Abstract: A method and apparatus for monitoring the status of a patient on the basis of a plurality of vital signs measurements such as heart rate, breathing rate, blood pressure, temperature, oxygen saturation etc. At each time point a set of such vital signs measurements is compared to two statistical models, one being a population-based statistical model representing the probability distribution of measurements from a large number of individuals, and the second is a patient-specific statistical model based on measurements from the particular patient being monitored. The patient-based statistical model is initialized as identical to the population-based model, but then is updated in a Bayesian update technique so that it evolves towards the patient's individual state. First and second novelty indexes are calculated by comparing each status measurement to each of the two statistical models.

Abstract: At least two waveforms indicative of respiration are extracted from cardiac signals such as PPG or ECG. The extracted waveforms are converted into the frequency domain and multiplied together to form a combined frequency response function representing the frequency content of the combined respiratory waveform. Up to three peaks in the combined frequency response function are identified and averaged to provide an improved estimate of the breathing rate.

Abstract: A PPG or other cardiac signal is analysed by calculating its amplitude in a narrow frequency range around the estimated heart rate or a harmonic of the heart rate. Cardiac signals from a patient in different states, e.g., exercise and non-exercise or limb lowered and limb raised can be analysed and the amplitude in the narrow range compared to determine various vascular conditions such as peripheral arterial disease.