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Birth weight is inversely correlated to adult systolic blood pressure and pulse pressure in type 1 diabetes.

In the general population, there is an inverse relationship between birth weight and adult systolic blood pressure. Because blood pressure in diabetic patients at least in part seems to be regulated by different mechanisms than in nondiabetic subjects, it is not known whether a similar correlation exists in diabetic individuals. Therefore, we obtained data on birth weight from original birth certificates in 1543 type 1 diabetic patients. Blood pressure was measured auscultatorily on a single occasion. In the 1225 patients born at term (after 37 weeks of gestation), the age- and sex-adjusted regression coefficients between systolic blood pressure and birth weight was -1.90 mm Hg/kg (95% confidence interval [CI], -3.71 to -0.09). The finding remained unchanged after adjustment for body mass index, current smoking, duration of diabetes, social class, antihypertensive therapy, glomerular filtration rate, glycemic control, and elevated albuminuria. The regression coefficient between birth weight and pulse pressure was of a similar magnitude. The age-adjusted regression coefficient between systolic blood pressure and birth weight seemed stronger in females (-3.34 mm Hg/kg; 95% CI, -6.06 to -0.62) than in males (-0.42 mm Hg/kg; 95% CI, -2.80 to 1.95), although this difference was not statistically significant. As a new finding, we report an inverse relationship between weight at birth and systolic blood pressure and pulse pressure in adult type 1 diabetic patients. Given the deleterious effects of elevated arterial blood pressure in diabetes, the impact of intrauterine growth retardation on the development of end-organ damage needs to be clarified.

Adult↗

Sodium and volume sensitivity of blood pressure. Age and pressure change over time.

Salt sensitivity has been implicated in the age-related increase in blood pressure. We studied the reproducibility of a rapid method for assessing sodium sensitivity and resistance of blood pressure as well as the effect of age on this phenomenon. Blood pressure after volume expansion with 2 l intravenous saline (0.9%) over 4 hours was compared with that after 1 day of 10 mmol sodium chloride intake and 3 and 40 mg oral doses of furosemide. Normal and hypertensive subjects (n = 28) were studied twice within a year. Cross-sectional observations of the effect of age were made from studies in 230 hypertensive and 430 normotensive subjects. Longitudinal observations of blood pressure change over time were made 10 or more years after categorization of sodium responsivity in 31 subjects. The blood pressure response was reproducible in 28 subjects studied twice (r = 0.56, p less than 0.002). Four subjects changed salt-responsiveness status and six were indeterminate on restudy. Sodium sensitivity of blood pressure increased significantly with increasing age in the entire population (n = 660, r = -0.38, p less than 0.001). The relation was more striking in hypertensive subjects (n = 230, r = -0.31, p less than 0.001) in whom a progressive increase in salt sensitivity with decades was seen than in the normotensive group (n = 430, r = -0.19, p less than 0.01) in whom salt sensitivity was not observed until the sixth decade. Salt-sensitive subjects had a significantly greater increase in systolic (p less than 0.001) and diastolic (p less than 0.01) pressure over time than those who were salt-resistant. Salt sensitivity is a reproducible phenomenon that is related to the age-associated increase in blood pressure characteristic of industrialized societies. In addition, salt sensitivity can be shown to be a predictor of subsequent, age-related blood pressure increase.

Adult↗

Kidneys and fluids in pressure regulation. Small volume but large pressure changes.

The human body has multiple blood pressure control mechanisms, each of which serves a special and usually different role in pressure regulation. The nervous pressure controllers usually react within seconds and prevent major rapid changes in pressure when acute extraneous forces act on the circulatory system. Then, within minutes to hours, several intermediately acting pressure controllers become activated. Among the more important of these are the renin-angiotensin-vasoconstriction system and the shift of fluid volume between the blood and interstitial fluids. Finally, after several hours to days, the kidneys readjust body fluid volumes, especially the extracellular fluid and blood volumes, to bring the pressure to a very precise level. This final adjustment usually requires little change in body fluid volume for two reasons. First, the other pressure controllers often have already made most of the needed pressure adjustments. Second, the increase in fluid volume required to cause a major increase in blood pressure is usually surprisingly small; this is true because the whole body blood flow autoregulation mechanism causes a secondary increase in total peripheral resistance.

