Indirect Blood Pressure Measurement Research Articles

The relative accuracy of sequential same-arm and simultaneous opposite-arm measurements for the intra-arterial validation of blood pressure monitors

To compare the results of simultaneous opposite-arm and sequential same-arm intra-arterial validation of automated blood pressure monitors. Intra-arterial blood pressure measurements were compared with blood pressure measurements obtained using conventional sphygmomanometry and two automated blood pressure monitors (the Dinamap XL and the SpaceLabs Scout) using a methodology based on the protocol published by the Association for the Advancement of Medical Instrumentation (AAMI) for the intra-arterial validation of automated monitors. Thirteen women with radial arterial lines were recruited from the obstetric intensive care unit at Groote Schuur Hospital, Cape Town. For each woman, intra-arterial blood pressure measurements were compared with those obtained by mercury sphygmomanometry and by using the two automated blood pressure monitors with both a sequential same-arm protocol and a simultaneous opposite-arm protocol. The mean and SD of the differences was calculated for each protocol and the results were compared using Student s t test. The differences between the 'means of the differences' for these two protocols never differed by more than 2 mmHg. For individuals the differences between data obtained using the two methodologies were up to 32 mmHg for mercury sphygmomanometry and 18 mmHg for the automated monitors. The differences between the SD of the differences were all less than 3 mmHg except for that of systolic blood pressure obtained by mercury sphygmomanometry, which was 7 mmHg The results of this study show that a sequential same-arm and a simultaneous opposite-arm comparison of intra-arterial and indirect blood pressure measurements yield similar results.

Inter- and intraindividual variation in Doppler ultrasonic indirect blood pressure measurements in healthy cats.

This study was undertaken to evaluate reference ranges for systolic blood pressure (SBP) in cats under conditions mimicking a clinical setting. SBP was measured in 50 healthy adult cats of various ages (range, 1.5-16 years) and body weights (range, 2.2-6.1 kg) by Doppler ultrasonic sphygmomanometry. A cuff width of 2.5 cm was used, placed on the left antebrachium, and this represented a mean cuff width of 35% limb circumference (range, 31-42%). The mean (+/-SD) SBP in the 50 cats was 162 +/- 19 mm Hg (range 124-210), with only 1 cat having a SBP > or = 200 mm Hg. No significant difference (P > .05) in SBP was found between male and female cats, and no significant correlation was found between SBP and age (r(s) = 0.075) or body weight (r(s) = 0.007). Further studies in some of these cats indicated that allowing a period of 10 minutes for acclimatization to the environment where SBP was recorded resulted in a significant decrease in SBP from 176 +/- 17 to 157 +/- 21 mm Hg (n = 7) and that use of a 3.3-cm-width cuff resulted in a significant decrease in measured SBP from 168 +/- 13 to 164 +/- 13 mm Hg (n = 10). Reproducibility of SBP measurements was evaluated in 7 cats by assessing SBP 7 times at intervals of > or = 24 hours over a 10-day period. These 7 cats had a low intraindividual coefficient of variation of SBP measurements (CV < or = 7.9%) although 2 of the 7 cats had SBP values > 200 mm Hg on at least 1 occasion.

A new method for automated blood pressure measurement

We propose a new technique for automated indirect blood pressure measurement based on the auscultatory method. Systolic, diastolic and blood mean pressure are identified by looking at trend changes in the spectral energy dispersion of Korotkoff sounds. The detection is solely based on patient measurements, not on population studies. By comparing the automatic detection with common auditory detection, in 286 measurements taken in 15 subjects there was agreement ( sound - 400 Pa error) in 278 cases for the systole and 276 cases for the diastole. Keywords: blood pressure, Korotkoff sounds, sound spectrum, ausculatory method, oscillometric method

Which Korotkoff sound should be used for the diastolic blood pressure in pregnancy?

