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Application of the cardiotrak™ pacemaker monitor to prehospital care
ORIGINAL CONTRIBUTION
Application of the Cardiotrak Pacemaker Monitor to Prehospital Care TM
Roger Bandy, MICP David J. Orban, MD* Joel M. Geiderman, MD t Los Angeles, California
The Cardiotrak TM is a small, lightweight device originally developed for use by pacemaker patients to transmit their electrocardiograms (ECGs) by telephone to their doctor or to a hospital. The Cardiotrak seemed well suited for use by paramedics and was field tested on 76 patients. In 69 patients, clear ECGs were transmitted with ease; in the remaining seven, only minor, correctable problems were noted. The Cardiotrak appears to have advantages over other devices used to transmit ECGs to base station hospitals from paramedics. Bandy R, Orban DJ, Geiderman JM: Application of the Cardiotrak TM pacemaker monitor to prehospital care. Ann Emerg Med 10:579-581, November 1981.
pacemaker monitor, prehospital use INTRODUCTION The Cardiotrak TM* is a small device originally developed for pacemaker patients to enable them to send electrocardiogram (ECG) tracings of their heart rhythms to cardiologists for interpretation 1 -3 / (personal communication, B. Goldreyer, August 1980). The heart rate and pacemaker activity are monitored by the physician, who then may advise the patient to go to the hospital, change the medication, or do nothing. The Cardiotrak sends an ECG of an intrinsically paced heart, and thus seemed well suited for field use by paramedics. The emergency departments of UCLA and Cedars-Sinai Medical Center, in cooperation with the City of Los Angeles Fire Department, conducted a pilot project to confirm or refute our initial impression that the Cardiotrak would be beneficial for routine telemetry use, and that it has significant advantages over other systems in current use. Data collected for 76 runs in 60 days are presented and evaluated.
MATERIALS The Cardiotrak is the same general size as a pocket calculator, and is battery operated, lightweight, and relatively inexpensive (Figure 1). It works by emitting a variable pitch tone, depending on the electrical activity of the heart. The tones are sent by telephone to a base station where telemetry translates them into a readable ECG. The device is simply placed on the patient's anterior chest, and a phone receiver is held close to it. This is more quickly and easily set up than are chest leads; contact paste is not necessary; and the tones can be heard immediately once the Cardiotrak is placed against the chest (Figure 2). *Registered Trademark, C.P.I. by Instromedex, Incorporated, Portland, Oregon. From the Department of Medicine, Division of Emergency Medicine, UCLA Hospital and Clinics;* and the Department of Emergency Medicine, Cedars-Sinai Medical Center,t Los Angeles, California. Address for reprints: Joel M. Geiderman, MD, Department of Emergency Medicine, CedarsSinai Medical Center, 8700 Beverly Boulevard, Los Angeles, California 90048.
10:11 (November) 1981
Ann Emerg Med
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The tone can be t r a n s l a t e d into a t r a c i n g by c o n v e n t i o n a l B i o c o m equipment or o v e r M o t o r o l a l a n d line receivers. The Cardiotrak offers significant advantages o v e r t h e c o n v e n t i o n a l phone patch kit, which is too awkward to carry r o u t i n e l y to the site of an arrest. Moreover, the k i t is more difficult to place, a n d s e t - u p t i m e s tend to be l o n g e r . A n a d d i t i o n a l problem with the phone k i t is t h a t it fits only the s t a n d a r d , conventional phone receiver; it could not be used with Princess TM, Trimline TM, or other specialty phones (Figure 3).
METHODS Records were k e p t for 60 days by both t h e p a r a m e d i c s a n d t h e b a s e s t a t i o n s on a l l r u n s in w h i c h t h e Cardiotrak could be used. Personnel at both sites were asked to record the c l a r i t y of t r a n s m i s s i o n , e s t i m a t e d length of time to set up, and other subjective comments. R h y t h m strips were saved and a t t a c h e d to the evaluation sheets for review. The r e s u l t s were e v a l u a t e d and t a b u l a t e d .
F i g . 1. Cardiotrak pacemaker monitor.
