SEARCH · PubMed Health

Results for “PRESSURE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources

PubMed1985

Non-invasive oscillometric measurement of systolic, mean and diastolic blood pressure in infants with congenital heart defects after operation. A comparison with direct blood pressure measurements.

The accuracy of indirect oscillometric blood pressure measurements has been evaluated in 32 infants up to 11 months of age undergoing heart surgery. In a number of 1029 simultaneous measurements the indirect blood pressure was compared with the direct value obtained from a radial artery catheter. Cuffs of different sizes were applied. The main results were as follows: Regarding the ratio of cuff width to arm circumference, the best correlation between oscillometric and direct blood pressure measurements was obtained with a ratio of 0.38-0.41. The value of indirect blood pressure measurements depends on the absolute height of the blood pressure. In low blood pressure there is a tendency to underestimate and in high blood pressure there is a tendency to overestimate by the oscillometric blood pressure measurement. By applying an appropriate cuff size and by using our diagrams it should be possible to derive a direct value for the blood pressure on the basis of indirect oscillometric blood pressure measurements.

Blood Pressure↗

PubMed1992

Differences in circadian blood pressure between upper and lower extremity in aortic coarctation patients with and without postoperative pressure gradients.

The purpose of this study was to investigate possible circulatory differences between pre- and poststenotic vascular beds in postoperative coarctation patients with and without a residual pressure gradient during a physiologic decrease in circulatory activity. Simultaneous diurnal variations in blood pressure in the brachial and femoral arteries were recorded in 5 long-term postoperative coarctation patients with and in 5 without a pressure gradient. The patients were studied 6.5 to 8.5 years postoperatively with intraarterial blood pressure telemetry. Both groups of patients had a normal pressure decrease during the hours of sleep. A significant (p less than 0.05) increase, however, in brachial to femoral pressure gradients developed during the hours of sleep in patients with a positive gradient in contrast to patients without a gradient who had identical pressure profiles in both vascular beds. A significant positive correlation was found between changes in mean pressure gradient and upper extremity systolic pressure (r = 0.79, p less than 0.01). There was no difference between the 2 groups regarding pre- and postoperative pressures, preoperative gradients or age at surgery. Results suggest that normalization of prestenotic circadian vascular reactivity depends on complete relief of the gradient, and that upper extremity vascular abnormality may not be fully irreversible, even in older patients with coarctation.

Adolescent↗

PubMed1987

Effect of hepatic nerves, norepinephrine, angiotensin, and elevated central venous pressure on postsinusoidal resistance sites and intrahepatic pressures in cats.

Portal venous pressure was controlled by resistance localized to specific sites in hepatic lobar veins in cats. All of the pressure drop from the portal vein to the vena cava occurred across postsinusoidal vessels; portal pressure, lobar venous pressure, and, therefore, sinusoidal pressure were not significantly different. Norepinephrine and angiotensin infusions (intraportal) caused elevation in portal pressure due to constriction of hepatic venous resistance sites as well as some constriction of presinusoidal (portal or sinusoidal) resistance sites. At low doses of norepinephrine presinusoidal constriction dominated whereas at higher doses the postsinusoidal constriction increased proportionately more. Hepatic nerve stimulation produced a similar response measured at an early time (1 min), but by 3 min the presinusoidal constriction showed complete escape so that elevated portal pressure was entirely due to hepatic venous constriction. The same site that provided basal vascular resistance also provided the increased hepatic venous resistance with nerve stimulation and infusion of angiotensin and norepinephrine. Rapid elevation of central venous pressure (CVP) caused elevated sinusoidal pressure. At high CVP (16 mm Hg), 75% of a rise in CVP was transmitted whereas at normal CVP (less than 4.5 mm Hg) less than 20% transmission occurred. The presence of a high resistance in the hepatic veins protected intrahepatic pressure from the effects of normal fluctuation of CVP.

