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PubMed1996

Positive end-expiratory pressure-induced hemodynamic changes are reflected in the arterial pressure waveform.

OBJECTIVE: To examine whether the hemodynamic changes due to mechanical ventilation with positive end-expiratory pressure (PEEP) can be assessed by the respiratory-induced variations in the arterial pressure waveform during normovolemia and experimental acute ventricular failure. DESIGN: Prospective, controlled experimental study. SETTING: Institutional experimental laboratory. SUBJECTS: Adult mongrel dogs. INTERVENTIONS: Experimental acute ventricular failure was induced by the infusion of pentobarbital (a cardiodepressant) and methoxamine (a vasoconstrictor), combined with volume loading. Both the control and acute ventricular failure groups were subjected to ventilation with incremental levels of PEEP up to 20 cm H2O. MEASUREMENTS AND MAIN RESULTS: Cardiac function was evaluated by cardiac output and left and right ventricular change in pressure over time (dP/dt) measurements. Arterial pressure waveform analysis was performed by measuring the systolic pressure variation, which is the difference between the maximal and minimal systolic blood pressure values during one mechanical breath. The components of the systolic pressure variation, namely, dUp and dDown, which are the increase and decrease in the systolic pressure during the mechanical breath relative to the systolic pressure during apnea, were also measured at each PEEP level. PEEP caused significant reduction of cardiac output in normovolemic dogs, and was associated with significant increases in systolic pressure variation and dDown. Acute ventricular failure decreased the variations in the systolic pressure and caused the dDown component to disappear. The application of PEEP did not affect cardiac output in dogs with acute ventricular failure, nor did it change systolic pressure variation and the dDown. CONCLUSIONS: Analysis of arterial pressure waveforms during mechanical ventilation reflected the decrease in cardiac output in dogs with normal cardiac function subjected to incremental PEEP. In dogs with acute ventricular failure in which PEEP did not affect cardiac output, the systolic pressure variation was similarly unaffected by PEEP. In the absence of cardiac output measurement during mechanical ventilation with PEEP, the analysis of the respiratory variations in the arterial pressure waveform may be useful in assessing changes in cardiac output.

Animals↗

PubMed1998

Effects of continuous negative extrathoracic pressure versus positive end-expiratory pressure in acute lung injury patients.

OBJECTIVE: To compare the effects of continuous negative extrathoracic pressure (CNEP) and positive end-expiratory pressure (PEEP) at the same level of transpulmonary pressure. DESIGN: Prospective analysis. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Nine consecutive acute lung injury patients. Patients with cardiac failure and patients with chronic lung disease were excluded from the investigation. INTERVENTIONS: The patients were sedated and paralyzed while receiving mechanical ventilation and were studied in three different conditions: a) using a PEEP of 0 cm H2O (zero end-expiratory pressure); b) using a PEEP of 15 cm H2O; c) using CNEP. CNEP was applied to the thorax and the upper abdomen and its level was chosen to obtain a transpulmonary pressure similar to the one observed at a PEEP of 15 cm H2O. All patients had an arterial catheter, a pulmonary artery catheter, and a thermistor-tip fiberoptic catheter for thermo-dye-dilution in the femoral artery. These catheters were connected to an integrated monitoring system. We also placed an esophageal catheter in each patient to detect esophageal pressure. MEASUREMENTS AND MAIN RESULTS: For each step, we assessed the hemodynamic variations by measuring intravascular pressures (via a pulmonary artery catheter), transmural pressures (computed by subtracting esophageal pressure from intravascular pressure), and blood volumes (derived from the technique of double indicator). The application of CNEP of -20+/-0.7 cm H2O produced a venous admixture and PaO2/FO2 improvement similar to that obtained with a PEEP of 15 cm H2O. This procedure is associated with a higher cardiac index (5.5+/-1.5 vs. 4.6+/-1.2 L/min/m2; p < .05) coupled with lower central venous pressure, pulmonary artery occlusion pressure, and higher transmural pressures and blood volume parameters. CONCLUSIONS: In acute lung injury patients, a CNEP of -20 cm H2O has the capability to obtain transpulmonary pressure and lung function improvement similar to a PEEP of 15 cm H2O. CNEP differs from the positive pressure by increasing the venous return and the preload of the heart, and has no negative effects on cardiac performance.

