Validation of a new arterial pulse contour-based cardiac output device

OBJECTIVE: To evaluate the accuracy and precision of an arterial pulse contour-based continuous cardiac output device (Vigileo). Vigileo cardiac output (VigileoCO) was compared with intermittent transpulmonary thermodilution cardiac output (TPCO) and an established arterial pulse contour-based cardiac output (PCCO). DESIGN: Prospective clinical study. SETTING: University hospital. PATIENTS: Twenty-two patients undergoing coronary artery bypass graft surgery. INTERVENTIONS: Defined volume load during surgery and in the postoperative period. MEASUREMENTS AND MAIN RESULTS: We obtained 184 pairs of VigileoCO and TPCO, 140 pairs of VigileoCO and PCCO, and 140 pairs of PCCO and TPCO. Measurements were performed after induction of anesthesia (T1), after sternotomy (T2), immediately after (T3) and 20 mins after volume challenge with 10 mL.kg hydroxyethyl starch 6% (T4), 15 mins after coronary pulmonary bypass (T5), after retransfusion of autologous blood (T6), after arrival at the intensive care unit (T7), and immediately after (T8) and 20 mins after (T9) a second volume load with 10 mL.kg hydroxyethyl starch 6%. TPCO was used to calibrate PCCO. For pooled data, including uncalibrated PCCO data immediately after weaning from coronary pulmonary bypass (T5), the correlation coefficient of TPCO vs. VigileoCO, PCCO vs. VigileoCO, and TPCO vs. PCCO was 0.75, 0.60, and 0.75 respectively. Bland-Altman analysis showed a bias of 0.00, -0.01, and 0.02 L.min, the precision (=sd) was 0.87, 1.08, and 0.93 L.min, and the mean error was 33%, 40%, and 35%. When we compared calibrated PCCO values (T2-T4, T6, T7-9), the correlation coefficients of PCCO-VigileoCO and TPCO-PCCO were 0.72 and 0.85, bias was -0.16 and 0.19 L.min, and mean error was 33% and 27%, respectively. Best correlations and the least differences between TPCO and VigileoCO were observed in postbypass closed-chest conditions and in the intensive care unit. CONCLUSIONS: Our results showed that VigileoCO enables clinically acceptable assessment of cardiac output in postbypass closed-chest conditions and during stable conditions in the intensive care unit.     

Estimated continuous cardiac output based on pulse wave transit time in off-pump coronary artery bypass grafting: a comparison with transpulmonary thermodilution

To evaluate the accuracy of estimated continuous cardiac output (esCCO) based on pulse wave transit time in comparison with cardiac output (CO) assessed by transpulmonary thermodilution (TPTD) in off-pump coronary artery bypass grafting (OPCAB). We calibrated the esCCO system with non-invasive (Part 1) and invasive (Part 2) blood pressure and compared with TPTD measurements. We performed parallel measurements of CO with both techniques and assessed the accuracy and precision of individual CO values and agreement of trends of changes perioperatively (Part 1) and postoperatively (Part 2). A Bland–Altman analysis revealed a bias between non-invasive esCCO and TPTD of 0.9 L/min and limits of agreement of ±2.8 L/min. Intraoperative bias was 1.2 L/min with limits of agreement of ±2.9 L/min and percentage error (PE) of 64 %. Postoperatively, bias was 0.4 L/min, limits of agreement of ±2.3 L/min and PE of 41 %. A Bland–Altman analysis of invasive esCCO and TPTD after OPCAB found bias of 0.3 L/min with limits of agreement of ±2.1 L/min and PE of 40 %. A 4-quadrant plot analysis of non-invasive esCCO versus TPTD revealed overall, intraoperative and postoperative concordance rate of 76, 65, and 89 %, respectively. The analysis of trending ability of invasive esCCO after OPCAB revealed concordance rate of 73 %. During OPCAB, esCCO demonstrated poor accuracy, precision and trending ability compared to TPTD. Postoperatively, non-invasive esCCO showed better agreement with TPTD. However, invasive calibration of esCCO did not improve the accuracy and precision and the trending ability of method.     

