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At least 109 records · Page 6Linked to original sources
PubMed1984

[Pressure control of a pressurized proportional counter for 4 pi beta-gamma coincidence counting--effects of pressure variation and study of a non-flow type system].

Effects of the pressure variation of counting gas on the efficiency function were examined using a 4 pi beta-gamma coincidence counting system with a pressurized proportional counter. The results showed that the pressure variation of about ten kPa could not give large effects on the efficiency function and that a non-flow type of pressurized proportional counter with a simple gas control system could work well in the case of the pressure higher than 1 MPa, an ordinary pressure for the counting.

Beta Particles↗
PubMed1988

Angiotensin converting enzyme inhibition decreases systolic blood pressure more than diastolic pressure as shown by ambulatory blood pressure monitoring.

Non-invasive ambulatory blood pressure monitoring (Spacelabs 5200) was carried out before and 3 months after treatment with perindopril, a new angiotensin converting enzyme (ACE) inhibitor given at 4-8 mg once a day in the morning. Twenty-one patients with sustained essential uncomplicated hypertension were analysed. The 24-h mean values for systolic and diastolic blood pressure, their standard deviations (absolute variability) and their coefficients of variation were compared before and after the administration of perindopril, using a two-way analysis of variance. In order to determine whether perindopril could decrease systolic more than diastolic pressure, we evaluated the relationship between systolic and diastolic blood pressure as recorded by the Spacelabs monitor. The correlation coefficient between these two parameters was calculated before (r = 0.82) and after (r = 0.76) treatment. Comparison between the corresponding slopes indicated that, at any given value of diastolic blood pressure, systolic blood pressure was lower after than before the administration of perindopril.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Heart-lung interactions during positive pressure ventilation: left ventricular pressure-volume momentary response to airway pressure elevation.

BACKGROUND: Left ventricular (LV) pressure and volume changes are known to occur in response to positive airway pressure (PAP). We aimed to further describe the immediate LV response to increased PAP as demonstrated in successive heart cycles with LV pressure and volume alterations. We postulated that these acute systematic LV events during institution of PAP can follow a distinct pattern that would allow calculation of parameters of systolic function, including end-systolic elastance (Ees) and preload recruitable stroke work (PRSW). We also aimed to examine the relationship of PAP-derived Ees and PRSW to the same parameters derived from vascular occlusion. METHODS: Eight anesthetized adult pigs were studied with invasive circulatory measurements including LV pressure and volume (conductance). The PAP intervention was an airway pressure plateau of 15 cm H2O for 6 s (APP). Venous occlusion was performed by transient balloon inflation in the inferior vena cava (IVCO). Ees and PRSW were derived for each APP and IVCO intervention. RESULTS: Central circulatory variables during APP and IVCO are reported. LV systolic function parameters could be derived from each of the heart-lung interactions during APP sequences. Ees and PRSW derived from APP showed a significant positive bias in relation to those derived from the IVCO sequence. CONCLUSIONS: We conclude that the heart-lung interactions during APP of the magnitude and duration shown here can allow derivation of Ees and PRSW. These parameters are not interchangeable with Ees and PRSW derived from IVCO.

Air Pressure↗
PubMed1981

Effects of alterations of inspiratory and expiratory pressures and inspiratory/expiratory ratios on mean airway pressure, blood gases, and intracranial pressure.

Twenty neonates requiring mechanical ventilation for respiratory failure, including 13 with hyaline membrane disease, were studied to assess the effects of alterations in ventilator settings on mean airway pressure (MAP), blood gases, and intracranial pressure (ICP). The study involved random alterations in peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), and inspiratory/expiratory ratio while MAP, PaO2, ICP, and end-tibal PCO2 were continuously monitored. The results showed a significant relationship between MAP and PaO2 that was expressed as the change in PaO2 per millimeter of mercury change in MAP (delta PaO2/delta MAP) with a mean delta PaO2/delta MAP of 4.92. The delta PaO2/delta MAP was highest for changes in PEEP (6.08), followed by PIP (5.07), and inspiratory/expiratory ratio (1.9). There was a significant relationship between alterations in PEEP and PIP vs PaCO2 and pH. Increases in PEEP and decreases in PIP resulted in an elevated PaCO2 and a lowered pH, and decreases in PEEP and increases in PIP resulted in a decreased PaCO2 and an elevated pH. There was no significant relationship between MAP and ICP, but there was a significant association between delta ICP and delta PaCO2 during alterations in PIP (r = .64, P less than .001). Increases in PEEP will lead to the greatest increase in PaO2 per change in MAP, followed by increase in PIP and inspiratory/expiratory ratio using a pressure-limited ventilator.