APACHE↗

PubMed2002

Tracheal pressure control provides automatic and variable inspiratory pressure assist to decrease the imposed resistive work of breathing.

OBJECTIVE: To evaluate the operation of a continuous positive airway pressure system by using tracheal airway pressure (PT) as the control signal for system operation (i.e., tracheal pressure control). DESIGN: Repeated measures. SETTING: University research laboratory. SUBJECTS: Twelve anesthetized, spontaneously breathing swine. INTERVENTIONS: Subjects were intubated and connected to a tracheal pressure control system (5 cm H2O continuous positive airway pressure). Varying inspiratory flow demands and degrees of partial endotracheal tube occlusion (25%, 50%, and 75%) were studied. Tracheal pressure control was compared with a conventionally controlled system (pressure from breathing circuit Y-piece [PY] used as control signal) during endotracheal tube occlusion. MEASUREMENTS AND RESULTS: Imposed resistive work of breathing (work to spontaneously inhale through endotracheal tube and ventilator circuit), work by ventilation system assisting inhalation, PT, PY, tidal volume, and inspiratory flow demands were measured. As inspiratory flow demands increased (range, 0.2-2.3 L/sec), pressure assist increased automatically (range, 5-40 cm H2O) as well as work of breathing by ventilation system assisting inhalation (range, 0.2-2.5 J/L). Imposed resistive work of breathing was nullified at the lower and was negligible at the higher flow demands. During endotracheal tube occlusion with a conventionally controlled system, PY was unchanged, whereas PT decreased (up to -15 cm H2O) and imposed resistive work of breathing increased (up to 1.05 J/L). With tracheal pressure control, PY increased automatically (range, 8-52 cm H2O), whereas PT varied slightly (range, 2 to -4.6 cm H2O). Imposed resistive work of breathing was negligible (range, 0-0.2 J/L). Breathing circuit pressure (PY), not pulmonary airway pressure (PT), increased significantly during tracheal pressure control. CONCLUSIONS: Tracheal pressure control results in automatic and variable levels of pressure assist to decrease imposed resistive work of breathing under conditions of varying spontaneous inspiratory flow demands and endotracheal tube occlusion. Conventional systems are potentially flawed when PY is used as the control signal because they do not function in this manner and do not accurately assess pulmonary airway pressure.

Animals↗

PubMed2004

Pulmonary artery occlusion pressure and central venous pressure fail to predict ventricular filling volume, cardiac performance, or the response to volume infusion in normal subjects.

OBJECTIVE: Pulmonary artery occlusion pressure and central venous pressure have been considered to be reliable measures of left and right ventricular preload in patients requiring invasive hemodynamic monitoring. Studies in recent years have questioned the correlation between these estimates of ventricular filling pressures and ventricular end-diastolic volumes/cardiac performance variables in specific patient groups, but clinicians have continued to consider the relationship valid in the broader context. The objective of this study was to assess the relationship between pressure estimates of ventricular preload (pulmonary artery occlusion pressure, central venous pressure) and end-diastolic ventricular volumes/cardiac performance in healthy volunteers. DESIGN: Prospective, nonrandomized, nonblinded interventional study. SETTING: Cardiac catheterization and echocardiography laboratories. SUBJECTS: Normal healthy volunteers (n = 12 group 1, n = 32 group 2). INTERVENTIONS: Pulmonary catheterization and radionuclide cineangiography (group 1) and volumetric echocardiography (group 2) during 3 L of normal saline infusion over 3 hrs. MEASUREMENTS AND MAIN RESULTS: In group 1, the initial pulmonary artery occlusion pressure and central venous pressure did not correlate significantly with initial end-diastolic ventricular volume indexes or cardiac performance (cardiac index and stroke volume index). Changes in pulmonary artery occlusion pressure and central venous pressure following saline infusion also did not correlate with changes in end-diastolic ventricular volume indexes or cardiac performance. In contrast, initial end-diastolic ventricular volume indexes and changes in these ventricular volume indexes in response to 3 L of normal saline loading correlated well with initial stroke volume index and changes in stroke volume index, respectively. The relationship between left ventricular end-diastolic volume index and stroke volume index was confirmed in group 2 subjects using mathematically independent techniques to measure these variables. In addition, initial central venous pressure, right ventricular end-diastolic volume index, pulmonary artery occlusion pressure, and left ventricular end-diastolic volume index failed to correlate significantly with changes in cardiac performance in response to saline infusion in group 1 subjects. CONCLUSIONS: Normal healthy volunteers demonstrate a lack of correlation between initial central venous pressure/pulmonary artery occlusion pressure and both end-diastolic ventricular volume indexes and stroke volume index. Similar results are found with respect to changes in these variables following volume infusion. In contrast, initial end-diastolic ventricular volume indexes and changes in end-diastolic ventricular volume indexes in response to saline loading correlate strongly with initial and postsaline loading changes in cardiac performance as measured by stroke volume index. These data suggest that the lack of correlation of these variables in specific patient groups described in other studies represents a more universal phenomenon that includes normal subjects. Neither central venous pressure nor pulmonary artery occlusion pressure appears to be a useful predictor of ventricular preload with respect to optimizing cardiac performance.

