Perfusion imaging heterogeneity during NO inhalation distinguishes pulmonary arterial hypertension (PAH) from healthy subjects and has potential as an imaging biomarker.

BACKGROUND: Without aggressive treatment, pulmonary arterial hypertension (PAH) has a 5-year mortality of approximately 40%. A patient's response to vasodilators at diagnosis impacts the therapeutic options and prognosis. We hypothesized that analyzing perfusion images acquired before and during vasodilation could identify characteristic differences between PAH and control subjects. METHODS: We studied 5 controls and 4 subjects with PAH using HRCT and 13NN PET imaging of pulmonary perfusion and ventilation. The total spatial heterogeneity of perfusion (CV2Qtotal) and its components in the vertical (CV2Qvgrad) and cranio-caudal (CV2Qzgrad) directions, and the residual heterogeneity (CV2Qr), were assessed at baseline and while breathing oxygen and nitric oxide (O2 + iNO). The length scale spectrum of CV2Qr was determined from 10 to 110 mm, and the response of regional perfusion to O2 + iNO was calculated as the mean of absolute differences. Vertical gradients in perfusion (Qvgrad) were derived from perfusion images, and ventilation-perfusion distributions from images of 13NN washout kinetics. RESULTS: O2 + iNO significantly enhanced perfusion distribution differences between PAH and controls, allowing differentiation of PAH subjects from controls. During O2 + iNO, CV2Qvgrad was significantly higher in controls than in PAH (0.08 (0.055-0.10) vs. 6.7 × 10-3 (2 × 10-4-0.02), p < 0.001) with a considerable gap between groups. Qvgrad and CV2Qtotal showed smaller differences: - 7.3 vs. - 2.5, p = 0.002, and 0.12 vs. 0.06, p = 0.01. CV2Qvgrad had the largest effect size among the primary parameters during O2 + iNO. CV2Qr, and its length scale spectrum were similar in PAH and controls. Ventilation-perfusion distributions showed a trend towards a difference between PAH and controls at baseline, but it was not statistically significant. CONCLUSIONS: Perfusion imaging during O2 + iNO showed a significant difference in the heterogeneity associated with the vertical gradient in perfusion, distinguishing in this small cohort study PAH subjects from controls.

Plasma Soluble Suppression of Tumorigenicity-2 Associates with Ventilator Liberation in Acute Hypoxemic Respiratory Failure.

Rationale: Standard physiologic assessments of extubation readiness in patients with acute hypoxemic respiratory failure (AHRF) may not reflect lung injury resolution and could adversely affect clinical decision-making and patient outcomes. Objectives: We hypothesized that elevations in inflammatory plasma biomarkers sST2 (soluble suppression of tumorigenicity-2) and IL-6 indicate ongoing lung injury in AHRF and better inform patient outcomes compared with standard clinical assessments. Methods: We measured daily plasma biomarkers and physiologic variables in 200 patients with AHRF for up to 9 days after intubation. We tested the associations of baseline values with the primary outcome of unassisted breathing at Day 29. We analyzed the ability of serial biomarker measurements to inform successful ventilator liberation. Measurements and Main Results: Baseline sST2 concentrations were higher in patients dead or mechanically ventilated versus breathing unassisted at Day 29 (491.7 ng/ml [interquartile range (IQR), 294.5-670.1 ng/ml] vs. 314.4 ng/ml [IQR, 127.5-550.1 ng/ml]; P = 0.0003). Higher sST2 concentrations over time were associated with a decreased probability of ventilator liberation (hazard ratio, 0.80 per log-unit increase; 95% confidence interval [CI], 0.75-0.83; P = 0.03). Patients with higher sST2 concentrations on the day of liberation were more likely to fail liberation compared with patients who remained successfully liberated (320.9 ng/ml [IQR, 181.1- 495.6 ng/ml] vs. 161.6 ng/ml [IQR, 95.8-292.5 ng/ml]; P = 0.002). Elevated sST2 concentrations on the day of liberation decreased the odds of successful liberation when adjusted for standard physiologic parameters (odds ratio, 0.325; 95% CI, 0.119-0.885; P = 0.03). IL-6 concentrations did not associate with outcomes. Conclusions: Using sST2 concentrations to guide ventilator management may more accurately reflect underlying lung injury and outperform traditional measures of readiness for ventilator liberation.

