Non-invasive blood pressure measurement in Yucatan miniature swine using tail cuff sphygmomanometry

A relatively new non-invasive method using a photo-electric flow sensor in non-heated animals, was evaluated for its accuracy in measuring systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) in 40-90 Kg normotensive and hypertensive Yucatan miniature swine. Directly measured SBP, DBP and electronically averaged MAP were recorded from chronic arterial catheters simultaneously with indirect pressures, cuff pressure and tail blood flow under various conditions. In all of the tests tail cuff SBP estimation averaged within 5% of directly measured SBP. The correlation of the two methods was significant (r = .95, P less than 0.01). Over a 60 to 202 mmHg range of blood pressure induced pharmacologically or due to DOCA hypertension, the tail cuff SBP was within 4-10% of directly measured SBP. The tail cuff method was also used to determine DBP and MAP. DBP determined from the tail cuff record was found consistently to underestimate the direct measured DBP by approximately 17%. The two methods were correlated (r = .87 P less than 0.01). The measured tail cuff MAP generally underestimated the direct MAP by approximately 5%. The correlation of directly measured MAP and tail cuff methods was significant (r = .72, P less than 0.01). These results indicated that this system may be used to accurately assess blood pressure in miniature swine.     

The relationship of family income,family size,age and circumferences with blood pressure in the female students of the Bahauddin Zakariya University,Multan, Pakistan

In a randomly selected sample of 600 female students of the Bahauddin Zakariya University, Multan, Pakistan, belonging to different socioeconomic groups, age, family income and family size were recorded and measurements were made of arm, waist, neck and total circumferences, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP). The correlation coefficients between different independent (age, family income, family size, arm, waist, neck and total circumference) and dependent variables (SBP, DBP and MAP) showed that age had a strong association (p < 0.001) with all types of blood pressure, whereas the correlation coefficient of family income and family size was significant with SBP (p < 0.05) and non-significant with DBP and MAP. Moreover, all the circumferences had strong relationship (p 0.05 at least) with blood pressure. The regression coefficients of age were highly significant for SBP, DBP and MAP, whereas these were non-significant (p > 0.05) for family income and family size. The regression coefficients for arm and waist were significant (p < 0.05), whereas these were highly significant (p < 0.01 at least) for neck and total circumferences. The neck had a 0.46 mm Hg/cm with SBP, 0.41 mm Hg/cm for DBP and 0.44 Hg/cm for MAP, and these were highest among the circumferences.     

How many sphygmomanometric cuff inflations are necessary to obtain a hemodynamic baseline?

The purpose of this study was to determine the minimum number of consecutive blood pressure cuff inflations required to obtain seated stable resting baseline measurements of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP). Sixty male college students aged 18 to 31 years volunteered as study subjects. Thirteen observations of HR, SBP, DBP, and MAP were recorded at 90-second intervals for each subject using a Critikon-Dinamap monitor. Stable readings for SBP and MAP were obtained in 6.5 minutes or 3 to 5 cuff inflations in the population tested. Using this procedure, additional age- and gender-specific norms could be established for normal and hypertensive subjects. Knowing the approximate quantity and frequency of blood pressure cuff inflations needed to generate baseline minimum measurements of HR, SBP, DBP, and MAP will be helpful in studies of cardiovascular reactivity, as well as for clinical and psychophysiologic treatment of hypertension.     

The relationship of age, body mass index and waist circumference with blood pressure in Bengalee Hindu male jute mill workers of Belur, West Bengal, India

A cross-sectional study of 150 adult Bengalee Hindu male jute mill workers of Belur, a suburb of Kolkata, West Bengal, India, was undertaken to study the relationship of age, body mass index (BMI) and waist circumference (WC) with systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure. The mean age and the BMI of the subjects were 40.7 years (S.D. = 15.2) and 23.2 kg/m2 (S.D. = 3.2), respectively. The mean SBP, DBP and MAP were 124.7 mmHg (S.D. = 7.8), 81.5 mmHg (S.D. = 5.7) and 95.9 mmHg (S.D. = 6.1), respectively. Age had similar significant (p < 0.001) correlations with BMI and WC. Age and WC were significantly correlated (p < 0.001) with all the three blood pressure variables. In general, the correlations of BMI with SBP (r = 0.24, p < 0.01), DBP (r = 0.15, n.s.) and MAP (r = 0.19, p < 0.05) were weaker. Age controlled multiple regression analyses demonstrated that BMI did not have a significant effect of any blood pressure variable. However, WC had a significant impact (p < 0.0001) on SBP (t = 7.068), DBP (t = 5.190) and MAP (t = 6.387), even after adjusting for the effect of age. Moreover, even after age adjustment, percent variations in SBP (20.7%), DBP (12.5%) and MAP (17.2%) explained by WC were high. This significant impact (p < 0.0001) of WC on SBP (t = 9.426), DBP (t = 8.349) and MAP (t = 9.642) remained even after controlling for the combined effects of age and BMI.     

