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G Parati

Publications and source records attributed to G Parati.

At least 127 records · Page 7Linked to original sources
PubMed1993

Feasibility of ambulatory, continuous 24-hour finger arterial pressure recording.

We tested Portapres, an innovative portable, battery-operated device for the continuous, noninvasive, 24-hour ambulatory measurement of blood pressure in the finger. Portapres is based on Finapres, a stationary device for the measurement of finger arterial pressure. Systems were added to record signals on tape, to alternate measurements between fingers automatically each 30 minutes, and to correct for the hydrostatic height of the hand. We compared the pressure as measured by Portapres with contralateral intrabrachial pressure measured with an Oxford device. Results were obtained in eight volunteers and 16 hypertensive patients. Time lost due to artifact was about 10% for each device. In two patients a full 24-hour Oxford profile was not obtained. In the remaining 22 subjects finger systolic, diastolic, and mean pressures differed +1 (SD 9), -8 (6), and -10 (6) mm Hg, respectively, from intrabrachial pressure. These diastolic and mean pressure underestimations are similar to what was found earlier for Finapres, are typical for the technique, and are systematic. Avoiding brisk hand movements resulted in fewer waveform artifacts. The hand had to be kept covered to continue recording at low outside temperatures. Sleep was not disturbed by Portapres, and arterial pressure showed a marked fall during siesta and nighttime. There were no major limitations in behavior, and no discomfort that originated from continuous monitoring was reported. Measurements continued normally during physical exercise. Portapres provides for the first time continuous 24-hour, noninvasive ambulatory blood pressure waveform monitoring and offers real and obvious advantages over current noninvasive and invasive devices.

Adult↗
PubMed1993

Spectral and sequence analysis of finger blood pressure variability. Comparison with analysis of intra-arterial recordings.

The aim of our study was to assess whether the Finapres device is able to accurately monitor not only average blood pressure values but also blood pressure variability. To examine this issue, we analyzed 30-minute recordings of finger and intra-arterial pressure simultaneously obtained at rest in 14 patients. We compared systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse interval (the reciprocal of heart rate), overall variability (standard deviation), and specific time-domain and frequency-domain components. Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse interval spectral powers were computed by fast Fourier transform over three frequency bands: low frequency (0.025 to 0.07 Hz), midfrequency (0.07 to 0.14 Hz), and high frequency (0.14 to 0.35 Hz). The coherence, ie, the degree of association between blood pressure and pulse interval powers obtained by the two techniques, was also assessed. Standard deviations of diastolic blood pressure, mean arterial pressure, and pulse interval were similar when assessed from the two recordings, whereas standard deviation of systolic blood pressure was overestimated by analysis of finger pressure recordings. All powers of diastolic blood pressure and mean arterial pressure and high-frequency powers of systolic blood pressure estimated from analysis of finger blood pressure tracings were superimposable to those obtained by analyzing invasive recordings. Low-frequency and midfrequency powers of intra-arterial systolic blood pressure were significantly overestimated by the analysis of finger blood pressure tracings (+13.7 +/- 4.4 mm Hg2, P < .01, and +2.3 +/- 0.9 mm Hg2, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Evaluating sympathetic activity in human hypertension.

AIM: To review the use of plasma norepinephrine to evaluate sympathetic activity in humans, and to discuss the improvement in assessment of human sympathetic activity brought about by the norepinephrine spillover method and by microneurography. METHOD: Literature survey. RESULTS: These methods have limitations, and an accurate assessment of sympathetic cardiovascular control should not be limited to an investigation of sympathetic nerve firing or norepinephrine secretion but include cardiac and vascular responses. These responses can be assessed by traditional pharmacological means (for example, a reduction in vascular resistance induced by alpha-adrenergic blockade) or by a variety of approaches aimed at examining sympathetic cardiovascular modulation in a more integrated fashion, such as the recently developed power spectrum analysis of blood pressure and heart rate. CONCLUSION: The sensitivity and specificity of all these methods is still under investigation, but in almost every case an increase in sympathetic cardiovascular influence has been reported to occur in hypertension, indicating that sympathetic activation has a pathogenic effect on this condition.

Blood Pressure↗
PubMed1993

Spectral analysis of 24 h blood pressure recordings.

