A six-minute walk test exercise risk assessment method and system based on heart rate recovery and blood oxygen response

Abstract

The application discloses a six-minute walk test exercise risk assessment method and system based on heart rate recovery and blood oxygen response, comprising the following steps: obtaining the heart rate, blood oxygen, walking distance of the tester in the resting and exercise states, and the heart rate at at least one time point after exercise; calculating the heart rate recovery value and blood oxygen drop value, and determining the normalized walking distance index, heart rate response index, heart rate recovery index and blood oxygen drop index respectively; adopting a preset weight to weight-sum the four indexes to obtain an exercise risk index; comparing the exercise risk index with first and second risk threshold values to determine low, medium or high risk, and outputting corresponding instructions; determining the test effectiveness according to the walking speed stability, mid-way pause, turning standard and test duration; and outputting the risk level, effectiveness and exercise intensity suggestion. The application can realize exercise risk grading early warning based on heart rate recovery and blood oxygen response, so as to meet the demand of heart rehabilitation clinic for exercise safety.

Description

Technical Field

[0001] This invention relates to the field of cardiac rehabilitation data processing technology, and in particular to a method and system for assessing exercise risk based on the six-minute walk test using heart rate recovery and blood oxygenation response. Background Technology

[0002] The Six-Minute Walk Test (6MWT) is a simple, economical, and safe method for assessing cardiopulmonary function. It is widely used in patients with cardiovascular disease, chronic obstructive pulmonary disease, and pulmonary hypertension to assess exercise tolerance, evaluate rehabilitation outcomes, and screen for exercise risks. Clinical guidelines explicitly recommend the 6MWT as a core tool for baseline assessment before cardiac rehabilitation and for regular monitoring during rehabilitation.

[0003] During and after the 6MWT trial, changes in several physiological parameters were closely related to exercise risk. Heart Rate Recovery (HRR) refers to the decrease in heart rate from peak exercise heart rate to a specific time point (usually 1 or 3 minutes) after exercise cessation. Abnormal HRR (e.g., a 1-minute HRR of less than 18 beats / min) suggests autonomic dysfunction and decreased cardiac reserve, and is an independent predictor of adverse cardiovascular events. Dynamic decrease in blood oxygen saturation (ΔSpO2) refers to the difference between resting oxygen saturation and the lowest oxygen saturation during exercise. ΔSpO2 ≥ 4% often indicates exercise-induced hypoxemia and is significantly associated with poor exercise tolerance, arrhythmias, and long-term mortality risk. Therefore, combining HRR and ΔSpO2 for exercise risk assessment has clear clinical significance.

[0004] Currently, clinically used six-minute walk test devices and wearable monitoring devices (such as fitness trackers, heart rate monitors, and pulse oximetry finger clips) mainly perform the following functions: real-time collection and display of parameters such as heart rate, blood oxygen saturation, blood pressure, and walking distance; triggering a simple audible and visual alarm when the heart rate exceeds a preset threshold (e.g., (220 - age)) or the blood oxygen saturation falls below a preset value (e.g., 90%). Some high-end devices can record the heart rate and blood oxygen change curves throughout the test and generate a report including walking distance and Borg dyspnea score.

[0005] While existing equipment can record heart rate data after exercise, it does not automatically calculate HRR values, nor does it integrate HRR and ΔSpO2, two independent risk indicators, for analysis. Clinicians must manually calculate HRR and ΔSpO2 and rely on personal experience for comprehensive judgment, which is inefficient and highly subjective. On the other hand, using only single-parameter threshold alarms (e.g., triggering an alarm for excessively high heart rate or low blood oxygen levels separately) cannot solve the decision-making problem when multiple parameters conflict. For example, when a patient walks a long distance (indicating good exercise endurance) but has a severely abnormal HRR (indicating poor autonomic function), the single-parameter threshold method may miss the risk because no individual alarm is triggered, or it may only display the two abnormal values ​​separately without providing a comprehensive risk level, leading to inaccurate assessment. Summary of the Invention

[0006] To overcome the aforementioned shortcomings of the prior art, the purpose of this invention is to provide a method and system for assessing exercise risk based on a six-minute walk test using heart rate recovery and blood oxygenation response, thereby addressing the problems raised in the background art.

[0007] The technical solution adopted by this invention to solve its technical problem is: a method for exercise risk assessment based on a six-minute walk test using heart rate recovery and blood oxygenation response, comprising the following steps: The heart rate, blood oxygen, walking distance, and heart rate at at least one time point after exercise were obtained from the test subjects during rest and exercise. The heart rate at at least one time point after exercise included the peak heart rate during exercise, the heart rate at 1 minute after exercise, and the heart rate at 3 minutes after exercise. Calculate the heart rate recovery value and blood oxygen saturation drop value, and determine the normalized walking distance index, heart rate response index, heart rate recovery index and blood oxygen saturation drop value based on the ratio of measured distance to predicted distance, heart rate response degree, heart rate recovery value and blood oxygen saturation drop value respectively; The exercise risk index is obtained by weighting and summing the four indicators using preset weights. If the heart rate recovery value is less than the first threshold or the blood oxygen drop value is greater than or equal to the second threshold, it is directly judged as high risk. The exercise risk index is compared with the first and second risk thresholds to determine low, medium or high risk, and corresponding instructions are output. The validity of the test was determined based on walking speed stability, pauses during the test, turning standardization, and test duration. Output risk level, effectiveness, and exercise intensity recommendations.

