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Anaesthesiology Intensive Therapy 2014Over the last few decades, increasing attention has been paid to understanding the pathophysiology, aetiology, prognosis, and treatment of elevated intra-abdominal... (Review)
Review
Over the last few decades, increasing attention has been paid to understanding the pathophysiology, aetiology, prognosis, and treatment of elevated intra-abdominal pressure (IAP) in trauma, surgical, and medical patients. However, there is presently a relatively poor understanding of intra-abdominal volume (IAV) and the relationship between IAV and IAP (i.e. abdominal compliance). Consensus definitions on Cab were discussed during the 5th World Congress on Abdominal Compartment Syndrome and a writing committee was formed to develop this article. During the writing process, a systematic and structured Medline and PubMed search was conducted to identify relevant studies relating to the topic. According to the recently updated consensus definitions of the World Society on Abdominal Compartment Syndrome (WSACS), abdominal compliance (Cab) is defined as a measure of the ease of abdominal expansion, which is determined by the elasticity of the abdominal wall and diaphragm. It should be expressed as the change in IAV per change in IAP (mL [mm Hg]⁻¹). Importantly, Cab is measured differently than IAP and the abdominal wall (and its compliance) is only a part of the total abdominal pressure-volume (PV) relationship. During an increase in IAV, different phases are encountered: the reshaping, stretching, and pressurisation phases. The first part of this review article starts with a comprehensive list of the different definitions related to IAP (at baseline, during respiratory variations, at maximal IAV), IAV (at baseline, additional volume, abdominal workspace, maximal and unadapted volume), and abdominal compliance and elastance (i.e. the relationship between IAV and IAP). An historical background on the pathophysiology related to IAP, IAV and Cab follows this. Measurement of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The Cab is one of the most neglected parameters in critically ill patients, although it plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion. The definitions presented herein will help to understand the key mechanisms in relation to Cab and clinical conditions and should be used for future clinical and basic science research. Specific measurement methods, guidelines and recommendations for clinical management of patients with low Cab are published in a separate review.
Topics: Abdomen; Compliance; Consensus; Critical Illness; Humans; Intra-Abdominal Hypertension; Pressure; Terminology as Topic
PubMed: 25432558
DOI: 10.5603/AIT.2014.0062 -
Physiological Reports Dec 2018Profound changes occur in the maternal circulation during pregnancy. Routine measures of arterial function - central systolic pressure (CSP) and augmentation index (AIx)...
Profound changes occur in the maternal circulation during pregnancy. Routine measures of arterial function - central systolic pressure (CSP) and augmentation index (AIx) - decline during normal human pregnancy. The objectives of this study were twofold: (1) explore wave reflection indices besides CSP and AIx that are not routinely reported, if at all, during normal human pregnancy; and (2) compare wave reflection indices and global arterial compliance (gAC) obtained from carotid artery pressure waveforms (CAPW) as a surrogate for aortic pressure waveforms (AOPW) versus AOPW synthesized from radial artery pressure waveforms (RAPW) using a generalized transfer function. To our knowledge, a comparison of these two methods has not been previously evaluated in the context of pregnancy. Ten healthy women with normal singleton pregnancies were studied using applanation tonometry (SphygmoCor) at pre-conception, and then during 10-12 and 33-35 gestational weeks. CSP and AIx declined, and gAC increased during pregnancy as previously reported. As a consequence of the rise in gAC, the return of reflected waves of lesser magnitude from peripheral reflection sites to the aorta was delayed that, in turn, reduced systolic duration of reflected waves, augmentation index, central systolic pressure, LV wasted energy due to reflected waves, and increased brachial-central pulse pressure. For several wave reflection indices, those derived from CAPW as a surrogate for AOPW versus RAPW using a generalized transfer function registered greater gestational increases of arterial compliance. This discordance may reflect imprecision of the generalized transfer function for some waveform parameters, though potential divergence of carotid artery and aortic pressure waveforms during pregnancy cannot be excluded.
Topics: Adult; Aorta; Blood Pressure; Carotid Arteries; Compliance; Female; Humans; Pregnancy; Pulse; Pulse Wave Analysis
PubMed: 30578623
DOI: 10.14814/phy2.13947 -
Journal of Applied Physiology... Oct 2012Arterial compliance is mainly determined by the elasticity of proximal large-conduit arteries of which the aorta is the largest contributor. Compliance forms an...
