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At least 595 records · Page 33Linked to original sources
PubMed2004

[Effects of nitrendipine on circadian variation of blood pressure in inpatients with renal parenchymal hypertension: assessment by ambulatory blood pressure monitoring].

OBJECTIVE: To study the effect of once-daily administration of a nitrendipine tablet 10 mg on 24-hour ambulatory blood pressure in inpatients with renal parenchymal hypertension. METHODS: Sixteen patients participated in the present study, and one patient was withdrawn because the baseline office blood pressure was less than 140/90 mmHg. In the baseline period, ambulatory blood pressure was monitored every 30 minutes for 30 hours. After the baseline measurement, nitrendipine 10 mg was orally administered once daily every morning for 7 days. The 30-hour ambulatory blood pressure monitoring was repeated after Day 6. RESULTS: Fifteen patients (aged 64.9 +/- 15.0 years) completed the study protocol. Baseline office blood pressure was 157.9 +/- 17.5/84.7 +/- 12.5 mmHg (mean +/- SD). Nitrendipine 10 mg tablets significantly reduced both systolic blood pressure (SBP) and diastolic blood pressure (DBP) at least for 11 hours after administration compared with those at baseline. The rate of "Decrease" (reduction in blood pressure > or = 20/10 mmHg and/or achieved blood pressure < 140/90 mmHg at trough point) was 60.0% (9/15). Eleven patients were considered as effective cases at peak point (maximal reduction in blood pressure > or = 20/10 mmHg). The rate of "Decrease" in effective cases at peak point was 72.7% (8/11). CONCLUSION: These results suggest that a once-daily administration of nitrendipine 10 mg tablets is effective for the 24-hour control of blood pressure in patients with renal parenchymal hypertension.

Administration, Oral↗
PubMed1989

Endoscopic measurement of variceal pressure in cirrhosis: correlation with portal pressure and variceal hemorrhage.

This study evaluated the clinical application of a pressure-sensitive gauge that allows the noninvasive measurement of the pressure of esophageal varices at endoscopy. The study was performed in 70 patients with cirrhosis and portal hypertension. Among them, 47 had bled from the varices and 23 had varices but had not bled. In addition to measurements of variceal pressure, the size of the varices was estimated semiquantitatively at endoscopy. This allowed an estimate of the tension on the wall of the varices as the product of the transmural pressure and the estimated radius of the varices. Most patients had a standard hemodynamic evaluation of portal hypertension, with measurements of wedged and free hepatic venous pressures, and of azygos blood flow. These were performed within 24 h of the variceal pressure measurements. Variceal pressure was significantly higher in bleeders than in nonbleeders (15.7 +/- 2.8 vs. 12.1 +/- 2.6 mmHg, p less than 0.001) in spite of a similar portal pressure in both groups (20.1 +/- 5.1 vs. 20.4 +/- 7.6 mmHg, NS). More than 60% of the bleeders, but only 22% of the nonbleeders had a variceal pressure greater than or equal to 15 mmHg (p less than 0.005). Among nonbleeders, variceal pressure was higher in patients with large varices (13.9 +/- 2 mmHg, n = 9) than in those with small varices (10.9 +/- 2.4 mmHg, n = 14) (p less than 0.01). Estimates of variceal wall tension further exaggerated the differences between bleeders and nonbleeders (66.1 +/- 22.6 vs. 32.0 +/- 19.8 mmHg.mm, p less than 0.001). More than 50% of bleeders, but just 9% of nonbleeders had an estimated variceal tension greater than 50 mmHg.mm (p less than 0.001). Our findings support the role of an increased variceal pressure in the pathogenesis of variceal hemorrhage, and suggest that this noninvasive technique can be valuable in assessing the risk of variceal hemorrhage in patients with portal hypertension.

Endoscopes↗
PubMed1987

Circadian rhythm of blood pressure in hypertensive adult patients: implications for blood pressure determination.

