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At least 523 records · Page 29Linked to original sources
PubMed2003

Estimation of central aortic pressure by SphygmoCor requires intra-arterial peripheral pressures.

Central arterial pressure, measured close to the heart, may be of more patho-physiological importance than conventional non-invasive cuff blood pressure. The technique of applanation tonometry using SphygmoCor has been proposed as a non-invasive method of estimating central pressure. This relies on mathematically derived generalized transfer functions, which have been previously validated using invasive peripheral pressure measurements. We compared simultaneous estimates of central aortic pressure using this technique with those measured directly during the routine diagnostic cardiac catheterization of 30 subjects (age range 27-84 years), half of whom were aged 65 years or more. This was done by applanating the left radial artery and recording the non-invasive brachial cuff blood pressure to generate a central aortic pressure estimate, using the SphygmoCor radial transfer function. The comparative results were analysed using Bland-Altman plots of mean difference. SphygmoCor, on average, underestimated systolic central arterial pressure by 13.3 mmHg and overestimated diastolic pressure by 11.5 mmHg. The results were similar in patients aged under and above 65 years. Furthermore, non-invasively measured brachial pressures were seen to give an overall closer estimate of the central arterial pressure than the SphygmoCor system. The transfer function has been validated from invasively measured arterial pressures and the current use by the system of non-invasive measures may explain the discrepancies. However, age, drugs and arterial disease would also be expected to play a role.

Adult↗
PubMed2004

Air pressure responses to sudden vocal tract pressure bleeds during production of stop consonants: new evidence of aeromechanical regulation.

Two studies were conducted to evaluate short-latency vocal tract air pressure responses to sudden pressure bleeds during production of voiceless bilabial stop consonants. It was hypothesized that the occurrence of respiratory reflexes would be indicated by distinct patterns of responses as a function of bleed magnitude. In Study 1, 19 adults produced syllable trains of "puh" using a mouthpiece coupled to a computer-controlled perturbator. The device randomly created bleed apertures that ranged from 0 to 40 mm2 during production of the 2nd or 4th syllable of an utterance. Although peak oral air pressure dropped in a linear manner across bleed apertures, it averaged 2 to 3 cm H2O at the largest bleed. While slope of oral pressure also decreased in a linear trend, duration of the oral pressure pulse remained relatively constant. The patterns suggest that respiratory reflexes, if present, have little effect on oral air pressure levels. In Study 2, both oral and subglottal air pressure responses were monitored in 2 adults while bleed apertures of 20 and 40 mm2 were randomly created. For 1 participant, peak oral air pressure dropped across bleed apertures, as in Study 1. Subglottal air pressure and slope, however, remained relatively stable. These patterns provide some support for the occurrence of respiratory reflexes to regulate subglottal air pressure. Overall, the studies indicate that the inherent physiologic processes of the respiratory system, which may involve reflexes, and passive aeromechanical resistance of the upper airway are capable of developing oral air pressure in the face of substantial pressure bleeds. Implications for understanding speech production and the characteristics of individuals with velopharyngeal dysfunction are discussed.

Adolescent↗
PubMed2002

Contralateral response in renal pelvic pressure and diuresis during increasing ipsilateral pelvic pressure and flow: a study of the normal and denervated upper urinary tract in pigs.