Smoking and Human Immunodeficiency Virus 1 Infection Promote Retention of CD8+ T Cells in the Airway Mucosa.

Smoking and human immunodeficiency virus 1 (HIV-1) infection are risk factors for chronic obstructive pulmonary disease (COPD), which is among the most common comorbid conditions in people living with HIV-1. HIV-1 infection leads to persistent expansion of CD8+ T cells, and CD8+ T cell-mediated inflammation has been implicated in COPD pathogenesis. In this study, we investigated the effects of HIV-1 infection and smoking on T-cell dynamics in patients at risk of COPD. BAL fluid, endobronchial brushings, and blood from HIV-1 infected and uninfected nonsmokers and smokers were analyzed by flow cytometry, and lungs were imaged by computed tomography. Chemokines were measured in BAL fluid, and CD8+ T-cell chemotaxis in the presence of cigarette smoke extract was assessed in vitro. HIV-1 infection increased CD8+ T cells in the BAL fluid, but this increase was abrogated by smoking. Smokers had reduced BAL fluid concentrations of the T cell-recruiting chemokines CXCL10 and CCL5, and cigarette smoke extract inhibited CXCL10 and CCL5 production by macrophages and CD8+ T-cell transmigration in vitro. In contrast to the T cells in BAL fluid, CD8+ T cells in endobronchial brushings were increased in HIV-1-infected smokers, which was driven by an accumulation of effector memory T cells in the airway mucosa and an increase in tissue-resident memory T cells. Mucosal CD8+ T-cell numbers inversely correlated with lung aeration, suggesting an association with inflammation and remodeling. HIV-1 infection and smoking lead to retention of CD8+ T cells within the airway mucosa.

Quantitative assessment of airway remodelling and response to allergen in asthma.

BACKGROUND AND OBJECTIVE: In vivo evaluation of the microstructural differences between asthmatic and non-asthmatic airways and their functional consequences is relevant to understanding and, potentially, treating asthma. In this study, we use endobronchial optical coherence tomography to investigate how allergic airways with asthma differ from allergic non-asthmatic airways in baseline microstructure and in response to allergen challenge. METHODS: A total of 45 subjects completed the study, including 20 allergic, mildly asthmatic individuals, 22 non-asthmatic allergic controls and 3 healthy controls. A 3-cm airway segment in the right middle and right upper lobe were imaged in each subject immediately before and 24 h following segmental allergen challenge to the right middle lobe. Relationships between optical airway measurements (epithelial and mucosal thicknesses, mucosal buckling and mucus) and airway obstruction (FEV1 /FVC (forced expiratory volume in 1 s/forced vital capacity) and FEV1 % (FEV1 as a percentage of predictive value)) were investigated. RESULTS: Significant increases at baseline and in response to allergen were observed for all four of our imaging metrics in the asthmatic airways compared to the non-asthmatic airways. Epithelial thickness and mucosal buckling exhibited a significant relationship to FEV1 /FVC in the asthmatic group. CONCLUSION: Simultaneous assessments of airway microstructure, buckling and mucus revealed both structural and functional differences between the mildly asthmatic and control groups, with airway buckling seeming to be the most relevant factor. The results of this study demonstrate that a comprehensive, microstructural approach to assessing the airways may be important in future asthma studies as well as in the monitoring and treatment of asthma.

Hypoxic Pulmonary Vasoconstriction Does Not Explain All Regional Perfusion Redistribution in Asthma.

