Thursday, July 19, 2007

Hearts and Lungs

Adventures in the OR
Since my last post, I have seen quite a few operations. The one I found particularly interesting was an arterial switch (known as a Jatene procedure), which is performed within the first two weeks of the patient's life. The purpose is to repair dextro-transposition of the great arteries: a congenital defect in which the pulmonary artery and the aorta are transposed. In other words, the aorta is where the pulmonary artery should connect to the heart, and vice versa. What effect does this have on the body? I'm glad you asked. Essentially, it results in two circulatory loops: one that pumps the blood continuously through the lungs, and the other that bypasses the lungs altogether. As a result, oxygenated blood will not be distributed to the body.

I watched Dr. Jonathan Chen from Cardiothoracic Surgery perform this operation on one of the patients from the neonatal ICU. I was very fortunate to be able to witness such a long, arduous surgery, and I was very impressed at the level of orchestration compared to some of the previous surgeries I have seen. Dr. Chen required almost complete silence during most of the operation, which is something I found out the hard way...

Change of Direction
Regarding my work with Dr. Frayer, I have begun looking into computational fluid dynamics as a new direction for the lung model. The original model was based on a lumped parameter circuit analog, but we decided to abandon it for a number of reasons. For example, although such models can be fitted to clinical data, they lack the predictive power that can be achieved with a 3D CFD model, particularly for studying the upper airways. Also, it assumes homogeneous ventillation to the acinar units of the lungs, which is a poor assumption especially when we are interested in modeling how the acinar units are ventillated.

I have begun working with Fluent, which is a popular CFD software package. I spent the last couple days working through tutorials for both Fluent and Gambit (Fluent's 3D modeling program). So far I haven't made much progress. The picture shown below is supposed to be a trachea with the two primary bronchi.

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