There is a gathering momentum favouring the adoption of the 5th Korotkoff sound to identify diastolic blood pressure in pregnancy. Our objective was to measure interobserver reliability for indirect blood pressure measurement in pregnancy for systolic and diastolic measurements and to calculate the difference in diastolic pressure measured by the 4th and 5th Korotkoff sounds. To minimize bias we used trained but previously inexperienced observers with proven, normal auditory acuity. The observers were paired in 4 teams and performed a series of 334 blinded, simultaneous observations of systolic and diastolic blood pressure measurements taken from pregnant women between 12-41 weeks' gestation. Reliability was measured by intraclass correlation coefficient for paired measures and kappa for the detection or nondetection of 4th (K4) and 5th (K5) Korotkoff sounds. K4 was undetected in 36% of observations and K5 was undetected in 2% of observations. Reliability for detection or nondetection of Korotkoff sounds was fair for K4 (kappa 0.36) and moderate for K5 (kappa 0.58). Reliability was good between observers for systolic, K4 and K5 diastolic measurements (intraclass correlation > or = 0.80). The mean difference between the diastolic pressure measured by K4 and K5 was 15 mmHg for all measurements and 8 mmHg for the top quartile of measurements (p <0.001). We found K5 to be more often and more reliably detected than K4. If units adopt K5 in preference to K4, consideration will need to be given to lowering treatment thresholds for women with borderline or mild hypertension.

The effect of divergent selection for total plasma phosphorus in Japanese quail on fearfulness and selected blood and heart parameters

A selection experiment utilizing Japanese quail was initiated to study the genetic relationship of growth and reproduction traits. In this study, lines were selected for increased (HP line) and decreased (LP line) total plasma phosphorus at the beginning of lay. The HP and LP lines were derived from a randombred control population (R1 line) that was maintained with the selected lines to remove environmental variation over generations. During the course of selection, it was observed that blood from HP line females was more viscous than that of the LP and R1 females. In later generations of selection, mortality of females during a 120-d egg production period was higher in the HP line than in the LP and R1 lines. The purpose of this experiment was to identify possible factors contributing to the increased mortality in the HP line. Fearfulness, as measured by tonic immobility, was greater in the HP and LP lines than in the R1 line. Indirect blood pressure measurements were made near the beginning and near the end of the 120-d egg production period. No significant line differences were observed in either measurement. Weight of the heart at the end of the laying period was higher in the HP and LP lines than in the R1 line. Histological study of the hearts of the HP and R1 lines indicated significant increases in the HP line in collagen content of the coronary arteries and in myocardial fibrosis. The data suggest that the increased mortality of females of the HP line relative to the R1 line during the laying period may be related to increased fearfulness and changes in the coronary structure leading to heart abnormalities.

Evaluation of noninvasive monitoring techniques in domestic ferrets (Mustela putorius furo)

Abstract Objective To evaluate instrument placement and accuracy of indirect physiologic monitoring techniques in anesthetized domestic ferrets. Animals 10 healthy adult female ferrets (Mustela putorius furo). Procedure Direct arterial blood pressure measurement and arterial blood sample collection were performed in ferrets. A pulse oximeter probe was clipped to a forefoot or hind foot; an airway adaptor for capnography was attached to the endotracheal tube; and a sphygmomanometer cuff and Doppler flow probe were positioned on the tail. Isoflurane and nitrous oxide concentrations were varied to induce episodes of hypotension or hypoxia, respectively. Aforementioned noninvasive techniques were compared with direct methods of arterial blood gas analysis, hemoximetry, and arterial blood pressure measurement. Simultaneously obtained direct and indirect measurements were statistically evaluated for mean and SD of the differences, and SEM, and subjectively, for ease of use and relevance to the clinical situation. Results Values obtained from pulse oximetry were closely related to oxygen saturation measured by blood gas analysis (O2sat). The mean (± SD) difference for all results was −0.49 (± −4.09)%. The most precise measurements were obtained when O2sat was between 90 and 100%. Capnography measurements varied between ranges. The most accurate measurements were obtained when Paco2 was &lt; 25 mm of Hg, when the mean difference was 1.6 (± −3.01) mm of Hg. Indirect blood pressure measurement consistently underestimated the direct blood pressure value. Conclusions and Clinical Relevance Pulse oximetry is a convenient and accurate method for monitoring oxygen saturation in domestic ferrets. Capnography is useful for monitoring respiratory rate and pattern, but may present difficulties in interpretation of actual Paco2. Indirect blood pressure monitoring is not accurate by use of current methods in ferrets. (Am J Vet Res 1997;58:1065–1069)

Longitudinal studies of reproducibility and variability of indirect (oscillometric) blood pressure measurements in dogs: evidence for tracking

