Noninvasive method and system for measuring pulmonary ventilation

1. A method for determining the tidal volume (V T ) of a subject, comprising:

determining a first anatomical characteristic representing a first linear displacement of the subject's rib cage in a first orientation using a first sensor system;

determining a second anatomical characteristic representing a first linear displacement of the subject's abdomen in said first orientation using a second sensor system;

determining a third anatomical characteristic representing a first axial displacement of the subject's chest wall in said first orientation using said first sensor system and said second sensor system;

determining a first rib cage volume-motion coefficient representing said first orientation of the subject;

determining a corrected abdominal volume-motion coefficient based on an upright abdominal volume-motion coefficient and a linear slope of an abdominal volume-motion coefficient as a function of an axial displacement of the subject's chest wall;

determining a first chest well volume-motion coefficient representing said first orientation of the subject;

providing a first mathematical relationship that is adapted to determine V T of the subject as a function of said first, second and third anatomical characteristics, said first rib cage volume-motion coefficient, said corrected abdominal volume-motion coefficient and said first chest wall volume-motion coefficient; and

determining V T of the subject with said first mathematical relationship and said first, second and third anatomical characteristics, and said first rib cage volume-motion coefficient, said corrected volume-motion coefficient and first chest wall volume-motion coefficient, whereby said determined V T represents the subject's V T at said first orientation.

2. The method of claim 1 , wherein said first axial displacement of said subject's chest wall is determined from a xiphi-umbilical distance.

3. The method of claim 1 , wherein said first axial displacement of said subject's chest wall is determined from a sternal-umbilical distance.

4. The method of claim 1 , wherein said first anatomical characteristic represents a second linear displacement of said rib cage during a first motion of the subject, said second anatomical characteristic represents a second linear displacement of said abdomen during said first motion of the subject, said third anatomical characteristic represents a second axial displacement of said chest wall during said first motion of the subject, said first rib cage volume-motion coefficient represents said first motion of the subject, and said first chest wall volume-motion coefficient represents said first motion of the subject, and wherein said determined V T represents the subject's V T during said first motion.

5. The method of claim 1 , wherein said first orientation comprises an upright position.

6. The method of claim 5 , wherein said first mathematical relationship comprises the following equation

V T =α(ΔRC)+(β u +εXi )×(Δ Ab )+γ(Δ Xi )

wherein ΔRC represents the linear displacement of the rib cage, ΔAb represents the linear displacement of the abdomen, ΔXi represents the change in the xiphi-umbilical distance from an upright position, α represents a rib cage volume-motion coefficient; β represents an abdominal volume-motion coefficient, β u represents the value of the abdominal volume-motion coefficient (β) in the upright position, s represents the linear slope of the relationship of β as a function of the xiphi-umbilical distance Xi, (β u +εXi) represents the corrected abdominal volume-motion coefficient, and γ represents a xiphi-umbilical volume-motion coefficient.

7. The method of claim 1 , wherein said volume-motion coefficients are determined by multiple linear regressions.

8. A method for determining the tidal volume (V T ) of a subject, comprising:

providing a first sensor system adapted to measure linear displacement of the subject's rib cage, said first sensor system including a first transmission coil and a first receive coil;

providing a second sensor system adapted to measure linear displacement of the subject's abdomen, said second sensor system including a second transmission coil and a second receive coil;

determining a plurality of rib cage volume-motion coefficients representing a plurality of orientations of the subject;

determining a plurality of abdomen volume-motion coefficients representing said plurality of orientations of the subject;

determining a plurality of chest wall volume-motion coefficients representing said plurality of orientations of the subject;

providing a posture sensor to determine a first orientation of the subject from one of said plurality of orientations of the subject;

determining a first linear displacement of the subject's rib cage in said first orientation with said first sensor system;

determining a first linear displacement of the subject's abdomen in said, first orientation with said second sensor system;

determining a first axial, displacement of the subject's chest wall as a function of a signal transmitted by said second transmission coil and received by said first receive coil;

providing a first mathematical relationship that is adapted to determine V T of the subject as a function of said first linear displacement of the subject's rib cage, said first linear displacement of the subject's abdomen, said first axial displacement of the chest wall, a respective one of said plurality of rib cage volume-motion coefficients representing said first orientation, a respective one of said plurality of abdomen volume-motion coefficients representing said first orientation, and a respective one of said plurality of chest wall volume-motion coefficients representing said first orientation; and

determining V T of the subject with said first mathematical relationship and said first linear displacement of the subject's rib cage, said first linear displacement of the subject's abdomen, and said first axial displacement of the chest wall, and automatically selecting said respective one of said plurality of abdomen volume-motion coefficients representing said first orientation, said respective one of said plurality of abdomen volume-motion coefficients representing said first orientation, and said respective one of said plurality of chest wall volume-motion coefficients representing said first orientation.