RATIONALE: Regional hypoventilation in bronchoconstricted patients with asthma is spatially associated with reduced perfusion, which is proposed to result from hypoxic pulmonary vasoconstriction (HPV). OBJECTIVES: To determine the role of HPV in the regional perfusion redistribution in bronchoconstricted patients with asthma. METHODS: Eight patients with asthma completed positron emission tomographic/computed tomographic lung imaging at baseline and after bronchoconstriction, breathing either room air or 80% oxygen (80% O2) on separate days. Relative perfusion, specific ventilation (sV), and gas fraction (Fgas) in the 25% of the lung with the lowest specific ventilation (sVlow) and the remaining lung (sVhigh) were quantified and compared. MEASUREMENTS AND MAIN RESULTS: In the sVlow region, bronchoconstriction caused a significant decrease in sV under both room air and 80% O2 conditions (baseline vs. bronchoconstriction, mean ± SD, 1.02 ± 0.20 vs. 0.35 ± 0.19 and 1.03 ± 0.20 vs. 0.32 ± 0.16, respectively; P < 0.05). In the sVlow region, relative perfusion decreased after bronchoconstriction under room air conditions and also, to a lesser degree, under 80% O2 conditions (1.02 ± 0.19 vs. 0.72 ± 0.08 [P < 0.001] and 1.08 ± 0.19 vs. 0.91 ± 0.12 [P < 0.05], respectively). The Fgas increased after bronchoconstriction under room air conditions only (0.99 ± 0.04 vs. 1.00 ± 0.02; P < 0.05). The sVlow subregion analysis indicated that some of the reduction in relative perfusion after bronchoconstriction under 80% O2 conditions occurred as a result of the presence of regional hypoxia. However, relative perfusion was also significantly reduced in sVlow subregions that were hyperoxic under 80% O2 conditions. CONCLUSIONS: HPV is not the only mechanism that contributes to perfusion redistribution in bronchoconstricted patients with asthma, suggesting that another nonhypoxia mechanism also contributes. We propose that this nonhypoxia mechanism may be either direct mechanical interactions and/or unidentified intercellular signaling between constricted airways, the parenchyma, and the surrounding vasculature.

High-flow oxygen therapy and other inhaled therapies in intensive care units.

In this Series paper, we review the current evidence for the use of high-flow oxygen therapy, inhaled gases, and aerosols in the care of critically ill patients. The available evidence supports the use of high-flow nasal cannulae for selected patients with acute hypoxaemic respiratory failure. Heliox might prevent intubation or improve gas flow in mechanically ventilated patients with severe asthma. Additionally, it might improve the delivery of aerosolised bronchodilators in obstructive lung disease in general. Inhaled nitric oxide might improve outcomes in a subset of patients with postoperative pulmonary hypertension who had cardiac surgery; however, it has not been shown to provide long-term benefit in patients with acute respiratory distress syndrome (ARDS). Inhaled prostacyclins, similar to inhaled nitric oxide, are not recommended for routine use in patients with ARDS, but can be used to improve oxygenation in patients who are not adequately stabilised with traditional therapies. Aerosolised bronchodilators are useful in mechanically ventilated patients with asthma and chronic obstructive pulmonary disease, but are not recommended for those with ARDS. Use of aerosolised antibiotics for ventilator-associated pneumonia and ventilator-associated tracheobronchitis shows promise, but the delivered dose can be highly variable if proper attention is not paid to the delivery method.

Plasma Concentrations of Soluble Suppression of Tumorigenicity-2 and Interleukin-6 Are Predictive of Successful Liberation From Mechanical Ventilation in Patients With the Acute Respiratory Distress Syndrome.

