Patent Publication Number: US-2023148878-A1

Title: System And Method for Determining an Adaptive Physiological Strain Index

Description:
This patent application is a continuation application from U.S. patent application Ser. No. 16/072,815, filed on Jul. 25, 2018, which is a 371 National Stage application from International Application No. PCT/US2017/027985, filed on Apr. 17, 2017, which claims priority to and the benefit of U.S. Patent Application No. 62/323,268 filed on Apr. 15, 2016, both of which are hereby incorporated by reference. 
    
    
     I. FIELD OF THE INVENTION 
     This invention in at least one embodiment relates to determining an adaptive physiological strain index (aPSI) using a body core temperature, a skin temperature, and a heart rate of an individual. 
     II. BACKGROUND OF THE INVENTION 
     Hot environments pose a risk of heat illness to people in occupations where heavy workloads and/or protective clothing ensembles are necessary. Excessive heat strain can lead to collapse or even death. Heat-related illness (HRI) has a spectrum of disorders due to environmental heat exposure and includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke. 
     HRI is an ever present threat to athletes, military personnel, and occupational hazard workers, as the combination of physical exertion in hot environments makes individuals susceptible to heat stroke, heat exhaustion, and heat cramps. HRI prevention includes avoiding medications that can increase the risk of heat illness (e.g., antihypertensives, diuretics, and anticholinergics), gradual adjustment to heat, and sufficient fluids and electrolytes. Mild HRI can be treated by drinking fluids. In more significant HRI cases, spraying with mist and using a fan is useful. For those with severe HRI putting them in lukewarm to cold water is recommended if possible with transport to a hospital. 
     Efforts to identify and control the incidence of heat illness/injury originally focused on identifying high risk environments and modifying work/rest schedules. Although the risk of heat illness can be reduced by acclimation, appropriate work rest schedules, and proper hydration, the risk is never entirely abated when there is heavy exertion in a hot environment. 
     Assessing risk of heat stress from environmental conditions alone fails to account for individual differences, such as acclimation status, fitness, body composition and morphology, prior heat injury, (which can play a role in an individual&#39;s response to working in hot environments) and clothing. 
     Personal physiological monitoring is one means of overcoming the limitations of assessing heat strain using environment monitoring alone. Modern physiological monitoring systems are becoming more common for monitoring applications; however, while a number of physiological strain indices can be computed from a number of different physiological variables none to date take account of the interplay between an individual&#39;s age, fitness, and personal protective equipment being worn. 
     III. SUMMARY OF THE INVENTION 
     By combining physiological measures into a single adaptive index of physiological strain (aPSI) it is possible to provide an assessment of risk of HRI to an individual being monitored. 
     In at least one embodiment, a system for generating an adaptive physiological strain index (aPSI) where the system includes: 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 processer configured to produce an aPSI score for the person using 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. 
     In at least one embodiment, a system for detecting aPSI for a person (or individual) where the system includes: a heart rate means for detecting a heart rate of a person; a temperature means for detecting a skin temperature of the person; an input means for receiving a person&#39;s age; a calculation means for producing an aPSI score for the person based on the detected skin temperature, the detected heart rate, the received input age, and temperature gradient between the detected skin temperature and a body core temperature calculated based on the detected heart rate; and storage means for storing heart rates from the heart rate means, skin temperatures from the temperature means, and body core temperatures from the calculation means. 
     In at least one embodiment, a system includes: at least one temperature sensor configured to be attached to an individual&#39;s skin; at least one heart rate sensor configured to be attached to the individual; a memory for storing at least a resting heart rate for the individual; a processor in electrical communication with the at least one temperature sensor and the at least one heart rate monitor, the processor configured to produce aPSI score for the individual based on the current skin temperature, the resting heart rate, and the current heart rate where the body core temperature is calculated based on the heart rate information and time since initiation of the monitoring, or the body core temperature is obtained from an internal temperature sensor in the individual. 
     In at least one embodiment, a system includes: at least one skin temperature sensor configured to be attached to an individual&#39;s skin; at least one heart rate sensor configured to be attached to the individual; at least one internal temperature sensor configured to be internal to the individual&#39;s skin; a memory for storing at least a resting heart rate for the individual; a processor in electrical communication with the at least one temperature sensor and the at least one heart rate monitor, the processor configured to produce aPSI score for the individual based on the current skin temperature from the at least one skin temperature sensor, the resting heart rate from the memory, the current heart rate from the at least one heart rate sensor, and the body core temperature from the internal temperature sensor. 
     Further to any of the above embodiments, the system further includes a data storage configured to store data related to an age of the person; and where the processor calculating the aPSI score based on the following equation: 
     