[0008] As a further improvement of the present invention: the acquisition of the test subject's heart rate, blood oxygen, walking distance, and heart rate at at least one time point after exercise, wherein the heart rate at at least one time point after exercise includes the peak heart rate during exercise, the heart rate at 1 minute after exercise, and the heart rate at 3 minutes after exercise, includes: The experimenter collected data on resting heart rate, resting blood oxygen saturation, continuous real-time heart rate, continuous real-time blood oxygen saturation, walking distance, peak heart rate, heart rate at 1 minute after exercise, and heart rate at 3 minutes after exercise during the six-minute walking test.

[0009] As a further improvement of the present invention: the calculation of heart rate recovery value and blood oxygen saturation drop value, and the determination of normalized walking distance index, heart rate response index, heart rate recovery index, and blood oxygen saturation drop index based on the ratio of measured distance to predicted distance, heart rate response degree, heart rate recovery value, and blood oxygen saturation drop value respectively, include: The first heart rate recovery value HRR1 is calculated based on the peak heart rate during exercise and the heart rate at 1 minute after exercise. The second heart rate recovery value HRR3 is calculated based on the peak heart rate during exercise and the heart rate at 3 minutes after exercise. The blood oxygen decrease value ΔSpO2 is calculated based on the resting blood oxygen saturation and the lowest blood oxygen saturation during exercise. The walking distance score S1 is calculated based on the ratio of the measured walking distance to the expected walking distance. The real-time heart rate response score S2 is calculated based on the degree of heart rate response during exercise. The heart rate recovery score S3 is calculated based on the first heart rate recovery value HRR1. The blood oxygen decrease score S4 is calculated based on the blood oxygen decrease value ΔSpO2. The walking distance score S1, the real-time heart rate response score S2, the heart rate recovery score S3, and the blood oxygen decrease score S4 are normalized to the interval [0,1].

[0010] As a further improvement of the present invention: the exercise risk index is obtained by weighting and summing the four indicators using preset weights, and if the heart rate recovery value is less than the first threshold or the blood oxygen saturation value is greater than or equal to the second threshold, it is directly determined to be high-risk, including: S1 = min (1, measured distance / estimated distance), where the estimated distance is calculated using the Enright formula based on gender, age, height, and BMI. S2=max (0, min (1, (peak heart rate) (resting heart rate) / ((220) age) Resting heart rate When HRR1 ≤ 10, S3 = 0; when 10 < HRR1 < 25, S3 = (HRR1) / ( ... 10) / 15; S3=1 when HRR1≥25; S4=max (0, 1 ΔSpO2 / 8); The exercise risk index MRI = α·S1+ β·S2+ γ·S3+ δ·S4 was calculated by weighting the normalized walking distance score S1, real-time heart rate response score S2, heart rate recovery score S3, and blood oxygen decline score S4 with preset first weight α, second weight β, third weight γ, and fourth weight δ, where α+β+γ+δ=1. The default weights are α=0.3, β=0.2, γ=0.3, and δ=0.2. For COPD patients, the weights were adjusted to δ=0.3 and β=0.1; If the first heart rate recovery value HRR1 is less than the first preset threshold or the blood oxygen decrease value ΔSpO2 is greater than or equal to the second preset threshold, it is directly determined as a high-risk condition.

[0011] As a further improvement of the present invention: the step of comparing the sports risk index with the first and second risk thresholds to determine low, medium, or high risk, and outputting corresponding instructions, includes: The motion risk index MRI is compared with a preset first risk threshold and a second risk threshold, wherein the first risk threshold is less than the second risk threshold; If the motion risk index MRI is less than or equal to the first risk threshold, it is considered a low-risk test and a prompt is output indicating that the test can be completed normally. If the first risk threshold < the motion risk index MRI ≤ the second risk threshold, it is judged as a medium risk, and a voice prompt command to decelerate the movement is output. If the motion risk index MRI is greater than the second risk threshold or the mandatory high-risk triggering condition is met, it is determined to be a high-risk event, and an alarm command to immediately terminate the test is output.

[0012] As a further improvement of the present invention: a temporary MRI is calculated every 1 minute. If the temporary MRI exceeds the second risk threshold, the test is terminated early and an alarm is triggered.

[0013] As a further improvement of the present invention: the determination of the test validity based on walking speed stability, mid-journey pauses, turning standardization, and test duration includes: To determine whether this six-minute walk test meets the following conditions simultaneously: The test is considered valid if the walking speed fluctuation does not exceed the preset fluctuation threshold, there are no illegal pauses, no abnormal continuous turns, and the complete test duration is not less than the preset minimum duration; otherwise, it is considered invalid.

