Electromagnetic compatibility - sensibility of implantable

Transcription

1 Sveučilište u Zagrebu Fakultet elektrotehnike i računarstva Biomedicinska instrumentacija Electromagnetic compatibility - sensibility of implantable electronic devices to different kinds of electroterapy Ratko Magjarević University of Zagreb Faculty of Electrical Engineering and Computing Croatia ratko.magjarevic@fer.hr

2 Electromagnetic compatibility (EMC) the degree to which an electronic system is able to function compatibly with other electronic systems not susceptible to interference not produce interference Opposite: Electromagnetic interference (EMI) EMC - Implantable Devices 2

3 Electromagnetic interference (EMI) disturbance that t affects an electrical l circuit it due to electromagnetic ti radiation electromagnetic conduction (bellow ~50 MHz) electrostatic discharge emitted from a source external internal may interrupt, degrade or obstruct the performance of an electronic circuit EMC - Implantable Devices 3

4 Electromagnetic interference (EMI) Inductive coupling Inductive coupling occurs where the source and receiver are separated by a short distance (typically less than a wavelength). Strictly, "Inductive coupling" can be of two kinds, electrical induction and magnetic induction. It is common to refer to electrical induction as capacitive coupling, and to magnetic induction as inductive coupling. Capacitive coupling Capacitive coupling occurs when a varying electrical field exists between two adjacent conductors typically y less than a wavelength apart, inducing a change in voltage across the gap. EMC - Implantable Devices 4

5 Electromagnetic interference (EMI) Conductive coupling Conductive coupling occurs when the coupling path between the source and the receptor is formed by direct contact with a conducting body, for example a transmission line, wire, cable, PCB trace or metal enclosure. Conduction modes Conducted noise is also characterised by the way it appears on different conductors: Common-mode or common-impedance[1]) coupling: noise appears in phase (in the same direction) on two conductors. Differential-mode coupling: noise appears out of phase (in opposite directions) on two conductors. EMC - Implantable Devices 5

6 Electromagnetic interference (EMI) Magnetic coupling Inductive coupling or magnetic coupling (MC) occurs when a varying magnetic field exists between two parallel conductors typically less than a wavelength apart, inducing a change in voltage along the receiving conductor. Radiative coupling Radiative coupling or electromagnetic coupling occurs when source and victim are separated by a large distance, typically more than a wavelength. Source and victim act as radio antennas: the source emits or radiates an electromagnetic wave which propagates across the open space in between and is picked up or received by the victim. EMC - Implantable Devices 6

7 EMI Growth The power density of EMI in an average urban environment since Light pollution is 1 to 1 correlated with electromagnetic energy leaking into the environment. Where there is artificial light there is electromagnetic interferences. from: EMC - Implantable Devices 7

8 Pacemakers and EMI pacemaker life saving device + EMI - may interrupt, degrade or obstruct the performance of an electronic circuit it = EMI may be life-threatening for patients with pacemakers Ruggera P.S. and R. Elder, Electromagnetic Radiation Interference with Cardiac Pacemakers, DHEW publication BRH DEP 71-5, 1971 EMC - Implantable Devices 8

9 EMI to (other) Medical Devices Documented cases: a ventilator suddenly changes its breath rate an electric powered wheelchair suddenly veers off course an apnea monitor fails to alarm... Casamento JP, Ruggera PS.Applying standardized electromagnetic compatibility testing methods for evaluating radiofrequency interference with ventilators, Biomed Instrum Technol. Witters D.M. and P. S. Ruggera, EMC of Powered Wheelchairs and Scooters, Proc. RESNA '94 EMC - Implantable Devices 9

10 Solving EMI at System Level EMI involves: the device itself the environment in which it is used anything that may come into that environment EMI - a systems problem requiring a systems approach EMI solution requires involvement of the (medical) device industry, the EM source industry (power industry, telecommunications industry...), the clinical user and patient EMC - Implantable Devices 10

11 IEC Classification International ti Electrotechnical Commission (IEC) classification of EM environment Conditions for the location and power of local l EM energy sources (e.g., transmitters) Table 1 indicates the general classifications and the upper range of radiated EM field strength specified for each environment. EMC - Implantable Devices 11

12 Sources of EMI Radio broadcasting Television Public safety (police, fire, highway, forestry, and emergency services) Land transportation (taxis, trucks, buses, railroads) Amateur radio Cellular phones and paging systems Industrial, scientific, and medical Citizens' band (CB) radio Radar... EMC - Implantable Devices 12

