Method and system for determining a ventilatory threshold

Patent metadata

Field	Value
Publication number	US-9855007-B2
Application number	US-201314648219-A
Country	US
Kind code	B2
Filing date	Nov 27, 2013
Priority date	Nov 28, 2012
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method of determining the ventilatory threshold of a subject in real time during an exercise session wherein data relating to physiological parameters of said subject are acquired and stored in function of time during the exercise session, said data including at least data indicative of the respiration and of the heart beat rate. The method includes a VT determination routine comprising the steps of: a) computing a first value of ventilatory threshold according to a first approach based on data relating to at least one of the physiological parameters acquired for the exercise session; b) computing a second value of ventilatory threshold according to a different, second approach based on data relating to at least one of the physiological parameters acquired for the exercise session; c) determining a confidence index for each of said first and second values of ventilatory threshold, wherein said confidence index reflects at least one of the detectability of the ventilatory threshold and the matching between the value of ventilatory threshold according to one approach and that according to the other approach.

First claim

The invention claimed is:

1. A method of determining a ventilatory threshold (VT) of a subject during an exercise session, said method comprising the steps of:
acquiring data relating to physiological parameters of said subject and storing said data as a function of time during said exercise session, said data including at least data acquired from a respiration sensor configured to monitor parameters relating to the respiration of said subject during said exercise session, and from a sensor configured to extract parameters relating to the heart beat pulses and/or heart beat rate of said subject during said exercise session;
executing a VT determination routine at periodic time intervals during said exercise session to detect a ventilatory threshold, the routine comprising the steps of:
a) computing a first value of ventilatory threshold according to a first approach based on data relating to at least one of the physiological parameters acquired for said exercise session;
b) computing a second value of ventilatory threshold according to a different, second approach based on data relating to at least one of the physiological parameters acquired for said exercise session;
c) determining a confidence index for each of said first and second values of ventilatory threshold, wherein said confidence index reflects at least one of the detectability of the ventilatory threshold, and the matching between the value of ventilatory threshold according to one approach and that according to the other approach;
wherein the confidence index for said first approach and/or second approach further depends on a matching with earlier calculated values of ventilatory threshold according to the same approach for the same exercise session; and
(d) selecting one of the values of ventilatory threshold as a most reliable ventilatory threshold based on its respective confidence index.

2. The method according to claim 1 , wherein said step of executing said VT determination routine is performed at periodic time intervals during said exercise session so as to provide a real-time determination of the VT during the exercise session.

3. The method according to claim 2 , wherein for each iteration of said VT determination routine, the value of ventilatory threshold having the greatest confidence index is retained.

4. The method according to claim 3 , wherein said retained value of ventilatory threshold is displayed with the corresponding confidence index, said value of ventilatory threshold being expressed as a time and/or heart beat rate.

5. The method according to claim 1 , wherein said matching between two approaches is assessed based on the ratio:

VTi
-
VTo

VTi

where VTi is the ventilatory threshold according to the current approach, and VTo is the ventilatory threshold according to the other approach.

6. The method according to claim 1 , wherein said matching with earlier calculated values of ventilatory threshold according to the same approach for the same exercise session is determined based on the formula:

1

n
-
1

⁢

∑

i
=
1

n
-
1

⁢

α
i

⁢



VT
n

-

VT
i



where VTn is the value determined during the current iteration of the VT determination routine and VTi represents the (n−1) VT values determined earlier during the exercise session and α i is a coefficient related to the corresponding confidence index.

7. The method according to claim 1 , wherein the confidence index for said first approach and/or second approach further depends one or more of:
the number of available data for calculation in each approach;
the sum of residuals and the dispersion of the data after filtering;
the probability of perturbation due to a warm-up threshold;
the matching with statistical data of ventilatory threshold.

8. The method according to claim 1 , wherein said first ventilatory threshold (VT 1 ) is determined, according to said first approach, from data representative of ventilation vs. heart beat rate, as the breakpoint at which ventilation starts increasing more rapidly.

9. The method according to claim 1 , wherein said second ventilatory threshold (VT 2 ) is determined, according to said second approach, from data representative of ventilation vs. time, as the breakpoint at which the ventilation starts increasing more rapidly.

10. The method according to claim 1 , wherein said ventilatory threshold is determined as a breakpoint at the intersection of an aerobic line with an anaerobic line fitting the data; and said detectability of the ventilation threshold is based on the ratio of the slope of the anaerobic line over the slope of the aerobic line.

11. The method according to claim 1 , wherein said respiration data reflect the breathing volume and frequency of the subject as measured by a respiration sensor worn by the subject.

12. The method according to claim 11 , wherein said respiration sensor comprises a chest sensor comprising an elongation sensor integrated in an expandable belt encircling the subject's chest;
and an abdominal sensor comprising an elongation sensor integrated in an expandable belt encircling the upper abdominal region of the subject.

13. The method according to claim 12 , wherein the breathing volume is estimated on the basis of the sum of the peak to valley amplitudes of the chest and abdominal sensor signals.

14. The method according to claim 1 , wherein the ventilation vs. time data are processed in order to eliminate data corresponding to possible recovery and stable periods of the exercise session and keep growing trends; and the second ventilatory threshold (VT 2 ) is determined from the resulting data representing the incremental effort best fitting the whole exercise, as the breakpoint at which the ventilation starts increasing more rapidly.

15. The method according to claim 1 , wherein, in accordance with a third approach, a third ventilatory threshold (VT 3 ) is determined based on statistical data; and a corresponding confidence index is determined.

16. The method according to claim 15 , wherein the determination of said third ventilatory threshold (VT 3 ) further takes into account previous values of ventilatory threshold for the subject determined in prior exercise sessions.

17. The method according to claim 15 , wherein the confidence index of said first and second approaches reflect the matching with said third ventilatory threshold (VT

Assignees

• Iee Sa

Inventors

• Jouanique-Dubuis Cecile
• Stifter Thomas
• Lu-Dac Mathieu
• Lemoine Franck
• Bour Christian

Classifications

• A61B5/4866 Primary

  Evaluating metabolism (using breath test A61B5/083) · CPC title

• A61B5/0833

  Measuring rate of oxygen consumption · CPC title

• A61B5/6823

  Trunk, e.g., chest, back, abdomen, hip · CPC title

• A61B5/091

  Measuring volume of inspired or expired gases, e.g. to determine lung capacity · CPC title

• A61B5/0816

  Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00) · CPC title