Noninvasive Measurement Of Cardiac Output Research Articles

Non-Invasive Cardiac Output Monitoring in Neonates Using Bioreactance: A Comparison with Echocardiography

Objectives: Non-invasive cardiac output monitoring is a potentially useful clinical tool in the neonatal setting. Our aim was to evaluate a new method of non-invasive continuous cardiac output (CO) measurement (NICOM™) based on the principle of bioreactance in neonates. Methods: In this prospective observational study, 10 neonates underwent 97 paired NICOM and echocardiography (echo) assessments of left ventricular output (LVO). For each neonate, NICOM measurements of left ventricular stroke volume (SV) and LVO over a 2- to 4-hour period were correlated with blinded, simultaneous, discrete echo measurements of SV and LVO. The precision and accuracy of the NICOM monitor relative to echo during periods of steady state were assessed. Results: The infants’ median birth weight was 2.72 kg (IQR 1.56–3.23 kg, range 1.44–4.00) and their median gestation was 37 weeks (IQR 31–40 weeks, range 31–41). Median NICOM SV and LVO readings were consistently lower than echo (2.6 ml [IQR 1.4–3.2, range 0.6–5.3] vs. 3.5 ml [IQR 2.1–4.4, range 1.1–6.8], and 400 ml/min [IQR 233–476] vs. 559 ml/min [IQR 386–652], p < 0.001). The NICOM LVO readings were lower than the echo readings by a mean of 153 ± 56 ml/kg. NICOM consistently under-read LVO by 31 ± 8%, and this systematic difference was constant across the range of LVOs obtained. There was a strong correlation between NICOM and echo measurements of LVO (r = 0.95, p < 0.001). Conclusion: Non-invasive cardiac output monitoring is feasible in neonates. Further validation studies in neonatal animal experimental models and human neonates need to be conducted before routine clinical use.

Noninvasive Measurement of Cardiac Output During Exercise in Children with Tetralogy of Fallot

In patients with surgically repaired tetralogy of Fallot (TOF), reported peak oxygen consumption (VO(2)) is decreased compared with control subjects. The measurement of exercise cardiac output (CO) could be a useful adjunct for assessing cardiovascular fitness. There are few data assessing noninvasive CO, cardiac index (CI), and stroke volume (SV) during exercise for these patients. This study sought to measure noninvasive CI and SV during rest and exercise in children with repaired TOF. The authors compared 21 asymptomatic children with repaired TOF ages 11-17 years during rest and exercise and 42 gender- and age-matched healthy control children without structural heart disease. Using a Bruce exercise protocol, exercise data were measured noninvasively by a novel inert gas rebreathing technique including peak duration and heart rate, as well as VO(2), CO, CI, and SV measured at 90 % of peak predicted theoretical heart rate (90 % ppHR). Statistical correlation between peak VO(2) and CI was performed. At baseline, there was no statistically significant difference in any of the measures between the groups. At 90 % ppHR, there was an increase in CI during exercise of 140 % in the TOF children and 180 % in the control children. During exercise, SV changed minimally in the patient group, whereas it increased more than 30 % in the control children. At 90 % ppHR, the patient group showed an increase in VO(2) during exercise similar to that of their healthy peers. The patients had a significantly shorter peak exercise duration than normal control subjects. The patients had a lower CI during exercise because they were less able to increase SV. Therefore, at similar heart rates, patients who have had TOF repair must rely on increased peripheral muscle extraction, with a higher arteriovenous oxygen difference (SaO(2)-MvO(2)) during exercise, which may limit peak exercise capacity. In this cohort of TOF patients, noninvasive CI measurement was feasible, and correlation with VO(2) was good.

