Patent ID: 6983750

Claim:
A method for determining gas exchange efficiencies of volumetric portions of and the volume of the lungs of a subject to express ventilation homogeneity characteristics of volumetric portions of the lungs, said method comprising the steps of: (a) allowing the patient to breathe with breathing gases having given properties regarding the amount of an inert gas contained therein; (b) ascertaining the concentration F o of the inert gas in the lungs of the subject; (c) altering the amount of the inert gas in the breathing gases provided to the subject; (d) causing the subject to breathe breathing gases having the altered amount of the inert gas; (e) thereafter measuring the change in volume ΔV ig of the inert gas in the lungs of the subject and the concentration F of inert gas in the lungs of the subject for each breath; (f) making a determination of the lung volume V of the subject using a summation of the volume change ΔV ig of the inert gas in the lungs of the subject, the concentration F of the inert gas in the lungs of the subject, and the amount F o of the inert gas in the breathing gases ascertained in step (b); (g) obtaining a measure of the gas exchange efficiency of the subject's lungs using the breathing gas volume V A of the subject and the lung volume V determined in step (f); (h) repeating step (e) and, respectively, steps (f) and (g) for a subsequent breath of the subject to make at least one further determination of the lung volume V of the subject and obtain at least one further gas exchange efficiency measure; (i) forming a lung volume V data series comprising the volumes V determined for each breath and, respectively, a gas exchange efficiency data series comprising gas exchange efficiencies obtained for each breath; and (j) expressing the ventilation homogeneity of volumetric portions of the lungs of the subject by relating the series of gas exchange efficiencies to the lung volume series.