Arterial Waveform Analysis Research Articles

Arterial waveform analysis.

The bedside measurement of continuous arterial pressure values from waveform analysis has been routinely available via indwelling arterial catheterization for >50 years. Invasive blood pressure monitoring has been utilized in critically ill patients, in both the operating room and critical care units, to facilitate rapid diagnoses of cardiovascular insufficiency and monitor response to treatments aimed at correcting abnormalities before the consequences of either hypo- or hypertension are seen. Minimally invasive techniques to estimate cardiac output (CO) have gained increased appeal. This has led to the increased interest in arterial waveform analysis to provide this important information, as it is measured continuously in many operating rooms and intensive care units. Arterial waveform analysis also allows for the calculation of many so-called derived parameters intrinsically created by this pulse pressure profile. These include estimates of left ventricular stroke volume (SV), CO, vascular resistance, and during positive-pressure breathing, SV variation, and pulse pressure variation. This article focuses on the principles of arterial waveform analysis and their determinants, components of the arterial system, and arterial pulse contour. It will also address the advantage of measuring real-time CO by the arterial waveform and the benefits to measuring SV variation. Arterial waveform analysis has gained a large interest in the overall assessment and management of the critically ill and those at a risk of hemodynamic deterioration.

Comparison of Subjective versus Objective Lower-Extremity Arterial Plethysmographic Waveform Analysis for the Identification of Hemodynamically Significant Inflow Disease

Objective Segmental pressures and subjective air plethysmography waveform (APW) analysis commonly are used in the noninvasive diagnosis of lower-extremity peripheral arterial disease (PAD) and have been used historically to define the extent of PAD. A recent investigation identified objective thigh arterial pulse waveform characteristics for defining hemodynamically significant (>50% diameter) PAD above the level of the common femoral artery (INFLOW). The purpose of this study is to compare subjective and objective APW analysis methodologies for defining INFLOW. Methods Patients who underwent segmental APW analysis and arteriography within 30 days of their noninvasive procedure were studied. Objective APW characteristics obtained from the thigh cuff included acceleration time, maximum amplitude, waveform down-slope curvature, relative amplitude reduction, and gain compensation index. Arteriograms were the basis for comparisons of objective APW criteria versus subjective APW pattern recognition interpretations of INFLOW disease. Results A total of 107 extremities were analyzed. There were statistically significant differences in sensitivity, specificity, positive predictive and negative predictive values, and accuracy for identifying hemodynamically significant INFLOW disease using objective (85%, 93%, 85%, 93%, 91%) versus subjective (53%, 85%, 62%, 80%, 75%) APW analysis, p = 0.0110. Conclusions Objective APW analysis of thigh level waveform characteristics may improve the identification of INFLOW disease in patients undergoing physiologic testing for lower extremity PAD.

The Vigileo-FloTracTM System: Arterial Waveform Analysis for Measuring Cardiac Output and Predicting Fluid Responsiveness: A Clinical Review

TWO HUNDRED THIRTY-FOUR MILLION major surgeries are estimated to be performed annually worldwide.1 Surgical mortality rates range from 0.4% to 4%, with the occurrence of perioperative complications ranging from 3% to 17%.2–5 These perioperative complications typically lead to an increase in the “unnecessary” days of hospitalization after surgery. Therefore, identifying high-risk patients and developing strategies aimed at decreasing perioperative complications are issues of great importance for anesthesiologists.

Two Methods of Hemodynamic and Volume Status Assessment in Critically Ill Patients: A Study of Disagreement.

The invasive nature and potential complications associated with pulmonary artery (PA) catheters (PACs) have prompted the pursuit of less invasive monitoring options. Before implementing new hemodynamic monitoring technologies, it is important to determine the interchangeability of these modalities. This study examines monitoring concordance between the PAC and the arterial waveform analysis (AWA) hemodynamic monitoring system. Critically ill patients undergoing hemodynamic monitoring with PAC were simultaneously equipped with the FloTrac AWA system (both from Edwards Lifesciences, Irvine, California). Data were concomitantly obtained for hemodynamic variables. Bland-Altman methodology was used to assess CO measurement bias and κ coefficent to show discrepancies in intravascular volume. Significant measurement bias was observed in both CO and intravascular volume status between the 2 techniques (mean bias, -1.055 ± 0.263 liter/min, r = 0.481). There was near-complete lack of agreement regarding the need for intravenous volume administration (κ = 0.019) or the need for vasoactive agent administration (κ = 0.015). The lack of concordance between PAC and AWA in critically ill surgical patients undergoing active resuscitation raises doubts regarding the interchangeability and relative accuracy of these modalities in clinical use. Lack of awareness of these limitations can lead to errors in clinical decision making when managing critically ill patients.

