Apparatus and method for determining a blood pressure of a subject

An apparatus for determining a blood pressure of a subject, comprising:

• a sensor assembly configured to measure a pulse wave signal of the subject;
• and
• a signal processor configured to generate a metric of the pulse wave signal based on the pulse wave signal, to select a blood pressure calculation algorithm based on the metric of the pulse wave signal, and to determine the blood pressure of the subject using the blood pressure calculation algorithm;
• wherein the signal processor is configured to perform time domain analysis on the pulse wave signal of the subject,
• the metric comprises a metric in time domain of the pulse wave signal;
• the metric in time domain of the pulse wave signal comprises at least one of (1) a ratio between amplitudes at two reference points in the time domain of the pulse wave signal;
• (2) a ratio between Δt1 and Δt2 in the time domain of the pulse wave signal, wherein Δt1 is a first time difference between a first pair of reference points, and Δt2 is a second time difference between a second pair of reference points;
• or (3) a ratio between S1 and S2, wherein S1 is a first area defined by a first pair of reference points under a curve of a time domain representation of the pulse wave signal, and S2 is a second area defined by a second pair of reference points under the curve of the time domain representation of the pulse wave signal;
• wherein the signal processor is further configured to perform time-frequency domain analysis on the pulse wave signal of the subject;
• the metric comprises a metric in time-frequency domain of the pulse wave signal;
• and
• the metric in time-frequency domain of the pulse wave signal comprises a correlation between a frequency domain metric and a time domain metric.

A method of determining a blood pressure of a subject, comprising:

• measuring a pulse wave signal of the subject;
• generating a metric of the pulse wave signal;
• determining the blood pressure of the subject using a blood pressure calculation algorithm;
• performing time domain analysis on the pulse wave signal of the subject;
• and
• performing frequency domain analysis, and time-frequency domain analysis;
• wherein the metric comprises a metric in time domain of the pulse wave signal, a metric in frequency domain of the pulse wave signal, and a metric in time-frequency domain of the pulse wave signal;
• and
• the metric in time domain of the pulse wave signal comprises at least one of (1) a ratio between amplitudes at two reference points in the time domain of the pulse wave signal;
• (2) a ratio between Δt1 and Δt2 in the time domain of the pulse wave signal, wherein Δt1 is a first time difference between a first pair of reference points, and Δt2 is a second time difference between a second pair of reference points;
• or (3) a ratio between S1 and S2, wherein S1 is a first area defined by a first pair of reference points under a curve of a time domain representation of the pulse wave signal, and S2 is a second area defined by a second pair of reference points under the curve of the time domain representation of the pulse wave signal.