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At least 19 recordsLinked to original sources
PubMed1976

[Intracranial pressure--volumetric pressure and driving pressure].

In order to understand the pathogenesis of increased intracranial pressure, the concept of the driving pressure (DP) from the intracranial vascular system was proposed. The DP consists of the transmission of atrial pressure (ADP) and venous pressure (vp). It is well known that when the animals died, the intracranial pressure decreased to the atmospheric pressure. This means that the DP is important in maintaining the static pressure of the cerebrospinal fluid. The theoretical equation of the intracranial pressure was expressed as follows.ICP=ADP+VP (1) ADP is expressed as (2). ADP=eta (BP-VP) (2) The pressure transmission rat (eta) was calculated as the ratio of the CSF pressure to the systemic arterial blood pressure in the experimental and clinical cases. In the normal CSF pressure, eta was very small (2.0 X 10(-2)), while in the severe intracranial hypertension, eta approached to 1. The concept of the driving pressure was useful to analyze the static intracranial pressure and the pulse pressure.

Adult↗
PubMed1978

The effect of Swan-Ganz catheter height on the wedge pressure-left atrial pressure relationships in edema during positive-pressure ventilation.

We have studied the effect of the ventrical height of the pulmonary wedge catheter in the lung on the pulmonary wedge pressure-left atrial relationship during positive end-expiratory pressure ventilation in oleic acid-induced pulmonary edema. Pulmonary wedge catheters were placed above and below the left atrium in normal dogs and in dogs with oleic acid-induced edema. Wedge pressure and left atrial pressure were measured simultaneously during positive end-expiratory pressure ventilation (range, 0 to 30 cm H2O positive end-expiratory pressure). Pulmonary wedge catheters below the left atrium correctly recorded left atrial pressure and change in left atrial pressure at all positive end-expiratory pressures studied. Pulmonary wedge catheters above the atrium consistently recorded pressures higher than the normal left atrial pressure. They did not correctly respond to increases in left atrial pressure until it was increased to a value higher than the initial upper pulmonary wedge pressure. Pulmonary arterial catheters, when properly placed, should be reliable indicators of left atrial pressure during positive-pressure ventilation in normal and edematous lungs.

Animals↗
PubMed1992

Tissue interface pressure and estimated subcutaneous pressures of 11 different pressure-reducing support surfaces.

This pilot study examined the pressure-reducing properties of 11 different pressure-reducing devices as compared to a standard hospital mattress. Mean trochanteric and heel pressure readings were obtained on each surface from 13 healthy adult volunteers by using an electropneumatic pressure transducer (Gaymar, catalog # PSM1). Mean trochanteric pressures ranged from 37.2 mm Hg to 55.1 mm Hg on the pressure-reducing support surfaces as compared to 83.6 mm Hg on a standard hospital mattress. Mean heel pressure readings ranged from 28.1 mm Hg to 62.1 mm Hg on the pressure-reducing support surfaces as compared to 93.9 mm Hg on the standard hospital mattress. While pressure-reducing support surfaces were found to yield significantly lower mean pressure readings than the standard hospital mattress, none of them is capable of preventing tissue ischemia if the subcutaneous pressure is three to five times higher than the interface pressure.

Adult↗
PubMed1978

[The influence of changes in body position on intraocular pressure, episcleral venous pressure, and blood pressure (author's transl)].

The intraocular pressure, the ophthalmic artery pressure, and the episcleral venous pressure increased after changes from sitting to recumbent body position, whereas the subclavian artery pressure remained unchanged or decreased slightly. Changing from recumbent to sitting position was followed by a decrease in IOP, ophthalmic pressure, and subclavian artery pressure. Comparing the last measurement in the first position to the first value after change, it was found that the IOP alters by about 20%, the ophthalmic artery pressure by 15%, and the episcleral venous pressure by 50%. In all series a decrease in subclavian artery pressure was observed during the first 15 min. The mean pressure in the ophthalmic artery diminished in the series that changed from sitting to recumbent position, whereas it increased in the other series during the first 15 min. The episcleral venous pressure increased more than the corresponding IOP after changing to the recumbent position.

Blood Pressure↗
PubMed1990

Effect of gammahydroxybutyrate on intracranial pressure, mean systemic arterial pressure and cerebral perfusion pressure in experimentally induced brain oedema of the rat.

