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Diagnosis of interstitial lung disease (ILD) requires a multidisciplinary discussion approach that includes clinicians, radiologists, and pathologists. Surgical lung biopsy (SLB) is currently the recommended standard in obtaining pathologic specimens for patients with ILD requiring a tissue diagnosis. The increased diagnostic confidence and accuracy provided by microscopic pathology assessment of SLB specimens must be balanced with the associated risks in patients with ILD. This document was developed by the SLB Working Group of the Pulmonary Fibrosis Foundation, composed of a multidisciplinary group of ILD physicians, including pulmonologists, radiologists, pathologists, and thoracic surgeons. In this document, we present an up-to-date literature review of the indications, contraindications, risks, and alternatives to SLB in the diagnosis of fibrotic ILD; outline an integrated approach to the decision-making around SLB in the diagnosis of fibrotic ILD; and provide practical information to maximize the yield and safety of SLB.

Background: This guideline addresses the diagnosis of hypersensitivity pneumonitis (HP). It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax. Methods: Systematic reviews were performed for six questions. The evidence was discussed, and then recommendations were formulated by a multidisciplinary committee of experts in the field of interstitial lung disease and HP using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Results: The guideline committee defined HP, and clinical, radiographic, and pathological features were described. HP was classified into nonfibrotic and fibrotic phenotypes. There was limited evidence that was directly applicable to all questions. The need for a thorough history and a validated questionnaire to identify potential exposures was agreed on. Serum IgG testing against potential antigens associated with HP was suggested to identify potential exposures. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. For patients with fibrotic HP, suggestions were made in favor of obtaining BAL for lymphocyte cellular analysis, transbronchial lung cryobiopsy, and surgical lung biopsy. Diagnostic criteria were established, and a diagnostic algorithm was created by expert consensus. Knowledge gaps were identified as future research directions. Conclusions: The guideline committee developed a systematic approach to the diagnosis of HP. The approach should be reevaluated as new evidence accumulates.

