Physiological tests of small airways function in diagnosing asthma: a systematic review

Bronchiolar disorders in systemic autoimmune rheumatic diseases

Pulmonary manifestations of systemic autoimmune rheumatic diseases (SARDs) may involve the large and small airways, lung parenchyma, pleura, respiratory muscles and thoracic cage. Bronchiolar disorders (BDs) or small airways disease (SAD) are common and may sometimes be the dominant presentation in patients with SARDs. We conducted a literature review using search terms "bronchiolitis," "small airway diseases" and the names of individual SARDs and collated relevant articles published between January 1977 and April 2024. A summary of the incidence/prevalence, clinical manifestations, pathogenetic mechanisms, pulmonary function testing, chest imaging, histopathology and treatment options for BDs associated with SARDs is provided in this review. BDs associated with Sjögren syndrome, rheumatoid arthritis, systemic sclerosis, systemic lupus erythematosus, idiopathic inflammatory myositis, mixed connective tissue disease and ankylosing spondylitis are specifically highlighted.

Diagnostic Accuracy of FEF25-75 for Bronchial Hyperresponsiveness in Patients with Suspected Asthma and/or Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Some studies have suggested that the forced expiratory flow between 25 and 75% of vital capacity (FEF25-75) can be used as an early marker of bronchial hyperresponsiveness (BHR) in asthma and allergic rhinitis (AR), but is highly variable. Here, we aimed to assess whether the FEF25-75 can be used to diagnose BHR in patients with asthma-like symptoms and AR.

METHODS

PubMed, EMBASE, Web of Science, Wiley Online Library, Cochrane Library, SinoMed, CNKI, and Wanfang Data were searched to acquire eligible studies. Articles published before 30 Sep 2023 were included. Quality Assessment of Diagnostic Accuracy Studies 2 was used to evaluate the risk of bias and application concern of the included articles. Data were pooled using random-effects models. The univariable meta-regression and subgroup analyses were used to explore the sources of heterogeneity.

RESULTS

Twenty-five studies were included, describing 12,310 patients with asthma-like symptoms and AR. In terms of the FEF25-75, the pooled sensitivity and specificity were 0.56(95% CI 0.47-0.65) and 0.86 (95% CI 0.80-0.90), respectively. In addition, the pooled diagnostic odds ratio (DOR) was 8.00 (95% CI 6-10) and the area under the curve (AUC) was 0.80 (95% CI 0.76-0.83). Furthermore, we performed the univariable meta-regression and subgroup analyses, indicating that the disease types and ethnicity may be the sources of heterogeneity.

CONCLUSION

This meta-analysis showed that if BPT cannot be performed a value of FEF25-75 < 65% of predicted may suggest the presence of BHR in patients with suspected asthma and /or AR.

The prevalence of small airways disease and association with handgrip strength in young Hispanic farmworkers

BACKGROUND

Small airways disease (SAD) is a key risk in developing obstructive lung diseases (OLD). Handgrip strength (HGS) is found to be associated with pulmonary function in populations with lung conditions. Hispanics remain the main workforce in farming industry, but their prevalence of lung conditions remain understudied. Likewise, HGS also remains understudied in Hispanic and farmworker populations. Our study investigated the prevalence of SAD and OLD as well as their associations with HGS among Hispanic farmworkers.

METHODS

A cross-sectional study analyzed 113 Hispanic farmworkers (54% female) who were screened using pulmonary function tests during annual health fairs in rural Southeastern US from 2013 to 2017. Smoking status was self-reported. SAD was defined as forced expiratory flow at 25-75% predicted of vital capacity (FEF25-75%predicted) ≤ 60% per literature and OLD defined as forced expiratory volume in 1 s/ forced vital capacity (FEV1/FVC) ratio < 70% per Global Initiative for Chronic Obstructive Lung Disease criteria. Seated isometric absolute (the sum of both hands) and relative (absolute handgrip strength divided by body mass index) handgrip strengths were collected.

