As the population continues to grow and age, automated patient monitoring systems are becoming more and more popular. Their popularity is not only due to low cost, but also consistency and repeatability. Surveillance devices with sensors in this category are also versatile because they can be used both in hospitals and at home.
Let's take a look at what high-tech sensors can be applied in the automatic patient monitoring system to help us cope with the problems of the future aging society.
1.Implantable sensors
Implantable sensors must be small, lightweight, weight-compatible, and require little power to operate. Most importantly, they must not decay over time. Because they are Class III medical devices, they automatically require FDA approval.
Implantable sensors typically require two to four years of development and implementation time before entering production. Generally, they are more expensive and require specialist surgery to implant them. Power requirements are one of the main challenges of implantable sensors, so sensors that can operate without power are ideal choices, but such sensors are rare on the market.
For example, piezoelectric polymer sensors are one of those sensors that can operate without a power source. It is small, reliable, durable and requires no power, making it ideal for vibration detection. Such sensors can be used in pacemakers that monitor patient activity.
The shape of the piezoelectric polymer sensor is a tiny cantilever beam with a weight attached to one end and descending as the human body moves. The sensor generates a signal each time the patient moves.
Take a pacemaker as an example. The pacemaker then receives the signal and beats the heart at the required speed. Sensors can distinguish various activities such as walking, running or other physical activities. If the patient is resting, the signal will be zero and the pacemaker will beat the heart at the minimum rate. In this way, the sensor signal is proportional to the level of activity.
The miniature piezoelectric thin film vibration sensor is 15/100 inches in length and includes a pacemaker. The implanted sensors can also be powered by an external power source. For example, when a radio frequency (RF) energy bar is placed near a sensor inside the human body, it will power the sensor, and then the sensor will record the patient's measurement results, transmit the data back to the energy bar via the RF link, and then return to sleep. Another example of using an implantable sensor in this way is a retroabdominal aortic aneurysm surgery, where the implantable sensor can monitor pressure leaks at the surgical site.
2.Sensors in the catheter and body cavity
Compared to sensors implanted in the human body, sensors inserted through the incision (usually at the tip of the catheter) are less stringent, but still require FDA approval. Depending on the surgical procedure, these sensors can run for minutes to hours and can be powered by an external power source.
We can guide a pair of matched thermistors at the end of the catheter to different locations in the heart to measure blood flow. They can be heated by coils or rinsed with cold fluid to measure blood flow. When flushed with cold fluid, the first sensor cools more than the second because the blood stream heats the fluid that reaches the second sensor. Because the two temperature sensors are at a known distance, the temperature and volume of the fluid can be controlled at this distance, and the blood flow can be calculated by reading the difference between the two sensors' resistance values. These thermistors do not require an external power supply.
3. Catheter ablation sensor
Catheter ablation sensors are temporarily inserted through an incision and include a radio frequency energy source and a load cell.
Radio frequency energy (like the radio frequency energy used by implantable sensors to send data) is often used during ablation to burn away dead tissue. It is essential that the force applied to the target tissue by the catheter tip does not exceed the maximum value to avoid any possibility of perforating the target tissue
4.Disposable MEMS pressure sensor
Disposable MEMS pressure sensors can be used in intrauterine pressure (IUP) sensors to measure systolic pressure and frequency during delivery. This method is more reliable than conventional belts and is used in emergency situations. Other functions can be built into these sensors, such as amniotic fluid infusion and withdrawal. These sensors are inserted through the uterus and reside in the amniotic sac. The sensor is removed when the baby is ready to give birth.
5.Body cavity sensor
Body cavity sensors include oral and rectal probes that measure body temperature. These temperature sensors are designed to be small and sturdy and covered with a soft coating material to protect the inner layers of the patient's organs from damage from contact.
6.Miniature thermocouple sensor
Miniature thermocouple sensors are flexible fine gauge thermocouples that can be used when fast and accurate temperature measurements are required. Thermocouples consist of two different metals, connected at one end. The two metals produce a small, unique voltage that can be measured and interpreted by a thermocouple thermometer. The dissimilar metals are individually insulated, and a protective layer is present to maintain a compact two-wire structure. Miniature thermocouples are made from only biocompatible materials, making them suitable for medical applications.
7.External sensor
External sensors are disposable sensors that can make contact with the human body through body fluids, but they are still located outside the human body.
Such as disposable blood pressure sensors (DPS). Disposable blood pressure sensors are used in surgical procedures and in intensive care units (ICUs) to continuously monitor patients' blood pressure. This is a reliable method for measuring blood pressure during surgery or intensive care units, by inserting a disposable blood pressure sensor into the monitor to record the patient's information profile. It should be noted that it needs to be replaced every 24 hours to avoid pollution.
Another sensor that comes in contact with drugs and body fluids is the one used for angioplasty balloon inflation. The pressure sensor at the pump tip will be in contact with a saline solution that is used as a medium to inflate and deflate the balloon. In this application, a pressure sensor monitors the pressure applied to expand / contract the balloon and needs to withstand pressures above 200 psi. If too much pressure is applied, the balloon may burst and cause serious complications to the patient.
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