Impedance Cardiography Monitoring Research Articles

Development of Multi-Parameter Exercise Cardiopulmonary Function Evaluation System with Impedance Cardiogram Monitoring

Cardiopulmonary exercise testing (CPET) refers to a method of measuring various indicators of the human body under gradually increasing exercise loads to objectively evaluate cardiopulmonary reserve function and exercise endurance. Currently, CPET detection systems primarily measure subjects' ECG, respiratory flow, oxygen (O 2), and carbon dioxide (CO 2) parameters. This paper introduces a non-invasive multi-parameter exercise cardiopulmonary function evaluation system that incorporates impedance cardiography monitoring. The system integrates impedance cardiography monitoring with conventional CPET detection parameters and detects changes in the hemodynamic parameters of the body during exercise, aiding in the evaluation of exercise capacity. Additionally, the system features a portable design with Wi-Fi wireless transmission, which enhances its applicability.

Differences in Hemodynamic Response to Passive Leg Raising Tests during the Day in Healthy Individuals: The Question of Normovolemia.

The passive leg-raising (PLR) test was developed to predict fluid responsiveness and reduce fluid overload. However, the hemodynamic response of healthy individuals to the PLR test and how it changes during the day, between the morning and evening, after individuals have consumed food and fluids, has not been profoundly explored. This study aimed to compare the systemic hemodynamic changes in healthy individuals between morning and evening PLR tests. In this study, the PLR test was performed twice a day. The first PLR test was performed between 08h00 and 09h00 in the morning, while the second PLR test was performed between 20h00 and 21h00 in the evening. Hemodynamic parameters were measured using an impedance cardiography monitor, and a cutoff value of a 10% increase in stroke volume (SV) during the PLR test was used to differentiate between preload responders and non-responders. We included 50 healthy volunteers in this study. When comparing the morning and evening PLR test results, we found no PLR-induced differences in heart rate (-3 [-8-2] vs. -2 [-8-4] beats/min, p = 0.870), SV (11 [5-22] vs. 12 [4-20] mL, p = 0.853) or cardiac output (0.7 [0.2-1.3] vs. 0.8 [0.1-1.4] L/min, p = 0.639). We also observed no differences in the proportion of preload responders during the PLR test between the morning and evening (64% vs. 66%, p = 0.99). However, there was a moderate agreement between the two PLR tests (morning and evening) (kappa = 0.429, p = 0.012). There was a moderate correlation between the changes in SV between the two PLR tests (rs = 0.50, p < 0.001). In young, healthy individuals, we observed no change in the systemic hemodynamic responsiveness to the PLR test between the morning and evening, without restriction of fluid and food intake.

Nepalankių kraujotakos reakcijų išsivystymo prognozavimas ir paciento kūno padėties įtaka širdies minutiniam tūriui mažųjų anorektalinių operacijų metu