RESULTS

26.5% of subjects had SAD and 15.9% had OLD. 50% of subjects with SAD had OLD while 83% of subjects with OLD had SAD. 13% of overall population smoked. Lower absolute and relative HGS groups had higher prevalence of SAD and OLD. Multivariate linear regression showed that lower absolute and relative HGS were associated with worsened small airway function. Age and FEF25-75%predicted were associated with FEV1/FVC. Smoking, body mass index, blood pressures, hemoglobin A1C and lipids were not predictors in either model.

CONCLUSIONS

This is one of the first studies reporting prevalence of pulmonary function in Hispanic farmworkers. Although this population was relatively young and healthy, there was high prevalence of SAD and OLD, which was higher than the overall prevalence in Hispanic population. There were more females subjects with SAD. Most of the subjects with OLD had SAD but not vice versa. Lower HGS levels were associated with worsened pulmonary function, and HGS was a significant predictor of FEF25-75%predicted, a potential marker for small airway physiology.

Prevalence of small airway dysfunction in the Swiss PneumoLaus Cohort

Background

Recent evidence identified exposure to particulate matter of size ≤2.5 µm (PM2.5) as a risk factor for high prevalence of small airway dysfunction (SAD). We assessed the prevalence of SAD in a European region with low air pollution levels.

Methods

SAD was defined as a maximum mid-expiratory flow (MMEF) <65% of predicted value (PV) or MMEF

Results

Among 3351 participants (97.6% Caucasian, 55.7% female sex, mean age 62.7 years), we observed MMEF <65% PV in 425 (12.7%) and MMEF 65 years only. In an area where ambient PM2.5 concentration was <15 µg·m-3 during the observation period (2010 and 2020), ≥72% of participants with SAD were ever-smokers.

Conclusions

The observed low prevalence of SAD of 5.0-12.7% depending on criteria employed may be related to lower PM2.5 exposure. Smoking was the main factor associated with SAD in an area with low PM2.5 exposure. Employing a MMEF threshold <65% PV carries a risk of SAD overdiagnosis in elderly individuals.

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Affiliation(s)

Brice Touilloux Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland Division of Pulmonology, Department of Medicine and Specialties, Fribourg Hospital, Fribourg, Switzerland
Cedric Bongard Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Benoit Lechartier Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Minh Khoa Truong Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Pedro Marques-Vidal Division of Internal Medicine, Department of Medicine, CHUV and UNIL, Lausanne, Switzerland
Peter Vollenweider Division of Internal Medicine, Department of Medicine, CHUV and UNIL, Lausanne, Switzerland
Julien Vaucher Division of Internal Medicine, Department of Medicine, CHUV and UNIL, Lausanne, Switzerland Division of Internal Medicine, Department of Medicine and Specialties, Fribourg Hospital, Fribourg, Switzerland University of Fribourg, Fribourg, Switzerland
Alessio Casutt Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland Division of Pneumology, Ospedale Regionale di Lugano, Ente Ospedaliero Cantonale, Lugano, Switzerland These authors contributed equally
Christophe von Garnier Division of Pulmonology, Department of Medicine, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland These authors contributed equally

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Assessing Asthma Control by Impulse Oscillometry and Fractional Expiratory Nitric Oxide in Children With Normal Spirometry

BACKGROUND

Because spirometric parameters fail to address current status of asthma in some patients, additional tests are required for better evaluation of asthma.

OBJECTIVE

We aimed to test the ability of impulse oscillometry (IOS) and fractional expiratory nitric oxide (FeNO) in identifying inadequately controlled asthma (ICA) that was not uncovered by spirometry.

METHODS

Recruited asthmatic children between ages of 8 and 16 years underwent spirometry, IOS, and FeNO measurements on the same day. Only subjects who had spirometric indices within normal range were included. Asthma Control Questionnaire-6 scores of 0.75 or lower and greater than 0.75 indicated well-controlled asthma (WCA) and ICA. Percent predicted values of IOS parameters and IOS reference values for upper and lower limits of normal (>95th and <5th percentiles, respectively) were calculated on the basis of previously published equations.