To be clinically reliable, blood pressure readings taken in quiet surroundings with good technique from healthy, unstressed subjects accustomed to the procedure, should be reasonably constant between occasions. Apart from changes attributable to age or stress, sustained rises suggest hypertension. Yet it is increasingly realised that arterial pressure shows great short-term lability. Despite this, ‘tracking’ occurs in groups of humans, i.e. when ranked by blood pressure they tend to maintain their rank order. This paper examines month-on-month variability of arterial pressure, measured by non-invasive oscillometry (Dinamap) in both pet dogs and kennel populations. ‘Tracking’ occurred and there was also evidence of ‘white coat’ effects. Heart rate was more variable than arterial pressure and should not be used to reject pressure readings unless changes are extreme. There was further evidence that canine blood pressure rises with age.

Blood pressure measurement in severe pre-eclampsia

Hypertensive disease in pregnancy remains a leading cause of maternal mortality. Death is often associated with cerebral haemorrhage with severe hypertension being the most important aetiological factor. Accurate measurement of blood pressure (BP) is essential to prevent maternal morbidity and mortality, and most units rely on indirect BP measurements. Some automated BP monitors under-record in pregnancy and particularly in pre-eclampsia when compared with mercury sphygmomanometry. There are no published data comparing intra-arterial measurements in severe pre-eclampsia with mercury sphygmomanometry and automated devices. The objective of this study was to determine the best non-invasive method for measuring BP in women with severe hypertension. We recruited nine women who required invasive monitoring for complications of severe preeclampsia/eclampsia (eg, pulmonary oedema) and four controls with other medical conditions requiring invasive monitoring. All women were studied within 12 hours of delivery. Women gave verbal consent and the study was approved by the University of Cape Town research ethics committee. Comparison was made between intra-arterial BP and three methods of non-invasive BP measurement: conventional sphygmomanometry and two automated BP devices, the Dinamap XL 9301 (Johnson and Johnson Medical, Tampa, USA) and the SpaceLabs Scout (SpaceLabs, Redmond, USA). The signal from the radial arterial line was recorded digitally on to an IBM PC for subsequent analysis. A static calibration was performed at 0 and 100 mm Hg and optimum dynamic calibration verified with a fast-flush test. All patients were semi-recumbant and the radial catheter, transducer, BP cuff, and sphygmomanometer were at heart level. All sphygmomanometry readings were obtained by a single trained observer who was blinded to intra-arterial BP. Diastolic BP was recorded at the disappearance of sounds. Intra-arterial BP was recorded for 15 s followed by an indirect BP on the same arm. This cycle repeated ten times for each automated BP device and for mercury sphygmomanometry as recommended by the Association for the Advancement of Medical Instrumentation. The ten comparisons on each individual were reduced to a summary measure. For each indirect BP measuring device the mean and standard deviation of the differences from intra-arterial measurements were calculated. The 95% confidence intervals of the mean of the differences were calculated and if they were significantly different from zero the non-invasive measurements were considered significantly different from the intra-arterial measurements. In pre-eclamptic women both automated monitors significantly underestimated systolic and mean BP by 11–18 mm Hg (see table). Diastolic BP was also underestimated by the Dinamap (11 mm Hg). Individual measurements were underestimated by up to 40 mm Hg. Conventional sphygmomanometry underestimated systolic by 7 mm Hg, overestimated diastolic by 6 mm Hg, and therefore a calculated mean arterial pressure (MAP) was only 2 mm Hg less than intra-arterial pressure. At present the use of automated monitors for the management of women with pre-eclampsia must be regarded with caution. We do not know if the difficulty is specific to the two monitors that we have studied, or is more general since no other monitor has been evaluated in this way. Despite the disadvantages of mercury sphygmomanometry, it is the technique that should be used to confirm severe hypertension. If an automated BP monitor is to be used in a woman with pre-eclampsia, its accuracy must be verified by comparison with conventional sphygmomanometry in each individual.

Treatment of systemic hypertension in cats with amlodipine besylate.

Amlodipine besylate, a calcium channel blocker, was used to treat (mean +/- standard deviation [SD], 127 +/- 68 days) 12 cats with systemic hypertension. Amlodipine was administered orally at a dosage of 0.625 mg per cat (range, 0.08 to 0.23 mg/kg body weight; mean dose +/- SD, 0.17 +/- 0.04 mg/kg body weight) once daily as a single agent. Average indirect systolic blood pressure measurements in the 12 cases decreased significantly from 198 to 155 mmHg during amlodipine treatment. Significant changes in body weight and serum creatinine and potassium concentrations were not detected. Amlodipine appears to be a safe and effective oral treatment for systemic hypertension in cats when used chronically once daily as a single agent.