       
         
           
             aPSI 
             = 
             
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         CT 
                         t 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                     
                       
                         CT 
                         critical 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                   
                   ) 
                 
               
               + 
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         HR 
                         t 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                     
                       
                         HR 
                         critical 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               HR 
               critical 
             
             = 
             
               0.9 
               
                 ( 
                 
                   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 a maximum body temperature, and ST is the skin temperature. Further to the previous embodiment, the processor adjusts the aPSI score based on at least one of a fitness level, an age, a maximum heart rate, and a resting heart rate of an individual. Further to the previous two embodiments, wherein the aPSI score is recalculated at predetermined intervals when a variance is detected in at least one of the detected skin temperature and the detected heart rate. Further to the previous three embodiments, the equation uses an individual specific heart rate critical for the individual while using the following equations: 
     
       
         
           
             aPSI 
             = 
             
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         CT 
                         t 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                     
                       
                         CT 
                         critical 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                   
                   ) 
                 
               
               + 
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         HR 
                         t 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                     
                       
                         HR 
                         critical 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               CT 
               critical 
             
             = 
             
               39.5 
               ° 
               ⁢ 
                   
               
                 C 
                 . 
                 
                   + 
                   
                     
                       
                         ( 
                         
                           
                             CT 
                             t 
                           
                           - 
                           
                             ST 
                             t 
                           
                         
                         ) 
                       
                       - 
                       4 
                     
                     4 
                   
                 
               
             
           
         
       
     
     Further to any of the above embodiments, where the processor configured to produce a new calculated aPSI score at predetermined intervals based on variances in at least one of the skin temperature and the heart rate received by the processor. Further to any of the above embodiments, the system further including a timer circuit in communication with the processor, and where 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 a new aPSI score at predetermined time intervals as provided by the timer circuit. Further to the previous embodiment, the system further includes an accelerometer in communication with the processor; and where the processor is configured to detect at least one of a resting heart rate and a resting skin temperature of the individual when a plurality of signals from the accelerometer remained below a predetermined threshold for a predetermined time period and/or substantially remained below the predetermined threshold for the predetermined time period, and the processor further configured to determine a resting body core temperature for the individual based on the resting heart rate. 
     Further to any of the above embodiments, where the processor calculates the body core temperature using a Kalman filter or an extended Kalman filter. Further to any of the above embodiments, the system including a display in communication with the processor to display the calculated aPSI index produced by the processor. Further to any of the above embodiments, the system including an alarm in communication with the processor. Further to the previous embodiment, the processor is configured to produce an alert signal to the alarm when the calculated aPSI score exceeds a predetermined aPSI score threshold. Further to any of the above embodiments, the system is housed in a wearable device. 
     In at least one embodiment, a method for generating an adaptive physiological strain index (aPSI) from a body temperature and heart rate for an individual, the method includes: 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 a body core temperature for the individual based on the heart rate signal; calculating with the processor a temperature gradient between the skin temperature reading and the body core temperature; calculating with the processor an aPSI score for the individual using the body core temperature, the temperature gradient and the heart rate signal; and producing the calculated aPSI score from the processor. 
     In at least one embodiment, a method for generating an adaptive physiological strain index (aPSI) from a skin temperature, a body core temperature and a heart rate, the method includes: receiving by a processor a heart rate signal from a heart rate sensor; receiving by the processor a skin temperature reading from a skin temperature sensor; receiving by the processor a body core temperature from an internal temperature sensor; calculating with the processor a temperature gradient between the skin temperature reading and the body core temperature reading; calculating with the processor an aPSI score for the person using the body core temperature, the temperature gradient and the heart rate signal; and producing the calculated aPSI score from the processor, and when one of the physiological readings is unavailable, using a previously stored value or calculating a value for the physiological reading. 
     According to either of the above method embodiments, the method further includes receiving the individual&#39;s age from at least one of an input device, memory, database, or data storage, wherein the person&#39;s age data can be accessed by the processor. Further to the previous embodiment, where calculating the aPSI score is based on said processor calculating the aPSI score based on the following equation: 
     
