Electrocardiography (ECG) is the non-invasive

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Ahmet Turkmen, Carl Pantiskas Electrocardiography (ECG) is the non-invasive capture and display (either on a screen or as a hard copy, such as a strip recording or page printout) of cardiac

ECG is used for monitoring cardiac activity, for the purpose of diagnosis and therapy in clinics, and all areas of the hospital, including operating rooms and intensive care units (ICU).

1 Ahmet Turkmen, Carl Pantiskas Electrocardiography (ECG) is the non-invasive capture and display (either on a screen or as a hard copy, such as a strip recording or page printout) of cardiac electrical activity. ECG provides a quick and highly reliable estimate of a patient s cardiovascular health, making it one of the most common non-invasive medical applications. ECG is used for monitoring cardiac activity, for the purpose of diagnosis and therapy in clinics, and all areas of the hospital, including operating rooms and intensive care units (ICU). Physicians can use ECG to quickly measure heart rate and cardiac rhythm of a patient. The physician can also identify abnormalities in how electrical impulses propagate through the heart and detect evidence of coronary artery disease, prior heart attacks, and thickening of the cardiac muscle. 1 4 For more detailed information about a patient s cardiac electrical activity, a physician may request longer-term ECG recordings through the use of a Holter monitor (an ambulatory ECG) or during intentionally loading of the heart with a stress test, such as having the patient exercise on a treadmill. Continuous ECG monitoring during anesthesia provides vital information regarding a patient s condition throughout a surgical procedure. Continuous ECG data acquisition using a bedside monitor provides real-time health information for a patient in an ICU. In some instances, pacemakers or defibrillators (external and internal) significantly alter Ahmet Turkmen, PhD, MS, BS, is an assistant professor with the Engineering and Technology Department at the University of Wisconsin Stout. He is a co-chair of the AAMI ECG Committee. turkmena@ uwstout.edu Carl Pantiskas, MS, BSEE, BS, is senior staff clinical engineer with Draeger s Patient Monitoring Group. He is co-chair of the AAMI ECG Committee. Carl. Pantiskas@draeger.com the appearance of the body-surface ECG. Many medical activities, including life supporting or life saving ones, depend on efficient acquisition of ECG data. ECG has been used since Willem Einthoven invented the first practical ECG in 1903, receiving the Nobel Prize in Medicine in 1924 for his invention. 5 ECG systems have evolved over many years. Now, ECG systems are built with similar building blocks, and all have similar external components. Electrical or mechanical failures occur infrequently for ECG devices themselves; however, malfunctions due to problems with ECG electrodes, leadwires, and ECG (patient) cables are common. 6 This article reviews these problems and presents the results from a 2010 AAMI survey of biomedical equipment technicians (BMET)s and clinical engineers (CE)s. The article covers issues related to clinical management of the cables and leadwires, as well as potential improvements in the design of new medical devices to increase efficiency and reliability. ECG cables, leadwires, and electrodes are used to connect the human body to many different types of ECG devices. Hospitals usually have many medical devices that record and display ECG signals including Holter monitors, stress-testing equipment such as treadmills, patient monitors, telemetry units, defibrillators, and diagnostic electrocardiographs (often referred to as ECG or EKG carts). Large multi-specialty clinics may have treadmills and Holters, but these are generally run through a cardiology subspecialty group. (Smaller clinics and physicians offices also use some of these devices, but patient monitors and telemetry units are typically not on site.) These facilities stock large numbers of ECG cables, leadwires, and electrodes needed to use these devices. Poor electrodes and worn-out leadwires or ECG cables routinely cause failures that clinical users may not be able to readily identify. ECG cables and leadwires should be tested by a BMET regularly or whenever an ECG device seems to be malfunctioning and replaced when necessary. Leadwires should only be used if they remain in good condition (i.e., intact insulation, unbroken, no visible signs of wear). If a BMET is not available, clini- 130 March/April 2011

