Radial Artery Pressure Waveforms Research Articles

Noninvasive assessment of central and peripheral arterial pressure (waveforms): implications of calibration methods

Noninvasive estimation of central blood pressure (BP) from radial artery pressure waveforms is increasingly applied. We investigated the impact of radial artery waveform calibration on central BP assessment and calculated pressure amplification, with focus on the one-third rule used to estimate mean arterial BP (MAP). Pressure waveforms were noninvasively measured at the radial and carotid arteries in 1873 individuals (age 45.8+/-6.1 years). Radial and carotid artery waveforms were calibrated using brachial artery DBP and SBP, MAP estimated with the one-third rule and MAP estimated as brachial DBP along with 40% of brachial artery pulse pressure. Central SBP obtained via a transfer function was 123.5 +/- 15.7, 117.8 +/- 14.2 and 126.0 +/- 15.4 mmHg (mean +/- SD) following above-mentioned three calibration schemes, respectively. Using the same calibration schemes, carotid artery SBP was 131.4 +/- 15.2, 118.4 +/- 14.4 and 126.8 +/- 15.7 mmHg, respectively. Central-to-brachial amplification was 13.0 +/- 3.6 mmHg using second method as compared with 4.6 +/- 3.8 mmHg with third method. Brachial-to-radial amplification was actually negative (-6.3 +/- 4.5 mmHg) using second method, whereas 3.4 +/- 5.5 mmHg was found with third method. Both carotid artery SBP and central SBP obtained via a transfer function are highly sensitive to the calibration of the respective carotid artery and radial artery pressure waveforms. Our data suggest that the one-third rule to calculate MAP from brachial cuff BP should be avoided, especially when used to calibrate radial artery pressure waveforms for subsequent application of a pressure transfer function. Until more precise estimation methods become available, it is advisable to use 40% of brachial pulse pressure instead of 33% to assess MAP.

Comparison of Stroke Volume Variations Derived From Radial and Femoral Arterial Pressure Waveforms During Liver Transplantation

Background Stroke volume variation (SVV) is being increasingly used to predict fluid responsiveness. Since radial arterial pressure (RAP) and femoral arterial pressure (FAP) frequently showing discrepancies during liver transplantation (LT), we sought to investigate the effect of differing arterial waveforms on SVV and cardiac output (CO) derived from the Vigileo device, by comparing SVV and CO values derived from RAP (SVV RAP, CO RAP) and FAP (SVV FAP, CO FAP) during LT. Methods The linear associations and agreements between SVV RAP and SVV FAP and between CO RAP and CO FAP were assessed during LT. Hemodynamic variables were measured at nine predefined time points in all 32 recipients, resulting in 288 data pairs. Results Correlations were observed between SVV RAP and SVV FAP ( r = .961) and between CO RAP and CO FAP ( r = .848) at all time points. These correlations between SVV RAP and SVV FAP ( r = .923) and between CO RAP and CO FAP ( r = .902) existed even during the period when mean RAP and FAP values differed (10 minutes after reperfusion). Bland-Altman analysis for SVV RAP versus SVV FAP and for CO RAP versus CO FAP showed weak biases (−0.2% and −0.5 L/min) and reasonable limits of agreement (−2.2 to 1.8% and −1.9 to 0.9 L/min). The percentage errors for SVV and CO values were 27.0% and 22.2%. Conclusions There was no significant difference between SVV RAP and SVV FAP when measured using the Vigileo device during LT. This finding indicated that SVV obtained using the Vigileo device offered relatively consistent information regardless of the catheterization site.

