Evaluation of small airway function and its application in patients with chronic obstructive pulmonary disease (Review)

Evaluating the clinical utility of small airway function assessment for early diagnosis of GOLD stage 0 chronic obstructive pulmonary disease

OBJECTIVE

To investigate the clinical utility of small airway function indices for early identification of GOLD stage 0 chronic obstructive pulmonary disease (COPD).

METHODS

This retrospective study enrolled 137 participants at our institution between January 2017 and December 2018, comprising 40 healthy controls, 46 individuals with GOLD stage 0 COPD, and 51 patients with established COPD. Pulmonary function was assessed using the PowerCube spirometry system (GANSHORN, Germany). Parameters evaluated included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, and small airway function indicators.

RESULTS

The COPD cohort exhibited significantly lower values across all lung function measures compared to the other two groups, particularly for dynamic lung volume parameters such as FEV1%predicted and FEV1/FVC%. Small airway function indices, including FEV3%predicted, FEF75%predicted, FEF50%predicted, FEF25%predicted, and MMEF%predicted, were markedly decreased in the COPD group (all p-values <0.001). Receiver operating characteristic (ROC) curve analysis demonstrated that MMEF/FVC% and FEV3/FVC% had high diagnostic accuracy for COPD, with MMEF/FVC% exhibiting the optimal sensitivity and specificity.

CONCLUSION

Small airway function indices, especially MMEF/FVC%, can serve as effective tools for early identification of GOLD stage 0 COPD. Incorporation of these findings into clinical practice may facilitate early diagnosis and intervention, thereby improving treatment outcomes and patient quality of life.

Impulse Oscillometry as an Alternative Lung Function Test for Hospitalized Adults

BACKGROUND

Impulse oscillometry (IOS) is a noninvasive technique that measures lung physiology independently of patient effort. In the present study, we aimed to investigate the utility of IOS parameters in comparison with pulmonary function testing (PFT) among hospitalized subjects, with emphasis on obstructive and small airway diseases.

METHODS

Sixty-one subjects hospitalized either with unexplained dyspnea or for pre-surgery evaluation were included in the study. All subjects underwent PFTs and IOS test. The correlation between IOS results and PFTs was examined in different subgroups. The ability of IOS parameters to predict abnormal PFTs was evaluated using the area under the receiver operating characteristic (ROC) curve, and optimal cutoff values were calculated.

RESULTS

IOS results were found to correlate with PFT values. Subgroup analysis revealed that these correlations were higher in younger (age < 70) and non-obese (body mass index < 25kg/m2) subjects. The resonant frequency was an independent predictor and had the best predictive ability for abnormal FEV1/FVC (area under the ROC curve 0.732 [95% CI 0.57-0.90], optimal cutoff 17 Hz, 87% sensitivity, 62% specificity) and abnormal forced expiratory flow during the middle half of the FVC maneuver (area under the ROC curve 0.667 [95% CI 0.53-0.81], optimal cutoff 15 Hz, 77% sensitivity, 54% specificity). Area of reactance and the difference in respiratory resistance at 5 Hz and 20 Hz also showed a good predictive ability for abnormal FEV1/FVC (area under the ROC curve 0.716 and 0.730, respectively).

CONCLUSIONS

We found that the IOS performed well in diagnosing small airway and obstructive diseases among hospitalized subjects. IOS might serve as an alternative to standard PFTs in non-cooperative or dyspneic hospitalized patients.

Potential pre-COPD indicators in association with COPD development and COPD prediction models in Chinese: a prospective cohort study

Background

Lung injury might take place before chronic obstructive pulmonary disease (COPD) occurs. A clearer definition of "pre-COPD" based on the effects of potential indicators on increasing risk of COPD development and a prediction model involving them are lacking.

Methods

A total of 3526 Chinese residents without COPD aged 40 years or older derived from the national cross-sectional survey of COPD surveillance in 2014-2015 were followed up for a mean of 3.59 years. We examined the associations of chronic bronchitis, preserved ratio impaired spirometry (PRISm), low peak expiratory flow (PEF), spirometric small airway dysfunction (sSAD), low maximal mid-expiratory flow (MMEF), low forced expiratory flow 50% of pulmonary volume (FEF50), and low FEF75 with subsequent COPD and constructed a prediction model with LASSO-Cox regression.

