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PubMed1981

[Gas-diffusion induced pressure kinetics in low pressure cuffs. Continuous pressure measurement in vivo and in vitro (author's transl)].

The main cause for the rise in cuff-pressure during anesthesia is the diffusion of nitrous oxide into the tube cuff. Gas-diffusion induced pressure changes in low pressure-high volume cuffs are registered continuously. Exposure of an air-filled cuff into an anaesthetic gas atmosphere in vitro shows, that there is an increase in cuff-pressure up to 150 mm Hg within 8 hours. This pressure-plateau remains for several hours. In intubated patients cuff-pressure increases even more. During anesthesia lasting 4--5 hours we recorded pressures up to 150 mm Hg, too. To prevent these high pressures we recommend the reducing of cuff-volume within defined times of anesthesia or, alternatively, the use of the anesthetic gas mixture as cuff inflating gas.

Anesthesia, Inhalation↗
PubMed1993

[Shunt indication of CSF circulatory disturbance with cerebral atrophy (atypical normal pressure hydrocephalus): evaluation of serum alpha 1-antichymotrypsin and pressure wave on epidural pressure monitoring].

PURPOSE: The purpose of this study was to evaluate serum alpha 1-antichymotrypsin (alpha 1-ACT) and pressure wave on continual epidural pressure (EDP) monitoring as the indices for shunt operations in CSF circulatory disturbance associated with cerebral atrophy (atypical normal pressure hydrocephalus: ANPH). METHOD: The subjects adopted were 10 patients (aged 48-79, averaging 64.9, male: female = 8.2). V-P shunt was performed on all the cases, and venous blood was collected from the internal jugular vein before and after the operation to measure serum alpha 1-ACT value (nephelometry method, SRL Co.). Continual measurement of EDP was made preoperatively (Geltec Co.). A comparative assessment was made regarding the preoperative alpha 1-ACT value and appearance or not of pressure wave at EDP in the group whose symptom was improved by shunt (effective group: E) and the other group (non-effective group: NE). RESULTS: 1. The cases were 6 in group E and 4 in group NE. 2. The mean values of the preoperative alpha 1-ACT were 43.47 +/- 8.08mg/dl in group E and 63.68 +/- 5.48mg/dl in group NE. The former exhibited evidently low values, and all the cases whose values were less than 55mg/dl belonged to group E (p < 0.001). 3) Pressure wave (A or B wave) at EDP were observed in 5 cases, all in group E. CONCLUSION: 1. Serum alpha 1-ACT value can be regarded as an index for shunt indication for ANPH, and the value was lower in group E than group NE. The value at the boundary between effectiveness and ineffectiveness was 55 mg/dl. 2. Appearance of pressure wave at measurement of EDP was observed in all of group E. 3. Shunt operation should be taken into consideration for ANPH patients whose preoperative serum alpha 1-ACT value is low (less than 55mg/dl) and in whom pressure wave emerges at continual measurement of EDP, even though their cerebral atrophy is found to be severe by CT.

Aged↗
PubMed1995

Effect of airway pressure on inferior vena cava pressure as a measure of central venous pressure in children.

We evaluated the effect of elevated airway pressure on the validity of intravascular pressure obtained in the distal inferior vena cava (IVC) as a measure of central venous pressure (CVP) in a group of children receiving mechanical ventilation. The IVC pressure correlated well with CVP in the patients without abdominal distention, but the disparity was wider in those with abdominal distention. Elevated mean airway pressure or positive end-expiratory pressure had no effect on the relationship of IVC to CVP.

Adolescent↗
PubMed1989

Proximal mean airway pressure: a good estimator of mean alveolar pressure during continuous positive-pressure breathing.

Although airway and alveolar pressures are not instantly equal during positive-pressure ventilation, proximal mean airway pressure (Paw) is the simplest available indirect gauge of mean alveolar pressure (Palv). To ascertain the relation of Paw to Palv and the limits of agreement between the two measures, real-time curves of proximal airway pressure (at the hub of the endotracheal tube) and alveolar pressure were generated by repeated airway occlusion at numerous PEEP levels in four groups of ventilated lambs or piglets: normal controls, oleic acid-injured and serotonin stimulated lambs, and preparations with mechanically induced air trapping. From these curves, Paw and Palv were determined. In all groups, Paw proved to be a precise estimator of Palv during volume-regulated, time-cycled, continuous positive-pressure breathing.