Caution Using Brachial Systolic Pressure to Calibrate Radial Tonometric Pressure Waveforms: Lessons From Invasive Study

To the Editor: We were very interested to read the recent article by Segers et al1 that prompted the correspondence from O’Rourke and Takazawa,2 who were concerned about the reliability of brachial artery tonometry and the lack of relevant invasive data, as well as the subsequent response from Segers et al.3 We have recently conducted an invasive study that may help resolve …

Performance of Vigileo and LiDCOplus cardiac output monitors during a prolonged cardiac arrest and resuscitation

Performance of Vigileo and LiDCOplus cardiac output monitors during a prolonged cardiac arrest and resuscitation

Arterial Wave Reflection in HIV-Infected and HIV-Uninfected Rwandan Women

To assess differences in arterial wave reflection, a marker of atherosclerosis, in HIV-positive and HIV-negative Rwandan women, applanation tonometry was performed on 276 HIV(+) and 67 HIV(-) participants. Radial artery pressure waveforms were recorded and central aortic waveforms were derived by validated transfer function. Central augmentation index (C-AI), central pulse pressure (C-PP), and peripheral augmentation index (P-AI) were measured. HIV(+) participants were younger and had lower diastolic blood pressure (BP) and 41% of the HIV(+) women were taking antiretroviral therapy (ART). Mean C-AI and P-AI were significantly lower in HIV-infected than in uninfected participants (20.3 +/- 12.0 vs. 25.5 +/- 12.1, p = 0.002 and 74.6 +/- 18.8 vs. 83.7 +/- 20.0, p < 0.001). After age matching, C-AI, C-PP, and P-AI were similar among the groups. On multivariate analysis, age, heart rate, weight, and mean arterial pressure were independently associated with C-AI (R(2) = 0.33, p < 0.0001). Among HIV-infected women, current CD4 count did not correlate with C-AI (Rho = -0.01, p = 0.84), C-PP (Rho = 0.09, p = 0.16), or P-AI (Rho = -0.01, p = 0.83). In conclusion, HIV infection was not associated with increased arterial wave reflection in women with little exposure to antiretroviral therapy and without CV risk factors. Whether long-term ART increases measures of arterial stiffness remains unknown.

The accuracy of central SBP determined from the second systolic peak of the peripheral pressure waveform

Recent evidence suggests that central aortic blood pressure may be a better predictor of cardiovascular risk than peripheral blood pressure. The central SBP (cSBP) can be estimated from the late systolic shoulder of the radial pulse waveform. We compared the second systolic peak of the radial waveform (pSBP(2)) with the central systolic pressure derived by a generalized transfer function in a large cohort, across a wide age range, of patients from the Anglo-Cardiff Collaborative Trial. We also compared pSBP(2) with the true cSBP measured by cardiac catheterization [invasively measured cSBP (cSBPi)]. Noninvasive measurements were made by applanation tonometry using the SphygmoCor device. The aortic pressure waveform was derived from the radial waveform using a validated transfer function. Invasive measures of cSBPi were carried out in a group of 38 patients undergoing diagnostic cardiac angiography, and radial artery pressure waveforms were simultaneously recorded using the SphygmoCor device. Overall, there was a strong correlation (r = 0.99, P<0.001) and good agreement between pSBP(2) and the derived cSBP (mean difference +/- SD 1 +/- 4 mmHg). However, there was a systematic bias with a greater difference between these measures at lower average pressures. There was also a strong correlation and good agreement between the invasively measured cSBPi and pSBP(2) (r = 0.92, P<0.001, mean difference 2 +/- 6 mmHg). The second systolic shoulder of the peripheral pressure waveform approximates the cSBP in a large cohort of patients across a wide age range, but this may be inaccurate at low SBP values.

Uncalibrated Radial and Femoral Arterial Pressure Waveform Analysis for Continuous Cardiac Output Measurement: An Evaluation in Cardiac Surgery Patients