9. The method of claim 8 , including determining a second linear displacement of said rib cage with said first sensor system during a first motion of the subject with said first sensor system, determining a second linear displacement of said subject's abdomen with said second sensor system during said first motion of the subject, determining a second axial displacement of the chest wall during said first motion, determining a second orientation of the subject selected from one of said plurality of orientations of the subject; and determining V T of the subject with said first mathematical relationship and said second linear displacement of the subject's rib cage, said second linear displacement of the subject's abdomen, said second axial displacement of the chest wall, and automatically selecting said respective one of said plurality of abdomen volume-motion coefficients representing said second orientation, said respective one of said plurality of abdomen volume-motion coefficients representing said second orientation, and said respective one of said plurality of chest wall volume-motion coefficients representing said second orientation.

10. The method of claim 8 , wherein said first transmission coil is placed at a first position on a first side of the subject's body, said first receive coil is placed at a second position on a second, opposite side of the subject's body, said second transmission coil is placed at a third position on said first side of the subject's body, and said second receive coil is placed at a fourth position on said second side of the subject's body, said first, second, third and fourth coil positions defining a plurality of geometrical configurations.

11. The method of claim 10 , wherein each of said first and second receive coils is adapted to receive a first and a second signal.

12. The method of claim 11 , wherein said first axial displacement of said subject's chest wall is determined as a function of a least one of said first and second signals and one of said plurality of geometrical configurations.

13. The method of claim 8 , wherein said first mathematical relationship comprises the following equation

V T =α(ΔRC)+β(Δ Ab )+γ(Δ Xi )

wherein V T represents tidal volume, RC represents said first linear displacement of said subject's rib cage, ΔAb represents said first linear displacement of said subject's abdomen, ΔXi represents said first axial displacement of said subject's chest wall, a represents said first rib cage volume-motion coefficient, β represents said abdominal volume-motion coefficient, and γ represents said first chest wall volume-motion coefficient.

14. A method for monitoring respiration of a subject, comprising:

determining a plurality of rib cage volume-motion coefficients representing a plurality of orientations of the subject using a first sensor system;

determining a plurality of abdomen volume-motion coefficients representing said plurality of orientations of the subject using a second sensor system;

determining a plurality of chest wall volume-motion coefficients representing said plurality of orientations of the subject using said first sensor system and said second sensor system;

compiling a plurality of volume-motion coefficient data sets, each of said plurality of volume-motion coefficient data sets including a respective one of said rib cage, abdomen and chest wall volume-motion coefficients that represent a respective one of said plurality of orientations;

providing a first mathematical relationship that is adapted to determine the tidal volume (V T ) of the subject as a function of a first anatomical characteristic representing a first linear displacement of the subject's rib cage, a second anatomical characteristic representing a first linear displacement of the subject's abdomen, a third anatomical characteristic representing a first axial displacement of the subject's chest wall, and a respective one of said plurality of said volume-motion coefficient data sets;

substantially continuously determining which one of said plurality of orientations of the subject, is a current orientation of the subject using a posture sensor; and

substantially continuously determining a plurality of V T of the subject over a first period of time with said first mathematical relationship, each of the plurality of V T of the subject is determined by automatically selecting a respective one of said plurality of volume-motion coefficient data sets that represent the current orientation of the subject.

15. The method of claim 12 , wherein said first mathematical relationship comprises the following equation

V T =α(ΔRC)+β(Δ Ab )+γ(Δ Xi )

wherein V T represents tidal volume, RC represents said first anatomical characteristic, ΔAb represents said second anatomical characteristic, ΔXi represents said third anatomical characteristic, α represents said first rib cage volume-motion coefficient, β represents said first abdominal volume-motion coefficient, and γ represents said first chest wall volume-motion coefficient.