Figure 1.

Output of isoprene (nmol min⁻¹), acetone (arbitrary units) and CO₂ (L min⁻¹) for a healthy volunteer during rest phases and exertion of an effort of 75 W on a stationary bicycle. In case of CO₂, 15 exhalations per minute with 3 L of alveolar air with 4% of CO₂ correspond to 1.8 L min⁻¹ of CO₂ ( = 15*3*0.04 L min⁻¹). Isoprene output through exhaled breath may increase up to a factor ~10 during exertion of an effort, whereas the concentration in breath increases up to a factor ~5. In this experiment, two steady-states of isoprene exhalation appear, (A) at ~25 nmol min⁻¹ (corresponding to production of isoprene in the liver) and (B) at ~100 nmol L⁻¹ (corresponding to production of isoprene in the muscles). In a person with high cholesterol blood level, the production of isoprene in the liver would be decreased under the influence of statins [139]. Reproduced with permission from [69], © 2009 IOP Publishing.