Intra-arterial Measurements Research Articles

Noninvasive Estimation of End‐Systolic Aortic Pressure in Children

To simplify the estimation of end‐systolic aortic pressure (Pes) noninvasively, a regression equation was derived from intra‐arterial measurements. Peak‐systolic (Pps), Pes, and diastolic aortic pressure (Pd), pulse pressure (Pp), heart rate, hemoglobin, body weight, and height were measured. Cardiac index and body surface area were calculated in 66 patients (17 with aortic runoff lesions, group I; 49 without lesions, group II) with various heart diseases without aortic stenosis (35 males, 31 females, mean age 4.6 years) during the course of diagnostic catheterization. Using a stepwise regression analysis, the following relationship was determined from the combined groups: Pes= 0.422*Pps+ 0.617*Pd+ 1.377. The correlation between Pes measured directly and Pes calculated from our formula was quite strong(r= 0.957, P= 0.0001), as was the correlations between each subgroup (r= 0.948, group I; r= 0.959, group II). The correlation between Pes calculated and that estimated using an indirect carotid pulse tracing method was also strong (r= 0.912, P= 0.0001, n= 31). This regression equation appears applicable to infants or children with aortic runoff lesions in whom it is difficult to measure Pes by noninvasive methods using the carotid pulse. (ECHOCARDIOGRAPHY, Volume 8, September 1991)

Continuous blood gas monitoring with an intraarterial optode during one-lung anesthesia

ECAUSE OF THE possibility of hypoxemia and hypoventilation during one-lung anesthesia, an accurate method of continuously monitoring both oxygenation and ventilation would be useful. Arterial blood gas (ABG) sampling is intermittent, expensive, and may result in delays in recognizing hypoxia, hypercarbia, and acidosis. Transcutaneous oxygen tension measurement and pulse oximetry have been recommended during one-lung ventilation (OLV), but both techniques have limitations and neither monitors ventilation.‘” The fiberoptic intraarterial optode makes use of the phenomenon of fluorescence quenching to determine blood gases and pH? The three-component optode (Cardiovascular Devices, Inc, Irvine, CA) is easily inserted through an 18-gauge radial artery catheter and allows continuous arterial pressure monitoring as well as access for blood sampling. The optode technology has also been applied to continuous blood gas monitoring in the extracorporeal circuit during cardiac surgery.6Z7 A case of OLV using continuous intraarterial optode measurement of pHa, PaOZ, and PaCO, is reported.

Arterial Tonometry for Noninvasive, Continuous Blood Pressure Monitoring during Anesthesia

Arterial tonometry is a technique used to measure arterial blood pressure noninvasively. The authors developed a new tonometer system containing an array of 15 piezoresistive pressure transducers, a mechanical positioning system, signal conditioning and multiplexing electronics, and a display and control console. The authors evaluated the accuracy, reliability, and clinical acceptability of this system by comparing tonometric blood pressure measurements with intraarterial blood pressure measurements in 60 anesthetized patients. Blood pressure was measured intraarterially in either the right or left radial artery by a Gould P23XL calibrated transducer, whereas blood pressure was measured by tonometer at the radial artery of the other arm. The tonometric waveform was similar to the intraarterial waveform. Simultaneous tonometer and intraarterial systolic blood pressures of the 60 patients (3,036 data sets) had an overall regression coefficient, r = 0.97, and an equation, regression equation = 0.95X + 5.8. Similar values were obtained for mean and diastolic pressures. Regression analyses of the paired tonometric and intraarterial blood pressure values showed good correlations in both sexes and in ages ranging from 8 to 82 yr (r = 0.94-0.97). Mean absolute values of error (precision) for the systolic, mean, and diastolic measurements did not differ significantly among the five systolic, five mean, and four diastolic pressure groups and ranged from 3.6 to 6.6 mmHg, with negligible bias, with intraarterial pressure used as the reference. Bias for the various pressure groups was small: -0.9-3.6 mmHg for systolic; -3.0-0.7 mmHg for mean; and -2.1-4.5 mmHg for diastolic. The "limits of agreement" (mean difference +/- two standard deviations) were within an acceptable range for clinical anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Reply to Vardan et al’s “Importance of Intraarterial Blood Pressure Measurement in the Evaluation of a New Antihypertensive Agent and the Need to Define Hypertension Also by This Method”

Reply to Vardan et al’s “Importance of Intraarterial Blood Pressure Measurement in the Evaluation of a New Antihypertensive Agent and the Need to Define Hypertension Also by This Method”

Effects of dietary sodium and fish oil on blood pressure development in stroke-prone spontaneously hypertensive rats.

