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PubMedDate not supplied

Stress-induced alterations of blood pressure and 24 h ambulatory blood pressure in adolescents.

OBJECTIVE: To examine the extent to which ambulatory blood pressure was predicted by blood pressure levels exhibited during talking segments of a laboratory protocol and by resting blood pressures in male and female adolescents from three ethnic groups: African, European and Hispanic Americans. DESIGN: This was a laboratory-field study incorporating an experimental study of reactivity of blood pressure during a laboratory protocol and an observational study of 24h ambulatory blood pressure (ABP) monitoring. METHODS: Resting blood pressure, reactivity of blood pressure, 24h ABP, and activity, height, and maturation of a multi-ethnic sample of 373 male and female adolescents aged 11-16 years were measured. A mixed-effects model for repeated measures was the statistical approach, with systolic and diastolic blood pressures as separate, dependent variables. RESULTS: Percentiles of ABP by sex, ethnic group, and height are presented. High and mixed blood pressure reactors in the laboratory had higher levels of 24h ABP and higher levels of blood pressure load during the daytime. African Americans had higher ABP than did European and Hispanic Americans. CONCLUSIONS: Blood pressure measured during laboratory tasks that require talking might be useful as a screening device to identify adolescents with high blood pressures. Further study will be necessary in order to quantify the sensitivity of the laboratory protocol as an indicator of high blood pressure compared with casual measurement of blood pressures. If laboratory patterns of blood pressure could be used to predict which individuals have high levels of blood pressure during the course of daily activities, the laboratory protocol would be a useful screening tool, identifying high-risk individuals.

Adolescent↗
PubMed2006

Intrathoracic pressure regulation improves vital organ perfusion pressures in normovolemic and hypovolemic pigs.

BACKGROUND: The intrathoracic pressure regulator (ITPR) was created to improve hemodynamics by generating continuous negative airway pressure between positive pressure ventilations to enhance cardiac preload in apnoeic animals. In normovolemic and hypovolemic pigs, we tested the hypothesis that continuous negative intrathoracic pressure set at -5 or -10mmHg, interrupted only for intermittent positive pressure ventilations, would decrease intracranial (ICP) and right atrial (RAP) pressure, and increase mean arterial pressure (MAP). METHODS: Twelve pigs were anesthetized with propofol and ventilated with a bag. The ITPR was used to vary baseline endotracheal pressures (ETPs) for 5min periods in the following sequence: 0, -5, 0, -10, 0mmHg under normovolemic conditions. Six pigs were bled 50% (32.5+/-mL/kg) of their estimated blood volume and the airway pressure sequence was repeated. Six other pigs were bled 35% (22.75+/-mL/kg) of their estimated blood volume and the same airway pressure sequence was repeated. Intracranial, aortic, right atrial pressures, arterial blood gases, end tidal CO(2) (ETCO(2)), were measured. ANOVA was used for statistical analysis. Linear regression analysis was performed for ETP and ICP. RESULTS: Mean arterial and vital organ perfusion pressures were significantly improved and RA pressure significantly decreased with the use of the ITPR; the effect was greater with the more negative ETPs and lower circulating blood volume. The change of ICP was linearly related to the ETP and blood loss: DeltaICP=[1.22-0.84(1-%blood loss/100)]xETP, r(2)=0.88 (in mmHg), p<0.001. There were no adverse device effects and there was a significant increase of ETCO(2) with the use of ITPR. CONCLUSION: The ITPR decreased RAP and ICP significantly and improved mean arterial and cerebral and coronary perfusion pressures without affecting acid base balance severely. The decrease in ICP was directly proportional to the reduction in intrathoracic pressure. The effects were more pronounced in severe hypovolemic and hypotensive states with more negative ETP pressure.

Animals↗
PubMed1985

Relative urethral leakage pressure versus maximum urethral closure pressure. The reliability of the measurement of urethral competence with the new tube-foil sleeve catheter in patients.

In 78 female patients the urethral leakage pressure, defined as the intravesical pressure at which leakage starts from the urethral orifice, was estimated with the tube-foil sleeve catheter. In accordance with the definition of maximum urethral closure pressure, the relative urethral leakage pressure was defined as urethral leakage pressure minus intravesical resting pressure. In the same patients urethral closure pressure was also measured by urethral pressure profilometry with a flexible micro pressure-sensor catheter. On the average the ratio of relative urethral leakage pressure/urethral closure pressure was about 0.5. Relative urethral leakage pressure and urethral closure pressure were higher than the maximum detrusor pressure increases during detrusor instabilities in 21 continent patients with motor urge. The relative urethral leakage pressure correlated better with the detrusor pressure elevations at which fluid loss from the urethral orifice started in 24 motor urge incontinent patients than urethral closure pressure did.

Female↗
PubMed1997

Influence of airway pressure on minimum occlusive endotracheal tube cuff pressure.