血液透析血压及其变异性与患者预后的相关性分析

目的:探讨血液透析前后和血液透析过程中血压及其变异性与患者预后的相关性。方法:选取沈阳军区总医院血液透析中心2010年1月1日至2013年12月31日收治的维持性血液透析患者,收集并对比随访期内生存及死亡患者的自然信息及临床资料,评估血液透析过程中患者血压及其变异程度与患者预后的关系。结果:共有269例患者纳入研究,经过4年随访共死亡83(30.86%)例。死亡组年龄显著大于存活组(64.92±13.24岁比49.89±12.86岁,P=0.000),而透析年限显著短于存活组(2.60±2.56年比7.25±4.14年,P=0.000)。死亡组透析前SBP(P=0.001)、DBP(P=0.000)、MAP(P=0.000)均显著高于存活组。两组间透析后SBP、DBP、MAP比较均无显著差异。死亡组△SBP(P=0.026)、△DBP(P=0.001)、△MAP(P=0.001)幅度显著大于存活组。死亡组透析前SBP变异率显著高于存活组(P=0.001);死亡组透析后SBP变异率(P=0.000)、DBP变异率(P=0.014)、MAP变异率(P=0.005)均高于存活组。死亡组每次透析前各时间点间SBP变异率(0.12±0.04 mm Hg比0.09±0.03 mm Hg,P=0.000)与MAP变异率(0.10±0.03mm Hg比0.09±0.03 mm Hg,P=0.001)显著高于非死亡组。结论:维持性血液透析患者透析前血压、透析前后血压改变幅度、透析前后血压变异率、每次透析各时间点间血压变异率等与全因死亡相关。     

高血压大鼠心肌肥大及逆转过程中相关因素的探讨

目的：探讨在心肌肥大及逆转过程中收缩压(SBP)、舒张压(DBP)、平均动脉压(MAP)、神经肽Y(NPY)等与左心室肥大的关系。方法：血压和心率用生物信号分析系统记录;NPY用放射免疫法测定,用SPSS软件求出了相关系数和回归方程。结果：SBP、DBP、MAP、心肌匀浆中NPY与心系数(LVW／BW)呈正相关,血液中NPY和心率(HR)与心系数不相关。结论：血压升高是导致左室肥大的因素之一,收缩压的影响大于舒张压;SBP、DBP、MAP、心肌匀浆中NPY与心系数(LVW/BW)有相关的趋势。     

Circadian pattern of blood pressure,heart rate,and double product in liver glycogen storage disease

The objective of this study was to determine systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP), heart rate (HR), double-product (DP: SBP x HR), and activity levels and their 24h pattern in liver glycogen storage disease (LGSD) patients. A case series of 12 (11 pediatric and one adult) diurnally active LGSD (seven type I, three type III, and two type IX) subjects were simultaneously assessed by 24h ambulatory blood pressure monitoring and wrist actigraphy. Nine subjects were judged to be hypertensive based on the criterion of an elevated 24h mean SBP and/or DBP being elevated beyond reference standards or the SBP and/or DBP load (percentage of time BP exceeds normal values) being greater than 25%. Two of the three other subjects, not viewed as hypertensive based on their 24h average SBP or DBP, exhibited daytime or nighttime SBP and/or DBP load hypertension. Each study variables displayed statistically significant (p < 0.001) group circadian rhythmicity. The SBP, DBP, and MAP displayed comparable 24h patterns of appreciable amplitude (total peak-trough variation equal to 17.7, 23.6, and 19.6%, respectively, of the 24h mean) with highest values (orthophase) occurring approximately 11 h after the commencement of daytime activity. The sleep-time trough (bathyphase) occurred approximately 4.5 h before morning awakening. The statistically significant (p < 0.006) circadian rhythms of HR (amplitude equal to 33.2% of the 24h mean) and DP (amplitude equal to 49.4% of the 24h mean) peaked earlier, approximately 7.4 h into the daytime activity span. The sleep-time trough occurred approximately 3 h before morning awakening. The 24h pattern in the cardiovascular variables was correlated with the 24h pattern of activity, with r ranging from 0.50 for DBP to 0.39 for HR.     