Airway Resistance↗
PubMed1994

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

Torasemide, a puridine-3-sulfonylurea derivative, is a lipophilic diuretic compound. It interacts with the Na+2Cl-K+ carrier and at higher concentrations with the chloride channels. The lipophilic nature of torasemide may determine its access to glial and neuronal cells across the blood brain barrier. The present study was performed to establish whether torasemide could modify intracranial pressure and cytotoxic brain edema in functionally nephrectomized Wistar rats (150-240 g). Brain edema of the cytotoxic type was induced by infusion of 100 ml aqua bidest/kg body weight. After the end of the infusion 100 mg torasemide/kg body weight or a corresponding volume of isotonic saline were injected followed by continuous continued recording of ICP and systemic arterial pressure for at least 3 hours. Torasemide prevented the rise in intracranial pressure seen in control animals. The ICP values for the torasemide-treated animals were lower at all points. Following intravenous injection of 100 mg torasemide/kg body weight at 50, 60, 70, 90 and 120 minutes a significant decrease of intracranial pressure compared to that in controls was observed. Torasemide may be a useful adjunct in the therapy of brain edema and increased intracranial pressure.

Animals↗
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↗
PubMed1981

Positive end-expiratory pressure (PEEP) and cerebrospinal fluid pressure during normal and elevated intracranial pressure in dogs.

The effect of up to 15 cm H2O positive end-expiratory pressure (PEEP) on cerebrospinal fluid pressure (Pcsf) was investigated in five anaesthetised, mechanically ventilated dogs during normal and then elevated (40-50 cm H2O) intracranial pressure (ICP). Stepwise elevations of PEEP in 5 cm H2O increments resulted in small rises in Pcsf at normal ICP and in significantly larger rises when ICP was elevated. The regression equations for the relationships between Pcsf and end-expiratory pressure (EEP) were as follows: Pcsf = 12.95 + 0.82 EEP for normal ICP, and Pcsf = 46.41 + 2.06 EEP for elevated ICP. Mean PaCO2 rose from 39.7 +/- 2.5 to 47.6 +/- 5.0 torr during normal ICP, and from 34.2 +/- 2.9 to 50.9 +/0- 5.3 torr at elevated ICP as PEEP was elevated to 15 cm H2O. We conclude that PEEP raised Pcsf, and that this increase is more severe under conditions of elevated ICP. The rise in Pcsf due to PEEP may be explained by either the rise in intrathoracic pressure or the rise in PaCO2, or both.

Animals↗
PubMed1998

[Home blood pressure measurement and ambulatory blood pressure measurement versus office blood pressure measurement].

PURPOSE: To compare both home blood pressure measurement (HBPM) and ambulatory blood pressure monitoring (ABPM) with office blood pressure measurement (OBP); and also to compare the correlation between HBPM and OBP with LVMI (left ventricular mass index). METHODS: Protocol 1--68 hypertensive patients (58 +/- 12 years, 37 females): a) self recorded blood pressure at home in the 7 days; b) recorded the ABPM during 24 hours; and c) the physician recorded blood pressure in the office. Protocol 2-41 hypertensive patients underwent the HBPM, OBP, and BI-dimensional echocardiogram. RESULTS: Protocol 1--OBP (153 +/- 24/96 +/- 13 mmHg) was higher (p < 0.05) than HBPM (133 +/- 18/84 +/- 12 mmHg) and ABPM (137 +/- 17/87 +/- 12 mmHg); Protocol 2--LVMI correlated better with HBPM (r = 0.39/0.49, p < 0.05, systolic and diastolic, respectively) than OBP (r = 0.02/ 0.22, p > 0.05, systolic and diastolic, respectively). CONCLUSION: This study showed that HBPM has a better correlation with LVMI than OBP.

Adult↗
PubMed2004

Recommendations for blood pressure measurement in humans and experimental animals: Part 1: blood pressure measurement in humans: a statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research.