To determine whether traditionally timed (0800, 1600, and 2400 hr) blood pressure assessments by nurses reflect circadian peaks and troughs, blood pressure was measured indirectly every 2 hr for 24 hr with a mercury sphygmomanometer and a Sprague-Rapaport stethoscope in a sample of 31 hypertensive adult patients in a university hospital. Pooled mean systolic and diastolic readings portrayed a circadian rhythm with the peak occurring most frequently at 1600 and the trough at 0400 hr. The mean range of variability was 29.54 mm Hg for systolic pressure and 21.54 mm Hg for diastolic pressure. Two-tailed t tests demonstrated statistically significant (P less than .001) differences between peak and 0800 systolic pressure, peak and 2400 systolic pressure, peak and 0800 diastolic pressure, and peak and 2400 diastolic pressure. No significant differences were found between peak and 1600 systolic and diastolic assessments. There were statistically significant (P less than .001) t test differences between trough systolic and diastolic pressure and traditionally timed blood pressure readings. These findings have clinical nursing implications for the timing of blood pressure assessments of hospitalized hypertensive adult patients.

Adult↗
PubMed1987

Measurement of intrahepatic pressure as an index of hepatic sinusoidal pressure.

Intrahepatic pressure was measured in 148 patients with liver disease (32 outpatients, 116 inpatients) and 13 controls with almost normal liver histology (inpatients), with a 23-gauge needle (inner diameter 0.38 mm). Intrahepatic pressure was significantly elevated in the group order of chronic active hepatitis without bridging necrosis (n = 17, 9.2 +/- 3.0 mm Hg), chronic active hepatitis with bridging necrosis (n = 24, 12.3 +/- 5.7), and posthepatitic liver cirrhosis (n = 65, 18.8 +/- 4.2), compared with controls (n = 13, 6.8 +/- 2.7), whereas it was not elevated in the group of idiopathic portal hypertension (n = 9, 7.8 +/- 2.5 mm Hg), acute hepatitis (n = 10, 8.4 +/- 2.6 mm Hg), and chronic persistent hepatitis (n = 23, 7.9 +/- 2.7 mm Hg), compared with controls. As complications, four patients had abdominal discomfort continuing for more than a day; however, patients were allowed to walk after they had rested on their beds for 30 min. In 37 patients (27 with cirrhosis, seven idiopathic portal hypertension, and three others), portal vein and/or hepatic vein catheterization was performed during the same procedure of intrahepatic pressure measurement. Intrahepatic pressure showed significant correlations with corrected wedged hepatic vein pressure (r = 0.91), portohepatic gradient (r = 0.69), wedged hepatic vein pressure (r = 0.79), and portal vein pressure (r = 0.68). Slopes were 0.97, 0.83, 0.66, and 0.65, respectively. In conclusion, intrahepatic pressure reflects hepatic sinusoidal pressure (corrected wedged hepatic vein pressure), and intrahepatic pressure starts to elevate at the stage of chronic active hepatitis.

Acute Disease↗
PubMed1994

Increase in blood pressure reproducibility by repeated semi-automatic blood pressure measurements in the clinic environment.

OBJECTIVE: To evaluate whether increasing the number of blood pressure readings obtained in the clinic environment increases the blood pressure reproducibility. PATIENTS: Thirteen mild essential hypertensive patients studied in the outpatient clinics, following withdrawal of antihypertensive treatment for 4 weeks. METHODS: The systolic and diastolic blood pressures were measured three times, using a mercury sphygmomanometer, with the patient in the sitting position. Measurements were then performed with the patient in the lying position using an oscillometric device (SpaceLabs 90202 or 90207). The device was operated semi-automatically at 3-min intervals until 25 readings had been collected. The same procedure was repeated 4 weeks later. The systolic blood pressure, diastolic blood pressure and heart rate were averaged by considering a progressively greater number of readings, from 1 to 25. The reciprocal of the standard deviation (1/SD) of the mean difference after 4 weeks was taken as the measure of reproducibility. RESULTS: 1/SD increased progressively as the number of semi-automatic blood pressure readings from which the average was calculated increased. For a similar number of blood pressure readings the reproducibility was similar for semi-automatic readings to that for automatic readings obtained by 24-h ambulatory blood pressure monitoring. CONCLUSION: Multiple blood pressure readings obtained semi-automatically in the outpatient clinics increase blood pressure reproducibility and make the value similar to that obtained by ambulatory blood pressure monitoring. The advantage of an increase in reproducibility for studies on antihypertensive drugs thus depends on the number of readings, and can also be obtained by semi-automatic measurements in the clinic environment.