OBJECTIVE: To examine the in vivo relationship between peak inflation pressure and the minimum occlusive pressure of a "high-volume, low-pressure" endotracheal tube cuff that may in some circumstances promote tracheal ischemic complications. DESIGN: Prospective, clinical study. SETTING: Surgical suite in a university hospital. PATIENTS: Fifteen patients undergoing mechanical ventilation and general anesthesia for surgery. INTERVENTIONS: After the regularly assigned anesthesia personnel established adequate general anesthesia, the investigator deflated and then reinflated the endotracheal tube cuff until tracheal seal was reestablished by auscultation. Peak inflation pressure and minimum occlusive pressure were determined using fluid-filled transducers to simultaneously record airway pressure just proximal to the endotracheal tube and cuff pressure via the pilot tube. MEASUREMENTS AND MAIN RESULTS: Peak inflation pressure ranged from 12.1 to 43.7 mm Hg, and was associated with a minimum occlusive pressure of 2.2 to 39.7 mm Hg. Minimum occlusive pressure increased linearly over the range of measured peak inflation pressure values (r2 = .85, p < .001). CONCLUSIONS: Knowledge of the linear relationship between peak inflation pressure and minimum occlusive pressure can help the clinician identify patients who may be at risk for cuff-induced tracheal ischemic complications, such as tracheoesophageal fistula and tracheal stenosis. In our series, a cuff pressure of 25 mm Hg corresponded to a peak inflation pressure of 35.3 mm Hg (48 cm H2O). Patients with higher peak inflation pressures may be at risk for ischemic tracheal injury, despite proper cuff inflation techniques.

Adult↗
PubMed2003

Tympanometry versus direct middle ear pressure measurement in an artificial model: is tympanometry an accurate method to measure middle ear pressure?

HYPOTHESIS: Indirect tympanometric pressure measurements of the middle ear (ME) do not correspond to direct pressure measurements. BACKGROUND: Tympanometry is an accepted method for estimating ME pressures. These pressure values are different, however, when measurements are made directly. MATERIALS AND METHODS: Negative pressures were induced by volume changes in an artificial ME model with various "mastoid" volumes. Both tympanometric and direct pressure measurements were obtained simultaneously. RESULTS: A substantial difference was demonstrated between tympanometric and direct pressure measurements. There was a linear correlation between tympanometry and direct pressures between -46.8 and -93.6 mmH2O, with a tympanometric overestimation of 40% to 20%, respectively. The smaller the "mastoid" volume, the greater the overestimation. The correlation was not linear for direct pressures between zero and -46.8 mmH2O. Tympanometric overestimation was greatest (i.e., 4-14-times the actual pressure) in the pressure range between zero and -12 mmH2O. CONCLUSIONS: Tympanometry does not yield precise ME pressure values. In a model with a larger "mastoid" and an actual pressure range of -46.8 to -93.6 mmH2O tympanometric readings are somewhat less unreliable (error of 40%-20%). However, tympanometry is in error of more than 400% in a model with a small mastoid in which the actual ME pressure is only slightly negative (i.e., range between -3.9 and -46.8 mmH2O). Therefore, this study implies that tympanometry has little use for measuring ME pressure especially in chronic ears or their sequelae that are usually characterized by having small negative pressures and small mastoids.

Acoustic Impedance Tests↗
PubMed1996

Human gallbladder pressure and volume: validation of a new direct method for measurements of gallbladder pressure in patients with acute cholecystitis.

Increased gallbladder (GB) pressure is probably a part of the pathogenesis of acute cholecystitis, and measurements of GB pressure might therefore be of interest. The aim of this study was to validate a microtip pressure transducer for intraluminal GB pressure measurements. In vitro precision and accuracy was within 0.2 mmHg, (SD) and 0.6 +/- 0.1 mmHg (mean +/- SD), respectively. Pressure rise rate was 24.8 +/- 5.5 mmHg s-1. Zero drift was in the range 0.3 +/- 0.4 to 0.8 +/- 0.9 mmHg (mean +/- SD). GB pressure was investigated in 16 patients with acute cholecystitis treated with percutaneous ultrasonically guided cholecystostomy. Basal intraluminal GB pressure was 8.9 mmHg (2.1-12.2 mmHg; n = 9, open cystic duct) and 1.8 and 5.8 mmHg (n = 2, closed cystic duct). There was no significant difference between two different measurements in the same patients (n = 5). The pressure was significantly influenced by respiration (n = 8) and the pressure seems to be higher in the sitting position than in the supine position (n = 5). Cystic duct opening pressure was 10.4, 11.2 and 16.8 mmHg (n = 3). Pressure-volume responses showed that the GB up to a certain volume could accommodate increases in intraluminal volume with only slight changes in intraluminal pressure (n = 4). Except for the zero drift, this piece of equipment seemed to fulfil the requirements of being able to measure pressure in the GB. In vivo measurements showed a good clinical reproducibility of the method, and also that respiration and patient posture influenced the pressure measurements. Further, a GB pressure-volume relationship was demonstrated, and the possibility of a cystic duct opening pressure was described.

Acute Disease↗