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Breathe Safely – Embedded Electronics Helps Save Lives

Mon, 10/04/2010 - 11:59am
Christian Schuster, Head of Software Development MEN Mikro Elektronik, Urs Reidt, Head of Development HAMILTON MEDICAL, Switzerland
In the United States alone, error in medical treatments causes 98,000 deaths a year. For this reason, the American Institute of Healthcare Improvement (IHI) founded the “100,000 Lives Campaign”, an initiative to improve patient care and prevent unnecessary deaths. More than 3,000 hospitals across the country have enrolled in the campaign, representing 75% of hospital beds in the nation. The campaign’s main focus is to reduce the error rate by making simple changes everywhere in the healthcare system.

FIGURE 1: Avoiding VAP-related incidents is of paramount concern to hospitals, especially in critical ICU situations.Participating hospitals have pledged to implement up to six evidence-based and life-saving interventions as part of the campaign, including the prevention of Ventilator-Associated Pneumonia (VAP), a leading killer among all hospital-acquired infections. Improving artificial respiration for critically ill patients was identified as a key attribute of the campaign. Any hospital can implement this initiative along with the other initiatives identified by the IHI, particularly in ICUs. 

According to the IHI, intensive care is not only complex, but it is also costly. Errors caused in ICUs have reached unacceptable rates. In addition to VAP, the Joint Commission on Accreditation of Healthcare Organizations found other principle causes of errors to be inadequate orientation/training and communication breakdown between staff members. It is no wonder that with dozens of ventilation modes, a plethora of monitoring parameters, and at times, inadequate training, a healthcare provider can become easily confused and make life-threatening mistakes. Clearly, ventilators need to be simplified.

Reduce Complexity in the ICU
Achieving optimum respiration and precise diagnostics of lung function are crucial to instituting additional safety precautions for patients in ICUs as well as in post-anesthesia care units and emergency rooms. The control of a ventilator, including patient monitoring for invasive or non-invasive ventilation (with or without an artificial airway access), is integral to proper operation and reduced patient risk. Equipment must provide a user interface that improves safety through intuitive operation and monitoring, while offering superior performance in complex environments that improve patient outcomes without breaking the bank. Computer-On-Modules (COM) based on Embedded System Modules (ESM) have proven to be an ideal method for integrating the ventilators hardware with the electronics to provide seamless operation, improved monitoring, and ultimately, better patient safety.

Hamilton Medical, in conjunction with MEN Mikro Elektronik, utilized some of the latest trends in technology, including Adaptive Support Ventilation (ASV), to simplify the operation of ventilators and the interpretation of monitored data. Together, they developed a Ventilation Cockpit that intuitively visualizes the patient’s respiratory mechanics and ventilatory support, while equipping the ventilator with a failsafe feature that immediately sets off an alarm, calling a doctor or nurse to a patient’s bedside in case of an error.

Hamilton created two ventilators that utilize the Ventilator Cockpit model to alleviate errors in the ICUs. The compact unit (HAMILTON-C2) is mobile and optimal for high-performance mask ventilation in children and adults. Meanwhile, the larger unit (HAMILTON-G5) is a fully-equipped high-performance device with a wide array of diagnostic possibilities that include touch screen and one-knob operation, alarm lamp, interface for storage media, DVI interface, serial interface for PDMS or patient monitoring as well as an extended battery backup option. (Figure 2) 

Figure 2: Schematic diagram of information flow within the Hamilton-C5.

Ventilate Safely with Adaptive Support Ventilation (ASV)
ASV employs lung-protective strategies to minimize complications from Auto PEEEP (gas trapped in the airways that exerts a positive pressure, prohibiting normal gas transit to reestablish until pressure is increased from the mouth to the alveoli). ASV guides the patient into a favorable breathing pattern and promotes early weaning. Unlike conventional modes that require healthcare providers to set many parameters, closed-loop ventilation with ASV requires attention to just one: minute ventilation (the flow of gas). Studies show that ASV does the following:
• Ventilates virtually all intubated patients – whether active or passive and regardless of lung disease.
• Requires less user interaction by adapting to patient’s breathing activity more frequently and causing fewer alarms.
• Adapts to changes in the patient’s lung mechanics over time.

Sophisticated Embedded Electronics
The technology that went into both ventilators relied on the System-On-Module EM1A made of standard components and based on a reliable Power PC CPU. A 32-bit processor MPC5200 was used.

The Field Programmable Gate Array (FPGA) for these devices is very complex. Depending on the version, up to 32 standard and custom IP cores can be loaded into the FPGA. (Figure 3) 

Typical functions implements on the FPGA:

INPUT TYPE

FUNCTION

Up to 8 UARTs

Communication with data logger, microcontroller on carrier or different CO2 and O2 sensors

Up to 6 PWMs

Valve control; speed control of ventilators

Up to 60 GPIOs

General purpose inputs for system flexibility

2 SPI interfaces

Time-synchronous poling of A-D converters


UARTs: Universal Asynchronous Receiver/Transmitters
PWMs: pulse width modulators
GPIOs: general purpose I/Os
SPI: serial peripheral interface
A-D: analog-to-digital

Two 8-channel ADCs polled via the two SPI interfaces are located on the carrier board. The safety-critical SPI cores control and monitor ventilation pressure and flow. For the control aspect of the ventilator all eight channels of the two ADCs must be read once and the corresponding pulse width modulators must be written once every millisecond. The monitoring portion requires a reading of the ADC channels once every five milliseconds. Without participation of the Power PC CPU, the data is pre-processed, leaving 30 percent of the total system capacity remaining as a reserve for other tasks…even during the highest load level.

System communication is at the forefront of the ventilators’ design. In fact, the safe alarm feature operates via redundant monitoring of the EM1A through the processor and the carrier from Hamilton Medical via the microcontroller.

Because the ventilators need to be more sophisticated and easier to use to combat errors while maintaining transportability, the unique ESM concept that controls the devices offers the complete functionality of a standard computer in a much smaller space. Through the FPGA, the necessary flexibility and adaptability to the application are achieved. Connection to the device and the application-specific I/O (sensors, ventilators, etc.) is made possible through the unique carrier boards optimized for this purpose.

Patient Outcome Improved
By utilizing the latest technology, intelligent ventilation helps deliver superior performance in complex environments while reducing costs and saving lives.
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