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At least 73 records · Page 4Linked to original sources
PubMed1982

Pulmonary artery pressure versus pulmonary capillary wedge pressure and central venous pressure in shock.

Evidence is presented from 43 dogs and 30 patients that under conditions of severe hemorrhagic, traumatic or septic shock, there may be partial obstruction of the pulmonary microcirculation due to disseminated intravascular coagulation (DIC) particularly in the pulmonary venules. This may cause the left atrial pressure to fall and the pulmonary artery pressure to rise, in some cases drastically. Pulmonary edema may result. This dangerous rise in pulmonary artery pressure is not reflected by the wedged pulmonary artery catheter which will monitor only the status of the left heart. Central venous pressure (CVP) may remain within normal limits even after pulmonary artery pressure has risen to dangerous levels with the development of pulmonary edema. It is only with right ventricle failure against the high pulmonary pressure that CVP rises. It is concluded that pulmonary artery pressure measurements are very important in monitoring intravenous fluid administration in severe shock. Wedged pulmonary artery pressures monitor the left heart but may be misleading if taken alone. Central venous pressure gives a delayed response to fluid overload.

Aged↗
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↗
PubMed2005

The BpTRU automatic blood pressure monitor compared to 24 hour ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension.

BACKGROUND: Increasing evidence suggests that ABPM more closely predicts target organ damage than does clinic measurement. Future guidelines may suggest ABPM as routine in the diagnosis and monitoring of hypertension. This would create difficulties as this test is expensive and often difficult to obtain. The purpose of this study is to determine the degree to which the BpTRU automatic blood pressure monitor predicts results on 24 hour ambulatory blood pressure monitoring (ABPM). METHODS: A quantitative analysis comparing blood pressure measured by the BpTRU device with the mean daytime blood pressure on 24 hour ABPM. The study was conducted by the Centre for Studies in Primary Care, Queen's University, Kingston, Ontario, Canada on adult primary care patients who are enrolled in two randomized controlled trials on hypertension. The main outcomes were the mean of the blood pressures measured at the three most recent office visits, the initial measurement on the BpTRU-100, the mean of the five measurements on the BpTRU monitor, and the daytime average on 24 hour ABPM. RESULTS: The group mean of the three charted clinic measured blood pressures (150.8 (SD10.26) / 82.9 (SD 8.44)) was not statistically different from the group mean of the initial reading on BpTRU (150.0 (SD21.33) / 83.3 (SD12.00)). The group mean of the average of five BpTRU readings (140.0 (SD17.71) / 79.8 (SD 10.46)) was not statistically different from the 24 hour daytime mean on ABPM (141.5 (SD 13.25) / 79.7 (SD 7.79)). Within patients, BpTRU average correlated significantly better with daytime ambulatory pressure than did clinic averages (BpTRU r = 0.571, clinic r = 0.145). Based on assessment of sensitivity and specificity at different cut-points, it is suggested that the initial treatment target using the BpTRU be set at <135/85 mmHG, but achievement of target should be confirmed using 24 hour ABPM. CONCLUSION: The BpTRU average better predicts ABPM than does the average of the blood pressures recorded on the patient chart from the three most recent visits. The BpTRU automatic clinic blood pressure monitor should be used as an adjunct to ABPM to effectively diagnose and monitor hypertension.

Adult↗
PubMed1985

Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 2: The relation between actual hydrostatic pressure, intrapelvic volume and time.

In a series of experiments with pigs the completely obstructed renal pelvis was infused with Ringer's lactate at a constant rate of 2 ml/min. At various pressure levels (lower than 50 mm Hg) the relations pressure vs infused volume and pressure vs actual intrapelvic volume and the effects on the intrapelvic pressure of rapid total or partial extraction of the actual volume were measured. At pressure levels lower than 15-20 mm Hg the P-V relation is exponential; at pressure levels between approximately 20 to 50 mm Hg this relation is linear. In the pressure range from 20 to 50 mm Hg the pressure decays, at a constant or increasing volume, asymptotically to a certain stabilisation value when the infusion is stopped. The relation between stabilised pressure and intrapelvic volume is linear.

Animals↗
PubMed1981

Treatment of acute low pressure pulmonary edema in dogs: relative effects of hydrostatic and oncotic pressure, nitroprusside, and positive end-expiratory pressure.