The postulated antihypertensive effect of dietary fish oil and the influence of dietary sodium on this effect were evaluated in young stroke-prone spontaneously hypertensive rats (SHRSP) by direct intra-arterial measurement of blood pressure. Weaning rats were fed synthetic diets containing olive oil or eicosapentaenoic acid-enriched fish oil (5% of dry weight) with normal (0.23%) or high (2.8%) sodium content. Catheters were implanted after 3 months for blood pressure measurement under resting conditions and to sample blood for catecholamine determinations. Effects of fish oil on vascular reactivity were assessed in the in situ blood-perfused mesentery. The overall observation, from a series of experiments, was that feeding diets containing 5% fish oil to young SHRSP resulted in a small but consistent suppression of the development of hypertension. This effect could be counteracted, however, by increasing dietary sodium intake. Observations after ganglion blockade indicate that the antihypertensive effect of fish oil is unlikely to result from a reduction in sympathetic vascular tone.

Measurement of systolic blood pressure using pulse oximetry during helicopter flight

Monitoring of vital signs in critically ill patients during helicopter flight is difficult because of the noise and vibrations of the aircraft. We evaluated the use of a pulse oximeter to measure systolic BP intraflight. Systolic BP measured by pulse oximetry was compared with systolic BP measured by the direct intra-arterial and the arterial occlusion methods intraflight. Systolic BP by pulse oximetry was measured by observing the return of the plethysmographic waveform of the pulse oximeter as the BP cuff ipsilateral to the pulse oximeter probe was slowly deflated. Arterial occlusion pressure was measured by observing the return of the intraarterial waveform as the BP cuff ipsilateral to the arterial cannula was slowly deflated. The study was performed during patient transport, intraflight. Ten critically ill patients were studied. None Seventy-three sets of measurements were recorded. The best correlation (r2 = .99) was found between pulse oximetry and the arterial occlusion method. The indirect methods correlated better with each other than with direct intraarterial measurements. The noise and the vibrations of the helicopter did not significantly interfere with the operation of the pulse oximeter. We conclude that a pulse oximeter that displays a plethysmographic waveform can accurately measure systolic BP intraflight.

Chronic Effects of Focused Electrohydraulic Shock Waves on Renal Function and Hypertension

The chronic effects of focused electrohydraulic shock waves were studied in a minipig model. Fifteen animals underwent a unilateral nephrectomy and compensatory renal hypertrophy was allowed to take place over a minimum of six months. Baseline studies were then carried out consisting of 1) serum creatinine, blood urea nitrogen, and plasma renin levels 2) intra-arterial blood pressure measurement and 3) 3H-inulin clearance. Ten of the animals then underwent 8 shockwave treatments (2500 shocks per treatment), alternately to the upper and lower pole of the kidney, at two weeks intervals. A total of 20,000 shock waves were administered to each minipig over the four month period. The five control pigs underwent sham procedures. The renal function and blood pressure evaluations were then repeated. No significant decrease in renal function was noted in the experimental animals when compared to the controls. In addition, renin mediated hypertension was not observed despite the excessive number of total shock waves delivered to the kidney.

On the reliability of the Penaz cuff during systemic and local fingertip vasodilatation at rest and in exercise

To compare the readings of blood pressure by the Riva-Rocci (RR) method with those of peripheral arterial pressure (PAP) as recorded by the Finapres (FP) device, exercise was performed by six male subjects on a cycle ergometer at a constant exercise intensity of 140 W. In addition, forearm volume was determined by impedance plethysmography. At rest, systolic FP values exceeded RR values by greater than or equal to 10 mmHg. During 60-min exercise both values at first increased almost in parallel with each other. While RR reached a plateau after 3 min, FP then started to decrease continuously up to the 10th min and finally stabilized at 20-30 mmHg below RR. The impedance values showed a similar declining slope, indicating vasodilatation. To separate the effects of sympathetic drive from heat elicited vasodilatation, a second experimental series was performed with ischaemic static calf exercise (5 min, 90 N), since this increases the sympathetic tone but prevents systemic heat distribution. In contrast to findings reported from intra-arterial measurements, no exercise effect on the pulse pressure amplification was obtained. However, the heating of one fingertip distal to the FP-cuff led to a significant decrease in PAP compared to the control recording made simultaneously from the other hand. It was concluded that heat induced vasodilatation may make FP unrepresentative of systemic blood pressure, in particular during exercise. Moreover, the FP-cuff seemed to induce substantial vasoconstriction due to venous occlusion. The FP method would therefore be useful for monitoring continuously systemic blood pressure if no (dilative) vasomotor changes occurred or their ranges and time courses were known sufficiently well.