Airway Resistance↗
PubMed1988

High inflation pressure pulmonary edema. Respective effects of high airway pressure, high tidal volume, and positive end-expiratory pressure.

The respective roles of high pressure and high tidal volume to promote high airway pressure pulmonary edema are unclear. Positive end-expiratory pressure (PEEP) was shown to reduce lung water content in this type of edema, but its possible effects on cellular lesions were not documented. We compared the consequences of normal tidal volume ventilation in mechanically ventilated rats at a high airway pressure (HiP-LoV) with those of high tidal volume ventilation at a high (HiP-HiV) or low (LoP-HiV) airway pressure and the effects of PEEP (10 cm H2O) on both edema and lung ultrastructure. Pulmonary edema was assessed by extravascular lung water content and microvascular permeability by the drug lung weight and the distribution space of 125I-labeled albumin. HiP-LoV rat lungs were not different from those of controls (7 cm H2O peak pressure ventilation). By contrast, the lungs from the groups submitted to high volume ventilation had significant permeability type edema. This edema was more pronounced in LoP-HiV rats. It was markedly reduced by PEEP, which, in addition, preserved the normal ultrastructural aspect of the alveolar epithelium. This was in striking contrast to the diffuse alveolar damage usually encountered in this type of edema. To our knowledge, this constitutes the first example of a protective effect of PEEP during permeability edema.

Animals↗
PubMed2000

Effect of hyperventilation on brain tissue oxygen pressure, carbon dioxide pressure, pH value and intracranial pressure during intracranial hypertension in pigs.

OBJECTIVE: To study the effect of hyperventilat ion on brain tissue oxygen pressure (P(ti)O(2)), brain tissue carbon dio xide pressure (P(ti)O(2)), pH value and intracranial pressure (ICP) dur ing intracranial hypertension in pigs. METHODS: Autologous arterial blood (5.5 mlplus minus0.5 ml) was injected into the left frontal lobe by micropump to establish the model of intr acerebral hematoma in pigs. After blood injection, the animals were hyperventila ted for 15 minutes to decrease the pressure of carbon dioxide in arterial blood (P(a)CO(2)) to 27.35 mm Hgplus minus11.97 mm Hg (1 mm Hg=0.133 kPa). The mean arterial pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), P(ti)O(2), (P(ti)CO(2)), pH value and [HCO(3)(-)] were continuously monitored and the blood gas was analyzed. RESULTS: After hyperventilation, the ICP significantly decr eased (P<0.01), the CPP significantly increased (P<0.05), while the P(ti)O(2) greatly decreased to t he ischemic level (8.20 mm Hgplus minus2.50 mm Hg) (P<0.01), the P(ti)CO(2) decreased (P<0.01) and the pH value increased (P<0.01). At the same time, bl ood gas analysis showed that the P(a)CO(2) greatly decreased and the pH valu e increased. CONCLUSIONS: Hyperventilation can decrease the ICP and the P(ti)O(2) significantly. Therefore, hyperventilation should be avoided earl y after brain injury. The P(ti)O(2) monitoring will be helpful for detec ting cerebral ischemia early.

Journal Article↗
PubMed2006

[Interface pressure measurement in the treatment of pressure sores. Comparison with subcutaneous pressure values measured in healthy volunteers].

BACKGROUND: Pressure relief is an important factor to determine the quality of anti-decubitus devices. Many studies have been carried out to measure the interface pressure, but because the results differed markedly, we made a study to assess the measurement devices. METHODS: The systems FSA, a device for internal use in the Lück company, the X-Sensor and an invasive subcutaneous pressure measurement over the os-sacrum (COACH: piezoelectric probe, MIPM) were tested on 20 healthy volunteers (average age 27 years, average BMI 21.8). RESULTS: The values of interface measurement showed obvious deviations from subcutaneous pressure in two cases (FSA +1.8%, Lück -33%, X-Sensor +65%) and some results showed extreme variations (FSA +18 mmHg, Lück -21 mmHg, X-Sensor +27 mmHg). CONCLUSIONS: The interface pressure measurement (with a few volunteers) is not suitable for a correct assessment of anti-decubitus devices. Furthermore, the use of this method is not necessary to monitor pressure relief in intensive care patients. These systems can, however be useful in the training of nursing staff.

