Changes In Diffusing Capacity Research Articles

Diffusion capacity of single and interconnected networks

Understanding diffusive processes in networks is a significant challenge in complexity science. Networks possess a diffusive potential that depends on their topological configuration, but diffusion also relies on the process and initial conditions. This article presents Diffusion Capacity, a concept that measures a node’s potential to diffuse information based on a distance distribution that considers both geodesic and weighted shortest paths and dynamical features of the diffusion process. Diffusion Capacity thoroughly describes the role of individual nodes during a diffusion process and can identify structural modifications that may improve diffusion mechanisms. The article defines Diffusion Capacity for interconnected networks and introduces Relative Gain, which compares the performance of a node in a single structure versus an interconnected one. The method applies to a global climate network constructed from surface air temperature data, revealing a significant change in diffusion capacity around the year 2000, suggesting a loss of the planet’s diffusion capacity that could contribute to the emergence of more frequent climatic events.

Patient and Physician Assessments of Clinical Status: A Mixed-methods Study of Interstitial Lung Disease

The SARS-CoV-2 pandemic necessitated novel health care delivery for patients with interstitial lung disease (ILD), including reduced in-person appointments and physiologic testing to minimize transmission. Clinicians often have been required to rely on patients' subjective assessments of their clinical status during phone follow-up appointments. It is unknown how accurate a patient's self-assessment is compared with that of their physician during an in-person evaluation. Are patients' self-assessments of their clinical status in agreement with their physicians' assessments, and are telemedicine vsin-person visits acceptable? Patients were enrolled prospectively from the University of Calgary ILD clinic. Participants were asked by phone before the in-person appointment and after the appointment to rate their clinical status on a five-point Likert scale. Physicians then rated the patient's clinical status after the appointment on a similar five-point Likert scale, masked to patient responses. Patients and physicians were asked if an in-person appointment was necessary or if telemedicine would have sufficed. Clinical variables associated with physician assessments were assessed. Fifty patients with mean age of 67 ± 11.8 years participated. Mean time since last follow-up was 5.0 ± 3.0months. No correlation was found between the preclinical patient self-assessment and postclinical physician assessment (P= .18; κ= 0.28). Correlation of postclinical assessment was statistically significant (P< .001), with moderate agreement (κ= 0.49). Physicians thought telephone visits were acceptable for 58%of appointments, whereas only 12%of patients preferred telephone visits. Physician's assessment of clinical status seemed to be driven by change in diffusion capacity of the lungs for carbon monoxide (P= .039). Telemedicine may improve access to care for patients during pandemic management, in rural communities, and for those with impaired mobility. Despite these benefits, our data support that patients and physicians may not agree on determination of clinical status and that patients generally prefer in-person patient-physician interactions.

Treatment of primary sjögren's syndrome-related interstitial lung disease: a retrospective cohort study.

Background:Interstitial lung disease (ILD) is a common complication of primary Sjögren’s syndrome (pSS). Because there is a paucity of literature on the management of pSS-associated ILD (pSS-ILD), this retrospective cohort study assessed the efficacy of azathioprine and mycophenolate therapy in adult patients with pSS-ILD.Methods:A retrospective cohort study was performed using electronic health records to identify adults meeting the 2016 American College of Rheumatology/European League Against Rheumatism classification criteria for pSS. The presence of pSS-ILD was confirmed by characteristic high-resolution computed tomography and/or histopathology findings. Sociodemographic, clinical, and pulmonary function test (PFT) data were abstracted for patients meeting the criteria and followed longitudinally from the date of their ILD diagnosis. PFT values were anchored on time of treatment start, and linear mixed-effects modeling was used to analyze changes in diffusion capacity for carbon monoxide (DLCO) and forced vital capacity (FVC) before and after treatment initiation.Results:We identified 19 subjects who had pSS-ILD, of whom seven were treated with azathioprine and seven were treated with mycophenolate. Within the azathioprine treated group, FVC% slope change trended toward improvement from a rate of -9.8% per month pre-treatment to 2.1% per month post-treatment (p = 0.13). Within the mycophenolate treated group, FVC% slope change improved from a rate of 1.5% per month pre-treatment to 4.3% per month post-treatment (p = 0.02) and DLCO% slope changed from a rate of -3.8% to –1.3% per month (p = 0.01) after therapy start.Conclusions:Mycophenolate treatment was associated with significant improvement in PFTs of pSS-ILD patients over time, and azathioprine treatment followed a similar non-significanttrend. Additional prospective studies are needed to further evaluate these findings. (Sarcoidosis Vasc Diffuse Lung Dis 2020; 37 (2): 136-147)

Arterial Stiffness Increases Over Time in Relation to Lung Diffusion Capacity: A Longitudinal Observation Study in COPD.