Arterial pressure waveform analysis is a less invasive alternative to the pulmonary artery catheter for continuous cardiac output (CO) measurement. Uncalibrated and calibrated systems are actually available (ie, the FloTrac/Vigileo system [Edwards Lifesciences, Irvine, CA] and the PiCCOplus system [Pulsion Medical Systems, Munich, Germany]). According to the FloTrac/Vigileo manufacturer, reliable measurements can be performed using any existing arterial catheter. The aim of this study was to evaluate CO determined by the FloTrac/Vigileo system using a radial (FCO(radial)) and femoral arterial catheter (FCO(femoral)) as well as the PiCCOplus system (PCO). Intermittent pulmonary artery thermodilution (ICO) was used as primary reference technique. A prospective clinical study. A teaching hospital, single center. Twenty-six cardiac surgery patients. Perioperative CO measurements. CO was assessed at predefined measurement points. FCO(radial), FCO(femoral), and PCO were recorded after the induction of anesthesia, after sternotomy, at skin closure, after intensive care unit transfer, and during intensive care unit stay 12 and 24 hours after study initiation. ICO was determined as the mean of 3 bolus injections. Bland-Altman analysis revealed comparable mean bias and limits of agreement for FCO(radial), FCO(femoral), and PCO when compared with ICO. There was a decreased agreement for all devices in the postoperative period. However, a consistently close agreement was observed for the direct comparison between FCO(radial) and FCO(femoral). Performance of the FloTrac/Vigileo system via radial as well as femoral access and the PiCCOplus monitoring for cardiac output measurement were comparable when tested against intermittent thermodilution in cardiac surgery patients.

Obesity as an independent influential factor for reduced radial arterial wave reflection in a middle-aged Japanese male population

This study aimed to examine whether obesity, including abdominal obesity, is an influential factor for radial arterial wave reflection, as expressed by the augmentation index (AI), in middle-aged Japanese men. Radial arterial pressure waveform was measured using automated applanation tonometry in 828 men (mean age: 47+/-5 years) during an annual health examination at a company. Radial AI was calculated from the waveforms. AI appeared to be similar between subjects with and without obesity (body mass index (BMI) >or=25 and <25 kg m(-2), respectively). However, after adjusting for age, height, heart rate, mean blood pressure, low- and high-density lipoprotein cholesterol, fasting plasma glucose, white blood cell count and other potential confounders, AI was significantly lower in subjects with obesity (71.6%, 95% confidence interval (CI); 70.2-73.0%) than in those without (75.2%, 95% CI; 74.4-76.0%, P<0.001). In a multiple linear regression analysis, BMI was negatively associated with AI (beta=-0.20, P<0.001); other factors associated with AI were heart rate (beta=-0.56), mean blood pressure (beta=0.44), height (beta=-0.24), age (beta=0.15), current smoking (beta=0.09), white blood cell count (beta=0.06) and low-density lipoprotein cholesterol (beta=0.06). Similar associations were found when waist circumference (WC, an index of abdominal obesity) was substituted for BMI in the analysis (beta=-0.12, P<0.001). BMI closely correlated with WC (r=0.87), thus suggesting that approximately 76% (a square of 0.87) of BMI can be explained by WC. In conclusion, although it does not have a major impact, obesity, including abdominal obesity, may be an influential factor for reduced radial AI, independently of well-known confounders, in middle-aged Japanese men.

Is radial artery pressure waveform derived cardiac index is reliable during cardiac surgery with hypothermic cardiopulmonary bypass?.

Discrepancy of central-peripheral arterial pressure after cardiopulmonary bypass may affect the reliability of arterial pressure waveform derived cardiac index (APCI) monitoring. In 15 elective cardiac surgeries employing moderate hypothermic cardiopulmonary bypass (CPB), APCI from radial arterial cannula and pulmonary artery catheter derived cardiac index from thermodilution method (PACI) were measured 1) after anesthesia induction (T1), 2) before CPB (T2), 3) immediately after CPB (T3) and 4) 1 hour after CPB (T4). APCI and PACI were analyzed by using the Bland-Altman analysis. Biases of APCI and PACI at T1, T2, T3 and T4 were 0.093 L/min/m2, -0.053 L/min/m2, 0.485 L/min/m2 and -0.09 L/min/m2, respectively. The limits of agreement (2 SD) at T1, T2, T3 and T4 were from -2.285 to 2.471 L/min/m2, -2.475 to 2.369 L/min/m2, -2.255 to 3.225 L/min/m2 and -2.609 to 2.423 L/min/m2, respectively. Bias of APCI and PACI during entire period (T1-T4) was 0.095 L/min/m2 and 2 SD was from -2.387 to 2.557 L/min/m2. However, mean error % (2 SD/mean) of APCI at T1, T2, T3, and T4 were greater than 30%. Our results were not able to show that APCI measured from radial artery is comparable to PACI for hemodynamic monitoring during cardiac surgery employing moderate hypothermic CPB. Considering the limitations of PACI as a gold standard of hemodynamic monitoring in a certain clinical circumstance, further investigation employing other monitoring method than PACI may be followed to get more definitive conclusion.