Background: At present, no approved pharmacotherapies are available for unclassifiable interstitial lung disease (ILD), which is characterised by progressive fibrosis of the lung. We aimed to assess the efficacy and safety of pirfenidone in patients with progressive fibrosing unclassifiable ILD., Methods: We did a multicentre, double-blind, randomised, placebo-controlled phase 2 trial at 70 centres in Australia, Belgium, Canada, Czech Republic, Denmark, Germany, Greece, Ireland, Israel, Italy, Poland, Portugal, Spain, and the UK. Eligible patients (aged ≥18-85 years) had progressive fibrosing unclassifiable ILD, a percent predicted forced vital capacity (FVC) of 45% or higher and percent predicted carbon monoxide diffusing capacity (DLco) of 30% or higher, more than 10% fibrosis on high-resolution CT, and a high-resolution CT from the previous 12 months. Patients were randomly assigned (1:1) to 2403 mg oral pirfenidone daily or placebo using a central validated interactive voice or web-based response system, stratified by concomitant mycophenolate mofetil use and presence or absence of interstitial pneumonia with autoimmune features. Investigators, site personnel, and patients were masked to treatment assignment. The primary endpoint was mean predicted change in FVC from baseline over 24 weeks, measured by daily home spirometry. Secondary endpoints were change in FVC measured by site spirometry, proportion of patients who had a more than 5% or more than 10% absolute or relative decline in percent predicted FVC measured by clinic-based spirometry, change in percent predicted DLco, change in 6-min walk distance (6MWD), change in University of California San Diego-Shortness of Breath Questionnaire (UCSD-SOBQ) score, change in Leicester Cough Questionnaire score, change in cough visual analogue scale, and changes in total and subscores of the St George's Respiratory Questionnaire (SGRQ), all of which were compared with baseline. Additional secondary endpoints included proportion of patients who had non-elective hospitalisation (respiratory and all-cause) and acute exacerbations, and progression-free survival. Efficacy was analysed in the intention-to-treat (ITT) population, which included all randomly assigned patients. Safety was assessed in the safety analysis set, which included all randomly assigned patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, NCT03099187, and is no longer recruiting., Findings: Between May 15, 2017, and June 5, 2018, 253 patients were randomly assigned to receive 2403 mg pirfenidone (n=127) or placebo (n=126) and were included in the ITT analysis set. Analysis of the primary endpoint was affected by intraindividual variability in home spirometry values, which prevented application of the prespecified statistical model. Over 24 weeks, predicted median change in FVC measured by home spirometry was -87·7 mL (Q1-Q3 -338·1 to 148·6) in the pirfenidone group versus -157·1 mL (-370·9 to 70·1) in the placebo group. Over 24 weeks, predicted mean change in FVC measured by site spirometry was lower in patients given pirfenidone than placebo (treatment difference 95·3 mL [95% CI 35·9 to 154·6], p=0·002). Compared with the placebo group, patients in the pirfenidone group were less likely to have a decline in FVC of more than 5% (odds ratio [OR] 0·42 [95% CI 0·25 to 0·69], p=0·001) or more than 10% (OR 0·44 [0·23 to 0·84], p=0·011). At week 24, mean change in DLco from baseline was -0·7% (SD 7·1) for the pirfenidone group and -2·5% (8·8) for the placebo group, and mean change in 6MWD from baseline was -2·0 m (68·1) for the pirfenidone group and -26·7 m (79·3) for the placebo group. Changes from baseline in UCSD-SOBQ, Leicester Cough Questionnaire score, cough visual analogue scale, and SGRQ scores were similar between the pirfenidone and placebo groups at week 24. Analysis of acute exacerbations, hospital admissions, and time to death from respiratory causes during the study yielded no meaningful results due to a small number of events. No differences in progression-free survival were identified between the pirfenidone and placebo groups, irrespective of the definition of progression-free survival used. Treatment-emergent adverse events were reported in 120 (94%) of 127 patients in the pirfenidone group and 101 (81%) of 124 patients in the placebo group. Serious treatment-emergent adverse events were reported in 18 (14%) patients in the pirfenidone group and 20 (16%) patients in the placebo group. The most common treatment-related treatment-emergent adverse events were gastrointestinal disorders (60 [47%] in the pirfenidone group vs 32 [26%] in the placebo group), fatigue (16 [13%] vs 12 [10%]), and rash (13 [10%] vs nine [7%])., Interpretation: Although the planned statistical model could not be applied to the primary endpoint data, analysis of key secondary endpoints suggests that patients with progressive fibrosing unclassifiable ILD could benefit from pirfenidone treatment, which has an acceptable safety and tolerability profile. These findings support further investigation of pirfenidone as an effective treatment for patients with progressive fibrotic unclassifiable ILD., Funding: F Hoffmann-La Roche., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The pathogenesis of idiopathic pulmonary fibrosis (IPF), an intractable interstitial lung disease, is unclear. Recessive mutations in some genes implicated in Hermansky-Pudlak syndrome (HPS) cause HPS-associated interstitial pneumonia (HPSIP), a clinical entity that is similar to IPF. We previously reported that HPS1 -/- embryonic stem cell-derived 3D lung organoids showed fibrotic changes. Here, we show that the introduction of all HPS mutations associated with HPSIP promotes fibrotic changes in lung organoids, while the deletion of HPS8, which is not associated with HPSIP, does not. Genome-wide expression analysis revealed the upregulation of interleukin-11 (IL-11) in epithelial cells from HPS mutant fibrotic organoids. IL-11 was detected predominantly in type 2 alveolar epithelial cells in end-stage IPF, but was expressed more broadly in HPSIP. Finally, IL-11 induced fibrosis in WT organoids, while its deletion prevented fibrosis in HPS4 -/- organoids, suggesting IL-11 as a therapeutic target. hPSC-derived 3D lung organoids are, therefore, a valuable resource to model fibrotic lung disease., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Pulmonary fibrosis (PF) is a rare, progressive disease that affects patients and their loved ones on many levels. We sought to better understand the needs and interests of PF patients and their loved ones (collectively "reader-participants") by systematically analyzing their engagement with the World Wide Web (the current version referred to as Web 2.0)., Methods: Data were collected from three PF-focused, interactive websites hosted by physician-investigators with expertise in PF. All data generated by reader-participants for approximately 10 months were downloaded and then analyzed using qualitative content analysis methods., Results: PF experts posted 38 blog entries and reader-participants posted 40 forum entries. Blogs received 363 responses, and forum entries received 108 responses from reader-participants. Reader-participants primarily used the three websites to seek information from or offer a contribution to the PF community. Information was sought about PF symptoms, diagnosis, prognosis, treatments, research, pathophysiology, and disease origin; reader-participants also made requests for new posts and pleas for research and sought clarification on existing content. Contributions included personal narratives about experiences with PF, descriptions of activities or behaviors found to be helpful with PF symptoms, resources or information about PF, and supportive comments to other PF sufferers., Conclusions: PF patients and their loved ones engage the Web 2.0 environment at these PF-focused sites to satisfy their needs to better understand PF and its impacts and to support others facing similar challenges. Clinicians may find it beneficial to encourage PF patients' involvement in internet forums that foster dynamic, bi-directional information sharing.