Findings

235 subjects in the cohort developed COPD during the follow-up. Subjects with PRISm, low PEF, sSAD, low MMEF, low FEF50, and low FEF75 had an increased risk of developing COPD (adjusted hazard ratio [HR] ranging from 1.57 to 3.01). Only chronic bronchitis (HR 2.84 [95% CI 1.38-5.84] and 2.94 [1.43-6.04]) and sSAD/low MMEF (HR 2.74 [2.07-3.61] and 2.38 [1.65-3.43]) showed effects independent of the other indicators and their concurrence had the strongest effect (HR 5.89 and 4.80). The prediction model including age, sex, low MMEF, low FEF50, and indoor exposure to biomass had good performance both internally and temporally. The corrected C-index was 0.77 (0.72-0.81) for discrimination in internal validation. For temporal validation, the area under the receiver operating characteristic curve was 0.73 (0.63-0.83). Good calibration was indicated in plot for internal validation and by Hosmer-Lemeshow test for temporal validation.

Interpretation

Individuals with concurrent chronic bronchitis and sSAD/low MMEF indicating pre-COPD optimally require more high attention from physicians. Our prediction model could serve as a multi-dimension tool to predict COPD comprehensively.

Funding

The Ministry of Finance and the Ministry of Science and Technology of the People's Republic of China and the National Natural Science Foundation of China.

The Role of Small Airway Disease in Pulmonary Fibrotic Diseases

Small airway disease (SAD) is a pathological condition that affects the bronchioles and non-cartilaginous airways 2 mm or less in diameter. These airways play a crucial role in respiratory function and are often implicated in various pulmonary disorders. Pulmonary fibrotic diseases are characterized by the thickening and scarring of lung tissue, leading to progressive respiratory failure. We aimed to present the link between SAD and fibrotic lung conditions. The evidence suggests that SAD may act as a precursor or exacerbating factor in the progression of fibrotic diseases. Patients with fibrotic conditions often exhibit signs of small airway dysfunction, which can contribute to worsening respiratory symptoms and decreased lung function. Moreover, individuals with advanced SAD are at a heightened risk of developing fibrotic changes in the lung. The interplay between inflammation, environmental factors, and genetic predisposition further complicates this association. The early detection and management of SAD can potentially mitigate the progression of fibrotic diseases, highlighting the need for comprehensive clinical evaluation and research. This review emphasizes the need to understand the evolving connection between SAD and pulmonary fibrosis, urging further detailed research to clarify the causes and potential treatment between the two entities.

What adverse health effects will environmental heavy metal co-exposure bring us: based on a biological monitoring study of sanitation workers

To investigate the relationship between health effect profile and co-exposure to heavy metal, 254 sanitation workers from Guangzhou, China, were recruited. Ten urinary metals were determined by inductively coupled plasma mass spectrometry. Parameters of physical examination, including blood lipid metabolism, renal function, blood pressure, and lung function, were tested for each participant. The hazard quotients (HQs) of eight heavy metals were evaluated. Cobalt, copper (Cu), molybdenum (Mo), nickel (Ni), and tin (Sn) demonstrated the top five associations with human health with the ∑₁₉β as 2.220, 1.351, 1.234, 0.957, and 0.930, respectively. Most physical examination parameters of workers were under the normal ranges, except the levels of forced mid expiratory flow rate (MMEF_75/25), the maximum expiratory flow rate at 25% vital capacity (MEF₂₅) and apolipoprotein B in the first quartile, and the level of uric acid in the third quartile of sanitation works. Moreover, Cu was significantly associated with diastolic pressure, pulse, and high density lipid (p < 0.05). Each unit increase in Mo level was related to a 120% increase odd ratio (OR) of abnormal of systolic pressure, but was significantly and negatively correlated with high density lipoprotein and apolipoprotein A, suggesting that Mo exposure may be a risk factor of cardiovascular disease. Each unit increase in Ni and Sn levels was associated with an increased OR of abnormal rate of MMEF_75/25 and MEF₂₅ (p < 0.001), suggesting the increasing risks of respiratory diseases. Sanitation workers exposed to Ni and Pb alone had no carcinogenic risks (HQ < 1). However, 23.8%, 34.6%, and 87.3% of sanitation workers confronted non-carcinogenic risks when exposed to Cu, Mo alone (HQ > 1), or co-exposed to the four heavy metals (HI > 1). Our study preliminarily revealed the potential sensitive health indicators of heavy metal co-exposure, which will provide beneficial health protection suggestions for the occupational populations.