Importance of Intraarterial Blood Pressure Measurement in the Evaluation of a New Antihypertensive Agent and the Need to Define Hypertension Also by This Method

Importance of Intraarterial Blood Pressure Measurement in the Evaluation of a New Antihypertensive Agent and the Need to Define Hypertension Also by This Method

Blood pressure measurement: an evaluation of direct and indirect methods

In order to evaluate the differences between the blood pressure values obtained by direct intraarterial (DM) and indirect sphygmomanometer (IM) measurements, both systems were employed in 30 patients during their immediate postoperative period (24 hours) at our Intensive Care Unite after open heart surgery. The total number of determinations was 355. The statistical study of data lead us to the following conclusions: 1. 1. There are significant differences between arterial pressure values obtained by DM and IM falling within an acceptable range of error for clinical purposes 2. 2. Both methods of measurement, direct and indirect, are highly influenced by technical details that have to be carefully standardised if suitable research values are to be obtained.

The Reliability of Auscultatory Measurement of Arterial Blood Pressure: A Comparison of the Standard and a New Methodology

In 48 individuals with a wide range of arm circumferences blood pressure measured indirectly with two different cuffs was compared to direct intraarterial measurements. The two cuffs were a standard size cuff (12 X 35 cm) and a newly developed cuff, containing three rubber bags of different sizes, which automatically selects the appropriately sized bag in relation to arm circumference (Tricuff, Pressure Group AB, Sweden). The Tricuff correctly placed 42 of the 43 patients in the "normotensive" range, ie, diastolic blood pressure less than 90 mm Hg, whereas the standard cuff put only 33 of 44 patients in this range (P less than .005). The discrepancy was not only due to the expected better performance in patients with obese arms, but also in the subgroup of patients with arms in the range 22 to 31 cm, in which group both cuffs would measure blood pressure with a 12 cm wide rubber bag. The number of correctly identified "normotensive" patients was noticeably higher with the Tricuff than with the standard cuff (30/31 v 25/32, P = .053). The better specificity of the new cuff thus offers an improvement over the standard cuff. There are several potential clinical advantages of this, mainly that the risk of erroneously labelling normotensive individuals as hypertensive is reduced.

A rapid, accurate, noninvasive technique for diagnosing critical and subcritical stenoses in aortoiliac arteries

Accurate hemodynamic evaluation of the aortoiliac system for the purpose of determining the need for an inflow procedure currently requires invasive pressure measurements. This study was undertaken to evaluate a noninvasive technique with the aortofemoral transfer function. Twenty-eight human aortoiliac segments were studied with intraarterial pressure measurements, with and without papaverine injection, and by calculation of the Doppler-derived mean power frequency index obtained by digital signal processing of aortic and femoral spectra. The procedure is menu driven and can be performed by any duplex ultrasound technologist. This technique involves recording 20 aortic and 20 femoral Doppler signals, requiring less than 1 minute of data acquisition time. Intraarterial pressure measurements were used to classify arteries into the three following groups: (1) normal arteries, (2) arteries with subcritical stenoses, and (3) arteries with critical stenoses. The mean power frequency index of group 1 arteries (n = 7) was 0.63 ± 0.04, of group 2 arteries (n = 6) was 0.46 ± 0.02, and of group 3 arteries (n = 15) was 0.21 ± 0.05. These mean power frequency index values were significantly different by analysis of variance (ANOVA) (p < 0.0001). Each group could be differentiated from the other groups with a sensitivity of 0.83 to 1.00, a specificity of 1.00, and an accuracy of 0.92 to 1.00 compared to intraarterial pressure measurements, including papaverine testing. Measurement of the mean power frequency index is a rapid, noninvasive technique that diagnoses and quantifies aortoiliac stenoses with an accuracy similar to intraarterial pressure measurements.

A rapid, accurate, noninvasive technique for diagnosing critical and subcritical stenoses in aortoiliac arteries