Differences in the late systolic shoulder pressure (SBP2) of the radial artery pressure waveform by antihyperensive regimen in the anglo scandinavian cardiac outcomes trial (ASCOT)

Differences in the late systolic shoulder pressure (SBP2) of the radial artery pressure waveform by antihyperensive regimen in the anglo scandinavian cardiac outcomes trial (ASCOT)

Estimated central blood pressure: importance of radial artery pressure waveform calibration

Estimated central blood pressure: importance of radial artery pressure waveform calibration

Response to Impact of Radial Artery Pressure Waveform Calibration on Estimated Central Pressure Using a Transfer Function Approach

We thank Segers et al1 for their interest in our recent study illustrating the importance of central-to-peripheral amplification of systolic blood pressure. Their concern regarding our data centers on the calibration of radial artery waves and the theoretical impact that this will have on amplification of pressure between the aorta and the brachial artery. Amplification expressed as a ratio between central and peripheral pulse pressure is a fiducial parameter. As such, the use of a generalized transfer function does not, in itself, affect this relationship, which is independent …

Impact of Radial Artery Pressure Waveform Calibration on Estimated Central Pressure Using a Transfer Function Approach

To the Editor: It is with great interest that we have read the excellent work of McEniery et al1 on the variability of the relation between central and brachial pulse pressure (pressure amplification), assessed in >10 000 subjects. We were, however, a little surprised about the magnitude of the central-to-brachial pressure amplification, which is in the order of 1.38 for the entire population (estimated from their Table 1). We hypothesize that these high values arise from the use of central aortic pressure curves synthesized from radial pressure tracings, with the most important factor not being the generalized pressure transfer function …

Agreement between carotid and radial augmentation index: Does medication status affect the relation?

Summary Central augmentation index (AI) is an index for arterial stiffness and wave reflection, but the measurement requires technical precision. We recently reported that AI obtained directly from radial arterial pressure waveforms (without using the general transfer function) could provide equivalent information to carotid AI in healthy adults. The aim of the present study was to determine whether such association would exist among patients on anti-hypertensive drugs. Forty-six hypertensive patients taking blood pressure lowering medications (62±9 years, mean±SD) and 78 age-matched apparently healthy adults (60±9 years) were studied. Carotid and radial AI were obtained using arterial applanation tonometry, and radial AI was calculated using the equation [(second peak radial systolic pressure - diastolic pressure)/(first peak radial systolic pressure - diastolic pressure) × 100]. Radial AI was strongly and positively correlated with carotid AI in medicated patients ( r =0.73, P r =0.84, P

Exercise reduces arterial pressure augmentation through vasodilation of muscular arteries in humans

