The Concavity of the Maximal Expiratory Flow-Volume Curve Reflects the Extent of Emphysema in Obstructive Lung Diseases

The Characteristics of the Concavity of Descending Limb of Maximal Expiratory Flow-Volume Curves Generated by Spirometry

PURPOSE

This study examined the concavity (angle β, central and peripheral concavity) of the descending limb of the maximal expiratory flow-volume (MEFV) curves to reflect various ventilatory defects, including obstructive, restrictive, or mixed patterns.

METHODS

We conducted a cross-sectional study collecting spirometry data from a healthcare center and a tertiary hospital between 2017 and 2022, with additional raw flow-volume curve data from primary healthcare institutions in 2023. We analyzed differences in concavity between spirometric patterns. Receiver operating characteristic curves were used to assess the predictive power of concavity for spirometric patterns. The relationship among concavity indices was examined.

RESULTS

This study included 18,938 cases, with 22% exhibiting an obstructive pattern. The dataset comprised 14,868 cases for training, 3716 cases for validation, and 354 cases for testing. In the training set, the mean angle β were 180.3 ± 12.4 and 148.5 ± 12.7 degrees in normal and obstruction patterns. The angle β had an AUC of 0.970 (95% CI 0.966-0.973) for identifying normal and obstructive patterns, with a cut-off value of 163.0 degrees. In the validation set, out of 2311 cases with a normal forced vital capacity (FVC), 3.1% cases exhibited a Z-score of forced expiratory volume in 1 s to FVC ratio (FEV1/FVC) ≥  - 1.645 but an angle β < 163.0 degrees. In testing set, a correlation coefficient of - 0.96 and - 0.79 was found between the angle β and the central or peripheral concavity.

CONCLUSION

The concavity of the descending limb of MEFV curves may be crucial in identifying spirometric patterns.

Curve-Modelling and Machine Learning for a Better COPD Diagnosis

Background

Development of new tools in artificial intelligence has an outstanding performance in the recognition of multidimensional patterns, which is why they have proven to be useful in the diagnosis of Chronic Obstructive Pulmonary Disease (COPD).

Methods

This was an observational analytical single-centre study in patients with spirometry performed in outpatient medical care. The segment that goes from the peak expiratory flow to the forced vital capacity was modelled with quadratic polynomials, the coefficients obtained were used to train and test neural networks in the task of classifying patients with COPD.

Results

A total of 695 patient records were included in the analysis. The COPD group was significantly older than the No COPD group. The pre-bronchodilator (Pre BD) and post-bronchodilator (Post BD) spirometric curves were modelled with a quadratic polynomial, and the coefficients obtained were used to feed three neural networks (Pre BD, Post BD and all coefficients). The best neural network was the one that used the post-bronchodilator coefficients, which has an input layer of 3 neurons and three hidden layers with sigmoid activation function and two neurons in the output layer with softmax activation function. This system had an accuracy of 92.9% accuracy, a sensitivity of 88.2% and a specificity of 94.3% when assessed using expert judgment as the reference test. It also showed better performance than the current gold standard, especially in specificity and negative predictive value.

Conclusion

Artificial Neural Networks fed with coefficients obtained from quadratic and cubic polynomials have interesting potential of emulating the clinical diagnostic process and can become an important aid in primary care to help diagnose COPD in an early stage.

The Challenges of Spirometric Diagnosis of COPD

Chronic obstructive pulmonary disease (COPD) is one of the top causes of morbidity and mortality worldwide. Although for many years its accurate diagnosis has been a focus of intense research, it is still challenging. Due to its simplicity, portability, and low cost, spirometry has been established as the main tool to detect this condition, but its flawed performance makes it an imperfect COPD diagnosis gold standard. This review aims to provide an up-to-date literature overview of recent studies regarding COPD diagnosis; we seek to identify their limitations and establish perspectives for spirometric diagnosis of COPD in the XXI century by combining deep clinical knowledge of the disease with advanced computer analysis techniques.

Systems Engineering Approach to Modeling and Analysis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterized by airflow limitation. This study develops a systems engineering framework for representing important mechanistic details of COPD in a model of the cardiorespiratory system. In this model, we present the cardiorespiratory system as an integrated biological control system responsible for regulating breathing. Four engineering control system components are considered: sensor, controller, actuator, and the process itself. Knowledge of human anatomy and physiology is used to develop appropriate mechanistic mathematical models for each component. Following a systematic analysis of the computational model, we identify three physiological parameters associated with reproducing clinical manifestations of COPD: changes in the forced expiratory volume, lung volumes, and pulmonary hypertension. We quantify the changes in these parameters (airway resistance, lung elastance, and pulmonary resistance) as the ones that result in a systemic response that is diagnostic of COPD. A multivariate analysis of the simulation results reveals that the changes in airway resistance have a broad impact on the human cardiorespiratory system and that the pulmonary circuit is stressed beyond normal under hypoxic environments in most COPD patients.

Principal component analysis of flow-volume curves in COPDGene to link spirometry with phenotypes of COPD

BACKGROUND

Parameters from maximal expiratory flow-volume curves (MEFVC) have been linked to CT-based parameters of COPD. However, the association between MEFVC shape and phenotypes like emphysema, small airways disease (SAD) and bronchial wall thickening (BWT) has not been investigated.

RESEARCH QUESTION

We analyzed if the shape of MEFVC can be linked to CT-determined emphysema, SAD and BWT in a large cohort of COPDGene participants.

STUDY DESIGN AND METHODS

In the COPDGene cohort, we used principal component analysis (PCA) to extract patterns from MEFVC shape and performed multiple linear regression to assess the association of these patterns with CT parameters over the COPD spectrum, in mild and moderate-severe COPD.

RESULTS

Over the entire spectrum, in mild and moderate-severe COPD, principal components of MEFVC were important predictors for the continuous CT parameters. Their contribution to the prediction of emphysema diminished when classical pulmonary function test parameters were added. For SAD, the components remained very strong predictors. The adjusted R² was higher in moderate-severe COPD, while in mild COPD, the adjusted R² for all CT outcomes was low; 0.28 for emphysema, 0.21 for SAD and 0.19 for BWT.

INTERPRETATION

The shape of the maximal expiratory flow-volume curve as analyzed with PCA is not an appropriate screening tool for early disease phenotypes identified by CT scan. However, it contributes to assessing emphysema and SAD in moderate-severe COPD.

Pulmonary function testing in COPD: looking beyond the curtain of FEV1

Chronic obstructive pulmonary disease (COPD) management remains challenging due to the high heterogeneity of clinical symptoms and the complex pathophysiological basis of the disease. Airflow limitation, diagnosed by spirometry, remains the cornerstone of the diagnosis. However, the calculation of the forced expiratory volume in the first second (FEV1) alone, has limitations in uncovering the underlying complexity of the disease. Incorporating additional pulmonary function tests (PFTs) in the everyday clinical evaluation of COPD patients, like resting volume, capacity and airway resistance measurements, diffusion capacity measurements, forced oscillation technique, field and cardiopulmonary exercise testing and muscle strength evaluation, may prove essential in tailoring medical management to meet the needs of such a heterogeneous patient population. We aimed to provide a comprehensive overview of the available PFTs, which can be incorporated into the primary care physician's practice to enhance the efficiency of COPD management.