Method for measuring physiological parameters

A method for measuring physiological parameters uses statistical properties, spectrum analysis and feedback mechanisms to remove the signal noise generated by human body movement from a detected physiological signal.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to a method for measuring physiological parameters.

2. Description of the Related Art

As people pay more and more attention to health, increasing numbers of physiological tests are conducted in non-hospital settings. If the subject base is expanded from hospital patients to include all people, that is, if technologies for detecting physiological parameters are applied to daily life activities of subjects, many conditions may be avoided. For example, if heartbeat or breathing of a subject is monitored during sleep, an apnea syndrome may be prevented. If the heartbeat or breathing of the subject can be monitored while driving, car accidents due to drowsiness can be prevented.

Based on the above situation, various detection technologies for measuring physiological parameters are available in the industry. Such technologies include exploiting spectral conversion to calculate heartbeat rate, applying a chest strap-type heart rate monitor to monitor the subject's electrocardiogram during exercise, applying different filters to an electrocardiogram detection result to remove noise caused by circuit and electromyographic signals, employing Doppler radar during heartbeat and breathing monitoring, estimating the heartbeat rate through spectral conversion in a recursive fashion, and using a pressure gauge and spectral conversion to normalize heartbeat rate during exercising.

Accurate measurement of heartbeat and breathing rate are usually only possible when the subject is not in motion. If, during the measurement process, the subject is in motion, a floating signal occurs in the electrocardiogram detector due to the interference of the electromyographic signal. Radar sensors also are affected by interference caused by relative movement of the subject. However, the prior art has not provided any method for removing the signal interference caused by the subject's movement.

Based on the above, in order to solve the problem currently faced by the medical industry, namely, the imprecise measurement of physiological parameters due to human body motion or movement interference, it is necessary to design a method for measuring physiological parameters. The to method is capable of removing noise generated from movement interference through statistical properties, spectrum analysis and feedback mechanisms. The present disclosure provides the method for measuring physiological parameters.

SUMMARY OF THE DISCLOSURE

The present disclosure presents a method for measuring physiological parameters, which includes the steps of: continuously receiving a physiological signal, where the physiological signal includes at least one physiological parameter of a subject; calculating a statistical parameter of the physiological signal; determining whether the physiological signal includes movement interference noise according to the statistical parameter; if it is determined that the received signal includes the movement interference noise, reduce the movement interference noise; decide a maximum value of the physiological signal on a frequency spectrum through a Fast Fourier Transform; and decide at least one physiological parameter of the subject accordingly.

Technical features of the present disclosure are briefly described, and may be better understood through detailed descriptions below. Other technical features forming the subject matter of the present disclosure are also described. Persons with ordinary skill in the art of the present disclosure shall understand that modifications or designs of other structures or manufacturing procedures based on the concepts and specific exemplary embodiments disclosed below can be applied to meet the objectives of the present disclosure. Persons with ordinary skill in the art of the present disclosure shall also understand that such equivalent constructions do not depart from the spirit and scope of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure is directed to a method for measuring physiological parameters. For thorough understanding of the disclosure, detailed steps are provided in the following description. The implementation of the disclosure is not limited to special details familiar to those skilled in the art of the disclosure. In addition, steps known to all are not described in detail, so as to avoid unnecessary limitation to the disclosure. The preferred exemplary embodiments of the disclosure are described below. However, in addition to the detailed description, the disclosure may further be implemented in other exemplary embodiments. The scope of the disclosure is not limited, and is subject to the scope of the claims below.

FIG. 1is a flow chart of a method for measuring physiological parameters according to an exemplary embodiment of the disclosure. In Step101, an initial physiological signal is received, where the physiological signal includes at least one physiological parameter of a subject, and Step102is executed. In Step102, an operation of a bandpass filter is performed on the initial physiological signal, and Step103is executed. In Step103, statistical properties of the initial physiological signal are calculated, and Step104is executed. In some exemplary embodiments of the disclosure, the calculated statistical properties include an average value and a standard deviation of the initial physiological signal. In Step104, an initial physiological signal is continuously received, where the physiological signal includes at least one physiological parameter of the subject, and Step105is executed. In some exemplary embodiments of the disclosure, the initial physiological signal and the detected physiological signal are received and stored in a queue. In some exemplary embodiments of the disclosure, the at least one physiological parameter includes a breath parameter, a heartbeat parameter or an enterocinesia parameter of the subject. In Step105, an operation of the bandpass filter is performed on the detected physiological signal, and Step106is executed.

