Increasing abdominal pressure with and without PEEP: effects on intra-peritoneal, intra-organ and intra-vascular pressures

Intra-organ and intra-vascular pressures can be used to estimate intra-abdominal pressure. The aim of this prospective, interventional study was to assess the effect of PEEP on the accuracy of pressure estimation at different measurement sites in a model of increased abdominal pressure.

Systolic blood pressure below 110 mmHg is associated with increased mortality in penetrating major trauma patients: Multicentre cohort study

Non-invasive systolic blood pressure (SBP) measurement is a commonly used triaging tool for trauma patients. A SBP of <90mmHg has represented the threshold for hypotension for many years, but recent studies have suggested redefining hypotension at lower levels. We therefore examined the association between SBP and mortality in penetrating trauma patients.

Systolic blood pressure below 110 mm Hg is associated with increased mortality in blunt major trauma patients: multicentre cohort study

Non-invasive systolic blood pressure (SBP) measurement is often used in triaging trauma patients. Traditionally, SBP< 90 mm Hg has represented the threshold for hypotension, but recent studies have suggested redefining hypotension as SBP < 110 mm Hg. This study aims to examine the association of SBP with mortality in blunt trauma patients.

A modified calculation of ankle-brachial pressure index is far more sensitive in the detection of peripheral arterial disease

BACKGROUND: Ankle-brachial pressure index (ABI) is a simple, inexpensive, and useful tool in the detection of peripheral arterial occlusive disease (PAD). The current guidelines published by the American Heart Association define ABI as the quotient of the higher of the systolic blood pressures (SBPs) of the two ankle arteries of that limb (either the anterior tibial artery or the posterior tibial artery) and the higher of the two brachial SBPs of the upper limbs. We hypothesized that considering the lower of the two ankle arterial SBPs of a side as the numerator and the higher of the brachial SBPs as the denominator would increase its diagnostic yield. METHODS: The former method of eliciting ABI was termed as high ankle pressure (HAP) and the latter low ankle pressure (LAP). ABI was assessed in 216 subjects and calculated according to the HAP and the LAP method. ABI findings were confirmed by arterial duplex ultrasonography. A significant arterial stenosis was assumed if ABI was <0.9. RESULTS: LAP had a sensitivity of 0.89 and a specificity of 0.93. The HAP method had a sensitivity of 0.68 and a specificity of 0.99. McNemar's test to compare the results of both methods demonstrated a two-tailed P < .0001, indicating a highly significant difference between both measurement methods. CONCLUSIONS: LAP is the superior method of calculating ABI to identify PAD. This result is of great interest for epidemiologic studies applying ABI measurements to detect PAD and assessing patients' cardiovascular risk.

Ultrasound assessment of detrusor thickness in men-can it predict bladder outlet obstruction and replace pressure flow study?

PURPOSE: We estimated the diagnostic accuracy of ultrasound detrusor thickness measurement for BOO and investigated whether this method can replace PFS for the diagnosis of BOO in some patients with lower urinary tract symptoms. MATERIALS AND METHODS: Detrusor thickness was measured by linear ultrasound (7.5 MHz) at a filling volume of greater than 50% of cystometric capacity in 102 men undergoing PFS for LUTS. All patients with prior treatment for bladder outlet obstruction and those with underlying neurological disorders were excluded from analysis. Detrusor thickness was correlated with PFS data. Obstruction was defined according to the Abrams-Griffiths nomogram. RESULTS: Detrusor thickness was significantly higher (p <0.0001) in obstructed (61 cases, median detrusor thickness 2.7 mm, IQR 2.4 to 3.3) compared to unobstructed (18 cases, median detrusor thickness 1.7 mm, IQR 1.5 to 2) as well as equivocal (23 cases, median detrusor thickness 1.8 mm, IQR 1.5 to 2.2) cases. A weak to medium Spearman correlation was found between detrusor thickness and PFS parameters. For a diagnosis of BOO, detrusor thickness of 2.9 mm or greater had a positive predictive value of 100%, a negative predictive value of 54%, specificity of 100% and sensitivity of 43%. ROC analysis revealed that detrusor thickness had a high predictive value for BOO with an AUC of 0.88 (95% CI 0.81-0.94). CONCLUSIONS: In men with LUTS without prior treatment and/or neurological disorders, ultrasonographically assessed detrusor thickness 2.9 mm or greater has a high predictive value for BOO and can replace PFS for the diagnosis of BOO. However, this cutoff value needs to be validated in a larger study population.