Angiotensin II↗

PubMed1984

Pressure therapy in the treatment of post-burn hypertrophic scar--a critical look into its usefulness and fallacies by pressure monitoring.

Pressure therapy is generally accepted as the best noninvasive means of preventing and controlling hypertrophic scarring after burn injury. Most studies in the past have failed to correlate clinical response with magnitude of the garment-scar interface pressure. This study looked critically at our usual techniques of pressure therapy using pressure 'sensors' manufactured locally and based on electro-pneumatic principles. Many pitfalls, such as large variations of pressure at different geometric sites on the body, elastic deterioration in garments, problems of garment manufacture, and the unfavourable properties of the Lycra garments, were observed. Recommendations on pressure treatment were made based on our experiences, to improve the present technique of pressure therapy. These included the standardization of measurement techniques and garment tailoring, the regular checking of pressure at the garment-scar interface using pressure transducers, the appropriate garment adjustments, a strict regimen for garment wearing, and the intelligent use of pressure-padding and reinforcement. Areas of further research are also discussed.

Burns↗

PubMed2000

Assessment of alternating-pressure air mattresses using a time-based pressure threshold technique and continuous measurements of transcutaneous gases.

Alternating-pressure air mattresses (APAMs) are used increasingly for the prevention and treatment of pressure sores. Laboratory evaluation techniques have centred largely on interface pressure (IP) measurement, typically analysing discrete maximum and minimum levels, or average pressure. However, since pressure relief varies with time, a time-based analysis technique has been developed for performance assessment. IP was recorded continuously, and the duration of pressures below three thresholds (30, 20 and 10 mmHg) was calculated automatically using a computerized rig. Fifteen healthy volunteers were used to evaluate the pressure-relieving characteristics of four APAMs, including one overlay. Results indicated significant differences (P < 0.001) between products when durations below the 20 and 10 mmHg thresholds were analysed, showing that some devices were only capable of momentarily relieving pressure. Maximum contact pressures on the sacrum were significantly lower (P < 0.0001) on devices whose inflation pressure was adjusted according to subject's body mass. This technique could assist in the selection of alternating or dynamic surfaces of any description with further clinical validation.

Adult↗

PubMed1996

Measurement of pulmonary artery diastolic pressure from a right ventricular pressure transducer in patients with heart failure.

Recent studies have demonstrated that pulmonary artery diastolic (PAD) pressure can be measured from a transducer positioned in the right ventricle (RV) based on the finding that PAD and RV pressures are equal at the time of pulmonary valve opening, which is associated with the time of maximum positive rate of pressure development (dP/dtmax) in the ventricle. The objective of this study was to assess the correlation between estimated PAD (ePAD) pressure, obtained through a RV transducer, and actual PAD (aPAD) pressure in patients with heart failure who have abnormal hemodynamics, reduced systolic function, and variable degrees of mitral regurgitation (MR) and tricuspid regurgitation (TR). Simultaneous measurements of pulmonary artery and RV pressures were obtained with a high-fidelity Millar catheter (Millar Instruments, Houston, TX) in 10 patients with New York Heart Association class III-IV heart failure who were being evaluated for cardiac transplantation. The overall correlation between ePAD and aPAD pressures was .92 (R2 = .878). This was not significantly different during the Valsalva maneuver (r = .96, R2 = .943), submaximal bicycle exercise (r = .87, R2 = .756), or infusions of dobutamine and nitroglycerin (r = .82, R2 = .730). The overall average difference between the average ePAD (24.6 +/- 7.0 mmHg) and aPAD (23.6 +/- 7.0 mmHg) pressures was 1.0 +/- 3.4 mmHg. The average difference between the two pressures in patients with mild to severe MR or TR was not different compared to those patients with no or trace MR or TR. The estimation of PAD pressure from an RV transducer is valid in patients with heart failure who have abnormal hemodynamics, reduced systolic function, and variable degrees of MR and TR. This correlation was observed at rest and during several provocative maneuvers. These data will be important for the development of a chronic, implantable hemodynamic monitor for patients with heart failure.