Spectral analysis of blood pressure and heart rate signals allows overall blood pressure and heart rate variabilities to be split into their different frequency components. When used to analyze 24 h discontinuous blood pressure recordings, the low sampling frequency that characterizes these devices allows only the slow fluctuations in day and night blood pressure to be adequately described by the spectral approach. Conversely, spectral analysis of continuous blood pressure recordings provides information both on fast and slow changes in blood pressure and heart rate. Because blood pressure and heart rate powers are characterized by a 1/f distribution over the 24 h, slow fluctuations in blood pressure and heart rate contribute most importantly to 24 h variance, while faster components provide only a minor contribution. However, spectral analysis of the latter has raised considerable interest due to the possible association of these components with cardiovascular regulatory mechanisms. It is now possible to perform 24 h dynamic spectral analysis of blood pressure and heart rate on continuous blood pressure recordings obtained noninvasively by a finger pressure device.

Blood Pressure↗
PubMed1993

Ambulatory blood pressure monitoring in the design of studies on antihypertensive drug efficacy.

Ambulatory blood pressure monitoring (ABPM) provides advantages for studies of the efficacy of antihypertensive drugs in addition to demonstrating antihypertensive effects in daily life conditions. For example, ABPM is devoid of the "white coat" effect and can thus more precisely estimate the relative proportion of responders and nonresponders to treatment. It also may reduce the study size because of the greater reproducibility of 24 h average blood pressure (BP) (as compared to clinic BP) and the lack of a substantial placebo effect, which eliminates the need for a placebo group. Some disadvantages exist, including the inability of automatic ABPM to consistently provide accurate BP readings and to estimate BP variability. Finally, hourly average BPs are less reproducible than their average 24 h counterpart, which may make it more difficult to statistically demonstrate an antihypertensive effect throughout the 24 h. Some of these disadvantages, however, may be reduced in the near future by new ABPM devices.

Ambulatory Care↗
PubMed1993

Ambulatory blood pressure monitoring in elderly hypertensive patients.

Ambulatory blood pressure monitoring (ABPM) has been shown to provide a reliable estimation of hourly blood pressure values over the 24 hours. Favourable features of this technique are the lack of alerting reaction to automatic blood pressure readings, at variance from what usually occurs when blood pressure is measured in the doctor's office, and the ability of ABPM to provide information on the 24 hour blood pressure profile without interfering with the physiological nocturnal hypotension. Although automatic blood pressure readings obtained in free-moving subjects are not always accurate, ABPM has been shown to represent a useful approach to evaluate the efficacy of antihypertensive drugs, as it allows to compare the 24 hour blood pressure profile obtained before and during treatment. Its feasibility to this aim is emphasized by the reproducibility of 24 hour ambulatory blood pressure profiles, which do not show any placebo effect. ABPM has been also employed to investigate 24 hour blood pressure fluctuations and to monitor the antihypertensive treatment in elderly hypertensives, in whom the evaluation of the actual time-course of the drug-induced blood pressure reduction over the day and night represents a crucial problem.

Aged↗
PubMed1992

Clinical value of blood pressure measurements: focus on ambulatory blood pressures.

Because clinic blood pressure values are compromised by 2 major limitations--the alerting reaction to clinic measurements and the spontaneous blood pressure variability--they have only a limited correlation with average 24-hour blood pressure values. Whether the latter should be employed routinely in substitution for, or in addition to, traditional blood pressure measurements has not yet been determined, however. To date, average 24-hour blood pressure values have been shown to correlate more closely than clinic blood pressure values with the organ damage of hypertension. A correlation with organ damage has been shown also for a number of blood pressure values within the 24 hours. Nevertheless, the clinical importance of 24-hour blood pressure and blood pressure variability has never been confirmed by prospective controlled studies. This information needs to be obtained before this approach is routinely employed in the clinical practice.

Ambulatory Care↗
PubMed1992

Noninvasive automatic blood pressure monitoring does not attenuate nighttime hypotension. Evidence from 24 h intraarterial blood pressure monitoring.

Automatic ambulatory blood pressure monitoring makes use of repeated cuff inflations throughout the day and night. This may interfere with the cardiovascular effects of sleep and thus alter the 24 h blood pressure profile. The possibility that intermittent automatic blood pressure measurements prevent nocturnal hypotension was examined in 17 mild or moderate essential hypertensive patients in whom blood pressure was recorded intraarterially for 48 h by the Oxford technique. During the first or the second 24 h period, blood pressure was also monitored noninvasively by the SpaceLabs (Redmond, WA) 5300 (n = 10) and by the Sandoz Pressure System SPS 1558 (Lavanchy Electronique, Prilly, Switzerland) (n = 7) devices, automatic measurements being performed at 15 min intervals during the day and at 30 min intervals during the night. Separate computer analysis of 24 h intraarterial tracings obtained in absence and in concomitance of contralateral automatic blood pressure monitoring showed that the occurrence of automatic measurements had not interfered with the day-night intraarterial blood pressure and heart rate profiles. Thus the frequent cuff inflations that characterize automatic blood pressure monitoring do not attenuate nighttime hypotension and bradycardia. This finding supports use of the noninvasive approach in assessing blood pressure profiles.