RESULTS A total of 76 C a r d i o t r a k evaluat i o n s h e e t s w e r e r e t u r n e d for t h e period of A u g u s t 7 t h r o u g h October 14, 1980. In 69 p a t i e n t s (91%), clear E C G t r a n s m i s s i o n s w e r e n o t e d by the base s t a t i o n , w i t h no a p p a r e n t problems. On only seven of t h e 76 s t r i p s (9%) were a n y p r o b l e m s reported by the hospitals. Two of these were from one engine c o m p a n y which, on successive runs, noted t h a t the C a r d i o t r a k tracings a p p e a r e d as flat lines, y e t the c l i n i c a l c o n d i t i o n s of t h e p a t i e n t s w e r e g o o d . I t w a s n o t e d on t h e second report t h a t the b a t t e r y of the C a r d i o t r a k was c h a n g e d , a n d t h a t i n c r e a s i n g t h e g a i n on the Biocom equipment solved the problem. Another s e p a r a t e incident was due to low b a t t e r y p o w e r as well. O t h e r c o m m e n t s were t h a t , on two occasions, t h e s t r i p s w e r e d i f f i c u l t to read. In one case, 60-cycle interference overlapped sinus rhythm; nevertheless, it was easy to i n t e r p r e t the presence of n o r m a l sinus r h y t h m with a r a t e of 75 and a n o r m a l QRS complex. A n o t h e r p r o b l e m occurred because a telephone fell off a . d e s k a n d b e c a m e d i s c o n n e c t e d . I n one other case, confusion arose because a patient's relative b e g a n u s i n g an extension telephone d u r i n g a run.
46/580
F i g . 2. Cardiotrak placed on anterior chest, coupled to telephone.
Positive comments were that, with slight repositioning of the Card i o t r a k on t h e chest, the strip could e a s i l y be s e n t w i t h perfect clarity. One squad r e p o r t e d t h a t t h e y were in a remote a r e a and would not have been able to t r a n s m i t over the Biocorn due to t h e i r location. One r u n t e s t e d t h e C a r d i o t r a k with the radio transmitter rather than the land-line. The reception was '~good, b u t only s o m e w h a t clear." PVCs were slightly difficult to interpret but, in comparison, the t r a c i n g sent by the radio alone was not as
Ann Emerg Med
clear as was the C a r d i o t r a k tracing. A t base station m e e t i n g s and at the conclusion of the trial, t h e p a r a medics' comments were only positive, p r a i s i n g the ease and convenience of using C a r d i o t r a k . One p a r a m e d i c s u g g e s t e d t h a t b e c a u s e t h e t o n e is a u d i b l e , t h e sound of the p a t i e n t ' s own h e a r t b e a t may cause apprehension and may cause a change in the v i t a l signs, as occurs w i t h m o n i t o r sounds in t h e critical care unit, the sound of ambulance sirens, or the p e r f o r m a n c e of blood pressure m e a s u r e m e n t .
10:11 (November) 1981
DISCUSSION Our trial has shown the Cardiotrak to be an effective, easy-to-use tool for use in transmitting ECGs from the field to the base station. Its use requires only a nearby telephone of any type. When a telephone is not available, it may be coupled successfully with radio equipment. Cardiotrak offers a number of distinct advantages over other equipment. First, it is small, portable, and lightweight, and thus can be carried easily in a "starter kit" taken to the patient's bedside. Because it is easy to carry, it can be available both when a cardiac problem is suspected and when monitoring becomes necessary unexpectedly. As previously noted, all that is necessary to complete the transmission is a nearby phone of any type. In contrast, previously developed phone patch kits could be used only with standard conventional phones. Set up time for the C a r d i o t r a k is a few seconds, whereas the phone patch kit takes one or two minutes, assuming it has been carried to the scene. Contact is quicker by telephone than by radio, and the problem of transmission break-up that is often encountered with radio use is nonexistent. With current methods, problems with telemetry transmission or interference by another signal in the area results in an ECG which is completely non-translatable. When this happens, the base station is forced to repeat the strip, and a great deal of time may be lost. Use of the telephone has been particularly effective in hillside areas or in s t r u c t u r e s from which clear radio signals cannot be transmitted. Another advantage to the phone is that several calls can be received simultaneously without interfering with each other. Confusion t h a t arises d u r i n g s i m u l t a n e o u s r u n s while Using the radio can actually be dangerous. Using the C a r d i o t r a k when a phone is accessible tends to keep the a i r w a y s clear for other situations for which radio communication is the only method available. Battery failure may occur with either the phone-patch kit or the Cardiotrak. Battery failure can be detected early with the Cardiotrak, because a weak signal will be sent. Spare batteries can be carried and changed quickly if necessary.
