LAUSR

Real time measurements of the differences in inhaled and exhaled normal and fully deuterated acetone concentration levels at rest and during exercise have been conducted using proton transfer reaction mass spectrometry. A novel approach to differentiate continuously the inhaled and exhaled breath acetone concentration signals is used. This leads to unprecedented fine grained data of inhaled and exhaled concentrations. The experimental results obtained are compared with those predicted using a simple three compartment model that theoretically describes the influence of inhaled concentrations on exhaled breath concentrations for volatile organic compounds with high blood:air partition coefficients, and hence appropriate for acetone. Good agreement between predicted and observed concentrations is obtained. Our results highlight that the influence of the upper airways cannot be neglected for volatiles with high blood:air partition coefficients.