Distal Airspaces Research Articles

Standardization of methods for sampling the distal airspace in mechanically ventilated patients using heat moisture exchange filter fluid.

Noninvasive sampling of the distal airspace in patients with acute respiratory distress syndrome (ARDS) has long eluded clinical and translational researchers. We recently reported that fluid collected from heat moisture exchange (HME) filters closely mirrors fluid directly aspirated from the distal airspace. In the current study, we sought to determine fluid yield from different HME types, optimal HME circuit dwell time, and reliability of HME fluid in reflecting the distal airspace. We studied fluid yield from four different filter types by loading increasing volumes of saline and measuring volumes of fluid recovered. We collected filters after 1, 2, and 4 h of dwell time for measurement of fluid volume and total protein from 13 subjects. After identifying 4 h as the optimal dwell time, we measured total protein and IgM in HME fluid from 42 subjects with ARDS and nine with hydrostatic pulmonary edema (HYDRO). We found that the fluid yield varies greatly by filter type. With timed sample collection, fluid recovery increased with increasing circuit dwell time with a median volume of 2.0 mL [interquartile range (IQR) 1.2-2.7] after 4 h. Total protein was higher in the 42 subjects with ARDS compared with nine with HYDRO [median 708 µg/mL (IQR 244-2017) vs. 364 µg/mL (IQR 136-578), P = 0.047], confirming that total protein concentration in HME is higher in ARDS compared with hydrostatic edema. These studies establish a standardized HME fluid collection protocol and confirm that HME fluid analysis is a novel noninvasive tool for the study of the distal airspace in ARDS.

Airspace Dimension Assessment (AiDA) by inhaled nanoparticles: benchmarking with hyperpolarised 129Xe diffusion-weighted lung MRI

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. Airspace Dimension Assessment with inhaled nanoparticles (AiDA) is a new method developed for in vivo measurement of distal airspace dimensions. The aim of this study was to benchmark the AiDA method against quantitative measurements of distal airspaces from hyperpolarised 129Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI). AiDA and 129Xe DW-MRI measurements were performed in 23 healthy volunteers who spanned an age range of 23–70 years. The relationship between the 129Xe DW-MRI and AiDA metrics was tested using Spearman’s rank correlation coefficient. Significant correlations were observed between AiDA distal airspace radius (rAiDA) and mean 129Xe apparent diffusion coefficient (ADC) (p < 0.005), distributed diffusivity coefficient (DDC) (p < 0.001) and distal airspace dimension (LmD) (p < 0.001). A mean bias of − 1.2 µm towards rAiDA was observed between 129Xe LmD and rAiDA, indicating that rAiDA is a measure of distal airspace dimension. The AiDA R0 intercept correlated with MRI 129Xe α (p = 0.02), a marker of distal airspace heterogeneity. This study demonstrates that AiDA has potential to characterize the distal airspace microstructures and may serve as an alternative method for clinical examination of the lungs.

Regulatory mechanisms of neutrophil migration from the circulation to the airspace.

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

Genetic variants of small airways and interstitial pulmonary disease in children

Genetic variants of small airways and interstitial pulmonary disease have not been comprehensively studied. This cluster of respiratory disorders usually manifests from early infancy (‘lung disease in utero’). In this study, 24 variants linked to these entities are described. The variants involved two genes associated with surfactant metabolism dysfunction (ABCA3 and CSF2RB), two with pulmonary fibrosis (MUC5B and SFTP), one with bronchiectasis (SCNN1B), and one with alpha-1-antitrypsin deficiency (SERPINA1). A nonsense variant, MUC5B:c.16861G > T, p.Glu5621*, was found in homozygous state in two siblings with severe respiratory disease from birth. One of the siblings also had heterozygous SFTPA1:c.675C > G, p.Asn225Lys, which resulted in a more severe respiratory disease. The sibling with only the homozygous MUC5B variant had lung biopsy, which showed alveolar simplification, interstitial fibrosis, intra-alveolar lipid-laden macrophages, and foci of foreign body giant cell reaction in distal airspaces. Two missense variants, MUC5B:c.14936 T > C, p.Ile4979Thr (rs201287218) and MUC5B:c.16738G > A, p.Gly5580Arg (rs776709402), were also found in compound heterozygous state in two siblings with severe respiratory disease from birth. Overall, the results emphasize the need for genetic studies for patients with complex respiratory problems. Identifying pathogenic variants, such as those presented here, assists in effective family counseling aimed at genetic prevention. In addition, results of genetic studies improve the clinical care and provide opportunities for participating in clinical trials, such as those involving molecularly-targeted therapies.

