Medical Applications User Guide (pdf) - Freescale Semiconductor

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Diagnostic and Therapy Devices 17.2 Using Motors for Patient Positioning Pressure ulcers or decubitus ulcers (bedsores) are one of the most common complications of patients who cannot change position in a bed. Bedsores can be caused by sweat, humidity and temperature but are mainly the result of unrelieved pressure applied by the bones to the skin and tissue. This is why the most common places for bedsores are the sacrum, elbows, knees and ankles. To avoid bedsores, hospitals and health care providers use irregular bed surfaces to distribute pressure along the whole body while electric motors allow the patient easily switch positions with just the push of a few buttons. Electric motors are clean and relatively efficient. This makes them a much better fit for use in hospital beds rather than pneumatic or hydraulic alternatives. An electronic motor system can be used to adjust the height of the bed and provide movement to the bed’s wheels. A typical system containing an MCU, an H-bridge and a motor is shown in Figure 17-2. The requirements for an MCU vary based on the size of the motor and the required efficiency. Most patient bed applications require between 32 to 100 MHz, 16 to 156 KB of flash memory, 2 to 64 KB of SRAM, a highly accurate timer and the ability to synchronize the timer with the analog to digital converter (ADC). The requirements for an H-bridge also vary, but most beds require a monolithic power IC comprising control logic, charge pump, gate drive and low RDS(ON) MOSFET output H-bridge circuitry in a small surface mount package. Freescale offers a wide variety of products specifically for motor control systems ranging from digital signal controllers (DSC) to MCUs and H-bridges. An ideal MCU and H-bridge solution for a bed is an MCF51AC256 paired with the flexible, low-power MC33926. In Figure 17-1: Powered Patient Bed General Block Diagram Powered Patient Bed Infusion Pump Motor Driver Patient Monitor Power Management Infusion Pump Control Patient Monitor Control Other Devices Freescale Technology Optional some cases, depending on the complexity of the motor system, a single DSC may be sufficient to control the motor. Freescale’s MC56F800x family is an alternative costoptimized solution for real-time motor control. 17.3 Integrated Real-Time Patient Monitoring A powered patient bed must be equipped to monitor the status of the patient and transmit the data remotely to a nurse station. Typical patient monitoring functions consist of blood pressure monitoring, heart rate monitoring, a pulse oximetry unit, ECG, blood glucose meters and an infusion pump. The modules shown in Figure 17-1 provide extra features allowing health care providers and the patient’s relatives to offer comfort to the patient. Some of these modules include a tilt accelerometer and motor driver to control the bed’s tilt, powered wheels to facilitate movement of the patient to different areas of the hospital, USB and Ethernet ports to provide connection with a PC or the hospital network, VoIP gateway to provide direct communication to the nurses’ station, and an LCD screen and keypad for user interface. 17.4 Integrated Tilt Control The tilt control module is used mainly for the safety and comfort of the patient. Although hospital beds are often maneuvered in many directions and in some cases, in an urgent manner, the safety of the patient must be paramount at all times. Electronic sensors can be used to monitor the tilt of the bed and provide an alarm if the bed is at an unsafe angle. Furthermore, the tilt control module is used to position the patient in the bed at the most ideal angle for the patient’s comfort. This is the most prevalent use of the tilt control module. Accelerometers can be used to measure both dynamic and static acceleration. Tilt is a static measurement where gravity is the acceleration being measured. Therefore, to achieve the highest degree of resolution of a tilt measurement, a low-g, high-sensitivity 90 Medical Applications User Guide UART UART UART LCD Controller LCD Display MCU/MPU SPI USB MII Keypad or Touch Screen Wireless Comm IEEE ® 802.11x Wi-Fi ® 10/100 Ethernet PHY CAN XSCVR Accelerometer CAN Bus CAN XSCVR Bed Tilt Control Motor Driver Bed Tilt Motors Nursing Station Wired Network CAN XSCVR Wheel Motor Control Motor Driver Wheel Motors VoIP Gateway to Public Phone Network Pressure Sensor CAN XSCVR Pump Control Motor Driver Pump Motors
accelerometer is required. The Freescale MMA845xQ series accelerometers are ideal solutions for XY and XYZ tilt sensing. A simple tilt application can be implemented using an MCU that has one or two ADC channels to read the analog output voltage of the accelerometers. For a safety application, an I/O channel can be used to send a signal to the MCU to turn power a particular medical device at a determined angle. Selecting the right accelerometer depends on the angle of reference and how the device is mounted. This allows the designer to achieve a high degree of resolution for a given solution due to the nonlinearity of the technology. To obtain the most resolution per degree of change, the sensor must be mounted with the sensitive axis parallel to the plane of movement where the most sensitivity is desired. For example, if the degree range that an application is measuring is 0° to 45°, then the printed circuit board (PCB) would be mounted perpendicular to gravity. An X-axis device would be the best solution. 17.5 Integrated Intercom Using VoIP VoIP intercom applications can improve communication throughout a facility across either wired or wireless networks. Maintaining support resources for only one network can lead to substantial cost savings, however, the greatest opportunity lies in the ability to deploy and integrate new productivity applications and enhanced voice services. A VoIP gateway, for instance, can help seamlessly integrate a patient’s monitored data into the underlying hospital network. Figure 17-2: Electronic Motor System V DD MCU A VoIP intercom application should deliver an attractive and intuitive user interface and maintain good audio quality from end to end with options for video connectivity. No additional switching equipment is required to implement these systems across an existing network. To meet these needs, the system MPU must feature a high level of integration to simplify a design for seamless video, voice and network connectivity. It must have enough processing performance and network bandwidth to simultaneously transfer data from many sources, including a keypad, touch screen display panel and voice inputs and outputs. Freescale offers a comprehensive hardware and software solution for commercial VoIP applications that meet these specific requirements. The i.MX product family contains processors up to 800 MHz with the proper mix of memory and peripherals for creating the VoIP solution. freescale .com/medical 91 SF FB IN1 IN2 INV SLEW D1 D2 EN Diagnostic and Therapy Devices 33926 VPWR CCP OUT1 OUT2 PGND AGND Motor V PWR
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Medical Applications User Guide TM
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freescale.com/medical 3 Introductio
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Introduction 1.1 Freescale Offers T
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Monebo Kenetic ECG Algorithms Free
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Home Portable Medical 2.1 Introduct
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3.2 Home Health Hub (HHH) Reference
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3.3 Power Management Every design n
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MC34704 The MC34704 is a multi-chan
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3.7 How it Works The external capac
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eliably monitor and manage non-crit
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3.19 Standard Medical USB Communica
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Freescale has developed sample code
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4.2 Heartbeat Detection The heartbe
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4.6 Blood Pressure Monitor Referenc
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MCF51MM: Flexis 32-bit ColdFire V1
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Heart Rate Monitor 5.1 Introduction
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Instrumentation amplifier requireme
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6.2 Test Strip A test strip consist
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fully featured products at lower co
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Page 41 and 42: 7.2 Signal Acquisition This applica
Page 43 and 44: AN4327 Pulse Oximeter Fundamentals
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Page 47 and 48: Xtrinsic Touch-Sensing Software Xtr
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Page 75 and 76: Vital Signs 14.1 Introduction A vit
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Page 87 and 88: segments. Devices start from 128 KB
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Page 95 and 96: 18.2 Ultrasound Ultrasound is a non
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Page 103 and 104: Summary Summary Applications Freesc
Page 105 and 106: Appendix Digital Signal Processing
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Medical Applications User Guide (pdf) - Freescale Semiconductor

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