Noninvasive Continuous Blood Pressure Measurement Research Articles

A comparison of non-invasive continuous finger blood pressure measurement (Finapres) with intra-arterial pressure during prolonged head-up tilt

Simultaneous intra-radial and non-invasive (Finapres, Ohmeda) blood pressures were compared during prolonged head-up tilt, in eight patients (mean age 49 years) with malignant vasovagal syncope. Twelve tilts were performed, of which eight resulted in vasovagal syncope. The mean bias (difference between Finapres and intra-arterial pressures) for systolic pressure was +0.7 mmHg (standard deviation 11.3 mmHg) and for diastolic pressure was +5.4 mmHg (standard deviation 7 mmHg). The within-tilt precision (standard deviation of the bias) of the non-invasive measurements varied between 2.9-12.4 mmHg (median 4.5 mmHg) for systolic comparisons, and 1.6-8.4 mmHg (median 4.4 mmHg) for diastolic comparisons. In all but one tilt highly significant positive increases in both systolic (median 7.1 mmHg) and diastolic bias (median 8.1 mmHg) occurred on tilt with respect to resting pre-tilt levels. Independent of the absolute level of agreement, the non-invasive measurements followed changes in intra-arterial pressure closely, with 89% of beat-to-beat changes in systolic pressure, and 95% of beat-to-beat changes in diastolic pressure followed to within +/- 2 mmHg. This study suggests that the Finapres is well suited for use during diagnostic tilt testing, demonstrating an acceptable within-tilt precision and closely following pressure changes during vasovagal syncope.

Cardiovascular reactivity to a new mental stress test: The maze test.

The response to the maze test was studied in 31 subjects on no medication, including seven subjects with mild essential hypertension. Beat-by-beat finger blood pressure (BP) was measured with a Finapres device. Pulse interval from which heart rate (HR) was derived was obtained from the BP signal. A period of 5 min baseline was used to define resting levels of systolic BP and HR using 20-s averaged values for the calculation of the 95% confidence limit of the two variables. The average test duration was 10 min. During this period a series of video-displayed mazes had to be solved with easy mazes preceding difficult ones. No subject had been exposed to the test before. The maximal BP elevation associated with the test was 27 mmHg. The HR response averaged 11 beats/min. Significant elevations were observed for half the test duration. No significant relationship between these two responses was observed and some subjects exhibited isolated systolic BP or HR responses. When indices obtained during this active mental stress were compared to resting values, positive correlations were observed. When the resting standard deviation (SD) of systolic BP was higher the systolic response was greater. A similar relationship was observed for HR. In addition, when the systolic BP level at rest was higher, the systolic BP reactivity index was greater. However, systolic BP or HR at baseline were not predictive of the systolic BP or HR responses. This study demonstrates the applicability of a new test to assess cardiovascular reactivity. The main advantage of non-invasive continuous BP measurement with the Finapres is the ability to provide variability indices in addition to the peak responses.

Noninvasive continuous blood pressure measurement during anaesthesia: A clinical evaluation of a method commonly used in measuring devices

The objective of the study was assess the utility during anaesthesia of noninvasive continuous blood pressure measurement techniques which use intermittent oscillometric blood pressure measurement for their calibration. The assessment was performed by comparing noninvasive blood pressure with intra-arterial blood pressure. The noninvasive blood pressure measurement device used for evaluation was the NCAT N-500 which uses tonometry for its continuous measurements. Fifteen patients were studied. In 10 patients the intra-arterial blood pressure curve (IBP) was recorded from the radial artery (radial artery group), and in 5 patients it was recorded from the brachial artery (brachial artery group). In all patients the oscillometrically calibrated tonometric blood pressure (OTBP) was recorded from the other arm. To discriminate between calibration dependent measurement error and tonometric measurement error, the OTBP signal was recalibrated against the IBP signal to get the intra-arterial calibrated tonometric pressure curve (ITBP). OTBP-IBP reflected the overall measurement error, ITBP-IBP the error of the tonometric measurement, and OTBP-ITBP the calibration dependent measurement error. According to criteria formulated in the discussion the accuracy and agreement of the ITBP-IBP measurements were clinical acceptable. Accuracy and agreement of OTBP-IBP and of OTBP-ITBP were not clinical acceptable. Correlation of dynamic behavior was lower for OTBP than for ITBP. A significant effect of site difference between calibration measurements and continuous measurements was not found. It is concluded that the approach of continuous noninvasive blood pressure measurement based on the combination of two different measurement methods, in which the continuous method is calibrated by the oscillometric method, lead to clinical unacceptable accuracy and agreement in the patient group studied.