Adult↗
PubMed1997

Ambulatory blood pressure, nocturnal blood pressure reduction and plasma catecholamines.

OBJECTIVE AND DESIGN: Controversial data have been reported on plasma catecholamines in hypertensives. Aims of this study were to find whether 24-hour ambulatory blood pressure was correlated with circulating catecholamines and to investigate whether nocturnal blood pressure reduction was associated with baseline plasma catecholamines. Samples for catecholamine determination were obtained in 34 consecutive male subjects after a 30-minute rest and before ambulatory blood pressure monitoring. RESULTS: Hypertensive patients (n = 22; 24-hour blood pressure: 145 +/- 14/94 +/- 6 mm Hg) showed similar norepinephrine and epinephrine levels when compared with normotensives (n = 12; 24-hour blood pressure: 124 +/- 6/81 +/- 6 mm Hg), and higher dopamine values (hypertensives: 64.6 +/- 58; normotensives: 26.2 +/- 31 pg/ml; p < 0.05). A positive correlation was observed between dopamine and diastolic nocturnal blood pressure (p < 0.05) while a negative correlation was found between dopamine and nocturnal diastolic blood pressure reduction (p < 0.025). No significant relationship was observed between both norepinephrine and epinephrine, and 24-hour blood pressures. CONCLUSIONS: Since previous reports have documented malfunctioning of dopaminergic system in hypertension, the higher levels of circulating plasma dopamine found in hypertensive patients in the present study may account for a peripheral compensatory increase. The correlation between dopamine and nocturnal blood pressure fall seems to indicate that the impairment of dopaminergic system may influence the 24-hour blood pressure profile, affecting the nocturnal blood pressure reduction.

Adult↗
PubMed1996

Blood pressure evaluation by noninvasive and traditional methods. Consistencies and discrepancies among photoplethysmomanometry, office sphygmomanometry, and ambulatory monitoring. Effects of blood pressure measurement.

Three hundred eight outpatients referred for hypertension were studied. A continuous beat-to-beat noninvasive recording (Finapres) of blood pressure evaluated the blood pressure increase (9 mm Hg systolic and 4 mm Hg diastolic) induced by office sphygmomanometry. Thereafter, patients underwent a 24-h ambulatory blood pressure monitoring. The evaluation against Finapres showed that office sphygmomanometry overestimates the systolic blood pressure by 3 +/- 36 mm Hg (mean +/- 2 SD) and the diastolic blood pressure by 15 +/- 25 mm Hg (mean +/- 2 SD). Blood pressure monitoring showed similar discrepancies. On the basis of both monitoring (normalcy defined from a population of 550 normotensive subjects) and office sphygmomanometry, patients were considered normotensive, hypertensive (either untreated or under active drug treatment), white coat hypertensive (monitoring below the 95th percentile and sphygmomanometry more than 140/90 mm Hg, either untreated or under active drug treatment), and reverse white coat patients (monitoring over the 95th percentile and sphygmomanometry less than 140/90 mm Hg). Patients showed different levels of alert reaction (the highest in white coat hypertensive and the lowest in reverse white coat hypertensive patients), and a similar increase in blood pressure induced by conventional sphygmomanometry. During initial readings of ambulatory monitoring, blood pressure decreased from the first reading to the third reading. This decrease is related to the increase of blood pressure under sphygmomanometry. Caution should be paid in interpreting results of sphygmomanometry (error level in the single patient as high as +/- 40 mm Hg), and interpreting and averaging results of the first hour of blood pressure monitoring (variably affected by the alert reaction to the clinical environment).

Adolescent↗
PubMed1984

Influence of transmural pressure on retrograde pressure pulse transmission velocity in the canine superior vena cava.

