Using the method of multi parameter monitor and its measuring principle

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Release date: 2015-09-06 00:00:00

Source: Henan Meilun Medical Electronics Co., Ltd.

Monitor (monitor) can be real-time, continuous and long time detection in patients with some important characteristic parameters of life and has important clinical value. And this instrument can also be used for portable and mobile, and it has greatly improved the frequency of use. With the continuous development of sensing technology and Electronic Science and technology, patient monitoring technology has been developed rapidly. The monitoring parameters have been developed from the single parameter to many parameters, including ECG, blood pressure, body temperature, respiration, blood oxygen saturation, carbon dioxide, blood pressure, cardiac output, etc.. Are introduced in this paper using method of multi parameter monitor and its measuring principle, in the following pages in small series will with you to share the knowledge of multi parameter monitor (multi parameter monitor principle).
Multi parameter monitor (monitor) can provide first-hand clinical information and a variety of life characteristic parameters for patient monitoring and rescuing patients, according to the monitor in the hospital we learned, various clinical departments in the use of the monitor are not able to do special plane. Especially new operators to monitor do not quite understand, cause there are many problems in the use of the monitor, for example, can not fully play instrument function, reduce the use rate and false failure rate is higher.
The basic structure, monitor
Monitor generally is composed of a physical module and a built-in computer system includes a variety of sensors. Various physiological signals are converted into electrical signals by the sensor, and the results are displayed, stored and managed by the computer after the pre amplification process. Multi function integrated monitor parameters can simultaneously monitor ECG, respiration, body temperature, blood pressure, blood oxygen parameters etc..
Plug-in combined monitor is a high-end monitor, it is by each of the separation of powers can remove physiological parameters module and a monitor host structure. The user can according to their own requirements to choose different plug-in modules to form a suitable for their own special requirements monitor. Monitor the display technology, digital tube display, CRT display, LCD (liquid crystal display), electroluminescent (EL) display.
Two, using the method of multi parameter monitor and its measuring principle
1 respiratory monitor
Multi parameter patient monitor respiration measurements are used in most of the thoracic impedance method, the human body in the process of respiration thoracic movement will cause changes in the human body resistance, variation is 0.1 ohm to omega-3s, called respiratory impedance.
Monitor is generally through two lead ECG electrodes, 10 ~ 100 kHz carrier frequency sinusoidal constant flow body is injected with 0.5 to 5mA current, thus in the same electrode respiratory impedance change of pickup signal. The change of respiratory impedance is described by the dynamic waveform of respiration and can be extracted from the respiratory rate parameters.
The movement of the thoracic and non respiratory movement of the body will cause changes in body resistance, when this change frequency and respiratory passages of the amplifier of the same frequency band, monitor is very difficult to determine the normal respiration signal which is, where is the motion interference signals. Therefore, when the patient has a serious and sustained physical movement, the measurement of respiratory rate may not be allowed.
2 invasive blood pressure (IBP) monitoring
In some severe cases, it has very important clinical value to monitor the real-time monitoring of blood pressure. The principle is that the catheter is inserted into the blood vessel through the puncture, and the external port of the catheter is directly connected with the pressure sensor, and the inner tube is injected with normal saline.
Because the fluid has a pressure transfer function, the pressure inside the vessel will pass through the catheter to the external pressure sensor. In order to obtain the dynamic waveform of the blood pressure, the systolic blood pressure, diastolic blood pressure and average pressure can be obtained by using a specific method.
In the blood pressure measurement, we should pay attention to: monitoring the start, the first of the instrument calibration zero processing; monitoring process, to keep the pressure sensor part and heart at the same level; to prevent the catheter is blood clot blockage, to continue to inject heparin saline irrigation catheter, because the movement may make the catheter moving position or exit. Therefore, we must firmly fixed catheter, and pay attention to check, when necessary adjustments.
3 body temperature monitoring
Temperature measurement monitor generally uses negative temperature coefficient thermistor as temperature sensor. General monitor to provide a temperature instrument, high-grade can provide double channel temperature. The type of body temperature probe is also divided into the body surface and the body cavity probe, respectively, to monitor the body temperature and body temperature.
When measuring, the operator can according to need the temperature probe is placed in any part of the body of a patient, due to the different parts of the human body with different temperature, then monitor the measured temperature value, that is, the patient body to discharge temperature of the probe site value, the temperature may differ from the mouth cavity or armpit temperature value.
In the body temperature measurement, the patient's body is measured with the sensor in the presence of a thermal balance problem, that is, when the probe is just started, because the sensor has not yet fully achieved balance with the human body temperature, so the temperature is not the part of the true temperature, it must go through a period of time to achieve the actual temperature. Also pay attention to maintain a reliable contact with the surface of the sensor, such as the gap between the sensor and the skin, it may cause low measurement value.