Sodium-coupled neutral amino acid transporter SNAT2 counteracts cardiogenic pulmonary edema by driving alveolar fluid clearance.

The constant transport of ions across the alveolar epithelial barrier regulates alveolar fluid homeostasis. Dysregulation or inhibition of Na+ transport causes fluid accumulation in the distal airspaces resulting in impaired gas exchange and respiratory failure. Previous studies have primarily focused on the critical role of amiloride-sensitive epithelial sodium channel (ENaC) in alveolar fluid clearance (AFC), yet activation of ENaC failed to attenuate pulmonary edema in clinical trials. Since 40% of AFC is amiloride-insensitive, Na+ channels/transporters other than ENaC such as Na+-coupled neutral amino acid transporters (SNATs) may provide novel therapeutic targets. Here, we identified a key role for SNAT2 (SLC38A2) in AFC and pulmonary edema resolution. In isolated perfused mouse and rat lungs, pharmacological inhibition of SNATs by HgCl2 and α-methylaminoisobutyric acid (MeAIB) impaired AFC. Quantitative RT-PCR identified SNAT2 as the highest expressed System A transporter in pulmonary epithelial cells. Pharmacological inhibition or siRNA-mediated knockdown of SNAT2 reduced transport of l-alanine across pulmonary epithelial cells. Homozygous Slc38a2-/- mice were subviable and died shortly after birth with severe cyanosis. Isolated lungs of Slc38a2+/- mice developed higher wet-to-dry weight ratios (W/D) as compared to wild type (WT) in response to hydrostatic stress. Similarly, W/D ratios were increased in Slc38a2+/- mice as compared to controls in an acid-induced lung injury model. Our results identify SNAT2 as a functional transporter for Na+ and neutral amino acids in pulmonary epithelial cells with a relevant role in AFC and the resolution of lung edema. Activation of SNAT2 may provide a new therapeutic strategy to counteract and/or reverse pulmonary edema.

Repetitive Ozone Exposures and Evaluation of Pulmonary Inflammation and Remodeling in Diabetic Mouse Strains.

Background:Epidemiological studies support the hypothesis that diabetes alters pulmonary responses to air pollutants like ozone (). The mechanism(s) underlying these associations and potential links among diabetes, , and lung inflammation and remodeling are currently unknown.Objectives:The goal was to determine whether pulmonary responses to repetitive ozone exposures are exacerbated in murine strains that are hyperglycemic and insulin resistant.Methods:Normoglycemic and insulin-sensitive C57BL/6J mice; hyperglycemic, but mildly insulin-resistant, KK mice; and hyperglycemic and markedly insulin-resistant KKAy mice were used for ozone exposure studies. All animals were exposed to filtered air (FA) or repetitive ozone ( , 4 h/d, for 13 consecutive weekdays). Tissue analysis was performed 24 h following the final exposure. This analysis included bronchoalveolar lavage (BAL) for cell and fluid analysis, and tissue for pathology, immunohistology, mRNA, and hydroxyproline.Results:Following repetitive exposure, higher bronchoalveolar lavage fluid inflammatory cells were observed in all mice (), with a notable influx of neutrophils and eosinophils in KK and KKAy mice. Although the lungs of -exposed C57BL/6J and KK mice had minimal centriacinar histological changes without fibrosis, the lungs of -exposed KKAy mice contained marked epithelial hyperplasia in proximal alveolar ducts and adjacent alveoli with associated centriacinar fibrosis. Fibrosis in -exposed KKAy lungs was confirmed with immunohistochemistry, tissue hydroxyproline content, and tissue mRNA expression of fibrosis-associated genes (Ccl11, Il13, and Mmp12). Immunofluorescence staining and confocal microscopy revealed alterations in the structure and composition of the airway and alveolar epithelium in regions of fibrosis.Discussion:Our results demonstrate that in diabetic animal strains repetitive ambient ozone exposure led to early and exaggerated pulmonary inflammation and remodeling. Changes in distal and interstitial airspaces and the activation of Th2 inflammatory and profibrotic pathways in experimental animals provide a preliminary, mechanistic framework to support the emerging epidemiological associations among air pollution, diabetes, and lung disease. https://doi.org/10.1289/EHP7255

The Nature of Recruitment and De-Recruitment and Its Implications for Management of ARDS.