OBJECTIVES: Soluble suppression of tumorigenicity-2 and interleukin-6 concentrations have been associated with the inflammatory cascade of acute respiratory distress syndrome. We determined whether soluble suppression of tumorigenicity-2 and interleukin-6 levels can be used as prognostic biomarkers to guide weaning from mechanical ventilation and predict the need for reintubation. DESIGN, SETTING, AND PATIENTS: We assayed plasma soluble suppression of tumorigenicity-2 (n = 826) concentrations and interleukin-6 (n = 755) concentrations in the Fluid and Catheter Treatment Trial, a multicenter randomized controlled trial of conservative fluid management in acute respiratory distress syndrome. We tested whether soluble suppression of tumorigenicity-2 and interleukin-6 levels were associated with duration of mechanical ventilation, the probability of passing a weaning assessment, and the need for reintubation. MEASUREMENTS AND MAIN RESULTS: In models adjusted for Acute Physiology and Chronic Health Evaluation score and other relevant variables, patients with higher day 0 and day 3 median soluble suppression of tumorigenicity-2 and interleukin-6 concentrations had decreased probability of extubation over time (day 0 soluble suppression of tumorigenicity-2: hazard ratio, 0.85; 95% CI, 0.72-1.00; p = 0.05; day 0 interleukin-6: hazard ratio, 0.64; 95% CI, 0.54-0.75; p < 0.0001; day 3 soluble suppression of tumorigenicity-2: hazard ratio, 0.64; 95% CI, 0.54-0.75; p < 0.0001; and day 3 interleukin-6: hazard ratio, 0.73; 95% CI, 0.62-0.85; p = 0.0001). Higher biomarker concentrations were also predictive of decreased odds of passing day 3 weaning assessments (soluble suppression of tumorigenicity-2: odds ratio, 0.62: 95% CI, 0.44-0.87; p = 0.006 and interleukin-6: odds ratio, 0.61; 95% CI, 0.43-0.85; p = 0.004) and decreased odds of passing a spontaneous breathing trial (soluble suppression of tumorigenicity-2: odds ratio, 0.45; 95% CI, 0.28-0.71; p = 0.0007 and interleukin-6 univariate analysis only: odds ratio, 0.55; 95% CI, 0.36-0.83; p = 0.005). Finally, higher biomarker levels were significant predictors of the need for reintubation for soluble suppression of tumorigenicity-2 (odds ratio, 3.23; 95% CI, 1.04-10.07; p = 0.04) and for interleukin-6 (odds ratio, 2.58; 95% CI, 1.14-5.84; p = 0.02). CONCLUSIONS: Higher soluble suppression of tumorigenicity-2 and interleukin-6 concentrations are each associated with worse outcomes during weaning of mechanical ventilation and increased need for reintubation in patients with acute respiratory distress syndrome. Biomarker-directed ventilator management may lead to improved outcomes in weaning of mechanical ventilation in patients with acute respiratory distress syndrome.

Lung Metabolic Activation as an Early Biomarker of Acute Respiratory Distress Syndrome and Local Gene Expression Heterogeneity.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is an inflammatory condition comprising diffuse lung edema and alveolar damage. ARDS frequently results from regional injury mechanisms. However, it is unknown whether detectable inflammation precedes lung edema and opacification and whether topographically differential gene expression consistent with heterogeneous injury occurs in early ARDS. The authors aimed to determine the temporal relationship between pulmonary metabolic activation and density in a large animal model of early ARDS and to assess gene expression in differentially activated regions. METHODS: The authors produced ARDS in sheep with intravenous lipopolysaccharide (10 ng ⋅ kg ⋅ h) and mechanical ventilation for 20 h. Using positron emission tomography, the authors assessed regional cellular metabolic activation with 2-deoxy-2-[(18)F]fluoro-D-glucose, perfusion and ventilation with NN-saline, and aeration using transmission scans. Species-specific microarray technology was used to assess regional gene expression. RESULTS: Metabolic activation preceded detectable increases in lung density (as required for clinical diagnosis) and correlated with subsequent histologic injury, suggesting its predictive value for severity of disease progression. Local time courses of metabolic activation varied, with highly perfused and less aerated dependent lung regions activated earlier than nondependent regions. These regions of distinct metabolic trajectories demonstrated differential gene expression for known and potential novel candidates for ARDS pathogenesis. CONCLUSIONS: Heterogeneous lung metabolic activation precedes increases in lung density in the development of ARDS due to endotoxemia and mechanical ventilation. Local differential gene expression occurs in these early stages and reveals molecular pathways relevant to ARDS biology and of potential use as treatment targets.

Effects of inhaled CO administration on acute lung injury in baboons with pneumococcal pneumonia.