BackgroundCardiovascular events are, after cancer, the most common cause of death in COPD patients. Arterial stiffness is an independent predictor of all-cause mortality and cardiovascular events. Several cross-sectional studies have confirmed increased arterial stiffness in patients with COPD. Various mechanisms in the development of arterial stiffness in COPD such as reduced lung function or systemic inflammation have been proposed. However, clinical predictors of arterial stiffness that had been reported in cross-sectional studies have not yet been confirmed in a longitudinal setting. We have assessed the course of augmentation index (AIx) - a measure of systemic arterial stiffness - and possible predictors in a cohort of COPD patients over a period of up to 7 years.MethodsCOPD patients underwent annual AIx measurement by applanation tonometry for a maximum duration of 7 years. Additionally, we performed annual assessments of lung function, blood gases, systemic inflammation, serum lipids and blood pressure. Associations between the course of AIx and potential predictors were investigated through a mixed effect model.ResultsSeventy-six patients (mean (SD) age 62.4 (7.1), male 67%) were included. The AIx showed a significant annual increase of 0.91% (95% CI 0.21/1.60) adjusted for baseline. The change in diffusion capacity (DLco), low-density lipoprotein (LDL), and high-sensitivity c-reactive protein (hsCRP) was independently associated with the increasing evolution of AIx (Coef. - 0.10, p<0.001, Coef. 1.37, p=0.003, and Coef. 0.07, p=0.033, respectively).ConclusionThis study demonstrated a meaningful increase in arterial stiffness in COPD over time. A greater annual increase in arterial stiffness was associated with the severity of emphysema (measured by DLco), systemic inflammation, and dyslipidaemia.Clinical Trial Registrationwww.ClinicalTrials.gov, NCT01527773.

Impact of Azathioprine use in chronic hypersensitivity pneumonitis patients

IntroductionSystemic corticosteroids are widely used in chronic hypersensitivity pneumonitis (CHP); however, there is not much evidence to support their use, besides being associated with significant side effects. Azathioprine (AZA) use is common in CHP, although not prospectively tested in randomized controlled trials. Our objective was to evaluate the lung function trajectory of CHP patients after AZA initiation, as well as to assess the safety profile of this drug. MethodsRetrospective analysis of patients initiated on AZA following a multidisciplinary team diagnosis of CHP. The longitudinal trajectory of lung function in the first 2 years of treatment was assessed. ResultsThirty-five out of 62 patients (56.5%) remained on treatment after 2 years. AZA treatment was associated with a significant improvement in forced vital capacity (FVC) at 12 and 24 months (p = 0.015 and p < 0.001, respectively). A slight increase in total lung capacity (TLC) and 6-min walking test (6MWT) were also reported, although it did not reach statistical differences at the end of 2 years. No changes in diffusion capacity for carbon monoxide (DLCO) were observed. ConclusionsThis is the first study identifying an improvement in lung function (FVC) of CHP patients on AZA treatment for 2 years. Prospective studies are needed to confirm these results and to more adequately select CHP patients who may benefit from AZA.

Change in pulmonary diffusion capacity in a general population sample over 9 years

RationaleData on the change in diffusion capacity of the lung for carbon monoxide (DLCO) over time are limited. We aimed to examine change in DLCO (ΔDLCO) over a 9-year period and its predictors.MethodsA Norwegian community sample comprising 1,152 subjects aged 18–73 years was examined in 1987 and 1988. Of the 1,109 subjects still alive, 830 (75%) were re-examined in 1996/97. DLCO was measured with the single breath-holding technique. Covariables recorded at baseline included sex, age, height, weight, smoking status, pack years, occupational exposure, educational level, and spirometry. Generalized estimating equations analyses were performed to examine relations between ΔDLCO and the covariables.ResultsAt baseline, mean [standard deviation (SD)] DLCO was 10.8 (2.4) and 7.8 (1.6) mmol·min−1·kPa−1 in men and women, respectively. Mean (SD) ΔDLCO was −0.24 (1.31) mmol·min−1·kPa−1. ΔDLCO was negatively related to baseline age, DLCO, current smoking, and pack years, and positively related to forced expiratory volume in 1 second (FEV1) and weight. Sex, occupational exposure, and educational level were not related to ΔDLCO.ConclusionsIn a community sample, more rapid decline in DLCO during 9 years of observation time was related to higher age, baseline current smoking, more pack years, larger weight, and lower FEV1.

