days of hUC-MSCs, groups subjected to 14 days of LPS and 14 days of hUC-MSCs, groups treated with LPS 21 days and 7 days with hUC-MSCs injection, and a control group assessed 3 days after hUC-MSCs injection. For the administration of hUC-MSCs, intraperitoneal injections were performed at a dose of 1∙106 cells/kg body weight. Immunohistochemistry was employed to analyze macrophage subpopulations in liver tissues. Animal experiments adhered to ethical guidelines. Results. Early ARDS stages showed increased M1 macrophages, indicating pro-inflammatory responses, while later stages showed M2 macrophage activation, suggestive of anti-inflammatory and tissue repair roles. MSC administration facilitated the transition from M1 to M2 macrophages, promoting an anti-inflammatory milieu. Conclusions. MSCs demonstrate the potential to modulate macrophage polarization into M2 anti-inflammatory phenotype. Such findings reflect one of the mechanisms of MSC action which holds practical significance for future ARDS therapies, aiming to mitigate excessive inflammation and enhance tissue repair.

Effects of early versus delayed application of prone position on ventilation–perfusion mismatch in patients with acute respiratory distress syndrome: a prospective observational study

BackgroundProne position has been shown to improve oxygenation and survival in patients with early acute respiratory distress syndrome (ARDS). These beneficial effects are partly mediated by improved ventilation/perfusion (V/Q) distribution. Few studies have investigated the impact of early versus delayed proning on V/Q distribution in patients with ARDS. The aim of this study was to assess the regional ventilation and perfusion distribution in early versus persistent ARDS after prone position.MethodsThis is a prospective, observational study from June 30, 2021, to October 1, 2022 at the medical ICU in Zhongda Hospital, Southeast University. Fifty-seven consecutive adult patients with moderate-to-severe ARDS ventilated in supine and prone position. Electrical impedance tomography was used to study V/Q distribution in the supine position and 12 h after a prone session.ResultsOf the 57 patients, 33 were early ARDS (≤ 7 days) and 24 were persistent ARDS (> 7 days). Oxygenation significantly improved after proning in early ARDS (157 [121, 191] vs. 190 [164, 245] mm Hg, p < 0.001), whereas no significant change was found in persistent ARDS patients (168 [136, 232] vs.177 [155, 232] mm Hg, p = 0.10). Compared to supine position, prone reduced V/Q mismatch in early ARDS (28.7 [24.6, 35.4] vs. 22.8 [20.0, 26.8] %, p < 0.001), but increased V/Q mismatch in persistent ARDS (23.8 [19.8, 28.6] vs. 30.3 [24.5, 33.3] %, p = 0.006). In early ARDS, proning significantly reduced shunt in the dorsal region and dead space in the ventral region. In persistent ARDS, proning increased global shunt. A significant correlation was found between duration of ARDS onset to proning and the change in V/Q distribution (r = 0.54, p < 0.001).ConclusionsProne position significantly reduced V/Q mismatch in patients with early ARDS, while it increased V/Q mismatch in persistent ARDS patients.Trial registration ClinicalTrials.gov (NCT05207267, principal investigator Ling Liu, date of registration 2021.08.20).

Design and rationale of the CHILL phase II trial of hypothermia and neuromuscular blockade for acute respiratory distress syndrome

The Cooling to Help Injured Lungs (CHILL) trial is an open label, two group, parallel design multicenter, randomized phase IIB clinical trial assessing the efficacy and safety of targeted temperature management with combined external cooling and neuromuscular blockade to block shivering in patients with early moderate-severe acute respiratory distress syndrome (ARDS). This report provides the background and rationale for the clinical trial and outlines the methods using the Consolidated Standards of Reporting Trials guidelines. Key design challenges include: [1] protocolizing important co-interventions; [2] incorporation of patients with COVID-19 as the cause of ARDS; [3] inability to blind the investigators; and [4] ability to obtain timely informed consent from patients or legally authorized representatives early in the disease process. Results of the Reevaluation of Systemic Early Neuromuscular Blockade (ROSE) trial informed the decision to mandate sedation and neuromuscular blockade only in the group assigned to therapeutic hypothermia and proceed without this mandate in the control group assigned to a usual temperature management protocol. Previous trials conducted in National Heart, Lung, and Blood Institute ARDS Clinical Trials (ARDSNet) and Prevention and Early Treatment of Acute Lung Injury (PETAL) Networks informed ventilator management, ventilation liberation and fluid management protocols. Since ARDS due to COVID-19 is a common cause of ARDS during pandemic surges and shares many features with ARDS from other causes, patients with ARDS due to COVID-19 are included. Finally, a stepwise approach to obtaining informed consent prior to documenting critical hypoxemia was adopted to facilitate enrollment and reduce the number of candidates excluded because eligibility time window expiration.