Inhaled carbon monoxide (CO) gas has therapeutic potential for patients with acute respiratory distress syndrome if a safe, evidence-based dosing strategy and a ventilator-compatible CO delivery system can be developed. In this study, we used a clinically relevant baboon model of Streptococcus pneumoniae pneumonia to 1) test a novel, ventilator-compatible CO delivery system; 2) establish a safe and effective CO dosing regimen; and 3) investigate the local and systemic effects of CO therapy on inflammation and acute lung injury (ALI). Animals were inoculated with S. pneumoniae (10(8)-10(9) CFU) (n = 14) or saline vehicle (n = 5); in a subset with pneumonia (n = 5), we administered low-dose, inhaled CO gas (100-300 ppm × 60-90 min) at 0, 6, 24, and/or 48 h postinoculation and serially measured blood carboxyhemoglobin (COHb) levels. We found that CO inhalation at 200 ppm for 60 min is well tolerated and achieves a COHb of 6-8% with ambient CO levels ≤ 1 ppm. The COHb level measured at 20 min predicted the 60-min COHb level by the Coburn-Forster-Kane equation with high accuracy. Animals given inhaled CO + antibiotics displayed significantly less ALI at 8 days postinoculation compared with antibiotics alone. Inhaled CO was associated with activation of mitochondrial biogenesis in the lung and with augmentation of renal antioxidative programs. These data support the feasibility of safely delivering inhaled CO gas during mechanical ventilation and provide preliminary evidence that CO may accelerate the resolution of ALI in a clinically relevant nonhuman primate pneumonia model.

Pulmonary vascular response patterns during exercise in interstitial lung disease.

When overt pulmonary hypertension arises in interstitial lung disease (ILD), it contributes to exercise intolerance. We sought to determine the functional significance of abnormal pulmonary arterial pressure (PAP) responses to exercise in ILD.27 ILD patients and 11 age-matched controls underwent invasive cardiopulmonary exercise testing (iCPET). Mean PAP (mPAP) was indexed to cardiac output (Q'T) during exercise, with a mPAP-Q'T slope ≥3 mmHg·min·L(-1) defined as an abnormal pulmonary vascular response.All control subjects had mPAP-Q'T slopes <3 mmHg·min·L(-1) (mean±sem 1.5±0.1 mmHg·min·L(-1)). 15 ILD patients had mPAP-Q'T slopes ≥3 mmHg·min·L(-1) (4.1±0.2 mmHg·min·L(-1)) and were labelled as having ILD plus pulmonary vascular dysfunction (PVD). Subjects without pulmonary hypertension and with mPAP-Q´T slopes <3 mmHg·min·L(-1) (1.9±0. 2 mmHg·min·L(-1)) were labelled as ILD minus PVD (n=12). ILD+PVD and ILD-PVD patients did not differ in terms of age, sex, body mass index, pulmonary function testing or degree of exercise oxygen desaturation. Peak oxygen consumption was lower in ILD+PVD than in ILD-PVD (13.0±0.9 versus 17±1.1 mL·kg(-1)·min(-1), p=0.012) and controls (19.8±1.7 mL·kg(-1)·min(-1), p=0.003). ILD+PVD patients had increased dead space volume (VD)/tidal volume (VT) and minute ventilation/carbon dioxide production at the anaerobic threshold.In ILD, mPAP-Q'T slope ≥3 mmHg·min·L(-1) is associated with lower peak oxygen consumption, increased VD/VT and inefficient ventilation. While noninvasive parameters were unable to predict those with abnormal pulmonary vascular responses to exercise, iCPET-derived mPAP-Q'T slope may aid in identifying physiologically significant, early pulmonary vascular disease in ILD.

MATHEMATICAL MODELING OF VENTILATION DEFECTS IN ASTHMA.

Airway narrowing by smooth muscle constriction is a hallmark of asthma attacks that may cause severe difficulties of breathing. However, the causes of asthma and the underlying mechanisms are not fully understood. Bronchoconstriction within a bronchial tree involves complex interactions among the airways that lead to the emergence of regions of poor ventilation (ventilation defects, VDefs) in the lungs. The emphasis of this review is on mathematical modeling of the mechanisms involved in bronchoconstriction and the emergence of the complex airway behavior that leads to VDefs. Additionally, the review discusses characteristic model behaviors and experimental data to demonstrate advances and limitations of different models.

Effect of local tidal lung strain on inflammation in normal and lipopolysaccharide-exposed sheep*.