Exercise markedly influences pulse wave morphology, but the mechanism is unknown. We investigated whether effects of exercise on the arterial pulse result from alterations in stroke volume or pulse wave velocity (PWV)/large artery stiffness or reduction of pressure wave reflection. Healthy subjects (n = 25) performed bicycle ergometry. with workload increasing from 25 to 150 W for 12 min. Digital arterial pressure waveforms were recorded using a servo-controlled finger cuff. Radial arterial pressure waveforms and carotid-femoral PWV were determined by applanation tonometry. Stroke volume was measured by echocardiography, and brachial and femoral artery blood flows and diameters were measured by ultrasound. Digital waveforms were recorded continuously. Other measurements were made before and after exercise. Exercise markedly reduced late systolic and diastolic augmentation of the peripheral pressure pulse. At 15 min into recovery, stroke volume and PWV were similar to baseline values, but changes in pulse wave morphology persisted. Late systolic augmentation index (radial pulse) was reduced from 54 +/- 3.9% at baseline to 42 +/- 3.7% (P < 0.01), and diastolic augmentation index (radial pulse) was reduced from 37 +/- 1.8% to 25 +/- 2.9% (P < 0.001). These changes were accompanied by an increase in femoral blood flow (from 409 +/- 44 to 773 +/- 48 ml/min, P < 0.05) and an increase in femoral artery diameter (from 8.2 +/- 0.4 to 8.6 +/- 0.4 mm, P < 0.05). In conclusion, exercise dilates muscular arteries and reduces arterial pressure augmentation, an effect that will enhance ventricular-vascular coupling and reduce load on the left ventricle.

Association Between Wasted Pressure Effort and Left Ventricular Hypertrophy in Hypertension: Influence of Arterial Wave Reflection

Wave reflection during the systole increases left ventricular (LV) pressure, tension-time index (TTI) and myocardial oxygen requirement. The purpose of this study was to extract that component of extra myocardial oxygen requirement that is due to early systolic wave reflection, define it as wasted effort (DeltaE(w)), and examine its relationship to LV hypertrophy (LVH). Radial artery pressure waveforms were recorded using applanation tonometry and central aortic waveforms generated in 98 patients with untreated hypertension. Aortic augmentation index (AI(a)), wave reflection amplitude (i.e., aortic augmented pressure (AG)) and systolic duration (ED-Tr), ejection duration (ED) and round-trip travel time of the pressure wave (Tr) were calculated from the aortic waveform, and DeltaE(w) estimated as 2.09 AG (ED-Tr). Carotid-femoral pulse wave velocity (PWV(e)) was also measured and LV mass index (LVMI) determined by echocardiography. DeltaE(w) was significantly correlated with age, body height, and LVMI. Women had greater DeltaE(w) than men. The correlation between DeltaE(w) and LVMI was independent of age, gender and body height (P = 0.003). Patients with LVH (LVH (+) group) showed greater DeltaE(w) than patients without LVH (LVH (-) group) (P = 0.003), and this difference remained significant when adjusted for confounding factors. Also, AI(a) and AG were higher in the LVH (+) than in the LVH (-) group (both P < 0.01). In contrast, PWV(e) was not different between the groups, and Tr showed only a marginal difference (P = 0.07). DeltaE(w) appears to be directly and positively associated with LVH in untreated hypertensive patients. The amplitude and duration of the reflected wave, rather than its travel time, are probably responsible for this association.

Characterization of the Upper Limb Arterial Properties during Reactive Hyperemia

The radial artery (RA) pressure waveform is commonly used to reconstruct the central aortic pressure waveform. Because the RA pressure waveform has been used as input to this process, its features that are dependent on the local arterial properties can influence the final reconstructed aortic waveform. In this study, we determined the effects of altered upper limb pulse wave velocity (PWV) and local wave reflection parameters on RA pressure waveform augmentation (RA-AIx). Twenty healthy volunteers (10 men) between the ages of 18 and 35 years of age were recruited. Simultaneous pressure waveforms were acquired using arterial tonometers from the right carotid and the radial arteries, prior to and following tourniquet induced hyperemia. The phase velocities from the pressure wave transfer function were used to estimate the pulse wave velocity (PWV(infinity)), the local reflection coefficient (Gamma) and an estimate of the terminal impedance of the upper limbs, PWV(0+). The RA-AIx was represented as a linear, three-parameter model that included the input (the AIx of the carotid artery pressure waveform, CA-AIx), the Gamma and PWV(infinity) of the arm. Tourniquet induced hyperemia did not alter Gamma but reduced PWV(infinity), and PWV(0+) and increased RA-AIx. Multiple linear regression analysis indicated that RA-AIx was increased by high levels of CA-AIx and PWV(infinity) and decreased by elevated Gamma. The relative weighing of CA-AIx, Gamma and PWV(infinity) on RA-AIx were 3:2:1, respectively. The AIx of RA is determined to an equal extent by the input and local factors. Interpretation of the AIx of the RA and the reconstructed central aortic waveform should be made in the context of this relationship.