Severe pulmonary edema sometimes develops despite normal pulmonary capillary wedge pressure (Ppw). The equation describing net transvascular flux of lung liquid predicts decreased edema when hydrostatic pressure is reduced or when colloid osmotic pressure is increased in the pulmonary vessels. We tested these predictions in a model of pulmonary capillary leak produced in 35 dogs by intravenous oleic acid. 1 h later, the dogs were divided into five equal groups and treated for 4 h in different ways: (a) not treated, to serve as the control group (Ppw = 11.1 mm Hg); (b) given albumin to increase colloid osmotic pressure by 5 mm Hg (Ppw = 10.6 mm Hg); (c) ventilated with 10 cm H(2)O positive end-expiratory pressure (Peep) (transmural Ppw = 10.4 mm Hg); (d) phlebotomized to reduce Ppw to 6 mm Hg; (e) infused with nitroprusside, which also reduced Ppw to 6 mm Hg. Phlebotomy and nitroprusside reduced the edema in excised lungs by 50% (P< 0.001), but Peep and albumin did not affect the edema. Pulmonary shunt decreased on Peep and increased on nitroprusside, and lung compliance was not different among the treatment groups, demonstrating that these variables are poor indicators of changes in edema. Cardiac output decreased during the treatment period in all but the nitroprusside group, where Ppw decreased and cardiac output did not. We conclude that canine oleic acid pulmonary edema is reduced by small reductions in hydrostatic pressure, but not by increased colloid osmotic pressure, because the vascular permeability to liquid and protein is increased. These results suggest that low pressure pulmonary edema may be reduced by seeking the lowest Ppw consistent with adequate cardiac output enhanced by vasoactive agents like nitroprusside. Further, colloid infusions and Peep are not helpful in reducing edema, so they may be used in the lowest amount that provides adequate circulating volume and arterial O(2) saturation on nontoxic inspired O(2). Until these therapeutic principles receive adequate clinical trial, they provide a rationale for carefully monitored cardiovascular manipulation in treating patients with pulmonary capillary leak.

Albumins↗
PubMed1985

Behavior of an extradural pressure monitor in clinical use. Comparison of extradural with intraventricular pressure in patients with acute and chronically raised intracranial pressure.

A comparison of intraventricular pressure (IVP) and extradural pressure (EDP) was carried out in 17 patients being investigated for normal-pressure hydrocephalus, and in six patients with acutely raised intracranial pressure following events such as head injury or intracerebral hematoma. Extradural pressure was measured using the CardioSearch monitor. There was a reasonably good correlation between EDP and IVP in the chronic stable group with pressures up to 25 mm Hg. In the acute group there was no predictable relationship between EDP and IVP, and during a 24-hour period the pressures could vary by as much as 30 mm Hg. Subdural pressure, measured with the same instruments, was compared to IVP in both acute and stable situations in eight other patients: there was a close and constant correlation between pressures in these two spaces. The authors conclude that misleading information may be obtained from EDP monitoring, and erroneous management decisions may result from dependence on such a technique. Possible explanations for this are discussed.

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↗
PubMed1982

Noninvasive estimation of central aortic pressure using the oscillometric method for analyzing systemic artery pulsatile blood flow: comparative study of indirect systolic, diastolic, and mean brachial artery pressure with simultaneous direct ascending aortic pressure measurements.

Brachial artery pressures determined by the oscillometric method were compared with simultaneous central aortic (Ao) pressure measurements in 30 patients undergoing cardiac catheterization. Three simultaneous oscillometric and central Ao pressure readings were obtained in each patient. Central Ao pressures ranged widely for systolic (SP) (98 to 177 mm Hg), diastolic (DP) (41 to 97 mm Hg), and mean (MP) (60 to 120 mm Hg) pressure values. The mean percent errors (pressure difference divided by central Ao pressure) and "within subject" standard deviation were 1% and 3% for SP, 2% and 4% for DP, and -3% and 7% for MP. The percent error in oscillometric SP and DP estimates was not significantly influenced by cardiac index, systemic vascular resistance, heart rate, body surface area, or left ventricular ejection fraction. The oscillometric method provides accurate, reproducible, and convenient estimates of central Ao SP and DP and may be particularly useful when indirect blood pressure measurements are required for the noninvasive assessment of left ventricular function in patients without aortic stenosis.

Adult↗
PubMed2001

Left ventricular mass relates to average systolic blood pressure, but not loss of circadian blood pressure in stable hemodialysis patients: an ambulatory 48-hour blood pressure study.