　　4 ECG monitoring
The "can be excited" in the heart of the electrochemical activity of the myocardium will cause the heart to be excited. To cause the heart to have mechanical contraction. The closure of the heart, the action current, flow in the body volume conductor, and spread to various parts of the body, so that the body of different surface parts produced a difference in current.
Electrocardiogram (ECG) is the potential difference between the body surface changes recorded in real time, lead is the concept of the human body is two or more than two of the potential difference between the surface of the heart and the change of the heartbeat cycle. The earliest definition of first, II, and III leads in the clinical practice as bipolar standard limb lead.
Then the aVR, V1, aVL, aVF, V4, V5,, V6, V2, V3,,,, and ECG were defined. Because the heart is a solid, a lead waveform represents a projection of the heart's electrical activity. These 12 leads, will be from 12 directions to reflect the electrical activity of different projection of the heart, you can be integrated diagnosis of different parts of the heart disease.
At present, the standard ECG is used in the measurement of ECG waveform, the limb electrode is to be placed in the wrist and ankle, while the electrodes are equivalent to the location of the patient's chest and abdomen, although the location is different, but they are equivalent, and its definition is the same. Therefore, the lead in the monitoring of ECG leads is the same as that in the ECG.
Monitor generally care three or six lead, the waveform can be displayed at the same time the A or two leads and by waveform analysis to extract the parameters of heart rate and the powerful function of monitor can care 12 lead, and waveform for further analysis, ST segment and arrhythmia events are extracted.
At present, the monitoring of ECG waveform is not very strong. This is because the purpose of monitoring is to monitor the patient's heart rate for a long time, and the results of the ECG machine is the result of short time measurement. So the amplifier of the two instruments is not the same as the width of the. Electrocardiograph bandwidth at 0.05 ~ 80Hz, and monitor the bandwidth of 1 25Hz in general. ECG signal is a relatively weak signal, easy to be outside interference, some types of interference is very difficult to overcome such as:
(1) motion interference. The movement of the patient's body will cause changes in the ECG signal. The amplitude and frequency of the motion is difficult to overcome in the bandwidth of the ECG amplifier.
(2) EMG interference. When the muscle contraction under the bonding ECG electrode, it will produce the EMG interference signal, the EMG signal will produce interference, and the EMG interference signal, with the same frequency spectrum bandwidth, and therefore, can not simply use the filter to clear.
(3) interference of high frequency electric knife. When the electric power is used in the operation, the electrical energy generated by the electric power is far greater than the signal and the frequency components are very rich, so that the ECG amplifier can reach saturation state, and the ECG waveform can not be observed. The current monitor almost all of such interference incapable of action. Therefore, the anti monitor electrosurgical interference part only in high frequency electric knife 5S monitor to recover after the withdrawal.
(4) electrode contact interference. Any interference from the human body to the electrical signal of the ECG signal can cause strong noise, which may cause the ECG signal to be blurred, which is often caused by poor contact between the electrode and the skin. This kind of interference prevention mainly from the use of method to overcome, the user should every time to carefully check each link, and the instrument to reliable grounding, which not only has the advantage of confrontation, but more important is to protect the safety of patients and operators.
5 noninvasive blood pressure monitoring
Blood pressure is the pressure on the blood vessel wall. During each contraction and dilation of the heart, blood flow to the vessel wall pressure changes, and the arterial vessel and venous pressure, different parts of the vascular pressure is not the same. Clinical often to upper arms of the human body and heart at different heights within the artery corresponding systolic and diastolic pressure values to characterize the human body blood pressure, systolic blood pressure (or pressure) and diastolic blood pressure (or pressure).
Arterial blood pressure in the human body is a variable physiological parameter. It has a great relationship with the people's mental state, emotional state, as well as the posture and body posture. Cardiac stroke volume increased, the pressure will increase. It can be said that the arterial blood pressure in each cardiac cycle is not absolutely the same.
Vibration method is developed in the 1970s noninvasive arterial blood pressure measurement method and its principle is using the cuff inflated to a certain pressure completely oppressed artery and occlusion of arterial blood flow, and then decreases with the increasing of the cuff pressure, arterial blood vessels will be presented by completely blocking closed, gradually open, open the change process.
In this process, due to the pulsatile arterial wall will be within the cuff of the gas generated gas oscillation wave, the oscillation wave and systolic blood pressure, diastolic blood pressure and mean pressure there is a corresponding relationship, through measurement, recording and analysis of the outgassing process within the cuff pressure vibration dynamic wave could be acquired parts of the contractile pressure average systolic and diastolic blood pressure.
The premise of the vibration method is to find the rules of the arterial pressure pulsation, in the actual measurement