Recruitment maneuvers in ARDS are used to improve oxygenation and lung mechanics by applying high airway pressures to reopen collapsed or obstructed peripheral airways and alveoli. In the early 1990s, recruitment maneuvers became a central feature of a variant form of lung-protective ventilation known as open-lung ventilation. This strategy is based on the belief that repetitive opening and closing of distal airspaces induces shear injury and therefore contributes both to ventilator-induced lung injury and ARDS-associated mortality. However, the largest multi-center randomized controlled trial of open-lung ventilation in moderate to severe ARDS reported that recruitment maneuver plateau pressures of 50-60 cm H2O were associated with significantly higher mortality compared to traditional lung-protective ventilation. Despite being based on well conducted preclinical and clinical recruitment maneuver studies, the higher mortality associated with the open-lung ventilation strategy requires re-examining the assumptions and conclusions drawn from those previous studies. This narrative review examines the evidence used to design recruitment maneuver strategies. We also review the radiologic, rheologic, and histopathologic evidence regarding the nature of lung injury and the phenomena of recruitment and de-recruitment as it informs our perceptions of recruitment potential in ARDS. Major lung-protective ventilation clinical trial data and other clinical data are also examined to assess the practical necessity of recruitment maneuvers in ARDS and whether a subset of cases might benefit from pursuing recruitment maneuver therapy. Finally, a less a radical approach to recruitment maneuvers is offered that might achieve the goals of recruitment maneuvers with less risk of harm.

CCR2 Mediates Chronic LPS-Induced Pulmonary Inflammation and Hypoalveolarization in a Murine Model of Bronchopulmonary Dysplasia.

The histopathology of bronchopulmonary dysplasia (BPD) includes hypoalveolarization and interstitial thickening due to abnormal myofibroblast accumulation. Chorioamnionitis and sepsis are major risk factors for BPD development. The cellular mechanisms leading to these lung structural abnormalities are poorly understood. We used an animal model with repeated lipopolysaccharide (LPS) administration into the airways of immature mice to simulate prolonged airway exposure to gram-negative bacteria, focusing on the role of C-C chemokine receptor type 2-positive (CCR2+) exudative macrophages (ExMf). Repetitive LPS exposure of immature mice induced persistent hypoalveolarization observed at 4 and 18 days after the last LPS administration. LPS upregulated the expression of lung pro-inflammatory cytokines (TNF-α, IL-17a, IL-6, IL-1β) and chemokines (CCL2, CCL7, CXCL1, and CXCL2), while the expression of genes involved in lung alveolar and mesenchymal cell development (PDGFR-α, FGF7, FGF10, and SPRY1) was decreased. LPS induced recruitment of ExMf, including CCR2+ ExMf, as well as other myeloid cells like DCs and neutrophils. Lungs of LPS-exposed CCR2−/− mice showed preserved alveolar structure and normal patterns of α-actin and PDGFRα expression at the tips of the secondary alveolar crests. Compared to wild type mice, a significantly lower number of ExMf, including TNF-α+ ExMf were recruited to the lungs of CCR2−/− mice following repetitive LPS exposure. Further, pharmacological inhibition of TLR4 with TAK-242 also blocked the effect of LPS on alveolarization, α-SMA and PDGFRα expression. TNF-α and IL-17a induced α-smooth muscle actin expression in the distal airspaces of E16 fetal mouse lung explants. In human preterm lung mesenchymal stromal cells, TNF-α reduced mRNA and protein expression of PDGFR-α and decreased mRNA expression of WNT2, FOXF2, and SPRY1. Collectively, our findings demonstrate that in immature mice repetitive LPS exposure, through TLR4 signaling increases lung inflammation and impairs lung alveolar growth in a CCR2-dependent manner.

