TENSIOMETER

When we measure blood pressure, we are observing the pressure exerted by the blood on the wall of the artery and the reaction of that artery before the aforementioned pressure in mm Hg. Therefore, taking into account these two factors, the pressure of the blood and the pressure of the vessels, can be considered different variables:

Systolic pressure: the one that exerts the heart in its movement of systole and transmits to the blood that circulates through the arteries. Diastolic pressure: minimum pressure of cardiac movement. It also represents the resistance offered by the vessels to the passage of blood. Differential pressure or pulse: difference between systolic and diastolic pressure. When this difference represents a circulatory difficulty to the passage of blood through the arteries. Dynamic average pressure: mean of both pressures, systolic and diastolic, although its figure is not an authentic arithmetic mean, but it is represented as 1/3 of the systolic plus 2/3 of the diastolic. Each of these pressures has a meaning for the maintenance of the homeostasis of the organism. Thus, for example, an increase in systolic pressure can rupture an artery and cause a hemorrhage[1].

TENSIOMETER PARTS

Pear: Inflatable component of neoprene-that develops the occlusion of the blood fluid in the patient [2].

Bracelet: It is the cover in which it wraps around the neoprene bladder and together they wrap the patient's limb to develop the blood occlusion[2].

Knob: Flexible device neoprene used to inject the air fluid that will circulate[2] .

Tubes Hoses: It is the one that joins the pump with the bag and the manometer[2].

Manometer: Instrument used to measure pressures, their units are mmHg[2].

MPX5100dp

The MPX5100DP piezoresistive pressure sensor is a state-of-the-art transducer with a wide range of applications. Because it delivers an analog output it is recommended to be used with a microcontroller or development card with ADC. This sensor is of high precision and is also compensated by temperature. [3]

• Working pressure: 0 to 100 kPa (0 to 14.5 psi).

• Working voltage: 0.2 to 4.7 V.

• Packaging: Freescale 867C.

• Accuracy: 2.5%.

• Working temperature range: -40 ° C to 125 ° C.

• Current: 7mA.

SOLENOID VALVE

A solenoid valve is also known as a general purpose solenoid valve. It is a valve that opens or closes the passage of a liquid in a circuit. The opening and closing of the valve is carried out through a magnetic field generated by a coil in a fixed base that attracts the piston.[4]

COMPRESSOR

A compressor is a machine, whose job is to increase the pressure of a fluid. Unlike other types of machines, the compressor increases the pressure of compressible fluids such as air and all types of gases.[5]

Characterization of the MPX5100DP

It was performed by measuring the voltage thrown at the output of the MPX5100DP sensor with respect to the change of pressure by pressing the bulb of the monitor which was displayed on the manometer.

ELECTRIC CIRCUIT

Now using the sensor characterization, we do a code to controlate the solenoid valve, to inflate and deflate the bracelet first we declarate the variables to detectect pulses, sistole and diastole pressure. in addition, like each code in arduino, we declarate the inputs and outputs.then we stars the program with the switch called PRIMER to inflate the bracelet until a pressure less than 155 mmHg.

when the condition of pressure is greater than 155 mmHg, we activate a flag called PR to stop the instruction of inflate. the digital output 9 is off, to start the reading sensor and keep data of pressureit in a vector during the disinflation. Then we proceed to perform a pre-measured pressure data to detect the systolic and diastolic pressure.

The last step is show the pressure data in LCD and activate alarms accordint to patient diagnostic. to add you can evaluate the pulse with optical voltage comparator and detect in 15 seg howmany pulse had the patient.

Results

The practice of blood pressure monitor was carried out based on the differential pressure sensor MPX5100DP to be able to check the Blood Pressure in a person. When performing the characterization the voltages we obtained depending on the pressure detected by the sensor were on the mV scale, therefore amplified 10 times with a non-inverter operational amplifier.

After amplification, the voltage was measured at each pressure in patients and we obtained response in the order of V, table 1 shows these voltage values relative to the pressure and the pressure vs voltage graph Displays the linear behavior of the sensor.

Already ready the signal was treated with the Arduino displaying values in the serial monitor. To check the pressures and that there were no voltage changes, he put the cuff on an empty thermos. Table 2 corresponds to these values with respect to each pressure value and the Arduino vs pressure graph shows the behavior of this relationship, which is also linear.

When making measurements it was corroborated that there were no voltage variations so the sensor was properly characterized, as the first noise that is heard is systole and the second the Diastole the program had to identify these voltage changes that were Small.

Measurements were made with three patients, oblivious to the class and the voltage measurements were started and then converted to pressure. These voltages were correct compared with those that we had already characterized and only detracted to convert them by reason of the pressure to be shown in the LCD.

The two pressures, systolic and diastolic, were visualized on the LCD screen and corroborated those values evaluated the pressure with the stethoscope. Finally, the average pressure was found by means and shown in the LCD along with the two required pressures and, in addition, the patient's pulse.

Analysis of results

The results show that, in the system designed for the taking of blood pressure, the differential sensor and its conditioning, the power stages for solenoid valve and compressor, functioned properly, because the process of insufflate and Desinsufle is Made automatically and, in addition, when comparing the pressure indicated on the manometer in this process and the one displayed on the LCD corresponding to that detected by the sensor, there was coincidence.

In addition, the program carried out in Arduino, allowed the obtaining of the systolic blood pressure, diastolic and mean, throwing values very close to the pressures evaluated with stethoscope listening to the sounds of KorotKoff the first corresponds to the systolic and The second to the diastolic, it was verified that the program performs its function. The process started by pressing a button, it was automatically inflated and when it reached up to 160 mmHg, it deflated and the program threw the values of the pressures to be displayed on the LCD.

GLOSSARY

Blood pressure:Blood pressure is the force of your blood pushing against the walls of your arteries.

Sensor: A sensor is everything that has a property sensitive to a magnitude of the medium, and by varying this magnitude also varies with some intensity the property, that is, it shows the presence of said magnitude, and also its measurement.

Valve: Device that opens or closes the passage of a fluid through a duct in a machine, apparatus or instrument, thanks to a mechanism, pressure differences, etc.

Piezoresistive:The electrical resistance of piezoresistive materials depends on the temperature (especially in the case of semiconductors). In contrast to the piezoelectric effect, piezoresistivity only causes a change in resistance and does not produce electrical potential.

Digital Analog Converter: An analog to digital converter or converter (Digital Analog Converter, CAD, Analog-to-Digital Converter, ADC) is an electronic device capable of converting an analog signal, either voltage or current, into a digital signal through a quantifier and coding in many cases in a particular binary code.

The wavelength: is the real distance a disturbance goes through in a certain time interval. That time interval is the interval between two consecutive maximums of some physical property of the wave.

BIBLIOGRAPHY

[1]Uv.es. (2018). [online] Available at: https://www.uv.es/inferm/HTA2.

[2] Futuras médicas. (2010). El tensiómetro. Recuperado de: https://futurasmedicas.weebly.com/tensiometro.html

[3] Estrada, R. (2018). Sensor de presión MPX5100DP Diferencial. [online] HeTPro. Available at: https://hetpro-store.com/sensor-de-presion-mpx5100dp-diferencial/

[4] [1]"Electroválvulas", Altecdust.com, 2018. [Online]. Available: https://www.altecdust.com/soporte-tecnico/que-son-las-electrovalvula.

[5]"Compresor", Mundocompresor.com, 2018. [Online]. Available: https://www.mundocompresor.com/diccionario-tecnico/compresor.