In Step106, it is determined whether the detected physiological signal includes movement interference noise according to the calculated statistical properties. If it is determined that the detected physiological signal includes the movement interference noise, then Step107is executed; otherwise, if it is determined that the detected physiological signal does not include the movement interference noise, then Step109is executed. In some exemplary embodiments of the present disclosure, it is determined in Step106whether a difference between each sampling point of the detected physiological signal and an average value of the physiological signal is greater than an integral multiple of a standard deviation of the physiological signal. The integral multiple, for example, can be 1 to 5. In Step106, it is determined whether the received signal includes the movement interference noise. In Step107, a component of the movement interference noise is reduced, and Step108is executed. In some exemplary embodiments of the present disclosure, in Step107, the step of reducing the movement interference noise is performed to reduce an influence of the movement interference noise on the frequency spectrum. In some exemplary embodiments of the present disclosure, the step of reducing the movement interference noise is performed to perform a calculation on the physiological signal using a Chebyshev Inequality. However, the step of reducing the movement interference noise of the present disclosure is not limited to using the Chebyshev Inequality, but may include any operation method capable of reducing the movement interference noise, for example, a bandpass filter, a Median Filter or a Gaussian Filter. Among such operation methods, the Chebyshev Inequality is a relatively reliable and effective operation method. In Step108, an operation of the bandpass filter is performed on the detected physiological signal with the reduced movement interference noise, and Step109is executed.

In Step109, it is determined whether the detected physiological signal is close to a saturation value. If it is determined that the detected physiological signal is close to the saturation value, then Step110is executed. If it is determined that the detected physiological signal is not close to the saturation value, then Step111is executed. In Step110, at least one physiological parameter of the detected physiological signal is decided according to the at least one physiological parameter decided previously. In Step111, a power spectral density of the detected physiological signal is calculated using the Fast Fourier Transform, and Step112is executed. In some exemplary embodiments of the present disclosure, in Step111, the step of calculation using the Fast Fourier Transform is performed according to a specific timeframe after deducting the average value from the detected physiological signal. In some exemplary embodiments of the present disclosure, the specific timeframe is from 1 to 60 seconds. In Step112, a maximum value of the detected physiological signal on the frequency spectrum is determined, and Step113is executed. In Step113, it is determined whether the maximum value can be used as a dominant frequency of the detected physiological signal. If it is determined that the maximum value can be used as the dominant frequency of the detected physiological signal, then Step114is executed. If it is determined that the maximum value cannot be used as the dominant frequency of the detected physiological signal, then Step115is executed. In some exemplary embodiments of the present disclosure, in Step113, a second maximum value is searched in a bandwidth range, wherein the bandwidth range includes the maximum value as a center, and it is determined whether energy of the maximum value is greater than an integral multiple of energy of the second maximum value. If the energy of the maximum value is greater than the integral multiple of the energy of the second maximum value, it is determined that the maximum value can be used as the dominant frequency of the detected physiological signal. In some exemplary embodiments of the present disclosure, the bandwidth range in Step113is between 0 and 4 hertz (Hz). In some exemplary embodiments of the present disclosure, the integral multiple in Step113is between 1 and 20.

In Step114, the maximum value is set as the dominant frequency of the physiological signal, at least one physiological parameter of the subject is decided according to the maximum value, and Step116is executed. In Step115, at least one physiological parameter of the subject is decided in a bandwidth range, wherein the bandwidth range includes the previous dominant frequency of the physiological signal as a center, and Step117is executed. In some exemplary embodiments of the present disclosure, the bandwidth range of Step115is between 0 and 4 Hz. In Step116, the statistical properties of the physiological signal are calculated according to the dominant frequency of the physiological signal, and Step117is executed. In Step117, it is determined whether to end the method. If it is determined to end the method, the method is ended. If it is determined not to end the method, the process returns to Step104.