EVEROLIMUS-INDUCED PULMONARY ALVEOLAR PROTEINOSIS

SESSION TITLE: Medical Student/Resident Diffuse Lung Disease SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Pulmonary alveolar proteinosis (PAP) is a rare respiratory disease characterized by an excessive accumulation of lipoproteinaceous surfactant material in the distal air spaces. This is mostly the result of inadequate clearance of surfactant by alveolar macrophages. Autoimmune etiologies make up ∼90% of adult cases, however there are congenital and secondary etiologies as well (1). We present a unique case of drug induced PAP caused by everolimus use. CASE PRESENTATION: A 44 year old female, history of renal cell carcinoma (RCC) with lung metastasis, presents with 1 week of worsening shortness of breath following a round of chemotherapy and immunotherapy (nivolumab, ipilimumab, everolimus). Associated fever, vomiting and productive cough were also reported. On the scene, EMS reported an oxygen saturation of 81% on room air. In the ED, the patient was placed on BiPAP and started on scheduled breathing treatments, IV fluids and broad spectrum antibiotics. Chest exam revealed diffuse rales. Initial labs showed lactic acidosis without an elevated WBC. ABG showed PaO2 of 103 mmHg on 60% BiPAP. CT chest showed new onset loculated right-sided pleural effusion and extensive left-sided ground glassing, concerning for a crazy pavement appearance. Right-sided thoracentesis was attempted and failed as the fluid could not be aspirated. On Day 2, she was intubated due to worsening respiratory status. Bronchoalveolar lavage (BAL) sample was obtained. BAL cytology was negative for malignant cells or active inflammation, but showed an abundance of amorphous, eosinophilic, periodic acid-Schiff (PAS)-positive material. Bacterial, fungal and viral cultures and respiratory viral PCR were negative. She continued to decline and on day 8, in light of her terminal illness, her family decided to transition to hospice care. Compassionate extubation was done on day 9 and the patient expired shortly after. DISCUSSION: Everolimus is a mammalian target of rapamycin (mTOR) inhibitor, often used in breast, pancreatic and renal carcinoma. Though there have been reports of PAP complicating sirolimus use, no such reports exist for everolimus (2). PAS stains of BAL or lung biopsy samples confirm the diagnosis of PAP. But without a sample, high index of clinical suspicion is needed to differentiate PAP from other pulmonary processes and intervene early. If diagnosed early, stopping the offending agent may be all that is needed. In those with moderate to severe symptoms, whole lung lavage (WLL) is the most accepted intervention. 30-50% of cases only require one lavage, others will require repeat at 6-12-month intervals. Cases refractory to WLL may require trials of GM-CSF inhaled therapy and rituximab but their efficacy has only been shown in autoimmune PAP (3). CONCLUSIONS: We present a case of everolimus induced pulmonary alveolar proteinosis in a patient with metastatic RCC. Diagnosis was confirmed with a PAS-positive BAL sample. Reference #1: Trapnell BC, Whitsett JA, Nakata K. Pulmonary alveolar proteinosis. N Engl J Med 2003; 349:2527. Reference #2: Kadikoy H, Paolini M, Achkar K, et al. Pulmonary alveolar proteinosis in a kidney transplant: a rare complication of sirolimus. Nephrol Dial Transplant 2010; 25: 2795–2798 Reference #3: Kumar A, Abdelmalak B, Inoue Y, Culver DA. Pulmonary alveolar proteinosis in adults: pathophysiology and clinical approach. Lancet Respir Med 2018; 6:554. DISCLOSURES: No relevant relationships by Gnananandh Jayaraman, source=Web Response No relevant relationships by Ramesh Babu Kesavan, source=Web Response No relevant relationships by Robert Liu, source=Web Response No relevant relationships by Sivatej Sarva, source=Web Response