Animals↗

Relation of pulse pressure and blood pressure reduction to the incidence of myocardial infarction.

The prognostic value of pretreatment pulse pressure as a predictor of myocardial infarction and the relation of pulse pressure and in-treatment diastolic blood pressure reduction to myocardial infarction were investigated in a union-sponsored systematic hypertension control program. In a prospective study, 2207 hypertensive patients with a pretreatment systolic blood pressure greater than or equal to 160 mm Hg and/or diastolic pressure greater than or equal to 95 mm Hg grouped according to tertile of pulse pressure (PP1, < or = 46; PP2, 47 to 62; PP3, > or = 63 mm Hg) were further stratified by the degree of diastolic fall: large (L), > or = 18; moderate (M), 7 to 17; small (S), < or = 6 mm Hg. During an average follow-up of 5 years, 132 cardiovascular events (50 myocardial infarctions, 23 strokes) were observed. Myocardial infarction rates per 1000 person-years were positively related to pulse pressure (PP1, 3.5; PP2, 2.9; PP3, 7.5; PP3 versus PP1, P = .02). Wide pulse pressure was identified as a predictor of myocardial infarction (PP3 versus [PP1 + PP2]: relative risk [RR] = 2.2, 95% confidence interval [CI] = 1.2-4.1), controlling for other known risk factors by Cox regression. A curvilinear relation (resembling a J shape) between diastolic fall and myocardial infarction was observed in patients with the widest pulse pressure, PP3 (L, 9.5; M, 3.9; S, 11.2; L versus M: RR = 2.5, 95% CI = 1.0-6.2; S versus M: RR = 2.9, 95% CI = 1.1-8.0).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Pressure-release tracheal gas insufflation reduces airway pressures in lung-injured sheep maintaining eucapnia.

Although tracheal gas insufflation (TGI) has proved to be a useful adjunct to mechanical ventilation, end-inspiratory as well as end-expiratory pressures may increase. We investigated the ability of continuous-flow TGI to maintain eucapnia while reducing airway pressure (Paw) and tidal volume (VT). Seven sheep (36 +/- 2 kg) were ventilated using the Dräger Evita 4 in the pressure control plus mode where flow is released via the expiratory valve to maintain constant inspiratory pressure. To avoid TGI-generated positive end-expiratory pressure (PEEP), a prototype reverse flow TGI tube was used. Two TGI flows (5 and 10 L/min) were investigated pre- and postsaline lavage-induced lung injury. Inspiratory pressures and VT were significantly reduced as TGI flow increased. At 10 L/min TGI flow the carinal pressures (Pcar) and VT were reduced pre- and postinjury by 15% and 20%, and by 28% and 34%, respectively. Tidal volume to dead space ratio (VD/VT) decreased preinjury from 0.49 +/- 0.1 to 0.18 +/- 0.2 and postinjury from 0.62 +/- 0.1 to 0.33 +/- 0.1 at a TGI flow of 10 L/min. The combination of the reverse flow TGI tube and a ventilator with an inspiratory pressure relief mechanism kept set end-inspiratory and end-expiratory pressures constant. This TGI system effectively reduced set Paw and VT while maintaining eucapnia.

Airway Resistance↗

Coronary back flow pressure is elevated in association with increased left ventricular end-diastolic pressure in humans.

To clarify the effect of left ventricular (LV) diastolic pressure on the coronary pressure-flow relation in humans, the instantaneous diastolic coronary pressure-Doppler flow velocity relation was analyzed at rest and during papaverine-induced maximal vasodilation in 15 patients with angiographically normal coronary arteries. The values for slope (alpha PF) and zero-flow pressure intercept (Pzf index) of the instantaneous diastolic coronary pressure-flow velocity relation were obtained by a linear regression analysis. Although alpha PF did not correlate with LV end-diastolic pressure (EDP), the Pzf index correlated positively with LVEDP both at rest and during maximal vasodilation (r = 0.64, P < 0.05 and r = 0.58, P < 0.05, respectively). Thus, the back pressure to coronary inflow, as indicated by the Pzf index, may be elevated in patients with increased LVEDP, resulting in the rightward shift of the maximally dilated coronary pressure-flow relation and decreased maximal coronary flow and reserve at any given perfusion pressure.