Pulmonary capillary pressure. A review

Pulmonary capillary pressure (Pcap) is the predominant force that drives fluid out of the pulmonary capillaries into the interstitium. Increasing hydrostatic capillary pressure is directly proportional to the lung's transvascular filtration rate, and in the extreme leads to pulmonary edema. In the pulmonary circulation, blood flow arises from the transpulmonary pressure gradient, defined as the difference between pulmonary artery (diastolic) pressure and left atrial pressure. The resistance across the pulmonary vasculature consists of arterial and venous components, which interact with the capacitance of the compliant pulmonary capillaries. In pathological states such as acute respiratory distress syndrome, sepsis, and high altitude or neurogenic lung edema, the longitudinal distribution of the precapillary arterial and the postcapillary venous resistance varies. Subsequently, the relationship between Pcap and pulmonary artery occlusion pressure (PAOP) is greatly variable and Pcap can no longer be predicted from PAOP. In clinical practice, PAOP is commonly used to guide fluid therapy, and Pcap as a hemodynamic target is rarely assessed. This approach is potentially misleading. In the presence of a normal PAOP and an increased pressure gradient between Pcap and PAOP, the tendency for fluid leakage in the capillaries and subsequent edema development may substantially be underestimated. Tho-roughly validated methods have been developed to assess Pcap in humans. At the bedside, measurement of Pcap can easily be determined by analyzing a pressure transient after an acute pulmonary artery occlusion with the balloon of a Swan-Ganz catheter.

A comparative study of water perfusion catheters and microtip transducer catheters for urethral pressure measurements

The aim of this study was to compare the maximum urethral closure pressure (MUCP) measures with two different techniques: water perfused catheter and microtip transducer catheters with respect to reproducibility and comparability for urethral pressure measurements. Eighteen women with stress urinary incontinence had repeat static urethral pressure profilometry on a different day using a dual microtip transducer and water perfused catheter (Brown and Wickham). The investigators were blinded to the results of the other. The microtip measurements were taken in the 45 degrees upright sitting position with the patient at rest at a bladder capacity of 250 ml using an 8 Fr Gaeltec(R) double microtip transducer withdrawn at 1 mm/s, and the transducer was orientated in the three o'clock position. Three different measures were taken for each patient. Three water perfusion measurements were performed with the patient at rest in the 45 degrees upright position at a bladder capacity of 250 ml using an 8 Fr BARD dual lumen catheter withdrawn at 1 mm/s. The mean water perfusion MUCP measure was 26.1 cm H(2)0, significantly lower than the mean microtip measure of 35.7 cm H(2)0. The correlation coefficient comparing each water perfusion measurement with the other water perfusion measures in the same patient was excellent, at 0.95 (p = 0.01). Correlation coefficient comparing each microtip measure with the other microtip measure in the same patient was also good, ranging from 0.70 to 0.80. This study confirms that both water perfusion catheters and microtip transducers have excellent or very good reproducibility with an acceptable intraindividual variation for both methods.

Noninvasive determination of intraocular pressure (IOP) in nonsedated mice of 5 different inbred strains

BACKGROUND: Noninvasive intraocular pressure (IOP) measurement in mice is critically important for understanding the pathophysiology of glaucoma. Rebound tonometry is one of the methods that can be used for obtaining such measurements. We evaluated the ability of the rebound tonometer (RT) to determine IOP differences among various mouse strains and whether differences in corneal thickness may affect IOP measurements in these animals. MATERIALS AND METHODS: Five different commonly used mouse strains (BALB/C, CBA/CAHN, AKR/J, CBA/J, and 129P3/J) were used. IOP was measured in eyes from 12 nonsedated animals (6 male and 6 female) from each strain at 2 to 3 months of age using the RT. IOPs were measured in all animals, on 2 different days between 10 AM and 12 PM. Subsequently, a number of eyes from each strain were cannulated to provide a calibration curve specific for that strain. Tonometer readings for all strains were converted to apparent IOP values using the calibration data obtained from the calibration curve of the respective strain. For comparison purposes, IOP values were also obtained using the C57BL/6 calibration data previously reported. IOP for the 5 strains, male and female animals, and the different occasion of measurement were compared using repeat measures analysis of variance. The central corneal thickness (CCT) of another group of 8 male animals from each of the 5 strains was also measured using an optical low coherence reflectometry (OLCR) pachymeter modified for use with mice. CCT values were correlated to mean IOPs of male animals and to the slopes and intercept of individual strain calibration curves. RESULTS: Noninvasive IOP measurements confirm that the BALB/C strain has lower and the CBA/CAHN has higher relative IOPs than other mouse strains while the AKR/J, the CBA/J, and the 129P3/J strains have intermediate IOPs. There is a very good correlation of apparent IOP values obtained by RT with previously reported true IOPs obtained by cannulation. There was a small but statistically significant difference in IOP between male and female animals in 2 strains (129P3/J and AKR/J) with female mice having higher relative IOPs. No correlation between CCT and IOP was detected. CCT did not correlate with any of the constants describing the calibration curves in the various strains. CONCLUSIONS: Noninvasive IOP measurement in mice using the RT can be used to help elucidate IOP phenotype, after prior calibration of the tonometer. CCT has no effect on mouse IOP measurements using the RT.