Arterial compliance is mainly determined by the elasticity of proximal large-conduit arteries of which the aorta is the largest contributor. Compliance forms an important part of the cardiac load and plays a role in organ (especially coronary) perfusion. To follow local changes in aortic compliance, as in aging, noninvasive determination of compliance distribution would be of great value. Our goal is to determine regional aortic compliance noninvasively in the human. In seven healthy individuals at six locations, aortic blood flow and systolic/diastolic area (ΔA) was measured with MRI. Simultaneously brachial pulse pressure (ΔP) was measured with standard cuff. With a transfer function we derived ΔP at the same aortic locations as the MRI measurements. Regional aortic compliance was calculated with two approaches, the pulse pressure method, and local area compliance (ΔA/ΔP) times segment length, called area compliance method. For comparison, pulse wave velocity (PWV) from local flows at two locations was determined, and compliance was derived from PWV. Both approaches show that compliance is largest in the proximal aorta and decreases toward the distal aorta. Similar results were found with PWV-derived compliance. Of total arterial compliance, ascending to distal arch (segments 1-3) contributes 40% (of which 15% is in head and arms), descending aorta (segments 4 and 5) 25%, and "hip, pelvic and leg arteries" 20%. Pulse pressure method includes compliance of side branches and is therefore larger than the area compliance method. Regional aortic compliance can be obtained noninvasively. Therefore, this technique allows following changes in local compliance with age and cardiovascular diseases.
Topics: Adult; Aging; Aorta; Blood Pressure; Cardiovascular Diseases; Compliance; Diastole; Female; Heart; Humans; Magnetic Resonance Imaging; Male; Pulse Wave Analysis; Regional Blood Flow; Systole; Young Adult
PubMed: 22936729
DOI: 10.1152/japplphysiol.00432.2012 -
Journal of Applied Physiology... Aug 2019Heart failure with preserved ejection fraction (HFpEF) is a common cause of hospital admission in patients over 65 yr old and has high mortality. HFpEF is characterized...
Heart failure with preserved ejection fraction (HFpEF) is a common cause of hospital admission in patients over 65 yr old and has high mortality. HFpEF is characterized by left ventricular (LV) hypertrophy that reduces compliance. Current HFpEF therapies control symptoms, but no existing medications or therapies can sustainably increase LV compliance. LV trabeculae develop hypertrophy and fibrosis that contribute to reduced LV compliance. This study expands our previous results in ex vivo human hearts to show that severing LV trabeculae increases diastolic compliance in an ex vivo working rabbit heart model. Trabecular cutting was performed in ex vivo rabbit hearts set up in a working heart perfusion system perfused with oxygenated Krebs-Henseleit buffer. A hook was inserted in the LV to cut trabeculae. End-systolic and end-diastolic pressure-volume relationships during transient preload reduction were recorded using an admittance catheter in the following three groups: control (no cutting; = 9), mild cutting (15 cuts; = 5), and aggressive cutting (30 cuts; = 5). In a second experiment, each heart served as its own control. Hemodynamic data were recorded before and after trabecular cutting ( = 10) or sham cutting ( = 5) within the same heart. In the first experiments, trabecular cutting did not affect systolic function ( > 0.05) but significantly increased overall diastolic compliance ( = 0.009). Greater compliance was seen as trabecular cutting increased ( = 0.002, = 0.435). In the second experiment, significant increases in systolic function ( = 0.048) and diastolic compliance ( = 0.002) were seen after trabecular cutting compared with baseline. In conclusion, trabecular cutting significantly increases diastolic compliance without reducing systolic function. We postulate that, in mammalian hearts, free-running trabeculae carneae exist to provide tensile support to the left ventricle and minimize diastolic wall stress. Because of hypertrophy and fibrosis of trabeculae in patients with left ventricular hypertrophy, this supportive role can become pathologic, worsening diastolic compliance. We demonstrate a novel operation involving cutting trabeculae as a method to acutely increase diastolic compliance in patients presenting with heart failure and diastolic dysfunction to improve their left ventricle compliance.
Topics: Animals; Compliance; Diastole; Female; Heart; Heart Failure; Heart Ventricles; Hemodynamics; Male; Myocardium; Rabbits; Stroke Volume; Systole; Ventricular Dysfunction, Left; Ventricular Function, Left
PubMed: 31219774
DOI: 10.1152/japplphysiol.00087.2019 -
British Journal of Clinical Pharmacology 1984Brachial artery haemodynamics, including arterial diameter, blood flow velocity, blood flow and compliance of the brachial artery may be evaluated non-invasively in man,... (Review)
Review
Brachial artery haemodynamics, including arterial diameter, blood flow velocity, blood flow and compliance of the brachial artery may be evaluated non-invasively in man, using pulsed Doppler methods. In patients with sustained untreated essential hypertension, brachial artery diameter is increased, blood flow is normal and arterial compliance is reduced independently of the level of blood pressure. Converting enzyme inhibition may reverse the large artery abnormalities, causing an increase in arterial diameter, blood flow and arterial compliance both in acute and long-term investigations. These changes in large arteries may contribute towards improved cardiovascular morbidity and less mortality in treated hypertensive patients.
