Retrospective study of pulmonary function tests in patients presenting with isolated reduction in single-breath diffusion capacity: implications for the diagnosis of combined obstructive and restrictive lung disease

Measuring lung diffusing capacity: an opportunity for improved medical surveillance and disability evaluation of coal miners

OBJECTIVES

Spirometry is the primary lung function test utilised for medical surveillance and disability examination for coal mine dust lung disease. However, spirometry likely underestimates physiologic impairment. We sought to characterise abnormalities of single-breath diffusing capacity for carbon monoxide (DLCO) among a population of former coal miners.

METHODS

Data from 3115 former coal miners evaluated at a West Virginia black lung clinic between 2006 and 2015 were retrospectively analysed to study the association between diffusion impairment (abnormally low DLCO), resting spirometry and the presence and severity of coal workers' pneumoconiosis on chest radiography. We developed ordinary least squares linear regression models to evaluate factors associated with per cent predicted DLCO (DLCOpp).

RESULTS

Diffusion impairment was identified in 20.2% of subjects. Ten per cent of all miners with normal spirometry had diffusion impairment including 7.4% of never smokers. The prevalence of diffusion impairment increased with worsening radiographic category of pneumoconiosis. Mean DLCOpp decreased with increasing small opacity profusion subcategory in miners without progressive massive fibrosis. Linear regression analysis also showed significant decreases in DLCOpp with increasing small opacity profusion and presence of large opacities.

CONCLUSIONS

Diffusion impairment is common among former coal miners, including among never smokers, miners without radiographic pneumoconiosis and miners with normal spirometry. These findings demonstrate the value of including DLCO testing in disability examinations of former coal miners and an important role for its use in medical surveillance of working miners to detect early chronic lung disease.

Effect size of rituximab on pulmonary function in the treatment of connective-tissue disease-related interstitial lung disease: a systematic review and meta-analysis

Background

Rituximab (RTX) has been previously reported as directed treatment in patients with connective-tissue disease-related interstitial lung diseases (CTD-ILD). A systematic assessment of treatment effect size on pulmonary function outcomes and related adverse effects in patients with CTD-ILD has not been previously reported.

Methods

We performed a systematic review and meta-analysis of published reports from PubMed, Embase, and Cochrane Libraries. Randomized and non-randomized controlled trials, case–control, cohort, and case series (with five or more cases) containing individual pulmonary function data and adverse effects were included. Study endpoints were pre- and post-treatment change in percent predicted forced vital capacity (FVC %) and diffusion capacity for carbon monoxide (DLCO%), along with reported drug-related adverse events.

Results

Twenty studies totaling 411 patients were identified with 14 included in the meta-analysis of pulmonary function and six in the descriptive review. Random effects meta-analysis of pre- and post-treatment pulmonary function findings demonstrated increases in FVC% (n = 296) (mean difference (MD) 4.57%, [95% CI 2.63–6.51]) and DLCO% (n = 246) (MD 5.0% [95% CI 2.71–7.29]) after RTX treatment. RTX treatment-related adverse effects were reported in 13.6% of the pooled cohort.

Conclusions

A systematic assessment of post-treatment effect size suggests a potential role for RTX in stabilizing or improving lung function in patients with CTD-ILD, with a modest but not insignificant adverse effect profile.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02082-x.

Effects of adopting the Global Lung Function Initiative 2017 reference equations on the interpretation of carbon monoxide transfer factor

The recently published Global Lung Function Initiative (GLI) carbon monoxide transfer factor (T _LCO) reference equations provide an opportunity to adopt a current, all-age, widely applicable reference set. The aim of this study was to document the effect of changing to GLI from commonly utilised reference equations on the interpretation of T _LCO results.33 863 T _LCO results (48% female, 88% Caucasian, n=930 aged <18 years) from clinical pulmonary function laboratories within three Australian teaching hospitals were analysed. The lower limit of normal (LLN) and proportion of patients with a T _LCO below this value were calculated using GLI and other commonly used reference equations.The average T _LCO LLN for GLI was similar or lower than the other equations, with the largest difference seen for Crapo equations (median: -1.25, IQR: -1.64, -0.86 mmol·min^-1·kPa^-1). These differences resulted in altered rates of reduced T _LCO for GLI particularly for adults (+1.9% versus Miller to -27.6% versus Crapo), more so than for children (-0.8% versus Kim to -14.2% versus Cotes). For adults, the highest raw agreement for GLI was with Miller equations (94.7%), while for children it was with Kim equations (98.1%). Results were reclassified from abnormal to normal more frequently for younger adults, and for adult females, particularly when moving from Roca to GLI equations (30% of females versus 16% of males).The adoption of GLI T _LCO reference equations in adults will result in altered interpretation depending on the equations previously used and to a greater extent in adult females. The effect on interpretation in children is less significant.

