Lung function test may catch respiratory issues in late-onset Pompe

A lung function test called intrabreath oscillometry may detect abnormalities related to late-onset Pompe disease (LOPD) that standard breathing tests would miss, a new study shows.

Findings suggest that intrabreath oscillometry may be more reliable than a standard test called spirometry at detecting weakened chest muscles in people with LOPD. However, the study was limited to a small number of patients, and researchers stressed the need for additional validation in larger studies.

“Intrabreath oscillometry identified two distinct airway-mechanical patterns and expiratory abnormalities not detected by spirometry. An abnormal [result on intrabreath oscillometry] may reflect greater clinical respiratory severity despite similar spirometric impairment,” researchers wrote.

“Given the small number of patients, larger studies are needed to determine whether these patterns reflect distinct disease [patterns],” they added.

The study, “Expiratory phase lung mechanics in late-onset Pompe disease: a multicenter study using oscillometry to identify specific breathing abnormalities,” was published as a letter to the editor in the Orphanet Journal of Rare Diseases.

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 LOPD patients commonly experience difficulty breathing

LOPD is a genetic disease marked by muscle weakness. People living with LOPD commonly experience difficulty breathing due to weakness in respiratory muscles, the chest muscles that pull and push air in and out of the lungs when someone breathes.

Spirometry is a standard lung function test that measures how much air someone can blow out in a set amount of time. Better spirometry scores generally reflect stronger respiratory muscles — but spirometry scores can get skewed by differences in how much effort patients put in when taking the test.

Intrabreath oscillometry involves using gentle sound waves to track how lung tissue moves when a person breathes. Among other variables, this can be used to investigate the amount of resistance in the airways. A notable benefit of this approach is that, unlike spirometry, intrabreath oscillometry doesn’t rely on how much effort a patient puts in during the test.

In this study, scientists in Italy compared intrabreath oscillometry and spirometry data from 16 adults with LOPD.

“We aimed to evaluate whether [intrabreath oscillometry] can identify respiratory abnormalities in LOPD patients … [that are] not detected by spirometry,” they said.

The researchers found that the patients could be broadly divided into two groups based on intrabreath oscillometry outcomes. Nine participants had normal findings. The other seven, however, showed an abnormal increase in airway resistance during breaths.

From a clinical perspective, intrabreath oscillometry could complement standard assessments in LOPD by providing a noninvasive, effort-independent signal of [lung function], potentially helping to refine [clinical classification] and longitudinal monitoring.

Notably, spirometry values did not differ significantly between patients with or without these findings. This suggests that intrabreath oscillometry may provide insight into respiratory muscle weakness in LOPD that cannot be achieved with spirometry alone.

“From a clinical perspective, intrabreath oscillometry could complement standard assessments in LOPD by providing a noninvasive, effort-independent signal of [lung function], potentially helping to refine [clinical classification] and longitudinal monitoring,” the scientists concluded.

The scientists called for further studies to expand on these findings.

“Whether the identified patterns predict symptoms, response to ventilatory [breathing] support, mucus clearance efficacy, or clinical outcomes should be tested in larger prospective cohorts,” they wrote. “Longitudinal studies would be appropriate to separately evaluate long-term evolution of clinical features in LOPD patients with and without” abnormalities on intrabreath oscillometry.