Idiopathic pulmonary fibrosis (IPF) is an untreatable diffuse parenchymal lung disease with a median survival of < 3 years. Pulmonary hypertension (PH) is frequently seen in patients with IPF and is commonly attributed to hypoxic vasoconstriction and capillary destruction. Pathology findings include endothelial proliferation and medial hypertrophy that exceed those expected in the setting of hypoxia. Noninvasive evaluation has limited sensitivity and specificity for the diagnosis of PH in IPF; therefore, right-heart catheterization remains the "gold standard" diagnostic test. PH in patients with IPF is associated with decreased exercise capacity and worse survival. Given the grave consequences of this condition, treatment of PH could improve functional outcomes and survival. However, possible treatments such as long-term supplemental oxygen and targeted vascular therapy are either unstudied or remain unproven.

Rationale: Functional studies may be useful to predict survival in idiopathic pulmonary fibrosis (IPF). Various cutoffs of 6-min-walk distance (6MWD) have been suggested to identify patients at a high risk of death., Objectives: To examine the association between 6MWD and survival in patients with IPF listed for lung transplantation, and to identify sensitive and specific cutoffs for predicting death at 6 mo., Methods: We performed a retrospective cohort study of 454 patients classified as having IPF listed for lung transplantation with the United Network for Organ Sharing between June 30, 2004 and July 22, 2005., Measurements and Main Results: Lower 6MWD was associated with an increased mortality rate (p value for linear trend < 0.0001). Patients with a walk distance less than 207 m had a more than fourfold greater mortality rate than those with a walk distance of 207 m or more, despite adjustment for demographics, anthropomorphics, FVC % predicted, pulmonary hypertension, and medical comorbidities (adjusted rate ratio, 4.7; 95% confidence interval, 2.5-8.9; p < 0.0001). 6MWD was a significantly better predictor of 6-mo mortality than was FVC % predicted (c-statistic = 0.73 vs. 0.59, respectively; p = 0.02)., Conclusions: Lower 6MWD was strongly and independently associated with an increased mortality rate for wait-listed patients classified as having IPF. 6MWD was a better predictor of death at 6 mo than was FVC % predicted.

Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by oculocutaneous albinism, a bleeding diathesis, and in a subset of patients, pulmonary fibrosis. Lung transplantation, the only curative therapy for pulmonary fibrosis, has not been previously reported as a successful treatment strategy for patients with HPS because the bleeding diathesis was thought to contraindicate major thoracic surgery. We successfully performed bilateral sequential lung transplantation in a patient with pulmonary fibrosis and HPS after transfusion of 6 units of platelets. Lung transplantation is a viable therapeutic option in patients with pulmonary fibrosis and only a mild bleeding diathesis associated with HPS.

