Vital Signs Monitoring Wearable Computer By Naresh Trilok Shreenath Laxman

Abstract Acquire data continuously and provide a complete history of the patient and also provide real-time feedback as a warning of medical emergency. Equipped with special sensors and tools from signal processing to measure the vital physiological variables depending on the kind of patient. Communication with the central server using telemetry. Application software to manipulate acquired data and present in usable form to doctors and nurses.

Vital physiological variables Pulse Rate. Blood Pressure. Temperature. Percentage of Oxygen Saturation in blood. Electro Cardio Graph.

Block Diagram Sensor Assembly Signal Conditioning Analog Signal A/D Converter TDM Telemeter Transmitter

Pulse Oximeter Measures Sa0 2. RBC’s are responsible for transport of oxygen. Using light attenuation to determine saturation. Beer’s Law I = Io * e ^-(a*d*c) a is the absorption coefficient d is distance c is concentration of absorbing substance.

Light travels through your finger

Photodetecter LED Transimpedance Amplifier Differential Amplifier Low Pass Filter Function Generator SOFTWARE

Type of light

System Trans impedance Amplifier. Differential Amplifier. Low Pass Filter. Using signal from hardware, output three things Ratio of Ratio Oxygen Saturation Heart Rate

Ratio of Ratios Extension of Beer’s Law: -Low = Io*exp(-  ( )d+  A ( )  d) -High = Io*exp(-  ( )d) -Simplify Expression by Taking ratio of Low to High -Low/High = exp(-  A ( )  d) Eliminates dependency on distance and reduces to standard equation for ratio of ratios -Ratio = (  A ( R))/ (  A ( IR)) = Ln (RL/RH) / (ln(IRL/IRH))

Oxygen Saturation S a O 2 = {(  Hb ( R ) -  Hb ( IR )R) / (  Hb ( R ) -  HbO2 ( R ) + [  HbO2 ( IR ) -  Hb ( IR )]R } * 100. Extinction Coefficients are known: - HbR =.81; - HbO2R =.08; - HbIR =.18; - HbO2IR =.29

Heart Rate Determination Dependent on period of signal. Heart Rate = (Sample Rate * 60) / No. of samples per period. Software uses loop to find the index (location) of two consecutive peaks. Subtracts the two indexes from one another to determine No. of samples per period. Then determines heart rate.

Temperature Telemeter

Temperature Telemeter contd… Oscillator circuit operates in the "blocking" mode. The circuit generates a 1 MHz. radio signal that pulses ON and OFF at a rate (blocking rate) set by a capacitor and the resistance sensor (Thermistor). The biotelemeter's signal can be picked up by a nearby AM broadcast band receiver. The clicking rate (i.e.: clicks per minute) carries the measured temperature information as reflected in changes in the resistance sensor. It can be miniaturized.

Server end Telemeter Receiver TDD Application Software

Server end