Adult↗

PubMed2002

Pressure relief bedding to prevent pressure ulcer development in critical care.

One major risk for the critically ill patient is the development of pressure ulcers during the intensive care unit (ICU) stay. These patients have many of the risk factors for the development of pressure ulcers including reduced mobility/activity, medications, neurologic deficits, increasing age, incontinence, decreased mental status, poor nutrition, pressure, shear forces, and friction. Pressure ulcers are known to be costly for the health care system and delay recovery in many patients. Different strategies have been advocated for the prevention of pressure ulcers, and the Agency for Healthcare Research and Quality (AHRQ) has identified the use of pressure relief bedding as a means to prevent the development of pressure ulcers during hospitalization. The use of pressure relief bedding has received the most research attention to date. The focus of this article is to describe the state of the current research in this area and how this applies to critical care. Development of protocols and guidelines for the use of pressure ulcer preventing strategies are important to improve the quality of care in the ICU. There is still a need to examine the impact of the evidence of pressure ulcer prevention in the ICU and this review should help to build a framework for future research and protocol development.

Beds↗

PubMed2005

Effectiveness of an alternating pressure air mattress for the prevention of pressure ulcers.

BACKGROUND: studies of the effectiveness of alternating pressure air mattresses (APAMs) for the prevention of pressure ulcers are scarce and in conflict. OBJECTIVE: evaluating whether an APAM is more or equally effective as the standard prevention. DESIGN: randomised controlled trial. SETTING AND SUBJECTS: patients admitted to 19 surgical, internal, or geriatric wards in seven Belgian hospitals were included if they were in need of prevention of pressure ulcers. To define this need, two methods were used randomly: the Braden Scale or the presence of non-blanchable erythema (NBE). METHODS: 447 patients were randomised into either an experimental or a control group. In the experimental group, 222 patients were lying on an APAM (Alpha-X-Cell, Huntleigh Healthcare, UK). In the control group, 225 patients were lying on a visco-elastic foam mattress (Tempur, Tempur-World Inc., USA) in combination with turning every 4 hours. Both groups had identical sitting protocols. RESULTS: there was no significant difference in incidence of pressure ulcers (grade 2-4) between the experimental (15.6%) and control group (15.3%) (P = 1). There were significantly more heel pressure ulcers in the control group (P = 0.006). There was an interaction effect between the risk assessment method and preventive measures for the development of all pressure ulcers and sacral pressure ulcers. CONCLUSION: fewer patients developed heel pressure ulcers on an APAM. Patients identified as being in need of prevention based on the presence of NBE had a tendency to develop fewer pressure ulcers on an APAM. Patients identified as being in need of prevention, based on the Braden Scale, appeared to develop more sacral pressure ulcers on an APAM.

Aged↗

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↗

PubMed2001

Mean blood pressure, pulse pressure and grade of hypertension in untreated hypertensive patients with sleep-related breathing disorder.