Objective To assess predictors of subclinical RA-associated interstitial lung disease (RA-ILD) using quantitative lung densitometry (qLD). Methods RA patients underwent multi-detector row CT scanning at baseline and after an average of 39 months. Scans were analysed with qLD for the percentage of lung parenchyma with high attenuation areas (%HAA: the percentage of voxels of –600 to –250 Hounsfield units). Additionally, a pulmonary radiologist calculated an expert radiologist scoring (ERS) for RA-ILD features. Generalized linear models were used to identify indicators of baseline %HAA and predictors of %HAA change. Results Baseline %HAA was assessed in 193 RA patients and 106 had repeat qLD assessment. %HAA was correlated with ERS (Spearman's rho = 0.261; P  < 0.001). Significant indicators of high baseline %HAA (>10% of lung parenchyma with high attenuation) included female sex, higher pack-years of smoking, higher BMI and anti-CCP ≥200 units, collectively contributing an area under the receiver operator curve of 0.88 (95% CI 0.81, 0.95). Predictors of %HAA increase, occurring in 49% with repeat qLD, included higher baseline %HAA, presence of mucin 5B (MUC5B) minor allele and absence of HLA-DRB1 shared epitope (area under the receiver operator curve = 0.69; 95% CI 0.58, 0.79). The association of the MUC5B minor allele with %HAA change was higher among men and those with higher cumulative smoking. Within the group with increased %HAA, anti-CCP level was significantly associated with a greater increase in %HAA. Conclusions %HAA, assessed with qLD, was linked to several known risk factors for RA-ILD and may represent a more quantitative method to identify RA-ILD and track progression than expert radiologist interpretation. [ABSTRACT FROM AUTHOR]

Background and objective: Normative values for HAA—a quantitative, CT‐based measure of subclinical ILD—in healthy adults are needed to improve interpretability in clinical and research settings. Methods: HAA was measured on full‐lung CT in 3110 participants in the MESA study. Clinical prediction models were developed using a healthy never‐smoker subset with normal spirometry (n = 696). RMSE on cross‐validation was used as the primary criterion for model selection. Parametric and non‐parametric methods were considered. z‐Scores were calculated for the entire study sample. Associations between z‐scores and several ILD features were estimated. Results: In the healthy never‐smoker subset, the mean age was 69 years with a range of 54–93 years. The median HAA was 4.3% with a range of 2.7–17.8%. Linear regression had better predictive performance than other methods. The final model included race, height, weight, age and sex. The standard error of the estimate was 1.62 with a cross‐validated RMSE of 1.64 and an adjusted R2 of 0.139. z‐Scores were associated with several ILD outcomes in adjusted models, including ILA (OR: 1.40 per z‐unit; 95% CI: 1.30, 1.52), exertional dyspnoea (OR: 1.08 per z‐unit; 95% CI: 1.02, 1.15) and FVC (expected increase per z‐unit: −2.49; 95% CI: −2.95, − 2.03). Conclusion: We present a reference equation and z‐scores to define expected values of HAA on full‐lung CT to aid HAA interpretation in middle‐aged and older adults. To better understand the natural variation of HAA (a novel quantitative CT‐based measure of subclinical ILD), we developed HAA reference equations and z‐scores to define expected values of HAA with adjustment for key demographic and anthropometric variables, and we demonstrated that HAA z‐scores correlate with several ILD features. See relatedEditorial [ABSTRACT FROM AUTHOR]

To the Editor.--We read with pleasure Dr Leslie's thoughtful article describing a potential role for peripheral tractional lung injury in idiopathic pulmonary fibrosis (IPF). (1) Mechanical stretch is a well-known [...]

Background: This document provides clinical recommendations for the diagnosis of idiopathic pulmonary fibrosis (IPF). It represents a collaborative effort between the American Thoracic Society, European Respiratory Society, Japanese Respiratory Society, and Latin American Thoracic Society.Methods: The evidence syntheses were discussed and recommendations formulated by a multidisciplinary committee of IPF experts. The evidence was appraised and recommendations were formulated, written, and graded using the Grading of Recommendations, Assessment, Development, and Evaluation approach.Results: The guideline panel updated the diagnostic criteria for IPF. Previously defined patterns of usual interstitial pneumonia (UIP) were refined to patterns of UIP, probable UIP, indeterminate, and alternate diagnosis. For patients with newly detected interstitial lung disease (ILD) who have a high-resolution computed tomography scan pattern of probable UIP, indeterminate, or an alternative diagnosis, conditional recommendations were made for performing BAL and surgical lung biopsy; because of lack of evidence, no recommendation was made for or against performing transbronchial lung biopsy or lung cryobiopsy. In contrast, for patients with newly detected ILD who have a high-resolution computed tomography scan pattern of UIP, strong recommendations were made against performing surgical lung biopsy, transbronchial lung biopsy, and lung cryobiopsy, and a conditional recommendation was made against performing BAL. Additional recommendations included a conditional recommendation for multidisciplinary discussion and a strong recommendation against measurement of serum biomarkers for the sole purpose of distinguishing IPF from other ILDs.Conclusions: The guideline panel provided recommendations related to the diagnosis of IPF. [ABSTRACT FROM AUTHOR]