Clinical evaluation of a new tracheal impedance cardiography method

Non-invasive cardiac output measurement by means of impedance cardiography has been evaluated before, and agreement with other methods has been variable. We decided to study a newly developed tracheal impedance device, that is claimed to be more accurate and reliable. This incorporates new software and mathematical formulae, that are designed to reduce signal noise from diathermy, leading to improved accuracy. In 25 cardiothoracic surgery patients, simultaneous measurements were performed using both pulmonary artery thermodilution and the tracheal impedance device, at five peri-operative time points: before skin incision; after weaning from cardiopulmonary bypass; after sternal closure; and 30 min and 2 h after arrival in the intensive care unit. Mean cardiac output, bias and 95% limits of agreement were 5.3, 0.03 and -2.8 to 2.8 l.min(-1) , respectively. Tracheal impedance showed good correlation with measurement trends using thermodilution in 88% of measurements, with a mean (95% limit of agreement) angular bias of -9.0° (-83.3 to 65.3°). However, the wide limits of agreement and high percentage error of 53% that were apparent in this study mean that, in its present guise, tracheal impedance is not an acceptable alternative to thermodilution in cardiac surgical patients.

Abstract P317: Cognitive Impairment in Coronary Artery Disease Patients: Do Exercise Tolerance and Cerebral Oxygenation During Exercise Matter?

Introduction: Cardiovascular diseases have been associated with impaired cognitive performances, especially in functions. In contrast, it is clearly established that regular physical activity maintained throughout life protects against age-related cognitive decline. Purpose: to assess maximal oxygen uptake (VO2max), cardiac output, and cerebral hemodynamic changes, assessed by Near-Infrared Spectroscopy (NIRS), during a graded maximal exercise tests, and cognitive performance at rest in patients with stable coronary heart disease (CHD) and healthy matched adults. Methods: Ten stable CHD patients (67.1±10.5 years) and 9 age-matched controls (62.2± 11.4 years) were included in this pilot study. Measurements included: body composition (bioelectrical impedance), complete blood analysis in a fasting state, cognitive performance using validated neuropsychological tests, graded maximal exercise testing on ergocycle with gas exchange analysis, non-invasive cardiac output measurement (cardiac bioimpedance) and NIRS signals measurement at the left prefrontal brain level (oxyhaemoglobin: O2Hb, deoxyhaemoglobin: HHb ; total haemoglobin: THb, and differential haemoglogin: Hbdiff). Results: Several cognitive performance items were lower in the CHD group, especially regarding executive functions (Backward digit span score, p&lt;0.05; trail making test B, p=0.05; Stroop test (inhibition/flexibility), p&lt;0.05). There was no difference between CHD and controls in VO2 max (29.7±8.5 Vs 32±6.3 ml/kg/min) and maximal cardiac output (15.5±3.9 Vs 17±2.6 l/min), whereas cardiac output and cardiac index at the ventilatory threshold were lower in CHD (5.75±1 Vs 7.06±0.6 l/min/m2, p&lt;0.05, and 11.2±2.2 Vs 14.1±2.8 l/min, p&lt;0.01, respectively). There was a significant difference in the kinetics of NIRS signal with higher amplitude for CHD patients vs. controls for O2Hb (p&lt;0.01); THb (p&lt;0.05) and Hbdiff (p&lt;0.05). Significant higher amplitude were also found for O2Hb, THb, Hbdiff (p&lt;0.0001) in younger (62 years) participants. HHb (p&lt;0.0001) and Hbdiff (p&lt;0.01) amplitude was higher for fit (≥120% theoretical VO2max) vs. less fit (&lt;120%) participants. Discussion: Compared to age-matched controls, our sample of stable fit CHD patients had a comparable maximal exercise tolerance and cardiac output, with higher NIRS cerebral signals amplitude for O2Hb, THb and Hbdiff. This latter parameter thus does not seem to influence cognitive performance at rest, that was lower in CHD patients, especially in executive functions. However, an important inter-individual variability of cerebral NIRS signal amplitude was observed, with age and fitness appearing as major contributors. We plan to recruit a larger sample of subjects to assess more clearly relationships between exercise, tolerance hemodynamic parameters and cognitive performance.

