| Sensors play an important role in satisfying our | | | | However, such a system allows for continuous |
| inquisitiveness to know about our surroundings. By | | | | monitoring of a patient's differential change in |
| far, temperature is the most measured parameter | | | | temperature. An array ofthermocouples can be used |
| using a sensor. The most primitive method to | | | | to measure temperature from different significant |
| measure would have been by touch and then by the | | | | parts of the body. With the use of thermocouples, |
| use of external metals. The initial measurements | | | | only one junction of each thermocouple will be closer |
| were just comparative and did not have a scale. | | | | to the surface towards the patient whilethe interface |
| Sensors have come a long way from that point and | | | | circuit can be hidden within the mattress. |
| we now have highly accurate measuring devices. | | | | Humidity Sensing |
| With advances in technology, various sensors | | | | A humidity sensor can be integrated into the hospital |
| measuring pressure, humidity, proximity, and motion, | | | | mattress to check either the perspiration level or for |
| among others, have been developed. To form a | | | | conditions like incontinence. Though excessive |
| complete application, however, use of these | | | | perspiration is not a disease in itself, it might be a |
| stand-alone sensors is not enough. | | | | revealing symptom. |
| Sensors must be interfaced to a microcontroller to | | | | Measuring the variation in perspiration will help log the |
| form a complete system. Interfacing sensors with | | | | information for certain medical conditions. It can also |
| microcontrollers has revolutionized different | | | | give an indication to the medical caregiver to attend |
| applications and is continuing to do so. Many fields like | | | | to the patient when required. Multiple humidity |
| medical, industrial, and automotive are benefiting from | | | | sensors can be arrayed, like in the case of |
| the latest innovations in sensor technology. Until | | | | temperature sensors, depending upon the patient and |
| recently, sensing has been implemented using | | | | caregiver's requirements. |
| hardwired circuits, which can be inconvenient to | | | | Capacitive and Proximity sensing |
| deploy in the areas where they are mounted. To | | | | A capacitive sensor can be used to detect the |
| simplify deployment, next-generation sensors are | | | | presence of the patient on the bed. If the patient |
| transferring the data they record using wireless | | | | has a case of unconscious movement, the |
| technology. A microcontroller that can interface with | | | | capacitance measured will fluctuate with each change |
| sensors and also has wireless capabilities makes | | | | in position. If the patient is moving restlessly or if the |
| continuous monitoringof received data possible. | | | | patient is out of bed when he/she is not supposed |
| This article explores the technology involved in | | | | to, the system can trigger an alarm for the medical |
| interfacing of sensors for medical applications, using | | | | caregiver. Utilizing the same technology as a |
| hospital beds as an example. Hospitals are places | | | | capacitive sensor, a proximity sensor can be placed |
| where all of us have felt the need for a little more | | | | at specific locations in the bed or mattress, such as |
| comfort, and hospital beds/mattresses can be made | | | | close to the head post. By moving his or her hand |
| more comfortable through technological | | | | close to it, the sensor can be simply activated by |
| improvements possible using sensors and | | | | patients with special needs. This will help avoid the |
| microcontrollers. Making patients more comfortable | | | | situation where the patient has to call for help by the |
| helps the patients, doctors, and also medical | | | | press of a button, which requires more motor skills. |
| caretakers. | | | | Pressure sensing |
| Present-day systems use sensors that are hardwired | | | | Pressure sensors are important in medical conditions |
| to a PC next to the bed. The use of sensors detects | | | | where patients have moving disabilities. These |
| the conditions of the patient and the data is collected | | | | sensors will detect and prevent any unrelieved |
| and transferred using a microcontroller. Doctors and | | | | pressure on the patient’s body " for example, |
| nurses need to visit the patient frequently to | | | | monitoring the formation of a pressure ulcer. The |
| examine his/her current condition. Using the proposed | | | | mattress developed for automated body position is |
| system, data can be sent wirelessly to the nurses' | | | | discussed in [2]. Adding wireless transmission to |
| station, allowing continuous monitoring of the patient. | | | | capability will take it to the next level of comfort and |
| Such an approach also reduces the number of wires | | | | sophistication. |
| present in the already confusing patient environment. | | | | |
| This system can also be used at places other than | | | | Linking to the Nurse Station GUI |
| hospitals, including home monitoring of patients with | | | | Once a transmitter binds to a receiving station, data |
| special needs. | | | | can be sent to and collected by an application at the |
| For the purpose of this article, only temperature, | | | | receiving station that uses a GUI to monitor the data |
| humidity, pressure and capacitive sensors are | | | | from each individual sensor. GUI-based monitoring |
| addressed. Any other sensor that can be interfaced | | | | tools can simply display data or can be designed to |
| with a microcontroller can be used in a similar method. | | | | provide extensive display options and features. The |