Use of pressure waves to confirm the correct placement of epidural needles in dogs

An epidural puncture was performed using the lumbosacral approach in 18 dogs, and the lack of resistance to an injection of saline was used to determine that the needle was positioned correctly. The dogs' arterial blood pressure and epidural pressure were recorded. They were randomly assigned to two groups: in one group an injection of a mixture of local anaesthetic agents was made slowly over 90 seconds and in the other it was made over 30 seconds. After 10 minutes contrast radiography was used to confirm the correct placement of the needle. The mean (sd) initial pressure in the epidural space was 0.1 (0.7) kPa. After the injection the mean maximum epidural pressure in the group injected slowly was 5.5 (2.1) kPa and in the group injected more quickly it was 6.0 (1.9) kPa. At the end of the period of measurement, the epidural pressure in the slow group was 0.8 (0.5) kPa and in the rapid group it was 0.7 (0.5) kPa. Waves synchronous with the arterial pulse wave were observed in 15 of the dogs before the epidural injection, and in all the dogs after the epidural injection.

Effects of cerebral perfusion pressure and increased fraction of inspired oxygen on brain tissue oxygen, lactate and glucose in patients with severe head injury

OBJECTIVE: The purpose of the study was to measure the effects of increased inspired oxygen on patients suffering severe head injury and consequent influences on the correlations between CPP and brain tissue oxygen (PtiO2) and the effects on brain microdialysate glucose and lactate. METHODS: In a prospective, observational study 20 patients suffering severe head injury (GCS< or =8) were studied between January 2000 and December 2001. Each patient received an intraparenchymal ICP device and an oxygen sensor and, in 17 patients brain microdialysis was performed at the cortical-subcortical junction. A 6 h 100% oxygen challenge (F IO2 1.0) ( Period A) was performed as early as possible in the first 24 hours after injury and compared with a similar 6 hour period following the challenge ( Period B). Statistics were performed using the linear correlation analysis, one sample t-test, as well as the Lorentzian peak correlation analysis. RESULTS: F IO2 was positively correlated with PtiO2 (p < 0.0001) over the whole study period. PtiO2 was significantly higher (p < 0.001) during Period A compared to Period B. CPP was positively correlated with PtiO2 (p < 0.001) during the whole study. PtiO2 peaked at a CPP value of 78 mmHg performing a Lorentzian peak correlation analysis of all patients over the whole study. During Period A the brain microdialysate lactate was significantly lower (p = 0.015) compared with Period B. However the brain microdialysate glucose remained unchanged. CONCLUSION: PtiO2 is significantly positively correlated with F IO2, meaning that PtiO2 can be improved by the simple manipulation of increasing F IO2 and ABGAO2. PtiO2 is positively correlated with CPP, peaking at a CPP value of 78 mmHg. Brain microdialysate lactate can be lowered by increasing PtiO2 values, as observed during the oxygen challenge, whereas microdialysate glucose is unchanged during this procedure. Extension of the oxygen challenge time and measurement of the intermediate energy metabolite pyruvate may clarify the metabolic effects of the intervention. Prospective comparative studies, including analysis of outcome on a larger multicenter basis, are necessary to assess the long term clinical benefits of this procedure.

Risk of Cardiovascular Events and Blood Pressure Control in Hypertensive HIV-Infected Patients: HIV Cohort Study (SHCS)

Background: Prevalence of hypertension in HIV infection is high, and information on blood pressure control in HIV-infected individuals is insufficient. We modeled blood pressure over time and the risk of cardiovascular events in hypertensive HIV-infected individuals. Methods: All patients from the Swiss HIV Cohort Study with confirmed hypertension (systolic or diastolic blood pressure above 139 or 89 mm Hg on 2 consecutive visits and presence of at least 1 additional cardiovascular risk factor) between April 1, 2000 and March 31, 2011 were included. Patients with previous cardiovascular events, already on antihypertensive drugs, and pregnant women were excluded. Change in blood pressure over time was modeled using linear mixed models with repeated measurement. Results: Hypertension was diagnosed in 2595 of 10,361 eligible patients. Of those, 869 initiated antihypertensive treatment. For patients treated for hypertension, we found a mean (95% confidence interval) decrease in systolic and diastolic blood pressure of −0.82 (−1.06 to −0.58) mm Hg and −0.89 (−1.05 to −0.73) mm Hg/yr, respectively. Factors associated with a decline in systolic blood pressure were baseline blood pressure, presence of chronic kidney disease, cardiovascular events, and the typical risk factors for cardiovascular disease. In patients with hypertension, increase in systolic blood pressure [(hazard ratio 1.18 (1.06 to 1.32) per 10 mm Hg increase], total cholesterol, smoking, age, and cumulative exposure to protease inhibitor–based and triple nucleoside regimens were associated with cardiovascular events. Conclusions: Insufficient control of hypertension was associated with increased risk of cardiovascular events indicating the need for improved management of hypertension in HIV-infected individuals.