OBJECTIVE: To examine, in young pigs, changes in baseline pelvic pressure and diuresis in the contralateral kidney during conditions of increasing pelvic pressure and perfusion with isotonic saline in the ipsilateral renal pelvis; the role of a reno-renal nervous mechanism was examined by denervating the kidneys, and the effect of bladder filling on these variables assessed. MATERIALS AND METHODS: Female pigs (37-40 kg) were assessed under general anaesthesia. Transparenchymally, one 6 F and two 6 F catheters were introduced into the right and left renal pelvis, respectively. Through a bladder incision an 8 F catheter was introduced 10 cm into the right ureter to collect urine and the orifice closed around the catheter. For bladder drainage and to measure bladder pressure a 10 F catheter was placed in the bladder and both the 8 F and 10 F catheters lead out through the urethra. In group A, five animals served as controls, with group B comprising eight with intact nerves and group C eight with denervated kidneys. In group B and C the left renal pelvis was perfused with isotonic saline at 2, 4, 6, 8, 10, 12 and 16 mL/min while the bilateral pelvic pressure and right renal diuresis were recorded; the bladder was kept empty and 0.5 h later the left pelvis was perfused with 10 mL/min while the bladder catheter was closed. Perfusion continued until micturition occurred. The bilateral pelvic pressure, bladder pressure and right renal diuresis were recorded. In group C the kidneys were surgically denervated, dividing all adhesions and all connective tissue around the pelvis and the vascular pedicle. The renal artery was freed to the aortic level. RESULTS: During the pressure-perfusion study the mean (sd) right pelvic pressure was 7.4 (0.2) mmHg in group B and 8.6 (0.2) mmHg in group C. The diuresis from the right kidney in both groups was similar and the same as that in group A. The perfusion rate and pressure on the left side had no influence on pelvic pressure and diuresis on the right side. During perfusion with a full bladder the right pelvic pressure was 8.6 mmHg in group B and 9.5 mmHg in group C. Diuresis in group B was approximately 0.6 mL/min and a little higher in group C, at approximately 1 mL/min, but identical to that in group A. CONCLUSION: These results indicate that a reno-renal reflex mechanism has no apparent role in young pigs during pressure-perfusion measurements with an empty or full bladder.

Animals↗
PubMed1998

Intramuscular pressure in the erector spinae and intra-abdominal pressure related to posture and load.

STUDY DESIGN: Intramuscular pressures in both Erectors Spinae and intra-abdominal pressures were measured during different holding tasks. OBJECTIVES: To investigate the potential for using intramuscular pressure measurements in both Erectors Spinae to better quantitate the role of muscles during different lifting tasks in vivo. SUMMARY OF BACKGROUND DATA: Intramuscular pressure and intra-abdominal pressure were measured previously under isometric and dynamic conditions. However, no previous study systematically has addressed the relation between intramuscular and intra-abdominal pressures and different loads, tasks, and postures. METHODS: Intramuscular and intra-abdominal were measured simultaneously with microtip pressure transducers in 10 healthy volunteers performing 24 different static holding tasks. Tasks included different weights (10 kg and 20 kg), postures (squat or back lift), and positions of the weight. RESULTS: Intramuscular pressures were dependent on posture. Kyphotic back posture produced intramuscular pressures of 120-130 mm Hg, compared with the 10-25 mm Hg produced when volunteers were in the erect position (P < 0.001). Holding a 10-kg weight at the thighs close to the body produced significantly (P < 0.001) lower intramuscular pressures (25-32 mm Hg) than that produced by holding it 25 cm in front of the body (47-56 mm Hg). In all tasks, intramuscular pressures were significantly higher with the 20-kg weight than with the 10-kg weight (P < 0.001). Highest values (> 300 mm Hg) were measured when the 20-kg weight was held in the kyphotic posture above the floor and 25 cm away from the body. CONCLUSIONS: Intramuscular pressure measurements in the erector spinae seem to be a valuable tool for quantitating the role of back muscles during different lifting tasks.

Abdomen↗
PubMed2005

Validation of direct intraabdominal pressure measurement using a continuous indwelling compartment pressure monitor.

BACKGROUND: According to recommendations, intraabdominal pressure should be monitored every 8 hours for patients at high risk of abdominal compartment syndrome. Continuous intraabdominal pressure monitoring may be valuable for these patients. METHODS: For 15 patients undergoing laparoscopic surgery, a pressure monitor was introduced after formation of pneumoperitoneum. During the procedure, the laparoscopic insufflator pressure was varied. The pressure monitor values and the time to equilibrium were recorded. RESULTS: Altogether, 152 pressure recordings were taken for the patients studied. The measurements from the insufflator and pressure monitor were compared using a Bland-Altman plot. The mean difference between the techniques was 0.04 +/- 3.8, and 95% of the points from the pressure monitor were within two standard deviations of the mean difference. Pressure changes were essentially "real time." CONCLUSIONS: The intracompartmental pressure monitor provides accurate, rapid, and direct measurement of intraabdominal pressure, and may be a useful tool for continuous intraabdominal pressure measurement among patients at risk of abdominal compartment syndrome.