Comorbidities in idiopathic pulmonary fibrosis patients: a systematic literature review

Idiopathic pulmonary fibrosis (IPF) is associated with a fatal prognosis and manifests in patients over 60 years old who may have comorbidities. The prevalence and impact of comorbidities on the clinical course of IPF is unclear.

This systematic literature review examined the prevalence of comorbidities and mortality associated with comorbidities in IPF patients. Relevant observational studies published in English from January 1990 to January 2015 identifiedviaMEDLINE and EMBASE were included; bibliographies of articles were also searched.

Among the 126 studies included, prevalence of pulmonary hypertension (PH) was 3–86%, 6–91% for obstructive sleep apnoea, 3–48% for lung cancer and 6–67% for chronic obstructive pulmonary disease (COPD). Nonrespiratory comorbidities included ischaemic heart disease (IHD) (3–68%) and gastro-oesophageal reflux (GER) (0–94%). Mortality was highest among patients with IPF and lung cancer. Most studies assessed relatively small samples of patients with IPF.

PH, COPD, lung cancer, GER and IHD are significant comorbidities; differences in IPF severity, case definitions and patient characteristics limited the comparability of findings. The identification and prompt treatment of comorbidities may have a clinically significant impact on overall outcome that is meaningful for patients with IPF.

Smoking-Related "Interstitial" Lung Disease

CONTEXT

Emphysema, respiratory bronchiolitis, desquamative interstitial pneumonia, pulmonary Langerhans' cell histiocytosis, small-airway injury including submucosal and adventitial fibrosis, increased bronchus-associated lymphoid tissue, and small artery/arteriolar wall thickening are recognized histologic findings in cigarette smokers. It has only recently been acknowledged that the range of lung injury from cigarette smoke is wider than generally accepted, in particular, there is increasing recognition that fibrosis of alveolar walls occurs in smokers.

OBJECTIVES

To review the literature that describes the range of histologic findings in cigarette smokers and that links cigarette smoke exposure to the development of alveolar wall fibrosis.

DATA SOURCES

Relevant peer-reviewed literature indexed in PubMed (National Library of Medicine) form the basis of this review.

CONCLUSIONS

Smokers demonstrate a wide range of lung injury at biopsy that defies simple placement within single categories, and the current categories do not adequately take into account the importance of alveolar wall and airway fibrosis.

Current clinical management of pulmonary arterial hypertension

During the past 2 decades, there has been a tremendous evolution in the evaluation and care of patients with pulmonary arterial hypertension (PAH). The introduction of targeted PAH therapy consisting of prostacyclin and its analogs, endothelin antagonists, phosphodiesterase-5 inhibitors, and now a soluble guanylate cyclase activator have increased therapeutic options and potentially reduced morbidity and mortality; yet, none of the current therapies have been curative. Current clinical management of PAH has become more complex given the focus on early diagnosis, an increased number of available therapeutics within each mechanistic class, and the emergence of clinically challenging scenarios such as perioperative care. Efforts to standardize the clinical care of patients with PAH have led to the formation of multidisciplinary PAH tertiary care programs that strive to offer medical care based on peer-reviewed evidence-based, and expert consensus guidelines. Furthermore, these tertiary PAH centers often support clinical and basic science research programs to gain novel insights into the pathogenesis of PAH with the goal to improve the clinical management of this devastating disease. In this article, we discuss the clinical approach and management of PAH from the perspective of a single US-based academic institution. We provide an overview of currently available clinical guidelines and offer some insight into how we approach current controversies in clinical management of certain patient subsets. We conclude with an overview of our program structure and a perspective on research and the role of a tertiary PAH center in contributing new knowledge to the field.

Idiopathic pulmonary fibrosis: early detection and referral

Idiopathic pulmonary fibrosis (IPF), a devastating progressive interstitial lung disease (ILD) with no known cause or cure, is the most common and deadly of the idiopathic interstitial pneumonias. With a median survival of 3-5 years following diagnosis, IPF is characterized by a progressive decline in lung function and quality of life in most patients. Vigilance among clinicians in recognizing IPF early in the disease course remains critical to properly caring for these patients, as this provides the widest range of management options. When IPF is suspected, a multidisciplinary evaluation (MDE) by a clinician, radiologist and pathologist with ILD expertise should occur, as this improves diagnostic agreement in both community and academic settings. When community MDE is not possible, or diagnostic doubt exists, referral to an ILD center should be considered. ILD center referral may also provide access specialized care, including clinical trials and lung transplantation, and should be considered for any patient with an established diagnosis of IPF.