OBJECTIVES: Regional tidal lung strain may trigger local inflammation during mechanical ventilation, particularly when additional inflammatory stimuli are present. However, it is unclear whether inflammation develops proportionally to tidal strain or only above a threshold. We aimed to 1) assess the relationship between regional tidal strain and local inflammation in vivo during the early stages of lung injury in lungs with regional aeration heterogeneity comparable to that of humans and 2) determine how this strain-inflammation relationship is affected by endotoxemia. DESIGN: Interventional animal study. SETTING: Experimental laboratory and PET facility. SUBJECTS: Eighteen 2- to 4-month-old sheep. INTERVENTIONS: Three groups of sheep (n = 6) were mechanically ventilated to the same plateau pressure (30-32 cm H2O) with high-strain (VT = 18.2 ± 6.5 mL/kg, positive end-expiratory pressure = 0), high-strain plus IV lipopolysaccharide (VT = 18.4 ± 4.2 mL/kg, positive end-expiratory pressure = 0), or low-strain plus lipopolysaccharide (VT = 8.1 ± 0.2 mL/kg, positive end-expiratory pressure = 17 ± 3 cm H2O). At baseline, we acquired respiratory-gated PET scans of inhaled NN to measure tidal strain from end-expiratory and end-inspiratory images in six regions of interest. After 3 hours of mechanical ventilation, dynamic [F]fluoro-2-deoxy-D-glucose scans were acquired to quantify metabolic activation, indicating local neutrophilic inflammation, in the same regions of interest. MEASUREMENTS AND MAIN RESULTS: Baseline regional tidal strain had a significant effect on [F]fluoro-2-deoxy-D-glucose net uptake rate Ki in high-strain lipopolysaccharide (p = 0.036) and on phosphorylation rate k3 in high-strain (p = 0.027) and high-strain lipopolysaccharide (p = 0.004). Lipopolysaccharide exposure increased the k3-tidal strain slope three-fold (p = 0.009), without significant lung edema. The low-strain lipopolysaccharide group showed lower baseline regional tidal strain (0.33 ± 0.17) than high-strain (1.21 ± 0.62; p < 0.001) or high-strain lipopolysaccharide (1.26 ± 0.44; p < 0.001) and lower k3 (p < 0.001) and Ki (p < 0.05) than high-strain lipopolysaccharide. CONCLUSIONS: Local inflammation develops proportionally to regional tidal strain during early lung injury. The regional inflammatory effect of strain is greatly amplified by IV lipopolysaccharide. Tidal strain enhances local [F]fluoro-2-deoxy-D-glucose uptake primarily by increasing the rate of intracellular [F]fluoro-2-deoxy-D-glucose phosphorylation.

Lung [(18)F]fluorodeoxyglucose uptake and ventilation-perfusion mismatch in the early stage of experimental acute smoke inhalation.

BACKGROUND: Acute lung injury occurs in a third of patients with smoke inhalation injury. Its clinical manifestations usually do not appear until 48-72 h after inhalation. Identifying inflammatory changes that occur in pulmonary parenchyma earlier than that could provide insight into the pathogenesis of smoke-induced acute lung injury. Furthermore, noninvasive measurement of such changes might lead to earlier diagnosis and treatment. Because glucose is the main source of energy for pulmonary inflammatory cells, the authors hypothesized that its pulmonary metabolism is increased shortly after smoke inhalation, when classic manifestations of acute lung injury are not yet expected. METHODS: In five sheep, the authors induced unilateral injury with 48 breaths of cotton smoke while the contralateral lung served as control. The authors used positron emission tomography with: (1) [F]fluorodeoxyglucose to measure metabolic activity of pulmonary inflammatory cells; and (2) [N]nitrogen in saline to measure shunt and ventilation-perfusion distributions separately in the smoke-exposed and control lungs. RESULTS: The pulmonary [F]fluorodeoxyglucose uptake rate was increased at 4 h after smoke inhalation (mean ± SD: 0.0031 ± 0.0013 vs. 0.0026 ± 0.0010 min; P < 0.05) mainly as a result of increased glucose phosphorylation. At this stage, there was no worsening in lung aeration or shunt. However, there was a shift of perfusion toward units with lower ventilation-to-perfusion ratio (mean ratio ± SD: 0.82 ± 0.10 vs. 1.12 ± 0.02; P < 0.05) and increased heterogeneity of the ventilation-perfusion distribution (mean ± SD: 0.21 ± 0.07 vs. 0.13 ± 0.01; P < 0 .05). CONCLUSION: Using noninvasive imaging, the authors demonstrated that increased pulmonary [F]fluorodeoxyglucose uptake and ventilation-perfusion mismatch occur early after smoke inhalation.