THE IL-33/ST2 AXIS PROMOTES ACUTE RESPIRATORY DISTRESS SYNDROME BY NATURAL KILLER T CELLS.

Acute respiratory distress syndrome (ARDS) is characterized by uncontrolled inflammation, which manifests as leukocyte infiltration and lung injury. However, the molecules that initiate this infiltration remain incompletely understood. We evaluated the effect of the nuclear alarmin IL-33 on lung damage and the immune response in LPS-induced lung injury. We established a LPS-induced lung injury mouse model. We used genetically engineered mice to investigate the relationship among the IL-33/ST2 axis, NKT cells, and ARDS. We found that IL-33 was localized to the nucleus in alveolar epithelial cells, from which it was released 1 h after ARDS induction in wild-type (WT) mice. Mice lacking IL-33 (IL-33 - / - ) or ST2 (ST2 - / - ) exhibited reduced neutrophil infiltration, alveolar capillary leakage, and lung injury in ARDS compared with WT mice. This protection was associated with decreased lung recruitment and activation of invariant nature killer (iNKT) cells and activation of traditional T cells. Then, we validated that iNKT cells were deleterious in ARDS in CD1d - / - and Vα14Τg mice. Compared with WT mice, Vα14Τg mice exhibited increased lung injury in ARDS, and the CD1d - / - mice showed outcomes opposite those of the Vα14Τg mice. Furthermore, we administered a neutralizing anti-ST2 antibody to LPS-treated WT and Vα14Τg mice 1 h before LPS administration. We found that IL-33 promoted inflammation through NKT cells in ARDS. In summary, our results demonstrated that the IL-33/ST2 axis promotes the early uncontrolled inflammatory response in ARDS by activating and recruiting iNKT cells. Therefore, IL-33 and NKT cells may be therapeutic target molecules and immune cells, respectively, in early ARDS cytokine storms.

Association between serum HMGB1 elevation and early pediatric acute respiratory distress syndrome: a retrospective study of pediatric living donor liver transplant recipients with biliary atresia in China

BackgroundHigh mobility group box 1 (HMGB1) protein is one of the main risk factors for pediatric acute respiratory distress syndrome (PARDS) after living donor liver transplantation (LDLT). However, studies of the relationship between HMGB1 and PARDS are lacking. We evaluated the link between anomalies of intraoperative serum HMGB1 and PARDS in pediatric LDLT recipients with biliary atresia during the first week after transplant.MethodsData for 210 pediatric patients with biliary atresia who underwent LDLT between January 2018 and December 2021 were reviewed retrospectively. The main measure was serum HMGB1 levels 30 min after reperfusion, while the outcome was early PARDS after LDLT. Data including pretransplant conditions, laboratory indexes, variables of intraoperation, clinical complications, and outcomes after LDLT were analyzed for each patient. Univariate analysis of PARDS and multivariate logistic regression analyses of serum HMGB1 levels at 30 min in the neohepatic phase in the presence of PARDS were conducted to examine the potential associations. Subgroup interaction analyses and linear relationships between intraoperative serum HMGB1 levels and PARDS were also performed.ResultsAmong the participants, 55 had PARDS during 7 days after LDLT, including four in the first HMGB1 tertile (4.3–8.1 pg/mL), 18 in the second tertile (8.2–10.6 pg/mL), and 33 in the third tertile (10.6–18.8 pg/mL). The nonadjusted association between intraoperative HMGB1 levels and PARDS was positive (odds ratio 1.41, 95% confidence intervals 1.24–1.61, P < 0.0001). The association remained unchanged after adjustment for age, weight, pretransplant total bilirubin, albumin, graft cold ischemia time, and intraoperative blood loss volume (odds ratio 1.28, 95% confidence interval 1.10–1.49, P = 0.0017). After controlling for potential confounders, the association between intraoperative HMGB1 levels and PARDS remained positive, as well as in the subgroup analyses.ConclusionsSerum HMGB1 levels at 30 min after reperfusion were positively associated with early PARDS among pediatric patients with biliary atresia who had undergone LDLT. Identifying such patients early may increase the efficacy of perioperative respiratory management.