OBJECTIVE: To test the hypothesis that sleep-related breathing disorder (SRBD) is associated with increasing severity of cardiovascular risk markers. DESIGN: A cross-sectional study of sleep laboratory patients. SETTING: University Hospital Sleep Disorders Centre. PATIENTS: We studied 591 patients referred for a sleep study, all of them without a history of systemic hypertension. INTERVENTIONS: Clinical interview, two unattended sleep studies, and assessment of office blood pressure, cholesterol concentration, alcohol and nicotine consumption and daytime blood gases. MAIN OUTCOME MEASURE: Post-hoc analysis of different cardiovascular risk markers: mean blood pressure, pulse pressure, and the type and grade of systemic hypertension. RESULTS: Patients were classified as normotensive (blood pressure < 140/90 mmHg, n = 228) or hypertensive (blood pressure > or = 140/90 mmHg, n = 363) according to office blood pressure measurements. Mixed (systolic and diastolic) hypertension was the most common type of hypertension (n = 182), followed by isolated diastolic hypertension (n = 101), borderline isolated systolic hypertension (n = 70), and isolated systolic hypertension (n = 10). The frequency of mixed hypertension increased with SRBD activity (P < 0.05) and respiratory disturbance index (RDI; the number of breathing disorders per hour of estimated sleep time) was increased in those with mixed hypertension compared with those with normotension (24.8 compared with 15.7; t test: P < 0.01). In hypertensive patients classified as having grades 1 -3 of hypertension (n = 265, 80 and 18, respectively), there was a progressive increase in RDI (18.9, 27.2 and 30.3, respectively, P < 0.01). Mean blood pressure increased significantly with RDI. Pulse pressure increased significantly with age (P < 0.001), but was unrelated to the degree of SRBD. CONCLUSION: We conclude that mean blood pressure and the severity of hypertension, but not pulse pressure, increase with the severity of the SRBD.

Adult↗

PubMed2003

Peripheral blood pressure measurement is as good as applanation tonometry at predicting ascending aortic blood pressure.

BACKGROUND: The Sphygmocor system purports to be able to assess ascending aortic blood pressure using a transfer function. It has been shown to be accurate when data obtained invasively are used, but has not been tested prospectively using data obtained non-invasively. OBJECTIVE: To investigate the accuracy of this equipment when measurements are obtained non-invasively, as would normally be the case in the clinic setting. DESIGN AND METHODS: The study was observational. Ascending aortic pressure measurements were taken simultaneously with radial artery pressure wave recordings for estimation of ascending aortic blood pressure, in 28 patients undergoing diagnostic cardiac catheterization. RESULTS: The transfer function in the Sphygmocor system significantly underestimated invasively measured systolic blood pressure [mean -7.23 +/- 10.07 mmHg; 95% confidence interval (CI) -3.3 to -11.14 mmHg, P = 0.001] and significantly overestimated invasively measured diastolic blood pressure (mean 12.20 +/- 7.14 mmHg; 95% CI 9.43 to 14.97 mmHg, P <0.001). Oscillometrically measured brachial systolic blood pressure was not significantly different from that measured invasively in the ascending aorta (mean 3.36 +/- 10.47 mmHg; 95% CI -0.69 to 7.43 mmHg, P = 0.1), but oscillometric measurement of brachial diastolic blood pressure gave a significant overestimation of that measured invasively (mean 11.70 +/- 7.18 mmHg; 95% CI 8.91 to 14.49 mmHg, P <0.001). CONCLUSIONS The transfer function in the Sphygmocor system is no better at estimating ascending aortic blood pressure than are standard peripheral blood pressure measurements. It may be necessary to derive a new transfer system that is based on data that are acquired entirely non-invasively.

Aged↗

PubMed2002

Systematic error in the determination of nocturnal blood pressure dipping status by ambulatory blood pressure monitoring.

BACKGROUND: Vertical displacement of the arm relative to the heart causes inverse changes in blood pressure of approximately 0.8 mmHg for every centimetre change in arm position. Therefore a potential confounding issue in assessing diurnal variation in blood pressure during ambulatory blood pressure monitoring (ABPM) is arm position during sleep. An increase in the number of patients with 'excessive' nocturnal dipping (> 20% decrease in night/day blood pressure) was observed following the creation of an instructional videotape in which patients were advised to muffle the noise of the monitor with a pillow at night. This raised the possibility that patients were placing their arm on top of the pillow reducing nocturnal blood pressure readings. DESIGN: Ambulatory blood pressure monitoring data from 184 patients prior to and from 193 patients following specific instructions not to put their arm on top of the pillow was examined. RESULTS: Following the instructions, the percentage of patients with 'excessive' nocturnal dipping in blood pressure decreased (excessive systolic dipping 17.4 versus 8.8%, P = 0.014; excessive diastolic dipping 37 versus 24.4%, P = 0.01). Consistent with an increase in the ratio of nocturnal/day pressures, there was an increase in the percentage of patients with inadequate nocturnal dipping (< 10% decrease in night/day blood pressure; systolic dipping 33.7 versus 45.6%, P = 0.02; diastolic dipping 13.0 versus 31.6%, P < 0.001) CONCLUSION: Instructing patients to avoid resting their arm on a pillow at night has a substantial effect on the classification of nocturnal dipping status. Patients need clear instructions not to place their arm on a pillow at night during blood pressure monitoring.

