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Previous studies have established the reliability of percutaneous portal venous pressure measurement using a Chiba needle, a procedure requiring fluoroscopic guidance. Intrahepatic pressure has been advocated by some as a simple and safe index of portal venous pressure. The aim of this study was to examine the reliability of intrahepatic pressure measurement and its relationship to portal venous pressure. Fifty patients requiring liver biopsy were included: 29 with cirrhosis (n = 20 micronodular, n = 9 macronodular) and 21 with various hepatic disorders but no cirrhosis. The procedure was performed under fluoroscopic guidance, using a Chiba needle connected to a manometer by a saline-filled catheter. Immediately prior to biopsy, each patient underwent measurement of: (i) 3 to 5 separate intrahepatic pressures, the intraparenchymal site being inferred by the lack of blood or bile return; and (ii) portal and hepatic venous pressures, the intravascular position of the needle being ascertained by the reflux of blood and the vessel identified with injection of contrast. Intrahepatic pressure measurements showed great intraindividual variability (variation coefficient up to 115%). Mean intrahepatic pressure (13.19 +/- 8.32 mm Hg) was similar to portal venous pressure (14.43 +/- 6.10 mm Hg) in the noncirrhotics but significantly lower in the cirrhotics (intrahepatic pressure = 18.34 +/- 8.82 mm Hg, portal venous pressure = 22.52 +/- 9.47 mm Hg; p less than 0.01). The difference between these two parameters exceeded 3 mm Hg in 50% of patients (mean = 9 mm Hg, range = 4 to 19 mm Hg), both in cirrhotics and noncirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)
The mechanisms involved in hypertrophy of the left ventricle were studied in Langendorff-perfused rat hearts by measuring the ventricular protein synthesis and its transmural distribution and by differentiating between the effects of changes in mechanical work load, intraventricular and coronary pressures. An increase in the aortic pressure from 7.85 kPa (80 cm of water) to 19.6 kPa (200 cm of water) in beating hearts increased phenylalanine incorporation into left ventricular protein from 1.4 to 2.0 mumol/g protein (p less than 0.02) during a two-hour perfusion. The protein synthesis was transmurally evenly distributed. A similar elevation in the perfusion pressure in potassium arrested hearts caused an increase in phenylalanine incorporation from 1.5 to 1.9 mumol/ (p less than 0.05) when the intraventricular pressure was adjusted to zero, indicating that the increase in aortic (coronary) pressure and not the work load per se was the reason for increased protein synthesis. Elevation of the end-diastolic pressure from zero to approximately 2 kPa in beating hearts at an aortic pressure of 7.85 kPa, or from 7.85 kPa to 17.3 kPa in K+-arrested hearts, at an aortic pressure of 19.6 kPa caused a significant reduction in subendocardial protein synthesis, whereas subepicardial phenylalanine incorporation was at most only slightly affected. The energetic parameters, oxygen consumption, output of vasoactive purine compounds and distribution of coronary flow indicate that the increase in protein synthesis via the elevation in aortic pressure was not due to the abolition of partial anoxia, whereas the same parameters indicate that the transmural gradient in protein synthesis observed under certain conditions was due to subendocardial ischemia when the intraventricular pressure approached the aortic pressure in arrested hearts, which are evidently of restricted use for extended periods without special measures to limit the build-up of intraventricular pressure.
Blood pressure variability under basal conditions and blood pressure reactivity to emotional stress were studied in 38 hypertensives and 13 normotensives. Systolic basal blood pressure variability correlated with systolic blood pressure reactivity. Variability increased with higher basal blood pressure. Thus in the hypertension group the blood pressure variability was greater than in the normotension group. Besides, the hypertension group showed a greater reactivity of systolic blood pressure to emotional stress, too. An influence of age on basal blood pressure, blood pressure variability, and reactivity could be evaluated; but no influence of sex on these parameters was detected. The results indicate that variability and reactivity of blood pressure can be referred to a common central nervous blood-pressure-regulating mechanism. As both parameters are increased in hypertension, a greater lability of blood pressure must be assumed. This greater lability may be attributed to a stronger neurogenic influence or to structural changes of peripheral blood vessels.