[0014] A six-minute walk test exercise risk assessment system based on heart rate recovery and blood oxygenation response includes: Wearable data acquisition module is used to collect the test subject's electrocardiogram signal, heart rate, blood oxygen saturation, triaxial acceleration, angular velocity and walking distance in real time, and record resting heart rate, resting blood oxygen saturation, peak exercise heart rate, heart rate at 1 minute and 3 minutes after exercise. The data processing module is communicatively connected to the wearable acquisition module and is used to execute the feature calculation step, comprehensive evaluation step, risk classification and early warning step, and test effectiveness determination step of the method described in any one of claims 1-6. The early warning module, connected to the data processing module, is used to generate corresponding voice prompt signals or sound and light alarm signals in response to the instructions output by the risk classification and early warning steps. Among them, the high-risk alarm signal has the highest priority and cannot be turned off by the user. The display module is used to display heart rate, blood oxygen saturation, walking distance, exercise risk index MRI, risk level, test effectiveness status, heart rate recovery curve and blood oxygen decline curve in real time.

[0015] As a further improvement of the present invention: the wearable acquisition module includes: ECG electrodes or photoplethysmography sensors are used to acquire heart rate and ECG signals; Reflective or transmissive pulse oximeters are used to collect blood oxygen saturation. A three-axis accelerometer and gyroscope are used to collect motion acceleration and angular velocity to calculate walking distance, cadence, turning angle and pause time; The wearable acquisition module also includes a signal preprocessing unit, which uses a Kalman filter or an adaptive filter to remove motion artifacts from the acquired heart rate and blood oxygen signals.

[0016] As a further improvement of the present invention: the data processing module further includes a weight adjustment unit, which selects the corresponding first to fourth weights from multiple preset weight sets according to the disease type or recovery stage of the test subject; The disease types include heart failure, chronic obstructive pulmonary disease, and pulmonary hypertension; For patients with chronic obstructive pulmonary disease, the fourth weight δ is adjusted to 0.3 and the second weight β is adjusted to 0.1; The rehabilitation phases include the acute phase, the recovery phase, and the maintenance phase, with different risk grading thresholds corresponding to different phases.

[0017] As a further improvement of the present invention: the warning module includes a voice synthesis unit and an interface highlighting and flashing unit; the voice synthesis unit is used to broadcast preset voice commands; the interface highlighting and flashing unit is used to display the high-risk level in red and flashing in the display module; the warning module is also equipped with a mute switch, which is deactivated when the high-risk alarm signal is triggered, and a forced sound and light alarm is output.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention quantifies two independent risk indicators—heart rate recovery and decreased blood oxygenation—by combining walking distance, heart rate response, heart rate recovery, and decreased blood oxygenation into a comprehensive index using a fixed weighted model. This addresses the limitations of existing devices, which can only trigger alarms based on single-parameter thresholds and cannot make decisions when multiple parameters conflict. Furthermore, mandatory high-risk trigger conditions are set to ensure that critical risks are never missed. Based on MRI's three-level risk grading, commands for normal completion, deceleration, and immediate termination are output respectively, enabling precise intervention and avoiding excessive alarms or missed alarms. The validity determination of the trial automatically removes invalid data, ensuring the reliability of the assessment. The system employs four main modules: wearable data acquisition, data processing, early warning, and display. It integrates mechanisms such as Kalman filtering for noise reduction, adaptive weight adjustment, and non-silencing high-risk alarms, making the assessment more aligned with clinical practice and improving the automation level of cardiac rehabilitation exercise risk management. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0020] To enable a clear and complete understanding of the technical solution, the present invention will now be further described in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0024] Embodiments of the present invention provide a method for exercise risk assessment based on a six-minute walk test using heart rate recovery and blood oxygenation response, comprising the following steps: The heart rate, blood oxygen, walking distance, and heart rate at at least one time point after exercise were obtained from the test subjects during rest and exercise. The heart rate at at least one time point after exercise included the peak heart rate during exercise, the heart rate at 1 minute after exercise, and the heart rate at 3 minutes after exercise. Calculate the heart rate recovery value and blood oxygen saturation drop value, and determine the normalized walking distance index, heart rate response index, heart rate recovery index and blood oxygen saturation drop value based on the ratio of measured distance to predicted distance, heart rate response degree, heart rate recovery value and blood oxygen saturation drop value respectively; The exercise risk index is obtained by weighting and summing the four indicators using preset weights. If the heart rate recovery value is less than the first threshold or the blood oxygen drop value is greater than or equal to the second threshold, it is directly judged as high risk. The exercise risk index is compared with the first and second risk thresholds to determine low, medium or high risk, and corresponding instructions are output. The validity of the test was determined based on walking speed stability, pauses during the test, turning standardization, and test duration. Output risk level, effectiveness, and exercise intensity recommendations.

