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At least 19 recordsLinked to original sources
PubMed1989

Central venous pressure and pulmonary capillary wedge pressure as estimates of left atrial pressure: effects of positive end-expiratory pressure and catheter tip malposition.

We compared CVP and pulmonary capillary wedge pressure (WP) measurements with left atrial pressure (LAP) in postcoronary bypass surgical patients with preserved cardiopulmonary function. Measurements were obtained under normal conditions and conditions likely to induce WP-LAP discrepancies (PEEP and catheter tip malposition). Patients were in both supine and lateral positions; the catheter tip was placed vertically below (tip down; n = 12) or above (tip up; n = 5) the left atrium. Our data showed that both CVP and WP correlated well with LAP at all PEEP levels in the supine and tip down lateral positions. However, in the tip up lateral position, WP overestimated LAP (13.3 +/- 3.4 vs. 8.0 +/- 2 mm Hg; p less than .01) at 20 cm H2O of PEEP, whereas CVP (8.8 +/- 2.1 mm Hg) closely reflected LAP. Thus, by placing the catheter tip vertically below the left atrium in supinely and laterally positioned patients, CVP and WP both produced reliable estimates of LAP despite an acute increase in alveolar pressure. When the pulmonary artery catheter tip was vertically above the left atrium, WP overestimated LAP. Under these conditions, CVP remained a reliable estimate of LAP. We conclude that CVP measurement as an estimate of LAP in this patient population could be used and not ignored. This is true in patients with previously documented good LAP-CVP correlation who are subjected subsequently to conditions which may produce an LAP-WP discrepancy (high PEEP and catheter tip malposition).

Aged↗
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↗
PubMed1990

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

In the treatment of raised intracranial pressure (ICP) an agent is needed which can similarly reduce ICP and protect the brain without reducing systematic arterial pressure and cerebral perfusion pressure. Gammahydroxybutyrate (GHB) decreases cerebral metabolic requirement of oxygen (CMRO2) and glucose utilization rate. The effect of 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 mmHg; control: 16.20 +/- 8.89 mmHg; p less than 0.01) while increasing mean systemic arterial pressure (109.89 +/- 6.35 mmHg; control: 89.65 +/- 4.22 mmHg; p less than 0.05) and cerebral perfusion pressure (98.11 +/- 6.79 mmHg; control: 73.84 +/- 5.25 mmHg; 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 mmHg to 98.60 +/- 3.48 mmHg (p less than 0.02) and 400 mg/kg GHB to 108.00 +/- 5.20 mmHg (p less than 0.001) mean systemic arterial pressure. 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

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

[Doctor's-office blood pressure, home blood pressure, ergometry blood pressure and 24-hour blood pressure. The correlations with the echocardiographic parameters of heart muscle mass].

In 62 untreated hypertensives (31 men, 31 women; median age 40 [17-57] years) blood pressures (BP) were measured in the doctor's office, at home (self-measured) and every 15 min during 24-hour monitoring (by portable automated oscillometry), the results being compared with echocardiographic measurements of ventricular septal thickness (VST), left ventricular muscle mass (LVM) and left ventricular mass index (LVMI), in 41 of them also during and 5 min after 100 W bicycle ergometry. In the total cohort, 24-hour values correlated better with diastolic VST (systolic: r = 0.706, P less than 0.00001; diastolic: r = 0.507, P less than 0.0001) than office BP (systolic: r = 0.381, P less than 0.01; diastolic: r = 0.177, not significant) and home BP (systolic: r = 0.477, P less than 0.0001; diastolic: r = 0.371, P less than 0.05). In the 41 exercised hypertensives the correlation with echocardiographic values was less close than with their 24-hour BP, but slightly better than with office and home BP. Systolic BP correlated better than diastolic BP with echocardiographic values. VST generally correlated better with BP than LVM and LVMI. It is concluded that (1) 24-hour BP values correlate more closely with LVM than any other noninvasive BP measurement; (2) VST is affected more by systolic than diastolic BP; and (3) VST more specifically reflects the influence of BP on myocardial structure than does LVM and LVMI.

Adolescent↗
PubMed1988

Influences of pressure surrounding the heart and intracardiac pressure on the diastolic coronary pressure-flow relation in excised canine heart.

We investigated the change in the instantaneous diastolic left coronary pressure-flow relation (DPFR) when the pressure surrounding the heart (SHP), right heart pressure (RHP), and left heart pressure (LHP) were systematically varied. Eight excised and maximally vasodilated canine hearts placed in an air-tight chamber were used. To obtain a capacitance-free DPFR, coronary perfusion pressure was slowly decreased (about 2 mm Hg/sec) during a prolonged diastole. The zero-flow pressure (Pf = 0) and the slope of the DPFR were analyzed. The mean values of the slope did not change significantly throughout the interventions. The mean value of Pf = 0 in the control state (SHP = RHP = LHP = 0 mm Hg) was 6.0 +/- 2.0 mm Hg (mean +/- SD, n = 8), significantly higher than the venous outflow pressure, RHP (p less than 0.001), and the other two pressures (p less than 0.001). When SHP was raised to 15 and 30 mm Hg, while the other pressures remained at 0 mm Hg, the mean values of Pf = 0 increased to 20.9 +/- 2.4 and 35.6 +/- 3.1 mm Hg (p less than 0.001 and p less than 0.0005, respectively, vs. control). The mean values of Pf = 0 when only RHP was elevated to 15 and 30 mm Hg were 16.0 +/- 1.5 and 29.3 +/- 1.5 mm Hg (p less than 0.001 and p less than 0.0005 vs. control). On elevation of LHP to 15 and 30 mm Hg, the mean values of Pf = 0 were 12.0 +/- 2.8 and 17.3 +/- 3.6 mm Hg (p less than 0.01 and p less than 0.01 vs. control). When both SHP and LHP were almost evenly elevated to about 15 and 30 mm Hg, the mean values of Pf = 0 were raised to 22.0 +/- 2.9 and 35.3 +/- 3.2 mm Hg, respectively. These mean values were not significantly different from those when only SHP was elevated to the comparable levels. The observation that Pf = 0 exceeded RHP in the control state and that RHP, which was elevated above the preceding Pf = 0, was identical with the present Pf = 0 supports the vascular waterfall mechanism when RHP is low. Furthermore, the evidence that the degree of DPFR shift was almost linearly dependent on the SHP level rather than on the LHP level indicates that the pressure on the epicardial side is one of the factors that determines the pressure at the top of the vascular waterfall.

Animals↗
PubMedDate not supplied

Interstitial fluid pressure in the facial nerve: relationship between facial nerve pressure and cerebrospinal fluid pressure.

The possibility of measuring interstitial pressure in the facial nerve using a servo-nulling system was investigated. As a pilot study, interstitial fluid pressure in the extirpated medulla oblongata was measured using this system, and was found to be proportional to the pressure applied to the surrounding tissue block. Interstitial fluid pressure of the facial nerve in guinea pigs was also measurable with this system. The pressure in the facial nerve fluctuated with respiration and/or heart beat, as did CSF pressure. Respiratory fluctuations in facial nerve and CSF pressures ceased when the respirator was stopped. Facial nerve pressure appeared to be closely related to CSF pressure; the injection of saline into the CSF space resulted in an increase in facial nerve pressure. Measurement of facial nerve pressure by a servo-nulling system should be useful in evaluating the pathogenesis underlying facial palsy.

Animals↗
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↗
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↗
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↗
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↗