Noninvasive Estimation of Respiratory Mechanics in Spontaneously Breathing Ventilated Patients: A Constrained Optimization Approach.

In 11 mechanically ventilated patients, respiratory mechanics were measured 1) during constant flow inflation and 2) following end-inflation airway occlusion, as proposed in model analysis (J. Appl. Physiol. 58: 1840–1848, 1985. During the latter part of inflation, the relationship between driving pressure and lung volume change was linear, allowing determination of static respiratory elastance (Ers) and resistance (RT). The latter represents in each patient the maximum resistance value that can obtain with the prevailing time constant inhomogeneity. Following occlusion, Ers and RT were also obtained along with RT (min) which represents a minimum, i.e., resistance value that would obtain in the absence of time constant inhomogeneity. A discrepancy between inflation and occlusion Ers and RT was found only in the three patients without positive end-expiratory pressure, and could be attributed to recruitment of lung units during inflation. In all instances Ers and RT were higher than normal. RT(min) was lower in all patients than the corresponding values of RT, indicating that resistance was frequency dependent due to time constant inequalities. Changes in inflation rate did not affect Ers, while RT increased with increasing flow.

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Acute effect of corticosteroids on respiratory mechanics in mechanically ventilated patients with chronic airflow obstruction and acute respiratory failure.

American Journal of Respiratory and Critical Care Medicine ◽

10.1164/ajrccm.149.2.8306023 ◽

1994 ◽

Vol 149 (2) ◽

pp. 306-310 ◽

Cited By ~ 22

Author(s):

F Rubini ◽

C Rampulla ◽

S Nava

Keyword(s):

Respiratory Failure ◽

Acute Respiratory Failure ◽

Respiratory Mechanics ◽

Airflow Obstruction ◽

Acute Effect ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Ventilated Patients

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A Constrained Optimization Approach to Finite Element Mesh Smoothing

ASME 1991 Computers in Engineering Conference: Volume 1 — Artificial Intelligence; Expert Systems; CAD/CAM/CAE; Computational Fluid/Thermal Engineering ◽

10.1115/cie1991-0064 ◽

1991 ◽

Author(s):

V. N. Parthasarathy ◽

Srinivas Kodiyalam

Keyword(s):

Finite Element ◽

Constrained Optimization ◽

Finite Element Mesh ◽

Optimization Approach ◽

Element Mesh ◽

Initial Mesh ◽

Nodal Coordinates ◽

Automatic Mesh ◽

Mesh Generators

Abstract The quality of a finite element solution has been shown to be affected by the quality of the underlying mesh. A poor mesh may lead to unstable and lor inaccurate finite element approximations. Mesh quality is often characterized by the “smoothness” or “shape” of the elements (triangles in 2-D or tetrahedra in 3-D). Most automatic mesh generators produce an initial mesh where the aspect ratio of the elements are unacceptably high. In this paper, a new approach to produce acceptable quality meshes from an initial mesh is presented. Given an initial mesh (nodal coordinates and element connectivity), a “smooth” final mesh is obtained by solving a constrained optimization problem. The variables for the iterative optimization procedure are the nodal coordinates (excluding, the boundary nodes) of the finite element mesh, and appropriate bounds are imposed on these to prevent an unacceptable finite element mesh. Examples are given of the application of the above method for 2/3-D triangular meshes generated using a QUADTREE | OCTREE automatic mesh generators. Results indicate that the new method not only yields better quality elements when compared with the traditional Laplacian smoothing, but also guarantees a valid mesh unlike the Laplacian method.

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D.C. Constrained Optimization Approach for Solving Metal Recovery Processing Problem

Mathematical Optimization Theory and Operations Research - Lecture Notes in Computer Science ◽

10.1007/978-3-030-49988-4_7 ◽

2020 ◽

pp. 101-114

Author(s):

Rentsen Enkhbat ◽

Tatiana V. Gruzdeva ◽

Jamsranjav Enkhbayr

Keyword(s):

Constrained Optimization ◽

Metal Recovery ◽

Optimization Approach ◽

Processing Problem

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Respiratory variation of inferior vena cava diameter and central venous pressure in ventilated and non-ventilated children in fluid refractory septic shock: an observational study

International Journal of Contemporary Pediatrics ◽

10.18203/2349-3291.ijcp20193691 ◽

2019 ◽

Vol 6 (5) ◽

pp. 1947

Author(s):

Mohd Kashif Ali ◽

Eeman Naim

Keyword(s):

Septic Shock ◽

Inferior Vena Cava ◽

Central Venous Pressure ◽

Inferior Vena ◽

Venous Pressure ◽

Vena Cava ◽

Central Venous ◽

Mechanically Ventilated ◽

Spontaneously Breathing ◽

Ventilated Patients

Background: Ultrasound guided fluid assessment in management of septic shock has come up as an adjunct to the current gold standard Central Venous Pressure monitoring. This study was designed to observe the respiro-phasic variation of IVC diameter (RV-IVCD) in invasively mechanically ventilated and spontaneously breathing paediatric patients of fluid refractory septic shock.Methods: This was a prospective observational study done at Paediatric intensive Care Unit (PICU) in Paediatric ward of Jawaharlal Nehru Medical College and Hospital (JNMCH) from February 2016 to June 2017. 107 consecutive patients between 1 year to 16 years age who were in shock despite 40ml/kg of fluid administration were included. Inferior Vena Cava (IVC) diameters were measured at end-expiration and end inspiration and the IVC collapsibility index was calculated. Simultaneously Central Venous Pressure (CVP) was recorded. Both values were obtained in ventilated and non-ventilated patients. Data was analysed to determine to look for the profile of RV-IVCD and CVP in ventilated and non-ventilated cases.Results: Out of 107 patients, 91 were on invasive mechanical ventilation and 16 patients were spontaneously breathing. There was a strong negative correlation between central venous pressure (CVP) and inferior vena cava collapsibility (RV-IVCD) in both spontaneously breathing (-0.810) and mechanically ventilated patients (-0.700). Negative correlation was significant in both study groups in CVP <8 mmHg and only in spontaneously breathing patients in CVP 8-12 mmHg range. IVC collapsibility showed a decreasing trend with rising CVP in both spontaneously breathing and mechanically ventilated patients.Conclusion: Ultrasonography guided IVCCI appears to be a valuable index in assessing fluid status in both spontaneously breathing and mechanically ventilated septic shock patients. However, more data is required from the paediatric population so as to define it as standard of practice.

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