[0025] This invention acquires multi-source data such as resting and post-exercise heart rate, blood oxygen, and walking distance, calculates heart rate recovery and blood oxygen decline values, and constructs four normalized indicators: walking distance, heart rate response, heart rate recovery, and blood oxygen decline. A weighted summation based on preset weights yields an exercise risk index, overcoming the technical shortcomings of existing devices that rely solely on single-parameter threshold alarms and cannot make comprehensive decisions when multiple parameters conflict. This enables a quantitative and comprehensive assessment of exercise risk. Simultaneously, mandatory high-risk trigger conditions are set to ensure no critical risks are missed. By comparing MRI with first and second risk thresholds, low, medium, and high risk levels can be finely classified, with corresponding outputs of normal testing, deceleration prompts, or termination alarm commands, achieving graded early warning and differentiated intervention. Furthermore, the validity of the test is automatically determined based on walking speed stability, pauses, turning standardization, and test duration, avoiding erroneous clinical decisions based on invalid data. Finally, the risk level, validity, and exercise intensity recommendations are output, providing an objective exercise risk assessment tool for cardiac rehabilitation and improving the clinical applicability and safety of the six-minute walk test.

[0026] In one embodiment of the present invention, the acquisition of the test subject's heart rate, blood oxygen, walking distance, and heart rate at at least one time point after exercise, wherein the heart rate at at least one time point after exercise includes the peak heart rate during exercise, the heart rate at 1 minute after exercise, and the heart rate at 3 minutes after exercise, includes: The experimenter collected data on resting heart rate, resting blood oxygen saturation, continuous real-time heart rate, continuous real-time blood oxygen saturation, walking distance, peak heart rate, heart rate at 1 minute after exercise, and heart rate at 3 minutes after exercise during the six-minute walking test.

[0027] Continuous real-time heart rate and blood oxygen acquisition can accurately capture peak heart rate and lowest blood oxygen saturation during exercise, avoiding missed diagnoses or misjudgments due to sparse sampling, thus ensuring the accuracy of blood oxygen drop and heart rate recovery calculations. After exercise, heart rate is acquired at 1 minute and 3 minutes simultaneously. This not only supports the most commonly used first heart rate recovery value (HRR1) for real-time risk assessment, but also provides a second heart rate recovery value (HRR3) as an auxiliary reference indicator for autonomic nerve function recovery, facilitating comprehensive judgment by doctors. The unified acquisition of resting and exercise parameters makes the normalized calculation of indicators such as walking distance score and heart rate response score reliable.

[0028] In one embodiment of the present invention, the calculation of heart rate recovery value and blood oxygen saturation drop value, and the determination of normalized walking distance index, heart rate response index, heart rate recovery index, and blood oxygen saturation drop index based on the ratio of measured distance to predicted distance, heart rate response degree, heart rate recovery value, and blood oxygen saturation drop value, respectively, includes: The first heart rate recovery value HRR1 is calculated based on the peak heart rate during exercise and the heart rate at 1 minute after exercise. The second heart rate recovery value HRR3 is calculated based on the peak heart rate during exercise and the heart rate at 3 minutes after exercise. The blood oxygen decrease value ΔSpO2 is calculated based on the resting blood oxygen saturation and the lowest blood oxygen saturation during exercise. The walking distance score S1 is calculated based on the ratio of the measured walking distance to the expected walking distance. The real-time heart rate response score S2 is calculated based on the degree of heart rate response during exercise. The heart rate recovery score S3 is calculated based on the first heart rate recovery value HRR1. The blood oxygen decrease score S4 is calculated based on the blood oxygen decrease value ΔSpO2. The walking distance score S1, the real-time heart rate response score S2, the heart rate recovery score S3, and the blood oxygen decrease score S4 are normalized to the interval [0,1].

[0029] By calculating the first heart rate recovery value (HRR1) and the second heart rate recovery value (HRR3), the recovery speed of autonomic nerve function within 1 minute and 3 minutes after exercise cessation can be assessed, respectively. HRR1 is a clinically recognized independent predictor of cardiovascular events, while HRR3 provides recovery trend information over a longer time window. By calculating the blood oxygen saturation drop value (ΔSpO2), the degree of exercise-induced hypoxemia can be quantified. Furthermore, the ratio of measured distance to predicted distance, heart rate response, HRR1, and ΔSpO2 are converted into normalized walking distance scores S1, heart rate response scores S2, heart rate recovery scores S3, and blood oxygen saturation drop scores S4, respectively, and all are mapped to the [0,1] interval. This makes the four parameters, which originally had different dimensions and clinical significance, comparable and avoids the one-sidedness of single-parameter threshold alarms.

[0030] In the calculation of the walking distance score S1, the expected walking distance is calculated using the Enright formula: For male participants, the expected distance = 867 - 5.71 × age - 1.03 × BMI + 0.14 × height (cm); For female participants, the expected distance = 525 - 2.86 × age - 0.77 × BMI + 0.14 × height (cm); By using the Enright formula to calculate the expected walking distance and by using four physiological parameters—gender, age, BMI, and height—individualized correction of theoretical exercise capacity can be achieved. This allows the walking distance score S1 to objectively reflect the exercise endurance level of the test subject relative to their own healthy baseline, avoiding the assessment bias caused by using a uniform fixed distance standard for different body types and age groups.

[0031] The value of S1 is the smaller of the ratio of the measured distance to the expected distance and 1, i.e., S1 = min(1, measured distance / expected distance); S1 is taken as the smaller value between the ratio of measured distance to expected distance and 1, to prevent excessive scores due to exceptional performance from masking adverse changes in other risk indicators, and to ensure the relative balance of the contributions of each indicator during weighted fusion.

