Doppler Cardiac Output Monitor Research Articles

A novel method of trans-esophageal Doppler cardiac output monitoring utilizing peripheral arterial pulse contour with/without machine learning approach.

Transesophageal Doppler (TED) velocity in the descending thoracic aorta (DA) is used to track changes in cardiac output (CO). However, CO tracking by this method is hampered by substantial change in aortic cross-sectional area (CSA) or proportionality between blood flow to the upper and lower body. To overcome this, we have developed a new method of TED CO monitoring. In this method, TED signal is obtained primarily from the aortic arch (AA). Using AA velocity signal, CO (COAA-CSA) is estimated by compensating changes in the aortic CSA with peripheral arterial pulse contour. When AA cannot be displayed properly or when the quality of AA velocity signal is unacceptable, our method estimates CO (CODA-ML) from DA velocity signal first by compensating changes in the aortic CSA, and by compensating changes in the blood flow proportionality through a machine learning of the relation between the CSA-adjusted CO and a reference CO (COref). In 12 anesthetized dogs, we compared COAA-CSA and CODA-ML with COref measured by an ascending aortic flow probe under diverse hemodynamic conditions (COref changed from 723 to 7316ml·min-1). Between COAA-CSA and COref, concordance rate in the four-quadrant plot analysis was 96%, while angular concordance rate in the polar plot analysis was 91%. Between CODA-ML and COref, concordance rate was 93% and angular concordance rate was 94%. Both COAA-CSA and CODA-ML demonstrated "good to marginal" tracking ability of COref. In conclusion, our method may allow a robust and reliable tracking of CO during perioperative hemodynamic management.

Development of trans-esophageal Doppler cardiac output monitoring via machine learning approach

Development of trans-esophageal Doppler cardiac output monitoring via machine learning approach

Comparison of cardiac output measured by oesophageal Doppler ultrasonography or pulse pressure contour wave analysis

Maintaining adequate organ perfusion during high-risk surgery requires continuous monitoring of cardiac output to optimise haemodynamics. Oesophageal Doppler Cardiac Output monitoring (DCO) is commonly used in this context, but has some limitations. Recently, the cardiac output estimated by pulse pressure analysis- (PPCO) was developed. This study evaluated the agreement of cardiac output variations estimated with 9 non-commercial algorithms of PPCO compared with those obtained with DCO. High-risk patients undergoing neurosurgery were monitored with invasive blood pressure and DCO. For each patient, 9 PPCO algorithms and DCO were recorded before and at the peak effect for every haemodynamic challenge. Sixty-two subjects were enrolled; 284 events were recorded, including 134 volume expansions and 150 vasopressor boluses. Among the 9 algorithms tested, the Liljestrand-Zander model led to the smallest bias (0.03 litre min(-1) [-1.31, +1.38] (0.21 litre min(-1) [-1.13; 1.54] after volume expansion and -0.13 litre min(-1) [-1.41, 1.15] after vasopressor use). The corresponding percentage of the concordance was 91% (86% after volume expansion and 94% after vasopressor use). The other algorithms, especially those using the Winkessel concept and the area under the pressure wave, were profoundly affected by the vasopressor. Among the 9 PPCO algorithms examined, the Liljestrand-Zander model demonstrated the least bias and best limits of agreement, especially after vasopressor use. Using this particular algorithm in association with DCO calibration could represent a valuable option for continuous cardiac output monitoring of high risk patients. Comité d'éthique de la Société de Réanimation de Langue Française No. 11-356.

Hemodynamic measurements for evaluating vasovagal syncope in the emergency department.