RESULTS

There were no significant differences in all spirometric indices between the WCA (n = 59) and the ICA (n = 101) groups. The % predicted values of IOS parameters except resistance at 20 Hz (R20) were significantly different between the 2 groups. Receiver operating characteristic analysis showed that the highest and lowest areas under the curve were 0.81 and 0.67 for the difference between the resistances at 5 Hz and 20 Hz (R5-R20) and R20 in discrimination of ICA versus WCA. The areas under the curve for IOS parameters were improved by combination with FeNO. The better discriminative ability of IOS was also supported by the higher values of the concordance index for the resistance at 5 Hz (R5), R5-R20, the reactance at 5 Hz (X5), and the resonant frequency of reactance than those for spirometric parameters. Compared with those with normal values, subjects with abnormal IOS parameters or high FeNO had significantly higher odds of having ICA.

CONCLUSIONS

The IOS parameters and FeNO were shown to be useful in identifying children with ICA when spirometry was normal.

Small Airways Response to Bronchodilators in Adults with Asthma or COPD: A Systematic Review

BACKGROUND

Bronchodilator responsiveness (BDR) is commonly used in the diagnosis of lung disease. Although small airways dysfunction is a feature of asthma and COPD, physiological tests of small airways are not included in guidelines for BDR testing. This systematic review assessed the current evidence of BDR using small airways function in asthma and COPD.

METHODS

The systematic review used standard methodology with the protocol prospectively registered on PROSPERO (CRD42020164140). Electronic medical databases (EMBASE and Medline) were searched using related keywords. Abstracts and full texts were screened independently by two reviewers. Studies that reported the change of physiological small airways function and FEV₁ were included in the review. The revised Cochrane risk of bias tool for RCT and NIH quality assessment tool for cohort and cross-sectional studies were used to evaluate the studies.

RESULTS

A total of 934 articles were identified, with 12 meeting the inclusion criteria. Ten studies included asthma patients, 1 study included COPD patients and 1 study included both asthma and COPD. A total of 1104 participants were included, of whom 941 were asthmatic, 64 had COPD and 109 were healthy controls. Studies were heterogeneous in design including the device, dose and time intervals for BDR assessment. A small airway BDR was seen for most tests in asthma and COPD, including oscillometry (R5-20, reactance (X5), area of reactance (AX) and resonant frequency (Fres)) and Maximal Mid Expiratory Flow.

CONCLUSION

There is a measurable BDR in the small airways. However, with no consensus on how to assess BDR, studies were heterogeneous. Further research is needed to inform how BDR should be assessed, its clinical impact and place in routine clinical practice.

The diagnosis of asthma. Can physiological tests of small airways function help?

Asthma is a common, chronic, and heterogeneous disease with a global impact and substantial economic costs. It is also associated with significant mortality and morbidity and the burden of undiagnosed asthma is significant. Asthma can be difficult to diagnose as there is no gold standard test and, while spirometry is central in diagnosing asthma, it may not be sufficient to confirm or exclude the diagnosis. The most commonly reported spirometric measures (forced expiratory volume in one second (FEV₁) and forced vital capacity assess function in the larger airways. However, small airway dysfunction is highly prevalent in asthma and some studies suggest small airway involvement is one of the earliest disease manifestations. Moreover, there are new inhaled therapies with ultrafine particles that are specifically designed to target the small airways. Potentially, tests of small airways may more accurately diagnose early or mild asthma and assess the response to treatment than spirometry. Furthermore, some assessment techniques do not rely on forced ventilatory manoeuvres and may, therefore, be easier for certain groups to perform. This review discusses the current evidence of small airways tests in asthma and future research that may be needed to further assess their utility.