10:11 (November) 1981
Fig. 3. Phone patch kit, with accessory equipment, coupled to standard telephone. Leads must be attached to patient (not shown). When defibrillation is necessary, the standard Lifepak ~ (PhysioControl Corporation, Redmond, Washington) paddles may be used exactly as if radio communication were established. The Cardiotrak does not int e r f e r e with " q u i c k - l o o k " paddle placement, defibrillation energy, or the performance of cardiopulmonary resuscitation in situations of cardiac arrest. The Cardiotrak may be useful for monitoring en route if coupled to the radio; however, the only advantage of this is in the event that the p a t i e n t did not have chest leads placed, or if chest leads would not stick to the patient's chest for some reason. Finally, patient anxiety may be minimized with careful explanation of the tone and a demonstration prior to placing the device on the patient's chest. The most experienced paramedics have not found "patient fear" to be a problem. CONCLUSION The Cardiotrak is a small, lightweight, relatively inexpensive device that is well suited for ECG transmission by paramedics. The device must be coupled with a radio transmitter when a land-line telephone is not available. A two-month field test at two
Ann Emerg Med
h o s p i t a l s in Los Angeles demonstrated the efficacy of the device. Most problems t h a t were encountered could be alleviated by keeping the Cardiotrak batteries charged. Advantages of the Cardiotrak over radiotelemetry are that it is easier to set up, t r a n s m i s s i o n is clearer, simultaneous transmissions do not interfere, transmission is private, and it may be used in areas in which physical conditions make radio transmission impossible. Its a d v a n t a g e s over p r e v i o u s phone patch kits are that it is less cumbersome, easier to set up, and may be adapted to any phone. The authors thank Chief John Gerard of the Los Angeles City Fire Department, and John Green, MICP, for their support in this project. We also thank Dana Taliaferro, RN, Linda Verraster, RN, and Baxter Larmon, MICR for their support in collecting data. REFERENCES 1. Furman S: The future utility of transtelephonic pacemaker monitoring. J Electrocardiol 9:199, 1976. 2. Furman S, Parker B, Escher DJW: Pacemaker clinic via telephone. Bull Heart Inst Jap 14:1, 1970. 3. Sakurai Y, Aoki E, Terashimu M: Pacemaker clinic by telephone transmission. Artificial Organs 4:357, 1975.
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Application of the Cardiotrak Pacemaker Monitor to Prehospital Care TM
Roger Bandy, MICP David J. Orban, MD* Joel M. Geiderman, MD t Los Angeles, California
The Cardiotrak TM is a small, lightweight device originally developed for use by pacemaker patients to transmit their electrocardiograms (ECGs) by telephone to their doctor or to a hospital. The Cardiotrak seemed well suited for use by paramedics and was field tested on 76 patients. In 69 patients, clear ECGs were transmitted with ease; in the remaining seven, only minor, correctable problems were noted. The Cardiotrak appears to have advantages over other devices used to transmit ECGs to base station hospitals from paramedics. Bandy R, Orban DJ, Geiderman JM: Application of the Cardiotrak TM pacemaker monitor to prehospital care. Ann Emerg Med 10:579-581, November 1981.
pacemaker monitor, prehospital use INTRODUCTION The Cardiotrak TM* is a small device originally developed for pacemaker patients to enable them to send electrocardiogram (ECG) tracings of their heart rhythms to cardiologists for interpretation 1 -3 / (personal communication, B. Goldreyer, August 1980). The heart rate and pacemaker activity are monitored by the physician, who then may advise the patient to go to the hospital, change the medication, or do nothing. The Cardiotrak sends an ECG of an intrinsically paced heart, and thus seemed well suited for field use by paramedics. The emergency departments of UCLA and Cedars-Sinai Medical Center, in cooperation with the City of Los Angeles Fire Department, conducted a pilot project to confirm or refute our initial impression that the Cardiotrak would be beneficial for routine telemetry use, and that it has significant advantages over other systems in current use. Data collected for 76 runs in 60 days are presented and evaluated.