Abdomen↗
PubMed1988

Pressure infusor devices. Do they generate the pressures indicated?

Three currently available pressure infusor devices, based on three different principles, were tested to see if the pressure reading on the infusor manometer corresponds to the pressure generated in the infusion system. Each device was tested in two ways. First, the pressure generated in the infusion system was measured when the infusor bag pressure was maintained at 300 mmHg while the infusion bag was emptied in aliquots of 50 ml. Second, the pressures in the infusor bag required to maintain a pressure of 300 mmHg were measured as the infusion bag was emptied stepwise. The results reveal surprisingly large discrepancies between the pressure registered on the infusor manometer and the actual pressure generated in the fluid, which are not due to manometer inaccuracy. The degree of discrepancy depends on the amount of fluid that remains in the infusion bag and, when the infusor manometer shows a pressure of 300 mmHg, pressure in the fluid can be as much as 170 mmHg above or 200 mmHg below this value. Furthermore, it was impossible to maintain a pressure of 300 mmHg in the infusion system using one of the devices despite the fact that 100 ml fluid remained. The clinical significance of these findings is discussed.

Infusions, Parenteral↗
PubMed1994

Relation of maternal blood pressure during pregnancy to birth weight and blood pressure in children. The Hypertension in Pregnancy Offspring Study.

OBJECTIVE: To evaluate the importance of perinatal factors, e.g. low birth weight, reduced gestational period and elevated maternal blood pressure during pregnancy, as well as high maternal blood pressure at follow-up 7-12 years after pregnancy, on blood pressure in children born after normotensive and hypertensive pregnancies. DESIGN: Follow-up study in children from hypertensive pregnancies and a control group of children born after normotensive pregnancies. SETTING: University Hospital, Göteborg, Sweden. SUBJECTS: Thirty-six children born after hypertensive pregnancies and a control group of 17 children born after normotensive pregnancies were studied at a mean age of 12.5 years. MAIN OUTCOME MEASURE: Blood pressure. RESULTS: Systolic blood pressure was higher in children born after hypertensive pregnancies. They also had lower birth weight and a shorter gestational period. There was a negative correlation between the highest recorded maternal blood pressure during pregnancy and birth weight of the child and a positive correlation between maternal blood pressure and blood pressure in their offspring. No correlation was found between birth weight and blood pressure in these children. CONCLUSIONS: Children born after hypertensive pregnancies have higher blood pressure compared to children born after normotensive pregnancies. There is a positive relationship between childhood blood pressure and maternal blood pressure during pregnancy.

Adolescent↗
PubMed1995

Capillary pressure during and after incremental venous pressure elevation in man.

1. The relationship between capillary pressure and venous pressure was investigated during incremental venous pressure elevation in seven healthy volunteers. Pressure was measured simultaneously at the apex of finger nailfold capillaries and in the dorsal vein of the ipsilateral hand. Elevation of venous pressure was accomplished by inflation of a sphygmomanometer cuff around the upper arm. 2. As venous pressure rose, apical capillary pressure (Pc) approached venous pressure (Pv). For changes in Pv greater than 20 mmHg, the increment in Pc was invariably less than the increment in Pv. 3. Above a cuff pressure of 20 mmHg, capillary pulse pressure amplitude (CPPA) tended to decline. At 50 mmHg cuff pressure, CPPA was lower than at baseline for all subjects. At baseline, CPPA was 4.2 +/- 2.0 mmHg (mean +/- S.D.) and at 50 mmHg it was 2.3 +/- 1.1 mmHg (P = 0.02). 4. In the period between 1 and 6 min following cuff release, both Pc and CPPA were lower than at baseline. (At baseline, Pc was 16.1 +/- 2.3 mmHg and following cuff release it was 11.2 +/- 1.5 mmHg (P = 0.02). At baseline, CPPA was 4.2 +/- 2.0 mmHg and following cuff release it was 1.8 +/- 1.1 mmHg (P = 0.03).) 5. Estimated changes in the ratio of pre- to postcapillary resistance (Ra/Rv), using arterial blood pressure (Pa) measured in the contralateral arm, and taking (Pa-Pc)/(Pc-Pv) to approximate to Ra/Rv, closely mirrored changes in CPPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Comparative study of pressure-induced germination of Bacillus subtilis spores at low and high pressures.