2 Turkmen et al cal users should be able to visually check the cables and leadwires, and recognize that noisy ECG signals and no recording conditions usually occur when broken or poor-quality cables and leadwires are used. Clinical users should be able to replace these suspected defective cables and leadwires with good ones, and send the replaced cables and leadwires for service. Survey of BMETs In 2010, AAMI, on behalf of the authors, asked BMETs about their experiences with ECG cables, leadwires, and electrodes. A random sample of 300 BMETs was e- mailed a seven-question survey about ECG cables. From this group, 67 BMETs representing a cross-section of different hospitals responded. Survey participants were asked to describe the type of the facility, the total number of hospital beds, how many devices with ECG cables participants were used at their facility, and the names of those devices. The survey participants were also asked to cite the most common ECG cable and wire problems they encountered, their frequency, other experiences they would like to share, and what simple things nurses could do to troubleshoot issues. The most common problems reported, as seen in Table 1, were bad electrode placement, poor connectivity between electrodes and patients, broken leadwires, and dry or old electrodes. These problems can be avoided if the devices are used carefully. Clinical users of ECG devices are expected to know how to prepare the patient s skin and place the electrodes to obtain good electrical conduction. They should be able to determine whether the electrodes are too old or too dry or are still in good condition. 1. Bad electrode placement 2. Dried up electrodes 3. Improper skin prep 4. Broken leadwires or clips 5. Broken connector pins 6. Interference with ESU units 7. Worn leadwires 8. Missing leadwires 9. Frayed cords 10. Abuse by patient and staff Table 1. AAMI Survey Results on Problems With ECG Cables, Leadwires, and Electrodes Other reported problems were broken leadwires, broken clips, broken connectors, and broken pins in the ECG cable s connector to the device, A few responders mentioned noise problems, low signal/noise ratio, weak strain-relief of these parts, intermittent or lost connections during exercise, worn leadwires that have intermittent loss of continuity or high impedance problems, and leadwires breaking at the termination point. A less common problem was the tightness of the connection of the leadwire to the electrode. Fixing this group of problems is usually a job for a biomed. For most of these problems, the best solution is to replace the faulty ECG cable or leadwire with a new one. A well-trained clinical user can easily detect most of the aforementioned problems. Active involvement of clinical users in management of medical equipment can increase the department s efficiency and help it provide uninterrupted service. Potentially faulty material can still be tested and, if possible, fixed or replaced by a biomed. When the ECG cables and leadwires are tested, a biomed may check their impedance with an ohmmeter. An intact lead or cable wire will read a low impedance or resistance value. A continuity tester with audio feedback is probably a better tool than an ohmmeter. Another test that can be performed is to connect the leadwires to a patient simulator and observe signals on the screen. Biomeds can also flex all the ends where the wire meets the connector through various angles to look for an intermittent break. Either testing may provide insight into conductivity and hence the quality of the ECG cable and the leadwires. However, this may not be enough to eliminate problems if the electrodes used with them are too dry. Of the 67 responses received, 24 (36%) stated that these problems occur every day or several times a week; 10 (15%) stated they occur occasionally. This difference probably relates to how frequently a hospital replaces patient cables and leadwires. There may also be many other variables, such as how often nurses will report the problem as opposed to replacing the cables themselves. Cables and leadwires that are used for a long time are more likely to have these problems. Several responders wrote that patient cables and leadwires usually have problems after about 12 months of usage. In practice, leadwires may need to be replaced after anywhere from six to 24 months of use. This variability may seem suspicious, but several factors affect this. The first is how often a particular ECG device is used (a cardiac monitor may be used nearly 100% Biomedical Instrumentation & Technology 131

3 of the time if it is in an ICU, but only for one to two hours per day if it is in an operating room. A 12-lead electrocardiograph in a physician s office may be used one to two hours a week or month. A second factor relates to how much abuse ECG cables and leadwires are subjected to. Consider, for example, transporting a patient who is being monitored to another area within a hospital. As the patient is moved along hallways, up and down elevators, the connected ECG cables and leadwires may be caught in bed rails or crushed by wheels. A third factor is whether ECG cables and leadwires stay with the patient after they are moved or are returned to their original location. Since tagging ECG cables or leadwires may not be feasible, feedback from clinical users may be the only way to locate faulty patient cables and leadwires. This must be done if the ECG devices are to be used efficiently and to keep them reliable. Tagging ECG leadwires and cables is an additional equipment management workload for the hospital. Unless there s evidence the time invested truly addresses these problems, it may not be worth the expense. Reducing Problems in a Clinical Setting In many hospitals, a BMET or CE maintains and troubleshoots ECG devices, including their cables and leadwires. These devices are routinely used by a wide range of clinicians, from physicians and nurses to the care specialists, such as cardiology technicians and medical assistants. Clinical users usually try to address a noisy signal, generally by repositioning the leads and assuring good contact. This kind of troubleshooting may not be as thorough as that of a biomed, but a clinician s primary focus has to be How to Increase Reliability The following is a list of things that can be done in a clinical setting to reduce problems with ECG cables and leadwires. The list was developed based on responses received from the survey. Train the clinical users. Devices that are used by trained personnel who care for them properly last much longer. Clinical users who use ECG devices should be well trained in how to prepare the patient for monitoring and recording, in positioning electrodes correctly, in making all cable connections, and in using the devices. These problems occur less frequently if clinical users are more familiar with how to do this. Actively involve clinical users to provide uninterrupted service. Having clinical users perform simple visual checks on cables, leadwires, and electrodes really makes a difference. Clinical users should be able to determine if electrodes are usable before putting them on a patient s skin. They should look for missing or broken leadwires, bad clips, or leadwires/cables with cut insulation. They should replace bad cables or bad leadwires with good ones. They should also check to see if the device displays any messages about missing leadwire/electrode connections, noise in displayed signals, null signals, or connection problems. Use good quality equipment. The problems listed above will occur less frequently if the electrodes, leadwires, and cables being used are of good quality. This also reduces service interruptions and the need for frequent troubleshooting. Check the electrodes regularly and use only good ones. Good electrical conduction from skin to a leadwire is critical. The electrode should be usable and not too dry. Many hospitals simply dump bags of electrodes into a convenient drawer whenever the level of the electrodes in that drawer is low. In such cases, simply rotating stock to ensure that older electrodes are used first greatly improves ECG device availability and the perceived quality of service. Identify and replace bad cables and leadwires. The cables and leadwires should be of good quality and intact. Faulty leadwires should be identified and eliminated quickly and good leadwires should be used as long as possible. Having a BMET frequently check the ECG cable and leadwires help problems occur less frequently. Always have spare cables and leadwires for clinical users. Always have spare ECG cables and leadwires available so that clinical users can quickly replace a faulty ECG cable or faulty leadwire when needed. 132 March/April 2011

