Breathing a sigh of relief: Increased patient safety through advanced ventilator electronics
May 01, 2013
Compact, rugged computing modules lay the framework for lifesaving advancements in today's ventilator technologies. Increased ventilator control is pa...
Achieving optimum respiration and precise diagnostics of lung function via a ventilator are crucial to instituting safety precautions for patients in ICUs as well as in post-anesthesia care units and emergency rooms.
While ventilators are critical, lifesaving devices for patients unable to breathe on their own, as with any medical process, there are certain risk factors, particularly to those patients hooked up to a ventilator for an extended period of time.
Ventilator-Associated Pneumonia (VAP), an airway infection that can develop more than 48 hours after a patient has been intubated, is the leading cause of death amongst hospital-acquired infections. It exceeds even the rate of death resulting from central line infections, severe sepsis, and respiratory tract infections in nonintubated patients.
While preventing pneumonia of any variety is a goal of all medical care professionals, there are some reasons to be particularly concerned about the impact of pneumonia associated with ventilator use.
Perhaps the most concerning aspect is the high level of death associated with VAP’s onset. Hospital mortality of ventilated patients who develop VAP is 46 percent compared to only 32 percent for ventilated patients who do not develop VAP.
VAP prolongs time spent on the ventilator as well as the length of a patient’s time in the ICU and overall hospital stay after discharge from the ICU, adding an estimated $40,000 to a typical hospital admission.
Overall, the best defense is a good offense – reducing the amount of time a patient is intubated decreases the risks of VAP and associated complications. Better ventilator control will reduce the amount of time a patient spends intubated, and therefore decreases the risk of VAP (Figure 1).
Intuitive monitoring, enhanced operation
Ventilator control including patient monitoring for invasive or noninvasive ventilation (with or without an artificial airway access) is integral to reduced patient risk, proper operation, and optimum cost management. The quicker a patient comes off a ventilator, the less chance there is for VAP to occur.
The ventilator is an important piece of equipment as it must provide a user interface that improves safety through intuitive operation and monitoring, while offering superior performance in complex environments that improves patient outcomes without breaking the bank.
Thus, companies such as Hamilton Medical are developing innovative respiratory equipment such as the HAMILTON-S1 with its INTELLiVENT-ASV technology, providing automated adjustment of oxygenation and ventilation to meet the individual needs of the patient. The Adaptive Support Ventilation (ASV) technology features closed-loop control technology to reduce the patient’s ventilation time significantly.
Weaning time with such a ventilator can, under certain circumstances, be reduced by more than 50 percent in comparison to conventional ventilation, significantly reducing the risk of infections and lung damage (Figure 2). The integrated electronics within the unit help facilitate this important aspect of patient safety, and are described in the next section. Additionally, user setup requires much less health-care provider attention to main settings (see Sidebar 1).
Sophisticated embedded electronics go mobile
As medical equipment becomes mobile, meeting the requirements of volume and weight as well as temperature, drop, and humidity can be a challenge. The embedded electronics within these systems need to be robust, compact, and lightweight to keep pace with product developments.
Advanced computing performance and networking features are necessary to build up the backbone for the communication between medical devices and management systems as well as to increase patient safety.
Compact Computers-On-Module (COMs) have proven to be an ideal method for integrating the ventilator’s hardware with the electronics to provide seamless operation, improved monitoring, and ultimately, better patient safety. Because they are complete computers on a small module that can be placed inside a rugged housing, COMs offer tremendous technology and design benefits in medical equipment development.
These all-in-one modules comprise hardware (CPU, chip set, memory, I/O) that is not fixed to any application-specific function, and an FPGA programmed in VHDL code for user-defined I/O.
The modules are based on the Embedded Systems Module (ESM) specification developed by MEN Mikro that defines one 71 x 149 mm form factor very close to the PMC format. In fact, this allows the use of up to three ESMs on one 6U carrier card (for example, CompactPCI or VME) or one ESM and two PMCs. And support of an FPGA directly on the CPU module allows flexible user-defined I/O extension.
The versatile ESM modules incorporate a robust PCI-104-type connector and soldered components to withstand shock of 15 g for 11 ms and vibration of 2 g from 10 Hz to 150 Hz (sinusoidal) as well as bump of 10 g for 16 ms.
They have been designed to operate in temperatures from -40 °C to +85 °C and can be conformally coated for extra protection when used in harsh medical environments. This includes imaging equipment and patient monitoring devices that are becoming increasingly more portable, making volume, weight, temperature, drop, and humidity increasingly important considerations.
Many ventilators are relying on this ESM COM concept, utilizing standard components based on a reliable PowerPC CPU with a 32-bit processor operating at up to 400 MHz and 700 MIPS. The FPGA for these devices is flexible and, depending on the version, up to 32 standard and custom IP cores can be loaded into the FPGA (Table 1). 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, and so on) is made possible through carrier boards optimized for this purpose.
Processing requirements are high to ensure accurate patient monitoring. Two 8-channel ADCs polled via two Serial Peripheral Interfaces (SPIs) 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 ADC must be read at once and the corresponding pulse width modulators must be written once every millisecond, constituting the final act of the control cycle. The monitoring portion requires reading the eight ADC channels once every 10 milliseconds.
Without participation of the PowerPC CPU, the data is preprocessed, leaving system capacity remaining on the PowerPC as a reserve for other tasks. Therefore, even if the ventilation is working on highest load level, additional functions like interactions with the control panel will not cause ventilation interruption.
System communication is at the forefront of the ventilator’s design. In fact, the safe alarm feature operates via redundant monitoring of the COM through the processor and the carrier via the programmable logic.
Because the ventilators need to be more sophisticated and easier to use to combat errors while maintaining transportability, the described COM concept that reliably controls the devices offers the complete functionality of a standard computer in a much smaller space.
Big benefits from compact computing
Because they incorporate a complete computing system on a single board, these modules bring more processing power into a smaller space. The flexibility of using a carrier card to adapt to specific applications, coupled with the ruggedization and standardized form factor, further enhance the use of this embedded computing concept in advanced medical electronics. Intelligent ventilation can utilize this technology to help deliver superior performance in complex environments while reducing costs and saving lives.
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