In the following example, the method ofFIG. 1is applied to detecting a physiological parameter.FIG. 2is a time domain chart of a detected physiological signal according to an exemplary embodiment of the present disclosure, where the detected physiological signal includes a heartbeat signal and a movement interference signal. In the exemplary embodiment, the physiological signal may be provided by an electrocardiogram or an ultra wideband signal detector. The detected physiological signal is a time domain chart after the operation of the bandpass filter in Step105. As shown inFIG. 2, a large amplitude is generated in a middle section of the detected physiological signal due to movement interference.FIG. 3is the frequency domain chart of the detected physiological signal inFIG. 2. As shown inFIG. 3, the heartbeat signal is a heart rate wave of 1.5 Hz and the movement interference signal is 0.9 Hz. Therefore, a high frequency response exists at both 1.5 Hz and 0.9 Hz in the frequency domain chart of the detected physiological signal.

In Step106, if it is determined that the detected physiological signal includes the movement interference noise, then Step107is executed. In Step107, calculation is performed on the detected physiological signal using the Chebyshev Inequality in order to reduce the component of the movement interference noise.FIG. 4is a time domain chart of the detected physiological signal after the calculation of the Chebyshev Inequality. As shown inFIG. 4, the operation of the Chebyshev Inequality is to compress a part of the detected physiological signal influenced by the movement interference signal, namely, the signal at the middle section of the chart. A part with higher amplitude is compressed at a higher degree. As for the frequency domain, the calculation of the Chebyshev Inequality is equivalent to moving a component at 0.9 Hz of the physiological signal to a high-frequency position.

In Step108, the operation of the bandpass filter is performed on the detected physiological signal. In this step, the movement interference noise of the detected physiological signal is reduced.FIG. 5is a time domain chart of the detected physiological signal using the operation of the bandpass filter after the calculation of the Chebyshev Inequality. As shown inFIG. 5, a high-frequency component generated by the calculation of Chebyshev Inequality, namely a sharp-pointed section of the detected physiological signal inFIG. 4, is eliminated from the detected physiological signal.FIG. 6is a frequency domain chart of the detected physiological signal through the operation of the bandpass filter after the calculation of the Chebyshev Inequality. As shown inFIG. 6, the movement interference signal is moved to the high-frequency position, and is eliminated through the operation of the bandpass filter. Therefore, the detected physiological signal only includes the detected heartbeat signal.

In Step109, if the detected physiological signal is close to the saturation value, that is, if some of the sampling points of the detected physiological signal reach the saturation value, then the detected physiological signal is not reliable, and Step110is executed. In Step110, the previously decided heartbeat parameter is directly output.

In Step113, if the noise of the detected physiological signal is removed, then only one dominant maximum value remains in a bandwidth range, and it is determined that the maximum value can be used as the dominant frequency of the detected physiological signal. On the other hand, if some noise still exists in the detected physiological signal, then other noise components remain in the bandwidth range, and it is determined that the maximum value cannot be used as the dominant frequency of the detected physiological signal.

In Step116, if it is determined that the maximum value can be used as the dominant frequency of the detected physiological signal, the statistical parameter of the physiological signal is updated accordingly. This is a feedback mechanism provided by the method for measuring physiological parameters according to the present disclosure. According to the feedback mechanism, the method for measuring physiological parameters of the present disclosure is capable of continuously tracing the physiological parameters of the subject.

In conclusion, the method for measuring physiological parameters according to the present disclosure uses statistical, properties, spectrum analysis and feedback mechanisms to perform signal processing on the detected physiological signal. As shown in the above description, the method for measuring physiological parameters of the present disclosure is capable of removing noise generated from the movement interference.

Technical content and technical features of the present disclosure are disclosed. However, persons skilled in the art may make other replacements and modifications without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure shall not be limited to the exemplary embodiments disclosed. Rather, the scope of the present disclosure should include all replacements and modifications without departing from the present disclosure and shall be covered by the scope of claims below.