MODEL RELEASED: Clinical trial of a respiratory drug. This young volunteer is an asthmatic. The vapour seen coming from the pipe is a solution, UNDW, which induces hyperventilation. The computer screen shows transcutaneous measurements of oxygen (blue, top) and carbon dioxide (yellow, bottom) blood concentrations. The left side of the screen shows the normal asthmatic response. Note that the carbon dioxide drops rapidly, then recovers, after inhalation of UNDW, but that the oxygen concentration drops later and for a long time. At the right side of the screen is the test after premedication with the drug - the long term drop in oxygen concentration is absent.