Letter to the Editor
2000; American Physiological Society; Volume: 88; Issue: 4 Linguagem: Inglês
10.1152/jappl.2000.88.4.1509
ISSN8750-7587
Autores Tópico(s)Hemodynamic Monitoring and Therapy
ResumoLETTERS TO THE EDITORLetter to the EditorGerard CybulskiGerard Cybulski Department of Applied Physiology Medical Research Centre Polish Academy of Sciences 5 Pawinskiego Str. 02106 Warsaw, Poland E-mail: Published Online:01 Apr 2000https://doi.org/10.1152/jappl.2000.88.4.1509MoreSectionsPDF (61 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail Ambulatory impedance cardiography: new possibilitiesTo the Editor: The primary objective of the study by Sherwood et al. (5) was “to assess how a newly developed ambulatory impedance monitor (AIM) would compare with established impedance cardiographic instrumentation.” Furthermore, “the study's objective was not to revisit the validation of impedance cardiography as a technique per se but rather to evaluate whether the AIM system, with its unique hardware and electrode configuration, would yield cardiovascular function indexes similar to those that are obtained with standardized impedance cardiographic methodology.”In my opinion, simultaneous, long-time recording of electrocardiogram and the signal reflecting the central hemodynamic activity might bring some further useful diagnostic data, particularly in arrhythmia patients and in pharmacological studies. Considering all limitations of the technique, it seems that electrical impedance cardiography, as a simple method for continuous, noninvasive determination of stroke volume, maximum velocity of ejection, and ejection time, could be used to provide such a signal. Cardiac contractility and the stroke volume indexes might be also used for determination of hemodynamic efficiency in healthy individuals (in sports medicine or work physiology) or in patients during regular pacing and arrhythmic or ischemic events for supplementary diagnosis or for evaluation of pharmacological therapy.From this point of view, development of the new device and the feasibility study performed by Sherwood et al. (5) seem to be important and very promising. However, these authors, who describe the “unique hardware and electrode configuration” of their AIM system, did not mention previous achievements in this field. According to a search performed using the Ovid Technologies database (which I accessed after publishing my papers on this subject), the idea of impedance cardiography ambulatory monitoring with signal recording on memory chips was introduced in 1985 and 1987 by Webster's group (4, 7) and, with the use of Personal Computer Memory Card International Association (PCMCIA) cards, in 1995 and 1996 by Cybulski et al. (1, 2). These conference papers were published in books by IEEE or Peter Peregrinus. In 1996, Willemsen et al. (6) described the ambulatory monitoring of impedance cardiogram device and the results collected in 25 subjects in various conditions and in 26 subjects during 24-h monitoring. This device, however, enabled only storage of the results of calculations performed on ensemble-averaged signals, so it did not give access to every single heartbeat.We have constructed an ambulatory-monitoring, four-channel recorder that allows the simultaneous collection of electrocardiogram and impedance cardiography signals from a built-in miniaturized impedance cardiography device on a 20-MB PCMCIA Flash Memory Card (1, 2). This system allows for off-line, beat-to-beat automatic evaluation of cardiac output, stroke volume, ejection time, preejection period, and heart rate. The system was checked in 80 healthy subjects in ambulatory conditions (1-3). During the day, the percentage of properly recognized heart cycles with respect to all above-mentioned parameters varied from 20 to 80% and at night from 75 to 90%. Speaking and vigorous movements markedly lowered this percent. The system was also used in clinical examinations to demonstrate the hemodynamic efficiency of pacing and in 10 arrhythmic patients. A similar study showed the increased variability of stroke volume in patients with atrial fibrillation. Some interesting data were also obtained before and during 8-s asystole in a young man provoked by the tilt test (3). Also in this study (3), hemodynamically efficient and nonefficient cardiac supraventricular ectopics were shown in the same patient. Using the system, we were also able to demonstrate the hemodynamic effects of dynamic exercise on a cycloergometer with