The invention relates to a monitoring apparatus for monitoring a physiological signal. A segmentation unit (4) determines signal segments from a physiological signal, which correspond to periods of the physiological signal, a classification unit (5) classifies the signal segments into a valid class and a non-valid class based on characteristics related to the signal segments, and a physiological information determination unit (7) determines physiological information from at least one of i)signal segments classified into the valid class and ii) signal segments classified into the non-valid class. The physiological information can therefore be determined based on the knowledge whether the respective signal segment is valid or not. For example, a physiological parameter like a breathing rate can be determined depending on valid adapted segments of the physiological signal, which are adapted to periods of the physiological signal. This improves the quality of determining physiological information from a physiological signal.