We have studied pressure-induced germination of Bacillus subtilis spores at moderate (100 MPa) and high (500 to 600 MPa) pressures. Although we found comparable germination efficiencies under both conditions by using heat sensitivity as a criterion for germination, the sensitivity of pressure-germinated spores to some other agents was found to depend on the pressure used. Spores germinated at 100 MPa were more sensitive to pressure (>200 MPa), UV light, and hydrogen peroxide than were those germinated at 600 MPa. Since small, acid-soluble proteins (SASPs) and dipicolinic acid (DPA) are known to be involved in spore resistance to UV light and hydrogen peroxide, we studied the fate of these compounds during pressure germination. DPA was released upon both low- and high-pressure germination, but SASP degradation, which normally accompanies nutrient-induced germination, occurred upon low-pressure germination but not upon high-pressure germination. These results adequately explain the UV and hydrogen peroxide resistance of spores germinated at 600 MPa. The resistance to pressure inactivation of 600-MPa-germinated spores could also, at least partly, be attributed to alpha/beta-type SASPs, since mutants deficient in alpha/beta-type SASPs were more sensitive to inactivation at 600 MPa. Further, germination at 100 MPa resulted in rapid ATP generation, as is the case in nutrient-induced germination, but no ATP was formed during germination at 600 MPa. These results suggest that spore germination can be initiated by low- and high-pressure treatments but is arrested at an early stage in the latter case. The implications for the use of high pressure as a preservation treatment are discussed.

Adenosine Triphosphate↗
PubMed1989

Diastolic pressure determines autonomic responses to pressure perturbation in humans.

Arterial baroreceptors reflexly regulate sympathetic and heart rate responses to alteration of blood pressure. The primary mechanical determinant of arterial baroreceptor activity in humans remains unclear. We examined the influence of systolic, diastolic, pulse, and mean arterial pressures on efferent muscle sympathetic nerve activity (MSNA, microneurography) and heart rate responses during perturbation of arterial pressure in 10 normal human subjects [age 25 +/- 2 (SE) yr]. We directly measured arterial pressure, heart rate, and MSNA during intravenous vasodilator infusion (nitroprusside, 6 +/- 1 micrograms.kg-1.min-1, n = 6; or hydralazine, 16 +/- 2 mg, n = 4) while central venous pressure was held constant by simultaneous volume expansion. Changes in arterial pressures were compared with changes in heart rate and MSNA over 3-min periods of vasodilator infusion during which we observed increases in systolic and pulse pressures with simultaneous decreases in mean and diastolic pressures. During vasodilator infusion, there were increases in systolic (124.2 +/- 2.1 to 131.7 +/- 2.9 Torr, P less than 0.001) and pulse pressures (57.0 +/- 2.2 to 72.7 +/- 2.7 Torr, P less than 0.001) although mean arterial pressure fell (88.0 +/- 2.6 to 80.4 +/- 2.7 Torr, P less than 0.001) because of decreases in diastolic pressure (67.2 +/- 3.0 to 59.0 +/- 2.7 Torr, P less than 0.001). The changes in arterial pressures were accompanied by simultaneous increases in heart rate (66.4 +/- 3.0 to 92.6 +/- 4.8 beats/min, P less than 0.001) and MSNA (327 +/- 59 to 936 +/- 171 U, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1999

Influence of balloon pressure during stent placement in native coronary arteries on early and late angiographic and clinical outcome: A randomized evaluation of high-pressure inflation.