Adiposity,central body fat distribution and blood pressure among young Bengalee adults of Kolkata,India: sexual dimorphism

A cross-sectional study of 174 men and 153 women of Bengalee ethnicity was undertaken to compare levels of adiposity, central body fat distribution and blood pressure. The mean age of both the sexes were similar (men = 20.1 years; women = 20.0 years). Significantly more women (n = 42, 27.5%) were overweight (body mass index, BMI > or = 25.0 kg/m2) as compared with men (19, 10.9%). Men were significantly taller and heavier. They also had significantly greater mean waist (WC) and mid upper arm (MUAC) circumferences compared with women. On the other hand, women had significantly (p < 0.001) greater mean BMI, biceps (BSF), triceps (TSF) and subscapular (SSF) skinfolds. The mean values of systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure were significantly greater among men. These significant differences existed even after controlling for BMI. Regression analyses revealed that sex had significant effect on all these variables even after controlling for BMI. Correlation studies showed that WC was found to be much more strongly correlated than BMI with SBP, DBP and MAP, in both sexes. However, when the effect of WC (along with BMI) was also controlled for, there was no significant sex difference in blood pressure.     

CIRCADIAN PATTERN OF BLOOD PRESSURE,HEART RATE,AND DOUBLE PRODUCT IN LIVER GLYCOGEN STORAGE DISEASE

The objective of this study was to determine systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP), heart rate (HR), double-product (DP: SBP×HR), and activity levels and their 24h pattern in liver glycogen storage disease (LGSD) patients. A case series of 12 (11 pediatric and one adult) diurnally active LGSD (seven type I, three type III, and two type IX) subjects were simultaneously assessed by 24h ambulatory blood pressure monitoring and wrist actigraphy. Nine subjects were judged to be hypertensive based on the criterion of an elevated 24h mean SBP and/or DBP being elevated beyond reference standards or the SBP and/or DBP load (percentage of time BP exceeds normal values) being greater than 25%. Two of the three other subjects, not viewed as hypertensive based on their 24h average SBP or DBP, exhibited daytime or nighttime SBP and/or DBP load hypertension. Each study variables displayed statistically significant (p<0.001) group circadian rhythmicity. The SBP, DBP, and MAP displayed comparable 24h patterns of appreciable amplitude (total peak–trough variation equal to 17.7, 23.6, and 19.6%, respectively, of the 24h mean) with highest values (orthophase) occurring ～11 h after the commencement of daytime activity. The sleep-time trough (bathyphase) occurred ～4.5 h before morning awakening. The statistically significant (p<0.006) circadian rhythms of HR (amplitude equal to 33.2% of the 24h mean) and DP (amplitude equal to 49.4% of the 24h mean) peaked earlier, ～7.4 h into the daytime activity span. The sleep-time trough occurred ～3 h before morning awakening. The 24h pattern in the cardiovascular variables was correlated with the 24h pattern of activity, with r ranging from 0.50 for DBP to 0.39 for HR.     

Genetic epidemiological study of blood pressure in a sedentary rural agricultural population of West Bengal, India

To study the genetic epidemiology of blood pressure (BP), data on 78 families were collected from a sedentary agricultural population of eastern India. The general levels of both systolic (SBP) and diastolic (DBP) blood pressures are found to be low (mean SBP = 106.41 mm Hg; mean DBP = 63.94 mm Hg). Trends of blood pressures with age are similar to those reported earlier (e.g., in the Framingham study). Environmental variables--e.g., occupation and tobacco use--do not have any direct significant effect on blood pressure variability in this population. Path analysis of family data shows a highly significant familial aggregation and yields a genetic heritability (maximum) estimate of 0.3 for both SBP and DBP. Sib-sib and mother-child correlation estimates are, respectively, 0.3 and 0.25. Father-child correlation estimates are 0.13 for SBP and near zero for DBP. A pseudopolygenic model yields the best fit to the data on SBP, while for DBP a proper resolution of various models considered could not be obtained.     