Adolescent↗

PubMed2006

Introversion associated with large differences between screening blood pressure and home blood pressure measurement: The Ohasama study.

OBJECTIVE: To explore the effect of personality on screening blood pressures measured in clinical settings and home blood pressure measurements. METHODS: From 1997 to 1999, 699 participants underwent screening and home blood pressure measurements and completed the Japanese version of the short-form Eysenck personality questionnaire. An increased screening blood pressure was defined as screening blood pressure > or = 140/90 mmHg and an increased home blood pressure was defined as home blood pressure > or = 135/85 mmHg. RESULTS: Participants with lower extroversion scores (i.e., introversion) showed a greater difference between screening and home systolic blood pressure. The association between introversion and differences was statistically significant, even after adjustment for other possible factors (younger age, female, wide screening pulse pressure, never smoked, and no antihypertensive medication). The adjusted means of SBP differences were 7.3 and 4.4 mmHg among the lowest and highest extroversion quartiles, respectively (P for trend = 0.02). Other personality scores (psychoticism or neuroticism) were not associated with screening and home blood pressure differences. The incorporation of an extroversion score in the basic model consisting of the above factors that affected the difference between screening and home blood pressure slightly improved the prediction of a high home blood pressure. The area under the receiver operating characteristic curve increased by 0.037 among participants with high screening blood pressure and 0.006 for those with normal screening blood pressure compared with the basic model. CONCLUSION: Physicians may need to be aware of 'introverted' patients who have high blood pressure in clinic settings, because they have the potential for 'white-coat' hypertension.

Aged↗

PubMed2001

Pressure amplification explains why pulse pressure is unrelated to risk in young subjects.

Pulse pressure rather than diastolic pressure is the best predictor of coronary heart disease risk in older subjects, but the converse is true in younger subjects. We hypothesized that this disparity results from an age-related difference in pressure amplification from the aorta to brachial artery. Data from 212 subjects age < 50 years and 230 subjects age > or =50 years were abstracted from a community database. All subjects were free from cardiovascular disease, diabetes, and medication. Peripheral blood pressure was assessed by sphygmomanometry. Radial artery waveforms recorded noninvasively by applanation tonometry were used to derive central blood pressure. Pressure amplification (peripheral/central pulse pressure ratio) was linearly related to age (r=0.7; P<0.001). There was an inverse, linear relationship between amplification and diastolic pressure in the younger group (r=0.3; P<0.001) but not in older subjects (r=0.1; P=0.2). There was no relationship in either group when the amplification ratio was calculated with nonaugmented central pressure. Amplification is reduced in older subjects because of enhanced wave reflection. In younger, but not older, subjects, amplification declines as diastolic pressure rises. Therefore, peripheral pulse pressure underestimates the effect that diastolic pressure has on central pulse pressure in younger subjects. This may explain why diastolic pressure is a better predictor of risk in this age group and suggests that assessment of central pressure may improve risk stratification further.