Syncope is a sudden and transient loss of consciousness and postural tone, with spontaneous recovery without medical intervention. It accounts for 1.0% to 1.5% of emergency department (ED) visits and up to 6% of hospital admissions. Vasovagal syncope may be the cause of syncope in 21% to 40% of cases. A 53-year-old Chinese woman was brought to the ED by ambulance after a near-syncope episode while performing gentle morning exercises. She was hypotensive and bradycardic in the ambulance. Upon arrival at the ED, her blood pressure was 89/61 mmHg. The use of a Doppler cardiac output monitor readily demonstrated that the patient’s systemic vascular resistance was reduced, with cardiac output at the lower limit of the normal range. These hemodynamic data were useful in supporting the diagnosis of vasovagal syncope; they helped in the risk stratification of our patient with syncope, and guided the management and subsequent disposition decision.

Oesophageal Doppler cardiac output monitoring: a longstanding tool with evolving indications and applications.

Much work has been done over the years to assess cardiac output and better grasp haemodynamic profiles of patients in critical care and during major surgery. Pulmonary artery catheterization has long been considered as the standard of care, especially in critical care environments, however this dogma has been challenged over the last 10-15 years. This has led to a greater focus on alternate, lesser invasive technologies. This review focuses on the scientific and clinical outcomes basis of oesophageal Doppler monitoring. The science underpinning Doppler shift assessment of velocity stretches back over 100 years, whereas the clinical applicability, and specifically clinical outcomes improvement can be attributed to the last 20 years. Oesophageal Doppler monitoring (ODM), and its associated protocol-guided fluid administration, has been shown to reduce complications, length of stay, and overall healthcare cost when incorporated into perioperative fluid management algorithms. However, more recent advances in enhanced recovery after surgery programs have led to similar improvements, leading the clinician to consider the role of Oesophageal Doppler Monitor to be more focused in high-risk surgery and/or the high-risk patient.

A comparison of noninvasive bioreactance with oesophageal Doppler estimation of stroke volume during open abdominal surgery

The anaesthetist must maintain tissue perfusion by ensuring optimal perioperative fluid balance. This can be achieved using less invasive cardiac output monitors such as oesophageal Doppler monitoring (ODM). Other less invasive cardiac output monitors using bio-impedence technology (noninvasive cardiac output monitoring, NICOM) may have a role in monitoring the circulation and informing fluid management decisions. To compare estimates of stroke volume from ODM with those from NICOM, a noninvasive monitor using bioreactance, a modification of transthoracic bio-impedence. An observational study. Manchester Royal Infirmary, UK. Data collected in 2011 and 2012. Twenty-two patients scheduled for major, open abdominal surgery. Reasons for noninclusion: atrial fibrillation; heart failure; oesophageal disease; lack of capacity; and known sensitivity to colloid. All patients had oesophageal Doppler cardiac output monitoring as a standard element of anaesthesia care. We placed NICOM Bioreactance electrodes and recorded stroke volume estimates from both devices. Fluid challenges were given by the anaesthetist and the haemodynamic responses were recorded. Stroke volume during surgery. The Bland-Altman method was used to compare bias and limits of agreement for stroke volume and cardiac output. Fluid responders were defined as patients who increased stroke volume by at least 10% after fluid loading. The precision of each device was calculated during periods of haemodynamic stability. We made 788 acceptable measurements of cardiac output. The bias was -6.9 ml and the limits of agreement were -22.9 to 36.8 ml. The percentage error was 57%. Average precision for both the ODM and NICOM were similar, 8.5% (SD 5.4%) and 8.7% (SD 3.2%). The concordance for the stroke volume change following fluid challenge was 90.5%. Both devices produced unacceptable readings with electrical diathermy. Simultaneous stroke volume estimations made by noninvasive Bioreactance (NICOM) and oesophageal Doppler showed bias and limits of agreement that are not clinically acceptable. The measurements made by these two devices cannot be regarded as interchangeable.

Comparison of bioimpedance and oesophageal Doppler cardiac output monitoring during abdominal aortic surgery

Abdominal aortic surgery is a high-risk procedure. Cardiac output monitoring allowing haemodynamic optimisation may reduce the complication rate. Minimally invasive, continuous techniques are preferable. Cardiac output using oesophageal Doppler has been validated in several studies, showing good agreement with the gold standard. The aim of this study was to assess the degree of correlation and agreement between cardiac output measured by oesophageal Doppler and bioimpedance obtained from an endotracheal tube.