       
         
           
             aPSI 
             = 
             
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         CT 
                         t 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                     
                       
                         CT 
                         critical 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                   
                   ) 
                 
               
               + 
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         HR 
                         t 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                     
                       
                         HR 
                         critical 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               HR 
               critical 
             
             = 
             
               0.9 
               
                 ( 
                 
                   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, and CT critical  is a maximum body temperature. 
     According to any of the above method embodiments, the method further includes calculating by the processor the body core temperature based on a Kalman filter or an extended Kalman filter. According to any of the above method embodiments, the method further includes when the received body temperature exceeds a predetermined threshold, generating an alert signal by the processor for an alarm. According to any of the above method embodiments, the method further includes 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. According to any of the above method embodiments, the method further includes said processor configured to produce a new calculated aPSI score at predetermined intervals based on at least one of variances in the detected body temperature by the temperature sensor and the detected heart rate by the heart rate sensor. According to any of the above method embodiments, the method further includes calculating with the processor new calculated aPSI scores at predetermined time intervals. 
    
    
     
       IV. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a method according to one embodiment of the system. 
         FIG.  2    illustrates a system according to at least one embodiment of the invention. 
         FIG.  3    illustrates a system according to at least one embodiment of the invention. 
         FIG.  4    illustrates a system according to at least one embodiment of the invention. 
         FIG.  5    illustrates a system according to at least one embodiment of the invention. 
         FIG.  6    illustrates a system according to at least one embodiment of the invention. 
         FIG.  7    illustrates a computer program product and computer implementation according to at least one embodiment of the invention. 
     
    
    
     V. DETAILED DESCRIPTION OF THE DRAWINGS 
     The invention in at least one embodiment includes a system and a method to calculate an index of heat strain (e.g., 0=no strain, 9=very high strain) using physiological measures. Prior indices did not include an ability for application to different populations, different work, and/or protective clothing environments. Table 1 shows the original PSI levels and the associated levels of thermal work strain according to Moran et al. (1998): 
                                 TABLE 1                       PSI   Strain                                                    0               1   No/Little           2               3   Low           4               5   Moderate           6               7   High           8               9   Very High           10                        
It has been found in the past that it is possible to exceed a PSI of 10 under certain circumstances. The above table is relevant for at least one of the disclosed embodiments, the adaptive physiological strain index (“aPSI” or “adaptive PSI”) provides a strain index score between 0 and 10 that takes into account the conditioning of the individual, the environment they are in, and the clothing they are wearing while being monitored. Existing systems would have a marathon runner having a high PSI (e.g., 11 or 12) compared to an individual wearing a fully enclosed Hazmat suit having a lower PSI (e.g.,  7 . 5 ). An observer would deem the Hazmat suit individual being under more strain than the marathon runner. In at least one embodiment, this invention addresses this inaccuracy.
 