Adult↗

PubMed1980

Variability of hydrostatic hepatic vein and ascitic fluid pressure, and of plasma and ascitic fluid colloid osmotic pressure in patients with liver cirrhosis.

The variability of hydrostatic hepatic vein and ascitic fluid pressures and of plasma and ascitic fluid colloid osmotic (oncotic) pressures was assessed during hepatic venous catheterization by repeated measurements on different days and at different locations in patients with cirrhosis of the liver. Furthermore, calculation of oncotic pressure from protein determinations was compared to the directly measured value of plasma and ascitic fluid samples. Repeated measurements of hydrostatic pressure in the same hepatic vein within 15 min showed a standard deviation (SD) below 1 mmHg. The variation in hydrostatic hepatic vein pressures, pressure differences and ascitic fluid pressures (when measured at different locations within the liver and peritoneal space during a single examination) was 1.5, 1.0 and 1.0 mmHg (SD), respectively. When measured on different days, the variation of hydrostatic hepatic vein pressures, pressure differences and ascitic fluid pressures was 2.5, 1.6 and 1.3 mmHg (SD), respectively. Repeated measurements of oncotic pressure on the same plasma sample varied 0.3 and 0.6 mmHg (SD) when measured on the same day and a subsequent day, respectively. The variation in plasma and ascitic fluid oncotic pressure, when measured on samples obtained on different days, was 2.0 and 0.6 mmHg, respectively. The error of oncotic pressure calculated from protein determinations was 2.9 and 1.3 mmHg (SD) for plasma and ascitic fluid, respectively. It is concluded that measurements during catheterization give a good reproducibility in determination of the hydrostatic pressures in hepatic vein and ascitic fluid and of the colloid osmotic (oncotic) pressure in plasma and ascitic fluid in the resting supine patient with cirrhosis, which substantiates the use of measurements during a short period as representative for the patients long-time level.

Ascitic Fluid↗

PubMed1999

Measurements of blood pressure with various techniques in daily practice: uncertainty in diagnosing office hypertension with short-term in-hospital registration of blood pressure.

OBJECTIVE: To predict blood pressure outside the clinic from a short-term in-hospital registration for patients referred for ambulatory blood pressure monitoring (ABPM) with special attention to office hypertension. PATIENTS AND METHODS: A series of measurements of blood pressure was performed by the same technician for 187 patients, 82% of whom were being administered antihypertensive therapy. She performed three mercury measurements of blood pressure (Hg stress 1) and then three manually started measurements with a semi-automatic device (Dinamap 1846SX; Dinamap stress) alternated with three manually started readings with a SpaceLabs 90207 monitor (SpaceLabs stress) on the contralateral non-dominant arm. The in-hospital session was continued with 15 automatic Dinamap registrations at 2 min intervals without the technician being present (Dinamap unstressed, five periods of three measurements averaged) before the patient left the hospital for 24h ABPM. RESULTS: The percentages of patients with hypertension in the office (systolic blood pressure >/= 140 mmHg or diastolic blood pressure >/= 90 mmHg, or both) were 80% with Hg stress 1, 76% with Dinamap stress and 85.0% with SpaceLabs stress. Average diastolic SpaceLabs stress was 6.0+/-5.6 mmHg (significantly) higher than diastolic Dinamap stress, whereas the difference between systolic blood pressures was 0.2+/-10.0 mmHg. No further change in blood pressure occurred after the fourth period of Dinamap unstressed measurements. Office hypertension defined as SpaceLabs stress systolic blood pressure >/= 140 mmHg or diastolic blood pressure >/= 90 mmHg, or both, and SpaceLabs daytime systolic blood pressure < 135 mmHg and diastolic blood pressure < 85 mmHg was found in 21 individuals. Office hypertension defined with similar cut-off points in the comparison of Dinamap stress versus Dinamap unstressed period 5 was found in 29 cases, 10 of which overlapped with the definition SpaceLabs stress versus SpaceLabs daytime. The differences between Dinamap stress and Dinamap unstressed period 5 were significantly correlated to the changes of SpaceLabs stress and SpaceLabs daytime both for systolic (r =0.41) and for diastolic (r =0.32) blood pressures. CONCLUSIONS: Measurements of blood pressure in the office with various techniques (mercury, Dinamap and SpaceLabs) are not equivalent. Office hypertension cannot be reliably predicted from a short-term semi-automatic in-hospital registration of blood pressure with a Dinamap device.

