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RATIONALE: Whereas non-invasive ventilation (NIV) may prevent reintubation in patients at high-risk of extubation failure in intensive care units (ICUs), this oxygenation strategy has not been specifically assessed in obese patients. OBJECTIVES: We hypothesized that NIV may decrease the risk of reintubation in obese patients compared with high-flow nasal oxygen (HFNO). METHODS: Post-hoc analysis of a multicenter, randomized, controlled trial (not pre-specified) comparing NIV alternating with HFNO versus HFNO alone after extubation, with the aim of assessing NIV effects according to patient body-mass index (BMI). MEASUREMENTS AND MAIN RESULTS: Among 623 patients at high-risk of extubation failure, 206 (33%) were obese (BMI≥30 kg/m2), 204 (33%) were overweight (25≤BMI<30), and 213 (34%) were normal or underweight (BMI<25). Significant heterogeneity of NIV effects on the rate of reintubation was found according to BMI (Pinteraction=0.007). Reintubation rates at day 7 were significantly lower with NIV alternating with HFNO than with HFNO alone in obese or overweight patients: 7% (15/204) vs. 20% (41/206); difference, -13%; [95% CI, -19 to -6]; P=0.0002; whereas it did not significantly differ in normal or underweight patients. In-ICU mortality was significantly lower with NIV than with HFNO alone in obese or overweight patients (2% vs. 9%; difference, -6%; [95% CI, -11 to -2]; P=0.006). CONCLUSIONS: Prophylactic NIV alternating with HFNO immediately after extubation significantly decreased the risk of reintubation and death as compared with HFNO alone in obese or overweight patients at high-risk of extubation failure. By contrast, NIV was not effective in normal or underweight patients.

Rationale South African adolescents carry a high tuberculosis disease burden. It is not known if schools are high-risk settings for Mycobacterium tuberculosis (MTB) transmission. Objectives To detect airborne MTB genomic DNA in classrooms. Methods We studied 72 classrooms occupied by 1,836 students in two South African schools. High-volume air filtration was performed for median 40 minutes (interquartile range 35-54) and assayed by droplet digital PCR (ddPCR) targeting MTB Region of Difference 9 (RD9), with concurrent CO2 concentration measurement. Classroom data were benchmarked against public health clinics. Students who consented to individual TB screening completed a questionnaire and sputum collection (Xpert MTB/RIF Ultra) if symptom-positive. Poisson statistics were used for MTB RD9 copy quantification. Measurements and Main Results ddPCR assays were positive in 13/72 (18.1%) classroom and 4/39 (10.3%) clinic measurements (p=0.276). Median ambient CO2 concentration was 886 ppm (IQR 747-1223) in classrooms vs. 490 ppm (IQR 405-587) in clinics (p<0.001). Average airborne concentration of MTB RD9 was 3.61 copies per 180,000 litres in classrooms vs. 1.74 copies per 180,000 litres in clinics (p=0.280). Across all classrooms, the average risk of an occupant inhaling one MTB RD9 copy was estimated as 0.71% during one standard lesson of 35 minutes. Among 1,836/2,262 (81.2%) students who consented to screening, 21/90 symptomatic students produced a sputum sample (36.2%), of which one was Xpert MTB/RIF Ultra positive. Conclusions Airborne MTB genomic DNA was detected frequently in high school classrooms. Instantaneous risk of classroom exposure was similar to the risk in public health clinics.

Rationale: The regeneration and replacement of lung cells or tissues from induced pluripotent stem cell- or embryonic stem cell-derived cells represent future therapies for life-threatening pulmonary disorders but are limited by technical challenges to produce highly differentiated cells able to maintain lung function. Functional lung tissue-containing airways, alveoli, vasculature, and stroma have never been produced via directed differentiation of embryonic stem cells (ESCs) or induced pluripotent stem cells. We sought to produce all tissue components of the lung from bronchi to alveoli by embryo complementation.Objectives: To determine whether ESCs are capable of generating lung tissue in Nkx2-1-/- mouse embryos with lung agenesis.Methods: Blastocyst complementation was used to produce chimeras from normal mouse ESCs and Nkx2-1-/- embryos, which lack pulmonary tissues. Nkx2-1-/- chimeras were examined using immunostaining, transmission electronic microscopy, fluorescence-activated cell sorter analysis, and single-cell RNA sequencing.Measurements and Main Results: Although peripheral pulmonary and thyroid tissues are entirely lacking in Nkx2-1 gene-deleted embryos, pulmonary and thyroid structures in Nkx2-1-/- chimeras were restored after ESC complementation. Respiratory epithelial cell lineages in restored lungs of Nkx2-1-/- chimeras were derived almost entirely from ESCs, whereas endothelial, immune, and stromal cells were mosaic. ESC-derived cells from multiple respiratory cell lineages were highly differentiated and indistinguishable from endogenous cells based on morphology, ultrastructure, gene expression signatures, and cell surface proteins used to identify cell types by fluorescence-activated cell sorter.Conclusions: Lung and thyroid tissues were generated in vivo from ESCs by blastocyst complementation. Nkx2-1-/- chimeras can be used as "bioreactors" for in vivo differentiation and functional studies of ESC-derived progenitor cells.