Noninvasive continuous blood pressure measurement: A clinical evaluation of the Cortronic APM 770

The Cortronic APM 770 (Cortronic, Ronkonkoma, NY) is a commercial device that claims to measure blood pressure noninvasively and continuously with the use of a standard blood pressure cuff. The aim of our study was to assess the performance of the continuous-mode blood pressure readings of the Cortronic during anesthesia and surgery. We recorded blood pressure in 5 patients bilaterally. An interaarterial pressure (IAP) curve was recorded from 1 arm and the Cortronic pressure curve (CPC) was recorded from the other. For statistical analysis the period between 2 Cortronic recalibrations was defined as the intercalibration interval. The duration of these intervals ranged from 20 to 0.5 minutes. Four paired samples were drawn from each interval. The first sample in an interval represented the recalibration blood pressure; the other samples represented the continuous blood pressure. A total of 1,232 samples were taken, of which 308 were recalibration. The median of the differences and the 2.5th and 97.5th percentile limits of agreement were determined. Their respective values for diastolic and systolic recalibration measurements were 5, -17, and 34 mm Hg, and 6, -12, and 38 mm Hg. Their values for continuous measurements were 4, -23.5, and 32 mm Hg, and 6, -30, and 70 mm Hg. Changes in CPC were evaluated against changes in the corresponding IAP by plotting them in 4-quadrant graphs. In these graphs the Spearman rank correlations were between r = -0.17 and r = 0.01. We observed opposite CPC and IAP trends on 24 occasions during this study. We performed a simple simulation study to better understand the measurement method of the Cortronic.(ABSTRACT TRUNCATED AT 250 WORDS)

Twenty-Four-Hour Ambulatory Noninvasive Continuous Finger Blood Pressure Measurement with PORTAPRES

PORTAPRES model 1 is a portable 24 h continuous noninvasive blood pressure recorder based on the same principles as FINAPRES, the volume-clamp method of Peñaz and the physiocal criteria of Wesseling. In addition, PORTAPRES measures two adjacent fingers in alternation every 30 min and automatically corrects hydrostatic effects due to height changes of the measured fingers. The device measures 255 x 210 x 60 mm and weights about 3,000 g, including a lithium battery pack and a TEAC cassette FM instrumentation tape recorder to record the finger pressure wave form, the height signal, and beat-to-beat derived systolic, mean and diastolic pressure as well as heart rate. It appears to be an excellent new tool for cardiovascular research in humans. In a randomized, placebo-controlled, double-blind, crossover study the effect of oral administration of 2.5 mg cilazapril, a new potent long-acting, nonsulfhydryl-group angiotensin converting enzyme (ACE) inhibitor, given once daily for 7 days, was investigated in 16 healthy young men (mean age 25.3 +/- 1.6 years). Finger blood pressure and heart rate were measured with PORTAPRES for 24 h during everyday life and during standardized laboratory tasks, once about 1 to 2 h A.M. and once about 10 to 11 h P.M. once about 1 to 2 h A.M. and once about 10 to 11 h P.M. after drug administration. Physical activity was controlled by integrated thigh-EMG. Using stepwise multiple linear regression analysis it was shown that based on 64 s mean values, this measure of physical activity explains 34-77% of the heart rate variance within 24 h (median 53%), 10-52% (31%) of systolic, and 4-38% (25%) of diastolic blood pressure variance when up to 20 time lags of the EMG signal were introduced as possible predictors. This indicates that varying degrees of physical activity have a great impact on everyday blood pressure and heart rate. After one week cilazapril did not alter 24-h means of systolic and diastolic blood pressure or heart rate significantly, but reduced 30 min averages of both systolic and diastolic blood pressure by 6-10 and 4-6 mm Hg between 1 1/2 and 4 or 6 h after drug administration respectively during everyday life (p = 0.0067-0.066) without changing heart rate. On adjusting cardiovascular variables for the effects of physical activity, this blood pressure reduction was confirmed.(ABSTRACT TRUNCATED AT 400 WORDS)

Twenty-Four-Hour Ambulatory Noninvasive Continuous Finger Blood Pressure Measurement with PORTAPRES: A New Tool in Cardiovascular Research

Twenty-Four-Hour Ambulatory Noninvasive Continuous Finger Blood Pressure Measurement with PORTAPRES: A New Tool in Cardiovascular Research

Continuous direct and indirect blood pressure measurement (Finapres) in the critically ill

Continuous noninvasive blood pressure measurement is of great potential use in the critically ill. This study was designed to find out whether measurements of blood pressure by a Finapres accurately represented intra-arterial pressure. Comparisons were made between readings from a radial artery line and from a Finapres finger cuff in 10 critically ill patients. There was an unpredictable but usually stable difference between measurements from the two sources; this difference varied in magnitude and direction in individual patients. At present the Finapres cannot be recommended as a substitute for intra-arterial blood pressure measurement in the critically ill.

EFFECTS OF RESPIRATION ON BLOOD PRESSURE AND HEART RATE VARIABILITY IN HUMANS

1. Non-invasive continuous finger blood pressure (BP) measurement and a spectral technique based on the Fourier transform (FT) were recently combined to quantify short-term fluctuations in haemodynamic variables. 2. Systolic BP (SBP) recording combined low frequency (LF, Mayer waves) plus high frequency (HF, respiratory) oscillations. The presence of HF oscillations of SBP probably reflects fluctuations in cardiac output. Heart rate (HR) also exhibited a combination of low and HF (respiratory) oscillations. The vagus nerve mediates the efferent control of the respiratory sinus arrhythmia (RSA). 3. During controlled breathing in a supine position, a change in SBP is associated with an opposite consequent change in HR. Respiratory sinus arrhythmia could therefore depend on the baroreceptor-HR response to underlying SBP oscillations. 4. The fast regulation of R-R interval by SBP through the baroreceptor-HR reflex may explain why the respiratory variations in the diastolic BP are small.