Adolescent↗

PubMed1996

Effect of nocturnal blood pressure measurement on sleep and blood pressure during sleep.

Nocturnal hypertension is of diagnostic interest and has important prognostic and therapeutic implications. Nighttime blood pressure can easily be measured using ambulatory blood pressure monitoring (ABPM). However, during nocturnal ambulatory blood pressure measurement pump noise, tactile stimuli and pressure produced by cuff inflation may alter the quality of sleep and subsequently influence the physiological fall of night time blood pressure. Eight studies were performed to determine whether non-invasive automated blood pressure monitoring during day and/or night provokes alert reaction, arousal, sleep disturbances and changes in blood pressure and/or heart rate. From these studies it can be concluded: 1) Nighttime blood pressure can be evaluated properly using ABPM. 2) Nocturnal blood pressure is not overestimated by ABPM. 3) ABPM does not induce an alarm reaction and a blood pressure rise when monitored with a silently operating recorder. 4) Sleep is often disturbed by blood pressure measurement without provoking a blood pressure increase. 5) In older patients blood pressure measurement and age-related alterations in sleep quality may influence each other. A patient's protocol has to be carried out and sleep quality should be recorded to provide a proper interpretation of nocturnal blood pressure behavior. ABPM is an important and valuable method to record nocturnal blood pressure for diagnostic and therapeutic purposes.

Arousal↗

PubMed2001

Impact of diet on blood pressure and age-related changes in blood pressure in the US population: analysis of NHANES III.

BACKGROUND: The impact of diet on blood pressure and the age-related changes in blood pressure have been difficult to detect within one population. We designed this analysis to study the association of major dietary factors with blood pressure and with age-related changes in blood pressure in a representative sample of the US population. METHODS: Data were obtained on all individuals 20 years or older (n = 17 030) surveyed in the Third National Health and Nutrition Examination Survey (NHANES III), including demographic data, anthropometric data, dietary intake (sodium, potassium, calcium, magnesium, protein, alcohol, and total energy) based on 24-hour recall, and blood pressure. Multivariate models relating diet to blood pressure were constructed using stepwise regression, best subset regression, and multiple regression. RESULTS: Systolic blood pressure was positively associated with higher sodium, alcohol, and protein intakes (P<.05) and negatively associated with potassium intake (P =.003). Diastolic blood pressure was negatively associated with potassium and alcohol intakes (P<.001). Pulse pressure was positively associated with sodium, protein, and alcohol intakes (P<.001). A higher intake of calcium (P =.01) was associated with a lower rate of rise in systolic blood pressure with age. CONCLUSION: A diet low in sodium, alcohol, and protein is associated with lower systolic blood and pulse pressure. Potassium intake was associated with lower systolic and diastolic blood pressure, whereas alcohol intake was associated with lower diastolic blood pressure. In addition, the age-related changes in systolic blood pressure were attenuated by higher calcium and protein intakes. Magnesium was not associated with any changes in blood pressure.

Aging↗

PubMed2000

Terlipressin is more effective in decreasing variceal pressure than portal pressure in cirrhotic patients.