[0032] The real-time heart rate response score S2 is calculated using the Karvonen formula: S2 = max(0, min(1, (peak heart rate - resting heart rate) / ((220 - age) - resting heart rate))).

[0033] The Karvonen formula is used to calculate the real-time heart rate response score S2. By predicting the maximum heart rate through the resting heart rate and age, it can accurately quantify the utilization rate of the heart rate reserve during exercise, reflect the chronotropic function of the heart. The Karvonen formula excludes the interference of individual resting heart rate differences, making S2 more truly reflect the adaptive response of the heart rate to exercise load. Through the boundary truncation processing of max(0, min(1,...)), S2 is forced to be limited within the interval [0, 1] to ensure that abnormal extreme values do not cause the score to exceed the boundary.

[0034] The piecewise normalization method of the heart rate recovery score S3 is as follows: When HRR1 ≤ 10, S3 = 0; When 10 < HRR1 < 25, S3 = (HRR1 - 10) / 15; When HRR1 ≥ 25, S3 = 1; HRR1 ≤ 10 beats per minute is generally considered a state of severe autonomic insufficiency and extremely high risk of cardiovascular events. Therefore, the score is directly assigned as 0, making the maximum negative contribution in weighted fusion; HRR1 ≥ 25 beats per minute represents good heart rate recovery and normal autonomic regulation function, with the score assigned as 1, having no negative impact on the risk index; for HRR1 between 10 and 25, linear interpolation is used, and the score continuously increases with the increase of HRR1, avoiding information loss caused by binary classification and being able to distinguish moderate heart rate recovery abnormalities.

[0035] The normalization method of the blood oxygen decline score S4 is as follows: S4 = max(0, 1 - ΔSpO2 / 8); The blood oxygen decline score S4 uses a linear attenuation function to map the blood oxygen decline value ΔSpO2 to the interval [0, 1], reflecting the risk gradient of clinical hypoxemia: when ΔSpO2 = 0%, S4 = 1, indicating no risk; as ΔSpO2 increases, S4 linearly decreases; when ΔSpO2 ≥ 8%, S4 = 0, indicating that the blood oxygen decline has reached a severe level and the risk contribution is the largest negative.

[0036] The first preset threshold is 18 beats per minute, and the second preset threshold is 4%. Both thresholds come from the recognized risk cut-off values in the clinical cardiac rehabilitation guidelines: HRR1 < 18 bpm indicates severe impairment of autonomic function, which is related to adverse cardiovascular events; ΔSpO2 ≥ 4% is widely recognized as the positive standard for exercise-induced hypoxemia.

[0037] In an embodiment of the present invention, the four indicators are weighted and summed using preset weights to obtain a motion risk index. At the same time, if the heart rate recovery value is less than the first threshold or the blood oxygen decline value is greater than or equal to the second threshold, it is directly determined as high risk, including: S1 = min (1, measured distance / estimated distance), where the estimated distance is calculated using the Enright formula based on gender, age, height, and BMI. S2=max (0, min (1, (peak heart rate) (resting heart rate) / ((220) age) Resting heart rate When HRR1 ≤ 10, S3 = 0; when 10 < HRR1 < 25, S3 = (HRR1) / ( ... 10) / 15; S3=1 when HRR1≥25; S4=max (0, 1 ΔSpO2 / 8); The exercise risk index MRI = α·S1+ β·S2+ γ·S3+ δ·S4 was calculated by weighting the normalized walking distance score S1, real-time heart rate response score S2, heart rate recovery score S3, and blood oxygen decline score S4 with preset first weight α, second weight β, third weight γ, and fourth weight δ, where α+β+γ+δ=1. The default weights are α=0.3, β=0.2, γ=0.3, and δ=0.2. For COPD patients, the weights were adjusted to δ=0.3 and β=0.1; An exercise risk index MRI is constructed by weighting and summing the normalized walking distance score (S1), real-time heart rate response score (S2), heart rate recovery score (S3), and blood oxygen saturation decline score (S4) using preset weights. The weights for walking distance and heart rate recovery reflect their core role in exercise risk assessment; the weights for heart rate response and blood oxygen saturation decline serve as auxiliary correction indicators to address the decision-making dilemma when different indicators point to contradictory conclusions. Through weighted summation, a continuous risk quantification value is obtained, enabling more refined risk classification.

[0038] If the first heart rate recovery value HRR1 is less than the first preset threshold or the blood oxygen decrease value ΔSpO2 is greater than or equal to the second preset threshold, it is directly determined as a high-risk condition.

[0039] If HRR1 < 18 bpm or ΔSpO2 ≥ 4%, it is directly classified as high risk. This condition, along with weighted summation, forms a dual safeguard mechanism: weighted summation is used to comprehensively assess the risk level under multi-parameter coordination, while the mandatory condition is used to prevent any single key indicator from reaching the clinically recognized risk cutoff value. Even if the weighted summation MRI does not exceed the high-risk threshold, the system will still immediately output a high-risk judgment as long as the mandatory condition is triggered. This retains the advantages of multi-dimensional information fusion while avoiding the risk of missing serious single abnormalities due to averaging effects, thus improving the sensitivity and safety of motion risk warning.