EFFECT OF GENDER ON THE TREATMENT RESPONSES TO RAPAMYCIN ON THE PROGRESSION OF EMPHYSEMA IN CIGARETTE SMOKE-EXPOSED MICE

SESSION TITLE: Obstructive Lung Disease Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Emphysema is characterized by the permanent enlargement of distal airspaces. Current therapies focus on symptom relief as little can halt disease progression. Given its role in cell aging/damage, the mTOR pathway has been studied with respect to emphysema. While inhibition of this pathway with rapamycin has been shown to delay progression of cigarette-smoke (CS) induced emphysema, effects of gender have not been examined. We aim to characterize the effects of rapamycin on the progression of CS induced lung injury in male and female mice. METHODS: A prospective study of 151 mice (C57B/6 strain) was conducted. The mice were separated into two cohorts: CS exposure vs. no CS exposure. The CS exposed group was stratified based on gender and treatment with rapamycin (CS-D) or a vehicle (CS-V) whereas the no CS exposure group was stratified by gender alone. Mice were sacrificed at 0, 3 and 5 months to obtain alveolar histologic data (chord length [Lm]) and pre-mortem physiologic data by Scireq Flexivent (total lung capacity [TLC], static compliance [Cst], dynamic compliance [Cdy], and Pressure-Volume [PV] loops). Statistical analysis was performed by Mann-Whitney t-test and Kruskall-Wallis test using PRISM GraphPad software with a p < 0.05 considered significant. RESULTS: Male CS-V mice had a higher lung compliance at 3 months compared to male CS-D mice as seen on the PV loops. Ventilator data showed male CS-V mice to have a higher average TLC (1.56mL vs 1.43mL; p= 0.002) and Cst (0.11 mL/cmH2O vs 0.09 mL/cmH2O; p = 0.002) at 3 months compared to male CS-D mice. This difference in ventilator parameters did not persist at 5 months and were not different between CS-V and CS-D mice (p > 0.05). On histology, CS-V mice had longer Lm than non-CS exposed mice over the 5 month study period with the largest difference at 5 months (75.12 um vs 66.28 um; p= 0.003). Male CS-V mice had longer Lm than CS-D mice at 3 months (69.59 um vs 65.47 um; p= 0.016), but not at 5 months. No significant differences in Lm were seen between CS-V and CS-D mice at 3 and 5 months in the female group. CONCLUSIONS: Protection against CS induced emphysema by treatment with rapamycin is highly gender dependent. Males benefit significantly with rapamycin treatment while females do not. This therapeutic effect is not durable over long/chronic CS exposure. CLINICAL IMPLICATIONS: Rapamycin may be a viable option for temporarily delaying the progression of CS-induced emphysema, though further investigation into the mechanisms by which gender influences the progression of CS-induced emphysema related to the biology of mTOR and aging are needed. DISCLOSURES: No relevant relationships by Marie Burdick, source=Web Response No relevant relationships by Kranthikiran Earasi, source=Web Response No relevant relationships by Mu He, source=Web Response No relevant relationships by Jamie MacLeod, source=Web Response No relevant relationships by Lukasz Myc, source=Web Response No relevant relationships by Zaid Obaida, source=Web Response No relevant relationships Added 05/30/2020 by Yun Shim, source=Web Response, value=Intellectual property rights Removed 06/01/2020 by Yun Shim, source=Web Response No relevant relationships Added 05/30/2020 by Yun Shim, source=Web Response, value=Salary Removed 06/01/2020 by Yun Shim, source=Web Response No relevant relationships by Chunzi Song, source=Web Response No relevant relationships by Zhimin Zhang, source=Web Response

Hidden Microatelectases Increase Vulnerability to Ventilation-Induced Lung Injury.

Mechanical ventilation of lungs suffering from microatelectases may trigger the development of acute lung injury (ALI). Direct lung injury by bleomycin results in surfactant dysfunction and microatelectases at day 1 while tissue elastance and oxygenation remain normal. Computational simulations of alveolar micromechanics 1-day post-bleomycin predict persisting microatelectases throughout the respiratory cycle and increased alveolar strain during low positive end-expiratory pressure (PEEP) ventilation. As such, we hypothesize that mechanical ventilation in presence of microatelectases, which occur at low but not at higher PEEP, aggravates and unmasks ALI in the bleomycin injury model. Rats were randomized and challenged with bleomycin (B) or not (H = healthy). One day after bleomycin instillation the animals were ventilated for 3 h with PEEP 1 (PEEP1) or 5 cmH2O (PEEP5) and a tidal volume of 10 ml/kg bodyweight. Tissue elastance was repetitively measured after a recruitment maneuver to investigate the degree of distal airspace instability. The right lung was subjected to bronchoalveolar lavage (BAL), the left lung was fixed for design-based stereology at light- and electron microscopic level. Prior to mechanical ventilation, lung tissue elastance did not differ. During mechanical ventilation tissue elastance increased in bleomycin-injured lungs ventilated with PEEP = 1 cmH2O but remained stable in all other groups. Measurements at the conclusion of ventilation showed the largest time-dependent increase in tissue elastance after recruitment in B/PEEP1, indicating increased instability of distal airspaces. These lung mechanical findings correlated with BAL measurements including elevated BAL neutrophilic granulocytes as well as BAL protein and albumin in B/PEEP1. Moreover, the increased septal wall thickness and volume of peri-bronchiolar-vascular connective tissue in B/PEEP1 suggested aggravation of interstitial edema by ventilation in presence of microatelectases. At the electron microscopic level, the largest surface area of injured alveolar epithelial was observed in bleomycin-challenged lungs after PEEP = 1 cmH2O ventilation. After bleomycin treatment cellular markers of endoplasmic reticulum stress (p-Perk and p-EIF-2α) were positive within the septal wall and ventilation with PEEP = 1 cmH2O ventilation increased the surface area stained positively for p-EIF-2α. In conclusion, hidden microatelectases are linked with an increased pulmonary vulnerability for mechanical ventilation characterized by an aggravation of epithelial injury.

Perspectives on Cardiopulmonary Critical Care for Patients With COVID-19: From Members of the American Heart Association Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation.

The coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), marks a global event that will permanently reshape implementation of intensive care medicine. As of June 4, 2020, there are 6,606,455 reported cases of COVID-19 including 388,556 fatalities spanning 215 countries and territories, although epidemiological data remain incomplete. Early autopsy reports emphasize proximal airway and distal airspace involvement, including alveolar epithelial inflammation and capillary thickening.

The ex vivo perfused human lung is resistant to injury by high-dose S. pneumoniae bacteremia.

Few patients with bacteremia from a nonpulmonary source develop acute respiratory distress syndrome (ARDS). However, the mechanisms that protect the lung from injury in bacteremia have not been identified. We simulated bacteremia by adding Streptococcus pneumoniae to the perfusate of the ex vivo perfused human lung model. In contrast to a pneumonia model in which bacteria were instilled into the distal air spaces of one lobe, injection of high doses of S. pneumoniae into the perfusate was not associated with alveolar epithelial injury as demonstrated by low protein permeability of the alveolar epithelium, intact alveolar fluid clearance, and the absence of alveolar edema. Unexpectedly, the ex vivo human lung rapidly cleared large quantities of S. pneumoniae even though the perfusate had very few intravascular phagocytes and lacked immunoglobulins or complement. The bacteria were cleared in part by the small number of neutrophils in the perfusate, alveolar macrophages in the airspaces, and probably by interstitial pathways. Together, these findings identify one mechanism by which the lung and the alveolar epithelium are protected from injury in bacteremia.

A PATIENT WITH ACUTE CHRONIC RESPIRATORY FAILURE AND BILATERAL PULMONARY INFILTRATES

SESSION TITLE: Tuesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Differential diagnosis of bilateral diffuse pulmonary infiltrate is broad and includes both infectious and noninfectious etiologies, such as vasculitis, allergic bronchopulmonary aspergillosis, interstitial lung disease and autoimmune disease. CASE PRESENTATION: A 45 year old male with a presumptive diagnosis of hypersensitivity pneumonitis presented with worsening shortness of breath and was admitted to the hospital. He received steroids and 5 day course of levofloxacin, but remained hypoxic requiring up to 10 liter oxygen. Due to his worsening respiratory status, he was transferred to the intensive care unit (ICU). On admission to the ICU, chest radiograph showed progressing patchy airspace disease diffusely throughout both lungs. CT chest revealed nonspecific diffuse and patchy ground glass opacity with interlobular septal thickening and superimposed consolidative opacities throughout both lungs, in a crazy paving pattern. He continued treatment with intravenous steroids but had minimal improvement in his respiratory status. He underwent bronchoscopy with bronchoalveolar lavage (BAL) on day 5, which showed scant thick secretions with occasional streak of blood. Based on his imaging results and bronchoscopy appearance, the top differential for his acute on chronic respiratory failure was pulmonary alveolar proteinosis (PAP). He subsequently underwent bilateral total lung lavage during which large amount of debris was cleared from both lungs, and periodic acid-Schiff (PAS) stain showed clumps of granular acellular material suggestive of intra-alveolar proteinosis. Culture from BAL also showed polymicrobial growth with streptococcus anginosus and rothia dentocariosa, and he completed 7 day course of antibiotic therapy, initially with cefepime and then transitioned to ceftriaxone. By the time of discharge, his oxygen requirement was 3L/min via nasal cannula and he was started on GM CSF. DISCUSSION: PAP is a rare disease characterized by accumulation of PAS-positive lipoproteinaceous material in the distal air spaces due to impaired surfactant clearance. Auto-immune PAP is the most common etiology with estimated prevalence of 4 to 40 cases per million. CT scan is the major tool in diagnosis of PAP with patterns of ground-glass opacities, septal reticulations and parenchymal consolidation being highly suggestive of the disease. Diagnosis requires BAL which reveals milky fluid and positive PAS-staining granules. The mainstay of treatment remains symptomatic total lung lavage with GM CSF as an adjunct. CONCLUSIONS: In patients with acute on chronic respiratory failure, the appearance of diffuse ground-glass opacities, septal reticulations and parenchymal consolidation should raise concern for PAP. Proper diagnostic workup includes BAL with PAS staining. Reference #1: Singh I, Kaner R. A Woman with Asthma and Ground-Glass Opacities. Ann Am Thorac Soc. 2017;14(1):140-144. Reference #2: Rosen SH, Castleman B, Liebow AA. Pulmonary alveolar proteinosis. N Engl J Med. 1958;258(23):1123-42. Reference #3: Borie R, Danel C, Debray MP, et al. Pulmonary alveolar proteinosis. Eur Respir Rev. 2011;20(120):98-107. DISCLOSURES: No relevant relationships by Alice Gallo De Moraes, source=Web Response No relevant relationships by Melissa Myers, source=Web Response No relevant relationships by Zhenmei Zhang, source=Web Response