BACKGROUND/AIMS: Terlipressin decreases portal pressure. However, its effects on variceal pressure have been poorly investigated. This study investigated the variceal, splanchnic and systemic hemodynamic effects of terlipressin. METHODS: Twenty cirrhotic patients with esophageal varices grade II-III, and portal pressure > or =12 mmHg were studied. Hepatic venous pressure gradient, variceal pressure and systemic hemodynamic parameters were obtained. After baseline measurements, in a double-blind administration, 14 patients received a 2mg/iv injection of terlipressin and six patients received placebo. The same measurements were repeated 60 min later. RESULTS: No demographic or biochemical differences were observed in basal condition between groups. Terlipressin produced significant decreases in intravariceal pressure from 20.9+4.9 to 16.3+/-4.7 mmHg (p<0.01, -21+/- 16%), variceal pressure gradient from 18.9+/-4.8 to 13.5+/-6.0 mmHg (p<0.01, -28+/-27%), estimated variceal wall tension from 78+/-29 to 59+/-31 mmHg x mm (p<0.01, -27+/-22%), and hepatic venous pressure gradient from 19.4+/-4.5 to 16.8+/-5 mmHg (p<0.01, -14+/-12%) at 60 min. The change in variceal pressure after 60 min of terlipressin administration was greater than the change in wedge hepatic venous pressure (-4.7 mmHg vs -0.5 mmHg, respectively, p<0.0001). Terlipressin also caused significant decreases in heart rate and cardiac index and increases in mean arterial pressure and peripheral vascular resistance. CONCLUSIONS: Our results demonstrate that terlipressin produces significant and prolonged decreases in variceal pressure and variceal wall tension and has intrinsic effects on portal pressure and systemic hemodynamics. Variceal pressure provides a better assessment of the effects of terlipressin administration on esophageal varices than hepatic venous pressure gradient.

Adolescent↗

PubMed1996

Effects of driving pressure and recurrent laryngeal nerve stimulation on glottic vibration in a constant pressure model.

Glottic phonatory parameters have been studied in constant flow models; however, the lung-thorax system is better viewed as a constant pressure source. Adjusting the driving pressure and recurrent laryngeal nerve stimulation as independent variables, rather than as dependent variables, may provide a more physiologic understanding of laryngeal function and glottic parameters, including subglottic pressure, airflow, fundamental frequency, and glottic area. In three dogs subglottic pressure and airflow were measured in two separate conditions: with constant recurrent laryngeal nerve stimulation and varying driving pressure, and with constant driving pressure and varying recurrent laryngeal nerve stimulation. Videostroboscopic measures on four dogs assessed glottic areas with constant recurrent laryngeal nerve stimulation at different driving pressures. With constant recurrent laryngeal nerve stimulation, increasing driving pressure had no effect on glottic areas, whereas subglottic pressure, fundamental frequency, and airflow increased significantly. However, changes in subglottic pressure were minimal in comparison with changes in driving pressure. At constant driving pressure, increasing recurrent laryngeal nerve stimulation increased subglottic pressure and fundamental frequency and decreased airflow. These findings suggest that during phonation subglottic pressure is primarily dependent on recurrent laryngeal nerve stimulation and laryngeal muscular contraction, but not on lung driving pressure.

Analysis of Variance↗

PubMed2003

The pressure tunning Raman spectral studies of the bilirubinIXalpha and neutral calcium bilirubinate at high external pressure.

The bilirubinIXalpha and its neutral calcium bilirubinate were studied using Raman spectroscopy at high external pressure. The results showed that the bilirubinIXalpha has two pressure-induced phase transitions (15-18 and 30-36 kbar) and three pressure phase areas. Its pressure sensitivities in the low-pressure phase are very low. It is believed that the four internally hydrogen bonds in bilirubinIXalpha molecule cause the atoms to attract each other tightly in the bilirubinIXalpha molecule. Therefore, the low pressure is not strong enough to shorten the bonds significantly. The pressure sensitivities in the middle-pressure phase are much higher than those in the low-pressure phase, but those in the high-pressure phase are slightly lower than in the middle-pressure phase. There is only one pressure-induced phase transition (25-34 kbar) in the neutral calcium bilirubinate. The pressure sensitivities in the low-pressure phase are higher than those in the high-pressure phase as usually.

Bilirubin↗

PubMed1988

Postural changes in blood pressure and pulse rate among black adolescents and white adolescents: the Minneapolis Children's Blood Pressure Study.