Although left ventricular hypertrophy (LVH) is a common complication which contributes substantially to high cardiovascular mortality and morbidity in end-stage renal failure, whether changes in blood pressure and alterations of circadian variation of blood pressure occur between the hemodialysis (HD) day and the interdialytic day, and if so, whether they influence the left ventricular mass (LVM) remain unknown. Thirty-five consecutive stable patients who had had a hematocrit value greater than 25% for the previous 6 months, who had been on the same antihypertensive drugs during this period, and who underwent HD 3 times a week were included. Echocardiograms were recorded after HD and then ambulatory blood pressure monitoring was recorded every hour for 48 h. The mean interdialytic body weight gain was less than 5% of dry weight. Patients with LVH had a higher average systolic blood pressure (SBP) at predialysis, postdialysis, on the HD day and on the interdialytic day than those without LVH despite the higher antihypertensive therapy rate. The majority of patients with LVH showed concentric hypertrophy and higher plasma natriuretic peptide levels. Irrespective of the presence of LVH, the average blood pressure value did not change between the HD day and the interdialytic day, and a loss of circadian blood pressure variation was observed on both the HD and interdialytic days. Univariate analysis revealed that LVM was significantly correlated with the average SBP at predialysis, postdialysis, on the HD day, on the interdialytic day and over 48 h (r= 0.48, r=0.61, r=0.67, r=0.67, r=0.73, respectively; all p<0.05). Multiple regression analysis revealed that 48-h SBP was independently associated with the LVM index. These results suggest that neither the loss of circadian blood pressure variation nor the changes of blood pressure between the HD and interdialytic days was of major etiologic importance in the development of LVH, and that the absolute value of the 48-hour average SBP may be an important risk factor for concentric LVH in stable HD patients.

Adult↗
PubMed2002

Comparison of high pressure-induced dissociation of single-stranded DNA-binding protein (SSB) from high pressure-sensitive and high pressure-adapted marine Shewanella species.

The effects of hydrostatic pressure on protein quaternary structure were compared for recombinant single-stranded DNA-binding protein (SSB) derived from piezosensitive, piezotolerant, and obligately piezophilic ("pressure-loving") marine Shewanella strains. The pressure-induced dissociation of the oligomeric SSB proteins was investigated using fluorescence anisotropy. The SSBs all exhibited striking similarity in the pressure-dependent behavior of the fluorescence intensity and emission spectrum as well as in their dissociation constants at atmospheric pressure. The free energies of subunit association into tetramers for all SSBs were between -27 and -30 kcal mol(-1). However, SSB from the piezosensitive Shewanella strain S. hanedai was more sensitive to pressure than that of the SSB proteins from the piezotolerant or piezophilic bacteria. The volume change of association obtained from the pressure dependence of dissociation at a fixed protein concentration (Delta V(p)) for SSB from S. hanedai was 394-402 ml mol(-1). The Delta V(p) values for SSB from the deeper-living Shewanellas were smaller and ranged from 253 to 307 ml mol(-1). Differences between the primary structures of the SSB proteins that could correlate with differences in sensitivity to pressure-induced dissociation were examined.

Adaptation, Physiological↗
PubMed2001

Analysis of left ventricular systolic function during elevated external cardiac pressures: an examination of measured transmural left ventricular pressure during pressure-volume analysis.

BACKGROUND: Variations or disturbances in intrathoracic and extracardiac pressures (ECP) occur in critically ill and anaesthetised patients. There are uncertainties concerning the analysis of left ventricular pressure-volume relationship (LVPVR) and the calculation of systolic function parameters when conducted without reference to transmural left ventricular pressure (LVPtm) in the setting of elevated ECP. METHODS: In 7 anaesthetised adult pigs, we measured LVPVR using conductance volumetry and tip manometry along with measurement of pericardial and other intrathoracic pressures. Experimental pericardial infusion and pleural insufflation were performed. Transient controlled preload reductions were accomplished using balloon occlusion of the inferior vena cava. Preload recruitable stroke work (PRSW) was calculated using both intracavitary left ventricular pressure (LVPic) and LVPtm, and differences were tested for using a paired t-test. RESULTS: The pericardial and pleural interventions produced significant elevations in ECP. No difference in PRSW calculated using LVPic and LVPtm was detected. CONCLUSION: These results suggest that LVPtm need not be measured and included in LVPVR analysis of systolic function when there is significant external cardiac pressure. To be able to employ LVPVR analysis of systolic function without reference to LVPtm is important for simplified application in the clinical setting, particularly when elevated extracardiac pressures are suspected, or have been therapeutically induced, as with continuous positive pressure ventilation.

Anesthesia↗
PubMed1984

The use of left ventricular end-ejection pressure and peak pressure in the estimation of the end-systolic pressure-volume relationship.