A review of intraoperative goal-directed therapy using arterial waveform analysis for assessment of cardiac output.

Increasing evidence shows that goal-directed hemodynamic management can improve outcomes in surgical and intensive care settings. Arterial waveform analysis is one of the different techniques used for guiding goal-directed therapy. Multiple proprietary systems have developed algorithms for obtaining cardiac output from an arterial waveform, including the FloTrac, LiDCO, and PiCCO systems. These systems vary in terms of how they analyze the arterial pressure waveform as well as their requirements for invasive line placement and calibration. Although small-scale clinical trials using these monitors show promising data, large-scale multicenter trials are still needed to better determine how intraoperative goal-directed therapy with arterial waveform analysis can improve patient outcomes. This review provides a comparative analysis of the different arterial waveform monitors for intraoperative goal-directed therapy.

Automated Pulse-Based Diagnosis: Role of TIM Diagnostic Features

Emanated from the idea of reinvestigating ancient medical system of Ayurveda—Traditional Indian Medicine (TIM), our recent study had shown significant applications of analysis of arterial pulse waveforms for non-invasive diagnosis of cardiovascular functions. Here we present results of further investigations analyzing the relation of pulse-characteristics with some clinical and pathological parameters and other features that are of diagnostic importance in Ayurveda.

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.

Haemodynamic monitoring using arterial waveform analysis

To describe the theory behind arterial waveform analysis, the different variables that may be obtained using this method, reliability of measurements and their clinical relevance. Areas for future research are identified. The precision of cardiac output (CO) measurements varies considerably and deteriorates during haemodynamic instability. Significant device-to-device differences exist. Nevertheless, most are sufficiently accurate for tracking changes in CO. Targeted intervention guided by haemodynamic monitoring reduces mortality and morbidity in high-risk surgical patients. Dynamic changes in variables such as systolic pulse variation, pulse pressure variation (PPV) and stroke volume variation (SVV) may be useful for evaluating fluid responsiveness, although important caveats exist. Newer indices such as PPV : SVV ratio may be useful in identifying preload and vasopressor-dependent patients. Peripheral arterial dP/dt has not been validated in critically ill patients and requires further investigation. Despite significant limitations in measurement accuracy and inter-device differences, arterial waveform analysis is a potentially useful tool for monitoring the central circulation in critically ill patients. Future studies investigating the effects of haemodynamic management guided by arterial waveform variables in critically ill patients are urgently needed. The evaluation of cardiopulmonary interactions and usefulness of dP/dt are other areas that require further investigation.

Is peripheral arterial waveform analysis continuous cardiac output monitoring useful with assessment of oxygenation status for patients on veno–venous extracorporeal membrane oxygenation?

Is peripheral arterial waveform analysis continuous cardiac output monitoring useful with assessment of oxygenation status for patients on veno–venous extracorporeal membrane oxygenation?

Central Blood Pressure, Arterial Waveform Analysis, and Vascular Risk Factors in Glaucoma

Reduced ocular perfusion pressure has been linked to glaucoma, and increased arterial stiffness is implicated in systemic cardiovascular risk. This study measured central blood pressure (BP) and arterial waveforms derived from pulse tonometry, together with data on systemic and ocular vascular factors relevant to glaucoma status. A total of 126 patients and 66 normal controls were tested, including 90 primary open-angle glaucoma (POAG) patients and 36 normal tension glaucoma (NTG) patients. Glaucoma patients had been followed for at least 3 years and inclusion required several (>4) reliable visual fields such that glaucoma progression could be determined. Radial pulse tonometry and brachial BP data were collected, together with data on disc hemorrhages, spontaneous venous pulsation, peripapillary atrophy, smoking, and medications. Brachial BP or derived central aortic BP parameters generally showed no significant differences between glaucoma patients and normal individuals. The POAG group had a lower pulse pressure, which was also significant in the regression analysis (P<0.002). In the arterial waveform analysis, POAG was associated with a lower brachial form factor than NTG (P<0.001) and higher subendocardial viability ratio (P<0.008). NTG was associated with a lower body mass index, and POAG with a smoking history. There was an increased incidence of disc hemorrhages and a reduced incidence of spontaneous venous pulsations in the progressing group. Derived central BP does not reveal significant differences from controls or in glaucoma subgroups, but a reduced pulse pressure was identified. There may be some changes in arterial pulse waveform shape suggesting possible differences in diastolic perfusion. Disc hemorrhages and loss of spontaneous venous pulsation were associated with disease progression.