[0040] In one embodiment of the present invention, the step of comparing the sports risk index with first and second risk thresholds to determine low, medium, or high risk, and outputting corresponding instructions, includes: The motion risk index MRI is compared with a preset first risk threshold and a second risk threshold, wherein the first risk threshold is less than the second risk threshold; If the motion risk index MRI is less than or equal to the first risk threshold, it is considered a low-risk test and a prompt is output indicating that the test can be completed normally. If the first risk threshold < the motion risk index MRI ≤ the second risk threshold, it is judged as a medium risk, and a voice prompt command to decelerate the movement is output. If the motion risk index MRI is greater than the second risk threshold or the mandatory high-risk triggering condition is met, it is determined to be a high-risk event, and an alarm command to immediately terminate the test is output.

[0041] A clinically adapted fixed-weighted model was constructed by explicitly setting the first weight α=0.3, the second weight β=0.2, the third weight γ=0.3, and the fourth weight δ=0.2. Walking distance and heart rate recovery each accounted for 0.3, reflecting their core position in exercise risk assessment; heart rate response and blood oxygen saturation decreased each accounted for 0.2 as auxiliary correction terms. The weight allocation was based on the empirical quantification of the importance of indicators in cardiac rehabilitation clinical guidelines, ensuring the clinical relevance of the exercise risk index MRI.

[0042] The first risk threshold is 0.4, and the second risk threshold is 0.7; Continuous MRI values ​​are divided into three levels: low risk (≤0.4), intermediate risk (0.4~0.7), and high risk (>0.7). Correspondingly, three differentiated instructions are output: normal completion, deceleration prompt, and termination alarm. This avoids the confusion caused by overly fine classification and ensures sufficient differentiation.

[0043] The preset fluctuation threshold is 20%, and the preset minimum duration is 5.5 minutes. As a criterion for validity determination, the strictness of the test standards and the practical operability are taken into account to ensure that only tests with qualified data quality are included in the evaluation.

[0044] The violation of a pause during the test is determined by an accelerometer reading of zero step frequency for more than 5 seconds, and the abnormal continuous turning is determined by a gyroscope reading of more than 3 times a change of direction greater than 90° within 10 seconds. By using an accelerometer to determine a pause of zero step frequency for more than 5 seconds and a gyroscope to determine more than 3 changes of direction greater than 90° within 10 seconds, the validity of the test is objectively determined, eliminating the need for manual visual inspection, removing subjective errors, and ensuring the reliability of the six-minute walking test data.

[0045] In one embodiment, the method further includes a step of calculating an intermediate risk index at preset time intervals during a six-minute walk test. For every minute of walking completed, a temporary MRI is calculated based on the currently collected peak heart rate, current lowest blood oxygen saturation, current walking distance, and corresponding normalized score. If the temporary MRI is greater than the second risk threshold, the trial is terminated early and a high-risk alarm is output.

[0046] By calculating an intermediate risk index every minute during a six-minute walk test, the system enables real-time dynamic monitoring and early warning of exercise risks. After each minute of walking, the system calculates a temporary MRI based on the currently collected peak heart rate, current lowest blood oxygen saturation, current walking distance, and corresponding normalized score, and compares it with a second risk threshold. If the temporary MRI exceeds 0.7, the test is terminated immediately without waiting for the six-minute test to end, and a high-risk alarm is issued.

[0047] In one embodiment of the present invention, determining the validity of the test based on walking speed stability, pauses during the test, turning standardization, and test duration includes: To determine whether this six-minute walk test meets the following conditions simultaneously: The test is considered valid if the walking speed fluctuation does not exceed the preset fluctuation threshold, there are no illegal pauses, no abnormal continuous turns, and the complete test duration is not less than the preset minimum duration; otherwise, it is considered invalid.

[0048] The test requires that walking speed fluctuations not exceed a preset fluctuation threshold to exclude unsteady walking caused by unstable rhythm or frequent starts and stops; there must be no improper pauses during the test, with a step frequency of zero for more than 5 seconds as measured by accelerometer to ensure continuous testing; there must be no abnormal continuous turns, with more than 3 directional changes greater than 90° within 10 seconds as measured by gyroscope to exclude invalid distance accumulation or abnormal fluctuations in physiological parameters caused by improper turning movements; and the complete test duration must not be less than a preset minimum duration to avoid insufficient data due to premature termination. This rigorous validity assessment ensures that only high-quality test data conforming to standard operating procedures can enter the risk assessment and rehabilitation recommendation generation stages, thereby avoiding erroneous clinical decisions based on invalid data.