Tikslas. Nustatyti pradinio širdies minutinio tūrio, matuojamo impedanso kardiografijos metodu, ribą, leidžiančią prognozuoti nepalankių kraujotakos reakcijų, sąlygotų paciento kūno padėties pokyčių, vystymąsi anorektalinių operacijų, atliekamų mažos dozės vietinių anestetikų spinalinėje nejautroje, metu pacientams, sergantiems lydimąja kardiovaskuline patologija.Darbo metodika. Perspektyvusis, stebimasis, klinikinis tyrimas, į kurį įtraukti 48 pacientai, įvertinti ASA 3 funkcinės būklės klase, turintys lydimąją kardiovaskulinę patologiją, stacionarizuoti mažajai anorektalinei operacijai, kuri atlikta mažos vietinių anestetikų dozės spinalinėje nejautroje. Iš jų 3 pacientai į vėlesnį tyrimą neįtraukti dėl įtraukimo kriterijų neatitikimo. Pacientai užklijuotų vokų metodo pagalba, atsitiktine tvarka buvo suskirstyti į dvi grupes: I grupė (n=24), tai pacientai, kuriems operacija atlikta paguldžius į lenktinio peilio padėtį, II grupė (n=24) – pacientai, kuriems operacija atlikta paguldžius į litotomijos padėtį. Operacijos metu buvo stebimi ir registruojami standartiniai rodikliai: širdies susitraukimų dažnis, elektrokardiograma, arterinis kraujo spaudimas bei impedanso kardiografijos parametrai: širdies minutinis tūris, sistolinis tūris, sisteminis kraujagyslių pasipriešinimas. Spinalinė anestezija buvo atlikta sušvirkščiant į subarachnoidinį tarpą 0,8ml (4mg) 0,5proc. hiperbarinio bupivakaino ir 0,2ml (10μg) fentanilo. Rezultatai. Širdies susitraukimų dažnis ir vidurinis arterinis kraujo spaudimas tarp grupių ir grupės viduje nesiskyrė (p&gt;0,05). Širdies minutinis tūris statistiškai reikšmingai sumažėjo nuo pradinio 6,2±1,4 l/min. iki 3,1±0,9 l/min. pacientą paguldžius į lenktinio peilio padėtį ir išliko sumažėjęs operacijos pradžioje (3,0±0,8 l/min.) bei pabaigoje (3,1±0,7 l/ min.). Atitinkamai skirtumas tarp I ir II grupių paguldžius į operacijos padėtį buvo 3,7 l/min., operacijos pradžioje - 3,3 l/min. ir operacijos pabaigoje - 3,1 l/min. (p&amp;lt;0.05). Atlikus diskriminantinę analizę nustatėme, jog pradinė širdies minutinio tūrio riba, kuriai esant tikėtina, kad paguldžius pacientą į lenktinio peilio padėtį širdies minutinis tūris bus mažesnis nei 3,0 l/min., yra &amp;lt;5,94 l/min. Išvados. Lenktinio peilio padėtis anorektalinių operacijų metu veikia širdies minutinio tūrio sumažėjimą. Pacientams, įvertintiems ASA 3 klase dėl kardiovaskulinės patologijos, širdies minutinis tūris sumažės iki &amp;lt; 3,0 l/min., pacientą operacijos metu paguldžius į lenktinio peilio padėtį, esant pradiniam širdies minutiniam tūriui &amp;lt; 5,94 l/min.

Comparison of cardiac output derived from FloTrac™/Vigileo™ and impedance cardiography during major abdominal surgery

Impedance cardiography (ICG) is a noninvasive technique that provides reasonably accurate measurements of cardiac output, but the usefulness of ICG in patients undergoing open abdominal surgery has not been validated. Cardiac output was measured while patients underwent open gastrectomy using an ICG monitor (niccomo™; ICG-CO); the results were compared with those measured using a FloTrac™/Vigileo™ monitor (Flo-CO), which measures cardiac output by analysing the arterial waveform. Data collection commenced at the beginning of anaesthetic induction and continued until the patient was awake. Data were compared using the Bland-Altman analysis, and the clinical significance of the difference between the two methods was evaluated by calculating the percentage error (%). Eleven patients were monitored during surgery. The bias of the Flo-CO and ICG-CO values was -0.45 l/min. The upper and lower limits of agreement were 0.96 l/min and -1.85 l/min, respectively. The percentage error was 28.5%. Electrocautery induced interference that transiently impaired the performance of the ICG monitor. ICG provided useful information in evaluating the cardiac output of patients during abdominal surgery.

Transthoracic Impedance Cardiography: A Noninvasive Method of Hemodynamic Assessment

Impedance cardiography technology, along with recent advances in the impedance cardiography (ICG) device, has become a provocative but not yet proven noninvasive alternative to invasive hemodynamic measurements. The results from stroke volume and cardiac output measurements by ICG show reasonably accurate correlation to the values calculated from direct measurements from pulmonary artery catheters. ICG may be a useful adjunct to clinical judgment for heart failure patients. The available data would not yet support supplanting invasive hemodynamic assessment in the critical care setting with ICG. Future studies and advances in technology are expected to improve impedance cardiography, thus broadening its clinical applications. Ongoing research must confirm the precise benefits of this information for ICG monitoring to become a standard assessment in heart failure.