Portal vein pressure and wedged hepatic vein pressure were measured simultaneously in 21 patients with hepatitis B-related cirrhosis of the liver and were compared to pressure measured in six patients with idiopathic portal hypertension. No significant difference in the portal venous pressure gradient was found between patients with cirrhosis and those with idiopathic portal hypertension (17.3 +/- 4.3 mmHg (mean +/- S.D.) vs. 19.7 +/- 3.1 mmHg, P greater than 0.05). However, the difference between the portal and the hepatic venous pressure gradient was significantly smaller in patients with cirrhosis than in idiopathic portal hypertension patients (1.3 +/- 1.7 vs. 10.8 +/- 2.1 mmHg, P less than 0.001). An excellent correlation was found between portal vein pressure and wedged hepatic vein pressure in hepatitis B-related cirrhosis (r = 0.94, P less than 0.001). There was no linear relationship between the portal venous pressure gradient and varix size or bleeding episodes. We concluded that a close agreement existed between portal vein pressure and wedged hepatic vein pressure in hepatitis B-related liver cirrhosis. Therefore, measurement of wedged hepatic vein pressure reliably reflects portal vein pressure in these patients.
This study has analyzed the relationships of cross-cultural variation in blood pressure to cultural characteristics, salt consumption and body weight. The data used were blood pressures for adults in 84 groups, ratings of cultural characteristics (based on anthropological data and made by raters who had no knowledge of the blood pressure data) and, where available, salt consumption and body mass index (weight/height2). Blood pressures were higher and the slopes of blood pressure with age were greater in groups which had greater involvement in a money economy, more economic competition, more contact with people of different culture or beliefs, and more unfulfilled aspirations for a return to traditional beliefs and values. Blood pressures were also higher in groups for which the predominant family type was a nuclear or father-absent family, as opposed to an extended family. For Negroes, groups who were descended from slaves had higher blood pressures than other groups. The correlations between blood pressures and involvement in a money economy were substantial and significant even after controlling for level of salt consumption and, for men, also after controlling for body mass index. For men there were also significant partial correlations between blood pressure and salt consumption, controlling for type of economy. For women there were significant partial correlations between blood pressure and body mass index, controlling for type of economy. In conclusion, cross-cultural variation in blood pressure appears to be due to multiple factors. One contributory factor appears to be psychosocial stress due to cultural disruption, including the disruption of cooperative relationships and traditional cultural patterns which frequently occurs during economic modernization. In addition, both the protective effects of very low salt consumption in some groups and differences in body weight appear to contribute to cross-cultural variation in blood pressure.
Arterial pressure measured in a peripheral artery may significantly underestimate central arterial pressure after discontinuation of cardiopulmonary bypass (CPB). Arterial pressure measured with a 50 cm radial artery catheter advanced into the brachial or axillary artery was compared to ascending aortic pressure in 31 patients before and after discontinuation of CPB. The radial artery catheter extended proximally into the brachial artery in 8/31 patients, and into the axillary artery in 23/31 patients. The patient's age, pre-CPB cardiac ejection fraction, and surgical procedures were similar in both groups. The systolic arterial pressure measured in the ascending aorta was found to be significantly different from that in the axillary artery after CPB, whereas the mean and diastolic pressures were not. The average aorta-to-axillary artery systolic pressure gradient was -3.0 +/- 4.0 mmHg, with no patient having a gradient greater than 10 mmHg. The systolic and mean arterial pressures measured in the ascending aorta were found to be significantly different from that in the brachial artery after discontinuation of CPB, whereas the diastolic pressure was not. The average aorta-to-brachial artery systolic pressure gradient was 6.9 +/- 6.9 mmHg, with 3/8 patients having a gradient greater than 10 mmHg. Long radial artery catheters, placed using the Seldinger technique, provide an accurate estimate of central aortic pressure after CPB when they are advanced into the axillary artery. Sites more distal than the axillary artery may result in significant underestimation of the central aortic pressure in these patients.