Validation of a device to measure arterial pulse wave velocity by a photoplethysmographic method

We aimed to validate a new method for measuring arterial pulsewave transit time and pulsewave velocity (a measure of arterial elasticity), based on the principle of photoplethysmography (PPG), and to compare transcutaneous values with those obtained by intra-arterial measurements. Three validation experiments are described. (a) PPG pulse wave delay times (defined as the time interval between the ECG R wave and the foot of the arterial pulse wave measured at the wrist or ankle) were compared to values obtained simultaneously from an established methodology (Doppler ultrasound). (b) Aortic pulsewave delay times in 17 subjects obtained non-invasively by the PPG method were compared with those obtained from the intra-arterial pressure wave. (c) Repeatability measurements of PWV on the same subjects were carried out over two timescales (minutes and hours) in the arm, the leg and the trunk. The Doppler and PPG delay times correlated well, as did intra-arterial and transcutaneous values. Repeatability at short timescales was good (coefficients of variation (CV) < 6% for all measurement sites) and, at the longer timescale, was satisfactory (CVs in the aorta, the arm and leg were 6.3, 13.1 and 16.0, respectively). The PWV values agreed well with others in the literature. We conclude that the PPG technique provides a complement to existing methods for the non-invasive measurement of arterial compliance. Its simplicity and ease of use make it suitable for large-scale epidemiological studies.     

The ability of a new continuous cardiac output monitor to measure trends in cardiac output following implementation of a patient information calibration and an automated exclusion algorithm

A new non-invasive continuous cardiac output (esCCO) monitoring system solely utilizing a routine cardiovascular monitor was developed, even though a reference cardiac output (CO) is consistently required. Subsequently, a non-invasive patient information CO calibration together with a new automated exclusion algorithm was implemented in the esCCO system. We evaluated the accuracy and trending ability of the new esCCO system. Either operative or postoperative data of a multicenter study in Japan for evaluation of the accuracy of the original version of esCCO system were used to develop the new esCCO system. A total of 207 patients, mostly cardiac surgical patients, were enrolled in the study. Data were manually reviewed to formulate a new automated exclusion algorithm with enhanced accuracy. Then, a new esCCO system based on a patient information calibration together with the automated exclusion algorithm was developed. CO measured with a new esCCO system was compared with the corresponding intermittent bolus thermodilution CO (ICO) utilizing statistical methods including polar plots analysis. A total of 465 sets of CO data obtained using the new esCCO system were evaluated. The difference in the CO value between the new esCCO and ICO was 0.34?±?1.50 (SD) L/min (95?% confidence limits of ?2.60 to 3.28?L/min). The percentage error was 69.6?%. Polar plots analysis showed that the mean polar angle was ?1.6° and radial limits of agreement were ±53.3°. This study demonstrates that the patient information calibration is clinically useful as ICO, but trending ability of the new esCCO system is not clinically acceptable as judged by percentage error and polar plots analysis, even though it’s trending ability is comparable with currently available arterial waveform analysis methods.     

Impact of changes in systemic vascular resistance on a novel non-invasive continuous cardiac output measurement system based on pulse wave transit time: a report of two cases

The inaccuracy of arterial waveform analysis for measuring continuos cardiac output (CCO) associated with changes in systemic vascular resistance (SVR) has been well documented. A new non-invasive continuous cardiac output monitoring system (esCCO) mainly utilizing pulse wave transit time (PWTT) in place of arterial waveform analysis has been developed. However, the trending ability of esCCO to measure cardiac output during changes in SVR remains unclear. After a previous multicenter study on esCCO measurement, we retrospectively identified two cases in which apparent changes in SVR developed in a short period during data collection. In each case, the trending ability of esCCO to measure cardiac output and time component of PWTT were analyzed. Recorded data suggest that the time component of PWTT may have a significant impact on the accuracy of estimating stroke volume during changes in SVR. However, further prospective clinical studies are required to test this hypothesis.     

