Procedure for deriving reliable information on respiratory activity from heart period measurement
The present invention describes a method of tracking minute ventilation from R-R intervals that are based on the acquisition of ECG signal. Sub-methods (RDF 1 ), which are mainly based on heart rate variability, are used, wherein the respiratory frequency is determined from a pattern of rhythmic changes in heart beat data. The sub-methods (RDF 1 -n) are combined using an expert function, wherein each sub-method (RDF 1 -n) determines an estimate of the respiratory frequency.
1. A method for deriving reliable information on respiratory activity from a pattern of rhythmic changes in heart beat data, the method comprising the steps of:
measuring an electrocardiographic (ECG)-signal;
obtaining RR-interval data from the ECG-signal;
calculating respiratory frequency estimates from the RR-interval data using two or more sub-methods, at least one sub-method being based on heart rate variability;
combining the calculated respiratory frequency estimates in a health apparatus using an expert function including a weight vector across frequencies for each frequency estimate and obtaining a resulting respiratory frequency estimate directly in the combination made by said expert function.
2. Method according to claim 1 , characterized in that one sub-method is optimal for a steady condition.
3. Method according to claim 1 , characterized in that at least one sub-method comprises determination of temporal changes in the respiratory frequencies by defining temporal deviations in the distribution of frequencies.
4. Method according to claim 1 , characterized in that post-correction of the respiratory period is made with a chosen method.
5. Method according to claim 1 , characterized in that an expert function comprises a reliability weightings for each sub-method as a function of the calculated respiratory frequency by the respective sub-method.
6. Method according to claim 1 , characterized in that at least one sub-method is controlled dynamically according to the heart rate level.
7. Method according to claim 1 , characterized in that the expert function makes a pre-selection from several different sub-methods with pre-selected criteria.
8. Method according to claim 7 , characterized in that the expert function makes a fixed pre-selection for an implementation according to pre-measured empirical data.
9. Method according to claim 1 , characterized in that information on tidal volume is calculated using information on RR-interval data.
10. Method according to claim 9 , characterized in that information on the ventilation from the heart beat data is derived wherein the following methods (a-c) are used:
a. Multiplying heart beat derived values of tidal volume with heart beat derived values on the frequency of breathing,
b. Applying information on at least one chosen parameter derived from the heart beat,
c. Using a mathematical function to transfer the chosen parameters measures into information on ventilation.
11. Method according to claim 1 , characterized in that the method is used in a wearable computer.
12. Method according to claim 1 , characterized in that the method is used in a fitness exercise equipment.
13. Method according to claim 1 , characterized in that the reliability of the estimate is determined and expressed with the estimate.
14. Method according to claim 1 , characterized in that the resulting respiratory frequency is used to determine oxygen consumption.
15. Method according to claim 1 , characterized in that the resulting respirator frequency is used to determine caloric consumption.
16. Method according to claim 1 , characterized in that the resulting respiratory frequency is used to determine threshold values for energy metabolism.