Accurate measurement of blood pressure is essential to classify individuals, to ascertain blood pressure-related risk, and to guide management. The auscultatory technique with a trained observer and mercury sphygmomanometer continues to be the method of choice for measurement in the office, using the first and fifth phases of the Korotkoff sounds, including in pregnant women. The use of mercury is declining, and alternatives are needed. Aneroid devices are suitable, but they require frequent calibration. Hybrid devices that use electronic transducers instead of mercury have promise. The oscillometric method can be used for office measurement, but only devices independently validated according to standard protocols should be used, and individual calibration is recommended. They have the advantage of being able to take multiple measurements. Proper training of observers, positioning of the patient, and selection of cuff size are all essential. It is increasingly recognized that office measurements correlate poorly with blood pressure measured in other settings, and that they can be supplemented by self-measured readings taken with validated devices at home. There is increasing evidence that home readings predict cardiovascular events and are particularly useful for monitoring the effects of treatment. Twenty-four-hour ambulatory monitoring gives a better prediction of risk than office measurements and is useful for diagnosing white-coat hypertension. There is increasing evidence that a failure of blood pressure to fall during the night may be associated with increased risk. In obese patients and children, the use of an appropriate cuff size is of paramount importance.

Adult↗
PubMed1981

Swan-Ganz catheter location and left atrial pressure determine the accuracy of the wedge pressure when positive end-expiratory pressure is used.

In 43 percent of 30 consecutive open heart surgery patients, Swan-Ganz catheter tips lodged within 1 cm of or above the left atrium. When in this position the wedge pressure measured by the catheter was not an accurate estimate of left atrial pressure when positive end-expiratory pressure (PEEP) was used, especially when left atrial pressure was low. Catheters located below the left atrium were accurate at all levels of PEEP tested. The position of Swan-Ganz catheters should be confirmed by a lateral chest roentgenogram when PEEP is used, and catheter tips not below the left atrium should be repositioned.

Atrial Function↗
PubMed1981

The effect of haemodilution on arterial blood pressure, central venous pressure, intracranial and intra-ocular pressures in pigs.

During the open-heart surgery, haemodilution is performed before extracorporeal circulation is started by the sampling of autologous blood and substituting an electrolyte solution. Following extracorporeal circulation, first the machine-blood and then the autologous blood is reinfused. The haemodilution and reinfusion procedures lead to alterations in blood osmolality and tissue fluid distribution, initiating changes in arterial blood pressure, central venous pressure, intracranial and intraocular pressures. These changes were studied in pigs. It is believed that these potentially hazardous pressure alterations can be minimized through proper handling of the procedure. This study presents some of the mechanisms involved.

Animals↗
PubMed2003

Effects of pressure- and volume-controlled inverse ratio ventilation on haemodynamic variables, intracranial pressure and cerebral perfusion pressure in rabbits: a model of subarachnoid haemorrhage under isoflurane anaesthesia.

BACKGROUND AND OBJECTIVE: An inverse I : E ratio (inspiratory time > expiratory time) may have benefits in patients suffering trauma who requiring lung ventilation. However, this application may be deleterious if there is concomitant head injury. We aimed to determine the physiological effects of pressure- and volume-controlled modes of inverse ratio (I : E = 2 : 1) ventilation of the lungs, while maintaining normocapnia, in a rabbit model of raised intracranial pressure (ICP). METHODS: New Zealand White rabbits were anaesthetized with isoflurane and a tracheostomy was performed. Subarachnoid haemorrhage was simulated in two groups by injecting blood into the cisterna magna. Groups 1 and 2 (n = 6, each), controls, were compared with Groups 3 and 4 (n = 6, each) with the simulated subarachnoid haemorrhage. Each ventilation mode was used with an I : E ratio of 2 : 1 for 30 min. Mean arterial pressure (MAP), ICP, cerebral perfusion pressure (CPP), mean airway pressure (P(AW)) and arterial blood-gas status were measured. RESULTS: Both modes increased mean P(AW) (P < 0.02). This increase was greater with the volume-controlled mode (P < 0.02). The baseline value averaged 5.8 +/- 0.4 and 5.6 +/- 0.3 mmHg in Groups 3 and 4, respectively, and increased to 7.8 +/- 0.3 and 10.8 +/- 0.4 mmHg. Inducing subarachnoid haemorrhage increased ICP and MAP (P < 0.02). Baseline ICPs were 10.3 +/- 0.5 and 10.3 +/- 0.4 mmHg in Groups 1 and 2, respectively, whereas they were 25.4 +/- 1.2 and 25.8 +/- 0.8 mmHg in Groups 3 and 4. However, ICP, MAP and CPP did not differ significantly according to the mode. CONCLUSIONS: An already raised ICP was altered by the application of induced mean PAW increases as a consequence of inverse ratio ventilation of the lungs with normocapnia.

Anesthetics, Inhalation↗
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↗