Adult↗
PubMed2002

[Peculiarities of blood pressure rhythms and blood pressure variability in adolescents with hypertension (in accordance with twenty-four monitoring of blood pressure)].

Registration of 24-hour blood pressure in adolescents with and without hypertension revealed active participation of sympathetic nervous system in genesis of juvenile hypertension. Hypertension in adolescents was mainly systolic, blood pressure elevation as a rule was accompanied by accelerated heart rate and increased pulse pressure. Episodes of blood pressure elevations occurred mostly during day time. Desynchronization of 24-hour rhythms due to excessive nocturnal blood pressure lowering was found to be typical for this age group. More than two thirds of adolescents with episodes of blood pressure elevation had also 'white coat hypertension'.

Adolescent↗
PubMedDate not supplied

[Mean airway pressure during pressure-controlled ventilation with static vs. dynamic positive end-expiratory pressure].

BACKGROUND: Positive end-expiratory pressure increases mean airway pressure (Paw) in patients with mechanical ventilation. We undertook this study to compare mean airway pressure (Paw) generated with static PEEP (sPEEP) vs. dynamic PEEP (dPEEP) at the same level of total PEEP (tPEEP) in the same patient with pressure-controlled mechanical ventilation (PC). METHODS: We conducted a prospective clinical trial at the Intensive Care Unit of a university-affiliated hospital. Consecutive patients in PC with SaO2>90%; FiO2<50%; sPEEP of 4 cm H2O and inspiration-expiration ratio (I:E ratio) 1:2 were included in the study. After a basal period of time of 15 min, Paw was registered (phase one of the study protocol). In phase 2 with the ventilator settings constant, only the I:E ratio was switched to 2:1 to generate dPEEP, and after 15 min Paw and total PEEP (tPEEP) were registered (tPEEP=sPEEP+dPEEP). In phase 3, the I:E ratio was switched back to 1:2 substituting the dPEEP generated in the second phase of the study by sPEEP to maintain the same level of tPEEP of phase 2. After 15 min, Paw was again registered. Friedman and Wilcoxon's test were used, p value<0.05 was considered statistically significant. RESULTS: Thirty eight patients were admitted to the study protocol, tPEEP was 4, 8 and 8 cm H2O and median of the Paw 8.7, 13.8, and 11.4 cm H2O, respectively, with a p value<0.05 in the first, second and third phases of the study. CONCLUSIONS: During pressure control ventilation, mean airway pressure is affected by the level of total PEEP and its composition. Paw is higher when dynamic PEEP participates in the composition of total PEEP.

Adolescent↗
PubMed1996

Modification of the single unpaired sulfhydryl group of beta-lactoglobulin under high pressure and the role of intermolecular S-S exchange in the pressure denaturation [single SH of beta-lactoglobulin and pressure denaturation].

Chemical modification reactions of the unpaired sulfhydryl group of beta-lactoglobulin (LG) under high pressure and the role of this group in the pressure-induced denaturation were investigated. When LG was incubated at 400 MPa (pH 6.8) for 1 h, dimerization through intermolecular reaction of SH was observed. The generation of the covalently linked dimers were prevented by the presence of N-ethylmaleimide (NEM), an agent for SH-specific modification. The reactivity of the SH group of LG, which is buried inside in its native state, was increased by high pressure, as a result of its exposure to the protein surface accompanied by the pressure denaturation. The effect of NEM was also observed in the fluorescence change caused by high pressure, in both the intrinsic fluorescence of LG and the retinol fluorescence of the LG-retinol complex. The control showed an irreversible change at neutral pH, but it became mostly reversible in the presence of NEM. Compatible results were obtained by CD spectroscopy. Inter- and intramolecular reactions of the SH group are suggested to be main causes for the pressure-induced irreversible denaturation of LG.

Circular Dichroism↗
PubMed1989

Measuring pressure under burns pressure garments using the Oxford Pressure Monitor.