The effect of gammahydroxybutyrate (GHB) on ICP, systemic arterial pressure and cerebral perfusion pressure in the experimentally induced brain oedema of the rat was examined. 400 mg/kg GHB reduced significantly ICP (11.74 +/- 1.20 mm Hg; control: 16.20 +/- 8.89 mm Hg; p less than 0.01) while increasing mean systemic arterial pressure (109.89 +/- 6.35 mm Hg; control: 89.65 +/- 4.22 mm Hg; p less than 0.05) and cerebral perfusion pressure (98.11 +/- 6.79 mm Hg; control: 73.84 +/- 5.25 mm Hg; p less than 0.02). In the dose-effect curve 200 mg/kg GHB show an increase in mean systemic arterial pressure from 89.60 +/- 9.35 mm Hg to 97.60 +/- 3.48 mm Hg (p less than 0.02) and 400 mg/kg GHB to 108.00 +/- 5.20 mm Hg (p less than 0.001) mean systemic arterial pressure. Thus, the decrease in intracranial pressure is not due to a reduction in the mean systemic arterial pressure, but GHB does reduce the ICP while increasing mean systemic arterial pressure and cerebral perfusion pressure. GHB may be a useful adjunct to neurosurgical therapy in controlling elevated ICP.

Animals↗
PubMed1992

Blood pressure reactivity does not correlate with baseline blood pressure or blood pressure change over time in preschool children.

Few studies have examined the relation of blood pressure reactivity to subsequent change in blood pressure of preschool children. The authors investigated relations between measurement-induced reactivity, exercise reactivity, and change in blood pressure over 16 months among 140 preschool children (46-67 months of age at baseline, 50.7% female, 92.9% Hispanic). Within-session measurement-induced reactivity was defined as the change in blood pressure between the first and the mean of the fourth and fifth readings obtained at each of 11 sessions. Between-session measurement-induced reactivity was defined as the change between mean blood pressure at session 1 and the mean of sessions 2 and 3. Both indices of measurement reactivity displayed poor reproducibility. Exercise reactivity was measured using a treadmill on two occasions and was moderately reproducible. There was no association between measurement and exercise reactivity. The change in systolic blood pressure over time was not associated with any measure of reactivity. The mean diastolic blood pressure did not change over the study period. Neither blood pressure reactivity to measurement nor blood pressure reactivity to exercise appeared to be a useful predictor of change in blood pressure in preschool children during a 16-month period.

Blood Pressure↗
PubMed1991

Pressure-time product during continuous positive airway pressure, pressure support ventilation, and T-piece during weaning from mechanical ventilation.

The objective of this study was to compare the effects of continuous positive airway pressure (CPAP), pressure support ventilation (PS), and T-piece on the pressure-time product (PTP) during weaning from mechanical ventilation. The PTP is an estimate of the metabolic work or oxygen consumption of the respiratory muscles. We studied 10 intubated patients recovering from acute respiratory failure of various etiologies. A modified continuous flow (flow-by) CPAP of 0 and 5 cm H2O (CPAP-0 and CPAP-5, respectively), PS of 5 cm H2O (PS-5), and T-piece were applied in random order for 30 min each. In the last 5 min of the 30-min periods, we measured the esophageal pressure and transdiaphragmatic pressure-time products--PTP(es) and PTP(di), cm H2O.s/min, respectively-multiplied by respiratory frequency. Breathing pattern, total lung resistance (RL), quasi-static lung compliance (CL), intrinsic positive end-expiratory pressure (PEEPi), end-expiratory transpulmonary pressure (Ptpexp), arterial blood gases, blood pressure, and heart rate were also measured. In comparison to T-piece, CPAP-5 decreased PTP(es) 40% (p less than 0.01) and PTP(di) 43% (p less than 0.02), whereas PS-5 decreased PTP(es) 34% (p less than 0.01) and PTP(di) 38% (p less than 0.05). The decrease in PTP(es) with CPAP-5 was associated with a significant reduction in RL, and to a less extent in PEEPi relative to airway pressure. The contribution of the decrease in PEEPi to the reduction in PTP(es) amounted to 36%. With PS-5, respiratory system mechanics and PEEPi were not significantly different compared with T-piece. With CPAP-0, PTP tended to be lower than with T-piece.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1976

[Pulmonary artery pressure and left ventricular late diastolic pressure in rest and during dynamic load. Comparative studies on pressure transmission in the pulmonary circulation during simultaneous determination].