The Pore Size Distribution of Naturally Porous Cigarette Paper and its Relation to Permeability and Diffusion Capacity

Summary The pore size distribution of cigarette paper determines its air permeability and diffusion capacity and thereby has a significant influence on the gas exchange of a cigarette through the cigarette paper during smoking and during smouldering. For the design of cigarettes and in particular of cigarette papers it is important to understand how the pore size distribution of the cigarette paper is affected by the paper composition and paper properties and how it influences air permeability and diffusion capacity. It was the aim of this study to investigate how the composition of the cigarette paper such as filler content, fibre type and burn additive content qualitatively influenced the pore size distribution and how the pore size distribution and, in particular, which pore size range is correlated with air permeability and diffusion capacity, respectively. To this end eight naturally porous cigarette papers were selected which differed in air permeability, diffusion capacity, fibre type, filler content and burn additive content. The pore size distributions of these papers were measured by mercury porosimetry before and after the papers had been heated to 230 °C for 30 min. The pore size distributions were investigated for qualitative differences when air permeability, fibre type and filler content of the cigarette paper are modified. Furthermore by appropriate weighting of the pore size distributions optimal correlations between a weighted pore volume and air permeability or diffusion capacity were determined. The results show a good correlation with correlation coefficients greater than 0.9 for air permeability as well as for diffusion capacity. The results indicate that large pores are better correlated with changes in air permeability, while small pores are more strongly correlated with changes in diffusion capacity and support previous theoretical results obtained from flow and diffusion models. They also demonstrate the tight relationship between pore size distribution, air permeability and diffusion capacity, which makes the pore size distribution a tool to further optimize cigarette papers, for example, with respect to carbon monoxide yields in the smoke of a cigarette. [Beitr. Tabakforsch. Int 26 (2015) 312-319]

Oral Sildenafil has No Acute Effect on Diffusion Capacity Measurements in Patients with Diffuse Parenchymal Lung Disease and Pulmonary Hypertension

Diffuse parenchymal lung diseases have diverse etiology and treatment often requires individualization taking into consideration comorbidities. Pulmonary hypertension represents one such comorbidity which, when present, worsens prognosis and confounds approach to treatment. Sildenafil is a pulmonary vasodilator, which has recently generated considerable interest for use in patients with diffuse parenchymal lung disease and concomitant pulmonary hypertension. We wondered whether acute administration of oral sildenafil affects the diffusion capacity measurement, which is a tool for serially monitoring patients with diffuse parenchymal lung diseases. Methods: 15 patients with diffuse parenchymal lung disease and pulmonary hypertension (WHO Class III) had diffusion capacity measurements and 6 minute walk test performed before and after receiving sildenafil 20 mg orally. CT scans of the chest were scored to determine burden of interstitial lung disease. Results: The mean change in DLCO after administration of oral sildenafil was -0.26 ± 0.94 ml/min/mmHg (p=0.30) and -0.41 ± 2.84 % predicted (p=0.58). The average 6 minute walk distance at baseline was 363.28 ± 141 meters. After oral administration of sildenafil, 6 minute walk distance was 369 ± 116 meters (p=0.63). No correlation was observed between composite radiology scores and DLCO measurements or change in DLCO and radiology scores (p=0.43 and p=0.17 respectively). Conclusion: We found no acute change in diffusion capacity after a single dose of oral sildenafil in patients with diffuse parenchymal lung disease and pulmonary hypertension.