Interstitial lung disease in inflammatory myopathies: clinical phenotypes and prognosis

Interstitial lung disease (ILD) is a very important complication of the idiopathic inflammatory myositides (IIM), with a prevalence of approximately 40 %. Characteristic HRCT changes, most commonly NSIP, together with a restrictive ventilatory defect and an associated decline in DLco support the presence of ILD. The strongest risk factors are the presence of the anti-amino-acyl-tRNA synthetases (ARS) and anti-MDA-5 antibodies, but a raised index of suspicion for ILD should also apply to IIM patients of black ethnicity. Overall, the prognosis of ILD in IIM is good; between 50 and 66 % of cases have a stable disease course over a substantial period of time. The remaining proportion will show signs of worsening lung disease within 12 months of diagnosis. Whereas ARS antibodies and black ethnicity have no influence on ILD prognosis, detection of the anti-MDA-5 antibody carries a poor ILD outcome, in which hyperferritinaemia appears to be an important diagnostic and prognostic feature.

Normal expiratory flow rate and lung volumes in patients with combined emphysema and interstitial lung disease: a case series and literature review

Pulmonary function tests in patients with idiopathic pulmonary fibrosis characteristically show a restrictive pattern including small lung volumes and increased expiratory flow rates resulting from a reduction in pulmonary compliance due to diffuse fibrosis. Conversely, an obstructive pattern with hyperinflation results in emphysema by loss of elastic recoil, expiratory collapse of the peripheral airways and air trapping. When the diseases coexist, pulmonary volumes are compensated, and a smaller than expected reduction or even normal lung volumes can be found. The present report describes 10 patients with progressive breathlessness, three of whom experienced severe limitation in their quality of life. All patients showed lung interstitial involvement and emphysema on computed tomography scan of the chest. The 10 patients showed normal spirometry and lung volumes with severe compromise of gas exchange. Normal lung volumes do not exclude diagnosis of idiopathic pulmonary fibrosis in patients with concomitant emphysema. The relatively preserved lung volumes may underestimate the severity of idiopathic pulmonary fibrosis and attenuate its effects on lung function parameters.

Combined pulmonary fibrosis and emphysema syndrome: a review

There is increasing clinical, radiologic, and pathologic recognition of the coexistence of emphysema and pulmonary fibrosis in the same patient, resulting in a clinical syndrome known as combined pulmonary fibrosis and emphysema (CPFE) that is characterized by dyspnea, upper-lobe emphysema, lower-lobe fibrosis, and abnormalities of gas exchange. This syndrome frequently is complicated by pulmonary hypertension, acute lung injury, and lung cancer. The CPFE syndrome typically occurs in male smokers, and the mortality associated with this condition, especially if pulmonary hypertension is present, is significant. In this review, we explore the current state of the literature and discuss etiologic factors and clinical characteristics of the CPFE syndrome.

Combined Pulmonary Fibrosis and Emphysema Syndrome: A New Phenotype within the Spectrum of Smoking-Related Interstitial Lung Disease

Combined pulmonary fibrosis and emphysema (CPFE) is a recently defined syndrome, in which centrilobular and/or paraseptal emphysemas in upper lung zones coexist with pulmonary fibrosis in lower lobes in individuals. These patients have a characteristic lung function profile, with unexpected subnormal dynamic and static lung volumes, contrasting with a significant reduction of carbon monoxide transfer (DL_co) and exercise hypoxemia. Pulmonary hypertension is highly prevalent in CPFE and is the leading determinant of death. Tobacco smoking has been proposed as the main factor in its etiology, though the pathophysiology and its natural history remain to be determined. High-resolution computed axial tomography is the mandatory tool to confirm the diagnosis. Currently, there is no consensus about its treatment since those published to date on this issue are limited to well-characterised series of cases; hence, a better understanding of this entity may help in the development of future therapeutic approaches.