     In at least one embodiment, a system and/or a method is provided to use an individual&#39;s body core temperature in connection with their heart rate and skin temperature to determine their aPSI. The invention in at least one embodiment includes a method for detecting and evaluating the aPSI of the individual with a processor having suitable programming to perform the functions discussed in this disclosure. In at least one embodiment, the relationship between the body core temperature and heart rate is a quadratic relationship that varies over a range of heart rate measurements, where in at least one embodiment the range is between 50 and 180 beats/minute, and in a further embodiment, the maximum heart rate is set to 220 minus the person&#39;s age with a corresponding quadratic relationship. In a further embodiment, the system and method use a Kalman filter model or an extended Kalman filter to determine the body core temperature. In at least one embodiment, the system and method calculate and adjust for external factors that may influence the adaptive physiological strain index, such as the environment, clothing, physical fitness, and the person&#39;s age or weight. 
       FIG.  1    illustrates a method for operation of at least one system embodiment like those illustrated in  FIGS.  2 - 6   . A processor  210  receives the individual&#39;s age from a data source,  102 . Examples of how the individual&#39;s age can be received include: 1) the individual providing his/her age is received through an input device such as a keyboard or other data entry mechanism including virtual versions; 2) retrieval of stored data about the individual; and 3) a combination of the previous two examples. In an alternative embodiment, this step is omitted from the method. In an alternate embodiment, the resting physiological information is provided in a similar manner at least as a starting point. 
     The processor  210  receives a skin temperature from at least one temperature sensor  230 ,  104 . The processor  210  receives a measured heart rate from a heart rate sensor  220 ,  106 . In at least one embodiment, there is one component that provides the skin temperature and the individual&#39;s heart rate. In at least one alternative embodiment, the processor sends a request for the person&#39;s skin temperature and/or heart rate to the appropriate sensor(s) for a reading instead of a continual data feed from these sensors. 
     In at least one embodiment, steps  102  through  106  can be performed in a different order and/or substantially simultaneous or substantially concurrently with each other. 
     The processor  210  calculates the aPSI score for the individual,  108 . In at least one embodiment, the aPSI score is determined based on a quadratic calculation of the values of at least one of received skin temperature, the received heart rate, and the received age of the individual. In at least one embodiment, the aPSI score is calculated using a critical body core temperature that is based on a temperature gradient between the resting body core temperature, which is calculated based on the heart rate in at least one embodiment, and the skin temperature. 
     In at least one embodiment, the body core temperature is calculated in a multi-step process using an extended Kalman filter as discussed in U.S. Pat. App. Pub. No. US-2014-0180027-A1, which is hereby incorporated by reference. In a further embodiment, the processor can produce the body core temperature for the individual using a number of factors for an individual based on physical characteristics such as height, weight, and age. In at least one embodiment, using any known way to estimate a body core temperature including using any combination of skin temperature, physiological data, accelerometer data, environmental information, and clothing information. 
     The processor then provides the calculated aPSI score,  110 . The calculated aPSI score may be provided to a display, a memory, a transmission system for relaying to an external device or system, and an alarm. The aPSI provides an improved indication of the current physiological strain of the individual being monitored, and would allow for an activity or pace change by the individual, if possible, to lower the physiological strain. 
