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J. Bartels is the first named author of the 1954 primary study comparing respiratory dead space measurements using single-breath analysis of oxygen, carbon dioxide, nitrogen or helium. The journal supplies the initial-only byline; it does not establish a fuller personal name. The measurement contribution concerns the relationship between expired gas composition and expired volume.^[ref]

A single expired breath is not compositionally uniform. Conducting-airway gas appears before gas from exchanging regions, with a transition that depends on mixing and measurement response. Pairing mouth-flow recording with gas-fraction recording allows elapsed time to be converted into an expired-volume coordinate. Synchronization matters because a gas analyser can respond later than the flow sensor.

An original idealized washout curve makes the volume interpretation concrete. Suppose a tracer fraction is zero over the first 100 mL, rises linearly to its plateau over the next 100 mL, and then stays at a plateau value $F_A$. The equivalent sharp-boundary volume under this flat-plateau model isThe transition contributes half its width. This synthetic equal-area construction explains a measurement principle; it is not a reported observation from Bartels's subjects.

A sloping plateau, incomplete tracer equilibration or analyser delay can change the inferred boundary. Comparing tracers therefore tests a physiological measurement model as well as an instrument. Bartels's verified authorship belongs to that gas-analysis experiment, without claiming that the initial-only name identifies a particular namesake or that every definition of respiratory dead space gives an identical volume.