Quantifying Risk in Various Methods of Continuous Monitoring
- Friday, 01 July 2011
Medical device companies should weigh the advantages and disadvantages of different approaches to monitoring critical environments.
Worldwide, there is growing concern about how to protect public safety and increase cooperation among regulatory agencies to audit medical device companies and their suppliers. Regulatory agencies are increasingly looking to global organizations such as the Global Health Task Force (GHTF) to adopt harmonization in regulatory practices. As recent as August 2010, the GHTF made medical device suppliers inclusive of site auditing guidelines. (“A supplier delivering materials, components, or services, that may influence the safety and performance of the product.” GHTF/SG4/N33)
All methods for monitoring critical environments such as refrigerators, freezers, clean rooms, packaging areas, and warehouses for medical devices and products need to be scrutinized for systemic weaknesses that allow human error to compromise product quality, system failure probabilities, and overall costs of ownership. When it comes to regulatory compliant applications involving public health, however, the criteria for using one method over the other should be well understood. The following chart (Fig. 1) provides a comparative overview of risk factors among different continuous monitoring modalities.
Paper-Based Chart Recorders: Over the last decade, leading medical device companies and their suppliers have been replacing paper chart recorders due to the risks of handling paper-based records and limited or no alarm notification. Chart recorders rely on humans for daily or weekly checks to replace paper, check pens, and write deviation reports. In addition, regulatory agencies encourage the move away from manually inten-
sive processes to more automation with the purpose of tightening up quality systems and making better use of quality resources.
Standalone Data Loggers: Compared to paper chart recorders, standalone data loggers reduce, but still do not completely eliminate the potential for human error. Staff may neglect to download data before the storage capacity of the instrument is exceeded. Battery-powered data loggers require ongoing monitoring of batteries. Even when battery alerts are in place, someone has to be there to see it. AC-powered data loggers without batteries may not record in the event of power outages.
As with chart recorders, the capability to access accurate and complete records throughout the record retention period as required by FDA 21 CFR Part 11 and EU GMP Annex 11 may be compromised if it takes too long to locate records or they are incomplete.
Wired Networks – With and Without PoE Capabilities: The industry has long relied on a wired infrastructure using Ethernet standards for making the connection to transmit and receive data. A hard-wired network allows communications to proceed securely and continuously with few possibilities to intercept or interrupt the flow of data.
Uninterruptible Power Supplies (UPS) ensure that servers are always available for data exchange. However, a potential problem with data continuity of monitoring controlled environments arises with a power outage to the facility. The UPS maintains network uptime but devices connected to the network may be without power, which could mean loss of critical data. Until recently, traditional wired networks lacked a cost-effective alternative to maintain data flow with these critical devices.
Power over Ethernet (PoE) technology allows electrical power and data to travel on the same Ethernet cable. Since 2003, companies have been integrating data and power standards on the manufacturing floor with PoE (IEEE 802.af) capable devices. The advantages of deploying a PoE network are many: (1) Saves the cost of running additional AC power, which usually requires a licensed electrician, aided by the low cost of network switches with built-in PoE power capability; (2) Provides greater flexibility to locate devices around the plant because they can be installed wherever a LAN cable can be run; (3) Increases data communication protection from power outage because the server’s UPS provides backup to PoE connected devices; (4) Protects critical data through the outage period. With PoE, security, maintenance, and access can all be managed within an existing IT framework.
Wireless Networks – WiFi and Mesh: For many medical device plants and warehouses, especially those in older facilities where there are difficulties in running Ethernet cabling, wireless communications can be a convenient and cost-effective method of connectivity. Ease of installation, reduction in cabling cost, and measurements in inaccessible areas are among the major factors driving the adoption of wireless networking.
WiFi is often the wireless system of choice because it uses the same IT infrastructure already in place in an organization. Wireless mesh (Zigbee) is a network architecture that uses access points or nodes to communicate with one another as well as with the host. It is designed to detect a degraded signal at one access point and reroute it to another nearby access point. Nodes have a low power requirement, which has the expectation of less drain on battery life. At the same time, low power inherently means less signal strength than WiFi. The low power requirement of Zigbee networks also means that there needs to be a sufficient number of nodes to maintain continuous data flow.
A downside of wireless is the possibility for losing the signal from obstacles that block transmission. This can be overcome using a sufficient number of wireless access devices.
The range for a wireless device is largely dependent on radio strength, which is also tied to the battery power. These installations have to accommodate signal range and barriers, which become important factors when continuous data is required.
With wireless mesh networks, signals are diverted to maintain data flow but this increases the load on other nodes picking up the signal, having implications for reduced battery life in unpredictable ways. These systems need a vigilant source for detecting and alerting for low battery issues well before data is lost.
With wireless systems, signals carrying critical data can also degrade from interfering sources such as security cameras, microwave ovens and Bluetooth devices communicating in the same 2.4 GHz band (WiFi & Zigbee).
Conclusion: Quantify Risk
No matter which connectivity method is used in temperature and humidity measurement devices, it is important to understand the limitations of each methodology. For the most part, the multiple ways in which standalone monitoring devices insert human error potential make them less than desirable compared to more automated network-based monitoring technology.
Wireless communication has the advantage of being flexible to install when there is limited access to running cable or where monitored storage units are moved on a frequent basis. Wired networks have the advantage of speed, security, and data redundancy. Generally speaking, if the goal is to reduce the risk of data loss to zero or nearly so, then wired systems are the best course. The lower upfront cost of wireless can disappear quickly if you have to write deviation reports from missing data, or experience product loss or regulatory problems. The good news is that connectivity technologies can be mixed — wired and wireless, solving the physical installation challenges that many facilities pose.
The details of how humans interact with systems — whether driving lift trucks, replacing batteries, or downloading data, etc. — are important factors in determining if a particular continuous monitoring technology truly minimizes risks introduced by the inevitability of human error.
This technology was done by Vaisala, Helsinki, Finland. For more information, visit http://info.hotims.com/34456-195.