Characterisation of steady-state and transient responses of transcutaneouspO2 andpCO2 by mass spectrometry

The paper describes steady-state and transient responses of transcutaneous pO₂ and pCO₂ by mass spectrometry. The effects of factors affecting the responses were estimated from a mathematical model comprising the skin, a membrane of a sampler and a tube connected to a mass spectrometer. The effect of heading temperature, membrane thickness, gas permeabilities of the membrane and the dimensions of the connecting tube were verified experimentally. Transcutaneous tension (tcp) in O₂ in a steady state was much more dependent on temperature and membrane thickness than in CO₂. The transient response of the tcp was found to be improved, without decreasing the magnitude of the steady-state tcp, by a thinner membrane with a lower permeability and by a shorter connecting tube of a larger inner diameter. The method of calibration was also examined because the magnitude of tcp by mass spectrometry was influenced in particular by water vapour.