Evaluation of the IITC tail cuff blood pressure recorder in the rat against intraarterial pressure according to criteria for human devices

National standards govern the manufacture and marketing of medical devices in the United States, including those for indirect blood pressure measurement in man. There are no comparable standards for devices for recording in laboratory animals. Noninvasive tail cuff blood pressure (BP) recording in the rat is widely accepted, but beset by methodologic difficulties. Intraarterial recording is regarded as the “gold standard” but is invasive and also susceptible to methodologic error. We compared the IITC Mark 12 photoelectric/oscillometric tail cuff system (IITC Life Sciences, Woodland Hills, CA) versus simultaneous femoral intraarterial recordings in spontaneously hypertensive rats, during anesthesia and 1 to 2 days after recovery (150 recordings under each condition), according to the guidelines for human data collection and analysis suggested by the American National Standard for automated sphygmomanometers. Within- and between-observer disagreements in estimates made by two observers from 40 anesthetized recordings were less for intraarterial measurements than for the tail cuff method. Within-observer differences (mean ± SD of differences [SDD]) for systolic, diastolic, and mean pressure were 0 ± 1, 0 ± 1, and 0 ± 1 mm Hg for intraarterial versus −1 ± 3, 0 ± 8, and 0 ± 5 mm Hg for tail cuff. Between-observer differences were 0 ± 2, 0 ± 1, and 6 ± 2 mm Hg versus 5 ± 4, 13 ± 7, and 0 ± 5 mm Hg, respectively. Differences between tail cuff and intraarterial methods were 16 ± 13, −5 ± 11, and 2 ± 8 mm Hg in anesthetized animals and 8 ± 14, −5 ± 9, and 0 ± 9 mm Hg in conscious animals (39% to 82% of differences exceeded 5 mm Hg). The upper limits of clinically acceptable disagreement in the American National Standard are: mean of 5 mm Hg, SDD of 8 mm Hg. The disagreement between tail cuff and intraarterial recordings cannot be ascribed to either method with certainty. These findings do not support the manufacturer's guarantee of tail-cuff readings within “5 mm Hg of intraarterial.” Inaccuracy and unreliability of devices intended for laboratory animal use have considerable scientific, fiscal, and ethical implications. Marketing of these devices should also be governed by rigorous standards.

Assessment of the accuracy of indirect blood pressure measurements.

This study assessed the accuracy of indirect blood pressure (BP) measurements by simultaneously performing three kinds of indirect BP measurement on the left arm (auscultatory, microphone and oscillometric methods) and a direct BP measurement on the left arm. The subjects were 34 hospitalized patients, ranging in age from 18 to 73 years (average 47.5 years). Highly significant correlations in systolic or diastolic BP between a given pair of the three indirect methods. The indirect methods underestimated systolic BP and overestimated diastolic BP compared with the direct method, with differences of -12.2 +/- 10.5/+4.6 +/- 7.6 (systolic/diastolic BP) with the oscillometric method, -8.1 +/- 9.7/+1.2 +/- 8.9 with the microphone method and -10.6 +/- 8.1/+3.7 +/- 6.5 mmHg with the auscultatory method. The difference in systolic BP between the auscultatory and direct methods was greater and the difference in diastolic BP was smaller in subjects older than 50 years than in those aged 50 years or less (p < 0.001 for systolic BP, p < 0.05 for diastolic BP). The auscultatory method revealed greater systolic BP in subjects with increased carotid arterial wall stiffness assessed by echoarteriography. Thus, it is concluded that there are inherent differences in BP between the indirect and direct methods which can be attributed to the changes in arterial wall physical properties partly due to aging.

Models of experimental hypertension in mice.