Impedance Cardiography

Endoscopic thoracic sympathectomy (ETS) is a minimally invasive procedure for treating palmar hyperhidrosis (PH). Hemodynamic changes are associated with CO(2) insufflation during ETS. In the present study, we examined hemodynamic changes during general anesthesia using impedance cardiography (ICG) monitor. Seventeen adult patients (15 males) scheduled to undergo elective unilateral ETS for treatment of PH were enrolled in the study. Patients with cardiorespiratory diseases were excluded from the study. Their age and weight mean values were 26.5 +/- 5 years, 71.9 +/- 11.5 kg, respectively. Besides routine monitoring, impedance cardiography monitor was used to measure cardiac output (CO), cardiac index (CI), stroke volume (SV), thoracic fluid content (TFC), and systemic vascular resistance (SVR). Three phases were defined for data collection: A, prior to CO(2) insufflation; B during gas insufflation (at 10, 5, and 2 mm Hg intrathoracic pressures); and C, after gas deflation. Repeated-measures analysis of variance (ANOVA) was used for statistical analysis and post hoc Bonferroni test for multiple comparisons of the data obtained. For all comparisons, P < 0.05 was considered significant. Systemic vascular resistance significantly increased at stages B10 and 5 compared with stage A mean value (P < 0.05). CO, CI, and SV mean values decreased significantly at stage B compared with stage A mean values. The mean values of thoracic fluid content at stages A, B10, 5, 2, and C were 33 +/- 5, 30.6 +/- 3.5, 31 +/- 3.4, 31.6 +/- 3.3, and 32.5 +/- 6.8/kOmega, respectively with significant differences (P < 0.05). Significant reductions of cardiac parameters were reported in the present study, but they were of minimal clinical significance. Of interest was the significant reduction of thoracic fluid content during CO(2) insufflation, whether it correlates to the magnitude of compression, caused by CO(2) insufflation accompanied by high systemic vascular resistance or sympathectomy procedure, yet to be further studied.

Hemodynamic and Pulmonary Fluid Status in the Trauma Patient: Are We Slipping?

Recent reports point to problems in the clinical assessment of the cardiopulmonary system in hemodynamically unstable patients, especially with the decreasing usage of pulmonary artery catheters. Our purpose was to evaluate the hypothesis that clinical judgment alone is inadequate for a reliable estimate of cardiopulmonary status in critically ill patients. Physician assessments (high, normal, or low) of cardiac index (CI) and thoracic fluid content (TFC) were made in 68 acute trauma cases and compared to the results obtained with impedance cardiography (ICG). Physician assessment using clinical judgment alone was correct only 42 per cent and 57 per cent, respectively, for CI and TFC. There was very little difference in heart rate (HR), blood pressure (BP), Glasgow Coma Score (GCS), and the number of injured systems between the incorrect and correct assessments of CI. However, the mean Injury Severity Score (ISS) was markedly higher for the incorrect than the correct CI values (18.8 +/- 9.3 vs 14.2 +/- 9.8, P = 0.0589). Thus, there is a need for an objective measurement of CI and TFC especially in the more severely injured patient. The inaccuracy of the clinical exam strongly suggests the need for a supplemental measurement, which the new and improved ICG monitor could provide.