Familial resemblance of blood pressure with residual household environmental effects in consanguineous and nonconsanguineous families from Andhra Pradesh, India.

Familial aggregation of blood pressure (BP), both systolic (SBP) and diastolic (DBP), was examined in consanguineous and nonconsanguineous families from southern India. Path analysis of BP suggests inbreeding effects, with the genetic variance for SBP being lower in the sample that included inbred families. Specifically, genetic heritability for SBP was 38% in the nonconsanguineous sample but only 23% in the combined sample. Genetic heritability for DBP (30%) did not vary by sample, nor were sample differences in cultural heritability detected for either SBP (over 35%) or DBP (about 18%). These findings are remarkably similar to those in a French-Canadian population of Quebec; both reports found a considerably larger effect of the home environment on BP than previous studies.     

Blood pressure levels of the Suruí and Zoró Indians of the Brazilian Amazon: group- and sex-specific effects resulting from body composition, health status, and age

Two related Tupí-Mondê-speaking tribes of the Aripuan? Indian Park of western Brazil are compared in terms of their recent contact with Western culture, subsistence patterns, general health, and blood pressure levels. Age, weight, height, sex, and tribal affiliation for Suruí and Zoró adults over age 18 are included in an analysis of covariance to test regression models of both diastolic and systolic blood pressure. Because of significant interaction effects between sex and other covariates, sex-specific models were developed. The relationship between body mass and blood pressure level in males conforms with Western data, but the direction and magnitude of effects for the age and body mass covariates in both sexes conflict with data from other modernizing societies. With age, weight/height ratio, and sex differences controlled for, Suruí males show a lower mean systolic blood pressure (SBP) level and diastolic blood pressure (DBP) level than Zoró males. Intertribal differences were smaller among females: Suruí females SBP and DBP differences were similar but did not reach significance. Other sex-specific differences include a greater inverse relationship between age and SBP level among the 104 male subjects than among the 98 female subjects (with similar trends in DBP) and a small but significant effect of the weight/height ratio on both SBP and DBP in males but not in females. Health status data for these groups suggest that hypothesized increases in mean blood pressure levels following the Suruí's acceptance of a Western diet and social stratification may be modified by their health status, particularly prevalent infectious disease.     

Postural-induced phase shift of respiratory sinus arrhythmia and blood pressure variations: insight from respiratory-phase domain analysis

The purpose of this study is to evaluate the multiple effects of respiration on cardiovascular variability in different postures, by analyzing respiratory sinus arrhythmia (RSA) and respiratory-related blood pressure (BP) variations for systolic BP (SBP), diastolic BP (DBP), and pulse pressure (PP) in the respiratory-phase domain. The measurements were conducted for 420 s on healthy humans in the sitting and standing positions, while the subjects were continuously monitored for heart rate and BP variability and instantaneous lung volume. The waveforms of RSA and respiratory-related BP variations were extracted as a function of the respiratory phase. In the standing position, the waveforms of the BP variations for SBP, DBP, and PP show their maxima at around the end of expiration (pi rad) and the minima at around the end of inspiration (2 pi rad), while the waveform of RSA is delayed by approximately 0.35 pi rad compared with the BP waveforms. On the other hand, in the sitting position, the phase of the DBP waveform (1.69 pi rad) greatly and significantly (P < 0.01) differs from that in the standing position (1.20 pi rad). Also, the phase of PP is delayed and that of RSA is advanced in the sitting position (P < 0.01). In particular, the phase shift of the DBP waveform is sufficiently large to alter whole hemodynamic fluctuations, affecting the amplitudes of SBP and PP variations. We conclude that the postural change associated with an altered autonomic balance affects not only the amplitude of RSA, but also the phases of RSA and BP variations in a complicated manner, and the respiratory-phase domain analysis used in this study is useful for elucidating the dynamic mechanisms of RSA.     