Fluid Therapy LiDCO Controlled Trial—Optimization of Volume Resuscitation of Extensively Burned Patients through Noninvasive Continuous Real-Time Hemodynamic Monitoring LiDCO

This pilot trial aims at gaining support for the optimization of acute burn resuscitation through noninvasive continuous real-time hemodynamic monitoring using arterial pulse contour analysis. A group of 21 burned patients meeting preliminary criteria (age range 18-75 years with second- third- degree burns and TBSA ≥10-75%) was randomized during 2010. A hemodynamic monitoring through lithium dilution cardiac output was used in 10 randomized patients (LiDCO group), whereas those without LiDCO monitoring were defined as the control group. The modified Brooke/Parkland formula as a starting resuscitative formula, balanced crystalloids as the initial solutions, urine output of 0.5 ml/kg/hr as a crucial value of adequate intravascular filling were used in both groups. Additionally, the volume and vasopressor/inotropic support were based on dynamic preload parameters in the LiDCO group in the case of circulatory instability and oligouria. Statistical analysis was done using t-tests. Within the first 24 hours postburn, a significantly lower consumption of crystalloids was registered in LiDCO group (P = .04). The fluid balance under LiDCO control in combination with hourly diuresis contributed to reducing the cumulative fluid balance approximately by 10% compared with fluid management based on standard monitoring parameters. The amount of applied solutions in the LiDCO group got closer to Brooke formula whereas the urine output was at the same level in both groups (0.8 ml/kg/hr). The new finding in this study is that when a fluid resuscitation is based on the arterial waveform analysis, the initial fluid volume provided was significantly lower than that delivered on the basis of physician-directed fluid resuscitation (by urine output and mean arterial pressure).

運動負荷中の心電図とSpO&lt;sub&gt;2&lt;/sub&gt; 脈波を用いた非侵襲連続心拍出量測定のエコードップラーに対する一致度とトレンドの追従性

A new technology called estimated continuous cardiac output (esCCO) uses pulse wave transit time (PWTT) obtained from an electrocardiogram and pulse oximeter to measure cardiac output (CO) noninvasively and continuously. This study was performed to evaluate the accuracy of esCCO during exercise testing. We compared esCCO with CO measured by echo Doppler aortic velocity-time integral (VTIao_CO). The correlation coefficient between esCCO and VTIao_CO was r = 0.87 (n = 72). Bias and precision were 0.33 ± 0.95 L/min with a percentage error of 30.2%. And the correlation coefficient between change in esCCO and change in VTIao_CO was r = 0.75 (n = 70). The esCCO could detect change in VTIao_CO larger than 1 L/min with a concordance rate of 88.2%. The areas under ROC curves to detect VTIao_CO changes more than 15% and 30% were 0.81 and 0.91, respectively. Polar plots show that the mean polar angle was 2.2° and radial limits of agreement were ±43.6°. The trending ability of esCCO is comparable with that of currently available arterial waveform analysis methods. In this study, the validity of esCCO during exercise testing was assessed and shown to be acceptable with respect to agreement and trending ability compared with the echo Doppler.

Radial–femoral concordance in time and frequency domain-based estimates of systemic arterial respiratory variation

Commonly used arterial respiratory variation metrics are based on mathematical analysis of arterial waveforms in the time domain. Because the shape of the arterial waveform is dependent on the site at which it is measured, we hypothesized that analysis of the arterial waveform in the frequency domain might provide a relatively site-independent means of measuring arterial respiratory variation. Radial and femoral arterial blood pressures were measured in nineteen patients undergoing liver transplantation. Systolic pressure variation (SPV), pulse pressure variation (PPV), area under the curve variation (AUCV), and mean arterial pressure variation (MAPV) at radial and femoral sites were calculated off-line. Two metrics, "Spectral Peak Ratio" (SPeR) and "Spectral Power Ratio" (SPoR) based on ratios of the spectral peak and spectral area (power) at the respiratory and cardiac frequencies, were calculated at both radial and femoral sites. Variance among radial-femoral differences was compared and correlation coefficients describing the relationship between respiratory variation at the radial and femoral sites were developed. The variance in radial-femoral differences were significantly different (p<0.001). The correlation between radial and femoral estimates of respiratory variation were 0.746, 0.658, 0.858, 0.882, 0.941, and 0.925 for SPV, PPV, AUCV, MAPV, SPeR, and SPoR, respectively. Assuming a PPV treatment threshold of 12% (or equivalent), differences in treatment decisions based on radial or femoral estimates would arise in 12, 14, 5.4, 5.7, 4.8, and 5.5% of minutes for SPV, PPV, AUCV, MAPV, spectral peak ratio, and spectral power ratio, respectively. As compared to frequency domain-based estimates of respiratory variation, SPV and PPV are relatively dependent on the anatomic site at which they are measured. Spectral peak and power ratios are relatively site-independent means of measuring respiratory variation, and may offer a useful alternative to time domain-based techniques.