Accurate hemodynamic evaluation of the aortoiliac system for the purpose of determining the need for an inflow procedure currently requires invasive pressure measurements. This study was undertaken to evaluate a noninvasive technique with the aortofemoral transfer function. Twenty-eight human aortoiliac segments were studied with intraarterial pressure measurements, with and without papaverine injection, and by calculation of the Doppler-derived mean power frequency index obtained by digital signal processing of aortic and femoral spectra. The procedure is menu driven and can be performed by any duplex ultrasound technologist. This technique involves recording 20 aortic and 20 femoral Doppler signals, requiring less than 1 minute of data acquisition time. Intraarterial pressure measurements were used to classify arteries into the three following groups: (1) normal arteries, (2) arteries with subcritical stenoses, and (3) arteries with critical stenoses. The mean power frequency index of group 1 arteries (n = 7) was 0.63 +/- 0.04, of group 2 arteries (n = 6) was 0.46 +/- 0.02, and of group 3 arteries (n = 15) was 0.21 +/- 0.05. These mean power frequency index values were significantly different by analysis of variance (ANOVA) (p less than 0.0001). Each group could be differentiated from the other groups with a sensitivity of 0.83 to 1.00, a specificity of 1.00, and an accuracy of 0.92 to 1.00 compared to intraarterial pressure measurements, including papaverine testing. Measurement of the mean power frequency index is a rapid, noninvasive technique that diagnoses and quantifies aortoiliac stenoses with an accuracy similar to intraarterial pressure measurements.

Blood pressure measurement during transport A comparison of direct and oscillotonometric readings in critically ill patients

This study assessed the accuracy of oscillotonometric blood pressure measurement in critically ill patients during transfer. Direct intra-arterial pressure measurements were taken in 44 transported patients as a 'gold standard' and compared with readings from four portable automatic oscillotonometers--the Dinamap 8100, Lifestat 100, Propaq 102 and Takeda UA711. All under-read systolic pressure (by 13%, 21%, 19% and 13% respectively) and over-read diastolic pressure (by 15%, 5%, 27% and 15% respectively) in comparison to direct pressure measurement. The limits of agreement for 95% of comparisons were broad. The systematic difference between direct and oscillotonometric measurements and the variability between and within patients show that direct oscillotonometric measurements are not interchangeable in these patients. Portable automatic oscillotonometers should not be substituted for direct monitoring in such circumstances.

The initial hemodynamic response to newer antihypertensive agents at rest and during exercise: Review of visacor, doxazosin, nisoldipine, tiapamil, perindoprilat, pinacidil, dilevalol, and carvedilol

Antihypertensive drugs may lower blood pressure through very different mechanisms, initially as well as during chronic use. This article is a review of the immediate hemodynamic changes induced by a beta blocker (visacor), an alpha-receptor blocker (doxazosin), two calcium antagonists (tiapamil and nisoldipine), an angiotensin-converting enzyme inhibitor (perindoprilat), two double-acting compounds (dilevalol and carvedilol), and placebo studied in 126 patients with mild to moderately severe essential hypertension. The patient populations of the different treatment groups were comparable. The invasive hemodynamic technique, including intraarterial blood pressure (BP) recording and measurements of cardiac output by cardiogreen, was the same in all studies. All antihypertensive compounds examined induced a rapid reduction in blood pressure both at rest and during exercise, while no significant changes occurred in the placebo group. This review shows the scope of hemodynamic responses, ranging from peripheral vasodilation to a reduction of heart rate and blood flow. Furthermore, different counterregulatory effects blunting the immediate BP reduction are demonstrated.

Parkinson's disease and hypotension: 24‐hour blood pressure recording in ambulant patients

Continuous intra-arterial blood pressure was recorded in 5 ambulatory patients with Parkinson's disease and in 5 control subjects. The 24-h mean systolic blood pressure was 135 +/- 7.6 mmHg in controls and 123.8 +/- 8.1 mmHg (p less than 0.01) in the parkinsonian group. Similarly, diastolic blood pressure was 89 +/- 8.1 mmHg in the control group while in the parkinsonian patients it was lower, 69.4 +/- 5.8 (p less than 0.01). Averages were also calculated for 8-h periods, the results of which indicate that both systolic and diastolic blood pressure were significantly lower in patients than in controls in all three 8-h periods of the day. We normalized the blood pressure curve to mealtimes and arousal times and did not observe any difference between parkinsonian patients and controls. This first study reporting continuous intra-arterial blood pressure measurements in ambulant parkinsonian patients demonstrates that blood pressure in such patients is lower than the mean for their age group. This finding may be of direct relevance in the management of idiopathic parkinsonism.

Artefacts in Measurement of Blood Pressure and Lack of Target Organ Involvement in the Assessment of Patients with Treatment-Resistant Hypertension

