Multiple Breath Washout Testing With Sulphur Hexafluoride Feasible, Reproducible in Adults With Bronchial Asthma

Multiple breath washout (MBW) testing with sulphur hexafluoride (SF₆) was found to be feasible and reproducible for the assessment of ventilation heterogeneity in adults with bronchial asthma, according to a study published in Scientific Reports.

In this study, 91 patients with a known or a first bronchial asthma diagnosis and 47 individuals without asthma were enrolled. MBW parameters were measured after 3 consecutive washouts using a commercially available closed-circuit system. MBW parameters reflected: functional residual capacity, acinar ventilation heterogeneity (S_acin) and conductive ventilation heterogeneity (S_cond). The lung clearance index (LCI) was calculated for the 2.5% (LCI_2.5) and 5% (LCI₅) stopping points.

Patients with vs without asthma had higher LCL_2.5 and LCL₅ (P <.001), and elevated S_acin (P <.001) and S_cond (P <.01). Coefficients of variation for LCL_2.5 and LCL₅ were 3.4% and 3.5%, respectively in patients with asthma.

The mean total washout times at the LCL₅ stopping point were reduced by 24 seconds in nonasthmatic individuals (P <.001) and by 28 seconds (P <.001) in patients with asthma. In regard to the differentiation of patients with asthma from healthy controls (ie, diagnostic accuracy).

In a receiver operating curve analysis, the area under the curve was 0.906 to differentiate individuals with asthma from those without asthma, indicating good diagnostic performance. The accuracy of conventional testing of lung function yielded a lower accuracy, as indicated by a smaller area under the curve (0.819; P <.05).

Study limitations include its lack of applicability, as several countries do not allow the medical use of SF₆, and a lack of structured data on asthma control, asthma symptoms, and medication.

”MBW parameters…may contain additional information that can be used to identify [patients with asthma] with abnormal ventilation missed by current tests,” noted the study authors. “Including parameters of ventilation heterogeneity and small airway disease significantly improves diagnostic accuracy of our prediction model.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Trinkmann F, Lenz SA, Schäfer J, et al. Feasibility and clinical applications of multiple breath wash-out (MBW) testing using sulphur hexafluoride in adults with bronchial asthma. Sci Rep. 2020;10(1):1527.