Left ventricular enddiastolic pressure (LVEDP), mean pulmonary artery pressure (PAPM) and enddiastolic pulmonary artery pressure (PADP) were simultaneously recorded in 19 subjects with normal left ventricular (LV) function, and in 109 patients with LV-dysfunction, 83 of whom were also studied during exercise. Patients with valvular heart disease or atrial fibrillation were excluded from this study. LVEDP and mean pulmonary capillary wedge (PCW) pressure were simultaneously recorded in 81 patients at rest, andin 16 patients also during exercise; the LV diastolic pressure prior to atrial contraction (LVPpreA) could accurately be identified in 45 patients at rest and in 23 patients with exercise. In contrast to the widely accepted opinion of others, the PADP (mean 8.2 +/- 2.2 mm Hg at rest and 12.3 +/- 3.4 mm Hg with exercise) showed a close approximation of LVEDP (10.0 +/- mm Hg at rest and 16.2 +/- 3.5 mm Hg with exercise) only in normal subjects at rest (p less than 0.05 and p less than 0.01 respectively). In patients with LV dysfunction there was no significant difference between PADP (11.7 +/- 4.5 mm Hg and 23.0 +/- 8.9 mm Hg), PCW (11.6 +/- 5.1 mm Hg and 24.1 +/- 11.9 mm Hg) and LVPpreA (12.5 +/- 5.5 and 21.5 +/- 7.7 mm Hg) at rest and during exercise. LVEDP could be estimated with sufficient accuracy only from the PAPM (18.9 +/- 6.5 and 35.7 +/- 10.8 mm Hg). The increase in LVEDP (14.7 +/- 7.7 mm Hg) with exercise was not significantly different from the increase in PAPM (16.8 +/- 7.1 mm Hg). There were highly significant correlations (p less than 0.001) between LVEDP and PADP (r = 0.85) as well as PAPM (r = 0.86) at rest and during exercise with the regressionline being closest to the line of identity for LVEDP and PAPM. The pressure gradient between LVEDP and PADP (LVEDP - PADP = 6.3 mm Hg with exercise) equaled the pressure increase in LV by atrial contraction (LVEDP - LVPpreA = 6.3 and 13.3 mm Hg). The pressure difference between PADP or PAPM and LVEDP remained constant despite marked variation of other hemodynamic parameters, e.g. stroke volume index (SVI), heart rate (HR) and cardiac index(CI). These data suggest that an elevated LVEDP is caused mainly by an augmented atrial contraction in patients with LV dysfunction at rest and with exercise. This mechanism precludes an enddiastolic pressure equilibrium between pulmonary artery and left ventricel. PAPM allows the best estimation of LVEDP independent from other hemodynamic variables.

Adult↗
PubMed1990

[A basic study on pressure distribution of supporting structures under complete denture. 1. Application of pressure dispersion analyzing system by using impedance grid sensor to measure the pressure of supporting structures under complete denture].

In order to measure the pressure distribution on supporting structures under complete denture, we used impedance grid pressure sensor and examined its accuracy and availability. The results were as follows: 1. The sensitivity of this sensor was high when the distance between electrodes was short. 2. This sensor showed large change in output voltage and high sensitivity in the case of soft elastic materials. 3. This sensor showed the high linearlity between output voltage and applied load. 4. This sensor showed hysteresis loop under cycle load. 5. Base line of this sensor that has the urethane rubber as elastic material was changed when the load was applied intermittently. We measured the pressure distribution over supporting bones under upper complete denture by using simulator of maxillary edentulous with this impedance grid pressure sensor. We could observe the pressure distribution and pressure region in detail and visually when the load was applied to the both occlusal tables evenly.

Alveolar Process↗
PubMed1991

Continuous positive pressure breathing without and with inspiratory pressure support in acute respiratory failure when mean airway pressure is constant.

OBJECTIVE: Mean airway pressure (Pawm) may be a major factor for PaO2, functional residual capacity, and cardiac output in acute respiratory failure (ARF). To clarify effects of inspiratory pressure support (IPS) as a ventilatory mode in ARF, we studied patients in ARF either using IPS or continuous positive pressure breathing (CPAP) at the same level of Pawm, measuring respiratory and circulatory parameters. METHODS: After consent, 10 patients in ARF of moderate severity (PaO2:FiO2 205 +/- 108 at positive end expiratory pressure (PEEP) 8.7 +/- 3.1 cmH2O; mean +/- SD) were investigated. Measurements were on day 7.4 +/- 8.4 after onset of ARF. IPS was 13.5 +/- 3.9 cmH2O above PEEP. To result in constant Pawm, PEEP was reduced for IPS (Pawm IPS 11.1 +/- 3.6 vs. Pawm CPAP 9.9 +/- 3.3 cmH2O, ns; PEEP IPS 8.7 +/- 3.1 vs. PEEP CPAP 10.6 +/- 4.3 cmH2O, p = 0.04). Inspired concentration of oxygen (FiO2) and the ventilator (Siemens 900 C) were not changed for the individual patient. RESULTS: For IPS, tidal volume (VT) increased by +31% and respiratory frequency (RF) decreased by -19% (VT IPS 608 +/- 179 vs. VT CPAP 465 +/- 141 ml, p = 0.01; RF IPS 21.6 +/- 7.6 vs. RF CPAP 26.7 +/- 8.3 breaths per minute, p = 0.02). Also, PaCO2 showed a tendency to be lower for IPS, not reaching significance (PaCO2 IPS 44.3 +/- 5 vs. PaCO2 CPAP 47.4 +/- 4.9 mmHg, p = 0.1). All other parameters were unchanged (expiratory minute volume, PaO2, pH, intravascular pressures, cardiac index, stroke volume index (n = 6), systemic and pulmonary vascular resistances, venous admixture, deadspace (n = 3), oxygen consumption and oxygen delivery). WE CONCLUDE: When Pawm remained constant, IPS added to CPAP improved VT and RF without improving oxygenation or deteriorating circulation in patients with ARF of moderate severity. IPS mainly supports the ability to breathe spontaneously in ARF.

