Antonella Groppelli

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 diastoiic blood pressure, respectively; a close between-method correspondence was also demonstrated by linear regression analysis. The beat-to-beat changes in finger systolic and diastoiic 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 diastoiic 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). The two methods of blood pressure recording also allowed similar assessments of the sensitivity of baroreceptor control of heart rate (vasoactive drug injections) and blood pressure (neck chamber technique) to be obtained. Thus, beat-to-beat blood pressure recording via FINAPRES provides an accurate estimate of means and variability of radial blood pressure in groups of subjects and represents in most cases an acceptable alternative to invasive blood pressure monitoring during laboratory studies.

Evaluation of the baroreceptor-heart rate reflex by 24-hour intra-arterial blood pressure monitoring in humans.

The baroreceptor control of the sinus node was evaluated in 10 normotensive and 10 age-matched essential hypertensive subjects in whom ambulatory blood pressure was recorded intraarterially for 24 hours and scanned by a computer to identify the sequences of three or more consecutive beats hi which systolic blood pressure (SBP) and pulse interval (PI) progressively rose (+ PI/ + SBP) or fell (− PI/ −SBP) in a linear fashion, according to a method validated in cats. In normotensive subjects, several hundred +PI/+SBP and −PI/−SBP sequences of 3 beats were found whereas the number of sequences of 4,5, and more than 5 beats showed a progressive drastic reduction. The mean slopes of plus; PI/ + SBP (7.6 ± 2.0 msec/mm Hg) and − PI/− SBP (6.4 ± 1.5 msec/mm Hg) sequences were similar, but in both instances there was a large scattering of the values around the mean (variation coefficients: 64.2 ± 4.7 and 62.6 ± 2.4%). The slopes decreased as a function of the sequence length and baseline heart rate and increased to a marked extent during the night as compared with daytime values. All sequences were more rare (−33.2% for +PI/ + SBP and −31.7% for −PI/−SBP) and less steep in hypertensive subjects (−40.3 and −36.2%, respectively), who failed to show the marked nighttime increase in slope observed in normotensive subjects. To our knowledge, these observations provide the first description in humans of the baroreceptor-heart rate reflex in daily life. This reflex is characterized by marked within-subject variations hi sensitivity due in part to hemodynamic, temporal, and behavioral factors. All features of the baroreceptor-heart rate reflex are unpaired hi essential hypertension.

Persistent blood pressure increase induced by heavy smoking

OBJECTIVE To test the hypothesis that heavy smoking is associated with a persistent increase in blood pressure. DESIGN In 10 normotensive smokers asked to smoke one cigarette every 15 min for 1 h, blood pressure and heart rate were continuously monitored during the smoking period and during the preceding non-smoking hour. In six other normotensive smokers asked to smoke two cigarettes per hour throughout the whole day, blood pressure and heart rate were monitored non-invasively in ambulatory conditions for 8 h (0900-1700 h). Blood pressure monitoring was repeated during a non-smoking day. METHODS Beat-to-beat blood pressure and heart rate were monitored at rest by means of the Finapres device. Blood pressure signal was sampled at 165 Hz by a computer to calculate hourly data. Ambulatory blood pressure and heart rate were measured once every 10 min. RESULTS In resting conditions, the first cigarette caused an immediate and marked increase in blood pressure and heart rate, and the peak blood pressure and heart rate achieved were similar for the remaining three cigarettes. In each instance, the hemodynamic effects were so prolonged that throughout the smoking hour, blood pressure and heart rate were persistently higher than during the non-smoking hour. The standard deviations of systolic and diastolic blood pressure and heart rate were also higher during the smoking hour, indicating an increase in blood pressure and heart rate variability. In the six ambulant smokers, daytime blood pressure and heart rate were also persistently higher during smoking than during non-smoking. CONCLUSIONS Heavy smoking is associated with a persistent rise in blood pressure and also with an increase in blood pressure variability. These effects (which may escape clinic blood pressure measurements performed during non-smoking) may account for some of the smoking-related cardiovascular risk.

Evaluation of noninvasive blood pressure monitoring devices Spacelabs 90202 and 90207 versus resting and ambulatory 24-hour intra-arterial blood pressure.