Orthostatic Circulatory Control in the Elderly Evaluated by Non-Invasive Continuous Blood Pressure Measurement

1. Continuous orthostatic responses of blood pressure and heart rate were measured in 40 healthy and active elderly subjects over 70 years of age in order to assess the time course and rapidity of orthostatic cardiovascular adaptation in old age. 2. During the first 30 s (initial phase) the effects of active standing and passive head-up tilt closely resembled those observed earlier in younger age groups. Standing up was accompanied by a drop (mean +/- SD) in systolic and diastolic blood pressures of 26 +/- 13 mmHg and 12 +/- 18 mmHg, respectively, at around 10 s, and a subsequent rise up to 11 +/- 17 mmHg and 8 +/- 6 mmHg above supine values at around 20 s. The drop in blood pressure upon standing was accompanied by a transient increase in heart rate with a maximum of 13 beats/min, followed by a gradual decrease to 7 beats/min above supine levels. These characteristic transient changes were absent upon a passive head-up tilt. 3. After 1-2 min of standing (early steady-state phase) diastolic blood pressure and heart rate increased significantly after active and passive postural changes. On average, for all subjects systolic blood pressure tended to increase from control during 5-10 min standing, reaching a significant difference at 10 min. During standing, the largest increases in systolic blood pressure were found in subjects with the lowest supine blood pressures. 4. In conclusion, for the investigation of orthostatic circulatory responses in elderly subjects the following factors have to be taken into account: active versus passive changes in posture, the timing of the blood pressure reading, and the level of supine blood pressure.

Non-invasive continuous finger blood pressure measurement during orthostatic stress compared to intra-arterial pressure

The aim of the study was to evaluate whether invasive blood pressure responses to orthostatic stress can be replaced by non-invasive continuous finger blood pressure responses. DESIGN - Intrabrachial and Finapres blood pressures were simultaneously measured during passive head up tilt and during active standing from the supine or sitting position in healthy volunteers. Subjects (n = 11) were healthy males aged 22-40 years, mean age 30 years. Beat to beat values of systolic, diastolic, and mean arterial pressures were calculated for both methods of measurement and the differences compared during a 30 s control period before, and during the first 120 s after, the change of posture. In the control period the difference between finger pressure and intra-arterial pressure was +2 (SD11) mm Hg for systolic, -4(8) mm Hg for mean, and -3(7) mm Hg for diastolic pressure. Compared to these control differences, the average finger minus intra-arterial pressure differences for mean and diastolic pressures during the three orthostatic manoeuvres were always within the range -6 to +6 mm Hg. The average systolic deviations were larger, ranging from -10 to +11 mm Hg. Despite these differences the characteristic changes in intra-arterial pressure during the initial phase (first 30 s after change of posture), as well as during the early steady state phase (1-2 min after the change of posture) were well reflected by finger pressure measurements in all subjects. For the assessment of the continuous blood pressure responses to orthostatic stress similar information can be obtained with non-invasive Finapres blood pressure recordings as with invasive recordings.

Monitoring the cardiovascular system: Current status and future directions

Monitoring the circulation of the patient with cardiac disease is of necessity a complex task. Decreased cardiac performance is attended by a higher incidence of undesirable perioperative outcomes. Early detection of inadequate cardiac performance is essential in minimizing complications and facilitating optimal patient care. The foundation of modern cardivascular monitoring is a thorough understanding of cardiac function and the determinants of cardiac performance-heart rate, afterload, preload, and contractility. Monitoring of these variables is the goal of current techniques including echocardiography and radionuclear studies. While the current trend is toward non-invasive acquisition of haemodynamic data, invasive techniques such as pulmonary artery catheterization remain the mainstay of sophisticated assessment. However, cardiac ultrasound with its potential for measurement of regional and global cardiac function is undergoing rapid development as an intraoperative monitor. The technique of trans-oesophageal echocardiography is well suited to the non-invasive acquisition of physiological data. The widespread application of this newer technology faces the significant, barriers of high cost and the requirement for significant training. Other important advances include continuous non-invasive blood pressure measurement. This technique, based on the plethysmographic principle, provides a wave-form which correlates with invasive gold standards for arterial pressure measurement. While present devices do not have universal applicability, this technology with refinement may make arterial cannulae unnecessary in most circumstances. Overall, the anaesthesiologist has available a variety of monitoring options to acquire the necessary information to support the surgical patient with cardiac disease during the perioperative period.

Noninvasive Continuous Blood Pressure Measurement from the Finger

Noninvasive Continuous Blood Pressure Measurement from the Finger