Because studies have suggested a possible relation between vascular responsiveness to postural changes and risk of subsequent myocardial infarction, the reactivity of blood pressure and pulse rate to change from supine to standing positions was examined in 158 black males, 144 black females, 342 white males, and 272 white females aged 14-16 years. The study was part of the Minneapolis Children's Blood Pressure Study and was conducted during October to December 1985. Two blood pressure readings and one pulse reading were taken after five minutes of supine rest, immediately upon standing, and five minutes after standing. After adjustment for body mass index, mean systolic blood pressure decreased, and fourth- and fifth-phase diastolic blood pressures and pulse rate increased from supine to standing positions in all race and sex groups. Black males had significantly larger changes in systolic pressure than did white males (-5.9 vs. -4.1 mmHg), and males had significantly larger changes in fourth- and fifth-phase diastolic pressures compared with females of the same race (fourth-phase diastolic pressure, 8.0 vs. 4.1 mmHg for blacks and 10.0 vs. 4.8 mmHg for whites). Fifth-phase diastolic pressure increased more than did fourth-phase diastolic pressure in all groups. No race or sex differences were seen for pulse changes. For all race-sex groups, decreases in systolic pressure were positively correlated with initial levels of supine systolic pressure, whereas increases in fourth- and fifth-phase diastolic pressures were negatively correlated with corresponding initial levels. Measurement of postural changes may provide a clinically simple and reproducible way of testing for abnormalities in blood pressure and may better discriminate those at high risk of hypertension and its cardiovascular complications than would the commonly used single-seated blood pressure measurement.

Adolescent↗

PubMed1994

Evaluation of pressure transmission ratios in women with genuine stress incontinence and low urethral pressure: a comparative study.

OBJECTIVE: To determine whether women with genuine stress incontinence and low urethral closure pressure (20 cm H2O or lower) had more severely impaired pressure transmission to the urethra than women with stress incontinence and normal urethral pressures. METHODS: Seventy-six women who underwent multichannel urodynamic testing were included for comparative analysis. They were classified into the following groups: genuine stress incontinence with low urethral pressure (N = 20), genuine stress incontinence without low urethral pressure (N = 32), and continent controls (N = 24). Urodynamic indices and pressure transmission ratios were calculated from static and stress urethral pressure profiles, respectively. Multiple demographic cofactors, urethral mobility, and previous surgeries were correlated for associations with urodynamic results. RESULTS: Women with stress incontinence and low urethral pressure were significantly older (57.6 years, P < .0071). There were no differences with regard to urethral mobility and previous surgeries. Mean maximum urethral closure pressure and the distance from the proximal margin of the urethra to the point of maximum urethral closure pressure were statistically less in women with low urethral pressure. There were no differences in pressure transmission ratios between any of the study groups. CONCLUSION: Because there are no differences in pressure transmission ratios between women with genuine stress incontinence with and without low urethral closure pressure, the higher risk for surgical failure with low urethral pressure appears to result from another pathophysiologic process.

Female↗

PubMed2002

The effect of fundal pressure manoeuvre on intrauterine pressure in the second stage of labour.

OBJECTIVE: To investigate the relationship between intrauterine pressure and the application of a standardised fundal pressure manoeuvre, and to determine the maternal, fetal and labour characteristics that modulate the relationship. DESIGN: Prospective measurement of intrauterine pressure during the second stage of labour. SETTING: North American university hospital. POPULATION: Forty full-term women in spontaneous labour were studied during the second stage. Each woman acted as her own control. All women laboured with requested epidural analgesia. METHODS: A fundal pressure manoeuvre was performed so as to standardise the level of force and the surface area of application. Intrauterine pressure was measured using a sensor-tip catheter. Five interventions were analysed: 1. valsalva during a uterine contraction; 2. fundal pressure and valsalva during a contraction; 3. fundal pressure during a contraction without valsalva; 4. fundal pressure in the absence of uterine contractions; and 5. valsalva in the absence of uterine contractions. RESULTS: Women in the second stage of labour transiently increased their expulsive force (as reflected by intrauterine pressure) by 86% of their baseline contraction using valsalva and fundal pressure simultaneously. The efficiency by which both contraction-enhancing manoeuvres increased intrauterine pressure was directly related to gestational age and inversely related to myometrial thickness. CONCLUSION: Fundal pressure applied under controlled conditions significantly increases intrauterine pressure in some, but not all women. Simultaneous measurement of intrauterine pressure, to maintain feedback during application will create a 'controlled environment' for the obstetrician and reassurance that this manoeuvre can be applied in a controlled fashion. Future delineation of the group of women that could benefit from fundal pressure, as well as the group that is refractory is essential to avoid unnecessary or delayed operative interventions.