Real-time effects of lateral positioning on regional ventilation and perfusion in an experimental model of acute respiratory distress syndrome.

Low-volume lung injury encompasses local concentration of stresses in the vicinity of collapsed regions in heterogeneously ventilated lungs. We aimed to study the effects on ventilation and perfusion distributions of a sequential lateral positioning (30°) strategy using electrical impedance tomography imaging in a porcine experimental model of early acute respiratory distress syndrome (ARDS). We hypothesized that such strategy, including a real-time individualization of positive end-expiratory pressure (PEEP) whenever in lateral positioning, would provide attenuation of collapse in the dependent lung regions. A two-hit injury acute respiratory distress syndrome experimental model was established by lung lavages followed by injurious mechanical ventilation. Then, all animals were studied in five body positions in a sequential order, 15min each: Supine 1; Lateral Left; Supine 2; Lateral Right; Supine 3. The following functional images were analyzed by electrical impedance tomography: ventilation distributions and regional lung volumes, and perfusion distributions. The induction of the acute respiratory distress syndrome model resulted in a marked fall in oxygenation along with low regional ventilation and compliance of the dorsal half of the lung (gravitational-dependent in supine position). Both the regional ventilation and compliance of the dorsal half of the lung greatly increased along of the sequential lateral positioning strategy, and maximally at its end. In addition, a corresponding improvement of oxygenation occurred. In conclusion, our sequential lateral positioning strategy, with sufficient positive end-expiratory pressure to prevent collapse of the dependent lung units during lateral positioning, provided a relevant diminution of collapse in the dorsal lung in a porcine experimental model of early acute respiratory distress syndrome.

Developing and evaluating a machine-learning-based algorithm to predict the incidence and severity of ARDS with continuous non-invasive parameters from ordinary monitors and ventilators

ObjectivesMajor observational studies report that the mortality rate of acute respiratory distress syndrome (ARDS) is close to 40%. Different treatment strategies are required for each patient, according to the degree of ARDS. Early prediction of ARDS is helpful to implement targeted drug therapy and mechanical ventilation strategies for patients with different degrees of potential ARDS. In this paper, a new dynamic prediction machine learning model for ARDS incidence and severity is established and evaluated based on 28 parameters from ordinary monitors and ventilators, capable of dynamic prediction of the incidence and severity of ARDS. This new method is expected to meet the clinical practice requirements of user-friendliness and timeliness for wider application. MethodsA total of 4738 hospitalized patients who required ICU care from 159 hospitals are employed in this study. The models are trained by standardized data from electronic medical records. There are 28 structured, continuous non-invasive parameters that are recorded every hour. Seven machine learning models using only continuous, non-invasive parameters are developed for dynamic prediction and compared with methods trained by complete parameters and the traditional risk adjustment method (i.e., oxygenation saturation index method). ResultsThe optimal prediction performance (area under the curve) of the ARDS incidence and severity prediction models built using continuous noninvasive parameters reached0.8691 and 0.7765, respectively. In terms of mild and severe ARDS prediction, the AUC values are both above 0.85. The performance of the model using only continuous non-invasive parameters have an AUC of 0.0133 lower, in comparison with that employing a complete feature set, including continuous non-invasive parameters, demographic information, laboratory parameters and clinical natural language text. ConclusionsA machine learning method was developed in this study using only continuous non-invasive parameters for ARDS incidence and severity prediction. Because the continuous non-invasive parameters can be easily obtained from ordinary monitors and ventilators, the method presented in this study is friendly and convenient to use. It is expected to be applied in pre-hospital setting for early ARDS warning.