The influence of intrathoracic and intraluminal pressure on venous pressure pulse propagation velocity in the superior vena cava was investigated in acute canine experiments. The propagation velocity of distinct points of the venous pressure curve was measured under different conditions of preload, during expiratory and inspiratory apnea and during positive-negative pressure respiration. Under control conditions transmission velocities varied from 1.07 m/s to 3.29 m/s. After volume expansion propagation velocities rose significantly and varied from 1.09 m/s to 6.48 m/s. During expiratory apnea and at peak negative expiratory pressure, the propagation speed of distinct pressure points was higher than during inspiratory apnea and at peak positive inspiratory pressure. Significant linear correlation coefficients were found between the transmission velocities of different distinct pressure points and the transmural pressure, but not between the propagation speed and the intraluminal pressure.

Animals↗
PubMedDate not supplied

[Effect of negative pressure and occluding cuffs on the intravascular pressure in the lower extremity of the healthy human being].

The effect of local negative pressure on the leg (with a bladder sealed above the knee) and occlusion cuffs (located as close as possible to Poupart's ligament) on the leg intravascular pressure was investigated in recumbency. In two experimental runs 8 healthy volunteers participated. Each of the two exposures was used at two levels: local negative pressure at -50 and -100 mm Hg and occlusion cuffs at +40 and +60 mm Hg with the exposure time averaging 5-7 min. Catheters were inserted into the femoral artery and vein, and arteries and veins of the back of the foot. The arterial pressure remained unchanged during both exposures: local negative pressure and occlusion cuffs. Upon exposure to local negative pressure the venous pressure in the back of the foot (with respect to the atmospheric pressure) did not change and in the femoral vein decreased. Upon exposure to occlusion cuffs the venous pressure in the back of the foot increased noticeably and in the femoral vein decreased slightly. It is concluded that none of the exposures can reproduce the major gravitational effect on leg vessels, i.e. characteristic changes in gradients of the intravascular (transmural) pressure.

Adult↗
PubMed1989

Blood pressure and blood pressure variability following withdrawal of propranolol and clonidine.

The effects of placebo, propranolol, and clonidine on blood pressure and blood pressure variability were examined in 14 subjects who had moderate essential hypertension. Hydrochlorothiazide was given throughout successive 4- to 5-week periods of placebo, propranolol, and clonidine administration. During each treatment period, subjects were admitted twice to the clinical research unit for 24-hour blood pressure monitoring performed during administration of placebo, propranolol and clonidine and repeated 1 to 2 weeks later during the first 24 hours after the abrupt cessation of placebo or drug administration. Blood pressure was recorded at 15-minute intervals using an automated noninvasive recorder (Arteriosonde, Roche, New Jersey). Systolic and diastolic blood pressure readings were averaged and the standard deviation taken as the measure of long-term variability (LTV). Systolic and diastolic blood pressure in sequential overlapping blocks of seven readings were averaged and the standard deviation calculated. Short-term variability (STV) was estimated as the average of the standard deviations of the running means. During placebo administration and withdrawal, systolic and diastolic blood pressures as well as LTV and STV were unchanged. Systolic and diastolic pressures did not differ during propranolol administration from those during propranolol withdrawal or placebo withdrawal. Systolic and diastolic LTV and STV did not differ during propranolol administration and withdrawal from those observed during placebo administration or withdrawal. After clonidine withdrawal, both systolic and diastolic pressures increased to values significantly greater than during clonidine administration. These values were significantly greater than those observed after placebo withdrawal, thereby indicating rebound hypertension. After clonidine withdrawal, seven of fourteen subjects developed systolic pressure rebound; diastolic pressure rebound was observed in three patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Reference data for ambulatory blood pressure monitoring: what results are equivalent to the established limits of office blood pressure?

In 1039 subjects ambulatory blood pressure monitoring was performed to define threshold values, which are equivalent to the established limits of the office blood pressure. Mean values and proportions of elevated single readings were correlated to office blood pressure by regression analyses. To avoid impact of varying sleeping periods on 24 h blood pressure, only daytime readings were considered. Correlations between average daytime blood pressure and office blood pressure were linear: Mean daytime values of 135 mmHg (systolic) and of 84 mmHg (diastolic) were equivalent to the casual blood pressure limits of 140 mmHg and 90 mmHg. Correlations between percentages of elevated single readings and office blood pressure were nonlinear: Proportions of 25% systolic readings greater than 140 mmHg and of 17% diastolic readings greater than 90 mmHg were equivalent to casual blood pressure limits of 140 mmHg and 90 mmHg. On the basis of the regression equations, any result of ambulatory blood pressure recording during daytime can now be evaluated in terms of the established standards of office blood pressure.