Rationale: The receptor for advanced glycation end products (RAGE) is underexpressed in idiopathic pulmonary fibrosis (IPF) lung, but the role of RAGE in human lung fibrosis remains uncertain.Objectives: To examine (1) the association between IPF risk and variation at rs2070600, a functional missense variant in AGER (the gene that codes for RAGE), and (2) the associations between plasma-soluble RAGE (sRAGE) levels with disease severity and time to death or lung transplant in IPF.Methods: We genotyped the rs2070600 single-nucleotide polymorphism in 108 adults with IPF and 324 race-/ethnicity-matched control subjects. We measured plasma sRAGE by ELISA in 103 adults with IPF. We used generalized linear and additive models as well as Cox models to control for potential confounders. We repeated our analyses in 168 (genetic analyses) and 177 (sRAGE analyses) adults with other forms of interstitial lung disease (ILD).Results: There was no association between rs2070600 variation among adults with IPF (P = 0.31). Plasma sRAGE levels were lower among adults with IPF and other forms of ILD than in control subjects (P < 0.001). The rs2070600 allele A was associated with a 49% lower sRAGE level (95% confidence interval [CI], 11 to 71%; P = 0.02) among adults with IPF. In adjusted analyses, lower sRAGE levels were associated with greater disease severity (14% sRAGE decrement per 10% FVC decrement; 95% CI, 5 to 22%) and a higher rate of death or lung transplant at 1 year (adjusted hazard ratio, 1.9 per logarithmic unit of sRAGE decrement; 95% CI, 1.2-3.3) in IPF. Similar findings were observed in a heterogeneous group of adults with other forms of ILD.Conclusions: Lower plasma sRAGE levels may be a biological measure of disease severity in IPF. Variation at the rs2070600 single-nucleotide polymorphism was not associated with IPF risk. [ABSTRACT FROM AUTHOR]

Acute exacerbation of idiopathic pulmonary fibrosis has been defined as an acute, clinically significant, respiratory deterioration of unidentifiable cause. The objective of this international working group report on acute exacerbation of idiopathic pulmonary fibrosis was to provide a comprehensive update on the topic. A literature review was conducted to identify all relevant English text publications and abstracts. Evidence-based updates on the epidemiology, etiology, risk factors, prognosis, and management of acute exacerbations of idiopathic pulmonary fibrosis are provided. Finally, to better reflect the current state of knowledge and improve the feasibility of future research into its etiology and treatment, the working group proposes a new conceptual framework for acute respiratory deterioration in idiopathic pulmonary fibrosis and a revised definition and diagnostic criteria for acute exacerbation of idiopathic pulmonary fibrosis. [ABSTRACT FROM AUTHOR]

Introduction: Primary graft dysfunction (PGD) is a significant contributor to early morbidity and mortality after lung transplantation. Increased vascular permeability in the allograft has been identified as a possible mechanism leading to PGD. Angiopoietin-2 serves as a partial antagonist to the Tie-2 receptor and induces increased endothelial permeability. We hypothesized that elevated Ang2 levels would be associated with development of PGD. Methods: We performed a case-control study, nested within the multi-center Lung Transplant Outcomes Group cohort. Plasma angiopoietin-2 levels were measured pre-transplant and 6 and 24 hours post-reperfusion. The primary outcome was development of grade 3 PGD in the first 72 hours. The association of angiopoietin-2 plasma levels and PGD was evaluated using generalized estimating equations (GEE). Results: There were 40 PGD subjects and 79 non-PGD subjects included for analysis. Twenty-four PGD subjects (40%) and 47 non-PGD subjects (59%) received a transplant for the diagnosis of idiopathic pulmonary fibrosis (IPF). Among all subjects, GEE modeling identified a significant change in angiopoietin-2 level over time in cases compared to controls (p = 0.03). The association between change in angiopoietin-2 level over the perioperative time period was most significant in patients with a pre-operative diagnosis of IPF (p = 0.02); there was no statistically significant correlation between angiopoietin-2 plasma levels and the development of PGD in the subset of patients transplanted for chronic obstructive pulmonary disease (COPD) (p = 0.9). Conclusions: Angiopoietin-2 levels were significantly associated with the development of PGD after lung transplantation. Further studies examining the regulation of endothelial cell permeability in the pathogenesis of PGD are indicated. [ABSTRACT FROM AUTHOR]