Impedance Cardiography: Noninvasive Assessment of Hemodynamics and Thoracic Fluid Content During Bariatric Surgery

The effects of pneumoperitoneum (ppm) on hemodynamic parameters during bariatric surgery were investigated using the impedance cardiography monitor. 11 patients with BMI 46.5+/-10 kg/m2 (range 38.9-60.8 kg/m2) underwent laparoscopic adjustable gastric banding under general anesthesia. Besides routine monitoring, the impedance cardiography (ICG) monitor was used to monitor cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), and thoracic fluid content (TFC). Data were recorded at three stages: A) before ppm, B) during ppm, and C) after gas deflation. One-way analysis of variance (ANOVA) was used to analyze differences of the data before, during and after ppm, and post-hoc (Bonferoni test) for multiple comparisons of the data obtained. For all comparisons, P<0.05 was considered significant. There were significant low mean values of heart rate (HR), CO and CI at stage B compared to stage A (P<0.05). The mean values of TFC at stages A, B, and C were 30.48 +/- 4.69, 29.74 +/- 2.86 and 31.72 +/- 4.93 k/Ohm respectively, with a non-significant relationship (P>0.05). The mean values of SVR during the same stages A, B and C were 1299.18 +/- 374.40, 1873.64 +/- 276.26 and 1669.36 +/- 537.92 dynes sec cm(-5) respectively, with significant high mean values at stages B and C compared to mean value at stage A (P<0.05). Morbid obesity and pneumoperitoneum have significant effects on hemodynamics. However, it appears that these changes were of marginal clinical significance.

Efficacy of noninvasive hemodynamic monitoring to target reduction of blood pressure levels (the control trial)

Use of impedance cardiography (ICG) can improve blood pressure (BP) control in resistant hypertension (HTN). The purpose of this study was to determine if ICG could aid primary care physicians in increasing BP control in mild to moderate HTN. Patients (pts.) with uncontrolled HTN evidenced by systolic BP (SBP) of 140 - 179 mm Hg and/or diastolic BP (DBP) of 90 - 109 mm Hg on 1–3 anti-hypertensive medications were enrolled and randomized by a 3:2 sequence of standard care to ICG-guided care and stratified by site. Each pt. completed 5 study visits that included a 2-week washout followed by 3 months of active treatment. ICG data (BioZ ICG Monitor, CardioDynamics) including cardiac index (CI), systemic vascular resistance index (SVRI), and thoracic fluid content (TFC) were collected in both arms but only revealed in the ICG-managed arm. 164 pts. from 11 centers completed the study, 95 in the standard care and 69 in the ICG-managed arm. There were no differences in the standard care vs. ICG-managed arm in age (55 vs. 54 yrs), gender (54 vs. 55% male), race (79 vs. 77% white), and prevalence of diabetes (5 vs. 4%), ischemic heart disease (2 vs. 7%), or hyperlipidemia (16 vs. 17%). There were also no differences at the enrollment and post-washout visit in SBP (147 vs. 148 and 155 vs. 155 mm Hg), DBP (87 vs. 89 and 92 vs. 94 mm Hg), or number of anti-hypertensive meds (1.7 vs. 1.7 and 0.0 vs. 0.0). At enrollment, pts. in the standard care and ICG-managed arm had similar CI (2.9 vs. 2.9 L/min/m2), SVRI (2,873 vs. 2,933 dyne sec m2 cm−5), and TFC (28.6 vs. 28.5 /kOhm). At the final visit, pts. in the ICG-managed care arm had a lower SBP (129 vs. 137 mm Hg, p<0.01) and DBP (78 vs. 82 mm Hg, p<0.05), greater drop in SBP (19 vs. 11 mm Hg, p<0.01) and DBP (11 vs. 5 mm Hg, p<0.001), and higher rates of BP control to < 140/90 mm Hg (78 vs. 55%, p<0.01) and 130/85 mm Hg (55 vs. 29%, p<0.01). Pts. in the ICG-managed care arm had no differences in the number of anti-hypertensive meds (2.1 vs. 2.0) although more were on angiotensin II receptor blockers (52 vs. 32%, p<0.05) and had a greater drop in SVRI (375 vs. 164 dyne sec m2 cm−5, p<0.05). These data are the first to show that in pts. with mild to moderate HTN on 1 or more anti-hypertensive meds, ICG-guided therapy results in greater reductions in systolic and diastolic BP and increased BP control rates.