13 Factors affecting EMC Frequency, Wavelength, and Antenna Effect Depth of Implantation Modulation Examples of Recorded d Device Malfunction Due to EMI Electroencephalographic cep og ap c interference e e Impedance-based apnea monitor mishaps Monitor alarms Mechanism of death due to apnea Susceptibility to EMI Drug-infusion pump mishaps Ventilator mishaps Powered-vehicle mishaps EMC - Implantable Devices 13

14 Examples of Recorded Device Malfunction Due to EMI Cellular and Mobile Telephone-Generated EMI Infant radiant warmer mishaps Miscellaneous medical device mishaps Health effects Blood pressure monitor EMC - Implantable Devices 14

15 Cardiac Pacemakers and EMI Implanted pacemakers Pacemaker malfunction due to cellular Communication with an implanted phones pacemaker Pacemaker malfunction due to magnetic Failure modes resonance imagers Effect of EMI on pacemaker function Pacemaker malfunction due to Pacemaker malfunction due to microwave-oven EMI electrosurgery Pacemaker malfunction due to low- Abandoned pacemaker lead frequency EMI accident Electronic surveillance systems Pacemaker malfunction due to paging system EMC - Implantable Devices 15

16 Implanted cardioverter defibrillator (ICD) Effect of EMI on ICDs ICD malfunction due to arc welders Cell-phone EMI Slot machine EMI Pacemaker and ICD interaction Improper electrode placement Powerline ICD accident EMC - Implantable Devices 16

17 Electrostatic Discharge Introduction ESD testing Mechanism of action of ESD ESD incidents Effect of ESD on human subjects EMC - Implantable Devices 17

18 Model of Interference EMC - Implantable Devices 18 from: S. Hrabar, Analysis of EMI between mobile telephone and impllanted medical device, Ph.D. thesis, 1999

19 Definitions to EMC problems Imunity to disturbance ability of a device to perform without degradation in presence of EMI Compatibility level l specified EM disturbance level expected to be impressed to a device Imunity level l max level l of given EM disturbance incident on a particular device Imunity margin difference between the imunity it level and EM compatibility level from IEEE standards EMC - Implantable Devices 19

20 Immunity Limit EMC - Implantable Devices 20 from: S. Hrabar, Analysis of EMI between mobile telephone and impllanted medical device, Ph.D. thesis, 1999

21 Block diagram of an unipolar pacemaker EMC - Implantable Devices 21

22 Unipolar Sensing Produces a large potential difference due to: A cathode and anode that are farther apart than in a bipolar system What about EMI? _ EMC - Implantable Devices 22

23 Block diagram of a bipolar pacemaker EMC - Implantable Devices 23

24 Bipolar Sensing Produces a smaller potential difference due to the short interelectrode distance: Electrical signals from outside the heart such as myopotentials are less likely to be sensed EMC - Implantable Devices 24

25 Amplifier Circuits - DC coupled EMC - Implantable Devices 25

26 Amplifier Circuits - AC coupled EMC - Implantable Devices 26

27 Biopotential Isolation Amplifier EMC - Implantable Devices 27

28 EMC - Implantable Devices 28

29 EMC - Implantable Devices 29

30 EMC - Implantable Devices 30

31 EMC - Implantable Devices 31

32 Electromagnetic Interference EMC - Implantable Devices 32

33 Electromagnetic Interference (EMI) Interference is caused by electromagnetic energy with a source that is outside the body Electromagnetic fields that may affect pacemakers are radio-frequency waves Hz are most frequently associated with pacemaker interference Few sources of EMI are found in the home or office but several exist in hospitals EMC - Implantable Devices 33

34 EMC - Implantable Devices 34

35 EMC - Implantable Devices 35

36 EMI May Result in the Following Problems: Oversensing Transient mode change (noise reversion) Reprogramming (Power on Reset or POR ) EMC - Implantable Devices 36

37 Oversensing May Occur When EMI Signals Are Incorrectly Interpreted as P Waves or R Waves Pacing rates will vary as a result of EMI: Rates will accelerate if sensed as P waves in dual-chamber systems (P waves are tracked ) Rates will be low or inhibited if sensed in single-chamber systems, or on ventricular lead in dual-chamber systems EMC - Implantable Devices 37

38 EMI Noise sensed by the pacemaker Should have paced EMC - Implantable Devices 38

39 Noise Reversion Continuous refractory sensing will cause pacing at the lower or sensor driven rate Lower Rate Interval Noise Sensed VP SR SR SR SR VP EMC - Implantable Devices 39