Increased intraoperative epidural pressure in lumbar spinal stenosis patients with a positive nerve root sedimentation sign

Purpose The sedimentation sign (SedSign) has been shown to discriminate well between selected patients with and without lumbar spinal stenosis (LSS). The purpose of this study was to compare the pressure values associated with LSS versus non-LSS and discuss whether a positive SedSign may be related to increased epidural pressure at the level of the stenosis. Methods We measured the intraoperative epidural pressure in five patients without LSS and a negative SedSign, and in five patients with LSS and a positive SedSign using a Codman TM catheter in prone position under radioscopy. Results Patients with a negative SedSign had a median epidural pressure of 9 mmHg independent of the measurement location. Breath and pulse-synchronous waves accounted for 1–3 mmHg. In patients with monosegmental LSS and a positive SedSign, the epidural pressure above and below the stenosis was similar (median 8–9 mmHg). At the level of the stenosis the median epidural pressure was 22 mmHg. A breath and pulse-synchronous wave was present cranial to the stenosis, but absent below. These findings were independent of the cross-sectional area of the spinal canal at the level of the stenosis. Conclusions Patients with LSS have an increased epidural pressure at the level of the stenosis and altered pressure wave characteristics below. We argue that the absence of sedimentation of lumbar nerve roots to the dorsal part of the dural sac in supine position may be due to tethering of affected nerve roots at the level of the stenosis.

Estimation of aortic pressure waveforms from 4D phase-contrast MRI

Several approaches for the non-invasive MRI-based measurement of the aortic pressure waveform over the heart cycle have been proposed in the last years. These methods are normally based on time-resolved, two-dimensional phase-contrast sequences with uni-directionally encoded velocities (2D PC-MRI). In contrast, three-dimensional acquisitions with tridirectional velocity encoding (4D PC-MRI) have been shown to be a suitable data source for detailed investigations of blood flow and spatial blood pressure maps. In order to avoid additional MR acquisitions, it would be advantageous if the aortic pressure waveform could also be computed from this particular form of MRI. Therefore, we propose an approach for the computation of the aortic pressure waveform which can be completely performed using 4D PC-MRI. After the application of a segmentation algorithm, the approach automatically computes the aortic pressure waveform without any manual steps. We show that our method agrees well with catheter measurements in an experimental phantom setup and produces physiologically realistic results in three healthy volunteers.

Assessment of Intrathecal Pressure in Chondrodystrophic Dogs With Acute Thoracolumbar Disk Disease

OBJECTIVES To assess intrathecal pressure (ITP) in chondrodystrophic dogs with thoracolumbar disk extrusion. STUDY DESIGN Prospective cohort study. ANIMALS Group 1: 11 chondrodystrophic dogs with thoracolumbar disk extrusion and present deep pain sensation. Group 2 (control): 3 healthy chondrodystrophic laboratory dogs without spinal disease. METHODS Diagnosis was based on neurologic signs, magnetic resonance imaging (MRI) findings, and surgical confirmation. Blood pressure was maintained within physiologic range during anesthesia. A standardized surgical procedure was applied to minimize factors that could influence measurement readings. An extended hemilaminectomy was performed and ITP was measured with a fiber optic catheter. The catheter was inserted in the subarachnoid space 1 spinal segment caudal to the level of herniation and its tip was advanced to the site of compression. RESULTS Significantly higher ITP occurred in chondrodystrophic dogs with acute thoracolumbar disk disease compared with controls. ITP was not associated with duration of clinical signs, neurologic status, outcome, degree of spinal cord compression, or signal intensity changes as assessed by MRI. CONCLUSION Acute thoracolumbar disk disease leads to elevated ITP in chondrodystrophic dogs, which may contribute to increased compression of spinal cord parenchyma.

Active relaxation counteracts the effects of ego depletion on performance under evaluative pressure in a state of ego depletion

We tested the assumption that active relaxation following an ego-depletion task counteracts the negative effects of ego depletion on subsequent performance under evaluative pressure. N = 39 experienced basketball players were randomly assigned to a relaxation condition or to a control condition, and then performed a series of free-throws at two points of measurement (T1: baseline vs. T2: after working on a depleting task and either receiving active relaxation or a simple break). The results demonstrated that performance remained constant in the relaxation condition, whereas it significantly decreased in the control condition. The findings are in line with the notion that active relaxation leads to a quicker recovery from ego depletion.