Topics: Angiotensin-Converting Enzyme Inhibitors; Blood Flow Velocity; Brachial Artery; Compliance; Dipeptides; Enalapril; Hemodynamics; Humans; Hypertension; Renin-Angiotensin System; Vascular Resistance
PubMed: 6099739
DOI: 10.1111/j.1365-2125.1984.tb02603.x -
PloS One 2018The objective was to better understand how a series compliance alters contraction kinetics and power output of muscle to enhance the work done on a load. A mathematical...
The objective was to better understand how a series compliance alters contraction kinetics and power output of muscle to enhance the work done on a load. A mathematical model was created in which a gravitational point load was connected via a linear spring to a muscle (based on the contractile properties of the sartorius of leopard frogs, Rana pipiens). The model explored the effects of load mass, tendon compliance, and delay between onset of contraction and release of the load (catch) on lift height and power output as measures of performance. Series compliance resulted in increased lift height over a relatively narrow range of compliances, and the effect was quite modest without an imposed catch mechanism unless the load was unrealistically small. Peak power of the muscle-tendon complex could be augmented up to four times that produced with a muscle alone, however, lift height was not predicted by peak power. Rather, lift height was improved as a result of the compliance synchronizing the time courses of muscle force and shortening velocity, in particular by stabilizing shortening velocity such that muscle power was sustained rather than rising and immediately falling. With a catch mechanism, enhanced performance resulted largely from energy storage in the compliance during the period of catch, rather than increased time for muscle activation before movement commenced. However, series compliance introduced a trade-off between work done before versus after release of the catch. Thus, the ability of tendons to enhance locomotor performance (i.e. increase the work done by muscle) appears dependent not only on their established role in storing energy and increasing power, but also on their ability to modulate the kinetics of muscle contraction such that power is sustained over more of the contraction, and maximizing the balance of work done before versus after release of a catch.
Topics: Animals; Biomechanical Phenomena; Compliance; Computer Simulation; Elastic Modulus; Locomotion; Models, Biological; Muscle Contraction; Rana pipiens; Tendons; Weight-Bearing
PubMed: 29370246
DOI: 10.1371/journal.pone.0191828 -
Journal of Biomechanical Engineering Jun 2013The recombinant congenic mouse strains HcB-8 and HcB-23 differ in femoral shape, size, and strength, with HcB-8 femora being more gracile, more cylindrical, weaker, and...
The recombinant congenic mouse strains HcB-8 and HcB-23 differ in femoral shape, size, and strength, with HcB-8 femora being more gracile, more cylindrical, weaker, and having higher Young's modulus. In previous work, we mapped a robust, pleiotropic quantitative trait locus for these bone traits. Ece1, encoding endothelin converting enzyme 1, is a positional candidate gene for this locus, and was less expressed in HcB-8 bone. We hypothesized that the same genetic factors would impose analogous developmental trajectories on arteries to those in bones. Cardiovascular hemodynamics and biomechanics of carotids were measured in adult HcB-8 and HcB-23 mice. Biological differences in heart and arteries were examined at mRNA and protein levels. As in bone, Ece1 expression was higher in HcB-23 heart and arteries (p < 0.05), and its expression was correlated with that of the endothelin B type receptor target Nos3, encoding endothelial nitric oxide synthase. HcB-8 mice had higher ambulatory blood pressure (p < 0.005) than HcB-23 mice. Ex vivo, at identical pressures, HcB-8 carotid arteries had smaller diameters and lower compliance (p < 0.05), but the same elastic modulus compared to HcB-23 carotid arteries. HcB-8 hearts were heavier than HcB-23 hearts (p < 0.01). HcB-8 has both small, stiff bones and small, stiff arteries, lower expression of Ece1 and Nos3, associated in each case with less favorable function. These findings suggest that endothelin signaling could serve as a nexus for the convergence of skeletal and vascular modeling, providing a potential mechanism for the epidemiologic association between skeletal fragility and atherosclerosis.
Topics: Animals; Arteries; Aspartic Acid Endopeptidases; Biomechanical Phenomena; Blood Pressure; Bone and Bones; Compliance; Endothelin-Converting Enzymes; Endothelins; Gene Expression Regulation; Male; Metalloendopeptidases; Mice; Nitric Oxide; Organ Size; RNA, Messenger; Species Specificity
PubMed: 23699715
DOI: 10.1115/1.4024161 -
Schizophrenia Research May 2012Peripheral arterial compliance is a measure of elasticity of the arteries that has been found to be a robust predictor of prevalent arteriosclerosis as well as incident...