6 arterial oxygen saturation (SpO2) monitoring
Oxygen is an indispensable material in life activities. The effective oxygen molecules in the blood are transported to the tissues of the body through the combination of HbO2 and hemoglobin (Hb). The parameters used to characterize the ratio of oxygenated hemoglobin in blood are known as oxygen saturation.
Noninvasive measurement of arterial oxygen saturation is according to the blood hemoglobin and oxyhemoglobin to light absorption characteristics of different, through the use of two different wavelengths of light (660nm) and infrared light (940) respectively through the organization after again by the photoelectric receiver converted into electrical signal, and made use of the other constituents of the tissue, such as skin, bones, muscles, blood and other absorption signal is constant, and only the absorption signal in the arteries of HBO2 and Hb is with the pulse as cyclical changes in the characteristics of the received signal can be processed and obtained.
Thus, this method can only measure the blood oxygen saturation in arterial blood, and it is necessary to measure the arterial blood flow. Clinical use of arterial blood flow and tissue thickness and thick parts of the organization to placing a sensor, such as fingers, toes, lobes and other parts. But when the measurement of the part of the measuring part of the sharp movement, it will affect the extraction of the regular pulse signal, can not measure.
When the patient's peripheral circulation is not smooth, it will lead to the decrease of the arterial blood flow, causing the measurement uncertainty. The body temperature of the patients with severe blood loss is lower, and when the probe is strong, the work of the photoelectric receiving device may deviate from the normal range. Therefore, the measurement should avoid the glare of light.
7 respiratory carbon dioxide (PetCO2) monitoring
Respiratory carbon dioxide is an important indicator for the patients with anesthesia and respiratory diseases. The measurement of CO2 mainly uses infrared absorption method, that is, different concentrations of CO2 to the absorption of specific infrared light. CO2 monitor has two kinds of main stream and side stream.
The mainstream type of gas sensor is placed directly in the patient's respiratory duct. Directly to breathing gas CO2 concentration conversion, and then the electric signal is transmitted to the monitor for processing and analysis, PetCO2 parameters are obtained. Side stream type optical sensor is placed on the monitor, by the gas sampling tube real time extraction of patient breathing gas samples and sent to monitor CO2 concentration were analyzed.
In CO2 monitoring, it is necessary to pay attention to the following issues: because the CO2 sensor is an optical sensor, in use process, must pay attention to avoid the severe pollution of the patient's secretions of the sensor; next to the stream CO2 monitor in general with a gas water separator can remove the breathing gas in water. Always check the gas and water separator is an effective work; otherwise the moisture in the gas will affect the accuracy of the measurement.
Believe that through introduction of the small series, we will use the multi parameter monitor and its measuring principle have deeper understanding. Measurement of various parameters itself will have some difficult to overcome the defects, although the intelligent degree of the monitor is to, but is still not completely take the place of human beings, still need to operating personnel to judgment and correct treatment. Operation process must be careful, the measurement results must be correctly judged.