| These sensors can monitor the condition of the | | | | GUI could also store setups, a particular useful |
| patient and, based on the thresholds chosen, record | | | | feature for enabling monitoring different parameters |
| useful data and/or trigger alarms for attention from | | | | in patients with different medical conditions. The |
| doctors or nurses over wireless networks. This will | | | | setup can be stored and loaded when a particular |
| not only help current patients, but the data recorded | | | | transmitter (patient) is connected. |
| can be helpful for case studies of certain medical | | | | Experimental system setup |
| conditions. | | | | In the experimental setup, the high limit of the |
| Choosing a wireless configuration | | | | temperature was set at 26 and the low limit was set |
| There are several microcontrollers available on the | | | | at 14. For the humidity, the high limit was set at 60. |
| market with the requisite wireless capabilities which, | | | | The alarm window also shows whether the high limit |
| when coupled with sensors, could implement a | | | | (H) or the low limit (L) was exceeded. Similar limits |
| wireless hospital bed. But in this proof of concept, | | | | can be set for the pressure or capacitance or any |
| performed at room temperature, a PSoC FirstTouch | | | | other sensor that is interfaced to the system. The |
| Starter Kit with CyFi Low-Power RF was used, with | | | | medical caregiver can monitor these graphs and can |
| a low power 2.4 GHz RF system built on direct | | | | switch between different patient charts and attend |
| sequence spread spectrum technology. | | | | to the patient as per the alarms. |
| On the transmission side, the sensors were | | | | |
| interfaced with a microcontroller and then connected | | | | Safety Considerations |
| to a wireless subsystem using a second | | | | Given the needs of the hospital environment, safety |
| microcontroller to process and send the data using a | | | | is a primary concern. When a system is powered |
| wireless transmitter. At the receiving station, a | | | | through wired lines, not only does it require the |
| wireless receiver (PC Dongle) is connected to the | | | | manual installation of wires, it also poses the threat |
| computer, which collects and displays the data on the | | | | of electrical shock in case of short circuit. A |
| monitoring station through a Graphical User Interface | | | | battery-powered wireless sensor system, on the |
| (GUI). Designing the sensor and wireless subsystems | | | | other hand, avoids such safety problems. The |
| as separate boards facilitated testing of different | | | | wireless system can be made to run in full power |
| sensor interfaces over the wireless network. For the | | | | mode, low power mode, or switched off based on |
| final system, these two subsystems would likely be | | | | the requirement to ensure longer battery life. The |
| integrated into a single unit. Each transmitter has a | | | | bed/mattress system will need an access panel to |
| different ID associated with it, and a single receiver | | | | this battery to replace it when required. There had |
| can bind to different transmitters. Using such an | | | | been concerns in past, about electromagnetic |
| approach, multiple patients' can be observed from the | | | | interference (EMI) issues in hospitals due to use of |
| same station simultaneously. | | | | wireless technology. |
| The range of this wireless system is 400 m in line of | | | | After a detailed study [4], [5], it was shown that if |
| sight and 200 m within a typical hospital environment. | | | | recommended separation distances from medical |
| Thus it has the capacity of covering patients in one | | | | equipment are observed, then wireless technologies |
| floor and sending data to the nurse station in charge | | | | are suitable for use in hospitals including intensive care |
| for that area. As the receiver has to bind to a | | | | units and operating rooms. Extra care should be |
| particular transmitter, the data from the each patient | | | | taken in maintaining these distances when the patient |
| can be uniquely identified. | | | | has a pace maker or other life supporting medical |
| | | | equipment. Although sensors have been around for a |
| | | | long time, the wires attached to them have limited |
| Sensor Interface | | | | their applications range. The wireless sensor |
| The technology of interfacing the sensor with | | | | monitoring system in hospital mattress proposed in |
| microcontrollers already exists and there are | | | | this article improves patient comfort while freeing up |
| numerous articles in journals describing the methods. | | | | caregivers by providing continuous monitoring of |
| Adding wireless technology to the sensors given | | | | patients on many different levels. Monitoring is |
| below takes the system to the next generation. | | | | superior compared to wired systems which must be |
| Temperature sensing | | | | manually checked. Patients can be monitored without |
| Temperature sensors in the medical field have been | | | | being disturbed and caregivers have full access to |
| used from time immemorial to measure the body | | | | sensor logs using an intuitive, convenient interface. |
| temperature and monitor the medical condition of | | | | And, because of the convenience of wireless |
| patients. With a temperature sensor in the bed | | | | monitoring, this application can also be used in other |
| mattress, measurement of absolute temperature of | | | | places other than hospitals like homecare and |
| the patient will not be accurate, as the sensor is not | | | | ambulances. |
| attached to the body. | | | | |