Daily Ards Research Analysis

BACKGROUND: Ventilator-free days (VFDs), a composite endpoint combining survival and mechanical ventilation duration, are increasingly used in acute respiratory distress syndrome (ARDS) trials to capture patient-centred outcomes beyond mortality. However, its interpretation and analysis are challenged by methodological limitations of conventional statistical methods. This study aims to investigate the interpretability and statistical performance of the hierarchical VFDs compared with the conventional versions for ARDS-related trials. METHODS: We applied a hierarchical composite endpoint framework, incorporating mortality and ventilation duration prioritised in sequence, to reconstruct VFDs censored at 28 days. Using the win ratio method, we carried out a post hoc analysis based on data from 10 high-quality randomised controlled trials and conducted simulation studies to assess its statistical performance. RESULTS: Analysis revealed bimodal VFD distributions across trials, with peaks near zero and around 18-20 days. The win ratio method detected all the significant treatment effects that were identified by conventional analyses. Simulation studies suggested that the win ratio demonstrated greater statistical power, particularly when mortality was the primary driver of treatment effect, outperforming traditional methods. CONCLUSIONS: The hierarchical VFDs endpoint, analysed using win statistics, provides a more sensitive and interpretable approach by distinguishing the contribution of mortality and ventilation duration components to the overall treatment effect in ARDS trials compared to the conventional approach.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a severe clinical syndrome with limited therapeutic options. Acute lung injury (ALI) is widely used as an experimental animal model that recapitulates the key pathological features of human ARDS. Parabacteroides goldsteinii, a newly identified Gram-negative probiotic, exhibits anti-inflammatory effects in certain disease models. Gram-negative bacteria release nanoscale structures called outer membrane vesicles (OMVs), which show varying composition across species. The role of P. goldsteinii-derived OMVs (Pg-OMVs) in ALI or ARDS remains to be elucidated. RESULT: In this study, we investigated the therapeutic potential of Pg-OMVs in a bleomycin (BLM)-induced ALI mouse model and explored their effects on pulmonary inflammation and gut microbiota composition. Compared to mice receiving BLM alone, Pg-OMV-treated mice exhibited significantly reduced inflammatory cell infiltration and lower levels of pro-inflammatory cytokines. Notably, Pg-OMV treatment significantly altered the gut microbiota composition, characterized by an increased abundance of Akkermansia muciniphila and a decreased abundance of Clostridia_bacterium. Fecal microbiota transplantation (FMT) experiments confirmed that the protective effects of Pg-OMVs were mediated via gut-lung axis. Further analysis revealed elevated cholic acid (CA) levels in the peripheral blood and bronchoalveolar lavage fluid following Pg-OMV treatment. CA was shown to suppress BLM-induced macrophage pyroptosis in the lung. Pharmacological inhibition of CA reversed the protective effects of Pg-OMVs, further confirming its pivotal role. CONCLUSIONS: In summary, Pg-OMVs increased the abundance of Akkermansia muciniphila while decreasing the abundance of Clostridia_bacterium in the gut, elevated systemic CA levels, and suppressed macrophage pyroptosis via inhibition of the NF-κB pathway, thereby attenuating pulmonary inflammation and ultimately alleviating ALI. These findings highlight a novel therapeutic strategy for the treatment of ALI or ARDS by targeting the gut-lung axis.

BACKGROUND: Optimal oxygen levels in pregnant mothers undergoing mechanical ventilation are not known. This study examined the effects of four maternal oxygenation ranges on fetal hemodynamics and oxygenation in late-preterm lambs. METHODS: Thirty-seven ewes were intubated, sedated, and surgically catheterized, while exposed to varying FiO RESULTS: Fetal carotid oxygen content was comparable between hyperoxia and normal oxygenation with stable cerebral oxygen delivery (DO₂: 2.0 ± 1.2 vs. 2.1 ± 1.7 mL/kg/min). In contrast, PaO₂ 55-80 mmHg and <55 mmHg were associated with significantly reduced fetal oxygen content (5.2 ± 3.7 and 4.0 ± 3.1 mL/dL, respectively) versus >150 mmHg, though only <55 mmHg differed significantly from 81-150 mmHg. Cerebral DO₂ trended lower in hypoxemic groups (1.6 ± 1.6 and 1.1 ± 1.1 mL/kg/min) but did not reach significance. CONCLUSIONS: Maternal hyperoxia exposure is buffered by the fetoplacental circulation minimizing fetal cerebral risk. When maternal PaO₂ < 80 mmHg, particularly < 55 mmHg, fetal carotid oxygen content declines, potentially compromising cerebral oxygen delivery. IMPACT: Pregnant women are highly susceptible to severe respiratory illness and ARDS, yet guidance on optimal maternal oxygen targets is limited. We investigated how varying maternal PaO₂ levels affect fetoplacental circulation and in-utero oxygenation. Using a large mammalian model of acute maternal hypoxia, we assessed whether maternal ARDSnet oxygenation targets (PaO₂ 55-80 mmHg, SpO₂ 88-95%) can be safely applied in pregnancy. Fetal carotid oxygen content decreased at maternal ARDSnet targets and when below PaO₂ 55 mmHg, with a non-significant trend toward reduced fetal cerebral oxygen delivery. Application of a maternal ARDSnet strategy may lead to suboptimal fetal oxygenation.