Adult↗

Oxygen therapy, continuous positive airway pressure, or noninvasive bilevel positive pressure ventilation in the treatment of acute cardiogenic pulmonary edema.

OBJECTIVE: To compare the effects of 3 types of noninvasive respiratory support systems in the treatment of acute pulmonary edema: oxygen therapy (O2), continuous positive airway pressure, and bilevel positive pressure ventilation. METHODS: We studied prospectively 26 patients with acute pulmonary edema, who were randomized into 1 of 3 types of respiratory support groups. Age was 69+/-7 years. Ten patients were treated with oxygen, 9 with continuous positive airway pressure, and 7 with noninvasive bilevel positive pressure ventilation. All patients received medicamentous therapy according to the Advanced Cardiac Life Support protocol. Our primary aim was to assess the need for orotracheal intubation. We also assessed the following: heart and respiration rates, blood pressure, PaO2, PaCO2, and pH at beginning, and at 10 and 60 minutes after starting the protocol. RESULTS: At 10 minutes, the patients in the bilevel positive pressure ventilation group had the highest PaO2 and the lowest respiration rates; the patients in the O2 group had the highest PaCO2 and the lowest pH (p<0.05). Four patients in the O2 group, 3 patients in the continuous positive pressure group, and none in the bilevel positive pressure ventilation group were intubated (p<0.05). CONCLUSION: Noninvasive bilevel positive pressure ventilation was effective in the treatment of acute cardiogenic pulmonary edema, accelerated the recovery of vital signs and blood gas data, and avoided intubation.

Acute Disease↗

Spontaneous anorectal pressure activity. Evidence of internal anal sphincter contractions in response to rectal pressure waves.

To characterize spontaneous anorectal pressure activity and a possible relation between the activity in the rectum and the anal canal, 11 healthy female volunteers were investigated. Resting activities were obtained during 1-h recordings with a multi-channel perfused catheter measuring the pressure 1, 2, 3, 7, and 8 cm from the anal verge. In five subjects sequences of rhythmic rectal pressure waves with amplitudes exceeding the maximal anal resting pressure coincided with a similar internal anal sphincter activity, preventing rectal pressure from exceeding the anal pressure at any point. The mean frequency was 5 x min-1 (range, 3-6 x min-1). This may well be a reflex mechanism by which the internal anal sphincter prevents incontinence in the resting state. Low-frequency pressure waves, not previously described, were detected in four women. These pressure waves were attributed to the internal anal sphincter and were named ultra-slow waves type II. The mean frequency and amplitude were 0.16 x min-1 (range, 0.15-0.17 x min-1) and 24 cm H2O (range, 11-41 cm H2O), respectively. The function of these pressure waves is unknown.

Adult↗

A simple device for the direct measurement of mean arterial pressure and for calibration of arterial pressure monitors.

A simple, inexpensive mechanical device is described for the direct continuous measurement of mean arterial pressure. It can be assembled in minutes using a few dollars worth of sterile components commonly available in an intensive care unit. Mean arterial pressure determined in patients with this device differs by 1.6 mmHg +/- 1.1 SD from mean arterial pressure simultaneously measured by properly calibrated Hewlett-Packard electronic monitors (N = 5), a non-significant difference. Similar agreement was obtained when the device was tested using a commercial blood pressure system calibrator as the pressure source. This device also allows rapid static calibration of electronic pressure transducers across the full range of human blood pressure using a 3 ml syringe as the pressure source and an aneroid gauge, or mercury column, as the pressure standard.

Biomedical Engineering↗

Effect of low dietary calcium intake on blood pressure and pressure natriuresis response in rats: a possible role of the renin-angiotensin system.