the work load up to 200 W (7).Technically, our system is very flexible and can be easily adapted for recording from various physiological signal sensors, such as a breathing detector or pulse oximeter, which may extend the number of its applications.I am very pleased that Sherwood et al. (5) successfully developed and initially tested another construction; their work may help in the exchange of ideas on possible applications of their system and the technique per se in the future.REFERENCES1 Cybulski G, Ksia̧z˙kiewicz A, Łukasik W, Niewiadomski W, and Pałko T. Ambulatory monitoring device for central hemodynamic and ECG signal recording on PCMCI flash memory cards.Computers in Cardiology.1995505507IEEENew YorkGoogle Scholar2 Cybulski G, Ksia̧z˙kiewicz A, Łukasik W, Niewiadomski W, and Pałko T. Central hemodynamics and ECG ambulatory monitoring device with signals recording on PCMCIA flash memory cards.Med Biol Eng Computing34, Suppl. 119967980Google Scholar3 Cybulski G, Ziółkowska E, Kodrzycka A, Niewiadomski W, Sikora K, Ksia̧z˙kiewicz A, Łukasik W, and Pałko T. Application of impedance cardiography ambulatory monitoring system for analysis of central hemodynamics in healthy man and arrhythmia patients.Computers in Cardiology.1997509512IEEENew YorkGoogle Scholar4 Qu M, Webster JG, Tompkins WJ, Voss S, Bogenhagen B, Nagel F.Portable impedance cardiograph for ambulatory subjects.Proceedings of the Ninth Annual Conference of the IEEE Engineering in Medicine and Biology Society.3198714881489IEEENew YorkGoogle Scholar5 Sherwood A, McFetridge J, Hutcheson JS.Ambulatory impedance cardiography: a feasibility study.J Appl Physiol85199823652369Link | ISI | Google Scholar6 Willemsen GH, De Geus EJ, Klaver CH, Van Doornen LJ, Carroll D.Ambulatory monitoring of the impedance cardiogram.Psychophysiology33199618493Crossref | ISI | Google Scholar7 Zhang Y, Qu M, Webster JG, Tompkins WJ.Impedance cardiography for ambulatory subjects.Proceedings of the Seventh Annual Conference of the IEEE/Engineering in Medicine and Biology Society. Frontiers of Engineering and Computing in Health Care.21985764769IEEENew YorkGoogle ScholarjapjapJAPPLPHYSIOLJournal of Applied PhysiologyJ Appl Physiol1522-16018750-7587American Physiological SocietyBethesda, MDLETTERS TO THE EDITOR 14200088415091510The following is the abstract of the article discussed in the subsequent letter:Sherwood, Andrew, Judy McFetridge, and J. Stanford Hucheson. Ambulatory impedance cardiography: a feasibility study.J. Appl. Physiol. 85(6): 2365–2369, 1998.—A wearable, ambulatory impedance monitor (AIM) has been developed to permit impedance cardiographic measurements while patients and volunteers engage in normal daily activities. The AIM system was developed for use with a new hybrid tetrapolar spot-band electrode configuration and was designed to be comfortable and inconspicuous. The objective of the present study was to provide a preliminary evaluation of AIM comparability with the widely validated Minnesota model 304B impedance cardiograph with standard tetrapolar band electrodes. Orthostatic challenge was used to systematically alter cardiac function in a laboratory setting in 11 healthy men and women. Both while the subjects were sitting and while they were standing, the AIM yielded measures of cardiac function, including heart rate, preejection period, left ventricular ejection time, and stroke volume, that were similar to those acquired by using the reference Minnesota 304B system (all Pearson R correlation > +0.87, all P < 0.001). Cardiac responses to postural shift, expressed as change measures from sitting to standing, were also comparable for the AIM and Minnesota reference monitoring systems. Potential applications, including the assessment of 24-h hemodynamic profiles, are illustrated and discussed. Previous Back to Top FiguresReferencesRelatedInformationCited ByOvercommitment to Work Is Associated With Changes in Cardiac Sympathetic RegulationPsychosomatic Medicine, Vol. 66, No. 5Temporal stability of twenty-four-hour ambulatory hemodynamic bioimpedance measures in African American adolescentsBlood Pressure Monitoring, Vol. 9, No. 4 More from this issue > Volume 88Issue 4April 2000Pages 1509-1510 Copyright & PermissionsCopyright © 2000 the American Physiological Societyhttps://doi.org/10.1152/jappl.2000.88.4.1509PubMed10819621History Published online 1 April 2000 Published in print 1 April 2000 PDF download Metrics Downloaded 112 times
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