Cardiopulmonary Assessment: Is Improvement Needed?

Clinical parameters alone have repeatedly been proven unreliable in assessing cardiopulmonary status, especially in hemodynamically unstable patients. To learn if we had a diagnostic problem in our hospital, we compared physician assessment of cardiac index (CI) and thoracic fluid content (TFC) to values obtained using impedance cardiography (ICG). We selected the newest available ICG monitor, the BioZ, which employs this noninvasive technology. For CI measurements we have shown it to be equivalent to thermodilution and to be more reproducible (variability: 6.3% vs. 24.7%). Physician assessment of CI and TFC (high, normal, or low) was compared to the BioZ monitor's results in 186 patients, considered to be hemodynamically unstable, from the emergency room, the intensive care units, and the floors. Normal values were defined for CI (2.5-4.2 L/min m(2)) and for TFC (males: 30-50 kohm(-1) and females: 21-37 kohm(-1)). The concordance between physician assessment and the BioZ was 51% for CI with Kappa of 0.14 and 58% for TFC with Kappa of 0.19. Attendings did slightly better than the surgical residents with CI (52% vs. 48%) but slightly worse with TFC (57% vs. 61%). The potentially serious conditions of low CI and high TFC were misdiagnosed 42% and 46% of the time, respectively, by all physicians. Analysis of the data revealed that physician use of clinically available objective hemodynamic data, such as heart rate, blood pressure, and pulse pressure index, would not have been helpful. Furthermore, assistance from the pulmonary artery catheter (PAC) is often not available in our hospital, which has experienced a 90% decrease in its utilization over the past six years. Considering the increasing acuity of our aging patient population, accurate assessment of cardiopulmonary status is needed. The use of ICG could be a valuable addition to the physician's armamentarium.

Systolic blood pressure does not reliably identify vasoactive status in chronic heart failure

In chronic heart failure (CHF), titration of vasodilating medications is often guided by monitoring of systolic blood pressure (BP). However, systolic BP may not indicate the patient's true vasoactive status-best approximated by systemic vascular resistance-because cardiac output is also a contributing factor. Impedance cardiography (ICG) is a validated noninvasive method of measuring cardiac output and systemic vascular resistance. To evaluate the relationship between systolic BP and systemic vascular resistance index (SVRI) in patients with CHF, we retrospectively evaluated the systolic BP and SVRI from 71 consecutive patients during 615 CHF clinic visits. Measurement of systolic BP was through the oscillometric method and SVRI through ICG (BioZ ICG Monitor, CardioDynamics, San Diego, CA). Absolute values and relative changes in systolic BP and SVRI were compared and characterized by systolic BP grouping. The 71 patients were an average of 69.3 +/- 12.2 years, New York Heart Association functional class 2.52 +/- 0.6, 46.5% men, and 47.8% ischemic etiology. Frequency by systolic BP grouping was: <100 mm Hg in 67 subjects (10.9%), 100 to 119 mm Hg in 245 subjects (39.8%), and >/=120 mm Hg in 303 subjects (49.3%). The correlation (R(2) value) of systolic BP to SVRI was 0.21 (N = 615), and change in systolic BP to change in SVRI from previous visit was 0.27 (N = 547). In 138 visits in which systolic BP did not change by 5 mm Hg or more, SVRI changed by 20% or more in 41 (29.7%). In the 67 visits in which systolic BP was below 100, only 6 (9.0%) had low SVRI and 57 (85.1%) had normal SVRI. In the 245 visits with systolic BP 100 to 119, 58 (23.7%) had high SVRI. Measurement of systolic BP alone does not reliably indicate the degree of vasoconstriction or vasodilation that exists in patients with CHF. Measurement of SVRI by ICG may help guide determination of need and tolerance for vasodilating medications in CHF.