Circadian Rhythm of Blood Pressure and Heart Rate in Healthy Persons and Kidney Transplant Patients: Correlations with Activity

Fourteen diurnally active (07: 00–22: 39 h) normotensive healthy control subjects and 14 kidney transplant patients were studied by ambulatory blood pressure monitoring and wrist actigraphy simultaneously during one 24-h period. In the control group, circadian rhythms in systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressure, heart rate (HR), and wrist activity were documented by cosinor analysis with comparable afternoon peak times. In contrast, circadian rhythms with afternoon acrophases were detected only in HR and wrist activity in the patient group. The correlation of wrist activity with HR in controls and patients was comparable. Wrist activity and blood pressure were associated (r = 0.65 DBP and 0.54 SBP; p < 0.05) in controls, while in patients the relationship was weak or absent (r ranging from 0.02 SBP to 0.22 DBP). In 6 of 14 patients, BP and wrist activity were negatively correlated, reflecting the existence of nocturnal hypertension. In eight others, the correlation was small but positive. The 24-h pattern in BP and wrist activity in controls was comparably phased; however, this was not the case for the transplant patients, indicating the day-night pattern in blood pressure in this group is strongly dependent on pathologic phenomena rather than activity level and pattern.     

Age, gender and circadian or circasemidian blood pressure and heart rate variation of children.

Systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) of clinically healthy children (24 boys and 15 girls) 3 to 7 years of age were measured with a standard mercury sphygmomanometer at 3-hour intervals for 24 hours in April 1991. The children slept and/or rested from 2100 to 0700 and napped from 1230 to 1530; they had meals at 0730, 1200 and 1800. A statistically significant circadian and about 12-hour (circasemidian) component of variation is documented for SBP and DBP of boys and girls and for HR of boys. No gender difference was found for the circadian and circasemidian components. A positive correlation with age is found for the MESOR and circadian amplitude of SBP and DBP (p < 0.05); a negative correlation with age is found for the MESOR of HR (p < 0.001).     

Histone 3 modifications and blood pressure in the Beijing Truck Driver Air Pollution Study

Context: Histone modifications regulate gene expression; dysregulation has been linked with cardiovascular diseases. Associations between histone modification levels and blood pressure in humans are unclear.

Objective: We examine the relationship between global histone concentrations and various markers of blood pressure.

Materials and methods: Using the Beijing Truck Driver Air Pollution Study, we investigated global peripheral white blood cell histone modifications (H3K9ac, H3K9me3, H3K27me3, and H3K36me3) associations with pre- and post-work measurements of systolic (SBP) and diastolic (DBP) blood pressure, mean arterial pressure (MAP), and pulse pressure (PP) using multivariable mixed-effect models.

Results: H3K9ac was negatively associated with pre-work SBP and MAP; H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP; and H3K27me3 was negatively associated with pre-work SBP. Among office workers, H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP. Among truck drivers, H3K9ac and H3K27me were negatively associated with pre-work SBP, and H3K27me3 was positively associated with post-work PP.

Discussion and conclusion: Epigenome-wide H3K9ac, H3K9me3, and H3K27me3 were negatively associated with multiple pre-work blood pressure measures. These associations substantially changed during the day, suggesting an influence of daily activities. Blood-based histone modification biomarkers are potential candidates for studies requiring estimations of morning/pre-work blood pressure.     

The Relationship Between Serum Calcium Level, Blood Lipids, and Blood Pressure in Hypertensive and Normotensive Subjects who Come from a Normal University in East of China

Previous studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. However, the relationship between serum calcium and blood pressure was unclear. The prevalence of hypertension is high in China. Thus, the aim of this study was to evaluate the serum calcium level between hypertensive and normotensive groups and to investigate the correlation between serum calcium, blood pressure, and blood lipid parameters. A total of 1,135 adult subjects participated in this study and were divide into two study groups: a hypertensive group (n?=?316) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP) and an age- and sex-matched normotensive group (n?=?819, 120 mmHg or less SBP and 80 mmHg or less DBP). Our results indicate a significant trend for men (60 years old or older) in the direction of decreasing blood pressure with increasing serum calcium level, but no trend for women was indicated. In the normotensive group, a significant positive correlation was found between DBP and total cholesterol (P?<?0.01) and triglyceride (P?<?0.01), Likewise, triglyceride was positively correlated with SBP (P?<?0.01). Overall, these data suggest that serum calcium may have an influence in the blood pressure of older male subjects with hypertension and in blood lipid profiles of normotensive subjects.     