BACKGROUND: High-pressure dilatation is considered a better stent placement strategy, but this has not yet been proved by appropriately designed studies. The objective of this randomized trial was to assess the role of high-pressure dilatation in the early and late outcome of patients undergoing coronary stent placement. METHODS AND RESULTS: Consecutive patients with coronary stent placement were randomly assigned to high- (15 to 20 atm, 468 patients) or low- (8 to 13 atm, 466 patients) balloon-pressure dilatation. The primary end point of the study was the event-free survival at 1 year. Secondary end points were the incidence of stent thrombosis at 30 days and angiographic restenosis (>/=50% diameter stenosis) at 6 months. The incidence of stent thrombosis was 1.7% in the high-pressure and 1.9% in the low-pressure group (relative risk 0.89; 95% CI 0.30 to 2.56). During the first 30 days, although there was no significant difference in the incidence of Q-wave myocardial infarction, the incidence of non-Q-wave infarction was 6.4% in the high-pressure and 3.4% in the low-pressure group (relative risk 1. 87; 95% CI 1.02 to 3.42). The restenosis rate was 30.4% in the high-pressure and 31.4% in the low-pressure group (relative risk 0. 97; 95% CI 0.75 to 1.26). Event-free survival at 1 year was not significantly different between the groups, with 78.8% in high-pressure patients and 75.5% in patients assigned to low-pressure dilatation (hazard ratio 0.85; 95% CI 0.65 to 1.11). CONCLUSIONS: The systematic use of high-balloon-pressure inflation (15 to 20 atm) during coronary stent placement is not associated with any significant influence on the 1-year outcome of patients undergoing this intervention.

Aged↗
PubMed2006

A new method for estimating arterial occlusion pressure in optimizing pneumatic tourniquet inflation pressure.

To reduce pressure-related injuries resulting from pneumatic tourniquet use, the lowest possible inflation pressure is recommended. Arterial occlusion pressure (AOP) is a measure of the cuff pressure required to maintain a bloodless surgical field. However, its determination method is time consuming, requires operator skill, and is therefore seldom used in current practice. An AOP estimation can be made by knowing the pressure transmitted to the underlying soft tissues. We measured upper and lower extremity tissue pressures under the tourniquet cuff at 100, 200, and 300 mm Hg of tourniquet inflation pressures in 30 anesthetized living adult patients. All patients received general anesthesia with neuromuscular relaxation. A Stryker intra-compartmental pressure monitor was used to measure tissue pressures under the tourniquet cuff. In all patients, the soft tissue pressures were consistently lower than the applied tourniquet inflation pressures. Our results revealed tissue padding coefficients for extremities 20 to 75 cm in circumferences. An estimation method of AOP was developed [AOP = (systolic blood pressure + 10)/Tissue padding coefficient]. The new AOP estimation method may be a simple, rapid, and clinically practical alternative to the AOP determination method.

Adolescent↗
PubMed1991

High-volume, low-pressure cuffs. Are they always low pressure?

Ischemic tracheal complications due to the ETT cuff occur in approximately 10 percent of mechanically ventilated critically ill patients despite the use of high-volume, low-pressure ETT cuffs. Using a laboratory model, we studied the effects of airway pressure on three different ETT cuff designs, including two "low pressure" designs. Positive airway pressure acted on the "low pressure" cuffs to create a "self-sealing" effect that maintained tracheal occlusion despite airway pressures that exceeded cuff inflation pressure. Increases in airway pressure caused by decreased lung compliance resulted in higher cuff inflation pressures in all three groups, with the smallest increase occurring in the design that had the longest tracheal contact length. We conclude that the current high-volume, low-pressure ETT cuff design currently used does not guarantee low cuff pressure when high airway pressures occur, and an alternative design should be developed.

