Patent ID: 8449473

Claim:
A method of determining the respiratory function of a subject, the method comprising: measuring the concentration of water vapour in the gas stream exhaled by the subject using an electrochemical sensor, wherein said measuring comprises causing the gas stream to impinge on a sensing element of said sensor, the sensing element comprising a working electrode, a counter electrode and a layer of ion exchange material extending between the working electrode and the counter electrode, the ion-exchange layer being configured to form an electrical contact between the working electrode and the counter electrode when exposed to water vapour in said gas stream, and applying a pulsed electric potential across the working electrode and counter electrode whereby the sensor generates an output representative of the change of concentration of water vapour over time in said gas stream; employing a processor to use the output of the sensor to generate data providing a profile representative of said change of water vapour concentration over time in the exhaled gas stream; and from said profile directly determining the respiratory function of the subject.