Endothelial Nitric Oxide Is Not Involved in Circadian Rhythm Generation of Blood Pressure: Experiments in Wild‐Type C57 and eNOS Knock‐Out Mice under Light‐Dark and Free‐Run Conditions

Endothelial nitric oxide synthase knock out mice (eNOS‐/‐) are mildly hypertensive in comparison to wild‐type (WT) mice. Hypertension in eNOS‐/‐ mice is partly the result of an increase in peripheral resistance due to the absence of the vasodilatory action of NO. No data are available for these animals regarding the 24 h blood pressure profile under the 12:12 h light‐dark cycle (LD) and constant dark (DD) conditions. Therefore, this study aimed to investigate by radiotelemetry the circadian rhythms in systolic blood pressure (SBP) and diastolic blood pressure (DBP) of six eNOS‐/‐ mice and five wild‐type mice under LD and DD. Data were collected beginning 3 wks after operation (implantation of sensor) for 2 wks under LD and for another 2 wks thereafter under DD. Our results show that eNOS‐/‐ mice were hypertensive under all experimental conditions. SBP and DBP were significantly higher by about 15% in eNOS‐/‐ mice. No differences were found in the pattern of the circadian rhythms, rhythmicity, or period lengths during LD or DD. The genetic deletion of eNOS seems to lead to higher SBP and DBP, but the circadian blood pressure pattern is still preserved with higher values during the night (active phase) and lower values during the daytime (rest phase). Thus, endothelial‐derived NO plays an important role in the regulation of vascular tone and haemodynamics, but it is not important for the circadian organization of SBP and DBP.     

Endothelial nitric oxide is not involved in circadian rhythm generation of blood pressure: experiments in wild-type C57 and eNOS knock-out mice under light-dark and free-run conditions

Endothelial nitric oxide synthase knock out mice (eNOS-/-) are mildly hypertensive in comparison to wild-type (WT) mice. Hypertension in eNOS-/- mice is partly the result of an increase in peripheral resistance due to the absence of the vasodilatory action of NO. No data are available for these animals regarding the 24 h blood pressure profile under the 12:12 h light-dark cycle (LD) and constant dark (DD) conditions. Therefore, this study aimed to investigate by radiotelemetry the circadian rhythms in systolic blood pressure (SBP) and diastolic blood pressure (DBP) of six eNOS-/- mice and five wild-type mice under LD and DD. Data were collected beginning 3 wks after operation (implantation of sensor) for 2 wks under LD and for another 2 wks thereafter under DD. Our results show that eNOS-/- mice were hypertensive under all experimental conditions. SBP and DBP were significantly higher by about 15% in eNOS-/- mice. No differences were found in the pattern of the circadian rhythms, rhythmicity, or period lengths during LD or DD. The genetic deletion of eNOS seems to lead to higher SBP and DBP, but the circadian blood pressure pattern is still preserved with higher values during the night (active phase) and lower values during the daytime (rest phase). Thus, endothelial-derived NO plays an important role in the regulation of vascular tone and haemodynamics, but it is not important for the circadian organization of SBP and DBP.     

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Exercise challenges cerebral autoregulation (CA) by a large increase in pulse pressure (PP) that may make systolic pressure exceed what is normally considered the upper range of CA. This study examined the relationship between systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) and systolic (V(s)), diastolic (V(d)). and mean (V(m)) middle cerebral artery (MCA) blood flow velocity during mild, moderate, and heavy cycling exercise. Dynamic CA and steady-state changes in MCA V in relation to changes in arterial pressure were evaluated using transfer function analysis. PP increased by 37% and 57% during moderate and heavy exercise, respectively (P < 0.05), and the pulsatility of MCA V increased markedly. Thus exercise increased MCA V(m) and V(s) (P < 0.05) but tended to decrease MCA V(d) (P = 0.06). However, the normalized low-frequency transfer function gain between MAP and MCA V(m) and between SBP and MCA V(s) remained unchanged from rest to exercise, whereas that between DBP and MCA V(d) increased from rest to heavy exercise (P < 0.05). These findings suggest that during exercise, CA is challenged by a rapid decrease rather than by a rapid increase in blood pressure. However, dynamic CA remains able to modulate blood flow around the exercise-induced increase in MCA V(m), even during high-intensity exercise.