Functional Predictors Discriminating Asthma-COPD Overlap (ACO) from Chronic Obstructive Pulmonary Disease (COPD)

Background

A significant proportion of patients with obstructive lung disease have clinical and functional features of both asthma and chronic obstructive pulmonary disease (COPD), referred to as the asthma–COPD overlap (ACO). The distinction of these phenotypes, however, is not yet well-established due to the lack of defining clinical and/or functional criteria. The aim of our investigations was to assess the discriminating power of various lung function parameters on the assessment of ACO.

Methods

From databases of 4 pulmonary centers, a total of 540 patients (231 males, 309 females), including 372 patients with asthma, 77 patients with ACO and 91 patients with COPD, were retrospectively collected, and gradients among combinations of explanatory variables of spirometric (FEV₁, FEV₁/FVC, FEF_25-75), plethysmographic (sR_eff, sG_eff, the aerodynamic work of breathing at rest; sWOB), static lung volumes, including trapped gases and measurements of the carbon monoxide transfer (DL_CO, K_CO) were explored using multiple factor analysis (MFA). The discriminating power of lung function parameters with respect to ACO was assessed using linear discriminant analysis (LDA).

Results

LDA revealed that parameters of airway dynamics (sWOB, sR_eff, sG_eff) combined with parameters of static lung volumes such as functional residual capacity (FRC_pleth) and trapped gas at FRC (V_TG^FRC) are valuable and potentially important tools discriminating between asthma, ACO and COPD. Moreover, sWOB significantly contributes to the diagnosis of obstructive airway diseases, independent from the state of pulmonary hyperinflation, whilst the diffusion capacity for carbon monoxide (DL_CO) significantly differentiates between the 3 diagnostic classes.

Conclusion

The complexity of COPD with its components of interaction and their heterogeneity, especially in discrimination from ACO, may well be differentiated if patients are explored by a whole set of target parameters evaluating, interactionally, flow limitation, airway dynamics, pulmonary hyperinflation, small airways dysfunction and gas exchange disturbances assessing specific functional deficits.

HDAC6 inhibitor ACY-1083 shows lung epithelial protective features in COPD

Airway epithelial damage is a common feature in respiratory diseases such as COPD and has been suggested to drive inflammation and progression of disease. These features manifest as remodeling and destruction of lung epithelial characteristics including loss of small airways which contributes to chronic airway inflammation. Histone deacetylase 6 (HDAC6) has been shown to play a role in epithelial function and dysregulation, such as in cilia disassembly, epithelial to mesenchymal transition (EMT) and oxidative stress responses, and has been implicated in several diseases. We thus used ACY-1083, an inhibitor with high selectivity for HDAC6, and characterized its effects on epithelial function including epithelial disruption, cytokine production, remodeling, mucociliary clearance and cell characteristics. Primary lung epithelial air-liquid interface cultures from COPD patients were used and the impacts of TNF, TGF-β, cigarette smoke and bacterial challenges on epithelial function in the presence and absence of ACY-1083 were tested. Each challenge increased the permeability of the epithelial barrier whilst ACY-1083 blocked this effect and even decreased permeability in the absence of challenge. TNF was also shown to increase production of cytokines and mucins, with ACY-1083 reducing the effect. We observed that COPD-relevant stimulations created damage to the epithelium as seen on immunohistochemistry sections and that treatment with ACY-1083 maintained an intact cell layer and preserved mucociliary function. Interestingly, there was no direct effect on ciliary beat frequency or tight junction proteins indicating other mechanisms for the protected epithelium. In summary, ACY-1083 shows protection of the respiratory epithelium during COPD-relevant challenges which indicates a future potential to restore epithelial structure and function to halt disease progression in clinical practice.