40 EMI May Lead to Inadvertent Reprogramming of the Pacing Parameters Device will revert to Power on Reset (POR or backup mode) Power on Reset may exhibit a mode and rate change which are often the same as ERI In some cases, reprogrammed parameters may be permanent EMC - Implantable Devices 40

41 New technologies will continue to create new, unanticipated sources of EMI: Cellular phones (digital) EMC - Implantable Devices 41

42 Sources of EMI Are Found Most Commonly in Hospital Environments Sources of EMI that interfere with pacemaker operation include surgical/therapeutic equipment such as: Electrocautery Transthoracic defibrillation Extracorporeal shock-wave lithotripsy Therapeutic radiation RF ablation TENS units MRI EMC - Implantable Devices 42

43 Sources of EMI Are Found More Rarely in: Home, office, and shopping environments Industrial environments with very high electrical outputs Transportation T t ti systems with high h electrical l energy exposure or with high-powered radar and radio transmission Engines or subway braking systems Airport radar Airplane engines TV and radio transmission sites EMC - Implantable Devices 43

44 Electrocautery is the Most Common Hospital Source of Pacemaker EMI Outcomes Precautions Oversensing inhibition Reprogram mode to Undersensing g( (noise VOO/DOO, reversion) or place a magnet over Power on Reset device Permanent loss of Strategically place the pacemaker grounding plate output (if battery voltage is Limit electrocautery bursts low) to 1-second burst every 10 seconds Use bipolar electrocautery forceps EMC - Implantable Devices 44

45 Transthoracic Defibrillation Outcome Inappropriate reprogramming of the pulse generator (POR) Damage to pacemaker circuitry Precautions Position defibrillation paddles apex-posterior (AP) and as far from the pacemaker and leads as possible EMC - Implantable Devices 45

46 Magnetic Resonance Imaging (MRI) is Generally Contraindicated in Patients with Pacemakers Outcomes Precautions Extremely high pacing rate Reversion to asynchronous pacing Program pacemaker output low enough to create persistent non-capture, ODO or OVO mode EMC - Implantable Devices 46

47 Lithotripsy Shock Waves May Have an Effect on Pacemaker Systems Outcomes in Precautions: dual-chamber modes: Program pacemaker to VVI Inhibition of ventricular or VOO mode pacing Lithotriptor focal point should be greater than 6 inches from the pacemaker Outcomes in rate adaptive pacemakers High pacing rates Piezoelectric crystal damage Carefully monitor heart function throughout procedure EMC - Implantable Devices 47

48 Radiation Energy May Cause Permanent Damage Certain kinds of radiation energy may cause damage to the semiconductor circuitry Ionizing radiation used for breast or lung cancer therapy Damage can be permanent and requires replacement of the pacemaker EMC - Implantable Devices 48

49 Therapeutic Radiation May Cause Severe Damage Outcomes: Pacemaker circuit damage Loss of output Runaway Precautions: Keep cumulative radiation absorbed by the pacemaker to less than 500 rads; shielding may be required Check pacemaker after radiation sessions for changes in pacemaker function (can be done transtelephonically) EMC - Implantable Devices 49

50 Pacemaker Features That Address Interference Pacemaker sensing circuits amplify, filter and either process or reject incoming signals Input Bandpass filter Absolute value Reversion circuit Level detector Pacemaker logic Sensitivity adjustment EMC - Implantable Devices 50

51 Equipment interference with pacemakers At home Household devices: shavers, hairdryers and microwave ovens, household tools such as drills,mowers and electric screwdrivers - not be a problem, as long as they are well maintained. Phones Useing a mobile phone or a cordless phone is safe, but it is best to keep the phone more than 15 centimetres (6 inches) from your pacemaker. Always use the ear on the opposite side to your pacemaker, and do not put the phone in a pocket over your pacemaker. Travelling and security systems Airport screening systems and anti-theft systems in shops and libraries may, very rarely, cause problems with pacemakers. There is also a small chance that you may trigger the alarms. Always carry your pacemaker registration card with you. In some countries you may be asked to go through the security system. Move quickly through the gateway. EMC - Implantable Devices 51

52 Equipment interference with pacemakers At work Some workplaces have strong electromagnetic fields which can interfere with your pacemaker. Arc-welding is an example. In hospitals Some hospital equipment may interfere with pacemakers. Some types of equipment used in surgery can also cause problems. Magnetic resonance imaging i (MRI) scans can be dangerous for pacemaker patients.. EMC - Implantable Devices 52

