The physiological assessment of small airways function in chronic obstructive pulmonary disease and their utility in assessing bronchodilator responsiveness and during acute exacerbation episodes

Alobaidi, Nowaf Y. (2022). The physiological assessment of small airways function in chronic obstructive pulmonary disease and their utility in assessing bronchodilator responsiveness and during acute exacerbation episodes. University of Birmingham. Ph.D.

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Abstract

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease that is linked to high mortality and morbidity. In COPD, the majority of airway resistance is located in the small airways. Studies have demonstrated that small airway dysfunction (SAD) has an important role in COPD pathophysiology. Few studies have shown that SAD can improve post-bronchodilator (BD) in some COPD patients, demonstrating the value of evaluating small airways as part of the bronchodilator responsiveness (BDR) assessment. Furthermore, there is evidence that SAD is worsened by inflammation associated with acute exacerbations of COPD (AECOPD), and it may improve as patients recover, indicating that small airway tests can be used to map and monitor recovery from AECOPD.
This thesis aimed to physiologically examine the small airway function in COPD and their utility in the assessment of bronchodilator responsiveness and during acute exacerbation of COPD.
Firstly, two cross-sectional studies were conducted using routinely collected lung function data of patients referred to the lung function unit as part of COPD screening to determine the prevalence of SAD in symptomatic ever-smokers and never-smokers. Secondly, to assess the utility of small airway tests in BDR assessment, a systematic literature review was carried out to identify the evidence of their use and a retrospective analysis of routinely collected lung function data of COPD patients was done to determine the use of MMEF as a measure of small airways (SA) in BDR assessment. Thirdly, to evaluate the utility of small airway tests during AECOPD, a systematic review of the literature to evaluate the evidence of their use in the acute setting was conducted.
Both cross-sectional studies of spirometric data found SAD in nearly all patients with established AO and 33-50% of patients without AO. This highlights that physiological assessment of small airways might play an important role in managing COPD. The presence of SAD without AO in some symptomatic patients suspected of COPD indicates that this group may have early lung injuries and may benefit from being closely monitored to prevent COPD.
The systematic review of SA tests in BDR reported that previous studies showed that measures of SA were associated with notable changes following bronchodilator administration, but studies were few and included a small number of participants, warranting the need for a study to determine their utility. The BDR study demonstrated that BDR in MMEF is detected in 59.2% of COPD patients in the cohort, and importantly, was detected in nearly 37.9% of patients without BDR in FEV1. This highlight that SA tests (particularly MMEF) could add to current spirometric measures used in the BDR assessment, providing insight into a clinical phenotype for patients displaying BDR in the SA alone, although further studies are needed to determine its clinical implications.
The systematic review of SA tests in AECOPD found six articles that showed that SA tests improved in correlation with FEV1 during recovery from exacerbation. Notably, SA tests showed an earlier sign of change from exacerbation onset than FEV1. These studies suggest that SA tests could be of value as a monitoring tool during AECOPD. Of the SA tests, FOT seems to be feasible and acceptable during AECOPD and may be useful for monitoring its recovery, although a comprehensive pilot study is needed to confirm this.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):