Interference Suppression in Spectral Plethysmography

An apparatus for assessing a blood related parameter of a subject, the apparatus comprising:

• a measurement unit configured to measure at least one blood related signal from a subject;
• a transform unit configured to derive a power spectrum for at least one of the at least one blood related signal, thereby to obtain at least one power spectrum;
• a frequency identification unit configured to identify at least one interference frequency of at least one interference source causing unwanted modulation in the at least one blood related signal;
• a first calculation unit configured to determine a weight function in which the relative weight of at least one frequency is dampened, the at least one frequency depending on the at least one interference frequency;
• a weighting unit configured to apply the weight function to at least one of the at least one power spectnjm, thereby to obtain at least one weighted power spectrum;
• and
• a second calculation unit configured to define the blood related parameter based on the at least one weighted power spectrum.

An apparatus for assessing a blood related parameter of a subject, the apparatus comprising:

• measurement means for measuring at least one blood related signal from a subject;
• transform means for deriving a power spectrum for at least one of the at least one blood related signal, thereby to obtain at least one power spectrum;
• frequency identification means for identifying at least one interference frequency of at least one interference source causing unwanted modulation in the at least one blood related signal;
• first calculation means for determining a weight function in which the relative weight of at least one frequency is dampened, the at least one frequency depending on the at least one interference frequency;
• weighting means for applying the weight function to at least one of the at least one power spectrum, thereby to obtain at least one weighted power spectrum;
• and
• second calculation means for defining the blood related parameter based on the at least one weighted power spectrum.