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.

Multicenter Study Verifying a Method of Noninvasive Continuous Cardiac Output Measurement Using Pulse Wave Transit Time

Many technologies have been developed for minimally invasive monitoring of cardiac output. Estimated continuous cardiac output (esCCO) measurement using pulse wave transit time is one noninvasive method. Because it does not require any additional sensors other than those for conducting 3 basic forms of monitoring (electrocardiogram, pulse oximeter wave, and noninvasive (or invasive) arterial blood pressure measurement), esCCO measurement is potentially useful in routine clinical circulatory monitoring for any patient including low-risk patients. We evaluated the efficacy of noninvasive esCCO using pulse wave transit time in this multicenter study. We compared esCCO and intermittent bolus thermodilution cardiac output (TDCO) in 213 patients, 139 intensive care units (ICUs), and 74 operating rooms (ORs), at 7 participating institutions. We performed electrocardiogram, pulse oximetry, TDCO, and arterial blood pressure measurements in patients in ICUs and ORs; a single calibration was performed to measure esCCO continuously. TDCO measurement was performed once daily for ICU patients and every hour for OR patients, and just before the removal of the pulmonary arterial catheter from patients in both the ICU and OR. We evaluated esCCO against TDCO with correlation analysis and Bland and Altman analysis and also assessed the change of bias over time. Furthermore, we inspected the impact of change in systemic vascular resistance (SVR) on change in bias because abnormal SVR was assumed to be a factor contributing to the change of the bias. From among 588 esCCO and TDCO datasets (excluding calibration points), 587 datasets were analyzed for 213 patients. The analysis results show a correlation coefficient of 0.79 (P < 0.0001, 95% confidence limits of 0.756-0.819), a bias (mean difference between esCCO and TDCO) of 0.13 L/min (95% confidence interval of bias 0.04-0.22 L/min), and a precision (1 SD) of 1.15 L/min (95% prediction interval was -2.13 to 2.39 L/min). There were no significant differences among 3 defined time intervals over 48 hours after calibration (repeated-measures analysis of variance P = 0.781) in the ICU. The influence of SVR on esCCO analysis showed a correlation coefficient between SVR and an error of 0.37 (P < 0.0001, 95% confidence interval 0.298-0.438). The efficacy of noninvasive esCCO technology was compared with TDCO in 213 cases. Five hundred eighty-seven datasets comparing esCCO and TDCO showed close correlation and small bias and precision, which were comparable to current arterial waveform analysis technologies.

The Effects of Acute Hypobaric Hypoxia on Arterial Stiffness and Endothelial Function and its Relationship to Changes in Pulmonary Artery Pressure and Left Ventricular Diastolic Function

This study investigated, for the first time, the effects of simulated high altitude, following acute hypobaric hypoxia (HH), on simultaneous assessment of large artery stiffness and endothelial function and its inter-relationship to left ventricular (LV) diastolic function, pulmonary artery systolic pressure (PASP), and estimated PA vascular resistance (PVR). Ten healthy subjects were studied at baseline pre and following acute HH to 4800 m for a total of 180 minutes. Assessments of LV diastolic function, mitral inflow, estimated LV filling pressure (E/e'), PVR, and PASP were undertaken using transthoracic echocardiography. Simultaneous assessments of arterial stiffness index (SI), systemic vascular resistance (SVR), vascular tone, and endothelial function (reflective index [RI]) were performed using pulse contour analysis of the digital arterial waveform. Acute hypoxia led to a fall in SpO₂ (98.1±0.7 vs. 71.8±7.1%; p=0.0002), SVR (1589.1±191.2 vs. 1187.8±248.7; p=0.004), and RI (50.8±10.3 vs. 33.0±6.5%; p=0.0008) with an increase in PASP (24.3±2.2 to 35.0±5.3 mmHg; p=0.0001) and estimated PVR (116.40±19.0 vs. 144.6±21.5; p<0.001). There was no rise in either SI (p=0.13), mitral early annular early e' filling velocity or E/e'. There was a significant inverse correlation between SpO₂ and PASP (r=-0.77; p<0.0001), PVR (r=-0.57; p=0.008) and between the fall in SpO₂ and change (Δ) in RI (baseline vs. 150 min, r=-0.52; p<0.001). There was a modest inverse correlation between ΔRI (lower ΔRI=worsening endothelial function) and ΔPAP (r=-0.55; p=0.10) and a strong inverse correlation between ΔRI and ΔPVR (r=-0.89; p=0.0007). Acute hypobaric hypoxia does not significantly alter large artery stiffness or cause overt LV diastolic function. However, the degree of hypoxia influences both the systemic endothelial and pulmonary vascular responses. This noted association is intriguing and requires further investigation.

