System and method for determining an adaptive physiological strain index
View Patent ↗The invention in at least one embodiment includes a system and method for detecting and evaluating an adaptive physiological strain index (aPSI) of an individual with a processor and in a further embodiment taking into account the fitness, age and clothing of the individual based upon physiology. The invention in at least one embodiment includes a system and method to calculate the aPSI using physiological measures. In at least one embodiment, the method obtains an individual's skin temperature and heart rate in order to calculate the individual's aPSI.
1. A system for generating an adaptive physiological strain index (aPSI), the system comprising:
at least one heart rate sensor configured to be attached to or placed on a person;
at least one temperature sensor configured to detect a skin temperature of the person; and
a processor in electrical communication with the at least one temperature sensor and the at least one heart rate sensor, the processor configured to produce an aPSI score for the person using a heart rate from the at least one heart rate sensor and an adaptive maximum body temperature based on a critical temperature and a temperature gradient between the skin temperature from the at least one temperature sensor and a body core temperature determined based on the heart rate from the at least one heart rate sensor, and
wherein the heart rate is used without signal analysis by the processor.
2. The system of claim 1 , further comprising a data storage configured to store data related to an age of the person, a body core temperature at rest, and a heart rate at rest; and
wherein the processor calculating the aPSI score based on the following equations:
aPSI
=
5
(
CT
t
-
CT
rest
CT
critical
-
CT
rest
)
+
5
(
HR
t
-
HR
rest
HR
critical
-
HR
rest
)
HR
critical
=
0.90
(
220
-
age
)
CT
critical
=
39.5
°
C
.
+
(
CT
t
-
ST
t
)
-
4
4
where CT t is the body core temperature at a time t, CT rest is the body core temperature at rest, HR t is the heart rate at a time t, HR rest is the heart rate at rest, HR critical is a maximum heart rate, CT critical is the adaptive maximum body temperature, ST is the skin temperature, and the critical temperature is set at 39.5° C.
3. The system according to claim 1 , wherein the processor configured to produce a new calculated aPSI score at predetermined intervals based on variances in at least one of the skin temperatures and the heart rates received by the processor.
4. The system according to claim 1 , further comprising a timer circuit in communication with the processor, and
wherein the processor configured to produce a new calculated aPSI score based on calculating at least one first aPSI score at an initial time designation of a timer circuit and calculating one new calculated aPSI score at each predetermined time interval as provided by the timer circuit.
5. The system according to claim 4 , further comprising an accelerometer in communication with the processor; and
wherein the processor is configured to detect at least one of a resting heart rate and a resting skin temperature of the person when a plurality of signals from the accelerometer remain below a predetermined threshold for a predetermined time period and/or substantially remain below the predetermined threshold for the predetermined time period, and
the processor further configured to determine a resting body core temperature for the person based on the resting heart rate.
6. The system according to claim 1 , wherein the processor calculates the body core temperature using a Kalman filter or an extended Kalman filter.
7. The system according to claim 1 , further comprising a display in communication with the processor to display the aPSI score produced by the processor.
8. The system according to claim 1 , further comprising an alarm in communication with the processor,
wherein the processor is configured to produce an alert signal to the alarm when the aPSI score exceeds a predetermined aPSI score threshold.
9. A method for generating an adaptive physiological strain index (aPSI) from at least one body core temperature and heart rate for an individual, the method comprising:
receiving by a processor a heart rate signal from a heart rate sensor detecting a heart rate of the individual;
receiving by the processor a skin temperature reading from a temperature sensor detecting a skin temperature of the individual;
calculating with the processor the body core temperature for the individual based on the heart rate signal;
calculating with the processor an adaptive maximum body temperature based on a critical temperature and a temperature gradient between the skin temperature reading and the body core temperature;
calculating with the processor the aPSI score for the individual using the body core temperature, the adaptive maximum body temperature and the heart rate signal; and
producing the aPSI score from the processor.
10. The method of claim 9 , further comprising receiving the individual's age from at least one of an input device, memory, database, or data storage, wherein the individual's age data can be accessed by the processor, and
wherein calculating the aPSI score is based on the processor calculating the aPSI score based on the following equations:
aPSI
=
5
(
CT
t
-
CT
rest
CT
critical
-
CT
rest
)
+
5
(
HR
t
-
HR
rest
HR
critical
-
HR
rest
)
HR
critical
=
0.90
(
220
-
age
)
CT
critical
=
39.5
°
C
.
