Tailoring COPD Management Strategies May Require Additional Pulmonary Function Testing

Although spirometry measurements are a reliable standard used to diagnose chronic obstructive pulmonary disease (COPD), results from additional pulmonary function tests (PFTs) are needed to better tailor management methods to individual patient needs, according to a recent review.

“A holistic patient assessment including multiple parameters is required for efficient COPD phenotyping, as some phenotypes have been shown to respond to treatment differently and have a worse prognosis,” wrote the investigators.

The review, published in npj Primary Care Respiratory Medicine, highlighted the usefulness of several PFTs that could be implemented into primary care practices to enhance the efficiency of COPD management, which can be difficult to establish due to the vast heterogeneity associated with the disease.

Spirometry is typically used to calculate a patient’s forced expiratory volume in the first second (FEV₁) and diagnose COPD. However, measuring FEV₁ as a determinant for COPD may not capture the complex nature of the disease because it does not effectively represent the extent of functional impairment and symptom burden.

“The use of a fixed FEV₁/[forced vital capacity] ratio as a diagnostic cut-off is a rather simplified approach, leading to overdiagnosis of COPD in older patients, while simultaneously underestimating the presence of COPD in younger patients,” the investigators noted.

In addition to the well-established phenotypes of COPD, namely chronic bronchitis, predominant emphysemas, frequent exacerbators, and the overlapping of COPD and asthma, there are several emerging phenotypes expected to be assimilated into regular clinical practice.

Newer phenotypes include fast decliners, the overlapping of COPD and bronchiectasis, high cardiovascular and metabolic comorbidity burden, pulmonary cachexia, and the phenotype reserved for nonsmokers.

In addition to spirometry, other PFTs, such as resting lung volume, capacity and airway resistance evaluations, diffusion capacity measurements, and field or cardiopulmonary exercise testing, could give physicians a more comprehensive understanding of their patients’ disease.

The investigators conducted an international database search and manual review of the identified literature in January 2021.

Whole-body plethysmography, a resting lung volume assessment and airway resistance evaluation, is considered to be more accurate at detecting airway obstruction than gas dilution methods. In addition, measurements of these tests, such as static lung volumes and reserve volumes, are associated with prominent symptoms of COPD and can aid in early disease detection.

Low measurements of diffusing capacity of carbon monoxide (DCLO) can be indicative of the COPD phenotype for predominant emphysemas and a reliable predictor of exertional desaturation in patients with COPD.

Assessments for airway resistance are associated with activity-related dyspnea in patients with moderate to severe COPD. Additionally, a decrease of specific airway resistance can also indicate changes in lung inflation that may be underestimated by spirometry.

Commercialized forced oscillation technique devices can be used to evaluate impedance in COPD, especially in patients unable to perform spirometry, such as children or elderly patients. Oscillometry can also detect early lung dysfunction in smokers prior to them experiencing COPD symptoms.

Field exercise tests, including the 6-minute walk test, are helpful to assess patients’ functional capacity in relation to exercise. Additionally, 6-minute walk tests are more representative of patients’ daily activity compared with other field and cardiopulmonary exercise tests and can be an early indicator of functional disability and increased mortality risk.

However, cardiopulmonary exercise tests can evaluate submaximal and peak exercise responses and can reveal physiological abnormalities in smokers who receive normal spirometry results.

The investigators suggested that physicians could incorporate anthropometric measures that can correlate with airway obstruction severity, such as malnutrition and sarcopenia, into their evaluations. Screening for the presence of pulmonary malnutrition could be easily implemented during routine visits.

The main limitation of the review was that only journal articles written in English were included in the analysis.

“Undoubtedly, FEV₁ remains an invaluable tool for COPD diagnosis and management. However additional functional testing is necessary in order to tailor COPD management to the variety of symptoms and phenotypes encountered in the everyday clinical practice,” wrote the investigators.

Reference

Kakavas S, Kotsiou OS, Perlikos F, et al. Pulmonary function testing in COPD: looking beyond the curtain of FEV₁. NPJ Prim Care Respir Med. Published online May 7, 2021. doi:10.1038/s41533-021-00236-w