This study evaluated the accuracy of blood pressure values provided by the Spacelabs 90202 and 90207 devices in comparison with intra-arterial recording in 19 subjects at rest and in nine subjects in ambulatory conditions (Oxford method). At rest Spacelabs monitors reflected intra-arterial systolic blood pressure values very closely but overestimated to a considerable extent intra-arterial diastolic blood pressure (Spacelabs-intra-arterial differences, -0.8 +/- 9.2, NS, and 9.1 +/- 8.8 mm Hg, p less than 0.01, for systolic and diastolic blood pressures, respectively). In ambulatory conditions Spacelabs-intra-arterial average differences in 24-hour values were +0.4 +/- 5.1 mm Hg for systolic blood pressure (NS) and +14.0 +/- 2.9 mm Hg for diastolic blood pressure (p less than 0.01) when group data were considered. The performance of both Spacelabs devices was worse when assessed in individual subjects or for each hourly interval. In spite of these differences between noninvasive and intra-arterial absolute blood pressure values, however, Spacelabs 90202 and 90207 monitors were able to faithfully reflect directional hour-to-hour changes in intra-arterial blood pressure (chi 2 = 18.2 and chi 2 = 23.1 for systolic and diastolic blood pressures, respectively, p less than 0.01). No differences were found between the performance of the two Spacelabs devices. Thus, although the absolute accuracy of blood pressure values provided by these monitors in ambulatory subjects is still limited, they seem to be suitable for studies aimed at assessing 24-hour blood pressure profiles quantitatively as well as qualitatively.

Validation of the Omron M5-I, R5-I and HEM-907 automated blood pressure monitors in elderly individuals according to the International Protocol of the European Society of Hypertension.

ObjectiveThis study aimed at verifying the accuracy of three automated electronic oscillometric blood pressure measuring devices, namely Omron M5-I (home use upper arm monitor), R5-I (home use wrist monitor) and HEM-907 (professional use upper arm monitor) according to the European Society of Hypertension International Protocol in elderly individuals. MethodsSequential measurements of systolic and diastolic blood pressure were obtained in 33 participants (aged ≥75 years) using the mercury sphygmomanometer (two observers) and each of the tested devices (one supervisor). A standard adult cuff was always employed during the study because all participants had an arm circumference compatible with such a cuff. According to the European Society of Hypertension validation protocol 99 couples (three pairs per patient) of test device and reference blood pressure measurements were obtained during phase 1 (15 participants studied) and phase 2 (a further 18 participants) for each electronic monitor. ResultsAll devices successfully passed the validation study with a mean (±SD) device−observer difference for systolic and diastolic blood pressure of 0.2±3.6/0.2±3.9 mmHg (Omron M5-I), −1.5±6.2/−0.7±3.7 mmHg (Omron R5-I), and 0.1±5.1/−1.9±4.2 mmHg (Omron HEM-907). SD of the mean difference was lower and thus the precision was better for diastolic than for systolic blood pressure, and for the Omron M5-I than for the other two devices. ConclusionsAccording to the results of the validation study based on the European Society of Hypertension International Protocol the Omron M5-I, R5-I, and HEM-907 may be recommended for clinical use in elderly individuals, without atrial fibrillation or frequent ectopic beats.

24-Hour blood pressure monitoring: Evaluation of Spacelabs 5300 monitor by comparison with intra-arterial blood pressure recording in ambulant subjects

The accuracy of 24-h blood pressure values obtained by ambulatory monitoring via the Spacelabs 5300 device was evaluated by comparison with simultaneous 24-h intra-arterial blood pressure recording from the contralateral arm. The comparison was made in eight essential hypertensive subjects in whom non-invasive blood pressure was measured every 15 (day) or 30 min (night). The measurements were automatically and visually edited to eliminate artefactual readings and hourly and 24-h means were calculated separately for systolic and diastolic blood pressure. The corresponding intra-arterial blood pressure means were also calculated. In the group as a whole, hourly means obtained by the non-invasive device were similar or only slightly different from those recorded intra-arterially. The 24-h systolic blood pressure mean obtained non-invasively was not significantly different from that obtained intra-arterially (138.4 +/- 9.1 and 142.9 +/- 9.2 mmHg, respectively), nor were the corresponding 24-h diastolic blood pressure means significantly different (83.5 +/- 4.5 and 80.6 +/- 3.5 mmHg, respectively). However, in spite of these similarities, there were contrasting and often large discrepancies between non-invasive and intra-arterial values in individual subjects. For the 24-h systolic blood pressure mean the discrepancies ranged from 7.6 +/- 1.1 to 16.1 +/- 2.2 mmHg and for the 24-h diastolic blood pressure mean, from 3.5 to 13.2 mmHg. Thus, the Spacelabs 5300 device has a limited ability to correctly estimate ambulatory blood pressure in individual subjects. It may be better suited for the estimation of group blood pressures, but only because errors are smoothed by the summation of individual errors of opposing signs.