Adolescent↗

PubMed1993

Non-invasive estimates of aortic root pressures: external subclavian arterial pulse tracing calibrated by oscillometrically determined brachial arterial pressures.

This investigation assessed the ability of a non-invasive method to reproduce aortic root pressure waveform and pressures. An external pulse tracing of the subclavian artery was obtained simultaneously with direct aortic root pressures during routine left heart catheterization in 26 patients (aged 39-74 years) with various cardiovascular disorders. Indirect brachial arterial peak-systolic and nadir-diastolic pressures were obtained with oscillometry. The direct and indirect peak-systolic and nadir-diastolic pressures, were separately used to calibrate the pulse tracing. Adequate pulse tracing was obtained in 19 patients (73%). The waveforms agreed well with cross-correlation coefficients for systole and diastole of 0.98. The difference between the pulse trace and the direct pressure curve, when the first was calibrated with the peak-systolic and nadir-diastolic pressures of the latter on average was less than 1 mmHg for systole and diastole. At end-systole the mean difference was 5 mmHg. Oscillometric brachial arterial peak-systolic pressures were (mean +/- SD) 3 +/- 7 mmHg below the corresponding direct measurements, while diastolic pressures were 8 +/- 4 mmHg above. The difference between the pulse trace and the direct pressure curve, when the pulse trace was calibrated with oscillometric pressures, was at end-systole 6 +/- 6 mmHg and for mean arterial pressures 5 +/- 4 mmHg. Thus, the external subclavian arterial pulse tracing provides a non-invasive, clinically feasible access to the aortic root pressure waveform. With optimal calibration, good estimates of aortic root pressures throughout systole and diastole can be obtained, while end-systolic pressure tends to be slightly overestimated.

Adult↗

PubMed2006

Common cavity pressure during gastroesophageal reflux: reassessment using simultaneous pressure, impedance, and ultrasound imaging.

An increase in intraesophageal pressure during transient lower esophageal sphincter (LES) relaxation [referred to as common cavity (CC) pressure] is thought to be a marker of gastroesophageal reflux (GER). Multiluminal impedance (MII) measurement is a sensitive marker of reflux entry into the esophagus during GER. We recorded GER using esophageal pressure, pH, impedance, and intraluminal ultrasound (US) images to understand the genesis of the esophageal CC pressure. Nine normal subjects underwent simultaneous MII/pH/pressure and US image recording of the esophagus for 2 h following a standardized meal. MII and pressure transducers were located at 5 and 15 cm above the LES. The US transducer and pH sensors were also placed at 5 cm above the LES. Refluxate entry into the esophagus by MII criteria was determined relative to the onset of CC pressure wave. Esophageal lumen cross-sectional area (CSA) and muscle CSA during GER were determined from the US images. Eighty liquid GER episodes identified using MII criteria, of which 55 were clearly associated with CC pressure waves, were analyzed. The GER reached 15 cm above LES in 49 of 55 (89%) by MII criteria, but the CC pressure wave was observed at 5 and 15 cm during all episodes. The propagation of the CC pressure wave was simultaneous between 5 and 15 cm during 49 of 55 (89%) of the GER episodes, but reflux entry by MII criteria was retrograde during 53 of 55 (96%) of these episodes. During 5 air-reflux episodes, MII showed a simultaneous reflux entry between the 5- and 15-cm site, however, the CC pressure preceded reflux entry during all of these episodes. There was poor correlation between the luminal CSA and the magnitude of CC pressure (R(2) = 0.144). US images revealed a close temporal correlation between CC pressure and the increase in esophageal muscle thickness and muscle CSA (markers of longitudinal muscle contraction). Disassociation between CC pressure and MII-detected reflux suggests that the onset of CC pressure is not due to GER. We speculate that longitudinal muscle contraction plays an important role in the genesis of CC pressure.

Adolescent↗