Role of Hypertonic Saline Nebulization Therapy in Patients with Early Acute Respiratory Distress Syndrome

Role of Hypertonic Saline Nebulization Therapy in Patients with Early Acute Respiratory Distress Syndrome

Does Interrupting Self-Induced Lung Injury and Respiratory Drive Expedite Early Spontaneous Breathing in the Setting of Early Severe Diffuse Acute Respiratory Distress Syndrome?

Does Interrupting Self-Induced Lung Injury and Respiratory Drive Expedite Early Spontaneous Breathing in the Setting of Early Severe Diffuse Acute Respiratory Distress Syndrome?

Biphasic positive airway pressure spontaneous breathing attenuates lung injury in an animal model of severe acute respiratory distress syndrome

ObjectiveTo compare the effects of unassisted spontaneous breathing (SB) and complete muscle paralysis (PC) on early severe acute respiratory distress syndrome (ARDS) in an animal model, and to explore the possibility of biphasic positive airway pressure (BIPAP) as lung protective ventilation support for patients in the early stage of severe ARDS.MethodsTwelve healthy beagle dogs between the ages of 10 and 15 months were randomly divided into two groups: the SB group (BIPAPSB) and the PC group (BIPAPPC). Arterial blood samples were drawn before modelling. Arterial blood gas analysis and mechanical tests were conducted. The animal model of severe ARDS was established using a deep intravenous injection of oleic acid, and BIPAP ventilation was performed for 8 hours. Lung tissue and blood were taken to detect lung function, inflammatory reactions and degree of pathological damage.ResultsAt the beginning of the experiment, there was no significant difference in the arterial blood gas analysis between the two groups (p > 0.05). After successful modelling, the oxygenation index and the end-expiratory lung volume in the SB group were significantly higher than those in the PC group 8 hours after MV. Pathologically, the wet-dry ratio and pathological score of the PC group were higher than those of the SB group; the lung injury in the gravity-dependent area in the SB group was less than that in the PC group (p< 0.05).ConclusionsIn the early stage of severe ARDS induced by oleic acid, compared with PC, retention of the BIPAP mode of SB can reduce the risk of lung injury and improve respiratory function.

Effects of High-Resolution CT Changes on Prognosis Predictability in Acute Respiratory Distress Syndrome with Diffuse Alveolar Damage

Diffuse alveolar damage (DAD) is the pathological hallmark of acute respiratory distress syndrome (ARDS). DAD is independently correlated with higher mortality compared with the absence of DAD. Traction bronchiectasis in areas of ground-glass opacity or consolidation is associated with the late fibroproliferative or fibrotic phase of DAD. This study examined whether the 60-day mortality related to DAD could be predicted using high-resolution computed tomography (HRCT) findings and HRCT scores. A total of 34 patients with DAD who received HRCT within 7 days of ARDS diagnosis were enrolled; they were divided into a 60-day survival group and a nonsurvival group, with 17 patients in each group. Univariate and multivariate binary regression analyses and the receiver operating characteristic curve revealed that only the total percentage of the area with traction bronchiectasis or bronchiolectasis was an independent predictor of 60-day mortality (odds ratio, 1.067; 95% confidence interval (CI), 1.011–1.126) and had favorable predictive performance (area under the curve (AUC): 0.784; 95% CI, 0.621–0.946; cutoff, 21.7). Physiological variables, including age, days from ARDS to HRCT, the sequential organ failure assessment (SOFA) score, the PaO2/fraction of inspired oxygen (FiO2) ratio, dynamic driving pressure, and dynamic mechanical power, were not discriminative between 60-day survival and nonsurvival. In conclusion, the extent of fibroproliferation on HRCT in early ARDS, presented as the total percentage of area with bronchiectasis or bronchiolectasis, is an independent positive predictor with a favorable predictive ability for the 60-day mortality of DAD.

