A simple method to reconstruct the molar mass signal of respiratory gas to assess small airways with a double-tracer gas single-breath washout.

For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF) and helium (He) as tracer components has been proposed. It is assumed that small airway diseases may produce typical ventilation inhomogeneities which can be detected within one single tidal breath, when using two tracer components. Characteristic parameters calculated from a relative molar mass (MM) signal of the airflow during the washout expiration phase are analyzed.

Double tracer gas single-breath washout: reproducibility in healthy subjects and COPD.

The applicability and interpretation of inert tracer gas washout tests is hampered by the lack of feasible protocols and reproducibility data. We assessed feasibility, variability and reproducibility of a new easy to perform double tracer gas (DTG) single-breath washout (SBW) test and compared this with conventional nitrogen washouts. In 40 healthy nonsmokers and 20 patients with stable chronic obstructive pulmonary disease (COPD), we performed three N2 vital capacity SBWs, three N2 multiple-breath washouts and three tidal DTG-SBW tests.