     Repeating the receiving ( 104  and  106 ), calculating ( 108 ) and providing ( 110 ) steps at predetermined intervals,  112 . Examples of predetermined intervals include 30 second intervals, 1 minute intervals, 2 minute intervals, 5 minute intervals, and 10 minute intervals, and hour intervals. In a further embodiment, the method includes setting or selecting the predetermined interval prior to calculating the aPSI score. In at least one further embodiment, a timer (or timer circuit or timing circuit)  340  illustrated in  FIG.  3    can be used to delay the repeat cycle after calculating each aPSI score. In at least one embodiment, the aPSI score is calculated at variable times based on a change in the detected temperature, the heart rate that exceeds a predetermined threshold, the rate of change at least one physiological signal (e.g., skin temperature or heart rate) over a predetermined change time, or a combination of these. 
     In at least one further embodiment, when the aPSI score exceeds a predetermined alarm threshold, an alert is generated by an alarm  450  of  FIG.  4   . In at least one embodiment, the processor  210  provides an alarm signal to the alarm  450  that triggers the alert. 
     In a further embodiment illustrated in  FIG.  5   , the system includes at least one accelerometer  555  to monitor activity of the individual to facilitate obtaining resting physiological information about the individual such as resting body core temperature (CT rest ) and resting heart rate (HR rest ) and in other embodiments, the skin temperature. The illustrated system also includes the timer circuit  340 . The processor  210  is in electrical communication with the timer circuit  340  and the accelerometer  555  to detect when the accelerometer  555  signal(s) are below a predetermined threshold for a predetermined time based on a time signal from the timer circuit  340 . 
     In at least one embodiment, when the accelerometer signal(s) decreases below the predetermined threshold, the processor  210  stores the current time data in memory for later comparison or alternatively begins a counter that is incremented based on the time signal. Under the comparison embodiment, when the current time data is greater than the stored time data by the predetermined time, the processor  210  pulls and/or processes the signal from the heart rate sensor  220  to obtain the resting heart rate, which then is used to determine the resting body core temperature. Under the counter embodiment, the processor  210  increments the counter based on the time signal until it matches and/or exceeds the predetermined time before pulling and/or processing the signal from the heart rate sensor  220 . 
     In a further embodiment, when the accelerometer signal(s) exceeds the predetermined threshold momentarily before decreasing below, the time does not reset. In such a situation, the accelerometer signal(s) has substantially remained below the predetermined threshold. 
     In at least one embodiment, the predetermined time is 20 minutes, 25 minutes, 30 minutes, 35 minutes, etc. In an alternative embodiment, the predetermined time is shorter such as 10 minutes or 15 minutes, and the processor  210  compares the heart rate signal starting at the predetermined time to follow-on recordings while the accelerometer signal(s) remains below the predetermined threshold to determine whether the heart rate signal has stabilized. Stabilized as used in this disclosure means that the signal level falls within a range set in the processor  210  for the physiological characteristic being monitored. 
     Using any of the previously mentioned variables, the modified and adaptive PSI includes an ability for application to different populations, different work, diverse age ranges, and/or protective clothing environments. The equation for the adaptive PSI score in at least one embodiment is as follows: 
     