4 Turkmen et al on patient safety, not medical device repair. However, keeping ECG devices working properly all the time benefits everyone. Poor management of the available technology results in inefficient use of these medical devices, loss of time and resources, and, most importantly, loss of their availability to support patient care. Think about how frustrating it is if a monitor fails to provide vital information at a crucial time, especially when the root cause turns out to be an easily recognized broken ECG cable or leadwire. Education of the clinical user, collaboration between clinical users and biomeds, use of good quality equipment, good maintenance, and availability of spare ECG cables and leadwires can all contribute to change for the better. Improving the Technology The survey responses also provided some clues on how new devices can be designed better. Here are some ideas: Standardization in connectors. Some survey respondents complained that there are too many different kinds of connectors in the market. Connectors are also expensive and are rarely compatible. Even those that look identical may have different pin assignments. Using standard connectors in all ECG devices can reduce maintenance and repair costs. Use of standard connectors will enable use of the same patient cables with different devices. This will reduce operating costs and make life easier for clinical users and biomeds. (This particular aspect of the survey is potentially confusing. ECGC:1983 defined a standardized connector for the trunk cable, but few manufacturers chose to support it. EC53:1995 was, therefore, written to standardize the connection at the leadwire, rather than at the trunk cable.) Improve strain-relief and make cable-leadwire systems more durable. Wires are less likely to break if they incorporate better strain-relief and are made of durable materials. The resulting system is then reliable even under demanding conditions. In addition, it s important that clinical users are careful in their use. Auto test. Designing a cable diagnostic tool into ECG monitors can save a lot of time and effort for BMETs and CEs, as well as for clinical users by allowing them to identify and replace bad parts. Develop new sensors which are less prone to noise or bad skin contact. Some researchers are working on development of capacitive sensors which may replace the ECG electrodes in current use. 7 Good contact with the patient s skin is not a problem with these new sensors. The measurements can even be taken through clothing. No ground contact is required to measure a multichannel ECG. A tablet personal computer (PC) with such sensors can provide a new, fast diagnostic tool through the real-time view of the electrocardiogram without any preparation procedure. These suggestions can lead to more reliable ECG devices and their more efficient use. This paper presented many practical problems related to these external components. This study is based primarily on feedback from biomeds who are deeply involved in maintenance and repair of ECG devices. It proposes some solutions to eliminate or reduce the problems and to design better ECG devices. It should be beneficial for clinical users, BMETs and CEs, and designers of ECG devices. The authors appreciate the contributions of everyone who responded to the survey. References 1. Chatterjee S, Miller A. Biomedical Instrumentation Systems. Delmar Cengage Learning 2010: Webster JG. Medical Instrumentation. 4th ed. John Wiley and Sons; 2010: Christe BL. Introduction to Biomedical Instrumentation: The Technology of Patient Care. Cambridge University Press; 2009: Thibodeau GA, Kevin TP. The Human Body in Health and Disease. 4th ed. Elsevier Mosby; 2002: Brodsky I. The History and Future of Medical Technology. First Edition. Telescope Books; 2010: Carr JJ, Brown JM. Introduction to Biomedical Equipment Technology. 4th ed. Prentice Hall; 2001: Oehler M, Ling V, Melhorn K, Schilling M. A multichannel portable ECG system with capacitive sensors. Physiol. Meas. 2008;29; A Helpful Standard AAMI EC53:1995/(R)2008 & A1:1998/(R)2008, ECG cables and leadwires and amendment List Price: $80 Member Price: $40 Order Code: EC53 or EC53-PDF To order, call (877) or visit the Marketplace at Biomedical Instrumentation & Technology 133

CP lead resting electrocardiograph

CP lead resting electrocardiograph CP 150 12-lead resting electrocardiograph Quick reference guide 2013 Welch Allyn, Inc. To support the intended use of the product described in this publication, the purchaser of the product is permitted