Apparatus for determining respiratory condition

An apparatus for determining an inspiratory flow limitation, the apparatus comprising:

• a signal acquirer which is configured to acquire a signal waveform corresponding to a respiratory flow of a subject;
• and
• a controller configured to function as (i) a first determiner to identify start and end phases of inspiration of the subject based on a gradient of the signal waveform and to determine that inspiratory flow limitation occurs in the subject, (ii) an acquirer to acquire a gradient value of the signal waveform between a time t1 when an amplitude of the signal waveform changes from a positive value to a negative value and a time t4 when the amplitude of the signal waveform changes from a negative value to a positive value and (iii) a differential calculator to acquire a secondary differential waveform by performing secondary differentiation of the signal waveform,
• wherein the first determiner determines that inspiratory flow limitation occurs when the secondary differential waveform satisfies a predetermined condition in a portion of the signal waveform,
• wherein the portion of the signal waveform is a time period excluding the start and end phases of the inspiration of the subject, wherein
• the start phase is an amount of time between the time t1 and a time t2 when the gradient value of the signal waveform is less than a maximum gradient value and
• the end phase is an amount of time between the time t4 and a time t3 when the gradient value of the signal waveform is less than the maximum gradient value,
• wherein the predetermined condition, is satisfied when an amount of a time interval, characterized by the secondary differential waveform having a negative value, is equal to or larger than a predetermined value.