José L. Lage - jll@seas.smu.edu
Mechanical Engineering Department
Southern Methodist University
Dallas, Texas, 75275-0337

Vladimir V. Kulish - mvvkulish@ntu.edu.sg
School of Mechanical & Production Engineering
Nanyang Technological University
50 Nanyang Ave., Singapore 639798

Connie C. W. Hsia - CONNIE.HSIA@email.swmed.edu
Department of Internal Medicine
University of Texas - Southwestern Medical Center
Dallas, Texas, 75235-9034

Robert L. Johnson, Jr. - ROBERT.JOHNSON@email.swmed.edu
Department of Internal Medicine
University of Texas - Southwestern Medical Center
Dallas, Texas, 75235-9034

A novel mathematical model derived from fundamental engineering principles for simulating the spatial and temporal gas diffusion process within the alveolar region of the lung was presented recently by Koulich et al. (1999). The model depends on a physical property of the alveolar region termed effective diffusivity, function of the diffusivity, solubility, and interface geometry of each alveolar constituent. Unfortunately, the direct determination of the effective diffusivity of the alveolar region is impractical because of the difficulty in describing the internal geometry of each alveolar constituent. However, the transient solution of the macroscopic model can be used in conjunction with the lung diffusing capacity (measured in laboratory via the single-breath technique) to determine the effective diffusivity of the alveolar region. With the effective diffusivity known, the three-dimensional effects of red blood cell distribution on the lung diffusing capacity can be predicted via numerical simulations. The results, obtained for normal (random), uniform, center-cluster, corner-cluster, and several chain-like distributions, unveil a strong relationship between the type of cell distribution and the lung diffusing capacity.

Keywords: mass diffusion, lung diffusing capacity, alveolus, macroscopic model, transient simulation
 
 

J. V. C. Vargas - jvargas@demec.ufpr.br
M. L. Brioschi - mbrioschi@hotmail.com
D. Colman - daniel@demec.ufpr.br
Universidade Federal do Paraná, Departamento de Engenharia Mecânica
Cx. P. 19011 - 81531-990 - Curitiba, PR, Brasil

L. A. O. Rocha - lar2@duke.edu
Duke University, Department of Mechanical Engineering & Materials Science
Durham, NC 27708-0300 USA

In this work, hypothermia associated with pneumoperitoneum procedures is studied. A thermodynamic model is developed to allow for the computational simulation of the thermal body response to pneumoperitoneum procedures, which are required by laparoscopic surgery. The numerical results predict the body temperature decay (or loss of energy) in time when the pneumoperitoneum procedure is conducted in a patient. The influence of several operating parameters (e.g., inlet air mass flow rate and temperature) on the resulting hypothermia level is analized. The model therefore allows for the search of mechanisms to reduce the loss of energy, and consequently, the hypothermia level due to pneumoperitoneum procedures.

Keywords: Balance of energy, Intra-abdominal hypertension, Body temperature regulation
 
 

Marcelo R. Errera
Departamento de Engenharia Mecânica - Universidade Federal do Paraná (UFPR)
CP 19011 - Curitiba, PR 81531-990 Brasil - errera@demec.ufpr.br

Silvio L. M. Junqueira
Departamento Acadêmico de Mecânica - Núcleo de Pesquisa em Engenharia Simultânea
Centro Federal de Educação Tecnológica do Paraná (CEFET-PR)
Av. Sete de Setembro, 3165 - Curitiba, PR 80230-901 Brasil - silvio@nupes.cefetpr.br

Laser is being employed in diverse applications nowadays, especially as a surgical tool as well as machining tool. Applied, empirical and experimental research has been the main focus of the work found in the Bioengineering literature. On the other hand, fundamental and theoretical studies of semi-transparent solid materials under phase-change due to laser radiation are not so frequently published. This paper deals with the fundamentals of such phenomena and leads to a mathematical model, to the main scales and physical groups. Numerical solutions of a case study are presented, discussed and compared to the literature. Expressions and correlations are presented in order to assist experimental and applied work of laser surgery and industrial applications.

Keywords: Laser, Phase Change, Bioengineering, Stefan Problem, Laser Machining.
 
 

Marcos Enê Chaves Oliveira - menevo@deq.ufmg.br
Adriana Silva França - franca@deq.ufmg.br
DEQ/UFMG - Rua Espírito Santo 35 - 30160030 - Belo Horizonte, MG, Brazil

It has been known for the past century that, if malignant cells are exposed to temperatures in the range of 42 to 45 o C, the growth of a malignant tumor can be reduced. Therefore, the use of induced hyperthermia has been considered as a treatment for cancer patients. There are two basic forms in which hyperthermia can be employed. The conventional route is by contact with a heated medium, usually a water bath. An alternative route is to apply electromagnetic radiation such as microwaves, in which energy penetrates the body and generates heat internally. This type of treatment can be predicted and evaluated with the aid of numerical simulation. The electric component field of the microwave patterns, which is responsible for heating, can be evaluated by solving Maxwell's equations for electromagnetic wave propagation. In this paper, the electric field distribution obtained from solving these equations was coupled to the energy equation to predict the temperature distribution during microwave heating. A discussion on the applicability of Lambert's law approximation is presented. Simulation results show that the treatment is significantly affected by irradiation direction and intensity, and also by sample size, shape and rotation. The effects of blood perfusion rate were also evaluated.

Keywords: Finite element method, Maxwell's equations, Hyperthermia