The instant invention relates to a holding device for a breathing tube for use in lung function diagnostics. It is characterized in that the holding device (1) comprises a material that is transparent for light having a wavelength in a first wavelength range but nontransparent for light having a wavelength in a second wavelength range. In other aspects, the invention relates to a lung function diagnostics device comprising such a holding device (1), to the novel use of a selectively transparent material for manufacturing such a holding device (1), and to a method for reading out a coding (15) on a surface of a breathing tube (14) for use in lung function diagnostics.
