Continuous Non-invasive Finger Blood Pressure Research Articles

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

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.

Continuous Noninvasive Finger Blood Pressure during Controlled Hypotension A Comparison with Intraarterial Pressure

The Finapres is a noninvasive monitor that continuously displays the arterial waveform, pulse rate, and systolic, mean, and diastolic blood pressure. We determined its bias (mean prediction error) and precision (mean absolute error), relative to directly measured radial arterial blood pressure, in 16 otherwise healthy patients undergoing spinal fusion surgery under hypotensive anesthetic techniques. Data were recorded during three contiguous epochs: 20 min of normotension; 30 min following the initiation of hypotension; 20 min of hypotension. The Finapres demonstrated a systolic, mean, and diastolic bias (+/- standard deviation) of 3.6 +/- 12.3, 5.2 +/- 10.8, and 8.3 +/- 9.4 mmHg, respectively. There were no significant differences in systolic bias among the epochs, whereas mean and diastolic bias were both greater during the hypotensive epoch, compared to the normotensive epoch. In 2 of the 16 patients, systolic and mean arterial pressure bias exceeded 20 mmHg. Finapres precisions of systolic, mean, and diastolic blood pressures were 9.8 +/- 9.0, 8.7 +/- 7.6, and 10.4 +/- 8.2 mmHg, respectively. Precisions among the epochs were not significantly different. When Finapres pressures were "corrected" by subtracting the baseline difference between Finapres and oscillometrically determined mean pressure, bias decreased significantly. The correction process did not improve precision. The Finapres closely tracked changes in blood pressure, even in the presence of a large bias. In most patients, the Finapres is a useful continuous noninvasive blood pressure monitor. Periodic calibration of the Finapres by the difference between Finapres and oscillometrically determined mean arterial pressure is recommended.

Cardiac baroreflex function during postural change assessed using non-invasive spontaneous sequence analysis in young men

The aim was to assess the value of baroreflex sensitivity estimates calculated from analyses of spontaneous systolic blood pressure and pulse interval sequences derived from continuous non-invasive finger blood pressure recordings during sitting and active standing. Continuous recordings of digital systolic blood pressure and pulse interval were obtained non-invasively using a Finapres FD5 during 5 min trials of sitting and standing. Subjects were healthy males aged 19-28, divided into those with "high" normal (n = 18) and "low" normal (n = 17) blood pressure. Recordings were scanned for spontaneous sequences of three or more cardiac cycles over which systolic blood pressure increased progressively in conjunction with prolonged pulse interval, or decreased while pulse interval became shorter. Regressions between blood pressure and pulse interval (r greater than 0.80) provided estimates of cardiac baroreceptor reflex control. Computations were carried out with concurrent blood pressure and pulse interval measurements, and with a delay or lag of one and two cycles between the two variables. Pulse interval was reduced from an average 870.3 ms sitting to 571.3 ms on standing. Mean baroreflex sensitivity while sitting averaged 17.5 ms.mm Hg-1 at a delay of one cycle, failing to 7.65 ms.mm Hg-1 with standing. The decrease in sensitivity was correlated with the change in pulse interval between trials. The number of sequences was also significantly reduced with standing as opposed to sitting. Three cycle sequences were most frequent, with a lesser number of sequences involving 4, 5, and 6 or more cycles. No significant differences between "high" and "low" normal blood pressure groups were observed. The analysis of spontaneous sequences from non-invasive recordings may provide useful information concerning cardiac baroreflex control in different postural and behavioural states. A lag of one cycle between systolic blood pressure and pulse interval may provide the most representative estimates of baroreflex sensitivity.

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.

Comparison of finger and intra-arterial blood pressure monitoring at rest and during laboratory testing.

The accuracy of blood pressure values obtained by continuous noninvasive finger blood pressure recording via the FINAPRES device was evaluated by comparison with simultaneous intraarterial monitoring both at rest and during performance of tests known to induce fast and often marked changes in blood pressure. The comparison was performed in 24 normotensive or essential hypertensive subjects. The average discrepancy between finger and intra-arterial blood pressure recorded over a 30-minute rest period was 6.5 +/- 2.6 mm Hg and 5.4 +/- 2.9 mm Hg for systolic and diastolic blood pressure, respectively; a close between-method correspondence was also demonstrated by linear regression analysis. The beat-to-beat changes in finger systolic and diastolic blood pressure were on average similar to those measured intra-arterially during tests that induced a pressor or depressor response (hand-grip, cold pressor test, diving test, Valsalva maneuver, intravenous injections of phenylephrine and trinitroglycerine) as well as during tests that caused vasomotor changes without major variations in blood pressure (application of lower body negative pressure, passive leg raising). The average between-method discrepancy in the evaluation of blood pressure changes was never greater than 4.3 and 2.0 mm Hg for systolic and diastolic blood pressure, respectively; the corresponding standard deviations ranged between 4.6 and 1.6 mm Hg. Beat-to-beat computer analysis of blood pressure variability over the 30-minute rest period provided standard deviations almost identical when calculated by separate consideration of intra-arterial and finger blood pressure tracings (3.7 and 3.8 mm Hg, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)