Experimental models of hypertension in various animals are useful in the research of vasoactive mechanisms. Recombinant DNA technology has produced genetically engineered animals, mostly mice, useful in hypertension research. However, the development of hypertensive models in mice is fraught with technical difficulties. We describe here the successful development in mice of two common types of experimental hypertension: the renovascular two-kidney, one clip and mineralocorticoid deoxycorticosterone-salt models. By adapting technology previously used in rats, we succeeded in developing hypertension (defined as systolic pressures higher than 140 mm Hg) in more than 50% of mice so treated. We also adapted the methodology for indirect tail-cuff blood pressure measurements as well as for direct intra-arterial monitoring of blood pressure in conscious, freely moving mice. Application of these techniques in transgenic or gene knockout mice with altered vasoactive hormones or receptors should allow elucidation of the role of the target gene products in various types of hypertension.

A century of indirect blood pressure measurement. Back to basics

A century of indirect blood pressure measurement. Back to basics

Calf Blood Pressure: Clinical Implications and Correlations With Arm Blood Pressure in Infants and Young Children

Indirect measurement of lower extremity blood pressure is often used in the clinical setting, although normative data after the newborn period are not readily available. Indirect blood pressure (BP) measurement was obtained in the right arms and right calves of 148 healthy infants and young children 2 weeks to 3 years of age. All measurements were made using an oscillometric device. The infants and children are quiet or asleep and in the supine position. A BP cuff of proper size was chosen. Three measurements were made in both extremities; the average of the second and third measurements was used for all analyses. Age correlated better with calf systolic blood pressure (SBPc) than with arm SBP (SBPa) (r = .52 vs .17). Calf diastolic blood pressure (DBPc) and calf mean blood pressure (MBPc) correlated moderately poorly with age (r = .37 and .39, respectively). There was no order effect. SBPc correlated best with height (r = .53), then age (r = .52), and, finally, weight (r = .51). The correlation between BPc and BPa was moderately low. The correlation of SBPc with SBPa was r = .46; that of DBPc with DBPa was r = .37; and that of MBPc with MBPa was r = .41. From birth to 6 months, SBPc was slightly lower than SBPa (1 to 3 mm Hg). SBPc increased linearly relative to SBPa and began to exceed SBPa at 6 months of age. The pattern of DBP and MBP was similar. Wide variability of blood pressure parameters was noted between the infants and children at all ages. Reference data are presented for BPc and the difference between BPc and BPa in healthy infants and children from 2 weeks to 3 years of age. BPc is not equivalent to BPa and should not be arbitrarily substituted. Because of the wide variability among healthy infants and children, SBPc measurements should be interpreted with caution when evaluating for coarctation of the aorta.

A mathematical study of some biomechanical factors affecting the oscillometric blood pressure measurement.

A mathematical lumped parameter model of the oscillometric technique for indirect blood pressure measurement is presented. The model includes cuff compliance, pressure transmission from the cuff to the brachial artery through the soft tissue of the arm, and the biomechanics of the brachial artery both at positive and negative transmural pressure values. The main aspects of oscillometry are simulated i.e., the increase in cuff pressure pulsatility during cuff deflation maneuvers, the existence of a point of maximum pulsations (about 1.5 mmHg) at a cuff pressure close to mean arterial pressure, and the characteristic ratios for cuff pressure pulsatility at systole and diastole (0.52 and 0.70, respectively, with this model, using basal parameters and an individual set of data for the arterial pressure waveform). Subsequently, the model is used to examine how alterations in some biomechanical factors may prejudice the accuracy of pressure measurement. Numerical simulations indicate that alterations in wall viscoelastic properties and in arterial pressure pulse amplitude may significantly affect the accuracy of pressure estimates, leading to errors as great as 15-20% in the computation of diastolic and systolic arterial pressure. By contrast, changes in arterial pressure mean value and cuff compliance do not seem to have significant influence on the measurement. Evaluation of mean arterial pressure through a characteristic ratio is not robust and may lead to misleading results. Mean arterial pressure may be better evaluated as the lowest pressure at which cuff pulse amplitude reaches a plateau. The obtained results may help to explain the nature of errors which usually limit the reliability of arterial pressure measurement (for instance in the elderly).

Indirect blood pressure measurement in pregnancy

Indirect blood pressure measurement in pregnancy

Proper measurement of blood pressure and heart rate in SHRSP and WKY by an indirect volume-oscillometric method.

