A Systematic Review of the Use of Physiological Tests Assessing the Acute Response to Treatment During Exacerbations of COPD (with a Focus on Small Airway Function)

Abstract

Exacerbations are prevalent in Chronic Obstructive Pulmonary Disease (COPD) patients and associated with poor clinical outcomes. Currently, there is a lack of sensitive and specific tools that can objectively identify exacerbations and assess their progress or treatment response. FEV₁ is often reported as a study outcome, but it has significant limitations. Studies have suggested that small airways measures might provide physiological biomarkers during exacerbations. Therefore, this study was done to assess which physiological tests of small airways function have been used in the acute setting during exacerbations of COPD and the evidence to support their use. An electronic databases search was conducted in April 2019. A standard systematic review methodology was used. Eligible studies were those of ≥10 participants that compared at least one small airway test with FEV₁ to assess response to treatment with baseline and a follow-up measurement ≤2 months after. Analyses were narrative. Of 1436 screened studies, seven studies were eligible. There was heterogeneity in which tests of small airways were used and three different small airways measures were reported. Studies were small (including 20 to 87 subjects). Six articles reported improvements in small airway measurements during the recovery from exacerbation which correlated with FEV₁. Included studies varied in their timing and duration of the assessment. There is some evidence to support the use of small airway tests in acute exacerbations of COPD. However, studies have been small with different tests being utilized. Further studies to determine the usefulness of each test may be of interest.

Keywords:

• COPD
• exacerbation
• monitoring
• small airways’ tests
• small airway dysfunction
• Lung function

Acknowledgement

The authors would like to thank Adam Seccombe for his help and support in refining the search strategy. RGE was supported by a Clinical Trials Fellowship (NIHR300008), supported by the National Institute for Health Research (NIHR), outside of the scope of this work. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health.

Authors contributions

NYA and ES designed the study. NYA performed the initial search and data extraction. NYA, RGE and MA assessed the eligibility of the included studies. NYA and MA performed the quality assessment for the included studies. NYA wrote the initial manuscript. RGE, ES and JS revised the manuscript. All authors read and approved the final version of the manuscript.

Declaration of interest

The authors report no conflict of interest.

Additional information

Funding

The current study was undertaken as part of NYA’s PhD. NYA is supported by King Saud bin Abdulaziz University for health sciences through the Saudi Arabian Cultural Bureau in the UK.