Clinical study on the relationship between the exosomes in bronchoalveolar lavage fluid and plasma and the severity of lung injury and outcome in early acute respiratory distress syndrome patients

Objective: To investigate the relationship between the levels of exosomes in bronchoalveolar lavage fluid (BALF) and plasma and the severity of lung injury and its outcome in patients with acute respiratory distress syndrome (ARDS). Methods: Patients who were admitted to the Department of Critical Care Medicine, Zhongda Hospital Affiliated to Southeast University and received invasive mechanical ventilation were selected from August 2020 to April 2021, and they were divided into ARDS group and non-ARDS group. Finally, 33 ARDS patients were included, including 18 males and 15 females, aged (65.5±15.5) years; 10 non-ARDS patients, 8 males and 2 females, aged (57.2±15.3) years. The BALF and plasma of the two groups of patients were collected within 24 hours after enrollment, and the total exosomes of the samples were collected by ultracentrifugation. Nanoparticle tracking analysis (NTA) was used to detect and compare the differences in exosome content between the two groups. Correlation of content with the severity and prognosis of lung injury in ARDS patients. Results: There was no significant difference in gender and age between ARDS group and non-ARDS group (both P>0.05). The exosome in plasma of ARDS group was significantly higher than that of non-ARDS group [(25.3±1.2)/ml vs (24.2±1.6)/ml, P=0.031], while the exosomes in BALF of ARDS group was also higher than that of non-ARDS group [(26.5±1.6)/ml vs (24.6±1.1)/ml, P=0.001]. The exosomes in BALF of patients with ARDS caused by intrapulmonary causes was higher than that in ARDS group caused by extrapulmonary causes [(26.9±1.5)/ml vs (25.2±0.9)/ml, P=0.01], and the infection caused by bacterial shows that the highest exosome level in BALF. The exosomes in the BALF of the mild ARDS group was significantly lower than that of the severe ARDS group [(25.7±1.3)/ml vs (27.2±1.5)/ml, P=0.038]; the exosomes in BALF of ARDS patients was negatively correlated with P/F ratio (r=-0.38, P=0.03); and it was positively correlated with Murray lung injury score (r=0.47, P=0.01). However, the static compliance levels, length of hospital stay, duration of mechanical ventilation, and 28-day outcome were not associated with the exosomes in BALF. Conclusion: Compared with non-ARDS patients, ARDS patients have significantly higher levels of exosomes in BALF and plasma, there is a certain correlation between exosomes derived from BALF and the severity of lung injury in ARDS.

Individualized positive end-expiratory pressure guided by end-expiratory lung volume in early acute respiratory distress syndrome: study protocol for the multicenter, randomized IPERPEEP trial

BackgroundIn acute respiratory distress syndrome (ARDS), response to positive end-expiratory pressure (PEEP) is variable according to different degrees of lung recruitability. The search for a tool to individualize PEEP based on patients’ individual response is warranted.End-expiratory lung volume (EELV) assessment by nitrogen washin-washout aids bedside estimation of PEEP-induced alveolar recruitment and may therefore help titrate PEEP on patient’s individual recruitability.We designed a randomized trial to test whether an individualized PEEP setting protocol driven by EELV measurement may improve a composite clinical outcome in patients with moderate-to-severe ARDS (IPERPEEP trial).MethodsIPERPEEP is an open-label, multicenter, randomized trial that will be conducted in 10 intensive care units in Italy and will enroll 132 ARDS patients showing PaO2/FiO2 ratio ≤ 150 mmHg within 24 h from endotracheal intubation while on mechanical ventilation with PEEP 5 cmH2O.To standardize lung volumes at study initiation, all patients will undergo mechanical ventilation with tidal volume of 6 ml/kg of predicted body weight and PEEP set to obtain a plateau pressure within 28 and 30 cmH2O for 30 min (EXPRESS PEEP).Afterwards, a 5-step decremental PEEP trial will be conducted (EXPRESS PEEP to PEEP 5 cmH2O), and EELV will be measured at each step. Recruitment-to-inflation ratio will be calculated for each PEEP range from EELV difference. Patients will be then randomized to receive mechanical ventilation with PEEP set according to the optimal recruitment observed in the PEEP trial (IPERPEEP arm) trial or to achieve a plateau pressure of 28–30 cmH2O (control arm, EXPRESS strategy). In both groups, tidal volume size, use of prone positioning and neuromuscular blocking agents, and weaning from PEEP and from mechanical ventilation will be standardized.The primary endpoint of the study is a composite clinical outcome incorporating in-ICU mortality, 60-day ventilator-free days, and serum interleukin-6 concentration over the course of the initial 72 h of treatment.DiscussionThe IPERPEEP study is a randomized trial powered to elucidate whether an individualized PEEP setting protocol based on bedside assessment of lung recruitability can improve a composite clinical outcome during moderate-to-severe ARDS.Trial registrationClinicalTrials.govNCT04012073. Registered 9 July 2019.