Pressure garments are used extensively in the treatment of hypertrophic scarring following burn injuries. The Oxford Pressure Monitor was used to measure garment-scar interface pressure (mmHg) using a number of fabric types over various body parts. The results indicate a wide range of pressure values between different garments and body parts with the greatest pressures found over the dorsum of hands and feet. The problems of achieving 'optimal pressure' over hypertrophic scarring are discussed with emphasis on the need for more accurate measuring equipment.

Burns↗
PubMed1980

Inhibition of fast anterograde axoplasmic transport by a pressure barrier. The effect of pressure gradient and maximal pressure.

Fast anterograde axoplasmic transport was studied in the motor fibres of the vagus nerve of rabbits in vitro at 22 degrees C with a pressure barrier applied to a small section of the nerve. The barrier was characterized by the maximal pressure and the gradients on each side of the maximum. The range tested was 16 to 45 mmHg maximal pressure and 30 to 140 mmHg/mm length of nerve for the pressure gradients. It was found that in the ranges tested the maximal pressure was of major importance for the inhibition of transport, the pressure gradient being of little significance. The results indicate that at least one part of fast anterograde axoplasmic transport occurs within collapsible canalicular structures.

Animals↗
PubMed2000

Systolic and diastolic blood pressure, pulse pressure, and mean arterial pressure as predictors of cardiovascular disease risk in Men.

We compared systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), and mean arterial pressure (MAP) in predicting the risk of cardiovascular disease (CVD), stratifying results at age 60 years, when DBP decreases while SBP continues to increase. We prospectively followed 11 150 male physicians with no history of CVD or antihypertensive treatment through the 2-year questionnaire, after which follow-up began. Reported blood pressure was averaged from both the baseline and 2-year questionnaires. During a median follow-up of 10.8 years, there were 905 cases of incident CVD. For men aged <60 years (n=8743), those in the highest versus lowest quartiles of average SBP (>/=130 versus <116 mm Hg), DBP (>/=81 versus <73 mm Hg), and MAP (>/=97 versus <88 mm Hg) had relative risks (RRs) of CVD of 2.16, 2.23, and 2.52, respectively. Models with average MAP and PP did not add information compared with models with MAP alone (P>0.05). For men aged >/=60 years (n=2407), those in the highest versus lowest quartiles of average SBP (>/=135 versus <120 mm Hg), PP (>/=55 versus <44 mm Hg), and MAP (>/=99 versus <91 mm Hg) had RRs of CVD of 1.69, 1.83, and 1.43, respectively. The addition of other blood pressure measures did not add information compared with average SBP or PP alone (all P>0.05). These data suggest that average SBP, DBP, and MAP strongly predict CVD among younger men, whereas either average SBP or PP predicts CVD among older men. More research should distinguish whether MAP, highly correlated with SBP and DBP, better predicts CVD.

Adult↗
PubMed1993

The left ventricular end-systolic pressure and pressure-volume index. Comparison between invasive and auscultatory arm pressure measurements.

The slope of the left ventricular (LV) end-systolic pressure-volume relation (ESPVR) has been established as a valuable clinical method to assess LV contractile function independent of LV loading factors. The purpose of the present study was to evaluate whether the ESPVR could be reliably determined from auscultatory blood pressure (BP) measurements and from LV volume measurement by contrast ventriculography (CVG). Twenty-four patients with suspected or known ischemic heart disease were studied by cardiac catheterization with simultaneous, blinded, intravascular and auscultatory pressure measurements. LV volume was determined by CVG. The auscultatory mean arterial blood pressure (MAP) derived from: [formula: see text] was found to be a useful measure of the LV end-systolic pressure in this connection. The correlation between invasively measured LV end-systolic pressure (ESP) and MAP was highly significant (r = 0.82; SEE = 6.9 mmHg; p = 0.001). The correlation between invasively and semi-invasively measured ESPVR fell close to the line of identity (r = 0.99; SEE = 0.23 mmHg.mL-1; p < 0.001). The replacement of ESP by MAP induced only a minimal error in the assessment of the ESPVR. A complete noninvasive determination of the ESPVR and LV contractility therefore seems possible by using the MAP and by measuring the end-systolic volume by radionuclide ventriculography or by echocardiography.

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↗