       
         
           
             aPSI 
             = 
             
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         CT 
                         t 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                     
                       
                         CT 
                         critical 
                       
                       - 
                       
                         CT 
                         rest 
                       
                     
                   
                   ) 
                 
               
               + 
               
                 5 
                 ⁢ 
                 
                   ( 
                   
                     
                       
                         HR 
                         t 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                     
                       
                         HR 
                         critical 
                       
                       - 
                       
                         HR 
                         rest 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               HR 
               critical 
             
             = 
             
               0.9 
               
                 ( 
                 
                   220 
                   - 
                   age 
                 
                 ) 
               
             
           
         
       
       
         
           
             
               CT 
               critical 
             
             = 
             
               39.5 
               + 
               
                 
                   
                     ( 
                     
                       
                         CT 
                         t 
                       
                       - 
                       
                         ST 
                         t 
                       
                     
                     ) 
                   
                   - 
                   4 
                 
                 4 
               
             
           
         
       
     
     In the adaptive PSI equation, the CT t  is the body core temperature at a time t, CT rest  is the body core temperature at rest, HR t  is heart rate at a time t, and the HR rest  is heart rate at rest, the HR critical  is a critical maximal heart rate threshold used to determine a maximal aPSI. In at least one embodiment the HR critical  in the adaptive PSI equation has a value as 90% of HR max  as suggested by the American College of Sports Medicine Guidelines (America College 1991) and also includes the variable (220-age) for the HR critical  value to be configured to apply to individuals of any age. In an alternate embodiment, the HR critical  can be set as 90% of HR max  derived from a VO 2  max test. In at least one embodiment, the HR critical  is determined for the particular person based on previous physiological measurements. 
     The adaptive PSI equation also includes CT critical  as the critical body core temperature which is adapted in real-time based on a body core temperature (CT t ), a skin temperature (ST t ), and a critical temperature such as 39.5° C. During activity the CT critical  will vary based on a temperature gradient between the current core temperature and the current skin temperature. 
     In at least one embodiment, the method and system are able to adapt to constraints on available physiological data for use. 
     In the case of resting body core temperature and resting heart rate, the values used may be preset, entered by the individual or another person as discussed previously, or based on physiological measurements taken at rest. When the resting body core temperature is not available, then it may be set to 37.1° C. or calculated from the resting heart rate using, for example, a Kalman filter or an extended Kalman filter or other similar estimation for body core temperature based on heart rate. When the resting heart rate is not available, then it may be set at 71 beats per minute. In at least one embodiment, the system is prompted to take the current heart rate by a user or the individual to establish the individual&#39;s resting heart rate. 
     In at least one embodiment, the critical heart rate (HR critical ) is set to 180 beats per minute. In other embodiments, it is set based on the individual&#39;s age using the equation above or is obtained from another source for this specific individual based on physiological testing. 
     When the skin temperature is unavailable, the skin temperature is set to body core temperature minus four degrees Celsius in at least one embodiment. In at least one further embodiment, the critical body core temperature (CT critical ) is set based on the clothing being worn by the individual. In a further embodiment, CT critical  is set as follows: 
                     TABLE 2               CT critical  Values based on Clothing                                                Full Encapsulation in PPE   about 38.5° C. or less           Long Sleeves and Pants   about 39.5° C. or less           Shorts and T-shirt   about 40.0° C.           Default Setting   39.5° C.                        
As discussed above, CT critical  may be set pursuant to the equation above when the resting body core temperature and the skin temperature are known. In a further embodiment, the skin temperature is modified based on the location of the sensor used to obtain the skin temperature to take into account the gradient that is present on an individual&#39;s skin based on body location.
 
