Patent ID: 8419645

Claim:
A heart monitor configured to obtain respiration metrics comprising: an impedance signal input; an impedance measurement unit coupled with said impedance signal input; a microprocessor configured to obtain a first time series of values that represent a transthoracic impedance signal obtained from said impedance measurement unit; and, said microprocessor further configured to generate a modified time series of values that represent a trend of values of said first time series through application of at least one morphological operator comprising an erosion operator or a dilation operator or any combination thereof wherein said trend of values comprises a respiratory component of said first times series, and wherein said at least one morphological operator includes said erosion operator defined by F ⁢ ⁢ Θ ⁢ ⁢ K ⁡ ( i ) = min j = 0 , ⁢ … ⁢ ⁢ M - 1 ⁢ f i + j - k j for ⁢ ⁢ i = 0 , 1 , … ⁢ , N - M and also includes said dilation operator defined by F ⁢ ⁢ Θ ⁢ ⁢ K ⁡ ( i ) = max j = i - M + 1 , ⁢ … ⁢ , ⁢ i ⁢ f j + k i - j for ⁢ ⁢ i = M - 1 , M , … ⁢ , N - 1 where F=[f 0 , f 1 , . . . ,f N-1 ] is a discrete input signal comprising said first time series, and where K=[k 0 , k 1 , . . . , k M-1 ] is a predefined discrete kernel function, or structure element or SE, and where N and M are two integers that N>M and where M is set dynamically to min(W max , max(W min , K×CL+d)) where K is user-programmable or selectable from a predetermined range, CL is the mean cardiac cycle length expressed as the number of samples over the previous H heart beats where H is a predefined positive integer, d is a predefined offset constant, W min is the lower boundary of SE width, and W max is the upper boundary of SE width.