Pulmonary hypertension in idiopathic pulmonary fibrosis: a review

Idiopathic pulmonary fibrosis (IPF) is a progressive diffuse parenchymal disease with a poor prognosis. Pulmonary hypertension (PH) often complicates the course of IPF and may even be found in patients with preserved lung function. Possible pathogenetic mechanisms of PH in IPF include vascular destruction, pulmonary hypoxic vasoconstriction and vascular remodeling due to overexpression of cytokines and growth factors. PH in IPF patients is associated with decreased exercise capacity and a worse prognosis. Due to its prognostic significance, it seems important to investigate for PH in these patients. As the symptoms of PH in IPF are nonspecific, the development of PH in a patient with known IPF can be easily overlooked. Noninvasive methods provide clues for the diagnosis, but their sensitivity is limited. Doppler echocardiography is a useful tool for the detection of PH which also provides additional information regarding associated cardiac abnormalities. However, right heart catheterization remains the gold standard diagnostic test. Therapeutic options for PH in IPF are limited. Long-term oxygen administration for the correction of hypoxemia should be recommended. The availability of new pharmacological agents in the treatment of PH has raised the possibility of therapy in patients with IPF and associated PH. Whether these PH-targeted therapies may be of benefit in this patient group, in terms of improving functional outcomes and survival, remains uncertain.

Rheumatoid arthritis-associated interstitial lung disease: diagnostic dilemma

Interstitial lung disease (ILD) is an increasingly recognized complication of rheumatoid arthritis (RA) contributing to significantly increased morbidity and mortality. Diagnosis can be challenging since patients are unlikely to report dyspnea due to an overall decrease in physical activity with advanced arthritic symptoms. Additionally, infections, drug toxicity, and environmental toxins can mimic ILD, creating significant diagnostic dilemmas for the clinician. In this paper we will explore an effective clinical algorithm for the diagnosis of RA-ILD. We will also discuss features of drug-related toxicities, infections, and environmental toxins that comprise the main entities in the differential diagnosis of RA-ILD. Finally, we will explore the known and experimental treatment options that may have some benefit in the treatment of RA-ILD.

[Combined pulmonary fibrosis and emphysema]

The combination of pulmonary fibrosis and emphysema (CPFE) is a recently defined syndrome, in which an upper lobe emphysema and lower lobe fibrosis coexist in a single patient. These patients have a characteristic lung function profile, with dynamic and static lung volumes apparently normal or minimally altered, contrasting with a significant reduction of carbon monoxide transfer (DLco) and exercise hypoxemia. Pulmonary hypertension is highly prevalent and is the principal negative prognostic factor for this condition. High resolution computed axial tomography (HRCT) is the main tool to confirm the diagnosis. Cigarette smoking has been proposed as the main factor in its etiology; however, neither pathogenic mechanisms nor the sequence of events involved in this syndrome has been clarified yet. Experimental studies in animal models are providing information on the involvement of some inflammatory mediators in the pathogenesis. There is currently no consensus on the therapeutic approach to be followed in these patients, since those published to date on this subject are limited to well-characterised series of cases. Therefore, it is a pathology with many unknowns yet to be resolved and highly likely to be underdiagnosed, unless its functional clinical characteristics are taken into account.

Prediction of pulmonary hypertension in idiopathic pulmonary fibrosis

BACKGROUND

Reliable, noninvasive approaches to the diagnosis of pulmonary hypertension in idiopathic pulmonary fibrosis are needed. We tested the hypothesis that the forced vital capacity to diffusing capacity ratio and room air resting pulse oximetry may be combined to predict mean pulmonary artery pressure (MPAP) in idiopathic pulmonary fibrosis.

METHODS

Sixty-one idiopathic pulmonary fibrosis patients with available right-heart catheterization were studied. We regressed measured MPAP as a continuous variable on pulse oximetry (SpO(2)) and percent predicted forced vital capacity (FVC) to percent-predicted diffusing capacity ratio (% FVC/% DL(co)) in a multivariable linear regression model.

RESULTS

Linear regression generated the following equation: MPAP=-11.9+0.272 x SpO(2)+0.0659 x (100-SpO(2))(2)+3.06 x (% FVC/% DL(co)); adjusted R(2)=0.55, p<0.0001. The sensitivity, specificity, positive predictive and negative predictive value of model-predicted pulmonary hypertension were 71% (95% confidence interval (CI): 50-89%), 81% (95% CI: 68-92%), 71% (95% CI: 51-87%) and 81% (95% CI: 68-94%).

CONCLUSIONS

A pulmonary hypertension predictor based on room air resting pulse oximetry and FVC to diffusing capacity ratio has a relatively high negative predictive value. However, this model will require external validation before it can be used in clinical practice.