Fatal COVID-19 and Non–COVID-19 Acute Respiratory Distress Syndrome Is Associated with Incomplete Alveolar Type 1 Epithelial Cell Differentiation from the Transitional State without Fibrosis

Acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 and other etiologies results from injury to the alveolar epithelial cell (AEC) barrier resulting in noncardiogenic pulmonary edema, which causes acute respiratory failure; recovery requires epithelial regeneration. During physiological regeneration in mice, type 2 AECs (AEC2s) proliferate, exit the cell cycle, transiently assume a transitional state, then differentiate into type 1 AECs (AEC1s); in humans, persistence of the transitional state is associated with pulmonary fibrosis. It is unknown whether transitional cells emerge and differentiate into AEC1s without fibrosis in human ARDS and why transitional cells differentiate into AEC1s during physiological regeneration but persist in fibrosis. We hypothesized that incomplete but ongoing AEC1 differentiation from transitional cells without fibrosis may underlie persistent barrier permeability and acute respiratory failure in ARDS. Immunostaining of postmortem ARDS lungs revealed abundant transitional cells without fibrosis. They were typically cuboidal or partially spread, sometimes flat, and occasionally expressed AEC1 markers. Immunostaining and/or single-cell RNA sequencing revealed that transitional cells in mouse models of physiological regeneration, ARDS, and fibrosis express markers of cell cycle exit but only in fibrosis express a specific senescence marker. Thus, in severe, fatal early ARDS, AEC1 differentiation from transitional cells is incomplete, underlying persistent barrier permeability and respiratory failure but ongoing without fibrosis; senescence of transitional cells may be associated with pulmonary fibrosis.

Maintenance of low driving pressure in patients with early acute respiratory distress syndrome significantly affects outcomes

BackgroundDriving pressure (∆P) is an important factor that predicts mortality in acute respiratory distress syndrome (ARDS). We test the hypothesis that serial changes in daily ΔP rather than Day 1 ΔP would better predict outcomes of patients with ARDS.MethodsThis retrospective cohort study enrolled patients admitted to five intensive care units (ICUs) at a medical center in Taiwan between March 2009 and January 2018 who met the criteria for ARDS and received the lung-protective ventilation strategy. ∆P was recorded daily for 3 consecutive days after the diagnosis of ARDS, and its correlation with 60-day survival was analyzed.ResultsA total of 224 patients were enrolled in the final analysis. The overall ICU and 60-day survival rates were 52.7% and 47.3%, respectively. ∆P on Days 1, 2, and 3 was significantly lower in the survival group than in the nonsurvival group (13.8 ± 3.4 vs. 14.8 ± 3.7, p = 0.0322, 14 ± 3.2 vs. 15 ± 3.5, p = 0.0194, 13.6 ± 3.2 vs. 15.1 ± 3.4, p = 0.0014, respectively). The patients were divided into four groups according to the daily changes in ∆P, namely, the low ∆P group (Day 1 ∆P < 14 cmH2O and Day 3 ∆P < 14 cmH2O), decrement group (Day 1 ∆P ≥ 14 cmH2O and Day 3 ∆P < 14 cmH2O), high ∆P group (Day 1 ∆P ≥ 14 cmH2O and Day 3 ∆P ≥ 14 cmH2O), and increment group (Day 1 ∆P < 14 cmH2O and Day 3 ∆P ≥ 14 cmH2O). The 60-day survival significantly differed among the four groups (log-rank test, p = 0.0271). Compared with the low ΔP group, patients in the decrement group did not have lower 60-day survival (adjusted hazard ratio 0.72; 95% confidence interval [CI] 0.31–1.68; p = 0.4448), while patients in the increment group had significantly lower 60-day survival (adjusted hazard ratio 1.96; 95% CI 1.11–3.44; p = 0.0198).ConclusionsDaily ∆P remains an important predicting factor for survival in patients with ARDS. Serial changes in daily ΔP might be more informative than a single Day 1 ΔP value in predicting survival of patients with ARDS.