Compartmentalized chemokine-dependent regulatory T-cell inhibition of allergic pulmonary inflammation.

BACKGROUND: Induction of endogenous regulatory T (Treg) cells represents an exciting new potential modality for treating allergic diseases, such as asthma. Treg cells have been implicated in the regulation of asthma, but the anatomic location in which they exert their regulatory function and the mechanisms controlling the migration necessary for their suppressive function in asthma are not known. Understanding these aspects of Treg cell biology will be important for harnessing their power in the clinic. OBJECTIVE: We sought to determine the anatomic location at which Treg cells exert their regulatory function in the sensitization and effector phases of allergic asthma and to determine the chemokine receptors that control the migration of Treg cells to these sites in vivo in both mice and human subjects. METHODS: The clinical efficacy and anatomic location of adoptively transferred chemokine receptor-deficient CD4(+)CD25(+) forkhead box protein 3-positive Treg cells was determined in the sensitization and effector phases of allergic airway inflammation in mice. The chemokine receptor expression profile was determined on Treg cells recruited into the human airway after bronchoscopic segmental allergen challenge of asthmatic patients. RESULTS: We show that CCR7, but not CCR4, is required on Treg cells to suppress allergic airway inflammation during the sensitization phase. In contrast, CCR4, but not CCR7, is required on Treg cells to suppress allergic airway inflammation during the effector phase. Consistent with our murine studies, human subjects with allergic asthma had an increase in CCR4-expressing functional Treg cells in the lungs after segmental allergen challenge. CONCLUSION: The location of Treg cell function differs during allergic sensitization and allergen-induced recall responses in the lung, and this differential localization is critically dependent on differential chemokine function.

Prognostic and diagnostic value of plasma soluble suppression of tumorigenicity-2 concentrations in acute respiratory distress syndrome.

OBJECTIVES: Soluble suppression of tumorigenicity-2 is a biomarker of myocardial strain and inflammation. The characteristics of acute respiratory distress syndrome include inflammation and cardiovascular dysfunction. We sought to determine whether plasma soluble suppression of tumorigenicity-2 concentration is associated with outcome and response to conservative fluid management and whether soluble suppression of tumorigenicity-2 concentration discriminates acute respiratory distress syndrome from decompensated heart failure. DESIGN: A retrospective analysis of the Fluid and Catheter Treatment Trial, a multi-center randomized controlled trial of conservative fluid management in the acute respiratory distress syndrome, as well as of a cohort of patients with decompensated heart failure. SETTING: Twenty acute care hospitals. PATIENTS: Eight hundred twenty-six patients with acute respiratory distress syndrome and 209 patients with acutely decompensated heart failure. MEASUREMENTS AND MAIN RESULTS: Nonsurvivors had higher day 0 (p < 0.0001) and day 3 (p < 0.0001) soluble suppression of tumorigenicity-2 concentrations. After adjustment for severity of illness, higher soluble suppression of tumorigenicity-2 concentration was associated with mortality, with odds ratioadj 1.47 (95% CI, 0.99-2.20; p = 0.06) at day 0, 2.94 (95% CI, 2.00-4.33; p < 0.0001) at day 3, and 3.63 (95% CI, 2.38-5.53; p < 0.0001) if soluble suppression of tumorigenicity-2 increased between days. Cumulative fluid balance was more positive among patients with higher day 0 (median, 5,212 mL [interquartile range, 200-12,284 mL] vs median, 2,020 mL [interquartile range, -2,034 to 7,091 mL]; p < 0.0001) and day 3 soluble suppression of tumorigenicity-2 (median, 7,678 mL [interquartile range, 2,217-14,278 mL] vs median, 1,492 mL [interquartile range, -2,384 to 6,239 mL]; p < 0.0001). Soluble suppression of tumorigenicity-2 showed excellent discriminative ability between the Fluid and Catheter Treatment Trial and heart failure populations (area under receiver-operating characteristic curve = 0.98; p < 0.0001). CONCLUSIONS: Higher soluble suppression of tumorigenicity-2 concentrations are associated with worse outcome in acute respiratory distress syndrome and may have value for discriminating acute respiratory distress syndrome from heart failure.

