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Pulmonary Performance in Laboratory Animals Exposed to Toxic Agents and Correlations with Lung Disease in Humans
Published in Jacob Loke, Pathophysiology and Treatment of Inhalation Injuries, 2020
Clearly, the advantages of this system include (1) the rapidity with which CO2 challenges can be performed, (2) the low variability in the response of a control group, and (3) the fact that CO2 challenges can be performed repeatedly in the same animals. Because of this last feature, it is possible to detect acute pulmonary effects as well as the development of chronic pulmonary effects. Furthermore, recovery from induced pulmonary effects can be assessed by this method One general disadvantage of CO2 challenges themselves is that an abnormal response to CO2 can occur because of toxicity within or outside the pulmonary system and, thus, the test is not diagnostic. Another disadvantage should be noted. While the amplitude of ΔP measured from minima to maxima is proportional to VT, this is not so during the entire breath (Bargeton and Barres, 1986). During the breath, not only are thermal and humidification effects contributing to ΔP but also added is the pressure to overcome airway resistance (Bargeton and Barres, 1956). If intense bronchoconstriction is present, the minima and maxima are shifted in time and no longer reflect VT amplitude, and, in fact, overestimate VT (Alarie et al., 1985; Wong et al., 1985; Schaper et al., 1985). This can be clearly seen in Figures 9 and 11. With intense bronchoconstriction, f decreases, particularly due to a longer expiratory phase (TE) and this will alert the investigator.
Cardiac catheterization
Published in Neeraj Parakh, Ravi S. Math, Vivek Chaturvedi, Mitral Stenosis, 2018
Raghav Bansal, Ganesan Karthikeyan
where ΔP is the pressure gradient across the resistance and Q is the flow through the resistance. ΔP is the mean transvalvular gradient and Q is the antegrade flow through the valve calculated similarly to Gorlin’s equation.
Production of Aortic Valve Sound
Published in Mano Thubrikar, The Aortic Valve, 2018
For obtaining a numerical solution, data is taken from both in vivo and in vitro measurements. The stiffness coefficient of a stented fresh porcine valve is calculated as K = ΔP π a2/χo, which represents static solution of Equation 2. K is determined from the experiments with porcine valve where deflection χo is measured as a function of pressure gradient ΔP, and is found to be 6.8 × 106 dynes/cm. For solving the modeling equations, the input pressure is taken to be a ramp function where ΔP increases at a rate of 8570 mmHg/s for time <0.0175 s. The ΔP is considered constant at 150 mmHg/s for time >0.0175 s. There are two unknowns, m and D, in Equation 2. The value of m is calculated from the equation m = K/ωn2 where the value of ωn2 is determined from the experiment. The effective vibratory mass m is calculated to be 195 g. The value of D used is 2.8 × 103 dynes s/cm.
How to recognize patients at risk of self-inflicted lung injury
Published in Expert Review of Respiratory Medicine, 2022
Tommaso Pettenuzzo, Nicolò Sella, Francesco Zarantonello, Alessandro De Cassai, Federico Geraldini, Paolo Persona, Elisa Pistollato, Annalisa Boscolo, Paolo Navalesi
The measurement of Pes allows calculating PL by subtracting Pes from airway pressure. During partial ventilatory assistance, i.e. patient effort and ventilator assistance both contribute to varying extents to generate the ventilatory output, the distending pressure applied to the lung can be expressed as dynamic transpulmonary driving pressure (ΔPL,dyn), quantified as the PL change between end-inspiration and end-expiration [87]. In a small physiologic study on patients intubated for different ARF etiologies, safe limits to prevent injurious ΔPL,dyn were identified between 15 cmH2O to 20 cmH2O [88]. This threshold is similar to that suggested for static transpulmonary driving pressure, i.e. (airway plateau pressure-PEEP) – (esophageal plateau pressure-end-expiratory esophageal pressure), by some experts [87].
Lung and diaphragm protective ventilation: a synthesis of recent data
Published in Expert Review of Respiratory Medicine, 2022
Vlasios Karageorgos, Athanasia Proklou, Katerina Vaporidi
The ΔP is the pressure distending both lungs and chest wall at end-inspiration, while the pressure that actually represents alveolar stress is the transpulmonary driving pressure (ΔPL) [4]. Thresholds of ΔPL associated with risk of VILI have not been examined in clinical studies. Based on physiological and experimental studies, a threshold of ΔPL<20 cmH2O is suggested for patients with healthy lungs, and of 10–12 cmH2O for those with ARDS [22,23]. Experimental studies have shown that VILI can develop in healthy lungs when the strain induced by high tidal volume is greater than 1.5–2 [24], corresponding to transpulmonary pressure of 18–26 cmH2O. In the presence of lung inhomogeneity, regional stress can be significantly greater, and thus it appears reasonable to aim for much lower ΔPL in patients with lung injury. Additionally, the validated threshold of ΔP of 15 cmH2O, corresponds to a ΔPL of 10 cmH2O, when the ratio of the lung to the respiratory system elastance is 0.7 (ΔPL = ΔP x EL/ERS), the median value reported in ARDS patients [4].
A comparison between the mechanical properties of the hepatic round ligament and the portal vein: a clinical implication on surgical reconstruction of the portal and superior mesenteric veins
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Wentao Zhu, Rongqiang Song, Xuefeng Cao, Lei Zhou, Qiang Wei, Haibin Ji, Rongzhan Fu
Biomechanical property analysis on HRL and PV samples was performed on an electronic peristaltic pump (HL-2D, Huxi Analysis Instrument Factory) and a pressure transducer (CY-YB-Y, Jinghua Electric Equipment Factory, Beijing, China) as previously described (Wang et al. 2009). Tissues were kept in Krebs’ solution supplemented with oxygen during the entire experiment at 37 °C. Isotropic incremental modulus (Einc), circumferential incremental modulus (Ev), longitudinal incremental modulus (Ep) and segment incremental compliance (C) were calculated using the following formula: Einc = 0.75 × ΔP/ ΔR × R2/h; Ev = ΔP/ΔR × R/2; Ep = ΔP/ΔR × R; C = dV/dP = 2πR × ΔR/ΔP, where P, R, and h are pressure, radius, and thickness of the blood vessel, respectively. ΔP is the pressure change and ΔR is the radius change. Breaking strength represents the stress at the plateau of the stress-strain curve. Independent t-test was applied to determine the statistical significance between the measured variables. p < 0.05 indicates a statistical difference.