Lithium dilution measurement of cardiac output and arterial pulse waveform analysis: an indicator dilution calibrated beat-by-beat system for continuous estimation of cardiac output

Lithium dilution cardiac output (LiDCO trade mark; LiDCO, London, UK) is a minimally invasive indicator dilution technique for the measurement of cardiac output. It was primarily developed as a simple calibration for the PulseCO trade mark (LiDCO, London, UK) continuous arterial waveform analysis monitor. The technique is quick and simple, requiring only an arterial line and central or peripheral venous access. These lines would probably already have been inserted in critical care patients. A small dose of lithium chloride is injected as an intravenous bolus, and cardiac output is derived from the dilution curve generated by a lithium-sensitive electrode attached to the arterial line. Studies in humans and animals have shown good agreement compared with results obtained with other techniques, and the efficacy of LiDCO trade mark in pediatric patients has also been proven. Compared with thermodilution, lithium dilution showed closer agreement in clinical studies with electromagnetic flow measurement.PulseCO trade mark is a beat-to-beat cardiac output monitor that calculates stroke volume from the arterial pressure waveform using an autocorrelation algorithm. The algorithm is not dependent on waveform morphology, but, rather, it calculates nominal stroke volume from a pressure-volume transform of the entire waveform. The nominal stroke volume is converted to actual stroke volume by calibration of the algorithm with LiDCO trade mark. Initial studies indicate good fidelity, and the results from centers in the United States and the United Kingdom are extremely encouraging. The PulseCO trade mark monitor incorporates software for interpretation of the hemodynamic data generated and provides a real-time analysis of arterial pressure variations (ie, stroke volume variation, pulse pressure variation, and systolic pressure variation) as theoretical guides to intravascular and cardiac filling.     

The difference in pulse transit time to the toe and finger measured by photoplethysmography

Blood pressure pulse wave velocity (PWV) is a parameter which is related to arterial distensibility. Its direct assessment, by measuring the appearance time of a pressure pulse in two sites along an artery and the distance between the two sites, is complicated and inaccurate. In the current study, pulse transit time (PTT) to the toes and fingers of 44 normotensive male subjects was measured by photoplethysmography (PPG) and ECG. The arrival time of the pulses at the toe and finger was determined from the foot of the systolic rise of the PPG signal, i.e. at end-diastolic time. Two parameters, which are related to PWV, were tested: the time delay between the ECG R-wave and the arrival time of the pulses at the toe (E-T PTT), and the difference in the transit time of the blood pressure pulses between the toe and finger (T-F PTTD). E-T PTT and T-F PTTD decreased as functions of the subject's age and systolic blood pressure (SBP), but their dependence on the diastolic blood pressure (DBP) was not statistically significant. The decrease of the PTT parameters with age is attributed to the direct structural decrease of the arterial compliance with age and not to functional effects associated with the increase of the blood pressure with age, since the PTT parameters did not depend on DBP though the measurements were performed at end-diastole.     

Assessment of the accuracy of continuous cardiac output and pulse contour cardiac output in tracking cardiac index changes induced by volume load.