Surfactant dysfunction and alveolar collapse are linked with fibrotic septal wall remodeling in the TGF-β1-induced mouse model of pulmonary fibrosis

In human idiopathic pulmonary fibrosis (IPF), collapse of distal airspaces occurs in areas of the lung not (yet) remodeled. Mice lungs overexpressing transforming growth factor-β1 (TGF-β1) recapitulate this abnormality: surfactant dysfunction results in alveolar collapse preceding fibrosis and loss of alveolar epithelial type II (AE2) cells' apical membrane surface area. Here we examined whether surfactant dysfunction-related alveolar collapse due to TGF-β1 overexpression is linked to septal wall remodeling and AE2 cell abnormalities. Three and 6 days after gene transfer of TGF-β1, mice received either intratracheal surfactant (Surf-groups: Curosurf®, 100 mg/kg bodyweight) or 0.9% NaCl (Saline-groups). On days 7 (D7) and 14 (D14), lung mechanics were assessed followed by design-based stereology at light and electron microscopic level to quantify structures. Compared with Saline, Surf showed significantly improved tissue elastance, increased numbers of open alveoli, as well as reduced alveolar size heterogeneity on D7. Deterioration in lung mechanics was highly correlated to the loss of open alveoli. On D14, lung mechanics, number of open alveoli, and alveolar size heterogeneity remained significantly improved in the Surf-group. Volumes of extracellular matrix and collagen fibrils in septal walls were significantly reduced, whereas the apical membrane surface area of AE2 cells was increased in Surf compared with Saline. In remodeled tissue with collapsed alveoli, three-dimensional reconstruction of AE2 cells based on scanning electron microscopy array tomography revealed that AE2 cells were trapped without contact to airspaces in the TGF-β1 mouse model. Similar observations were made in human IPF. Based on correlation analyses, the number of open alveoli and of alveolar size heterogeneity were highly linked with the loss of apical membrane surface area of AE2 cells and deposition of collagen fibrils in septal walls on D14. In conclusion, surfactant replacement therapy stabilizes alveoli and prevents extracellular matrix deposition in septal walls in the TGF-β1 model.

In Vivo Morphometry of Distal Airspaces with Nanoparticles As a Proposed Biomarker for Emphysema

Background: Airspace dimension assessment with nanoparticles (AiDA) is a novel method to measure distal airway morphology non-invasively. In this study, AiDA-derived airspace radii were measured in an unselected, cross-sectional study population. Persons with emphysema detected by computed tomography (CT) were compared to non-emphysematous subjects. Method: Nanoparticle inhalation tests, from which distal airspace radius (rAiDA) were calculated, were conducted on 618 individuals aged 50-64 years participating in the population-based Swedish CArdiopulmonary BioImaging Study (SCAPIS). The radius was studied in relation to visual and densitometric assessment of emphysema, as well as to lung function tests and symptoms. Findings: The forty-seven individuals with visually detected emphysema had a significantly larger rAiDA (326 ± 49 µm), compared to non-emphysematous persons (291 ± 36 µm), p = 0.00001. Odds ratio per 1 µm for emphysema, adjusted for age, sex, height and weight was 1·021 (1·013 - 1·028), p<0·0001. Similar results were found when other lung function measures were assessed. Interpretation: AiDA can indicate distal airspace enlargement and is a potential biomarker for emphysema. A diagnostic accuracy study in patients with suspected lung disease is needed to establish AiDA as a diagnostic technique. Funding: The study has received support from the Swedish Heart and Lung Foundation, The Swedish Research Council, FORTE, the Crafoord foundation, the Swedish Governmental Agency for Innovation Systems, the ERA-NET project EuroNanoMed2, and governmental funding of clinical research within the National Health Services. Declaration of Interest: The funders of the study had no commercial interests. Ethical Approval: The study was approved by the Regional Ethical Review Board in Umea, Sweden, 2010/228-31, and performed according to the Declaration of Helsinki.

Cryptogenic Organizing Pneumonia Presenting as a Solitary Mass: Clinical, Imaging, and Pathologic Features.

