Patent ID: 9597011
Date: 2017-03-21
CPC Classifications: A61B

Claim:
1. A respiratory phase determination apparatus, which compensates for differences in respiration among subjects or variations in respiration of a subject without calibration, the respiratory phase determination apparatus comprising a first sensor that is attached at a first position of a body of a subject to acquire a first biological sound signal including a first breath sound signal, the first breath sound signal has a usual power of an inspiratory phase greater than a usual power of an expiratory phase; a second sensor that is attached at a second position of the body of the subject to acquire a second biological sound signal including a second breath sound signal, the second breath sound signal has a usual power of an inspiratory phase smaller than a usual power of an expiratory phase; and circuitry operative to: receive the first breath sound signal from the first sensor and the second breath sound signal from the second sensor during a first predetermined time; calculate a first power of the first breath sound signal for each of a plurality of time frames and a second power of the second breath sound signal for each of the time frames, the first predetermined time being divided into the plurality of time frames; extract pauses, each of the pauses including consecutive time frames in which either one of the first power is less than a first threshold value and the second power is less than a second threshold value; extract respiratory periods, each of the respiratory periods between one pause of the extracted pauses and next one pause of the extracted pauses, the one pause and the next one pause are temporally located next to each other in the extracted pauses and being longer than a second predetermined time; determine a first average power of the first breath sound signal, by using the first power, in each of the respiratory periods and a second average power of the second breath sound signal, by using the second power, in each of the respiratory periods; obtain a combined average power by subtracting the first average power from the second feature value for each of the respiratory periods, the combined average power cancelling fluctuations due to irregularity in the first breath sound signal and the second breath sound signal; compare two of the combined average powers obtained for a pair of respiratory periods to determine which one of the two combined average powers is larger, the pair of respiratory periods including two consecutive respiratory periods; determine whether a previous period included in the pair of respiratory periods and a following period in the pair of respiratory periods correspond to an inspiratory phase or expiratory phase based on a result of the comparison and a predetermined datum; and output a result of the determination, to perform a lung sound analysis for an asthma test on the first or second biological sound signal at least in the determined inspiratory phase, wherein the first position is set to acquire a vesicular breath in a first predetermined range of the body of the subject, the second position is set to acquire a tracheal breath sound or bronchial breath sound in a second predetermined range of the body of the subject, the predetermined datum indicates that one respiratory period in the pair of respiratory periods which has larger combined average power corresponds to the expiratory phase and the other respiratory period in the pair of respiratory periods corresponds to the inspiratory phase.