Acute Disease↗
PubMed1978

Hemodynamic and respiratory response to varying gradients between end-expiratory pressure and end-inspiratory pressure in patients breathing on continuous positive airway pressure.

Nine patients on intermittent mandatory ventilation (IMV) and continuous positive airway pressure (CPAP) were allowed to breathe spontaneously at varying end expiratory pressure-end inspiratory pressure (EEP-EIP) gradients up to 10 cm H2O. There was no change in the mean cardiac output and oxygen delivery despite a lowered mean airway pressure (MAWP) when the gradient was increased. Three patients were uncomfortable at the higher gradients and another manifested evidence of fatigue of the muscles of respiration by raising her arterial PCO2 (PaCO2) and intrapulmonary shunt (Qs/Qt). In view of the difficulty experienced by some patients and lack of improvement in cardiac outputs (CO) during spontaneous inspiration when the EEP-EIP gradient is raised from zero to 5 and 10 cm H2O, it is recommended that the variation in airway pressure during spontaneous breaths while a patient is on CPAP be minimized.

Hemodynamics↗
PubMed1992

[Extending informative value of intracranial pressure measurement by cerebral pressure amplitudes (Pa)--analysis of average intracranial pressure (Pm)].

One aim of the intracranial pressure measurement is observing constantly patients with intracranial space-occupying factors and therefore to act diagnosticly and therapeutically correct at the right time. Through the continual registration of the intracranial pressure amplitude in relation to the medium intracranial pressure it is earlier possible to forecast intracranial pressure rise and to deal with this than with just the simple measurements of medium intracranial pressure. With 40 neurosurgical patients such examinations were undertaken after implantation of a ventricle catheter. The value of this method was proven during the continual observation of the patient.

Brain Injuries↗
PubMed1991

Intracranial pressure monitoring using a programmable pressure valve and a telemetric intracranial pressure sensor in a case of slit ventricle syndrome after multiple shunt revisions.

A case of hydrocephalus showing slit ventricle syndrome after multiple shunt revisions was treated with a programmable pressure valve, and intracranial pressure was monitored with a telemetric sensor. High pressure setting produced positive and normal values of intracranial pressure in this patient. We report our experiences.

Cerebrospinal Fluid Shunts↗
PubMed1990

Minimum airway pressure weaning. Weaning from mechanical ventilation at 50 breaths/minute by reduction of inflation pressure using a pressure generator.

Ten patients, whose lungs were ventilated initially with intermittent positive pressure ventilation at conventional rates after myocardial revascularisation or cardiac valvular surgery, were weaned using a valveless high frequency jet ventilator at a constant rate of 50 breaths/minute. The withdrawal of ventilation was achieved, when clinical criteria permitted, by reduction of the tidal volume preset on the jet ventilator in successive stages; this was effected by stepwise decreases in the jet driving pressure. This new mode of weaning at a constant rate of 50 breaths/minute is associated with minimum peak airway pressures. Synchronisation of the patient's breathing with the valveless ventilator is not required and weaning is tolerated well by the patient. Arterial oxygen tension and saturation were maintained throughout weaning and did not decline after extubation of the trachea.

Adult↗
PubMed1992

Effect of torasemide on intracranial pressure, mean systemic arterial pressure and cerebral perfusion pressure in experimental brain edema of the rat.

The study was performed to establish whether a lipophilic loop diuretic, torasemide could modify intracranial pressure and cytotoxic brain edema. Brain edema was induced by water intoxication in nephrectomized rats. Following intravenous injection of 100 mg torasemide/kg body weight at 50, 60, 70, 90 and 120 min, a significant decrease of intracranial pressure was observed.

Animals↗