BACKGROUND
Peripheral arterial compliance is a measure of elasticity of the arteries that has been found to be a robust predictor of prevalent arteriosclerosis as well as incident stroke and myocardial infarction. Psychiatric diagnoses and second generation antipsychotics may contribute to cardiovascular risk and stroke, but effects on peripheral arterial compliance are unknown. This study compared peripheral arterial compliance in healthy male controls to male patients with psychiatric diagnoses who were treated with quetiapine or risperidone or off antipsychotics at time of testing.
METHODS
The groups consisted of 63 patients with mental illness taking quetiapine, risperidone, or no antipsychotics. There were 111 males in the control group. Mean thigh and calf arterial compliance among four groups were compared by ANCOVA, adjusting for body mass index and Framingham Risk Score. All patients were also compared to the control group. Compliance was measured with a computerized plethysmography device.
RESULTS
Patients (n=63) had significantly lower arterial compliance in both thigh and calf than the controls. Arterial compliance in the calf was significantly lower in the subgroups of quetiapine (n=16) and risperidone (n=19) treated, and in unmedicated (n=28) patients than in controls. In the thigh, patients taking either quetiapine or risperidone had significantly lower arterial compliance than controls. These subgroups did not differ from each other in arterial compliance.
CONCLUSION
The presence of psychiatric diagnoses is associated with reduced arterial compliance. A large study may be required to measure any specific affects of antipsychotics such as quetiapine and risperidone on compliance compared to controls.
Topics: Adult; Aged; Analysis of Variance; Antipsychotic Agents; Blood Pressure; Compliance; Dibenzothiazepines; Femoral Artery; Humans; Male; Mental Disorders; Middle Aged; Quetiapine Fumarate; Retrospective Studies; Risperidone
PubMed: 22377105
DOI: 10.1016/j.schres.2012.02.007 -
PloS One 2013The pericardial tissue is commonly used to produce bio-prosthetic cardiac valves and patches in cardiac surgery. The procedures adopted to prepare this tissue consist in...
BACKGROUND
The pericardial tissue is commonly used to produce bio-prosthetic cardiac valves and patches in cardiac surgery. The procedures adopted to prepare this tissue consist in treatment with aldehydes, which do not prevent post-graft tissue calcification due to incomplete xeno-antigens removal. The adoption of fixative-free decellularization protocols has been therefore suggested to overcome this limitation. Although promising, the decellularized pericardium has not yet used in clinics, due to the absence of proofs indicating that the decellularization and cryopreservation procedures can effectively preserve the mechanical properties and the immunologic compatibility of the tissue.
PRINCIPAL FINDINGS
The aim of the present work was to validate a procedure to prepare decellularized/cryopreserved human pericardium which may be implemented into cardiovascular homograft tissue Banks. The method employed to decellularize the tissue completely removed the cells without affecting ECM structure; furthermore, uniaxial tensile loading tests revealed an equivalent resistance of the decellularized tissue to strain, before and after the cryopreservation, in comparison with the fresh tissue. Finally, immunological compatibility, showed a minimized host immune cells invasion and low levels of systemic inflammation, as assessed by tissue transplantation into immune-competent mice.
CONCLUSIONS
Our results indicate, for the first time, that fixative-free decellularized pericardium from cadaveric tissue donors can be banked according to Tissue Repository-approved procedures without compromising its mechanical properties and immunological tolerance. This tissue can be therefore treated as a safe homograft for cardiac surgery.
Topics: Animals; Compliance; Cryopreservation; Fixatives; Humans; Immunocompetence; Implants, Experimental; Materials Testing; Mice; Pericardium; Stress, Mechanical; Tissue Engineering
PubMed: 23705010
DOI: 10.1371/journal.pone.0064769 -
The Canadian Journal of Cardiology Feb 2006The understanding of the pathophysiology of atherosclerosis has advanced greatly in the past decade. Cardiovascular risk factors increase the likelihood of an adverse... (Review)
Review
The understanding of the pathophysiology of atherosclerosis has advanced greatly in the past decade. Cardiovascular risk factors increase the likelihood of an adverse event by having a detrimental effect on the blood vessel wall. Abnormal interactions among cholesterol, inflammatory mediators, platelets and the vascular wall lead to atherogenesis and cardiac events. In an effort to better understand this process, develop surrogate end points for clinical trials and, ultimately, better risk stratify individuals, a variety of measures of arterial function have been studied. These include measures of endothelial health and arterial compliance. The current paper reviews the various techniques available for the study of vascular health. While not yet routinely used for clinical care, these measurements provide important insights into the pathophysiology and treatment of atherosclerosis.
Topics: Arteries; Atherosclerosis; Biomarkers; Blood Pressure; Cardiovascular Diseases; Compliance; Elasticity; Endothelium, Vascular; Humans; Prognosis; Risk Factors
PubMed: 16498516
DOI: 10.1016/s0828-282x(06)70990-4