Rationale: Idiopathic pulmonary fibrosis is often initially misdiagnosed. Delays in accessing subspecialty care could lead to worse outcomes among those with idiopathic pulmonary fibrosis.Objectives: To examine the association between delayed access to subspecialty care and survival time in idiopathic pulmonary fibrosis.Methods: We performed a prospective cohort study of 129 adults who met American Thoracic Society criteria for idiopathic pulmonary fibrosis evaluated at a tertiary care center. Delay was defined as the time from the onset of dyspnea to the date of initial evaluation at a tertiary care center. We used competing risk survival methods to examine survival time and time to transplantation.Measurements and Main Results: The mean age was 63 years and 76% were men. The median delay was 2.2 years (interquartile range 1.0–3.8 yr), and the median follow-up time was 1.1 years. Age and lung function at the time of evaluation did not vary by delay. A longer delay was associated with an increased risk of death independent of age, sex, forced vital capacity, third-party payer, and educational attainment (adjusted hazard ratio per doubling of delay was 1.3, 95% confidence interval 1.03 to 1.6). Longer delay was not associated with a lower likelihood of undergoing lung transplantation.Conclusions: Delayed access to a tertiary care center is associated with a higher mortality rate in idiopathic pulmonary fibrosis independent of disease severity. Early referral to a specialty center should be considered for those with known or suspected interstitial lung disease. [ABSTRACT FROM AUTHOR]

The article evaluates the relationship between mean pulmonary artery pressure (mPAP) and primary graft dysfunction (PGD) among patients with idiopathic pulmonary fibrosis (IPF). The role of secondary pulmonary arterial hypertension (PAH) in mediating PGD risk in IPF patients is also explored. A multicenter prospective cohort study of 126 lung transplant procedures performed for IPF was conducted. It was found that higher mPAP in patients with IPF is associated with the development of PGD.

The article presents a study on the relationship between serum albumin concentration and waiting list mortality in patients with idiopathic interstitial pneumonia (IIP) for lung transplantation in the U.S. The study employed data from the United Network for Organ Sharing between January 1, 2004 and December 31, 2006. Researchers found that low serum albumin is significantly associated with poor survival in patients with IIP listed for lung transplantation.

Background--Right ventricular failure from increased pulmonary vascular loading is a major cause of morbidity and mortality, yet its modulation by disease remains poorly understood. We tested the hypotheses that, unlike the systemic circulation, pulmonary vascular resistance (RPA) and compliance (CPA) are consistently and inversely related regardless of age, pulmonary hypertension, or interstitial fibrosis and that this relation may be changed by elevated pulmonary capillary wedge pressure, augmenting right ventricular pulsatile load. Methods and Results--Several large clinical databases with right heart/pulmonary catheterization data were analyzed to determine the RPA-CPA relationship with pulmonary hypertension, pulmonary fibrosis, patient age, and varying pulmonary capillary wedge pressure. Patients with suspected or documented pulmonary hypertension (n= 1009) and normal pulmonary capillary wedge pressure displayed a consistent RPA-CPA hyperbolic (inverse) dependence, CPA=0.564/(0.047+RPA), with a near-constant resistance-compliance product (0.48±0.17 seconds). In the same patients, the systemic resistance-compliance product was highly variable. Severe pulmonary fibrosis (n=89) did not change the RPA-CPA relation. Increasing patient age led to a very small but statistically significant change in the relation. However, elevation of the pulmonary capillary wedge pressure (n=8142) had a larger impact, significantly lowering CPA for any RPA and negatively correlating with the resistance-compliance product (P<0.0001). Conclusions--Pulmonary hypertension and pulmonary fibrosis do not significantly change the hyperbolic dependence between RPA and CPA, and patient age has only minimal effects. This fixed relations, hip helps explain the difficulty of reducing total right ventricular afterload by therapies that have a modest impact on mean RPA. Higher pulmonary capillary wedge pressure appears to enhance net right ventricular afterload by elevating pulsatile, relative to resistive, load and may contribute to right ventricular dysfunction. [ABSTRACT FROM AUTHOR]