[0049] A six-minute walk test exercise risk assessment system based on heart rate recovery and blood oxygenation response includes: Wearable data acquisition module is used to collect the test subject's electrocardiogram signal, heart rate, blood oxygen saturation, triaxial acceleration, angular velocity and walking distance in real time, and record resting heart rate, resting blood oxygen saturation, peak exercise heart rate, heart rate at 1 minute and 3 minutes after exercise. The data processing module is communicatively connected to the wearable acquisition module and is used to execute the feature calculation step, comprehensive evaluation step, risk classification and early warning step, and test effectiveness determination step of the method described in any one of claims 1-6. The early warning module, connected to the data processing module, is used to generate corresponding voice prompt signals or sound and light alarm signals in response to the instructions output by the risk classification and early warning steps. Among them, the high-risk alarm signal has the highest priority and cannot be turned off by the user. The display module is used to display heart rate, blood oxygen saturation, walking distance, exercise risk index MRI, risk level, test effectiveness status, heart rate recovery curve and blood oxygen decline curve in real time.

[0050] In one embodiment of the present invention, the wearable data collection module includes: ECG electrodes or photoplethysmography sensors are used to acquire heart rate and ECG signals; Reflective or transmissive pulse oximeters are used to collect blood oxygen saturation. A three-axis accelerometer and gyroscope are used to collect motion acceleration and angular velocity to calculate walking distance, cadence, turning angle and pause time; The wearable acquisition module also includes a signal preprocessing unit, which uses a Kalman filter or an adaptive filter to remove motion artifacts from the acquired heart rate and blood oxygen signals.

[0051] In one embodiment of the present invention, the data processing module further includes a weight adjustment unit, which selects the corresponding first to fourth weights from a set of multiple preset weights according to the disease type or recovery stage of the test subject. The disease types include heart failure, chronic obstructive pulmonary disease, and pulmonary hypertension; For patients with chronic obstructive pulmonary disease, the fourth weight δ is adjusted to 0.3 and the second weight β is adjusted to 0.1; The rehabilitation phases include the acute phase, the recovery phase, and the maintenance phase, with different risk grading thresholds corresponding to different phases.

[0052] In one embodiment of the present invention, the warning module includes a voice synthesis unit and an interface highlighting and flashing unit; the voice synthesis unit is used to broadcast preset voice commands; the interface highlighting and flashing unit is used to display the high-risk level in red and flashing in the display module; the warning module is also provided with a mute switch, which is deactivated when the high-risk alarm signal is triggered, and a forced sound and light alarm is output.

[0053] In summary, after reading this invention document, those skilled in the art can make various other corresponding modifications to the technical solutions and concepts based on this invention without creative mental effort, and all of these modifications fall within the scope of protection of this invention.

Claims

1. A method for assessing exercise risk based on a six-minute walk test using heart rate recovery and blood oxygenation response, characterized in that, Includes the following steps: The experimenter obtained heart rate, blood oxygen, walking distance, peak heart rate, heart rate at 1 minute and 3 minutes after exercise during rest and exercise. The first heart rate recovery value HRR1 is calculated based on the peak heart rate during exercise and the heart rate at 1 minute after exercise. The second heart rate recovery value HRR3 is calculated based on the peak heart rate during exercise and the heart rate at 3 minutes after exercise. The blood oxygen saturation drop value ΔSpO2 is calculated based on the resting blood oxygen saturation and the lowest blood oxygen saturation during exercise. The walking distance score S1 is calculated based on the ratio of the measured walking distance to the expected walking distance. The real-time heart rate response score S2 is calculated based on the degree of heart rate response during exercise. The heart rate recovery score S3 is calculated based on the first heart rate recovery value HRR1. The blood oxygen drop score S4 is calculated based on the blood oxygen drop value ΔSpO2. The walking distance score S1, the real-time heart rate response score S2, the heart rate recovery score S3, and the blood oxygen drop score S4 are normalized to the [0,1] interval, respectively. The exercise risk index is obtained by weighting and summing the four indicators using preset weights. If the heart rate recovery value is less than the first threshold or the blood oxygen drop value is greater than or equal to the second threshold, it is directly judged as high risk. The exercise risk index is compared with the first and second risk thresholds to determine low, medium or high risk, and corresponding instructions are output. The validity of the test was determined based on walking speed stability, pauses during the test, turning standardization, and test duration. Output risk level, effectiveness, and exercise intensity recommendations.

2. The exercise risk assessment method based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 1, characterized in that, The acquisition of the test subject's heart rate, blood oxygen, walking distance, peak heart rate during exercise, and heart rate at 1 minute and 3 minutes after exercise includes: The experimenter collected data on resting heart rate, resting blood oxygen saturation, continuous real-time heart rate, continuous real-time blood oxygen saturation, walking distance, peak heart rate, heart rate at 1 minute after exercise, and heart rate at 3 minutes after exercise during the six-minute walking test.