Blood Pressure Monitors↗
PubMed2006

Ventilator Y-piece pressure compared with intratracheal airway pressure in healthy intubated children.

OBJECTIVE: Compare airway pressure measurements at the ventilator Y-piece of the breathing circuit (P( Y )) to intratracheal pressure measured at the distal end (P( T )) of the endotracheal tube (ETT) during mechanical ventilation and spontaneous breathing of intubated children. METHODS: Thirty children (age range 29 days to 5 years) receiving general anesthesia were intubated with an ETT incorporating a lumen embedded in its sidewall that opened at the distal end to measure P( T ). Peak inflation pressure (PIP) was measured at P( Y ) and P( T ) during positive pressure ventilation. Just before extubation, all measurements were repeated and imposed resistive work of breathing (WOBi) was calculated at both sites while breathing spontaneously. RESULTS: Average PIP was approximately 25% greater at P( Y ) (19.7 +/- 3.4 cm H(2)O) vs. P( T ) (15.0 +/- 2.9 cm H(2)O), p < 0.01. During spontaneous inhalation P( T ) was 59% lower ({bond}8.5 +/- 4.0 cm H(2)O) vs. P( Y ) ({bond}3.5 +/- 2.0 cm H(2)O), p < 0.01. WOBi measured at P( Y ) (0.10 +/- 0.02 Joule/L) was 86% less than WOBi measured at P( T ) (0.70 +/- 0.40 Joule/L), p < 0.01. CONCLUSIONS: In healthy children P( Y ) significantly overestimates PIP in the trachea during positive pressure ventilation and underestimates the intratracheal airway pressure during spontaneous inhalation. During positive pressure ventilation P( T ) better assesses the pressure generated in the airways and lungs compared to P( Y ) because P( T ) also includes the difference in airway pressure across the ETT tube due to resistance. During spontaneous inhalation, P( T ) reflects the series resistance of the ETT and ventilator circuit, while P( Y ) reflects only the resistance of the ventilator circuit, accounting for the smaller decreases in pressure. Additionally, P( Y ) underestimates the total WOBi load on the respiratory muscles. Thus, P( T ) is a more accurate reflection of pulmonary airway pressures than P( Y ) and suggests that it should be incorporated into ventilator systems to more accurately trigger the ventilator and to reduce work of breathing.

Anesthesia, General↗
PubMed1995

Monitoring of pulmonary arterial diastolic pressure through a right ventricular pressure transducer.

Pulmonary arterial diastolic pressure is an important parameter for hemodynamic monitoring in congestive heart failure. It is traditionally obtained through a pulmonary arterial catheter. If it could be obtained from a sensor in the right ventricle, chronic monitoring would be possible without the use of a pulmonary arterial catheter. This study is based on the hypothesis that pulmonary valve opening and pulmonary arterial diastolic pressure occur at the time of maximum positive rate of pressure development (dP/dt) in the right ventricle, when the pressures should be equal. Thus, right ventricular pressure at the time of maximum dP/dt (PAD index) should be a reasonable estimate of pulmonary arterial diastolic pressure. Eight patients with heart failure were catheterized and exposed to hemodynamic stress. Right ventricular and pulmonary arterial pressures were simultaneously recorded from a Millar (Houston, TX) catheter with two pressure transducers. The distal transducer was positioned in the bifurcation of the pulmonary artery and the proximal transducer was placed in the right ventricle. Pulmonary arterial diastolic pressure and PAD index were stored beat by beat on a bed-side computer. Acceptable recordings were obtained in all patients. Recordings from the individual patients showed a good covariation between PAD index and pulmonary arterial pressure during different hemodynamic manuevers, except during infusion of dobutamine, when the correlation was not as good. Pulmonary arterial diastolic pressure may be estimated from a transducer in the right ventricle, thus eliminating the need for a permanent pulmonary arterial catheter in an implantable hemodynamic monitoring system. Further studies are needed to verify the correlation on a long-term basis.

Aged↗
PubMed2005

Intracuff pressures of endotracheal tubes in the management of airway emergencies: the need for pressure monitoring.