STUDY OBJECTIVES: We determine the effect of pressure immobilization on mortality and intracompartmental pressure after artificial intramuscular Crotalus atrox envenomation in a porcine model. METHODS: We prospectively studied 20 pigs using a randomized, controlled design. After anesthesia, C atrox venom (20 mg/kg) was injected with a 22-gauge needle 10 mm deep into the tibialis anterior muscle of the hind leg. Pigs were randomized to receive either pressure immobilization (applied 1 minute after envenomation and maintained throughout the duration of the experiment) or no pressure immobilization. We measured time to death, intracompartmental pressure before venom injection and at 2 hours after injection, and leg circumference at a standardized location before injection and immediately postmortem. Duration of survival was compared using Kaplan-Meier survival analysis. RESULTS: The dose of venom resulted in 100% mortality. The median survival was longer in the pressure immobilization group (191 minutes, range 140 to 240 minutes) than in the control group (median 155 minutes, range 119 to 187 minutes). The difference between the groups was 36 minutes (95% confidence interval [CI] 2 to 64 minutes; P =.0122). The mean intracompartmental pressures were 67+/-13 mm Hg+/-SD with pressure immobilization and 24+/-5 mm Hg without pressure immobilization. The difference between groups was 43 mm Hg (95% CI 32 to 53 mm Hg). The mean circumferences were 14.3 cm in the pressure immobilization group and 19.1 cm in the control group. The difference between groups was -4.8 cm (95% CI -5.7 to -3.9 cm). CONCLUSION: Compared with control animals without treatment, the pressure immobilization group had longer survival, less swelling, and higher intracompartmental pressures after artificial, intramuscular C atrox envenomation in our porcine model.
This study investigated the reproducibility of repeated measurements with the Kikuhime pressure sensor under two different types of pressure garments used in the treatment and prevention of scars after burns. Also efficiency of garments was assessed in clinical circumstances by assessing pressure loss and residual pressure after 1 month. Intra- and inter-observer reproducibility and repeated measurements with 1-month time lapse were examined on 55 sites in 26 subjects by means of intra-class correlation coefficients and standard error of measurements. Results showed good to excellent ICC and low SEMs in the two conditions. There was a significant difference in pressure after 1 month between elastic tricot and weft knit garments, although evolution of pressure loss after 1 month was similar. Concerning different locations, there was a significant difference in pressure loss after 1 month between gloves and sleeves with the largest pressure loss for sleeves. Considering these results we concluded that the Kikuhime pressure sensor provides valid and reliable information and can be used in comparative clinical trials to evaluate pressure garments used in burn scar treatment. Secondly, elastic tricot garments in our study tended to have higher clinical pressures but both types of garments had similar pressure loss over time.
The accuracy and reliability of a noninvasive pressure-sensitive capsule for the endoscopic measurement of esophageal varix pressure was evaluated. Capsule pressure was correlated with direct intraluminal pressure measurements. The influence of vessel wall tension on capsule pressure was also assessed. In vitro studies demonstrated an excellent correlation (r greater than or equal to 0.94; p less than 0.001) between the pressure obtained with the capsule and intraluminal pressure over a range of vessel diameters and wall thicknesses. In vivo correlation of pressures obtained with the capsule with direct venous pressure measurements was excellent (r = 0.85). However, this correlation decreased with a decrease in vessel diameter (group 1 diameter greater than or equal to 10 mm, r = 0.95; group 2 diameter greater than or equal to 5 mm but less than 10 mm, r = 0.75; group 3 diameter greater than or equal to 3 mm but less than 5 mm, r = 0.81). This decrease in accuracy was significant (p less than 0.001) between group 1 and groups 2 and 3. In vitro and in vivo, capsule pressure variability was significantly greater (p less than 0.001) in vessels of smaller diameter. Wall tension significantly influenced capsule pressure (p less than 0.05), although this effect was only seen in large "vessels" with a diameter beyond a clinically relevant range. Therefore, despite obtaining technically acceptable capsule pressure measurements in ideal experimental conditions, the accuracy and variability of these measurements are limited by vessel size.
