The spirometric parameter maximal mid-expiratory flow (MMEF) test is a good compliment to the lung clearance index (LCI) for diagnosing adults with bronchiectasis, according to researchers at First Affiliated Hospital of Guangzhou Medical University, in China.
In the study, “Maximal mid-expiratory flow is a surrogate marker of lung clearance index for assessment of adults with bronchiectasis,” published in the journal Scientific Reports, researchers showed that MMEF and LCI have similar diagnostic value for identifying bronchiectasis; although MMEF is easier to measure, requires shorter test periods, and uses less complex instruments.
The non-uniform distribution of inspired gas within the lungs is called ventilation heterogeneity. Although it is observed in healthy lungs because of differential distributions of blood and air caused by gravity gradients, chronic respiratory diseases such as bronchiectasis aggravate the condition with overproduced mucus, pulmonary infections, or airway remodeling.
Ventilation heterogeneity, commonly associated with poor lung function, can be identified via high-resolution computed tomography (HRCT) scans of the chest, or through LCI which is more sensitive for the diagnosis of other diseases such as cystic fibrosis.
MMEF can also be used to detect changes in lung architecture; expiratory flow is lower in bronchiectasis patients. Using the more simple and less expensive MMEF instead of LCI to diagnose bronchiectasis would make testing available to more patients at much lower health care costs.
With that idea in mind, the study investigators compared the diagnostic value of MMEF with that of LCI, to see if the parameters accompanied bronchiectasis exacerbations and if MMEF could be used as a diagnostic tool instead of LCI. The study included 115 bronchiectasis patients from the First Affiliated Hospital of Guangzhou Medical University, who were already diagnosed through HRCT scans.
Results showed that LCI and MMEF had similar diagnostic value in discriminating severe-to-moderate from mild bronchiectasis. In fact, both parameters correlated significantly with forced expiratory flow in one second (FEV1; a measure of lung function), age, and HRCT score, and were able to reflect clinical characteristics of bronchiectasis that included cystic bronchiectasis, ventilation heterogeneity, Pseudomonas aeruginosa (bacteria) colonization, and bilateral bronchiectasis.
But both LCI and MMEF showed limited ability for identifying bronchiectasis exacerbations or changes after antibiotic treatment. Researchers concluded that neither test should be used alone – but could surely be used to support the other – in determining severity of bronchiectasis exacerbation or confirming exacerbation recovery.