Adult↗
PubMed1992

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.

Adult↗
PubMed1992

Limited reproducibility of hourly blood pressure values obtained by ambulatory blood pressure monitoring: implications for studies on antihypertensive drugs.

OBJECTIVE: To assess the reproducibility of average hourly blood pressure values obtained by 24-h non-invasive ambulatory monitoring. PATIENTS: Fifteen outpatients with essential hypertension. In all subjects antihypertensive treatment was withdrawn for 4 weeks before and during the 4 weeks of the study. METHODS: The 24-h blood pressure was monitored by a SpaceLabs 5300 device (four readings per hour during the day and three readings per hour during the night) twice, at a 4-week interval. Systolic (SBP) and diastolic blood pressure (DBP) were averaged for each hour and for the whole 24-h period, and hourly and 24-h reproducibility was quantified by the standard deviation of the mean difference (SDD) between the values obtained in the two recordings. RESULTS: The SDD of hourly SBP and DBP was much greater than that of the 24-h values and ranged widely between the hours of recording. The SDD of hourly SBP and DBP were also variably greater than the SDD of the 24-h value in another 14 untreated essential hypertensives in whom 24-h ambulatory blood pressure was monitored intra-arterially twice at a 4-week interval to calculate hourly average blood pressure on thousands rather than on three or four values per hour. CONCLUSION: Reproducibility is less for hourly than for 24-h average blood pressure. This feature (which probably depends on behavioural differences between two recordings) suggests that ambulatory blood pressure measurement partly loses its advantages for reproducibility and reduction in trial size if the results are analysed over hourly periods.

Adolescent↗
PubMed1992

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.

Adolescent↗
PubMed1992

Changes in 24 hour blood pressure and in cardiac and vascular structure in normotensive subjects with parental hypertension.

Subjects with family history of hypertension represent a suitable model to investigate the mechanisms responsible for early cardiovascular structural and functional changes occurring in essential hypertension. In our study we have addressed the factors involved in determining the mild elevation in office blood pressure frequently observed in normotensive subjects with hypertensive parents. In 15 normotensive subjects with both parents hypertensive (FH++) and in 15 normotensive subjects with one parent hypertensive (FH(+)-) we found no evidence of a hyperreactivity to stress as compared to the responses of 15 normotensive subjects with no parental hypertension (FH--). On the contrary FH++ subjects were characterized by a significant although mild increase in their blood pressure values recorded either at rest and in ambulatory conditions over the 24 hours, including night sleep. FH++ and FH(+)- subjects also showed a greater left ventricular mass thickness and a greater minimal forearm vascular resistance than FH-- subjects. Thus, the elevation in blood pressure found in the pre-hypertensive stage in subjects with positive family history for hypertension does not reflect a hyperreactivity to the stress associated with physician's visit but indicates an early and persistent blood pressure elevation. This blood pressure elevation is accompanied by early cardiovascular structural changes which may indicate that these subjects are exposed to a higher risk even before developing overt hypertension.

Adult↗
PubMed1992

Effects of graded vasoconstriction upon the measurement of finger arterial pressure.

OBJECTIVE: To assess the effects of incremental phenylephrine infusion rates and subsequent graded vasoconstriction upon the performance of the Ohmeda Finapres. DESIGN: Blood pressure in eight hypertensive patients in the finger and the brachial artery was recorded simultaneously. Systolic blood pressure (SBP), diastolic blood pressure (DPB) and mean arterial pressure (MAP) were compared as well as additional waveform characteristics like the pressure at moment of the dicrotic notch and calculation of the pulsatile-systolic areas. RESULTS: Before phenylephrine infusion SBP and DBP were higher in the finger. At maximal infusion (1.6 micrograms/kg/min) the increase in brachial SBP was significantly underestimated by Finapres. Thus, the computed sensitivities of baroreflex control for SBP differed significantly between the two measurements. Under control conditions, the shape of the finger waveform differed from the brachial-artery waveform in terms of: (1) a more peaked appearance; (2) a dicrotic notch (Pnotch) which is located at a lower percentage of pulse pressure; and (3) a larger pulsatile-systolic area. At maximal infusion rates finger Pnotch increased whilst intrabrachial Pnotch did not. In contrast, the brachial and finger pulsatile-systolic areas changed fully in parallel. CONCLUSIONS: Phenylephrine infusion caused a significant, and clinically important, underestimation of the increase in brachial SBP when assessed by Finapres, whereas MAP and DBP and pulsatile-systolic area track intra-arterial pressure reliably.