     In other embodiments, where just the heart rate is available for the individual (for example, if the skin temperature sensor is omitted or not providing data), the body core temperature is calculated from the heart rate and CT critical  is set to 39.5° C. When heart rate and skin temperature are available for the individual, using the equations above and calculating body core temperature from the heart rate. When the embodiment also includes a sensor for body core temperature, then using heart rate and body core temperature to determine the aPSI and taking into account whether skin temperature is available or not and adjusting accordingly using the above-described approaches. 
     In at least one embodiment as illustrated, for example in  FIG.  2   , the methods discussed in connection with  FIG.  1    are performed on the processor  210  running code that enables the performance of at least one method embodiment and is in communication with the heart rate sensor  220  and the temperature sensor  230 . Examples of a heart rate sensor  220  include a heart rate monitor attached to the individual, a processor for receiving EKG signals from electrodes attached to the person, a processor for receiving a photoplethysmogram signal (e.g., a pulse oximeter), or a processor for receiving a ballistic-cardiogram signal. The processor used as part of the heart rate sensor  220  in at least one embodiment is the processor  210 . Examples of a temperature sensor  230  configured to detect a temperature on the exterior of the individual being monitored, such as an expanse of skin, can include various analog and digital temperature sensors, and infrared thermometers. In at least one embodiment, there is a memory, data storage, or storage (not illustrated) in communication with the processor  210 . 
     In at least one embodiment of the previous embodiments, for example as illustrated in  FIG.  3   , there is an optional component of the timer circuit  340  for setting or scheduling the sampling times (or intervals) at which the heart rate is used to calculate the body core temperature. In an alternative embodiment, the predetermined intervals are set by a user or the individual being monitored. In a further alternative embodiment, the predetermined time period is stored in a memory or data storage, for example, on a memory chip located on the user&#39;s wrist, in a database located on a network, or is present in the code running on the processor  210 . The timer circuit  340 , for example, can adjust the sampling intervals for various periods such as 30 second, 1 minute, and 5 minute intervals. The timer circuit  340  can transmit a signal to the processor  210  notifying the processor  210  to perform at least one instruction, such as alerting the processor  210  that a time interval of one minute has occurred. The timer circuit  340  can be an integrated circuit, chip, or microchip used for timing, pulse, and/or oscillator applications. 
     In at least one further embodiment to any of the embodiments as illustrated in  FIG.  4   , the system includes the alarm  450  or another similar component to produce an alert indicating the person being monitored has exceeded an alarm parameter threshold for the aPSI score as calculated by the processor  210 . The alarm  450  can be contained within the system or in communication with the system to produce an alert. The alert can be produced in any sensory form, such as auditory output through a speaker, visual output through a display and/or light elements, and/or a vibration from a transducer, configured to alert the individual or a monitoring system that the PSI parameter threshold has been exceeded. 
     As illustrated in  FIG.  5   , in at least one further embodiment to any of the above embodiments, the system includes a timer circuit  340  and at least one accelerometer  555  in communication with the processor  210 . The accelerometer  555  is configured to provide a signal to the processor  210  based on the individual&#39;s movements that are detected. 
     In a further embodiment to the above embodiments, the system includes a sensor internal to the individual being monitored to measure body core temperature. The sensor is in communication with the processor wirelessly. An example of the internal temperature sensor is a thermometer pill (Jonah Pill, Respironics, Bend, Oreg.) that would be orally ingested. 
     In at least one embodiment, the processor  210 , the heart rate sensor  220 , the temperature sensor  230 , and/or the other described electronics, such as the timer  340 , the alarm  450 , or the accelerometer  555 , embodied in the block diagrams of  FIGS.  2 - 5   , are housed within or attached to an apparatus worn by an individual being monitored, such as on the individual&#39;s chest, arm, or wrist, but is not limited in this regard. 
     In a further embodiment illustrated in  FIG.  6   , the processor  210 , the timer circuit  340 , the alarm  450 , and the accelerometer  555  are present in one housing  690 , such as that provided by a smartphone or smartwatch, in wireless communication with the heart rate sensor  220  and/or the temperature sensor  230 . In a further embodiment or in addition to the previous embodiments, the body core temperature, the heart rate, and/or the aPSI score can be shown on a display present on the wearable device, such as a wrist worn display, a smart telephone, or a heads up display, for viewing by the person being monitored. 
     In at least one embodiment, the processor  210  is detached from the individual being monitored and is located in external equipment such as a medical monitor or a computer implemented device running software according to at least one method embodiment. In such an embodiment, examples of how the information is sent to such external equipment include, but is not limited to, transmitting can be sent wirelessly including optically, or by various types or arrangements of hardwire connections, or combinations thereof. An example of wireless and optical transmissions is through a transmitter and a receiver. In a further embodiment to any of the previous embodiments, the information can be received through, for example, a user interface, such as a keyboard, graphical user interface (e.g., touchscreen) on a display, or a microphone. 
     The information and operations that are transmitted throughout the various described embodiments can be in the form of electronic data, wireless signals, or a variation thereof, for example. In at least one embodiment, the processor  210  can be designed to accomplish signal processing in the configured apparatus containing the sensors and electronics but can transmit signals to a network for further processing. In another embodiment, the processor  210  is connected to a communications circuit  660  to transmit the body core temperature, the skin temperature, the heart rate, and/or the aPSI score to an external system for monitoring and/or display.  FIG.  6    illustrates a communications circuit  660  configured to communicate directly with the external system, such as the communications circuit  660  communicating directly with a smart phone  670 . The information and operations that are transmitted throughout the various embodiments can be sent wirelessly, optically, or by various types or arrangements of hard wire connections, or combinations thereof, among the various system components, for example. 
