Pulmonary fibrosis (PF) is a form of chronic lung disease characterized by pathologic epithelial remodeling and accumulation of extracellular matrix (ECM). To comprehensively define the cell types, mechanisms, and mediators driving fibrotic remodeling in lungs with PF, we performed single-cell RNA sequencing of single-cell suspensions from 10 nonfibrotic control and 20 PF lungs. Analysis of 114,396 cells identified 31 distinct cell subsets/states. We report that a remarkable shift in epithelial cell phenotypes occurs in the peripheral lung in PF and identify several previously unrecognized epithelial cell phenotypes, including a KRT5−/KRT17+ pathologic, ECM-producing epithelial cell population that was highly enriched in PF lungs. Multiple fibroblast subtypes were observed to contribute to ECM expansion in a spatially discrete manner. Together, these data provide high-resolution insights into the complexity and plasticity of the distal lung epithelium in human disease and indicate a diversity of epithelial and mesenchymal cells contribute to pathologic lung fibrosis.

Pseudomonas aeruginosa uses a type III secretion system to promote development of severe disease, particularly in patients with impaired immune defenses. While the biochemical and enzymatic functions of ExoU, ExoS, and ExoT, three effector proteins secreted by this system, are well defined, the relative roles of each protein in the pathogenesis of acute infections is not clearly understood. Since ExoU and ExoS are usually not secreted by the same strain, it has been difficult to directly compare the effects of these proteins during infection. In the work described here, several isogenic mutants of a bacterial strain that naturally secretes ExoU, ExoS, and ExoT were generated to carefully evaluate the relative contribution of each effector protein to pathogenesis in a mouse model of acute pneumonia. Measurements of mortality, bacterial persistence in the lung, and dissemination indicated that secretion of ExoU had the greatest impact on virulence while secretion of ExoS had an intermediate effect and ExoT had a minor effect. It is of note that these results conclusively show for the first time that ExoS is a virulence factor. Infection with isogenic mutants secreting wild-type ExoS, ExoS defective in GTPase-activating protein (GAP) activity, or ExoS defective in ADP-ribosyltransferase activity demonstrated that the virulence of ExoS was largely dependent on its ADP-ribosyltransferase activity. The GAP activity of this protein had only a minor effect in vivo. The relative virulence associated with each of these type III effector proteins may have important prognostic implications for patients infected with P. aeruginosa.Pseudomonas aeruginosa is a gram-negative pathogen that causes a variety of serious infections predominantly in immunocompromised patients. To promote severe illness, P. aeruginosa uses a type III secretion system to inject toxic effector proteins into the cytoplasm of eukaryotic cells. To date, four effector proteins have been described in P. aeruginosa: ExoU, ExoS, ExoT, and ExoY (9,18,[59][60][61][62]. ExoU is a potent cytotoxin with phospholipase A 2 activity (43, 49). ExoS and ExoT are bifunctional enzymes that have 75% amino acid identity (60) and encode both GTPase-activating protein (GAP) and ADP-ribosyltransferase (ADPRT) activities (15,(24)(25)(26)33). ExoY is an adenylate cyclase (62).The overall importance of type III secretion as a virulence mechanism of P. aeruginosa has been well established. Early studies showed that ExsA, a transcriptional activator of the type III secretion system (11, 61), is essential for full virulence in animal models of acute pneumonia (28,34,58). More recently, these conclusions have been validated by the use of mutants with specific disruptions in genes encoding portions of the type III secretion apparatus (54). In addition, type III secretion has been associated with more severe clinical disease in human patients (16,47).Several studies have analyzed mutants with deletions in individual effector-encoding genes to begin to address the roles of each effector...

The RALE score can be used to assess both the extent of pulmonary oedema and the severity of ARDS, by utilising information that is already obtained routinely, safely and inexpensively in every patient with ARDS. This novel non-invasive measure should be useful for assessing ARDS severity and monitoring response to therapy.

Objective Atrial fibrillation (AF) has been associated with increased mortality in critically-ill patients. We sought to determine whether AF in the intensive care unit (ICU) is an independent risk factor for death. A secondary objective was to determine if patients with new-onset AF have different risk factors or outcomes compared to patients with a previous history of AF. Design Prospective observational cohort study. Setting Medical and general surgical ICUs in a tertiary academic medical center. Patients 1,770 critically-ill patients requiring at least 2 days in the ICU. Interventions None. Measurements Demographics, medical history, development of AF, fluid balance, echocardiographic findings, medication administration, and hospital mortality were collected during the first four days of ICU admission. Main Results AF occurred in 236 (13%) patients (Any AF). Of these, 123 patients (7%) had no prior AF (New-onset AF) while the remaining 113 (6%) had Recurrent AF. Any AF was associated with male gender, Caucasian race, increased age, cardiac disease, organ failures, and disease severity. Patients with Any AF had increased mortality compared to those without AF (31% vs. 17%, p <0.001) and Any AF was independently associated with death (OR 1.62, 95% CI 1.14-2.29, p=0.007) in multivariable analysis controlling for severity of illness and other confounders. The association of AF with death was magnified in patients without sepsis (OR 2.92, 95% CI 1.52-5.60, p=0.001). Treatment for AF had no effect on hospital mortality. New-onset AF and Recurrent AF were each associated with increased mortality. New-onset AF, but not Recurrent AF, was associated with increased diastolic dysfunction and vasopressor use and a greater cumulative positive fluid balance. Conclusions AF in critical illness, whether new-onset or recurrent, is independently associated with increased hospital mortality, especially in patients without sepsis.

BACKGROUND:Oxygen saturation as measured by pulse oximetry/F io 2 (SF) ratio is highly correlated with the Pa o 2 /F io 2 (PF) ratio in patients with ARDS. However, it remains uncertain whether SF ratio can be substituted for PF ratio for diagnosis of ARDS and whether SF ratio might identify patients who are systemically diff erent from patients diagnosed by PF ratio.