Arteries↗
PubMed1992

Twenty-four hour blood pressure monitoring and end-organ damage.

Ambulatory blood pressure monitoring (ABPM) over 24 hours has become quite common. Evidence suggests that the mean 24-hour measurement is more closely associated with end organ damage, including end-points such as left ventricular hypertrophy (LVH), than is a single blood pressure measurement taken in the doctor's office. Clinicians disagree about the particular significance of blood pressure measurements obtained during exercise, blood pressure variability, and blood pressure load (a measurement above 140/90 over 24 hours). However, the morning peak in blood pressure appears to be associated with the highest incidence of coronary events, and end organ damage may be greater in subjects in whom nocturnal blood pressure falls only slightly from a diurnal baseline (non-dippers). From now, ABPM serves mainly as a research tool. Longitudinal controlled studies are needed to compare the value of ABPM to office blood pressure readings in terms of how these measurements can predict cardiovascular end-points or, more realistically, surrogate end-points, such as the development or regression of LVH.

Blood Pressure Determination↗
PubMed1992

Twenty-four-hour blood pressure and antihypertensive treatment.

Normal values for 24-hour blood pressure (BP) have not been well characterized. However, it is believed that the maintenance of normal blood pressure control is a desirable feature of an antihypertensive agent. This is particularly important with respect to the drug's ability to (1) maintain circadian variation, albeit from a lower baseline, (2) lower BP throughout the 24 hours, (3) avoid the development of postural hypotension, (4) avoid decreases in BP sufficient to precipitate an ischemic event, (5) and to reduce BP variability toward the normal BP limits.

Antihypertensive Agents↗
PubMed1992

The neck chamber technique.

Since the first description of the neck chamber technique for stimulating carotid baroreceptors by Ernsting and Parry in 1957, a number of different neck collars have been realized, among which the simplified version devised by Eckberg and coworkers in 1975 and the neck chamber described by Ludbrook and coworkers in our Institute in 1977. At variance with Eckberg's type, the "Milan neck chamber" completely surrounds the neck and allows the application of both positive and negative pressures to the neck by means of a system of double rubber valves that prevents air leakage from the chamber. The main advantage of this technique, as compared to infusion of vasoactive drugs, is the possibility it offers to study baroreflex control not only of heart rate, but also of peripheral resistance and blood pressure through neck chamber induced changes in carotid transmural pressure. In recent years a systematic evaluation of the neck chamber technique has allowed to clarify the following issues: 1) application of positive pressure to the neck, although increasing internal jugular venous pressure and thereby reducing the pressure gradient from the arterial versus the venous side of head circulation, does not reduce cerebral blood flow; 2) changes in pressure within the neck chamber do not seem to reduce blood flow to the carotid bodies, at least to a degree which might lead to chemoreceptor stimulation; 3) there is a linear relation between changes in neck chamber pressure and changes in tissue pressure adjacent to the carotid sinus. The transmission of pressure to pericarotid tissues is complex, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1992

Variability in arterial diameter and compliance: compliance modulation reserve.

BACKGROUND: Some antihypertensive drugs are known to increase arterial compliance in hypertensives; how far compliance can be increased is unknown. DESIGN: We studied eight mildly hypertensive patients to determine how far radial artery compliance can be acutely increased, i.e. the extent of the compliance modulation reserve. METHODS: We evaluated radial artery compliance by a new technique, assessing it throughout the cardiac cycle before and after the intra-arterial infusion of a vasodilator agent (papaverine). RESULTS: Before papaverine, compliance decreased progressively through diastolic to systolic blood pressure values. This was the case also during the papaverine infusion. However, over the full systolo-diastolic pressure range, compliance was increased by about 40% with papaverine. CONCLUSIONS: In hypertensive subjects radial artery compliance can be markedly increased on a acute basis, indicating that those antihypertensive drugs that improve compliance have a considerable reserve to act upon.

Adult↗