3. The exercise risk assessment method based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 2, characterized in that, The exercise risk index is obtained by weighting and summing the four indicators using preset weights. If the heart rate recovery value is less than a first threshold or the blood oxygen saturation value is greater than or equal to a second threshold, it is directly determined to be high-risk, including: S1 = min (1, measured distance / estimated distance), where the estimated distance is calculated using the Enright formula based on gender, age, height, and BMI. S2=max (0, min (1, (peak heart rate) (resting heart rate) / ((220) age) Resting heart rate When HRR1 ≤ 10, S3 = 0; when 10 < HRR1 < 25, S3 = (HRR1) / ( ... 10) / 15; S3=1 when HRR1≥25; S4=max (0, 1 ΔSpO2 / 8); The exercise risk index MRI = α·S1 + β·S2 + γ·S3 + δ·S4 was calculated by weighting the normalized walking distance score S1, real-time heart rate response score S2, heart rate recovery score S3, and blood oxygen decline score S4 with preset first weight α, second weight β, third weight γ, and fourth weight δ, where α+β+γ+δ=1. The default weights are α=0.3, β=0.2, γ=0.3, and δ=0.

2. For COPD patients, the weights were adjusted to δ=0.3 and β=0.1; If the first heart rate recovery value HRR1 is less than the first preset threshold or the blood oxygen decrease value ΔSpO2 is greater than or equal to the second preset threshold, it is directly determined as a high-risk condition.

4. The exercise risk assessment method based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 3, characterized in that, The step of comparing the sports risk index with the first and second risk thresholds to determine low, medium, or high risk, and outputting corresponding instructions, includes: The motion risk index MRI is compared with a preset first risk threshold and a second risk threshold, wherein the first risk threshold is less than the second risk threshold; If the motion risk index MRI is less than or equal to the first risk threshold, it is considered a low-risk test and a prompt is output indicating that the test can be completed normally. If the first risk threshold < the motion risk index MRI ≤ the second risk threshold, it is judged as a medium risk, and a voice prompt command to decelerate the movement is output. If the motion risk index MRI is greater than the second risk threshold or the mandatory high-risk triggering condition is met, it is determined to be a high-risk event, and an alarm command to immediately terminate the test is output.

5. The exercise risk assessment method based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 4, characterized in that, A temporary MRI is calculated every minute. If the temporary MRI exceeds the second risk threshold, the trial is terminated early and an alarm is triggered.

6. The exercise risk assessment method based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 5, characterized in that, The determination of test validity based on walking speed stability, pauses, turning technique, and test duration includes: To determine whether this six-minute walk test meets the following conditions simultaneously: The test is considered valid if the walking speed fluctuation does not exceed the preset fluctuation threshold, there are no illegal pauses, no abnormal continuous turns, and the complete test duration is not less than the preset minimum duration; otherwise, it is considered invalid.

7. A six-minute walk test exercise risk assessment system based on heart rate recovery and blood oxygenation response, characterized in that, include: Wearable data acquisition module is used to collect the test subject's electrocardiogram signal, heart rate, blood oxygen saturation, triaxial acceleration, angular velocity and walking distance in real time, and record resting heart rate, resting blood oxygen saturation, peak exercise heart rate, heart rate at 1 minute and 3 minutes after exercise. The data processing module is communicatively connected to the wearable acquisition module and is used to execute the feature calculation step, comprehensive evaluation step, risk classification and early warning step, and test effectiveness determination step of the method described in any one of claims 1-6. The early warning module, connected to the data processing module, is used to generate corresponding voice prompt signals or sound and light alarm signals in response to the instructions output by the risk classification and early warning steps. Among them, the high-risk alarm signal has the highest priority and cannot be turned off by the user. The display module is used to display heart rate, blood oxygen saturation, walking distance, exercise risk index MRI, risk level, test effectiveness status, heart rate recovery curve and blood oxygen decline curve in real time.

8. The exercise risk assessment system based on the six-minute walk test using heart rate recovery and blood oxygenation response as described in claim 7, characterized in that, The wearable data acquisition module includes: ECG electrodes or photoplethysmography sensors are used to acquire heart rate and ECG signals; Reflective or transmissive pulse oximeters are used to collect blood oxygen saturation. A three-axis accelerometer and gyroscope are used to collect motion acceleration and angular velocity to calculate walking distance, cadence, turning angle and pause time; The wearable acquisition module also includes a signal preprocessing unit, which uses a Kalman filter or an adaptive filter to remove motion artifacts from the acquired heart rate and blood oxygen signals.

9. The exercise risk assessment system based on heart rate recovery and blood oxygenation response of a six-minute walk test according to claim 7, wherein the data processing module further includes a weight adjustment unit, wherein the weight adjustment unit selects the corresponding first to fourth weights from multiple preset weight sets according to the test subject's disease type or rehabilitation stage; The disease types include heart failure, chronic obstructive pulmonary disease, and pulmonary hypertension; For patients with chronic obstructive pulmonary disease, the fourth weight δ is adjusted to 0.3 and the second weight β is adjusted to 0.1; The rehabilitation phases include the acute phase, the recovery phase, and the maintenance phase, with different risk grading thresholds corresponding to different phases.

10. A six-minute walk test exercise risk assessment system based on heart rate recovery and blood oxygenation response as described in claim 7, wherein the early warning module includes a voice synthesis unit and an interface highlighting and flashing unit; the voice synthesis unit is used to broadcast preset voice commands; the interface highlighting and flashing unit is used to display the high-risk level in red and flashing in the display module; the early warning module is also provided with a mute switch, which is deactivated when a high-risk alarm signal is triggered, and a forced sound and light alarm is output.

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