Noninvasive Cardiac Output Measurement at Rest and During Exercise in Pediatric Patients After Interventional or Surgical Atrial Septal Defect Closure

In the majority of patients, secundum atrial septal defects (ASDs) are treated interventionally or surgically, before the onset of clinical symptoms, between 3 and 6 years of age. Because right-ventricular dimensions usually normalize after ASD closure, it has been assumed that cardiac function and exercise performance also normalize at long-term follow-up. The aim of our study was to determine cardiac index (CI) at rest and during exercise at medium-term follow-up of children who had undergone surgical or interventional closure of ASD because no such reports have been published thus far. Seventeen patients (age range 8.8-17.3 years) who underwent surgical correction were included together with 17 subjects who received an interventional procedure with Amplatzer and Helex occluders (age range 12.2-17.3 years). The study was performed after a median interval of 8.6 years (range 6.5-11.6) after the procedure. Twelve healthy children of comparable age served as controls. CI measurements were performed based on the inert gas-rebreathing method with the Innocor system. For exercise testing, the standard treadmill protocol of the German Society of Pediatric Cardiology was used. CI, stroke volume (SV), and heart rate (HR) were determined at rest and at two standardized submaximal exercise levels (levels 3 and 6). CI increased in all subjects under exercise conditions. Neither SV nor HR displayed significant differences between the three groups either at rest or under exercise conditions. Although HR increased continuously, no increase of indexed SV occurred beyond level 3. Noninvasive determination of CI at rest and during exercise with the IGR method is feasible in the pediatric age group. At medium-term follow-up, we found no significant differences between patients who underwent surgical or interventional ASD closure compared with normal controls.

Continuous non-invasive cardiac output measurements in the neonate by electrical velocimetry: a comparison with echocardiography

ObjectiveElectrical velocimetry (EV) is a non-invasive method of continuous left cardiac output monitoring based on measurement of thoracic electrical bioimpedance. The objective was to validate EV by investigating the agreement...

Comparison of hemodynamic changes between phenylephrine and combined phenylephrine and glycopyrrolate groups after spinal anesthesia for cesarean delivery.

BackgroundHypotension remains a common clinical problem of spinal anesthesia for cesarean delivery and phenylephrine is used as a vasopressor to address this. However, phenylephrine reduces maternal cardiac output (CO) due to reflex bradycardia. Glycopyrrolate is safe for the fetus, and increases heart rate (HR). Using a noninvasive measure of CO, we compared maternal hemodynamic changes between the phenylephrine only group (group P) and the phenylephrine plus glycopyrrolate group (group PG).MethodsIn this randomized study, 60 women scheduled for elective cesarean delivery were allocated to group P (n = 30) or group PG (n = 30). In both groups, phenylephrine was infused at 50 µg/min. This infusions stopped if systolic blood pressure (SBP) was higher than the baseline value, and phenylephrine 100 µg was injected if SBP was lower than 80% of the baseline value from spinal anesthesia to delivery. In group PG, glycopyrrolate 0.2 mg was injected intravenously after spinal anesthesia. Hemodynamic parameters, such as SBP, heart rate (HR), stroke volume index (SVI), cardiac index (CI) were measured before and until 15 min after spinal anesthesia.ResultsThere were no significant differences in SBP and SVI compared to the baseline value in each group and between the two groups. HR and CI reduced significantly from 8 min to 15 min in group P compared to the baseline value as well as group PG for each time-point. However, HR and CI were maintained in group PG.ConclusionsThe use of glycopyrrolate added to phenylephrine infusion to prevent hypotension by spinal anesthesia for cesarean delivery was effective in maintaining HR and CI.

Estimating cardiac output. Utility in the clinical practice. Available invasive and non-invasive monitoring

This aim of this review is to provide a detailed review of the physiologic conditions and variables of the cardiac output, as well as review the different techniques available for its measurement. We also want to establish the clinical situations in which the measurement of cardiac output can add valuable information for the management of critically ill patients. The Fick technique, used in the beginning to calculate cardiac output, has been replaced today by thermodilution techniques (transcardiac or transpulmonary), lithium dilution, bioreactance, Doppler technique or echocardiography. Pulse wave analysis allows a continuous minimally invasive cardiac output measurement. Other methods, such as bioreactance, Doppler technique or echocardiography currently provide a valid, fast and non-invasive measurement of cardiac output.