MATERIALS The Cardiotrak is the same general size as a pocket calculator, and is battery operated, lightweight, and relatively inexpensive (Figure 1). It works by emitting a variable pitch tone, depending on the electrical activity of the heart. The tones are sent by telephone to a base station where telemetry translates them into a readable ECG. The device is simply placed on the patient's anterior chest, and a phone receiver is held close to it. This is more quickly and easily set up than are chest leads; contact paste is not necessary; and the tones can be heard immediately once the Cardiotrak is placed against the chest (Figure 2). *Registered Trademark, C.P.I. by Instromedex, Incorporated, Portland, Oregon. From the Department of Medicine, Division of Emergency Medicine, UCLA Hospital and Clinics;* and the Department of Emergency Medicine, Cedars-Sinai Medical Center,t Los Angeles, California. Address for reprints: Joel M. Geiderman, MD, Department of Emergency Medicine, CedarsSinai Medical Center, 8700 Beverly Boulevard, Los Angeles, California 90048.
10:11 (November) 1981
Ann Emerg Med
579/45
The tone can be t r a n s l a t e d into a t r a c i n g by c o n v e n t i o n a l B i o c o m equipment or o v e r M o t o r o l a l a n d line receivers. The Cardiotrak offers significant advantages o v e r t h e c o n v e n t i o n a l phone patch kit, which is too awkward to carry r o u t i n e l y to the site of an arrest. Moreover, the k i t is more difficult to place, a n d s e t - u p t i m e s tend to be l o n g e r . A n a d d i t i o n a l problem with the phone k i t is t h a t it fits only the s t a n d a r d , conventional phone receiver; it could not be used with Princess TM, Trimline TM, or other specialty phones (Figure 3).
METHODS Records were k e p t for 60 days by both t h e p a r a m e d i c s a n d t h e b a s e s t a t i o n s on a l l r u n s in w h i c h t h e Cardiotrak could be used. Personnel at both sites were asked to record the c l a r i t y of t r a n s m i s s i o n , e s t i m a t e d length of time to set up, and other subjective comments. R h y t h m strips were saved and a t t a c h e d to the evaluation sheets for review. The r e s u l t s were e v a l u a t e d and t a b u l a t e d .
F i g . 1. Cardiotrak pacemaker monitor.
RESULTS A total of 76 C a r d i o t r a k evaluat i o n s h e e t s w e r e r e t u r n e d for t h e period of A u g u s t 7 t h r o u g h October 14, 1980. In 69 p a t i e n t s (91%), clear E C G t r a n s m i s s i o n s w e r e n o t e d by the base s t a t i o n , w i t h no a p p a r e n t problems. On only seven of t h e 76 s t r i p s (9%) were a n y p r o b l e m s reported by the hospitals. Two of these were from one engine c o m p a n y which, on successive runs, noted t h a t the C a r d i o t r a k tracings a p p e a r e d as flat lines, y e t the c l i n i c a l c o n d i t i o n s of t h e p a t i e n t s w e r e g o o d . I t w a s n o t e d on t h e second report t h a t the b a t t e r y of the C a r d i o t r a k was c h a n g e d , a n d t h a t i n c r e a s i n g t h e g a i n on the Biocom equipment solved the problem. Another s e p a r a t e incident was due to low b a t t e r y p o w e r as well. O t h e r c o m m e n t s were t h a t , on two occasions, t h e s t r i p s w e r e d i f f i c u l t to read. In one case, 60-cycle interference overlapped sinus rhythm; nevertheless, it was easy to i n t e r p r e t the presence of n o r m a l sinus r h y t h m with a r a t e of 75 and a n o r m a l QRS complex. A n o t h e r p r o b l e m occurred because a telephone fell off a . d e s k a n d b e c a m e d i s c o n n e c t e d . I n one other case, confusion arose because a patient's relative b e g a n u s i n g an extension telephone d u r i n g a run.
46/580
F i g . 2. Cardiotrak placed on anterior chest, coupled to telephone.
Positive comments were that, with slight repositioning of the Card i o t r a k on t h e chest, the strip could e a s i l y be s e n t w i t h perfect clarity. One squad r e p o r t e d t h a t t h e y were in a remote a r e a and would not have been able to t r a n s m i t over the Biocorn due to t h e i r location. One r u n t e s t e d t h e C a r d i o t r a k with the radio transmitter rather than the land-line. The reception was '~good, b u t only s o m e w h a t clear." PVCs were slightly difficult to interpret but, in comparison, the t r a c i n g sent by the radio alone was not as
Ann Emerg Med
clear as was the C a r d i o t r a k tracing. A t base station m e e t i n g s and at the conclusion of the trial, t h e p a r a medics' comments were only positive, p r a i s i n g the ease and convenience of using C a r d i o t r a k . One p a r a m e d i c s u g g e s t e d t h a t b e c a u s e t h e t o n e is a u d i b l e , t h e sound of the p a t i e n t ' s own h e a r t b e a t may cause apprehension and may cause a change in the v i t a l signs, as occurs w i t h m o n i t o r sounds in t h e critical care unit, the sound of ambulance sirens, or the p e r f o r m a n c e of blood pressure m e a s u r e m e n t .