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of cardiac output

Study ObjectivesTo compare the Nexfin cardiac output (CO) with the CO obtained from transthoracic Doppler echocardiography (TTE) during routine cardiac function screening. DesignObservational clinical study. SettingEchocardiography laboratory. Patients40 ASA physical status 1 and 2 patients scheduled for routine TTE examination. InterventionsNone. Measurements and Main ResultsIn 40 patients scheduled for routine TTE examination, we obtained simultaneous CO measurements with Doppler ultrasound and derived from Nexfin blood pressure measurements. Correlation and level of agreement between Nexfin and TTE were analyzed using Pearson correlation coefficient and Bland-Altman plots. The Pearson correlation coefficient for Nexfin versus TTE was 0.68 (CI: 0.46 - 0.82, P < 0.0001). Bland-Altman analysis showed a bias of 0.51 ± 1.1 L/min and limits of agreement of -1.6 to 2.6 L/min, with a percentage error of 39%. ConclusionsConsidering limits of precision of CO measurements with Doppler echocardiography (± 30%), the agreement between noninvasive CO measurement with the Nexfin and TTE is reasonable.

Evaluating the Adequacy of Fluid Resuscitation in Patients with Septic Shock: Controversies and Future Directions

Fluid resuscitation is a cornerstone in the treatment of severe sepsis and septic shock. However, there is little evidence to guide clinicians in its administration. Current guidelines recommend targeting fluid therapy based on measurements of cardiac filling pressures, such as central venous pressure. Static pressures are poor predictors of a patient's response to fluid. Such response can be better predicted by measuring changes in hemodynamic parameters caused by positive pressure ventilation or maneuvers designed to simulate increased preload. These changes can be measured by analysis of arterial waveforms, echocardiography or Doppler, or with emerging noninvasive technologies. This article reviews the current role of fluid replacement strategies and the use of monitoring systems in the overall resuscitation of patients with severe sepsis and septic shock.

Noninvasive Evaluation for Congenital Arteriovenous Fistulas and Malformations

Although relatively rare, congenital arteriovenous fistulas and other vascular anomalies present a diagnostic challenge to the clinician. The same noninvasive tests that are used for diagnosing arterial occlusive disease in the extremities will also detect arteriovenous fistulas. These tests include segmental limb pressure measurements, segmental plethysmography, and arterial waveform analysis. Additionally, magnetic resonance imaging can be used to determine the extent of these vascular anomalies and the involvement of muscle skin and bone, all of which have a direct bearing on resectability. This article will examine these diagnostic modalities and explain how they can be used in this setting.

What are the real determinants of the ambulatory arterial stiffness index?

O ver the last few years, increasing attention has been devoted to the pathophysiological role of large arteries in functionally coupling the left ventricle with peripheral vessels [1]. Particularly, an increasing number of articles have focused on the investigation of the functional properties of the large arteries, through the availability of devices able to allow the noninvasive analysis of arterial pulse waveforms in normal conditions, as well as the assessment of their modifications in a number of diseases [2,3]. Making use of this approach, evidence has been provided that arterial stiffness, assessed through the quantification of aortic pulse–wave velocity (PWV), may be a predictor of cardiovascular organ damage as well as of cardiovascular events [4,5]. On the basis of such evidence, aortic PWV has been included among those factors influencing prognosis in hypertensive patients, the evaluation of which may allow a more precise assessment of cardiovascular risk [6]. In spite of its universally acknowledged pathophysiologic and clinical value, however, aortic PWV has not become yet a routine procedure to assess the level of cardiovascular risk of hypertensive patients in daily clinical practice. This is mainly due to the need of dedicated and often expensive equipment for its assessment, as well as to the requirement of careful training of the personnel in charge of its measurement. These difficulties have stimulated research and development of new technologies to estimate arterial stiffness in humans in an easier manner, based on the obvious consideration that a technique able to assess arterial wall properties, without the need of using specially designed and costly equipment and without the mandatory requirement of carefully trained and highly qualified observers,