Resuscitation in massive obstetric haemorrhage using an intraosseous needle*

A 38-year-old woman experienced a massive postpartum haemorrhage 30 minutes after emergency caesarean delivery. The patient became severely haemodynamically compromised with an unrecordable blood pressure. Rapid fluid resuscitation was limited by the capacity of the intravenous cannula in place at the time and inability to establish additional vascular access using conventional routes in a timely manner. An intraosseous needle was inserted in the proximal humerus at the first attempt and administration of resuscitation fluid by this route subsequently enabled successful placement of further intravenous lines. Blood and blood products were deployed in conjunction with intra-operative cell salvage and transoesophageal Doppler cardiac output monitoring was used to assess adequacy of volume replacement. Haemorrhage control was finally achieved with the use of recombinant factor VIIa and hysterectomy.

Doppler cardiac output monitoring: a tool for all physicians

This article introduces Doppler ultrasound cardiac output monitoring and outlines its increasing utility for managing patients with critical illness in the hospital environment.

Cardiac Resynchronization Therapy Optimization by Ultrasonic Cardiac Output Monitoring (USCOM) Device

We investigated the accuracy and feasibility of a 2D echo-independent ultrasonic continuous wave Doppler cardiac output monitoring device (USCOM) operated by trained nurse for the atrio-ventricular interval (AVI) optimization in cardiac resynchronization therapy (CRT). CRT is of proven benefit in patients with advanced chronic heart failure and ventricular conduction delay. Appropriate AVI selection is critical to optimize hemodynamic in CRT. Currently, most non-invasive methods for AVI optimization are often complicated and labor-intensive. USCOM method, Ritter method, and aortic outflow cardiac output method were used to determine the optima AVI in 20 patients with CRT. The accuracy and time for measurement of each method were determined. The optimal AVI determined by USCOM method had good correlation with Ritter's method and aortic outflow estimated cardiac output method (r2= 0.78, P < 0.01 and r2= 0.73, P < 0.01, respectively). The optimal AVI determined USCOM method showed good agreement (within 10 msec range) with Ritter's method (85% patients) and aortic outflow estimated cardiac output method (80%). The mean time for determining AVI using USCOM method was shorter than that with aortic outflow method (7.1 +/- 0.7 min vs 12.7 +/- 1.1 min, P < 0.01), whereas the mean time was shortest for Ritter method (4.7 +/- 1.6 min vs 7.1 +/- 0.7 min, P < 0.01). USCOM device operated by trained nurse can provide a simple, accurate, and fast non-invasive method for the AVI optimization in CRT population.

Emergency physicians can reliably assess emergency department patient cardiac output using the USCOM continuous wave Doppler cardiac output monitor

1 To develop a training package for ultrasonic cardiac output monitor (USCOM) cardiac output assessments and determine the number of proctored studies necessary for skill acquisition. 2 To develop criteria for acceptance of cardiac output results obtained with the USCOM. 3 To evaluate the reliability of USCOM cardiac output assessments in the ED. The authors developed an audiovisual training package. Four emergency physicians and one geriatrician subsequently underwent hands-on training, and skill acquisition was assessed at the fifth, 10th, 15th and 20th examinations. Six image-scoring criteria were developed to assess acoustic image quality. Upon completion of training a protocol was developed to optimize interassessor reliability. Two trained emergency physicians then performed blinded examinations on ED patients using the protocol and interassessor reliability was evaluated. During training average image score improved between the fifth and 20th assessed patient from 4.6 (95% CI 4.0-5.3) to 5.5 (95% CI 5.0-6.0, Pt-test=0.02) out of 6 and average intra-assessor cardiac output difference improved from 17% (95% CI 4-25) to 5% (95% CI 0-11, Pt-test=0.02). Analysis of 52 cardiac output assessments in 21 ED patients demonstrated excellent interassessor correlation (r=0.96, 95% CI 0.90-0.98, P<0.001). The average interassessor difference in cardiac output and index was 0.2 L/min (4%, 95% CI 3-6) and 0.1 L/min/m2 (4%, 95% CI 2-6), respectively. Emergency physicians with no prior ultrasonographic experience can be trained to obtain reliable cardiac output estimations upon conscious ED patients with the USCOM over the course of 20 patient assessments.