10:11 (November) 1981
DISCUSSION Our trial has shown the Cardiotrak to be an effective, easy-to-use tool for use in transmitting ECGs from the field to the base station. Its use requires only a nearby telephone of any type. When a telephone is not available, it may be coupled successfully with radio equipment. Cardiotrak offers a number of distinct advantages over other equipment. First, it is small, portable, and lightweight, and thus can be carried easily in a "starter kit" taken to the patient's bedside. Because it is easy to carry, it can be available both when a cardiac problem is suspected and when monitoring becomes necessary unexpectedly. As previously noted, all that is necessary to complete the transmission is a nearby phone of any type. In contrast, previously developed phone patch kits could be used only with standard conventional phones. Set up time for the C a r d i o t r a k is a few seconds, whereas the phone patch kit takes one or two minutes, assuming it has been carried to the scene. Contact is quicker by telephone than by radio, and the problem of transmission break-up that is often encountered with radio use is nonexistent. With current methods, problems with telemetry transmission or interference by another signal in the area results in an ECG which is completely non-translatable. When this happens, the base station is forced to repeat the strip, and a great deal of time may be lost. Use of the telephone has been particularly effective in hillside areas or in s t r u c t u r e s from which clear radio signals cannot be transmitted. Another advantage to the phone is that several calls can be received simultaneously without interfering with each other. Confusion t h a t arises d u r i n g s i m u l t a n e o u s r u n s while Using the radio can actually be dangerous. Using the C a r d i o t r a k when a phone is accessible tends to keep the a i r w a y s clear for other situations for which radio communication is the only method available. Battery failure may occur with either the phone-patch kit or the Cardiotrak. Battery failure can be detected early with the Cardiotrak, because a weak signal will be sent. Spare batteries can be carried and changed quickly if necessary.
10:11 (November) 1981
Fig. 3. Phone patch kit, with accessory equipment, coupled to standard telephone. Leads must be attached to patient (not shown). When defibrillation is necessary, the standard Lifepak ~ (PhysioControl Corporation, Redmond, Washington) paddles may be used exactly as if radio communication were established. The Cardiotrak does not int e r f e r e with " q u i c k - l o o k " paddle placement, defibrillation energy, or the performance of cardiopulmonary resuscitation in situations of cardiac arrest. The Cardiotrak may be useful for monitoring en route if coupled to the radio; however, the only advantage of this is in the event that the p a t i e n t did not have chest leads placed, or if chest leads would not stick to the patient's chest for some reason. Finally, patient anxiety may be minimized with careful explanation of the tone and a demonstration prior to placing the device on the patient's chest. The most experienced paramedics have not found "patient fear" to be a problem. CONCLUSION The Cardiotrak is a small, lightweight, relatively inexpensive device that is well suited for ECG transmission by paramedics. The device must be coupled with a radio transmitter when a land-line telephone is not available. A two-month field test at two
Ann Emerg Med
h o s p i t a l s in Los Angeles demonstrated the efficacy of the device. Most problems t h a t were encountered could be alleviated by keeping the Cardiotrak batteries charged. Advantages of the Cardiotrak over radiotelemetry are that it is easier to set up, t r a n s m i s s i o n is clearer, simultaneous transmissions do not interfere, transmission is private, and it may be used in areas in which physical conditions make radio transmission impossible. Its a d v a n t a g e s over p r e v i o u s phone patch kits are that it is less cumbersome, easier to set up, and may be adapted to any phone. The authors thank Chief John Gerard of the Los Angeles City Fire Department, and John Green, MICP, for their support in this project. We also thank Dana Taliaferro, RN, Linda Verraster, RN, and Baxter Larmon, MICR for their support in collecting data. REFERENCES 1. Furman S: The future utility of transtelephonic pacemaker monitoring. J Electrocardiol 9:199, 1976. 2. Furman S, Parker B, Escher DJW: Pacemaker clinic via telephone. Bull Heart Inst Jap 14:1, 1970. 3. Sakurai Y, Aoki E, Terashimu M: Pacemaker clinic by telephone transmission. Artificial Organs 4:357, 1975.
581/47