Dietary Ca is an important modulator of blood pressure in humans and rats. Since the kidney plays a key role in the pathogenesis of hypertension, the effects of a low Ca diet (0.01% Ca) on blood pressure and pressure natriuresis response were studied in normotensive Sprague-Dawley rats. In addition, a possible role of the renin-angiotensin system in the development of hypertension and an altered pressure natriuresis response resulting from low dietary Ca intake was examined. In the low Ca diet group, systolic blood pressure measured by the tail-cuff method was significantly higher than in the normal Ca diet group (1,1% Ca) 1 week after the diet (1 13.0 +/- 7.1 vs. 105.0 +/- 9.5mmHg, p < 0.05). After 4 weeks, the hypertension was more pronounced. Low dietary Ca intake significantly inhibited the water and sodium excretory responses to acute elevation of renal perfusion pressure by tightening an infrarenal aortic constriction. Treatment with an inhibitor of angiotensin-converting enzyme, captopril (30 mg/kg/day), completely abolished the elevation of blood pressure and attenuated the reduced pressure natriuresis response observed in Ca-deficient rats. Although plasma renin activity was not different between the low and normal Ca diet groups after the 2-week dietary regimen, the pressor response to angiotensin II was enhanced by 30% in the low Ca diet group and there was a significant difference in the pressor response between the two groups. These results suggest a possible involvement of the renin-angiotensin system in the development of hypertension and an inhibitory effect on the pressure natriuresis response caused by low dietary Ca intake, via an enhanced sensitivity to angiotensin II.

Analysis of Variance↗

Inactivation of hepatitis A virus by high-pressure processing: the role of temperature and pressure oscillation.

Inactivation of hepatitis A virus (HAV) in Dulbecco's modified Eagle medium with 10% fetal bovine serum was studied at pressures of 300, 350, and 400 MPa and initial sample temperatures of -10, 0, 5, 10, 20, 30, 40, and 50 degrees C. Sample temperature during pressure application strongly influenced the efficiency of HAV inactivation. Elevated temperature (> 30 degrees C) enhanced pressure inactivation of HAV, while lower temperatures resulted in less inactivation. For example, 1-min treatments of 400 MPa at -10, 20, and 50 degrees C reduced titers of HAV by 1.0, 2.5, and 4.7 log PFU/ml, respectively. Pressure inactivation curves of HAV were obtained at 400 MPa and three temperatures (-10, 20, and 50 degrees C). With increasing treatment time, all three temperatures showed a rapid initial drop in virus titer with a diminishing inactivation rate (or tailing effect). Analysis of inactivation data indicated that the Weibull model more adequately fitted the inactivation curves than the linear model. Oscillatory high-pressure processing for 2, 4, 6, and 8 cycles at 400 MPa and temperatures of 20 and 50 degrees C did not considerably enhance pressure inactivation of HAV as compared with continuous high-pressure application. These results indicate that HAV exhibits, unlike other viruses examined to date, a reduced sensitivity to high pressure observed at cooler treatment temperatures. This work suggested that slightly elevated temperatures are advantageous for pressure inactivation of HAV within foods.

Animals↗

MDS+ items not contained in the pressure ulcer RAP associated with pressure ulcer prevalence in newly institutionalized elderly.

All federally funded facilities are required to use the Minimum Data Set Plus (MDS+) for functional assessment of their residents. Within the MDS+ there are 18 specific conditions addressed through Resident Assessment Protocols (RAPs). The purpose of this study was to determine if MDS+ items not included in the pressure ulcer RAP correlated with pressure ulcer prevalence in newly institutionalized elderly. Additionally, this study examined whether the addition of nutritional status information to the correlated items increased association with pressure ulcer prevalence. Data were collected through a retrospective chart review of 990 residents over age 65 at eight nursing homes. Pressure ulcer prevalence was 33.2%. Nineteen of 59 non-RAP MDS+ items were correlated with pressure ulcer prevalence. Logistic regression determined that 10 MDS+ items predicted pressure ulcer prevalence in 28.88% of the subjects. Including serum albumin in the logistic model increased the predictability for pressure ulcer prevalence to 36.3%. Results of this study demonstrate the strong association between nutrition and pressure ulcer prevalence and the need to revise the pressure ulcer RAP.

Aged↗

Blood pressure, edema and proteinuria in pregnancy. 4. Blood pressure relationships.