BackgroundCryptogenic organizing pneumonia (COP), with a variety of radiologic findings, is a clinical pathological entity characterized by the presence of granulation tissue composed of fibroblasts/myofibroblasts and loose connective tissue in the alveoli and/or the distal bronchioles. Nevertheless, the presence of a solitary mass in COP is relatively rare. This study investigated the clinical, imaging, and pathologic features of COP with solitary mass form.Material/MethodsThis retrospective analysis included 12 patients (9 men and 3 women; age range 36–78 years; mean age 60±9 years) with surgery- or biopsy-proven COP with a solitary lung mass, diagnosed between June 2012 and December 2017 at the Department of Radiology in our hospital.ResultsAll patients experienced cough with expectoration and 8 patients had hemoptysis. All lesions were adjacent to the pleura. Mean size of the lesions was 4.2±0.9 cm (range, 3.2–6.1 cm). The upper left lobe was the site of the lesion in 4 patients. Six masses had heterogeneous density; among these, 4 had cavities and distal obstructive inflammation. The mass caused pleural indentation in 4 patients. Lymphadenopathy was seen in 7 patients. All specimens showed buds of granulation tissue within the lumen of the distal pulmonary airspaces, with significant increase in interstitial lymphocytes in 4 specimens.ConclusionsPatients with COP with solitary mass form are more susceptible to hemoptysis and the mass is prone to necrosis. Vascular bundles, exudation around the mass, interstitial lymphocyte infiltration, and mediastinal lymph node enlargement are common features.

A Case Report of Organizing Pneumonia /IgG4 Related Diseases

Organizing pneumonia form of idiopathic interstitial pneumonia characterized by lung inflammation and scarring that obstructs the small airways and air sacs of the lungs (alveoli). Organising pneumonia is defined pathologically by the presence in the distal air spaces of buds of granulation tissue progressing from fibrin exudates to loose collagen containing fibroblasts. Since organising pneumonia is a non-specific inflammatory pulmonary process, it may result from a number of causes. Pathologists may report features of organising pneumonia in association with conditions such as infectious pneumonia, lung abscess, empyema, lung cancer, bronchiectasis, broncholithiasis, chronic pulmonary fibrosis, aspiration pneumonia (giant cells and foreign bodies usually are present), adult respiratory distress syndrome, pulmonary infarction, and middle lobe syndrome. This is an interesting, yet challenging case trying to formulate a diagnosis of a patient presented with worsening of dyspnea over more than a year. The patient has history of unsuccessful treatment of eosinophilic asthma with biological agents while also on treatment with prednisone for query organizing pneumonia.

Mark1 regulates distal airspace expansion through type I pneumocyte flattening in lung development.

During the later stages of lung development, two types of pneumocytes, cuboidal type II (AECII) and flattened type I (AECI) alveolar epithelial cells, form distal lung saccules. Here, we highlight how fibroblasts expressing MAP-microtubule affinity regulating kinase 1 (Mark1) are required for the terminal stages of pulmonary development, called lung sacculation. In Mark1-knockout (KO) mice, distal sacculation and AECI flattening are significantly impaired. Fetal epithelial cells generate alveolar organoids and differentiate into pneumocytes when co-cultured with fibroblasts. However, the size of organoids decreased and AECI flattening was impaired in the presence of Mark1 KO fibroblasts. In Mark1 KO fibroblasts themselves, cilia formation and the Hedgehog pathway were suppressed, resulting in the loss of type I collagen expression. The addition of type I collagen restored AECI flattening in organoids co-cultured with Mark1 KO fibroblasts and rescued the decreased size of organoids. Mathematical modeling of distal lung sacculation supports the view that AECI flattening is necessary for the proper formation of saccule-like structures. These results suggest that Mark1-mediated fibroblast activation induces AECI flattening and thereby regulates distal lung sacculation.

Muc5b overexpression causes mucociliary dysfunction and enhances lung fibrosis in mice

The gain-of-function MUC5B promoter variant rs35705950 is the dominant risk factor for developing idiopathic pulmonary fibrosis (IPF). Here we show in humans that MUC5B, a mucin thought to be restricted to conducting airways, is co-expressed with surfactant protein C (SFTPC) in type 2 alveolar epithelia and in epithelial cells lining honeycomb cysts, indicating that cell types involved in lung fibrosis in distal airspace express MUC5B. In mice, we demonstrate that Muc5b concentration in bronchoalveolar epithelia is related to impaired mucociliary clearance (MCC) and to the extent and persistence of bleomycin-induced lung fibrosis. We also establish the ability of the mucolytic agent P-2119 to restore MCC and to suppress bleomycin-induced lung fibrosis in the setting of Muc5b overexpression. Our findings suggest that mucociliary dysfunction might play a causative role in bleomycin-induced pulmonary fibrosis in mice overexpressing Muc5b, and that MUC5B in distal airspaces is a potential therapeutic target in humans with IPF.