The inactivation of Escherichia coli by high hydrostatic pressure treatment at up to 550 MPa and 20 degrees C was studied in potassium phosphate buffer containing high concentrations of sucrose. E. coli strain MG1655 was pressure-sensitive in the absence of sucrose, but became highly pressure resistant in the presence of 10% to 50% (w/v) sucrose. The pressure resistance of E. coli strain LMM1010, a previously described derivative of MG1655 that is pressure resistant in the absence of sucrose, was further increased in the presence of sucrose, to a similar level as for strain MG1655 in the presence of sucrose. When cell suspensions of either strain were stored after pressure treatment for 24 h at 20 degrees C, a further reduction of the plate counts indicative of pressure induced sublethal injury was observed, that was positively correlated with pressure intensity and negatively with sucrose concentration. Addition of the lactoperoxidase system to the cell suspensions strongly enhanced high pressure inactivation of E. coli at high sucrose concentrations. Using a pressure intensity of only 250 MPa, both E. coli strains were sensitized for the lactoperoxidase system in up to 30% (w/v) sucrose, resulting in at least 10(6)-fold inactivation within 24 h or less after pressure treatment. For comparison, a pressure treatment at 250 MPa in the absence of the lactoperoxidase system did not cause any inactivation of either strain even in the absence of sucrose. At sucrose concentrations above 30% (w/v), no or very little inactivation occurred even in the presence of the lactoperoxidase system.
OBJECTIVE: To evaluate the effects of abdominal belts on lifting performance, muscle activation, intra-abdominal pressure and intra-muscular pressure of the erector spinae muscles. DESIGN: Simultaneous measurement of intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles was performed during the Valsalva maneuver and some isometric lift exertions. BACKGROUND: While several hypotheses have been suggested regarding the biomechanics of belts and performance has been found to increase when lifting with belts, very little is known about the modulating effects on trunk stiffness. At present, there is no reason to believe that spine tolerance to loads increases with belts. METHODS: An abdominal belt designed for weightlifting was used. Intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and myoelectric activities of trunk muscles (erector spinae, rectus abdominis and external oblique) were measured simultaneously during the Valsalva maneuver as well as three types of isometric lifting exertions (arm, leg and torso lift). A paired t-test was used to analyze for statistical differences between the two conditions (without-belt and with-belt) in intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and in the integrated EMG of the trunk muscles. RESULTS: Intra-muscular pressure of the erector spinae muscles increased significantly by wearing the abdominal belt during Valsalva maneuvers and during maximum isometric lifting exertions, while maximum isometric lifting capacity and peak intra-abdominal pressure were not affected. Integrated EMG of rectus abdominis increased significantly by wearing the abdominal belt during Valsalva maneuvers (after full inspiration) and during isometric leg lifting. CONCLUSIONS: Wearing abdominal belts raises intra-muscular pressure of the erector spinae muscles and appears to stiffen the trunk. Assuming that increased intra-muscular pressure of the erector spinae muscles stabilizes the lumbar spine, wearing abdominal belts may contribute to the stabilization during lifting exertions.