Airway Resistance↗
PubMed1992

Does radial artery pressure accurately reflect aortic pressure?

STUDY OBJECTIVE: Our objective was to determine whether the systolic, diastolic, and mean arterial pressures measured in the radial artery accurately reflect corresponding pressures in the ascending aorta in narcotic-anesthetized patients with known obstructive coronary artery disease, before being subjected to cardiopulmonary bypass (CPB). DESIGN: This was a prospective study. SETTING: The cardiac operating room of a large, tertiary-care university medical center. PARTICIPANTS: Fifty-one patients (45 men and six women; age range, 48 to 77 years) with documented atherosclerotic coronary artery disease were studied. All patients underwent elective coronary artery bypass grafting after the study. INTERVENTIONS: Patients were premedicated with lorazepam and morphine 60 min before administration of Fentanyl-pancuronium anesthesia. The radial artery was cannulated before induction of anesthesia and the aorta approximately 45 min later. Comparisons of radial and aortic pressures were then performed. MEASUREMENTS AND RESULTS: Radial and aortic pressures were recorded through standard, fluid-filled, high-pressure, 91-cm (36-in) long tubing and disposable transducers, meticulously cleared of air bubbles. Additional measurements included cardiac output, central venous pressure, core temperature, blood gas levels, and hematocrit reading. Radial-aortic pressure differences were as follows: systolic arterial pressure (SAP), 12 +/- 1 mm Hg; mean arterial pressure (MAP), -0.8 +/- 0.3 mm Hg; and diastolic arterial pressure (DAP), -1.0 +/- 0.3 mm Hg. All were significant (p < 0.001), but the SAP difference was more than ten times that of either the MAP or the DAP values. The coefficients of determination (r2) indicated that the radial-aortic dependence was 0.44 for the SAP, 0.90 for the DAP, and 0.98 for the MAP relationship. Plotting the respective differences against the arithmetic mean of simultaneously measured pressures indicated that the radial SAP was 4 to 35 mm Hg higher than the aortic in 42 patients (82 percent) and was 10 to 35 mm Hg higher in 26 patients (51 percent); radial-aortic MAP differences clustered within 3 mm Hg in 47 patients (92 percent); radial DAP was +/- 3 mm Hg different from the aortic in 46 patients (90 percent). The largest MAP difference was -6 mm Hg in one patient. The largest DAP difference was +/- 5 mm Hg in three patients. CONCLUSIONS: In this group of patients, who were studied before undergoing CPB, the radial SAP gave a poor estimate of that present in the ascending aorta, since in more than 50 percent of the cases, the radial SAP was 10 to 35 mm Hg higher than that in the aorta. The radial MAP and DAP are reliable, since in 90 percent and 92 percent of the patients, respectively, the pressure differences were within +/- 3 mm Hg of those in the aorta.

Aged↗
PubMed1993

The effects of ventilator working pressure during pressure support ventilation.

The purpose of this study was to examine the consequences of altering ventilator working pressure on airway pressure and flow characteristics during pressure support ventilation (PSV). A ventilator (Siemens Servo 900C) and single lung simulator were used, and graphic read outs, in triplicate, were taken at a variety of combinations of PSV, working pressure, lung compliance, and airway resistance. The graphic read outs were then analyzed for a number of "dependent variables," and multiple regression analyses were performed using working pressure, PSV level, compliance, and resistance as "independent variables." The results show that the relative impact of working pressure on airway pressure and flow will vary with other lung and airway characteristics; also, excessive working pressure results in significantly greater flow rates at 40 ms after onset of inspiratory flow and at maximum flow, greater ringing or overshoot in the circuit, reduced tidal volume and inspiratory time, and reduced area under the airway pressure curve. In conclusion, adjusting ventilator working pressure will significantly affect lung-ventilator interaction in a quantifiable fashion. Further, these findings support clinical evidence that working pressure and/or initial flow rate need to be individualized to ensure optimal airway flow and pressure characteristics.