OBJECTIVE: To assess the ability to track changes in cardiac index (DeltaCI) induced by volume loading using continuous pulsed heat thermodilution (CCO), and pulse contour (PCCO) cardiac output (CO) with transpulmonary thermodilution (TD(tp)) CO as reference. DESIGN: Prospective observational clinical trial. SETTING: Intensive care unit. PATIENTS: Twelve ventilated and sedated post-operative cardiac surgery patients. MEASUREMENTS AND RESULTS: Each patient had a 7.5F CCO pulmonary artery catheter (Edwards Lifesciences) and a 5F, 20cm PCCO femoral artery catheter (Pulsion Medical Systems). Forty-five data sets were taken before and after 25 volume loadings of 5mL/kg of 4% albumin. Volume loading resulted in an increase in CI (2.84L/(minm(2)) versus 3.12L/(minm(2)), p<.05) although only nine volume loadings changed CI (DeltaCI)>/=14%. The change in CI using PCCO (DeltaPCCI) was correlated with DeltaCI (TD(tp)) (R(2)=.50, p<.0001), whilst DeltaCI using CCO (DeltaCCI) was not (R(2)=.14). The bias and limits of agreement (LOA) between DeltaTD(tp)CI and DeltaPCCI was 6.2% (95% CI, +/-5.8%) and 28.4% (95% CI, +/-38.2%) respectively. DeltaTD(tp)CI and DeltaCCI has a bias of 2.6% (95% CI, +/-8.3%) and LOA of 39.6% (95% CI, +/-63%). Both DeltaPCCI and DeltaCCI reliably tracked DeltaCI>/=14%. CONCLUSION: In this small group of patients the continuous cardiac output methods tracked changes in CI, although, in individual cases they did not change in the same direction as the thermodilution method. Critical care nurses need to critically appraise the accuracy and clinical relevance of continuous CO data within the clinical context.     

Response time of the Opti-Q continuous cardiac output pulmonary artery catheter in the urgent mode to a step change in cardiac output

Objectives.This study was conducted to determine the response timeof the Opti-Q continuous cardiac output (CCO) device to a step change incardiac. Design.Prospective study. Setting.University hospitalanimal lab. Model.Female sheep. Interventions.In ten animals,cardiac output was altered suddenly by opening and closing a peripheralarteriovenous shunt to test the response time of the CCO system.Measurements and main results.Cardiac output was measured continuouslyby thermodilution and ultrasonic techniques while an arteriovenous shunt wasopened and closed. A total of 53 dynamic observations were made (5–6 peranimal). The mean response time of the continuous cardiac output device was86 seconds and was unaffected by the magnitude or direction of the change incardiac output. It was also unaffected by the animal's weight. CCOvalues were not statistically different from standard thermodilutionmeasurement (p= 0.895). Shunt flow ranged from 430 to 1730 ml/minand averaged 812 ml/min. The mean CCO with the shunt closed was 4.62 L/min.There was 1.5 to 2 minutes under or overshoot in cardiac output in 11% of themeasurements. Conclusions.Continuous cardiac output measurement wasas accurate as those made by standard bolus thermodilution. The averageresponse time to acute changes in cardiac output was approximately 1.5 minutesor ten times faster than previously reported systems. Response time isindependent of animal mass, shunt volume and the direction of cardiac outputperturbations.     

Clinical evaluation compared to the pulse indicator continuous cardiac output system in the hemodynamic assessment of critically ill patients

Objective

The objective was to assess the effects of pulse indicator continuous cardiac output catheterization on the management of critically ill patients and the alteration of therapy in intensive care units.

Methods

One hundred thirty-two patients with primary physiological abnormalities of hypotension or hypoxemia were evaluated. Prior to catheterization, physicians were asked to complete a questionnaire that collected information regarding predictions of the ranges of several hemodynamic variables and plans for therapy. After catheterization, each chart was reviewed by a panel of intensive care attending physicians to determine the possibility of altering the therapy.

Results

Overall correct classification of the key variables ranged from 46.0% to 65.4%. Catheterization results prompted alterations in therapy for 45.5% of patients. The fellows were less accurate in predicting hemodynamic values for patients whose diagnoses were unknown, and the primary abnormality was hypotension. There was significant difference in the physicians’ abilities to predict the hemodynamics for the subgroups with and without acute myocardial infarction. When the patients were divided into 3 subgroups by Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment scores, the fellows had the most difficulty predicting the variables of the moderately ill patients in the middle subgroup, which led to the greatest percentage of therapy alterations for this subgroup; and this difference was significant.