The significance of these and related data will be discussed in greater detail during the subsequent course of this workshop. For now, we can sum up our findings with the following general statements concerning this analysis: 1. Blood pressure elevation occuring alone during the course of pregnancy, in the absence of edema and/or proteinuria, affects perinatal survival adversely. 2. This relationship is most marked among nulliparas in the age range 20-34 years and is less pronounced, but still evident, in young nulliparas and in multiparas of comparable age. 3. The effect is greater among black patients than among white patients in the median-aged nulliparas and multiparas, but this difference is not mirrored in the young nulliparas studied. 4. Blood pressure elevations during weeks 20-28 of pregnancy result in much higher subsequent perinatal losses in white nulliparas (both median and young age groups) than comparable elevations earlier or later in pregnancy. 5. Among black nulliparas of median age, maximal blood pressure effect on outcome is encountered at the sixteenth week (the earliest available data), with continuing significant increases until the twenty-eighth week, and there is another increment at term. In younger black patients, the results from 20 through 28 weeks parallel those seen in white patients, but with an additional peak at term. 6. among multiparas, maximal effect occurs at 24-28 weeks in both black and white groups. 7. The critical blood pressure levels are significantly lower in early pregnancy than in late pregnancy. 8. Critical levels of blood pressure with advancing pregnancy appear to parallel the trend in mean blood pressures determined to exist for this series. 9. Utilizing blood pressure distribution data to set limits statistically, we find very meaningful increments in perinatal mortality rates for nulliparas presenting blood pressure elevations beyond the 95 percentile point. This holds also for diastolic or systolic levels when these are examined independently because neither alone yielded more convincing data than blood pressure combinations condidered together.

Adolescent↗

Skin perfusion responses to surface pressure-induced ischemia: implication for the developing pressure ulcer.

This study describes alterations in skin perfusion in response to step increases in surface pressure, before and after long-term (5 hr) exposure to pressure-induced ischemia. A provocative test was developed in which surface pressure was increased in increments of 3.7 mmHg until perfusion reached an apparent minimum by a computer-controlled plunger that included a force cell, a laser Doppler flowmeter to determine perfusion, and a thermistor to monitor skin temperature. Force was applied to the greater trochanters of adult male fuzzy rats. Skin perfusion (n=7) initially increased with low levels of surface pressure (up to 13.9+/-1.9 mmHg) and then decreased with further increases in pressure, reaching minimum (zero) perfusion at 58.2+/-3.64 mmHg. After pressure release, reactive hyperemia (3 x normal) was observed, with levels returning to normal within 15-30 min. The provocative test was then applied after a 5-hr ischemic episode (produced by 92 mmHg) and 3 hr of recovery. A comparison of responses between stressed and unstressed skin revealed: elevated (63%) control perfusion levels; loss of the initial increase in perfusion with low levels of increasing pressure; a depression (45%) in the hyperemic response with delayed recovery time; and a decrease (54%) in amplitude of low frequency (<1 Hz) rhythms in skin perfusion. Skin surface temperature gradually increased both during the control period and the period of incremental increases in surface pressure (total DT=3.3 degrees C). The results suggest a compromised vasodilator mechanism(s). The provocative test developed in this study may have clinical potential for assessing tissue viability in early pressure ulcer development.

Animals↗

[Pressure sores: evaluation of the systematic use of special surfaces for managing pressure sores in the intensive care unit of the Tarrasa Hospital, Spain].

Pressure sores are a major challenge for healthcare systems. Patients admitted to intensive care units are an important risk group for pressure sores. Systematic use of a protocol employing special surfaces to manage pressure is a basic measure for preventing pressure sores in institutionalized patients. In a study carried out in the Intensive Care Unit of the Hospital of Terrassa (Spain), the incidence of pressure sores before and after introducing a prevention protocol that included the systematic use of special surfaces to manage pressure was compared. The incidence of pressure sores in patients admitted in 1998 and 1999 was studied. Sore locations were recorded. The results of three periods were examined: before introducing the protocol (6.4% incidence), after introducing a protocol (1.1%), and after use of the protocol was consolidated (0%). The results of the study suggest that the systematic use of special surfaces to manage pressure, in accordance with a prevention protocol, is a basic measure for reducing the incidence of pressure sores in patients admitted to intensive care units.

Critical Care↗

Comparison of alpha 1-adrenoceptor agonists in canine urethral pressure profilometry and abdominal leak point pressure models.