Subclinical impairment of arterial mechanics in systemic lupus erythematosus identified by arterial waveform analysis

Structural and functional changes in wall and endothelial components of arterial blood vessels underlie the accelerated vascular disease progression in systemic lupus erythematosus (SLE). Using pulse contour analysis we sought to determine if subclinical vascular abnormalities could be identified in a well-characterised cohort of patients with SLE who had no increase in traditional cardiovascular risk factors. Radial artery pressure waveforms were obtained by applanation tonometry and pressure envelopes were analysed by descriptive and model-based approaches. Waveshape morphology was quantified by a novel eigenvector approach and model-based compliance indices of the large arteries (C1, capacitative arterial compliance) and small arteries (C2, reflective arterial compliance) were derived using a third-order four-element modified Windkessel model. Data were recorded from 30 patients with SLE (mean age 44 +/- 7 years and mean SLAM-R 10 +/- 4) and 19 age-matched control subjects. Significant differences in the lower frequency sinusoidal components of the pressure waveforms were evident between groups (P < 0.05). Both C1 and C2 were significantly reduced in patients with SLE: C1 mean +/- SD 13.5 +/- 4.0 ml/mmHg x 10 versus C1 17.5 +/- 4.8 ml/mmHg x 10 (P = 0.003 in patients vs. controls, respectively) and C2 5.2 +/- 3.4 ml/mmHg x 100 versus C2 9.4 +/- 2.8 ml/mmHg x 100 (P < 0.001 in patients vs. controls, respectively). In this group of SLE patients, without an excess of traditional cardiovascular risk factors and SLAM-R scores indicating mild disease, descriptive and model-based analysis of arterial waveforms identified vascular abnormalities at a preclinical stage.

Relationship between augmentation index obtained from carotid and radial artery pressure waveforms

Increased aortic and carotid arterial augmentation index (AI) has been directly linked with cardiovascular disease risk, mortality and morbidity. The aim of this study was to examine whether AI obtained directly from radial artery pressure waveforms (radial AI) can provide information comparable with carotid arterial AI measurements. In a cross-sectional study of 204 apparently healthy subjects (88 men and 116 women) aged 19-76 years (51 +/- 15 years, mean +/- SD), carotid AI [(second peak carotid systolic pressure - first peak carotid systolic pressure)/carotid pulse pressure*100] and radial AI [(second peak radial systolic pressure - diastolic pressure)/(first peak radial systolic pressure - diastolic pressure)*100] were measured using applanation tonometry. Radial AI was strongly correlated with carotid AI (r = 0.86, P < 0.0001, SD of difference 10.0%), although radial AI was consistently approximately 66% higher than carotid AI. In 16 apparently healthy young adults (11 men and five women, aged 23 +/- 3 years) handgrip exercise was immediately followed by post-exercise muscle ischaemia (PEMI) to compare changes in carotid and radial AI during increased sympathetic nervous activity. PEMI caused parallel increases in carotid and radial AI (26 and 19%). Accordingly, changes in radial AI with PEMI were strongly correlated with corresponding changes in carotid AI (r = 0.86, P < 0.0001, SD of difference 7.3%). These results suggest that AI obtained directly from radial arterial pressure waveforms could provide equivalent information to carotid arterial AI, and has potential as a surrogate marker of cardiovascular disease.

Comparison between uncalibrated cardiac output using the femoral and radial arterial pressure waveform in critically ill patients

Cardiac output (CO) monitoring is often required to manage critically ill patients. Nominal values can be determined from analysis of arterial pressure waveforms. It is assumed that arterial waveforms from different arterial sites give similar CO values. The aim of this study was to compare the values of uncalibrated CO derived from simultaneous radial (COr) and femoral (COf) blood pressures.