Rationale: Alveolar epithelial cell (AEC) injury and dysregulated repair are implicated in the pathogenesis of pulmonary fibrosis. Endoplasmic reticulum (ER) stress in AEC has been observed in idiopathic pulmonary fibrosis (IPF), a disease of aging.Objectives: To investigate a causal role for ER stress in the pathogenesis of pulmonary fibrosis (PF) and therapeutic potential of ER stress inhibition in PF.Methods: The role of ER stress in AEC dysfunction and fibrosis was studied in mice with tamoxifen (Tmx)-inducible deletion of ER chaperone Grp78, a key regulator of ER homeostasis, in alveolar type II (AT2) cells, progenitors of distal lung epithelium, and in IPF lung slice cultures.Measurements and Main Results: Grp78 deletion caused weight loss, mortality, lung inflammation, and spatially heterogeneous fibrosis characterized by fibroblastic foci, hyperplastic AT2 cells, and increased susceptibility of old and male mice, all features of IPF. Fibrosis was more persistent in more severely injured Grp78 knockout (KO) mice. Grp78 KO AT2 cells showed evidence of ER stress, apoptosis, senescence, impaired progenitor capacity, and activation of TGF-β (transforming growth factor-β)/SMAD signaling. Glucose-regulated protein 78 is reduced in AT2 cells from old mice and patients with IPF, and ER stress inhibitor tauroursodeoxycholic acid ameliorates ER stress and fibrosis in Grp78 KO mouse and IPF lung slice cultures.Conclusions: These results support a causal role for ER stress and resulting epithelial dysfunction in PF and suggest ER stress as a potential mechanism linking aging to IPF. Modulation of ER stress and chaperone function may offer a promising therapeutic approach for pulmonary fibrosis.

Rationale: Recent data show that Aspergillus species are prevalent respiratory infections in children with cystic fibrosis (CF). The biological significance of these infections is unknown.Objectives: We aimed to evaluate longitudinal associations between Aspergillus infections and lung disease in young children with CF.Methods: Longitudinal data on 330 children participating in the Australian Respiratory Early Surveillance Team for Cystic Fibrosis surveillance program between 2000 and 2018 who underwent annual chest computed tomography (CT) imaging and BAL were used to determine the association between Aspergillus infections and the progression of structural lung disease. Results were adjusted for the effects of other common infections, associated variables, and repeated visits. Secondary outcomes included inflammatory markers in BAL, respiratory symptoms, and admissions for exacerbations.Measurements and Main Results: Haemophilus influenzae, Staphylococcus aureus, Pseudomonas aeruginosa, and Aspergillus infections were all associated with worse CT scores in the same year (Poverall < 0.05). Only P. aeruginosa and Aspergillus were associated with progression in CT scores in the year after an infection and worse CT scores at the end of the observation period. P. aeruginosa was most significantly associated with development of bronchiectasis (difference, 0.9; 95% confidence interval, 0.3-1.6; P = 0.003) and Aspergillus with trapped air (difference, 3.2; 95% confidence interval, 1.0-5.4; P = 0.004). Aspergillus infections were also associated with markers of neutrophilic inflammation (P < 0.001) and respiratory admissions risk (P = 0.008).Conclusions: Lower respiratory Aspergillus infections are associated with the progression of structural lung disease in young children with CF. This study highlights the need to further evaluate early Aspergillus species infections and the feasibility, risk, and benefit of eradication regimens.