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Pressure–Volume Loop of the Left Ventricle
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
An increase in diastolic pressure at a given ventricular volume indicates decreased ventricular distensibility. This produces a parallel upward shift of the diastolic pressure–volume relationship. Reduced distensibility may occur from either intrinsic causes such as myocardial ischaemia or extrinsic restrictions to ventricular filling, such as constrictive pericarditis or pericardial effusion.
The cardiovascular system
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Mary N Sheppard, C. Simon Herrington
Mönckeberg's medial calcific sclerosis refers to medial calcification, usually at the internal elastic lamina (IEL). It is common and occurs independently of atherosclerosis. It is more frequent in people aged >50 years and in people with diabetes and renal failure. In advanced cases, vessels may become rigid and lose their distensibility. It can be seen easily as an opaque vessel on normal radiographs and as purple material on histological slides. It is not usually associated with clinical sequelae because it does not cause narrowing of the lumen.
Mechanisms of Continence and Defecation
Published in Han C. Kuijpers, Colorectal Physiology: Fecal Incontinence, 2019
Richard L. Grotz, John H. Pemberton
These observations are quantifiable; the distensibility of the rectum is calculated by plotting the slope of the ΔV/ΔP; Heppell and co-workers found the distensibility to be 16.8 ml/H20 in seven healthy volunteers.4 In addition, the ability of the rectal wall to accommodate is dependent on the rate of delivery of enteric contents into the rectum. Animal studies have shown that rectal wall relaxation in response to intraluminal distention is modulated by the pelvic nerves.31 Gastrointestinal transit of a solid meal is slowed by painless rectal distension.32 Thus, numerous factors contribute to controlling the rate of slowing rectal filling.
Arterial Stiffness and Cardiorespiratory Fitness Are Associated With Cognitive Function in Older Adults
Published in Behavioral Medicine, 2022
Justin R. Mason, Gershon Tenenbaum, Salvador Jaime, Nelson Roque, Arun Maharaj, Arturo Figueroa
Characteristics of the left common carotid artery were obtained by using an ultrasound scanner (Phillips HD11 XE, Philips Medical) equipped with a high-resolution linear array transducer. A longitudinal image (30 seconds) of the cephalic portion of the common carotid artery was acquired ∼2cm proximal to the carotid bulb and optimized for diameter detection. All digital images were analyzed offline by a single researcher using automated image analysis software (Carotid Artery Analyzer, Quipu srl.). This setup enabled the measurement of the intima-media thickness, end-diastolic diameter (d), and change in diameter (Δd = end-systolic diameter – end-diastolic diameter). Combined with brachial BP, three markers were calculated to evaluate elastic properties of the common carotid artery: (a) β-stiffness index = ln(systolic BP/diastolic BP)/(Δd/d), as stress-to-strain ratio; (b) distensibility = 1/(β-stiffness × intima-media thickness), as the inverse of β-stiffness and adjusted to intima-media thickness; and (c) Young’s elastic modulus = 133.3 (pulse pressure) (PP)/(Δd/d), representing elastic properties of arterial wall material.33,34
Analysis of the passive biomechanical behavior of a sheep-specific aortic artery in pulsatile flow conditions
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Claudio M. García–Herrera, Álvaro A. Cuevas, Diego J. Celentano, Álvaro Navarrete, Pedro Aranda, Emilio Herrera, Sergio Uribe
As already mentioned, the distensibility (DC) and incremental modulus (Einc) are two common indicators that allow characterizing the mechanical response of a specific biological tissue. These two parameters depend on both the geometry (diameter and thickness) and the pressure in the specific analyzed zone (positions I, II and III from Figure 1). Experimental results from the CST (Table 1) show that maximum distensibility is in position II, and thus it has a greater capacity to change its shape, which is in accordance with the greatest variation in the diameter measured in this position. This agrees with the physiological analysis, because it is in this zone of the aorta where the pressure wave coming from the heart is damped (Montorzi-Thorell 2004). Similarly, it can be noticed that the greatest change in the relative diameter is found in position II (Figure 8), which is the area of the aorta where, physiologically, the pressure wave loses energy due to the curvature of the aortic arch, such that the consistent dissipation of this energy occurs by a deformation of the artery. From Table 1, position III shows signs of stiffening due to the large value of the incremental modulus. In general, the measurements exhibit similar values, which means that the numerical predictions are representative of the artery response in the CST. Therefore, it is acceptable to get an average value for these two parameters to estimate the response under in-vivo conditions.
Assessment of anal sphincter distensibility following the STARR procedure: a pilot study
Published in Acta Chirurgica Belgica, 2020
Charlotte Desprez, Chloé Melchior, Guillaume Gourcerol, Jean-Jacques Tuech, Estelle Houivet, Anne-Marie Leroi, Valérie Bridoux
The STARR procedure was performed as described by Pigot [1] For assessing the impact of the STARR procedure on anorectal symptoms, the Cleveland Clinic Severity (CCSC) [4], ODS [5], and Kess scores [6] were determined before and three months post-surgery. An anal distensibility study was performed before and three months post-surgery using a previously described methodology [3]. Briefly, high-resolution impedance planimetry was used to measure the relationship between luminal dimensions and distensive pressure (i.e. distensibility) during controlled volumetric distension [3]. The distensibility index as calculated by the cross-sectional area divided by the intra-balloon pressure at 40 mL of inflation at rest and during voluntary contraction was the primary endpoint of the study [3]. An endoanal ultrasound (7 Mhz, 360°, Two-Dimensional US, Brüel and Kjaer, Naerum, Denmark) was also performed before and three months post-surgery to verify the absence of anal sphincter defects that may have been caused by the STARR procedure. Given the small size of the patient cohort, the results were expressed individually. The normal 40 mL distensibility indexes at rest and during squeeze were defined, respectively, as ≤1mm2.mmHg−1 and ≤0.5 mm2.mmHg−1 based on measurements from a group of healthy volunteers [3].