Small airway function measured using forced expiratory flow between 25% and 75% of vital capacity and its relationship to airflow limitation in symptomatic ever-smokers: a cross-sectional study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is diagnosed and its severity graded by traditional spirometric parameters (forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) and FEV₁, respectively) but these parameters are considered insensitive for identifying early pathology. Measures of small airway function, including forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75), may be more valuable in the earliest phases of COPD. This study aimed to determine the prevalence of low FEF_25-75 in ever-smokers with and without airflow limitation (AL) and to determine whether FEF_25-75 relates to AL severity.

METHOD

A retrospective analysis of lung function data of 1458 ever-smokers suspected clinically of having COPD. Low FEF_25-75 was defined by z-score<-0.8345 and AL was defined by FEV₁/FVC z-scores<-1.645. The severity of AL was evaluated using FEV₁ z-scores. Participants were placed into three groups: normal FEF_25-75/ no AL (normal FEF_25-75/AL-); low FEF_25-75/ no AL (low FEF_25-75/AL-) and low FEF_25-75/ AL (low FEF_25-75/AL+).

RESULTS

Low FEF_25-75 was present in 99.9% of patients with AL, and 50% of those without AL. Patients in the low FEF_25-75/AL- group had lower spirometric measures (including FEV₁ FEF_25-75/FVC and FEV₃/FVC) than those in the normal FEF_25-75/AL- group. FEF_25-75 decreased with AL severity. A logistic regression model demonstrated that in the absence of AL, the presence of low FEF_25-75 was associated with lower FEV₁ and FEV₁/FVC even when smoking history was accounted for.

CONCLUSIONS

Low FEF_25-75 is a physiological trait in patients with conventional spirometric AL and likely reflects early evidence of impairment in the small airways when spirometry is within the 'normal range'. FEF_25-75 likely identifies a group of patients with early evidence of pathological lung damage who warrant careful monitoring and reinforced early intervention to abrogate further lung injury.

The association between small airway dysfunction and aging: a cross-sectional analysis from the ECOPD cohort

BACKGROUND

Aging has been evidenced to bring about some structural and functional lung changes, especially in COPD. However, whether aging affects SAD, a possible precursor of COPD, has not been well characterized.

OBJECTIVE

We aimed to comprehensively assess the relationship between aging and SAD from computed tomography, impulse oscillometry, and spirometry perspectives in Chinese.

METHODS

We included 1859 participants from ECOPD, and used a linear-by-linear association test for evaluating the prevalence of SAD across various age subgroups, and multivariate regression models for determining the impact of age on the risk and severity of SAD. We then repeated the analyses in these subjects stratified by airflow limitation.

RESULTS

The prevalence of SAD increases over aging regardless of definitional methods. After adjustment for other confounding factors, per 10-yrs increase in age was significantly associated with the risk of CT-defined SAD (OR 2.57, 95% CI 2.13 to 3.10) and the increase in the severity of air trapping (β 2.09, 95% CI - 0.06 to 4.25 for LAA_-856), airway reactance (β - 0.02, 95% CI - 0.04 to - 0.01 for X5; β 0.30, 95% CI 0.13 to 0.47 for AX; β 1.75, 95% CI 0.85 to 2.66 for Fres), as well as the decrease in expiratory flow rates (β - 3.95, 95% CI - 6.19 to - 1.71 for MMEF%predicted; β - 5.42, 95% CI - 7.88 to - 2.95 for FEF₅₀%predicted) for SAD. All these associations were generally maintained in SAD defined by IOS or spirometry. After stratification of airflow limitation, we further found that the effect of age on LAA_-856 was the most significant among almost all subgroups.

CONCLUSIONS

Aging is significantly associated with the prevalence, increased risk, as well as worse severity of SAD. CT may be a more optimal measure to assess aging-related SAD. The molecular mechanisms for the role of aging in SAD need to be explored in the future. Trial registration Chinese Clinical Trial Registry ChiCTR1900024643. Registered on 19 July 2019.