PURPOSE: We describe and compare the usefulness of 3 minimally invasive dog urethral function models to demonstrate the efficacy potential of alpha 1 agonists for stress urinary incontinence. From this overall composite dataset the efficacy profiles of the alpha 1A selective agonist A-61603 and the active metabolite of midodrine ST-1059 were specifically compared. MATERIALS AND METHODS: Isoflurane anesthetized multiparous female beagle dogs were used in all studies. Intraurethral pressure was measured using a 7Fr balloon catheter. Profilometry was performed using an 8Fr Millar transducer catheter. Bladder pressure required to produce leakage in response to external abdominal ballottements of increasing intensity was measured using a 5Fr transurethral catheter. Agonist responses were measured before and after increasing cumulative intravenous doses of each compound in each test. RESULTS: Agonist induced increases in maximal urethral closure and leak point pressure strongly correlated in linear fashion (R(2) = 0.94), as did measurements of agonist induced increases in proximal intraurethral pressure using the microtransducer or balloon catheter technique (R(2) = 0.87). A dose of 0.01 to 1 nmol./kg. A-61603 and 10 to 1,000 nmol./kg. ST-1059 intravenously each caused dose dependent increases in maximum urethral closure, leak point and intraurethral pressure. CONCLUSIONS: While the dose range for which alpha 1 agonists affect urethral pressure was adequately predicted by any of the 3 methods used, the leak point pressure assay described has the advantage of being a dynamic test that directly evaluates efficacy to protect against leakage caused by increases in abdominal pressure. This leak point pressure test appears be useful for the preclinical evaluation of compounds used to treat stress urinary incontinence.

Adrenergic alpha-1 Receptor Agonists↗

[Continuous tracheal gas insufflation during pressure control ventilation with a pressure relief valve].

OBJECTIVE: To establish the method of continuous tracheal gas insufflation (CTGI) and investigate the role of pressure relief valve (PRV) in limiting high peak airway pressure induced by CTGI. METHODS: CTGI device was made by authors. Nine healthy mongrel dogs were mechanically ventilated by using Evita 2 (Drager Inc.). PRV was inserted into the ventilatory circuit for selected experiment steps and adjusted a threshold pressure equal to the preset inspiratory pressure. PCV, PCV + CTGI (TGI group) and PCV + CTGI + PRV (PRV group) were conducted in different inspiration/expiration (I/E) ratio of 1:2 and 2:1. Gas exchange, lung mechanics and hemodynamics status were monitored at the constant set inspiratory pressure of PCV. RESULTS: At the same I/E ratio, peak airway pressure in TGI group was higher than that of PRV and PCV group (P < 0.01), whereas PRV group maintained the preset inspiratory pressure as PCV group. At the different I/E ratio, peak airway pressure in TGI (2:1) group was higher than that of TGI (1:2) group(P < 0.01). PaCO2 in TGI and PRV group decreased significantly than that of PCV, TGI group was more lower than PRV group, PaO2, hemodynamics and oxygenation remained unchanged in all groups. CONCLUSIONS: The CTGI device is effective in improving alveolar ventilation with no significant influence on hemodynamics and oxygenation; A pressure relief valve is necessary to ensure the safe use of CTGI.

Animals↗

[Circadian pressure variability and pressure peaks during treatment of mild to moderate essential hypertension with felodipine].

It is not yet known how blood pressure variability contributes to the vascular changes associated with hypertension, but 2 possibly relevant factors are mean blood pressure levels over time and pressure peaks. It has been observed that patients in whom the variability in 24-hour blood pressure is low have a lower prevalence and severity of target organ damage. We carried out a whole-day continuous intraarterial blood pressure recording (Oxford method) in 12 essential hypertensive patients after a 2-week placebo period and after a 4-week felodipine treatment, administered in an extended release formulation, 10 mg once daily at 7 am. Felodipine significantly lowered systolic and diastolic blood pressure values throughout the 24 hours (p less than 0.005 to 0.001). Also, hourly variabilities of systolic and diastolic blood pressure during whole-day monitoring were significantly reduced (p less than 0.05 to 0.001), evaluated on the basis of the hourly means of standard deviation of systolic and diastolic blood pressure. In addition, felodipine significantly lowered the values of blood pressure reached during both dynamic exercise (bicycle ergometer, p less than 0.001) and isometric exercise (handgrip, p less than 0.001).

Adult↗