Impact of gender, age, and chemotherapy on lung diffusion capacity in patients receiving thoracic radiation

The hallmark of radiation lung injury is the decline in diffusion capacity of the lung. This is attributed to radiation injury to the pulmonary vasculature resulting in deficiency in gas exchange. The diffusion capacity is a part of the Pulmonary Function Test (PFT) as measured by the diffusion of carbon monoxide (DLCO). It is reported as either uncorrected DLCO or corrected DLCO (adjusted for individual hemoglobin levels). To determine whether the correction is essential to the interpretation of radiation pulmonary injury and to better characterize other clinical factors that may affect radiation lung injury, we investigated the longitudinal changes in DLCO with and without correction. We propose that gender, age, and chemotherapy status may impact the changes in diffusion capacity in patients who received radiotherapy (RT) to the chest. In a prospective clinical protocol for radiation lung injury, patients who received thoracic irradiation with or without chemotherapy for malignancy in the chest had serial PFTs performed at our institution from 1996 to 2001. Measurements of corrected and uncorrected DLCO were taken both prior to thoracic irradiation and approximately 1, 3, 6, 9, 12, 15, and 18 months after completion of radiotherapy. Thirty-six patients had PFTs both pre and post RT. We used a one-tailed paired t-test to compare the pre and post RT data at the various time points. The data was stratified in regards to gender, age, and chemotherapy status. A one tailed student t-test test was used to test significance of these groups. Both corrected and uncorrected DLCO continued to decline significantly after completion of RT for all patients. It reached a nadir at 9 months (75s81%, respectively) post RT, but only the corrected DLCO showed a significant (p = .05) recovery to 84% from this nadir at 15 months post RT. Patients who had chemotherapy along with RT had a decline in their absolute and relative changes in DLCO (both corrected and uncorrected for hemoglobin). For those with RT only, there is a recovery of DLCO only in corrected DLCO, but not in the uncorrected DLCO. Male patients’ corrected and uncorrected DLCOs leveled off after the initial decline at 1 month, while female patients’ DLCOs continued on a steady decline after the initial decline at 1 month. Both corrected and uncorrected DLCO showed a statistically significant recovery at 15 months for female patients only. Although both younger (40–64 yo) and older (65–86 yo) patients experienced their nadir (70s80%, respectively) of corrected DLCO at 9 months, older patients didn’t experience any recovery of their DLCO (corrected and uncorrected), while the younger patients experienced a statistically significant recovery of their DLCO. Both radiation alone and in combination with chemotherapy caused an immediate decline in DLCO (corrected or uncorrected) starting within one month after RT with a nadir at 9 months. This was seen in all patient populations studied, irrespective of their gender, age, and chemotherapy status. Gender, age, and chemotherapy status influence kinetics of recovery of DLCO after nadir. We are in the process of assessing the impact of other clinical factors (smoking, RT dose, RT volume, etc.) on the changes of diffusion capacity post RT. Corrected DLCO and uncorrected DLCO showed different kinetics in some but not all of the variables in this study. Because corrected DLCO more accurately reflects gas exchange function, we recommend using corrected DLCO as a measurable endpoint for radiation pneumopathy. It may also allow for standardized comparison of data among different institutions

Pulmonary Diffusion Abnormalities in Heart Transplant Recipients: Relationship to Cytomegalovirus Infection

Lung function of patients with heart failure is characterized by a variety of changes proposed as being due to passive congestion, secondary pulmonary fibrosis, and/or recurrent pulmonary emboli. A diffusion impairment thought to be due to cyclosporine has also been noted in patients following heart transplantation. Similar changes of unclear origin have been observed in renal transplant recipients. The objective of this study was to determine the extent to which lung function changes are reversible by cardiac transplantation and relate changes to the status of the recipients lung in the presence of possible vascular, iatrogenic, immune, or infectious injury. We analyzed the data of 22 patients who underwent lung function testing before and after heart transplantation and correlated changes to hemodynamic change, episodes of rejection, concentration of cyclosporine, and cytomegalovirus infection. Despite excellent graft function, the carbon monoxide transfer factor deteriorated to a mean of 57 percent of predicted postoperatively. The fall in diffusion factor did not correlate with episodes of cardiac rejection, cyclosporine levels, or hemodynamic status. In those patients who had serologic evidence of cytomegalovirus infection, the reduction in transfer factor was greater compared to those without infection despite a normal chest radiograph. The effects of cardiopulmonary bypass were unlikely to have been responsible for the abnormalities as lung function was assessed at a mean of 14 months after surgery. In heart transplant recipients, a change in diffusion capacity may represent an additional marker for cytomegalovirus infection and reflect infectious/immune injury late following surgery.

Changes in diffusing capacity after bronchography.

Changes in diffusing capacity after bronchography.