TFC (Thoracic Fluid Content): A New Parameter for Assessment of Changes in Chest Fluid Volume

Clinical assessment of cardiac status can be difficult and incomplete without an assessment of fluid volume status, especially of the lungs. Now, a new parameter is available, thoracic fluid content (TFC). It is an indicator of total fluid volume, both intracellular and extracellular. Because it is measured noninvasively using impedance cardiography (ICG), it could be a welcome addition to the physician's assessment. An evaluation of TFC was performed beginning with 1) an examination of chest impedance (Z) as an accurate means of following fluid changes, 2) the relationship of TFC to Z using both loop and spot electrodes, and 3) clinical applications of TFC. In 1) 12 dogs, Z was superior (r = 0.935, P < 0.006) to 10 traditional hemodynamic and gas transfer parameters in trending a lactated Ringer's infusion; 2) a plastic model, changes in TFC values derived from Z measurements using both loop and spot electrodes were virtually identical and paralleled infused saline (r = 0.999, P < 0.001); 3) the clinical setting, TFC trended fluid changes well. From these results, we conclude that TFC is a reliable measurement of chest fluid status and of changes in that fluid. Along with cardiac index (CI), also provided by the ICG monitor, TFC can be very helpful to the clinician.

Impedance cardiography: a bridge between research and clinical practice in the treatment of heart failure.

This paper proposes that impedance cardiography could narrow the gap between heart failure clinical research and the appropriate and timely application of new knowledge and technology in the care of patients with heart failure. Research variables and measurement strategies, identified in the heart failure scientific literature between 1994-1999, are compared to measures that can be obtained through a cost effective, noninvasive technology--impedance cardiography. Emphasis is placed on case reports that illustrate how "real time" evaluation and trending of key hemodynamic variables through impedance cardiography monitoring has been used to apply state of the science knowledge and technology to improve the inpatient and outpatient management of care for patients with severe heart failure. (c)2000 by CHF, Inc.

Cardiopulmonary exercise response in patients with left ventricular dysfunction or heart failure: a noninvasive study by gas exchange and impedance cardiography monitoring.

We investigated the upright bicycle exercise cardiopulmonary response in 20 patients with left ventricular dysfunction (LVD, secondary to previous myocardial infarction, left ventricular ejection fraction range 18-44%). Ten patients (48 +/- 7 years) asymptomatic (I NYHA class) without drug treatment (LVD group). The others (n = 10) (50 +/- 1 years) complained of dyspnea and/or fatigue despite therapy (NYHA II-III). They represented the heart failure (HF) group. Eight sedentary men (40 +/- 10 years) served as controls. Controls and patients performed stress testings under drug treatment, when administered. Anaerobic ventilatory threshold (ATge) was considered as an index of submaximal exercise while peak exercise VO2 (Peak VO2) was considered the maximal volitional exercise capacity. The ratio between minute ventilation (VE) to carbon dioxide release (VCO2) (VE/VCO2) was assessed to evaluate the ventilatory response during exercise. We coupled gas exchange assessment (2001, MGC) with noninvasive monitoring of stroke volume (SV) by impedance cardiography (NCCOM3, BOMED) and total systemic vascular resistances (TSVR; by auscultatory blood pressure measurement). In controls VO2 increase during exercise was related to higher heart rate (HR) and SV both from resting to ATge and from this point to the peak. TSVR declined during both steps. In patients with HF VO2 rose from resting to ATge (by faster HR and unchanged SV). VO2 increased slightly from this point to Peak VO2. This result was related to flat HR increase and unchanged SV as well as TSVR. In patients with LVD VO2 increased similarly to controls from resting to ATge and less above the threshold. In these patients both HR and SV increased during submaximal exercise. From ATge to Peak VO2 only HR increased. TSVR declined significantly similarly to controls. The VE/VCO2 ratio was higher at peak exercise in patients with HF compared to controls. Different determinants were demonstrated in patients with left ventricular dysfunction with mild or symptomatic chronic heart failure (CHF). These findings and the increased ventilatory response in patients with CHF can explain different changes of VO2 in these patients during submaximal and maximal voluntary exercise and contribute to explain exercise-induced exertion in these subjects.