Abstract 196: Measurement of Depth, Thrust and Thoracic Impedance During Mechanical Cardiopulmonary Resuscitation: Is Thoracic Impedance a Potential Indicator of Effective External Cardiac Massage in a Porcine Model of Cardiac Arrest?

Purpose of the Study: The 2010 AHA guidelines currently recommend a depth of at least 2 inches (5cm) during external cardiac massage. The purpose of this study was to determine if the use of an alternative measure to depth could assist in quantifying the effectiveness of CPR in an out-of-hospital setting and to determine how achievable depths of at least 2 inches are in experimental models of cardiac arrest. Materials and Methods: A total of 12 porcine models were used each weighing 30.7±4.2kg. Depth (mm), thrust (kg); End-tidal CO 2 , and Cardiac Output (CO) were measured at 2 minute intervals for each model. The Impedance Cardiogram (ICG)/Thoracic Impedance (non-invasive measure of cardiac output) was recorded via 2 standard defibrillation electrodes, as a method of detecting the presence of effective CPR. Ethical approval was granted by the Northern Ireland Home Office. Models were anaesthetised using Isoflurane and connected to a Datex Ohmeda® for anaesthesia monitoring. Depth and rate of CPR were continuously measured using Q-CPR®, Philips. CPR was administered using the HLR-201®, Michigan Instruments. Recordings from each experiment were acquired using the Datex Ohmeda for statistical analysis using Microsoft Access®. Results: During CPR, cardiac output was maintained at an average of 21% of normal CO levels. At thrusts of 60kg and a rate 112±2 compressions per minute, the average depth (using Q-CPR®, Philips) achieved using a stabilised mechanical CPR system was 37.12mm±3 (1.46±0.12inches). Using the HLR-201®, Michigan Instruments the average depth achieved was 50mm (1.97inches). A strong linear correlation was achieved when comparing depth (mm) using Q-CPR® and the thrust (kg) using the HLR-201®, Michigan Instruments; r=0.856. In addition a strong linear correlation was attained when the Impedance cardiogram (ICG) (ohms) was compared with depth (mm) using Q-CPR®, Philips of; r=0.86. Conclusions: A depth of at least 2 inches was almost unattainable in this porcine model, even at thrusts of 60 kg. An algorithm will incorporate the results from this study, providing feedback to the operator on the quality of CPR by measuring the ICG amplitude which has been strongly correlated with standard measures of depth as well as a number of physiological parameters.

Long-term lifestyle intervention and optimized high intensity interval training program improve body composition, cardiovascular risk and exercise capacity in obese patients with or without metabolic syndrome

bjectives.– To evaluate the feasibility at rest with reproducibility of the ntra-operator and inter-operator measurement of CO and to compare with easurements obtained by transthoracic echocardiography (TTE). To estimate he feasibility during effort and during the recovery effort. To determine the iagnostic, therapeutic and prospective implication. ethods.– Observational study based on 142 consecutive outpatients included rom cardiac rehabilitation (CHU Dijon). IGR was performed before and/or uring and/or after the cardiac stress test by photoacoustic analysis using two nert gases: 0.5% nitrous oxide and 0.1% sulfur hexafluoride (indirect oxyen Fick Method Innocor®). Statistical analysis based on correlation analysis, land and Altman, and standardization. esults.– At rest, the correlation coefficient was 0.91 (P< 0.001) between two O in intra-operator in 26 patients, 0.89 (P< 0.001) between two CO in interperator in 30 patients, 0.38 (P= 0.039) between the CO measured by IGR and TE in 30 patients. Using the method of Bland and Altman, the range of variation f repeatability was respectively± 27%, ± 33%± 42%. During the effort in 45 atients, formulas of standardization were used to assess components: stroke olume (SV) and heart rate (HR). Two populations were isolated: preferential ncrease in SV or HR. onclusion.– At rest, feasibility, repeatability and reproducibility of the meaurements are correct (despite the dispersion related to measurement of CO). t submaximal exercise, feasibility is good. The measurement to quantify the emodynamic changes during rehabilitation is valid and applicable in various athological conditions (heart failure in high CO at rest, etc), and could help to dapt the use of chronotopic drug. eferences 1] Goda A et al. Usefulness of non-invasive measurement of cardiac output uring sub-maximal exercise to predict outcome in patients with chronic heart ailure. AM J Cardiol 2009; 104(Suppl. 11):1556–60. 2] Follath F. Challenging the dogma of high target doses in the treatment of eart failure: is more always better? Arch Cardiovasc Dis 2009;102:785–9.