The end-systolic pressure-volume relationship (ESPVR) as derived from left ventricular pressure-volume loops has gained increasing acceptance as an index of ventricular contractile function. In animal experiments the ESPVR has been defined as a line connecting the upper left corners of several differently loaded pressure-volume (P-V) loops with a slope parameter Ees and a volume axis intercept parameter Vo. In the clinical setting, several variants of the ESPVR have been determined with use of peak left ventricular pressure, end-ejection pressure, and end-ejection volume. The maximum P-V ratio has also frequently been measured. We attempted to determine which of these alternatives resulted in good approximations of the reference ESPVR in eight isolated canine ventricles that ejected into a simulated arterial impedance system with resistance, compliance, and characteristic impedance. We determined various versions of the ESPVR from the same set of beats quickly obtained with little change in inotropic background. To vary ventricular pressure wave forms, each of the arterial impedance parameters was independently controlled at 50%, 100%, and 200% of normal. Against each of the nine combinations of the impedance parameters four P-V loops were obtained under four preloads and from each of the sets of four P-V loops, the reference ESPVR, linear regression of the peak pressure on end-ejection volume (ESPVRPP-EEV), and linear regression of end-ejection pressure on end-ejection volume (ESPVREEPV) were determined. In addition, the maximum P-V ratio (MPVR) was calculated for each P-V loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Reproducibility of twitch mouth pressure, sniff nasal inspiratory pressure, and maximal inspiratory pressure.

Twitch mouth pressure (Pmo,tw) during magnetic phrenic nerve stimulation and sniff nasal inspiratory pressure (SNIP) were recently proposed as alternative noninvasive methods for assessing inspiratory muscle strength. This study aimed to compare their reproducibility with maximal inspiratory pressure (MIP) in normal subjects. Ten healthy subjects were studied at functional residual capacity in semirecumbent position. Cervical magnetic phrenic nerve stimulation was performed during gentle expiration against an occlusion incorporating a small leak. Constancy of stimulation was controlled by recording diaphragmatic electromyogram. Within and between-session reproducibility of pressure were studied for Pmo,tw, SNIP, and MIP. The subjects were studied during a session of 10 manoeuvres repeated after 1 day and 1 month. The mean values were 16 cmH2O for Pmo,tw, 118 cmH2O for SNIP, and 115 cmH2O for MIP. For the three tests, the within subject variation was small in relation to between-subject variation, with the intraclass correlation coefficient ranging 0.79-0.90 for Pmo,tw, 0.85-0.92 for SNIP, and 0.88-0.92 for MIP. At 1 day interval, the coefficient of repeatability (2 SD of differences) was 3.6 cmH2O for Pmo,tw, 32 cmH2O for SNIP and 28 cmH2O for MIP. At 1 month interval, the coefficient of repeatability was 5.8 cmH2O for Pmo,tw, 23 cmH2O for SNIP and 21 cmH2O for MIP. We conclude that the within session reproducibility of the new tests twitch mouth pressure and sniff nasal inspiratory pressure is sufficient to be clinically useful. For sniff nasal inspiratory pressure, the between session reproducibility established after 1 day was maintained after 1 month. For twitch mouth pressure, the between session reproducibility declined slightly after 1 month. These characteristics should be considered when using these methods to follow an individual patient over time.

Adult↗
PubMed1986

The interrelationship between intraocular pressure and Honan Intraocular Pressure Reducer pressure.

The relationship between the pressure applied to the enucleated human eye using the Honan Intraocular Pressure Reducer (HIPR) and the peak intraocular pressure as a function of initial intraocular pressure has been examined. The peak intraocular pressure is linearly related to the applied HIPR pressure whether the latter is 30, 50, or 75 mm Hg. The slopes relating peak intraocular pressure to initial intraocular pressure at different HIPR settings are parallel. Use of the HIPR at settings greater than 30 mm Hg and an initial IOP of greater than 30 mm Hg could compromise ocular vascular perfusion.

Humans↗
PubMed1996

Predictive power of screening blood pressure, ambulatory blood pressure and blood pressure measured at home for overall and cardiovascular mortality: a prospective observation in a cohort from Ohasama, northern Japan.

OBJECTIVE: To investigate the risks of high and low blood pressure levels determined by ambulatory blood pressure monitoring and home blood pressure measurements. METHODS: A long-term prospective study of all-cause mortality and cardiovascular mortality has been conducted in Ohasama, Japan since 1987. RESULTS: The Cox proportional hazards model after adjusting for age and sex demonstrated that, during a 5-year follow-up period involving 893 of the subjects aged 50 years or more in this cohort, those with the lowest quintile of ambulatory blood pressure levels exhibited a significantly higher hazard ratio for cardiovascular and for all-cause mortality. During the same follow-up period, of 1226 subjects aged 50 years and more, those with the lowest and highest quintiles of home blood pressure levels demonstrated a significantly higher hazard ratio with respect to cardiovascular and all-cause mortality (i.e., a J-shaped relationship). CONCLUSION: These results suggest that there is a significant risk associated with low blood pressure levels, which can be determined by ambulatory and home blood pressure measurements, but not by casual blood pressure measurements.

Journal Article↗