Abstract: The invention relates to a mechanism for determining the depth of sleep of a subject. In order to obtain information about the continuum of the depth of sleep in a user-friendly way without a need for high computational power, EEG signal data is obtained from a subject, REM sleep periods of the subject are detected, and a measure indicative of irregularity in the EEG signal data is derived. Based on the measure and the depicted REM sleep periods, a sleep depth index and state information are produced, where the index is indicative of the depth of sleep of the subject and the state information indicates whether or not the EEG signal data is obtained during a REM sleep period. The detection of the REM periods may be based on a bioimpedance measured from EEG electrodes simultaneously with the EEG measurement or on EOG signal data measured from the subject.

Abstract: The invention relates to a method and apparatus for measuring the responsiveness of a subject with lowered level of consciousness. Physiological signal data is obtained from the subject and a first measure indicative of the level of consciousness of the subject is derived from the physiological signal data. In order to obtain an objective measure of the responsiveness of the subject and to improve the specificity of patient monitoring, a sequence of the first measure is recorded without inducing arousals in the subject and a second measure indicative of a responsiveness of the subject is determined based on the recorded sequence. The determination of the second measure may be independent of the unintentional stimuli that cause arousals in the patient or the stimuli causing such arousals in the clinical environment may be detected to find out their effect on the first measure.

Abstract: The invention relates to a mechanism for detecting whether a sleep state of a subject is due to natural sleep or induced by drugs. An indicator indicative of the activation of the autonomic nervous system of the subject is derived based on cardiovascular signal data measured from the subject and the indicator is employed to identify whether the sleep of the subject is drug-induced sleep or natural sleep. The identification is performed upon detection of a sleep state.

Abstract: The invention relates to a method and apparatus for measuring the responsiveness of a subject. Physiological signal data is obtained from a subject through at least one electrode attached to the skin of the subject and a first measure is derived from the physiological signal data, the first measure being indicative of signal energy in the physiological signal data on a frequency band where EMG activity appears. Recorded sequence of the first measure is subjected as input data to a morphological pattern extraction operation. The output data of the operation is indicative of presence of predetermined response waveforms in the input data and a measure of responsiveness is determined based on the output data.

Abstract: The invention relates to a mechanism for detecting whether a sleep state of a subject is due to natural sleep or induced by drugs. An indicator indicative of the activation of the autonomic nervous system of the subject is derived based on cardiovascular signal data measured from the subject and the indicator is employed to identify whether the sleep of the subject is drug-induced sleep or natural sleep. The identification is performed upon detection of a sleep state.

Abstract: The invention relates to a mechanism for determining the depth of sleep of a subject. In order to obtain information about the continuum of the depth of sleep in a user-friendly way without a need for high computational power, EEG signal data is obtained from a subject, REM sleep periods of the subject are detected, and a measure indicative of irregularity in the EEG signal data is derived. Based on the measure and the detected REM sleep periods, a sleep depth index and state information are produced, where the index is indicative of the depth of sleep of the subject and the state information indicates whether or not the EEG signal data is obtained during a REM sleep period. The detection of the REM periods may be based on a bioimpedance measured from EEG electrodes simultaneously with the EEG measurement or on EOG signal data measured from the subject.

Abstract: The invention relates to a method and apparatus for measuring the responsiveness of a subject with lowered level of consciousness. Physiological signal data is obtained from the subject and a first measure indicative of the level of consciousness of the subject is derived from the physiological signal data. In order to obtain an objective measure of the responsiveness of the subject and to improve the specificity of patient monitoring, a sequence of the first measure is recorded without inducing arousals in the subject and a second measure indicative of a responsiveness of the subject is determined based on the recorded sequence. The determination of the second measure may be independent of the unintentional stimuli that cause arousals in the patient or the stimuli causing such arousals in the clinical environment may be detected to find out their effect on the first measure.