Pressure garments are the mainstay of burn scar management despite limited scientific evidence. This study demonstrates a simple method of directly measuring the cutaneous pressures generated by a pressure garment. The results show pressure garments generate an increase in subdermal pressures in the range 9-90 mmHg depending on the anatomical site. Garments over soft sites generate pressures ranging from 9 to 33 mmHg. Over bony prominences the pressures range from 47 to 90 mmHg. This method is believed to be more representative of the pressures generated than the interpositional techniques that measure garment-skin interface pressure, as it avoids garment distortion, the interference effect of the measurement device (size, conformation, area) and directly measures subdermal pressures. The method should be useful for larger research projects on pressure therapy and also for clinical management of pressure garments in the treatment of hypertrophic scar.
OBJECTIVES: The purpose of this study was to evaluate the relationship of baseline pulse pressure and mean arterial pressure to mortality in patients with left ventricular dysfunction. BACKGROUND: Increased conduit vessel stiffness increases pulse pressure and pulsatile load, potentially contributing to adverse outcomes in patients with left ventricular dysfunction. METHODS: Pulse and mean arterial pressure were analyzed for their effect on mortality, adjusting for other modifiers of risk, using Cox proportional hazards regression analysis of data collected from 6,781 patients randomized into the Studies of Left Ventricular Dysfunction trials. RESULTS: Pulse and mean arterial pressure were related positively to each other, age, ejection fraction and prevalence of diabetes and hypertension and inversely to prior myocardial infarction and beta-adrenergic blocking agent use. Higher pulse pressure was associated with increased prevalence of female gender, greater calcium channel blocking agent, digoxin and diuretic use, lower heart rate and a higher rate of reported smoking history. Higher mean arterial pressure was associated with higher heart rate, lower calcium channel blocker and digoxin use and lower New York Heart Association functional class. Over a 61-month follow-up 1,582 deaths (1,397 cardiovascular) occurred. In a multivariate analysis adjusting for the above covariates and treatment assignment, higher pulse pressure remained an independent predictor of total and cardiovascular mortality (total mortality relative risk, 1.05 per 10 mm Hg increment; 95% confidence interval, 1.01 to 1.10; p = 0.02). Mean arterial pressure was inversely related to total and cardiovascular mortality (total mortality relative risk, 0.89; 95% confidence interval, 0.85 to 0.94; p <0.0001). CONCLUSIONS: One noninvasive blood pressure measurement provides two independent prognostic factors for survival. Increased conduit vessel stiffness, as assessed by pulse pressure, may contribute to increased mortality in patients with left ventricular dysfunction, independent of mean arterial pressure.
We evaluated time-related blood pressure trends in the Tecumseh study participants, none of whom received antihypertensive treatment. At baseline the blood pressures were measured in the field clinic and by self measurement at home (twice daily for 7 days). After a mean of 3.2 +/- 0.42 years, the clinic and home pressure readings were repeated. Nine hundred forty-six subjects had clinic and home blood pressure readings at baseline. Of these 735 (380 men, 355 women; average age, 32 years) also completed the second examination. Blood pressure, morphometric data, and biochemical measures at the first examination were used as predictors of future clinic blood pressures. Five hundred ninety-six subjects were normotensive on both examinations (81%). Of 79 subjects (10.7%) with clinic hypertension (> 140 mg Hg systolic or 90 mm Hg diastolic) at baseline, 38 remained hypertensive ("sustained hypertension") and 41 became normotensive ("transient hypertension") after 3 years. Another 60 normotensives at baseline (10.4%) became hypertensive on second examination ("de novo hypertensives"; incidence; 8.1%). The home blood pressure readings on both examinations were reproducible. The three hypertensive groups had elevated home blood pressure, were overweight, had dyslipidemia, and higher insulin values. Only the home blood pressure proved predictive of subsequent blood pressure trends. A home blood pressure of 128 and 83 mm Hg or higher detected "sustained" hypertension with a 48% sensitivity and 93% specificity. Readings of 120 and 80 mm Hg or lower predicted future normotension with a 45% sensitivity and a 91% specificity. We conclude that self determination of the blood pressure at home is useful in the management of borderline hypertension. An algorithm for the management of these patients is proposed.