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

Med Biol Eng Comput. 2017 Nov;55(11):1975-1987. doi: 10.1007/s11517-017-1633-y. Epub 2017 Mar 29.


For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF6) 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. The DTG-SBW signal is acquired by subtracting a reconstructed MM signal without tracer gas from the signal measured with an ultrasonic sensor during in- and exhalation of the double-tracer gas for one tidal breath. In this paper, a simple method to determine the reconstructed MM signal is presented. Measurements on subjects with and without obstructive lung diseases including the small airways have shown high reliability and reproducibility of this method.

Keywords: Double-tracer gas single-breath washout (DTG-SBW); OLS; Signal reconstruction; Small airway diseases.

MeSH terms

  • Adult
  • Airway Obstruction / diagnosis*
  • Airway Obstruction / metabolism
  • Child
  • Helium / metabolism
  • Humans
  • Lung / metabolism*
  • Pulmonary Disease, Chronic Obstructive / diagnosis*
  • Pulmonary Disease, Chronic Obstructive / metabolism
  • Pulmonary Ventilation / physiology*
  • Reproducibility of Results
  • Respiration
  • Sulfur Hexafluoride / metabolism
  • Tidal Volume / physiology


  • Helium
  • Sulfur Hexafluoride

Supplementary concepts

  • Pulmonary Disease, Chronic Obstructive, Severe Early-Onset