Transcutaneous continuous wave doppler cardiac output monitoring is feasible producing reliable and reproducible signals

Transcutaneous continuous wave doppler cardiac output monitoring is feasible producing reliable and reproducible signals

Cardiovascular changes during laparoscopic cholecystectomy

A transoesophageal Doppler cardiac output monitor was used to study the cardiovascular changes occurring during laparoscopic cholecystectomy in patients without (group A) or with (group B) a history of cardiovascular disease, i.e. hypertension, ischaemic heart disease or heart failure. Insufflation of the abdomen with carbon dioxide caused significant (P<0.01) falls in mean cardiac index (17.9% in group A, 25.1% in group B) and mean stroke volume index (15.3% in group A, 21.2% in group B). Simultaneously, there was a significant(P<0.05) increase in mean systolic blood pressure (19.4%) in group A. There were no other differences in the cardiovascular responses of the two groups. There was no correlation between systolic blood pressure and either cardiac index or stroke volume index. No significant complications or morbidity were associated with the use of the transoesophageal Doppler monitor. We conclude that the cardiovascular changes associated with insufflation are neither predictable by clinical assessment nor adequately determined by routine monitoring. We recommend the transoesophageal Doppler monitor for use in this situation.

Comparison of cardiac output measured by intrapulmonary artery doppler, thermodilution, and electromagnetometry

A Doppler pulmonary artery catheter system (Doppler cardiac output monitor or DOPCOM) that continuously measures instantaneous and mean cardiac output was recently introduced. Because thermodilution (TD) flow measurements may not represent an adequate standard, the present study was designed to compare TD and DOPCOM cardiac output measurements with aortic electromagnetic (EM) flow in cardiac surgical patients. Twenty-one patients scheduled for elective coronary artery bypass grafting were enrolled in the study. Simultaneous measurement of cardiac output by all three methods was performed before cardiopulmonary bypass, after cardiopulmonary bypass with the aorta cannulated and volume intermittently infused, and after decannulation. Analysis of all data demonstrated fair TD and EM correlation ( r = 0.80), with minimal bias (0.03 ± 1.21 L/min) and a median absolute error of 0.53 L/min; DOPCOM and EM data showed moderate correlation ( r = 0.64), a bias of −0.61 ± 1.50 L/min, and a median absolute error the same as TD (0.51 L/min). However, distribution of DOPCOM values was heavily skewed by 3 patients in whom flow measurements immediately after cardiopulmonary bypass were markedly different between the DOPCOM and electromagnetometry, probably because of malposition of the Doppler transducers secondary to partial catheter withdrawal during bypass. Consistent with this theory was the finding that before CPB, the DOPCOM was significantly better than TD in predicting EM flow (median absolute error: DOPCOM, 0.12 L/min, and TD, 0.48 L/min; p = 0.04). Our data suggest that, in general, the DOPCOM shows similar precision to TD for predicting EM flow measurements, although the DOPCOM may underestimate actual flow. However, when optimal position of the DOPCOM catheter is maintained, the device is significantly more precise than TD and does not underestimate flow. Furthermore, the instantaneous on-line data provided by the DOPCOM may potentially provide the basis for beat-to-beat assessment of the pulmonary circulation and right ventricular function.