Cardiac Resynchronization Therapy Optimization Using Noninvasive Cardiac Output Measurement

Noninvasive cardiac output (CO) measurement (NICOM) is a novel method to assess ventricular function and offers a potential alternative for optimization of cardiac resynchronization therapy (CRT) devices. We compared the effect of NICOM-based optimization to no optimization (empiric settings) on CRT outcomes. Two hundred and three patients undergoing CRT were assessed in two consecutive nonrandomized groups; an empiric group (n = 54) was programmed to "out of the box" settings with a fixed AV delay of 120 ms and a VV delay of 0 ms; and the optimization group (n = 149) underwent adjustments of both the AV and VV delays according to the greatest improvement in resting CO. The primary endpoints were improvements in left ventricular (LV) volumes and function from baseline at 6 months. Secondary endpoints were change in New York Heart Association (NYHA) class, quality of life score, and 6-minute walk test (6 MWT) performance. After 6 months of CRT, the optimization group had a better clinical response with lower NYHA class (2.1 ± 0.8 vs 2.4 ± 0.8, P = 0.048) and quality of life scores (35 ± 18 vs 42 ± 20, P = 0.045) but no differences in 6-MWT performance (269 ± 110 vs 277 ± 114 m, P = 0.81). Echocardiographic response was also better in the optimization group with lower LV end systolic volume (108 ± 51 vs 126 ± 60 mL, P = 0.048) and higher ejection fraction (30 ± 7 vs 27 ± 8, P = 0.01) compared to empiric settings. Device optimization using noninvasive measures of CO is associated with better clinical and echocardiographic response compared to empiric settings.

A comparative evaluation of electrical velocimetry and inert gas rebreathing for the non-invasive assessment of cardiac output

When assessing the function of the cardiovascular system, cardiac output (CO) is a substantial parameter. For its determination, numerous non-invasive techniques have been proposed in the recent years including inert gas rebreathing (IGR) and impedance cardiography (ICG). The aim of our study was to evaluate whether a novel ICG algorithm (electrical velocimetry) and IGR can be used interchangeably in the clinical setting. A total of 120 consecutive stable patients were included resulting in two pairs of repeated non-invasive cardiac output measurements. The mean CO was 5.0±1.2l/min (range 2.6-8.6l/min) using IGR and 4.4±1.1l/min (1.7-7.4l/min) using ICG, respectively. Bland-Altman analysis revealed an acceptable agreement with a mean bias of 0.6±1.2l/min. We found a high reproducibility with a mean bias of 0.2±0.7l/min for IGR and 0.0±0.3l/min for ICG (p<0.001), respectively. There was a statistically significant difference for unphysiological circulatory conditions represented by values of 2.6-4.1l/min and 5.6-8.6l/min. Both non-invasive techniques are associated with low operating costs and require only a few expendable items for the rapid determination of cardiac function. We found an acceptable agreement between IGR and ICG as well as a high reproducibility, which was statistically significant higher for ICG. For cardiac output states exceeding the physiological range, we found a statistically significant difference. Consequently, values of cardiac function determined by either method should not be used interchangeably in the clinical setting.