1. The effect of environmental temperature on the indirect measurement of rat blood pressure and heart rate was investigated with special reference to the tail arterial blood flow in both strains of SHRSP and WKY. 2. Very good correlations (r > 0.82, P < 0.05; t-test, 10 d.f.) were observed between the two values of systolic blood pressure or heart rate measured by a direct and an indirect method at environmental temperatures between 26 and 38 degrees C in SHRSP, and 34 and 38 degrees C in WKY, respectively. 3. When the temperature was elevated by 10 degrees C from 25 degrees C to 35 degrees C, the regional blood flow in the tail artery increased by 52-69%, sufficient to detect a blood flow increase by the indirect method. 4. These data showed that the best way to measure the accurate blood pressure and heart rate in both strains of SHRSP and WKY by the indirect volume-oscillometric method was to hold the rats at 34-36 degrees C for 5 min.

Evaluation of a New Control Valve for Indirect Blood Pressure Measurement

Although a relatively simple procedure, blood pressure (BP) measurement is fraught with pitfalls. One source of error is the BP cuff control valve. The Johnston valve regulates the rate of cuff deflation. This study compared the means and variances of the Johnston BP valve and the standard valve in 60 healthy volunteers and in 72 surgical patients. In these patients, all measurements were compared to intra-arterial pressure. In healthy volunteers, no statistically significant differences were found between the means or variances of the two devices. In surgical subjects, however, means for systolic blood pressure and variances for systolic and diastolic measurements differed significantly between the two devices. When differences from intra-arterial pressure were compared for both devices, variances of the systolic differences were significant. Given the wide variability of the standard cuff seen in this study, a patient could be defined as normotensive one moment and hypotensive the next. The Johnston valve has the advantage of significantly reducing the variability of systolic and diastolic blood pressure measurement.

Effects of vasopressin V1 and V2 receptor antagonists on the development of salt-induced hypertension in Dahl rats.

To determine whether the vasopressor and antidiuretic actions of arginine vasopressin (AVP) may participate in the development of salt-induced hypertension, we examined the long-term effects of AVP V1 and V2 receptor antagonists on blood pressure (BP) in Dahl-Iwai salt-sensitive (DS) and salt-resistant (DR) rats. From age 7 weeks, DS and DR rats were fed a diet containing 8% NaCl, alone (control group); 8% NaCl and 1% OPC-21268 (V1 antagonist-treated group); or 8% NaCl and 0.05% OPC-31260 (V2 antagonist-treated group). The pressor response to AVP was significantly inhibited in DS rats treated with OPC-21268. Urinary volume and water intake were significantly increased by administration of OPC-31260; this increase was greater in DR rats than in DS rats. Indirect BP measurements obtained using tailcuff plethysmography showed that DS but not DR rats developed hypertension when fed high-salt diets. However, chronic treatment with either OPC-21268 or OPC-31260 did not alter the course of hypertension in DS rats, despite the effective blocking actions of these antagonists. This finding also was confirmed by direct BP measurements. Our results indicate that even if AVP plays a role in salt-induced hypertension peripheral blockade of either subtype of AVP receptors does not prevent the development of hypertension in DS rats.

Effects of streptozotocin-induced diabetes and insulin treatment on blood pressure in the male rat.

Hyperinsulinemia may link diabetes to hypertension. We evaluated the effects of insulin on blood glucose and blood pressure in control and streptozotocin (STZ)-induced (60 mg/kg, i.v.) diabetes. Insulin was given daily for 10-14 weeks to both diabetic (0, 1, 2, and 3 U) and control (0, 2, and 3 U) male rats (n = 7-8/group). Indirect and direct blood pressures were measured as were blood glucose and several metabolic parameters. All treated rats became hyperinsulinemic. Untreated and 1 U insulin-treated diabetic rats were hyperglycemic. Higher doses of insulin significantly reduced blood glucoses in diabetic animals. Indirect blood pressure measurements were unchanged between groups. However, when measured directly, the untreated diabetic rats had significantly lower pressures that did untreated controls. Insulin treatment at dosages above 1 U normalized blood pressure in diabetic animals. These same doses of insulin also restored to normal all the metabolic parameters associated with diabetes. Insulin treatment did not affect any of the parameters evaluated in nondiabetic rats. Collectively, the results show that STZ-induced diabetes results in a decrease in blood pressure and that insulin treatment can restore blood pressure in diabetic rats. Although the results suggest that insulin may be involved in restoring blood pressure in animals with a carbohydrate imbalance, the precise mechanism for elevating blood pressure is not known with certainty.