Method and apparatus for determining functional residual capacity of the lungs
AssigneeGeneral Electric Company
InventorErkki Heinonen
Life of this patent
Estimating the term…
Abstract
The functional residual capacity (FRC) value of a subject's lungs determined for each breath is related a volume dilution factor kn and the final FRC value is determined at the point where the volume dilution factor kn reaches a predetermined volume dilution factor value. The determination of the final FRC value can be based on interpolation or extrapolation from a measured breath data series. The volume dilution factor may be normalized value. This is achieved by division of all volume dilution factors with the initially determined volume dilution factor. With normalization, the compartments in which gas concentration change is achieved slowly are referenced with the faster, more effective compartments, thus giving a ventilation profile of the lungs.
Claims18
A method for determining the functional residual capacity of a subject's lungs using a washout/wash-in technique in which a concentration of a tracer gas in the inspired breathing gases for the subject is altered from an initial concentration, said method comprising the steps of:
- (a) providing a functional residual capacity (FRC) measuring circuit having a central processing unit (CPU);
- (b) determining in the CPU, for each of a plurality of breaths of a series of breaths, a value of a volume dilution factor kn, where the volume dilution factor is calculated using tidal volume and lung volume for each breath;
- (c) determining in the CPU, for each breath of the plurality of breaths, a value of the functional residual capacity of the subject's lungs;
- (d) establishing a predetermined value for the volume dilution factor kn;
- (e) determining in the CPU when the value of the volume dilution factor kn determined in step (b) stands in a predetermined relationship to the predetermined value for the volume dilution factor kn;
- (f) establishing a relationship in the CPU between the determined value for the volume dilution factor kn and the functional residual capacity of a subject's lungs over the plurality of breaths;
- and
- (g) estimating the functional residual capacity of the subject's lungs in the CPU at the predetermined value for the volume dilution factor kn based upon the established relationship of step (f).
A method for determining the functional residual capacity of a subject's lungs using a washout/wash-in technique in which the concentration of a tracer gas in the inspired breathing gases for the subject is altered from an initial concentration, said method comprising the steps of:
- (a) providing a functional residual capacity (FRC) measuring circuit having a central processing unit (CPU);
- (b) determining a functional residual capacity (FRC) value in the CPU for the subject's lungs for each of a plurality of breaths of a series of breaths;
- (c) determining in the CPU, for each of the plurality of breaths of the series of breaths, a value of a volume dilution factor kn, where the volume dilution factor is calculated using tidal volume and lung volume for each breath;
- (d) establishing a relationship between the functional residual capacity value determined in step (b) to the volume dilution factor value kn determined in step (c) for the plurality of breaths of the series of breaths;
- (e) determining in the CPU when the value of the volume dilution factor kn determined in step (c) stands in a predetermined relationship to a predetermined value for the volume dilution factor kn;
- and
- (f) determining an estimated functional residual capacity value in the CPU based upon the predetermined relationship established in step (e) between the functional residual capacity value determined in (b) and the volume dilution factor kn determined in (c), wherein the estimated functional residual capacity value is the functional residual capacity of the subject's lungs at the predetermined value for the volume dilution factor kn.
Dependencies are inferred from the claim text.