Noninvasive measurement of cardiac output by uncalibrated finger arterial waveform analysis

s and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: Monitoring: Equipment and Computers

86 How often is important adjustment of pacing intervals required for optimal response following CRT?

Introduction A significant minority of patients do not experience clinical benefit following cardiac resynchronisation therapy (CRT). Haemodynamically-guided adjustment of the intervals between chambers paced (“optimisation” of atrio-ventricular (AV) and left-right ventricular (VV) delays) may be undertaken to improve the chance of response to CRT. However, data to support this approach as standard management are lacking and many institutions programme CRT devices to deliver “out-of-the-box” intervals, only undertaking optimisation when clinical response is lacking. We sought to determine how often the “out-of-the-box” settings are optimal or acceptable and how often CRT optimisation results in significant alteration of the pre-programmed pacing intervals. Methods Data were collected from 180 consecutive patients who underwent CRT followed by optimisation within 24 h. Optimisation was performed with serial adjustment of AV and VV intervals. Haemodynamic assessment was undertaken using either echocardiography or Non-Invasive Cardiac Output Measurement. The optimal pacing intervals were considered to be those which resulted in greatest acute augmentation of cardiac output and the device was programmed accordingly. The final settings were compared with the pre-programmed settings for that device and the difference (AV or VV Adjustment) derived, taking into account the preset paced or sensed AV delay. An AV or VV Adjustment of more than 40 ms was considered to be clinically significant. Data are presented as mean (SD). Results Optimal AV delay ranged from 60 to 200 ms (mean 124 ms (30)), VV delay ranged from 0 to 100 ms (mean 23 ms (19)). With the pre-set pacing parameters, cardiac output was acutely augmented by 13.1 (34)%. Optimised CRT produced further improvement of cardiac output, to 24.9 (32)% augmentation. “Out-of-the-box” settings were found to be optimal in 11 (6.1%), or requiring only minor alteration in 120 (66.7%). A clinically significant alteration in AV delay was made in 40 (22.2%), in VV delay in 12 (6.7%) or in either parameter in 49 (27.2%). Conclusions Significant adjustment of AV or VV delay is required in over a quarter of patients receiving CRT. Optimisation of pacing intervals provides augmentation of cardiac output over and above the “out-of-the-box” settings. The findings suggest that optimisation is an important component of resynchronisation therapy.

Quantitative assessment of cardiac output and left ventricular function by noninvasive phase‐contrast and cine MRI: Validation study with invasive pressure‐volume loop analysis in a swine model

To validate noninvasive cardiac output measurements of phase-contrast magnetic resonance imaging (PC-MRI) and cine MRI using an invasive pressure-volume (PV) loop technique on a swine model. We compared three methods for evaluating cardiac function at rest and under pharmaceutical low-dose inotropic infusion conditions: 1) phase-contrast MRI, 2) cine MRI, and 3) PV loop relationship. These measurements were made in 14 domestic pigs under rest conditions. Identical MRI acquisitions and PV loop analysis were performed on six pigs from the same group that received an infusion of dobutamine 2.5 μg/kg/min. Cardiac outputs from all measurements were analyzed and compared using linear regression and Bland-Altman analysis. Noninvasive PC-MRI and cine MRI did not show any significant differences compared to an invasive PV loop technique for measurement of cardiac output under both rest (PC-MRI, cine MRI, and PV loop, 3.17 ± 0.45, 3.18 ± 0.61, 3.45 ± 0.41 L/min, respectively) and pharmaceutical low-dose inotropic infusion conditions (PC-MRI, cine MRI, and PV loop, 4.78 ± 0.53, 4.7 ± 0.6, 4.96 ± 0.48 L/min, respectively). Statistical analysis showed good agreement of cardiac output measurements at rest (R(2) = 0.83) and under low-dose inotropic infusion conditions (R(2) = 0.74) using PC-MRI and PV loop techniques. Cardiac output measurement using cine MRI and PV loop techniques also showed good agreement at rest (R(2) = 0.85) and under low-dose inotropic infusion conditions (R(2) = 0.76). Furthermore, cardiac outputs determined with the three modalities showed good agreement over a wide range of heart rates (90-180 bpm). MRI can provide a reliable, noninvasive measurement of cardiac output that can be carried out without the complications that are inherent with current invasive procedures.