Regional lung derecruitment and inflammation during 16 hours of mechanical ventilation in supine healthy sheep.

BACKGROUND: Lung derecruitment is common during general anesthesia. Mechanical ventilation with physiological tidal volumes could magnify derecruitment, and produce lung dysfunction and inflammation. The authors used positron emission tomography to study the process of derecruitment in normal lungs ventilated for 16 h and the corresponding changes in regional lung perfusion and inflammation. METHODS: Six anesthetized supine sheep were ventilated with VT=8 ml/kg and positive end-expiratory pressure=0. Transmission scans were performed at 2-h intervals to assess regional aeration. Emission scans were acquired at baseline and after 16 h for the following tracers: (1) F-fluorodeoxyglucose to evaluate lung inflammation and (2) NN to calculate regional perfusion and shunt fraction. RESULTS: Gas fraction decreased from baseline to 16 h in dorsal (0.31±0.13 to 0.14±0.12, P<0.01), but not in ventral regions (0.61±0.03 to 0.63±0.07, P=nonsignificant), with time constants of 1.5-44.6 h. Although the vertical distribution of relative perfusion did not change from baseline to 16 h, shunt increased in dorsal regions (0.34±0.23 to 0.63±0.35, P<0.01). The average pulmonary net F-fluorodeoxyglucose uptake rate in six regions of interest along the ventral-dorsal direction increased from 3.4±1.4 at baseline to 4.1±1.5 10(-3)/min after 16 h (P<0.01), and the corresponding average regions of interest F-fluorodeoxyglucose phosphorylation rate increased from 2.0±0.2 to 2.5±0.2 10(-2)/min (P<0.01). CONCLUSIONS: When normal lungs are mechanically ventilated without positive end-expiratory pressure, loss of aeration occurs continuously for several hours and is preferentially localized to dorsal regions. Progressive lung derecruitment was associated with increased regional shunt, implying an insufficient hypoxic pulmonary vasoconstriction. The increased pulmonary net uptake and phosphorylation rates of F-fluorodeoxyglucose suggest an incipient inflammation in these initially normal lungs.

Long-term tezacaftor/ivacaftor safety and efficacy in people with cystic fibrosis and an F508del-CFTR mutation: 96-week, open-label extension of the EXTEND trial.

BACKGROUND: Study 661-110 (EXTEND) is a phase 3, open-label, three-part rollover study designed to assess the long-term safety and efficacy of tezacaftor/ivacaftor (TEZ/IVA) in participants aged ≥12 years homozygous for F508del (F/F) or heterozygous for F508del and a residual function mutation (F/RF). TEZ/IVA was shown to be safe and efficacious for up to 120 weeks in Part A. Here we report results from Part B, which evaluated safety and efficacy for an additional 96 weeks. METHODS: Part B enrolled participants aged ≥12 years with CF and F/F or F/RF genotypes who completed TEZ/IVA treatment in either Study 661-110 Part A, Study 661-112 (F/F), or Study 661-114 (F/F). Participants received TEZ 100 mg/IVA 150 mg fixed-dose combination once daily (morning) and IVA 150 mg once daily (evening) for 96 weeks. Safety endpoints included adverse events (AEs) and serum liver function tests. Efficacy endpoints included absolute change from baseline in percent predicted forced expiratory volume in 1 second (ppFEV1) and pulmonary exacerbation (PEx) rate. RESULTS: 464 participants were enrolled from Part A (n=377) and other eligible studies (n=87); 463 received ≥1 dose of TEZ/IVA. Overall, 92.2% had ≥1 AE, 0.9% had AEs leading to treatment discontinuation, and 29.4% reported serious AEs. The most common AEs, which were generally consistent with common manifestations of CF, included infective PEx of CF, cough, nasopharyngitis, hemoptysis, and headache. Lung function was maintained over 96 weeks in both genotype groups. PEx rates per year were comparable with Part A. CONCLUSIONS: TEZ/IVA was generally safe and well tolerated over a further 96 weeks; safety data were consistent with Part A. Improvements in ppFEV1 and PEx rates were maintained for an additional 96 weeks in Part B.