Arm↗

PubMed2004

Topical negative pressure using a drainage pouch without foam dressing for the treatment of undermined pressure ulcers.

UNLABELLED: Topical negative pressure is gaining popularity as an acute and chronic wound management technique. In general, foam dressing is applied to the wound surface to maintain negative pressure. Due to the potential for clogging by the foam dressing, topical negative pressure cannot be used when there is a high volume of necrotic tissue or massive infection present. In this study, topical negative pressure was applied using a drainage pouch without any dressing. Topical negative pressure was applied to 8 patients with 9 pressure ulcers complicated by undermining. This approach was effective in the treatment of all 9 ulcers and allowed the wounds to be visualized while maintaining negative pressure. Since this technique can be performed without foam dressing, it can be used to treat early-stage infectious pressure ulcers in which there is a lot of necrotic tissue. CONCLUSION: Topical negative pressure without dressing is an extremely effective treatment of pressure ulcers complicated by undermining.

Adult↗

PubMed1985

Capillary pressures in rat intestinal muscle and mucosal villi during venous pressure elevation.

Whole-organ experiments designed to estimate the capillary filtration coefficient require information about the numerical relationship between capillary pressure and venous pressure. Indirect estimates using isogravimetric and isovolumetric methods indicate that 62-85% of a step change in venous pressure reaches the intestinal capillaries, taken as a whole. We have made direct measurements of capillary pressure with a servo-null micropressure system in the microcirculation of both the intestinal muscle and the mucosal villi of rats during local elevation of venous pressure. Consistent regional differences in the relationship between capillary pressure and venous pressure were observed. During increased venous pressure, submucosal arterioles constricted, while muscularis arterioles dilated. The diameter changes of the small arterioles were consistent with blood flow redistribution from mucosa to muscle during venous pressure elevation, but inconsistent with a pure myogenic response. These data raise questions about the exact role for the expression of the myogenic response during venous pressure elevation in the intestine and about previous interpretations of whole-organ experiments concerned with intestinal blood flow and fluid exchange.

Animals↗

PubMed1984

Volume-dependent effects of positive airway pressure on intracavitary left ventricular end-diastolic pressure.

To test the hypothesis that the effects of positive end-expiratory airway pressure (PEEP) on intracavitary left ventricular end-diastolic pressure (LVEDP) depend on the ventricular filling conditions under which PEEP is applied, the effects of PEEP on pressure in and around the left ventricle were determined before and after stepwise expansion of intravascular blood volume in 10 closed-chest dogs. Over a range of 0 to 20 cm of water, PEEP progressively increased both intrapericardial and intracavitary right ventricular end-diastolic pressures. These increases in pressure around the left ventricle were approximately linear and were relatively unaffected by volume loading. At the same time, PEEP always decreased transmural LVEDP by decreasing ventricular filling. However, transmural LVEDP fell more when ventricular volume was initially large, due to the nonlinear relationship between left ventricular transmural pressure and volume. As a result, intracavitary LVEDP (which reflected the sum of decreased transmural LVEDP and increased external pressure) increased when baseline ventricular volume was small and decreased when baseline ventricular volume was large. At intermediate volumes the fall in transmural pressure equaled the rise in external pressure, and intracavitary LVEDP did not change. These findings demonstrate that changes due to PEEP in intracavitary LVEDP are a complex function of increased intrathoracic pressure, decreased ventricular filling, and the operative level of left ventricular compliance.