ACUTE NON-INVASIVE CARDIAC OUTPUT MEASUREMENTS FOLLOWING CARDIAC RESYNCHRONIZATION THERAPY PREDICT LEFT VENTRICULAR REVERSE REMODELING AT 6 MONTHS AND LONG TERM SURVIVAL

Abstract Category: 28. Cardiac PacingSession-Poster Board Number: 1089-397Authors: Fakhar Z. Khan, Munmohan S. Virdee, David Begley, John Hutchinson, Beverley Smith, Philip A. Read, Peter J. Pugh, Simon P. Fynn, David P. Dutka, Addenbrooke’s Hospital, Cambridge, United Kingdom, Papworth Hospital, Cambridge, United Kingdom Background: We aimed to assess to what extent acute changes in non invasive cardiac output measurements (NICOM) are related to longer term outcomes following cardiac resynchronization therapy (CRT).Methods: In 196 patients (69±9yrs, EF 23±7%, QRS 154±12ms, NYHA III/IV 183/13) CO recordings were made within 1 day of CRT at baseline (CRT OFF) and during optimized settings (CRT ON). Response was defined by >15% reduction in left ventricular end systolic volume (LVESV) at 6 months.Results: There was a significant difference in CO readings during CRT between responders (n=112) and non responders (6.23±1.21 vs 5.19±0.96L/min, p 20% in CO, 1 day after CRT implant had greater survival than those patients with <20% improvement (figure).Conclusions: NICOM recordings following CRT accurately predict LV reverse remodeling and long term survival. This validation study suggests potential use in either the optimization of CRT devices or in the guidance of LV lead placement.

Non-invasive cardiac output and oxygen delivery measurement in an infant with critical anemia

To assess the combination of a non-invasive blood oxygen content (CaO(2)) monitor and a non-invasive cardiac output (CO) monitor to continuously measure oxygen delivery (DO(2); DO(2) = CaO(2) × CO). DO(2) was assessed during blood transfusions in an infant with acute hemolytic anemia following admission (~48 h). CaO(2) was measured by Pulse Co-Oximetry, which also provides estimates of hemoglobin (Hgb) concentration and percent oxygen saturation. CO was measured by Electrical Velocimetry, which also provides an estimate of stroke volume (SV). Lactate levels, an indirect measure of adequate DO(2), were assessed during the initial 8 h following admission. Incremental blood transfusions during the first 36 h increased Hgb from 2.7 to 9.5 g/dL during which time heart rate (HR) normalized from 156 to 115 beats/min. Lactate levels decreased from 20 to 0.8 mmol/L in the first 7 h. Non-invasive Hgb and CaO(2) measurements were well correlated with invasive Hgb and CaO(2) measures (r (2) = 0.88; P = 0.019; r (2) = 0.86; P = 0.0074, respectively). CO decreased from 2.47 ± 0.06 to 1.28 ± 0.02 L/min and SV decreased from 15.9 ± 0.4 to 11.1 ± 0.2 mL/beat. Mean arterial blood pressure was stable throughout the admission with systemic vascular resistance increasing from 407.6 ± 15.2 to 887.7 ± 30.1 dynes-s/cm(5). DO(2) was estimated to increase from 120.2 ± 18.9 to 182.4 ± 5.6 mL O(2)/min. Non-invasive continuous CO and CaO(2) monitors are shown in this single case to provide continuous DO(2) measurement. The ability to assess DO(2) may improve hemodynamic monitoring during goal directed therapies.

Noninvasive cardiac output monitoring with bioreactance as an alternative to invasive instrumentation for preclinical drug evaluation in beagles