+
(
CT
t
-
ST
t
)
-
4
4
where CT t is a body core temperature at a time t, CT rest is a body core temperature at rest, HR t is the heart rate at a time t, HR rest is a heart rate at rest, HR critical is a maximum heart rate, CT critical is the adaptive maximum body temperature, ST is the skin temperature, and the critical temperature is set at 39.5° C.
11. The method of claim 9 , wherein calculating with the processor the body core temperature uses a Kalman filter or an extended Kalman filter.
12. The method of claim 9 , further comprising adjusting by the processor the aPSI score based on at least one of a fitness level, an age, a maximum heart rate, or a resting heart rate of the individual.
13. The method of claim 9 , further comprising calculating a new aPSI score with the processor at predetermined time intervals or at predetermined intervals based on at least one of variances in the body core temperatures from the temperature sensor and the heart rates from the heart rate signal from the heart rate sensor.
14. The system according to claim 1 , further comprising:
a memory for storing at least a resting heart rate for the person, and the memory is in electrical communication with the processor;
wherein the processor configured to produce an updated aPSI score for the person based on a current skin temperature, the resting heart rate, and a current heart rate where a current body core temperature is calculated based on the heart rate information and time since initiation of the monitoring.
15. The system according to claim 14 , using a person specific critical heart rate for the person while using the following equations:
aPSI
=
5
(
CT
t
-
CT
rest
CT
critical
-
CT
rest
)
+
5
(
HR
t
-
HR
rest
HR
critical
-
HR
rest
)
HR
critical
=
0.90
(
220
-
age
)
CT
critical
=
39.5
°
C
.
+
(
CT
t
-
ST
t
)
-
4
4
where CT t is the body core temperature at a time t, CT rest is the body core temperature at rest, HR t is the heart rate at a time t, HR rest is the heart rate at rest, HR critical is the person specific critical heart rate, CT critical is the adaptive maximum body temperature, ST is the skin temperature, the critical temperature is set at 39.5° C.
16. The system according to claim 1 , further comprising:
at least one internal temperature sensor configured to be internal to the person's skin;
wherein the processor configured to produce an updated aPSI score for the person based on a current skin temperature from the at least one skin temperature sensor, the resting heart rate from a memory, a current heart rate from the at least one heart rate sensor, and the body core temperature from the internal temperature sensor.
17. The method according to claim 9 , wherein for generating the aPSI from the skin temperature, the body core temperature and the heart rate, the method comprising:
when one of the skin temperature and a heart rate from the heart rate signal is unavailable, using a previously stored value or calculating a value for the unavailable skin temperature or the unavailable heart rate.
18. The method according to claim 9 , wherein calculating the aPSI score for the individual is based on the skin temperature reading received from the temperature sensor, a resting heart rate, the heart rate signal received from the heart rate sensor, and the body core temperature calculated based on the heart rate signal.
19. The system according to claim 1 , wherein the processor produces a current aPSI score for the person based on a current skin temperature from the temperature sensor, a resting heart rate, a current heart rate from the heart rate sensor, a current body core temperature calculated based on the current heart rate, and a resting body core temperature calculated based on the resting heart rate.
20. A system for generating an adaptive physiological strain index (aPSI), the system comprising:
at least one heart rate sensor configured to be attached to or placed on a person;
at least one temperature sensor configured to detect a skin temperature of the person; and
a processor in electrical communication with the at least one temperature sensor and the at least one heart rate sensor, the processor configured to produce an aPSI score for the person using
a heart rate from the at least one heart rate sensor and
an adaptive maximum body temperature based on
a temperature gradient between the skin temperature from the at least one temperature sensor and a body core temperature determined based on the heart rate from the at least one heart rate sensor, and
a critical temperature, and
wherein the heart rate is used without signal analysis by the processor, and
wherein an adaptive characteristic of the aPSI is varying the adaptive maximum body temperature based on variances of the temperature gradient between the skin temperature and the body core temperature over time.
21. The system according to claim 20 , wherein the critical temperature provides an anchor around which the adaptive maximum body temperature varies based on a size of the temperature gradient.