Animals↗

PubMed1986

The relationship between pericardial pressure and right atrial pressure: an intraoperative study.

The objective of this study was to determine the constraining effect of the normal human pericardium. Accordingly, immediately after thoracotomy in nine patients undergoing elective cardiac surgery, we measured mean pericardial surface pressure over the lateral free wall of the left ventricle with a flat balloon as well as mean right atrial pressure while incrementally infusing up to 2.1 liters of Ringer's solution to increase right atrial pressure. In each case, the slope of the relationship between right atrial (range -4 to 20 mm Hg, overall) and pericardial pressures was near unity (1.16 +/- 0.20 mean +/- SD) and the intercept was approximately zero (0.71 +/- 2.48 mm Hg). Correlation coefficients ranged from .86 to .97. These observations suggest that right atrial pressure can be used as an estimate of pericardial surface pressure. If this is the case, true left ventricular preload (i.e., effective distending pressure or transmural diastolic pressure) might be estimated from the difference between left ventricular filling pressure and right atrial pressure, both conveniently measurable clinically by means of a triple-lumen, flow-directed catheter.

Aged↗

PubMed1981

Home blood pressure and circadian variation of blood pressure in the evaluation of hypertensive patients.

Clinical blood pressures measured at clinic by physician were higher than home blood pressures measured at home by patients in the majority of untreated patients with essential hypertension, but equivalent or lower in some patients. Clinic minus home blood pressure (delta P) were correlated with the levels of clinic blood pressure (r = 0.51, p less than 0.005 for systolic; r = 0.35, p less than 0.02 for diastolic blood pressure, respectively). The systolic delta P might be greater in the middle-aged women, especially in the fifties of females than the age-matched males (p less than 0.05). The delta P could not be altered by any antihypertensive drugs with the exception of systolic delta P with diuretic alone. The blood pressure tended to remain more stable throughout the 24-hour period in proportion as the severity of hypertension increased. The observation of circadian variation in blood pressure disclosed that the blood pressure was lower in the morning, but increased gradually, resulting in the relatively high blood pressure between the afternoon and evening in the low renin and volume expanded type of hypertension. On the contrary, the blood pressure was already high in the early morning in hypertensive patients characterized by the accelerated renin-angiotensin system and contracted volume factor.

Adrenal Gland Neoplasms↗

PubMed1980

Skin perfusion pressure on the legs measured as the external pressure required for skin reddening after blanching: a photo-electric technique compared to isotope washout.

The skin perfusion on the calf was measured photo-electrically and by isotope washout technique using external counter pressure by a blood pressure cuff. By the photocell the skin blanching threshold external pressure (BTEP) was recorded on histamine flared red skin. By isotope washout technique the skin blood flow cessation external pressure (FCEP) was recorded using intra-dermal [131I-]-antipyrine mixed with histamine in estimating the skin blood flow. The external pressure was measured with an airfilled plastic cushion connected to a mercury manometer. Over a wide range of pressures as obtained from twenty patients with occlusive arterial disease of the legs, five normal subjects and eleven patients treated for arterial hypertension the values of the two different methods were highly significantly correlated (r = 0.97, P < 0.001). On average the BTEP was equal to the FCEP: 83.9 mmHg (range 18-187) compared to 80.8 mmHg (range 18-158) (P > 0.1). A normal material was obtained from twenty-four subjects measured on the thigh, calf and ankle; the average gradients between the auscultatory brachial mean blood pressure and the BTEP were: thigh 10.7 mmHg (SD 12.7); calf 4.0 mmHg (SD 12.1); ankle 5.1 mmHg (SD 8.7). As compared to the intra-arterial blood pressure the BTEP was found to lie close to the mean blood pressure in normal subjects as well as in hypertensive subjects. The present data indicate that the skin perfusion pressure on the legs can be measured by the rapid photo-electric technique. The clinical application and sources of error are discussed.

Adult↗