Introduction Non-invasive measurement of cardiac output (CO) using bioreactance signals (NICOM) was recently validated in swine and human adults. The present study was designed to test the hypothesis that NICOM flow measurements can accurately measure CO and detect acute drug-induced changes in aortic blood flow (AoQ) ≥ 10% in beagles. Methods Data from 5 anesthetized, open chest beagles used for preclinical screening of novel neuromuscular blocking drugs were analyzed for the study. AoQ was measured beat-to-beat with a probe on the aortic root and averaged over 30 s intervals. NICOM CO measurements were simultaneously obtained every 30 s. NICOM precision (random variation) and accuracy relative to AoQ were assessed from individual segments of steady-state data. The ability of NICOM to detect acute alterations in AoQ ≥ 10% was determined from other segments with dynamic change. Results 516 simultaneous CO measurements between 826 and 2436 mL/min were analyzed. Steady-state measurements (20% of the dataset) revealed an average AoQ − NICOM difference (bias) of 63 ± 38 mL/min, a percent error of 6.1%, and a NICOM precision of 6.1%. Within the acute change dataset, 21/23 events reflecting a ≥ 10% change in beat-to-beat AoQ were detected by the NICOM (sensitivity of 0.91). In none of 10 instances where drug or fluid injection altered AoQ < 10% did the NICOM indicate a change (specificity of 1.0). Discussion Continuous, non-invasive measurement of CO by bioreactance provides data that satisfactorily approximates invasive measurement of aortic blood flow in beagles. In addition, despite a 30 s interval between measurements, the NICOM appears to have sufficient fidelity to detect and quantify acute, drug-induced changes in CO. These data suggest that the NICOM may represent an alternative to open chest instrumentation for CO measurement in preclinical drug evaluation studies.

Non-invasive measurements of cardiac output in atrial fibrillation: Inert gas rebreathing and impedance cardiography

Background. Atrial fibrillation (AF) is associated with significant morbidity and mortality. To test the effect of interventions, knowledge of cardiac output (CO) is important. However, the irregular heart rate might cause some methods for determination of CO to have inherent weaknesses. Objective. To assess the validity of these methods in AF, a new inert gas rebreathing device and impedance cardiography was tested with echocardiography as reference. Methods. Using a cross-sectional design, 127 patients with AF and 24 in SR were consecutively recruited. Resting CO was measured using inert gas rebreathing (n = 62) or impedance measurement of intrathoracic blood flow (n = 89) in separate studies with echocardiographic measurement as reference. Results. CO determined with impedance cardiography was mean 4.77 L/min ± 2.24(SD) compared to 4.93 L/min ± 1.17 by echocardiography (n = 89, n.s.) in patients with AF. CO by inert gas rebreathing was 4.98 L/min ± 2.49(SD) compared to 5.70 L/min ± 2.49 by echocardiography (n = 62, n.s.) in patients with AF and SR (AF 5.42 ± 2.9 vs. 6.27, n.s. and SR 4.09 ± 1.08 vs. 4.35 ± 0.86, n.s.). Mean bias between impedance cardiography and echocardiography was 0.14 ± 0.95 L/min and −0.13 ± 0.98 L/min between inert gas rebreathing and echocardiography. Inert gas rebreathing showed larger intra-patient variation than impedance cardiography (0.11 vs. 0.054). Correlation between inert gas rebreathing and echocardiography was r = −0.060 and between impedance cardiography and echocardiography was r = 0.128. Impedance cardiography and inert gas rebreathing both underestimated CO compared to echocardiography. Conclusion. Variation between the inert gas rebreathing and the reference method for AF patients was less than desired. Impedance cardiography was superior to inert gas rebreathing and showed acceptable agreement with echocardiography and variability similar to echocardiography.

Validation of Noninvasive Measurements of Cardiac Output in Mice Using Echocardiography

Although multiple echocardiographic methods exist to calculate cardiac output (CO), they have not been validated in mice using a reference method. Echocardiographic and flow probe measurements of CO were obtained in mice before and after albumin infusion and inferior vena cava occlusions. Echocardiography was also performed before and after endotoxin injection. Cardiac output was calculated using left ventricular volumes obtained from an M-mode or a two-dimensional view, left ventricular stroke volume calculated using the pulmonary flow, or estimated by the measurement of pulmonary velocity time integral (VTI). Close correlations were demonstrated between flow probe-measured CO and all echocardiographic measurements of CO. All echocardiographic-derived CO overestimated the flow probe-measured CO. Two-dimensional image-derived CO was associated with the smallest overestimation of CO. Interobserver variability was lowest for pulmonary VTI-derived CO. In mice, CO calculated from two-dimensional parasternal long-axis images is most accurate when compared with flow probe measurements; however, pulmonary VTI-derived CO is subject to less variability.