STUDY OBJECTIVE: Excessive pressure exerted on the tracheal mucosa is an avoidable factor implicated as a cause of damage after intubation of the trachea with cuffed tubes. Many patients are intubated in the out-of-hospital setting by emergency medical teams. The time spent in the out-of-hospital setting could very well be long enough for tracheal mucosal damage to occur if cuff pressure is not controlled. The objective of this study is to assess the incidence of intracuff excessive pressure in the out-of-hospital setting. METHODS: We performed an observational prospective study. Every patient who required tracheal intubation was included in the study, regardless of indication. When the patient was stabilized, the cuff was connected to a manometer, and pressure was systematically recorded. Corrections to inflation were performed if necessary to achieve a cuff pressure of 14 to 27 cm H2O. RESULTS: One hundred seven patients were included. Eighty-five were out-of-hospital patients and 22 were transfers between 2 hospitals who had been previously intubated when the mobile intensive care unit team arrived. The first recorded cuff pressures were greater than 27 cm H2O among 79% of patients (85/107), with a mean pressure of 56 cm H2O (SD+/-34 cm H2O) in out-of-hospital patients and 69 cm H2O (SD+/-37 cm H2O) for transferred patients. Pressure correction was made in 72% of patients (77/107). There were corrections in 69% (59/85) of out-of-hospital patients and 82% (18/22) of transferred patients. CONCLUSION: This study revealed that the majority of cuff pressures exceeded safe pressure and required correction. Frequent measurement and adjustment of cuff pressure has been recommended, but this method requires a specific manometer.

Emergency Medical Services↗
PubMed2004

Foot pressures during level walking are strongly associated with pressures during other ambulatory activities in subjects with diabetic neuropathy.

OBJECTIVE: To assess the relationship between foot pressures measured during level walking and other types of ambulatory activity in subjects with diabetes mellitus (DM) and peripheral neuropathy (PN). DESIGN: Descriptive survey with repeated measures. SETTING: University medical center. PARTICIPANTS: Convenience sample of 16 ambulatory subjects with DM and PN. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak pressure and pressure-time integral (PTI) at the heel, great toe, first metatarsal head (MT1), and third metatarsal head (MT3) during level walking, ramp climbing, stair climbing, and turning at a self-selected speed. RESULTS: Peak pressure and PTI during level walking correlated highly with pressures during ramp climbing (r range,.85-.97) and turning (r range,.75-.96) at all regions examined and with pressures during stair climbing at MT1 and MT3 (r range,.84-.91). Correlations between pressures during level walking and stair climbing were moderate at the great toe (r range,.46-.57) and poor at the heel (r range, -.12 to -.06). With few exceptions, pressures during ramp climbing, stair climbing, and turning were less than (P<.008) or equal to pressures during level walking. We found no activity-related differences in peak pressure or PTI independent of the effects of preferred walking speed. CONCLUSIONS: Results support the clinical evaluation of peak pressure during level walking as an efficient method to screen for maximum levels of stress on the foot as patients with DM and PN perform their daily activities.

Activities of Daily Living↗
PubMed1998

The acute pressure natriuresis response blunted and the blood pressure response reset in the normal pregnant rat.

OBJECTIVES: Our purpose was to test the hypothesis that the acute pressure natriuresis curve was reset in pregnancy to facilitate the volume expansion. STUDY DESIGN: Studies were done with 14- to 16-day pregnant (n = 8) and age-matched virgin female (n = 6) Sprague-Dawley rats that were under general anesthesia. The left kidney was denervated, and mechanical clamps were placed on the aorta above and below the renal arteries for manipulation of renal perfusion pressure. Rats received intravenous 0.9% sodium chloride (1.5% body weight/h) and a cocktail of vasoactive factors to suppress variation in endogenous hormones. Renal perfusion pressure was varied acutely from 125 to 95 mm Hg, and glomerular filtration rate, renal plasma flow, sodium excretion, and urine flow were measured in both kidneys at each renal perfusion pressure. Data were analyzed by unpaired t test and by homogeneity by slopes. RESULTS: The acute pressure natriuresis curve was blunted in pregnant rats versus virgins, and the renal nerves were not responsible. The blunted natriuretic response in pregnancy was due to loss of tubular epithelial responsiveness to increased blood pressure. CONCLUSION: The pressure natriuretic response is markedly blunted in pregnancy, permitting the cumulative plasma volume expansion to occur. Contrary to nongravid states, blunting of the acute pressure natriuresis curve in pregnancy is not associated with increased blood pressure because of the profound peripheral vasodilation. This suggests an alteration in the mechanism(s) normally linking blood pressure control to the acute pressure natriuresis relationship.