To determine the relative importance of factors known to cause therapy-resistant hypertension, and to derive an efficient approach to the evaluation of this problem in clinical practice. Consecutive sample. University hospital hypertension clinic and clinical research center. Fifteen patients referred for management of refractory hypertension and found to have a seated diastolic blood pressure greater than 95 mm Hg while taking a standard dose of hydrochlorothiazide, propranolol, and hydralazine or its equivalent for at least 4 weeks. Seven patients (group 1) had normal, resting mean intra-arterial blood pressure (mean pressure less than 107 mm Hg) and eight had elevated pressure (group 2). Patients in group 1 had minimal or not target organ involvement whereas those in group 2 had higher minimum vascular resistance by forearm plethysmography and greater interventricular septal wall thickness. Factors contributing to resistant hypertension, particularly in group 1, were "office hypertension" (clinic systolic blood pressure at least 20 mm Hg higher than home systolic blood pressure), pseudohypertension (cuff diastolic blood pressure at least 15 mm Hg higher than simultaneously determined intra-arterial pressure), and "cuff-inflation hypertension" (intra-arterial diastolic blood pressure rise of at least 15 mm Hg during cuff inflation). Home blood pressure monitoring and echocardiography are recommended as initial steps in the evaluation of patients with resistant hypertension. Intra-arterial blood pressure measurement is particularly helpful in patients with resistant hypertension who do not have office hypertension yet have normal septal thickness on echocardiography.

Clinical assessment.of cardiac output

Cardiac output estimation is an important and much needed measurement for assessing patients in heart failure. In hypertension, it is vital for understanding the haemodynamic basis of the disease and the mode of action of drugs. Measurements of blood pressure and cardiac output provide the only means of estimating peripheral resistance. Of the available methods to determine cardiac output, thermodilution is the most practical, although it has its difficulties and care has to be exercised in its use. When intra-arterial blood pressure measurements are needed, the dye-dilution method is equally valid, and if respiratory techniques are available the Fick principle may also be used. Of the non-invasive methods, none is yet developed to a stage suitable for general clinical use. Doppler velocimetry is the most promising technique, but it requires complex computer analysis and, as yet, can reliably be used only to measure changes in cardiac output in an individual. The technique has been assessed against the electromagnetic flowmeter in man and gives reasonable accuracy and repeatability. Echocardiography and impedance cardiography are not yet satisfactory for clinical use; neither are the radionuclide methods, apart from the 'first pass' method, but this also needs further verification.

Accutracker: Evaluations of a New Ambulatory Blood Pressure Monitor

The aim of this study was to evaluate the Accutracker noninvasive ambulatory blood pressure monitor in comparison to direct intra-arterial blood pressure measurement and to that derived from another automatic device already widely used (Copal). Intra-arterial comparisons in 14 patients produced an acceptable assessment of blood pressure. There was no significant difference in the mean values for systolic (mean difference +5 ± 10.5 mm Hg) or diastolic pressure (mean difference +9 ± 8.3 mm Hg). Sixty-one percent of systolic and diastolic recordings fell within ±10 mm Hg of intra-arterial measurements and 95 and 92% respectively within ± 20 mm Hg. In 51 patients the Copal vs. Accutracker measurements also compared favourably. The overall mean systolic blood pressure was 138 ± 22 (Copal) vs. 136 ± 18 mm Hg (Accutracker) and overall mean diastolic pressure was 83 ± 13 (Copal) vs. 79 ±12 mm Hg (Accutracker ) (p = NS). Only three measurements of systolic blood pressure and four of diastolic pressure fell outside ± 2 SD from the mean difference of recordings between the devices. The device also yielded satisfactory repeatability of measurements but was unable to accurately record blood pressure during treadmill exercise. Exercise studies apart, this device compares very favourably with other available automatic or semiautomatic devices and in addition offers noninvasive ambulatory monitoring.

Autonomic control of the diurnal variation in arterial blood pressure and heart rate in spontaneously hypertensive and Wistar-Kyoto rats.

The relative influences of sympathetic and parasympathetic neural modulation on mean arterial pressure (MAP) and heart rate (HR), and their respective variabilities, were studied in young spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). An on-line computerized system was used for continuous intra-arterial measurements of MAP and HR in unrestrained rats. In addition, the autonomic nervous control of MAP and HR was studied in ageing SHR and WKY. Both WKY and SHR showed diurnal rhythms with regard to MAP and HR. The MAP variability was higher in SHR than in WKY during both daytime (inactive) and night-time (active), and did not change in response to either beta 1-adrenoceptor- or cholinergic blockade. Structural vascular changes, with a resultant increase in reactivity, may explain the elevated MAP variability in SHR. HR variability was clearly reduced in SHR; this was not influenced by vagal blockade, whereas HR variability was significantly reduced in WKY. This pattern is suggested to be due to a reduced tonic vagal discharge in SHR, as part of a persistent, mild defence reaction. The initial reduction in vagal activity will in turn eliminate vagally mediated tachycardias. Furthermore, administration beta 1-blockade to SHR of different ages caused a greater fall in MAP and HR than in WKY, indicating an increased dependence upon the sympathetic nervous system in SHR with age.