     In a further embodiment, the system includes one or more means instead of a particular component. 
     A heart rate means for detecting a heart rate includes a sensor for measuring heart beats or blood flow, a heart rate sensor, a heart monitor, or another biotelemetry device configured to detect a heartbeat, heart rate, or blood flow but is not limited in this regard and the means for measuring a heart rate or heart beat can be measured in real time or recorded for later use. 
     In at least one embodiment, a temperature means for measuring the skin temperature can include various manual or digital thermometer and temperature gauges, but is not limited in this regard and additional apparatuses configured to detect heat or temperature can be used. The temperature means can detect skin temperature of an area of a body, such as an area of skin, can include a manual or digital thermometer, a temperature gauge, for example but is not limited in this regard and additional apparatuses configured to detect heat or temperature of an area of a body can be used. 
     An input means for receiving input, such as receiving a user&#39;s age includes a user interface such as a keyboard, graphical user interface (e.g., touchscreen) on a display, or voice recognition interface but is not limited in this regard and can also include receiving data from a device, memory, database, data storage, or apparatus configured to store or transmit data. 
     In at least one embodiment, a calculation means for calculating an aPSI score for the person based on the detected skin temperature, the detected heart rate, the received input age, and temperature gradient between the detected skin temperature and a body core temperature calculated based on the detected heart rate is the processor with suitable programming to perform the steps associated with this function. 
     In an alternative embodiment, the Kalman filter model or the extended Kalman filter model is adjusted for fitness level. In particular, the aPSI score can be adjusted by increasing it for better fitness and decreasing it for lower fitness levels. In a further alternative embodiment, the Kalman filter is adjusted based on age of the person by adjusting the maximum heart rate used in the model to reflect the person&#39;s age. An example of one way to determine maximum heart rate is to use 220 minus the person&#39;s age; however, the maximum heart rate could be determined for the person based on physiological testing prior to use of the heart rate sensor. In at least one embodiment, the maximum heart rate is adjusted to reflect the heart rate for the person while leaving the starting heart rate alone and thereby adjusting the scale of the correlation between the heart rate and the body core temperature. In a further alternative embodiment, any combination of the fitness, age, resting heart rate, and maximum heart rate are used to adapt or fine-tune the aPSI score the monitored individual. 
     As will be appreciated by one skilled in the art based on this disclosure, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, a processor operating with software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this disclosure, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Xcode, Ruby, Python, Java, Smalltalk, Objective C, C++, C#, Transact-SQL, XML, or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including Bluetooth, a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Aspects of the present invention are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute with the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     Referring now to  FIG.  7   , a representative hardware environment for practicing at least one embodiment of the invention is depicted. This schematic drawing illustrates a hardware configuration of an information handling/computer system in accordance with at least one embodiment of the invention. The system comprises at least one processor or central processing unit(s) (CPU)  710 . The CPU(s)  710  are interconnected with system bus  712  to various devices such as a random access memory (RAM)  714 , read-only memory (ROM)  716 , and an input/output (I/O) adapter  718 . The I/O adapter  718  can connect to peripheral devices, such as disk units  711  and tape drives  713 , or other program storage devices that are readable by the system. The system can read the inventive instructions on the program storage devices and follow these instructions to execute the methodology of at least one embodiment of the invention. The system further includes a user interface adapter  719  that connects a keyboard  715 , mouse  717 , speaker  724 , and/or other user interface devices such as a touch screen device  722  to the bus  712  to gather user input. Additionally, a communication adapter  720  connects the bus  712  to a data processing network  725 , and a display adapter  721  connects the bus  712  to a display device  723  which may be embodied as an output device such as a monitor, printer, or transmitter, for example. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, circuit, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the root terms “include” and/or “have”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means plus function elements in the claims below are intended to include any structure, or material, for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. 
     Although the present invention has been described in terms of particular example embodiments, it is not limited to those embodiments. The embodiments, examples, and modifications which would still be encompassed by the invention may be made by those skilled in the art, particularly in light of the foregoing teachings. 
     As used above “substantially,” “generally,” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. It is not intended to be limited to the absolute value or characteristic which it modifies but rather possessing more of the physical or functional characteristic than its opposite, and preferably, approaching or approximating such a physical or functional characteristic. 
     Those skilled in the art will appreciate that various adaptations and modifications of the embodiments described above can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein. 
     VI. INDUSTRIAL APPLICABILITY 
     The disclosed embodiments provide an improved way to detect HRIs based upon an individual&#39;s a PSI taking into account an impact of the clothing worn by the individual. In some embodiments, the systems and methods provide a mechanism to alert the individual of the potential for HRI based on their aPSI.