Animals↗
PubMed1998

Pressure-dependent neuroretinal rim loss in normal-pressure glaucoma.

PURPOSE: To evaluate whether, in normal-pressure glaucoma, the level of intraocular pressure is correlated with the degree of glaucomatous optic nerve damage. METHODS: Color stereo optic disk photographs of 98 eyes with the focal type of normal-pressure glaucoma, 17 eyes with the highly myopic type of normal-pressure glaucoma, and 36 eyes with the age-related atrophic type of primary open-angle glaucoma were morphometrically evaluated. RESULTS: In all three study groups, neuroretinal rim area declined significantly (P < .05) with increasing maximal intraocular pressure values. CONCLUSIONS: In different forms of open-angle glaucoma with normal intraocular pressure, eyes with relatively high intraocular pressure have more pronounced optic nerve damage than do eyes with relatively low intraocular pressure. This suggests a barotraumatic aspect in the pathogenesis of optic nerve damage in the normal-pressure glaucomas. It implies that therapeutically, an intraocular pressure in the low-normal range may less likely be associated with glaucoma damage than an intraocular pressure in the upper-normal range would be.

Aged↗
PubMed1996

High-frequency pressure-control ventilation with high positive end-expiratory pressure in children with acute respiratory distress syndrome.

OBJECTIVE: Animal models suggest that high-frequency ventilation with low tidal volumes and high positive end-expiratory pressure (PEEP) minimize secondary injury to the lung. We hypothesized that using a high-frequency pressure-control mode of ventilation with high PEEP in children with severe acute respiratory distress syndrome (ARDS) would be associated with improved survival. DESIGN: The study was a retrospective and prospective clinical study at a 24-bed tertiary care pediatric critical care unit. Fifty-three patients with severe ARDS were studied during a 37-month period, 30 prospectively and 23 retrospectively. Severe ARDS was defined as (1) rapid onset of severe bilateral infiltrates of noncardiac origin, (2) partial pressure of oxygen (arterial)/fraction of inspired oxygen less than 200 on PEEP of 6 cm H2O or more for 24 hours or longer, and (3) Murray disease severity score greater than 2.5. All patients meeting these criteria underwent ventilation in the pressure-control mode; the protocol for ventilation had the following general guidelines: (1) fraction of inspired oxygen limited to 0.5, (2) mean airway pressure titrated with PEEP to maintain arterial partial pressure of oxygen of 55 mm Hg or greater (7.3 kPa), (3) peak inspiratory pressure minimized to allow hypercapnia (arterial partial pressure of carbon dioxide, 45 to 60 mm Hg (6.0 to 8.0 kPa), and (4) ventilator rates of 40 to 120/min. Percutaneous thoracostomy and mediastinal tubes were placed for treatment of air leak. RESULTS: The survival rate was 89% (47/53) in children with severe ARDS. Nonsurvivors had significantly higher peak inspiratory pressures (75 vs 40 cm H2O, p = 0.0006), PEEP (23 vs 17 cm H2O, p = 0.0004), mean airway pressure (40 vs 28 cm H2O, p = 0.04), alveolar-arterial oxygen gradient (579 vs 540 mm Hg, p = 0.03), and oxygenation index (43 vs 19, p = 0.0008) than survivors. Air leak was present in 51% of patients; there was no difference in the incidence of air leak between survivors and nonsurvivors (p = 0.42). CONCLUSIONS: The high-frequency positive-pressure mode of ventilation was safe and was associated with an improved survival rate (89%) for children with severe ARDS. Limitation of both inspired oxygen and tidal volume, along with aggressive treatment of air leak, may have contributed to the improved survival rate.

Child↗