Non-invasive Doppler-derived cardiac output: A validation study comparing this technique with thermodilution and fick methods

The high mortality and morbidity related to cardiac events remains a considerable problem in vascular surgery. Predicting high risk patients is difficult except perhaps by coronary angiography which is invasive, costly and impractical. It would be useful to have a technique which could easily measure cardiac output and stratify cardiac risk in patients needing vascular surgery. Doppler-derived cardiac output may be such a technique. It offers considerable advantages over Swan-Ganz thermodilution measurement in that it is non-invasive, continuous, inexpensive, and requires only limited technical skill and training. In order to assess and validate a Doppler cardiac output monitor (ACCUCOM 2, Datascope Medical Co. Ltd.), we undertook a prospective study comparing Doppler-derived measurements with those obtained by thermodilution and Fick methods. Twelve patients undergoing elective coronary angiography were studied. Swan-Ganz thermodilution catheters were inserted on completion of cardiac catheterisation and five consecutive thermodilution and Doppler measurements made in each patient. Oxygen saturation from pulmonary artery and aortic blood samples, and a single indirect Fick cardiac output, were calculated. Linear regression analysis for Doppler against thermodilution gave a correlation co-efficient (r) of 0.81 (p less than 0.002), and (r) for Doppler against the Fick method was 0.76 (p less than 0.02). Bland and Altman's statistical method showed the differences to be normally distributed. The mean difference (thermodilution minus Doppler) was 0.32 l/min SD 0.48 l/min, 95% confidence limits -0.64 to +1.28 l/min. Doppler-derived cardiac output compares well with traditional methods of measurement and may be a useful tool in the assessment and monitoring of the high risk vascular patient.

Intraoperative Assessment of the Lawrence 3000 Doppler Cardiac Output Monitor

Transoesophageal Doppler cardiac output measurement was evaluated against the thermodilution method in eleven patients undergoing elective cardiac surgery. A total of 106 pairs of Doppler and thermodilution values were obtained. Cardiac output was measured over a range of 2.3 l.min-1. to 11.51 l.min-1. The mean difference between the Doppler and thermodilution measures was -1.0 l.min-1 (thermodilution minus Doppler). Standard deviction was 1.8 l.min-1. This is a significant difference. It is concluded that these techniques do not agree when measuring cardiac outputs.

Noninvasive Measurement of Cardiac Output by Esophageal Doppler Method During Anesthesia

The authors evaluated the effi ciency and reproducibility of cardiac output measurement by esophageal continuous-wave Doppler ultra sonography (ECO). A total of 114 si multaneous measurements of ECO and thermodilution cardiac output (TDCO) were compared in 25 surgi cal patients undergoing general anes thesia in the supine position. ECO could be obtained easily with mini mal experience by means of a com mercially available Doppler cardiac output monitor. There was a signifi cant correlation between ECO and TDCO (&lt;0.001). The regression equation obtained was Y = 0.992X- 0.029, and the correlation coefficient was 0.935. ECO was more reproduc ible than TDCO, because the aver aged value for coefficient of variation (CV) was 5.2% for ECO and 8.3% for TDCO, and these values were sta tistically significant. Their results in dicate that the esophageal Doppler method provides noninvasive, safe, and continuous cardiac output moni toring in patients during anesthesia in the supine position. This method is more useful in patients for whom in vasive cardiac output monitoring is considered inappropriate.

Transesophageal Doppler Ultrasonography

Cardiac output monitoring by transesophageal Doppler ultrasound has not gained wide clinical acceptance. A recently developed transesophageal Doppler device, Accucom 2, features technological advances aimed to reduce the error of this approach to the monitoring of cardiac output. To determine if Accucom 2 enables more accurate cardiac output monitoring, a prospective investigation was undertaken. Analyses of 923 simultaneous measurements of transesophageal Doppler and thermodilution cardiac output in 47 anesthetized patients were compared. Results using Accucom 2 were highly correlated with the results obtained with thermodilution (R = 0.91) and provided significantly greater accuracy in comparison with a previously developed Doppler cardiac output monitor, Accucom 1. Technological advances in transesophageal Doppler ultrasound hold promise for clinically useful noninvasive monitoring of cardiac output.