Assessment of overall blood pressure variability and its different components

Blood pressure (BP) is characterized by continuous fluctuations, including fast changes lasting only a few seconds as well as slower and more prolonged variations, with a time constant of minutes or hours. Assessing the relative contribution of these different components to overall blood pressure variance is now possible through a number of mathematical approaches, either in the time or in the frequency domain (spectral analysis). Due to its complex nature, a precise and detailed assessment of blood pressure variability can be obtained only from the analysis of continuous, beat-by-beat, blood pressure recordings. Some information, however, can also be derived from analysis of discontinuous blood pressure tracings, such as those commonly performed in a clinical setting. This would require that attention is paid both to the quality of the recordings and to the selection of suitable analysis methods that should cope with the discontinuous nature of the measurements to be processed and to their intrinsic low sampling frequency.

Role of heart rate variability in the production of blood pressure variability in man.

In both normotensive and hypertensive subjects blood pressure (BP) and heart rate (HR) show concordant changes over 24 h. This may depend on a central factor exerting influences of the same nature on cardiac and vascular targets. An alternative explanation, however, is that a cause-effect relationship links these variabilities, i.e. that HR variations induce BP changes [presumably via variations in cardiac output (CO)]. Blood pressure was recorded intra-arterially in five supine and five exercising (walking) essential hypertensive subjects during a control period of 1 h and during an additional hour in which atropine, 0.04 mg/kg body weight, was injected intravenously (i.v.). The same recordings were performed in seven other subjects, in which saline rather than atropine was employed. One-hour BP and HR variabilities (variation coefficients, VC) were computer analysed. In both the supine and the exercising subjects atropine caused a marked reduction in HR VC (-65.3 and -48.4%, respectively). In the supine subjects this reduction was accompanied by only a modest reduction in BP VC whereas in the exercising subjects the BP VC increased by 30.4%. In the seven subjects in which saline was injected no change in BP and HR VC occurred. Thus a marked reduction in HR variability is not accompanied by a comparable attenuation in BP variability, which rules out a cause-effect link between these two phenomena. Indeed, during physical exercise HR stabilization is followed by an increase rather than a reduction in BP variation, which supports the conclusion that under some circumstances HR plays an anti-oscillatory role.

Cardiovascular effects of smoking

Coronary heart disease (CHD) increases with smoking and this factor interacts with hypercholesterolemia and hypertension in raising the incidence of this condition in a greater than linear fashion. This can be explained by the adverse effect of smoking on plasma fibrogen, platelet turnover and lipid profile. It may also be accounted for, however, by the acute bradycardia, increase in blood pressure and generalized vasoconstriction accompanying smoking, due to a nicotine-dependent activation of the sympathetic nervous system. These effects (which in heavy smokers can raise blood pressure permanently) are only partly offset by beta-blockers and can only be abolished by opposing the cardiac and vascular sympathetic influences by alpha and beta-blockade combined.

Variable day/night bias in 24-h non-invasive finger pressure against intrabrachial artery pressure is removed by waveform filtering and level correction

Background Twenty-four-hour finger arterial pressure (FAP) recordings show a negative bias against intrabrachial artery pressure (BAP) and the bias is greater during the night, thereby overestimating the nocturnal blood pressure dip. We have available a methodology with which to reconstruct BAP from FAP by waveform filtering (transfer function) and generalized level (bias) correction that reduces the bias for short-term blood pressure records. Objective To investigate if this methodology also decreases the extra bias during the night, thereby yielding a better estimate of the nocturnal dip. Methods Twenty-four-hour FAP and BAP blood pressure recordings were simultaneously obtained in eight healthy normotensive volunteers and 14 patients with hypertension (ages 19–60 years), during standardized scheduled activities. The data were analysed off-line, applying the brachial reconstruction technique (reBAP) consisting of a waveform filter and level correction. Simultaneous beats yielded systolic, diastolic and mean pressures that were averaged per 30 min, per day, per night, per activity, over the 24-h period, and for volunteers and patients separately. Results Over the full 24 h, FAP systolic, diastolic and mean values for the total group differed from BAP by +1 ± 10, −8 ± 7 and −10 ± 8 mmHg (mean ± SD), respectively. Similarly, reBAPs differed by +1 ± 11, −2 ± 7 and −2 ± 7 mmHg. BAPs dipped by 20 ± 8, 13 ± 6 and 15 ± 6 mmHg, respectively, during the night. These dips were overestimated by +8, +4 and +4 mmHg by FAP, but not by reBAP: −1, +1 and +1 mmHg. The volunteer and the patient groups showed slight differences in results, but these were not statistically significant. Conclusions The generalized reconstruction technique to obtain near-brachial pressure from non-invasive FAP almost completely removed bias over the full 24-h day–night period and improved tracking of diurnal changes for all three blood pressure values.