53 The SureScan Pacing System The first pacing systems designed, tested and approved for MRI EMC - Implantable Devices 53

54 The SureScan Pacing System Patients and physicians need a device specifically designed to address the unique hazards of magnetic resonance imaging. Professor Richard Sutton St. Mary s Hospital, London EMC - Implantable Devices 54

55 Pacing Systems need to be MRI-safe by Design not Chance Control about Reed switch behavior Better protection against electromagnetic interference leading to electrical reset Programmable MRI modes for different pts. populations Leads with less RF-induction and less temperature increase EMC - Implantable Devices 55

56 SureScan Innovations Change: Lead input filtering capacitance Benefit: Minimize the energy induced on leads/discharged at tip Change: Reed switch replaced by Hall sensor Benefit: Control switch behavior Change: Internal power supply circuit protection Benefit: Prevents the energy induced on the telemetry antenna from disrupting the internal power supplies Change: Significantly reduced ferromagnetic components Benefit: Decrease susceptibility to magnetic attraction Reed Switch Hall sensor EMC - Implantable Devices 56

57 SureScan Innovations Change: Dedicated SureScan modes: asynchronous pacing or non pacing mode (Programmer+ Device Software/Firmware) Benefit: Ease of patient management Suspension of diagnostic data collection and atrial arrhythmia therapy EMC - Implantable Devices 57

58 SureScan Innovations Change: 5086 lead geometry and internal make up (filar #, pitch, size, Impedance, ) changed to prevent interactions with gradient field and produce low RF conduction characteristics Benefit: Reduces lead heating Standard MRI Pitch EMC - Implantable Devices 58

59 SureScan Innovations Change: Radiographic markers Benefit: Ease of device identification EMC - Implantable Devices 59

60 The SureScan Pacing System MRI-safe by Design not tchance 1997 Initiate Research 2001 Begin technology work with international eperts experts 2004 Commence formal discussions with regulatory bodies (TUV, FDA, ) 2005 Complete first system modifications: start extensive test program 2006 Finalize device modifications; define human clinical trial 2007 Commence worldwide EnRhythm MRI Pacing System clinical trial 2008 Clinical trial completed; CE mark received; EnRhythm MRI market release nd generation SureScan Pacing Systems market release MRI Unsafe MRI Conditional: Safe for use in MRI under certain conditions EMC - Implantable Devices 60

61 Approval by the authorities t SureScan was rigorously tested, clinically studied, and CE-mark approved The CE marking (also known as CE mark) is a mandatory conformance mark on many products placed on the single market in the European Economic Area (EEA). The CE marking certifies that a product has met EU consumer safety, health or environmental requirements. EMC - Implantable Devices 61

62 Literature Yadin, D et al, eds. Clinical Engineering CRC Press, 2003 Kimmel D.D., D.D. Gerke, Protecting Medical Devices From Electromagnetic Interference, Designer's Handbook: Medical Electronics, Brown,B.H. et alt., Medical Physics and Biomedical Engineering., g IoP Publishing, London, reprinted Webster,J.G. (Ed.), Medical Instrumentation, Application and Design. 2nd ed., J. Wiley & Sons, Inc., New York, Webster,J.G. (Ed.), Bioinstrumentation. John Wiley & Sons, Inc., New York, 2003 In Croatian: Šantić, A., Biomedicinska elektronika, Školska knjiga, Zagreb, 1995 EMC - Implantable Devices 62

63 Standards, Regulations... EU directive 2004/108/CE (previously 89/336/EEC) on EMC CISPR 11 - Industrial, scientific and medical (ISM) radio-frequency equipment - Electromagnetic disturbance characteristics - Limits and methods of measurement ANSI/AAMI PC69:2000, Active implantable medical devices- Electromagnetic compatibility- EMC test protocols for implantable cardiac pacemakers and implantable cardioverter defibrillators, American National Standards Institute, Medical Electrical Equipment, Part 1: General Requirements for Safety, Collateral Standard: Electromagnetic Compatibility, International Electrotechnical t l Commission i IEC IEC Electromagnetic Compatibility (EMC)- Part 4; Testing and measurement techniques- Section 3: Radiated, Radio frequency, electromagnetic field immunity test The Safe Medical Devices Act (SMDA) of 1990, Public Law International Electrotechnical Committee IEC/TC or SC: TC77, Electromagnetic Compatibility Between Electrical Equipment Including Networks, Classification of Electromagnetic Environments... EMC - Implantable Devices 63