Airway Resistance↗
PubMed2001

A new model-based method of reconstructing central aortic pressure from peripheral arterial pressure.

We have shown in our previous study that the transfer function between central aortic pressure and tonometric radial arterial pressure can be modeled as a pure elastic lossless tube terminated with a modified Windkessel. We hypothesized, using the model-derived radial arterial flow, that central pressure could be reconstructed by adding the time-shifted forward and backward pressure components (Stergiopulos et al.: Am J Physiol 274: H1386---H1392, 1998). In eight patients (age 16--75), central micromanometric and radial arterial tonometric pressure were measured simultaneously. We imposed measured tonometric pressure to the terminal modified Windkessel to estimate radial arterial flow, with which tonometric pressure was separated into forward and backward components. These components were then appropriately time shifted, and summed to central pressure. We used average parameter values for the terminal impedance, but individualized the transmission delay. The poor correlation (r(2)) between tonometric and central pressure (0.264--0.765) was improved by both central pressure reconstruction methods (generalized transfer function: 0.887--0.974, model-based method: 0.849--0.979). The sensitivity analysis indicated that the key model parameter in reconstructing central pressure was the transmission delay. We conclude that our model-based method was capable of reconstructing central pressure as precisely as the generalized transfer function method, and also capable of individualizing the transfer function by changing the transmission delay.

Aorta↗
PubMed1998

Interaction of hydrostatic pressure, time and temperature of pressurization and pediocin AcH on inactivation of foodborne bacteria.

High hydrostatic pressure, because it can kill microorganisms, is being investigated for potential use as a nonthermal food preservation method. The objective of this study was to determine the hydrostatic pressurization parameters, pressure, time, and temperature, and a bacteriocin that in combination would destroy 7 to 8 log cycles of pathogenic and spoilage bacterial populations. We suspended cells of Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, Escherichia coli O157:H7, Lactobacillus sake, Leuconostoc mesenteroides, Serratia liquefaciens, and Pseudomonas fluorescens in peptone solution and exposed them to the combination of treatments. The combined parameters used were hydrostatic pressure (138 to 345 MPa), time (5 to 15 min), temperature (25 to 50 degrees C), and pediocin AcH (3,000 AU/ml, final concentration). In general, cell death increased as the pressure, time, or temperature increased; however, the cells developed proportionately greater sensitivity as the pressure increased to 276 MPa and higher and the temperature increased above 35 degrees C. Pressurization for longer than 5 min, especially at lower pressure and temperature ranges, had very little added benefit. Among the four gram-negative species, E. coli O157:H7 was the most resistant to pressurization while among the four gram-positive species, L. sake and L. mesenteroides had greater resistance. The death rate at high pressure (345 MPa) and high temperature (50 degrees C) in combination followed first-order kinetics; at lower pressure and temperature combination it showed a late tailing effect. Estimated D value data indicated that even at 345 MPa and 50 degrees C an 8-log-cycle viability loss could not be achieved within 5 min for all eight species. However, when pediocin AcH was included during pressurization this loss was achieved.

Bacteria↗
PubMedDate not supplied

The effect of pressure changes inside the antrum on lower esophageal sphincter (LES) pressure in man and dog.

The pressure change inside the lower esophageal sphincter (LES) in response to pressure changes inside the antrum was investigated in man and in dogs with antral pouches. In dogs with innervated antral pouches a pressure increase of 20 cm H2O inside the antrum produced an increase in LES pressure of 14 +/- 7 mm Hg, whereas an antral pressure of 80 cm H2O caused a decrease of 26 +/- 12 mm Hg in LES pressure (x +/- SD). Truncal vagotomy abolished LES response to the various antral pressures. In dogs with denervated antral pouches antral pressure changes did not influence LES pressure. In the dogs gastrin levels rose due to antral pressure increase; this was less pronounced in the dogs with denervated antral pouches than in the dogs with innervated antral pouches. In man a short antral pressure increase revealed a decrease in LES pressure. This effect was not seen in patients after selective proximal vagotomy.

Adult↗