Conclusions

The hemodynamic variables obtained from pulse indicator continuous cardiac output catheterization improved the accuracy of bedside evaluations and led to alterations in therapeutic plans, particularly among the moderately ill patients with hypotension or unknown diagnoses.     

Evaluation of the estimated continuous cardiac output monitoring system in adults and children undergoing kidney transplant surgery: a pilot study

Evaluation of the estimated continuous cardiac output (esCCO) allows non-invasive and continuous assessment of cardiac output. However, the applicability of this approach in children has not been assessed thus far. We compared the correlation coefficient, bias, standard deviation (SD), and the lower and upper 95 % limits of agreement for esCCO and dye densitography-cardiac output (DDG-CO) measurements by pulse dye densitometry (PDD) in adults and children. On the basis of these assessments, we aimed to examine whether esCCO can be used in pediatric patients. DDG-CO was measured by pulse dye densitometry (PDD) using indocyanine green. Modified-pulse wave transit time, obtained using pulse oximetry and electrocardiography, was used to measure esCCO. Correlations between DDG-CO and esCCO in adults and children were analyzed using regression analysis with the least squares method. Differences between the two correlation coefficients were statistically analyzed using a correlation coefficient test. Bland–Altman plots were used to evaluate bias and SD for DDG-CO and esCCO in both adults and children, and 95 % limits of agreement (bias ± 1.96 SD) and percentage error (1.96 SD/mean DDG-CO) were calculated and compared. The average age of the adult patients (n = 10) was 39.3 ± 12.1 years, while the average age of the pediatric patients (n = 7) was 9.4 ± 3.1 years (p < 0.001). For adults, the correlation coefficient was 0.756; bias, ?0.258 L/min; SD, 1.583 L/min; lower and upper 95 % limits of agreement for DDG-CO and esCCO, ?3.360 and 2.844 L/min, respectively; and percentage error, 42.7 %. For children, the corresponding values were 0.904; ?0.270; 0.908; ?2.051 and 1.510 L/min, respectively; and 35.7 %. Due to the high percentage error values, we could not establish a correlation between esCCO and DDG-CO. However, the 95 % limits of agreement and percentage error were better in children than in adults. Due to the high percentage error, we could not confirm a correlation between esCCO and DDG-CO. However, the agreement between esCCO and DDG-CO seems to be higher in children than in adults. These results suggest that esCCO can also be used in children. Future studies with bigger study populations will be required to further investigate these conclusions.     

Comparison of four different Doppler instruments used to measure linear and volumetric cardiac output: a study of reproducibility and agreement

Values of stroke distance obtained from 25 subjects with the obsolete Transcutaneous Aortovelograph were compared with those from two commercially available Doppler ultrasound devices, the Doptek Decoder, and the Doppler unit of the Interspec-XL Ultrasound System. Also studied was the Quantascope, an ultrasound device designed to measure stroke volume. In the aortic arch, reproducibility was 4.8% with the Transcutaneous Aortovelograph, 9.1% with the Doptek Decoder, 17.2% with the Interspec, and 23.6% with the Quantascope. In the ascending aorta, reproducibility was worse, being 13.4% for the Doptek, 23.0% for the Interspec, and 28.1% for the Quantascope. There was close agreement between the absolute values of stroke distance obtained with the Transcutaneous Aortovelograph and the Interspec, but lower values were obtained by the Doptek Decoder. There is a need for an updated instrument dedicated to the measurement of stroke distance in the aortic arch.     

The influence of time on the accuracy of healthcare personnel to diagnose paediatric cardiac arrest by pulse palpation

Aim

To determine time and accuracy diagnosing paediatric cardiac arrest (CA) by pulse palpation.

Materials and methods

Blinded rescuers (82 nurses, 71 doctors) palpated for a brachial pulse in 17 children (1 day-11 years) with non-pulsatile extracorporeal circulation for CA or cardiac failure. Timed rescuer decisions (pulse present/absent) were compared with non-blinded investigator decisions.

Results

CA on 55 occasions was diagnosed by 42 (76%) rescuers in mean (±SD) time 30 ± 19 s. Experienced rescuers diagnosed CA in 25 ± 14 s, inexperienced rescuers in 37 ± 24 s (p = 0.042). CA absent on 98 occasions was confirmed by 77 (79%) rescuers in 13 ± 13 s. Experienced rescuers confirmed absent CA in 9 ± 5 s, inexperienced rescuers in 21 ± 19 s (p = 0.0001). Diagnosis of CA compared to confirmation of absence took longer by all rescuers (p < 0.0001), experienced rescuers (p < 0.0001) and inexperienced rescuers (p = 0.018). Twenty-eight of 33 (85%) experienced doctors diagnosed CA or confirmed absence in 13 ± 9 s, 49 of 61 (80%) experienced nurses in 15 ± 12 s, 11 of 21 (52%) inexperienced nurses in 18 ± 15 s and 31 of 38 (82%) inexperienced doctors in 30 ± 24 s. Overall accuracy was 78% (95%CI 71-84%), sensitivity 0.76 (95%CI 0.64-0.86) and specificity 0.79 (95%CI 0.69-0.86). Experienced doctors were 85% accurate, inexperienced doctors 82%, experienced nurses 80%, inexperienced nurses 52%. Rescuers diagnosing quickly (<10 s) had 90% accuracy, in 11-20 s 77% accuracy and in 21-30 s 62.5% accuracy (p = 0.015).

Conclusions

Diagnosis of cardiac arrest by pulse palpation alone is unreliable. At least 30 s is required but accuracy and speed are related to clinical experience.     

Continuous measurement of cardiac output by the Fick principle in infants and children: Comparison with the thermodilution method

Objective To compare a system that continuously monitors cardiac output by the Fick principle with measurements by the thermodilution technique in pediatric patients.Design Prospective direct comparison of the above two techniques.Setting Pediatric intensive care unit of a university hospital.Patients 25 infants and children, aged 1 week to 17 years (median 10 months), who had undergone open heart surgery were studied. Only patients without an endotracheal tube leak and without a residual shunt were included.Methods The system based on the Fick principle uses measurements of oxygen consumption taken by a metabolic monitor and of arterial and mixed venous oxygen saturation taken by pulse- and fiberoptic oximetry to calculate cardiac output every 20 s.Interventions In every patient one pair of measurements was taken. Continuous Fick and thermodilution cardiac output measurements were performed simultaneously, with the examiners remaining ignorant of the results of the other method.Results Cardiac output measurements ranged from 0.21 to 4.55 l/min. A good correlation coefficient was found:r ²=0.98;P<0.001; SEE=0.14 l/min. The bias is absolute values and in percent of average cardiac output was –0.05 l/min or –4.4% with a precision of 0.32 l/ min or 21.3% at 2 SD, respectively. The difference was most marked in a neonate with low cardiac output.Conclusion Continuous measurement of cardiac output by the Fick principle offers a convenient method for the hemodynamic monitoring of unstable infants and children.     

Assessment of the cardiac output by impedance cardiography (differential rheography) to give optimum continuous positive pressure ventilation (author's transl)]

It is very important to know the cardiac output in artificial positive pressure ventilation for the determination of the exact dosage of dopamine and the endexpiratory pressure. Invasive monitoring of the cardiac output is not suitable for routine bedside use. In our study we looked into the question of whether the dosage of dopamine in continuous positive pressure ventilation could be controlled by impedance determination. Differential rheography, as described by Kaindl, Polzer, and Schuhfried, was used in the study. Relative changes in cardiac output after dopamine administration are shown with sufficient accuracy using the above-mentioned method.