A cigarette smoker takes a deep drag and holds it, waiting to feel the tingle of nicotine hitting the bloodstream. It's not a pretty picture if we care about our health. Nevertheless, says Jeffrey Hammersley, M.D., the smoker is on to something: "The airway is an excellent way to administer drugs. You get rapid transmission of vapors and small particles deep into the lung and almost instant absorption into the bloodstream."
Take cardiac arrhythmia, for instance. Many people with dangerously irregular heartbeats carry an "autoinjector" of antiarrhythmic medication, typically lidocaine, for jabbing into their thigh when their heart acts up. In three to four minutes, the heart usually calms down. For some, however, three to four minutes may be too late. In the future, Hammersley and his colleagues expect that inhalers will speed lidocaine from the lungs to the heart in 10-15 seconds.
Other potential inhaled medications include insulin for diabetics and antibiotics to treat chronic infections that now require injections. When the lung is the target of medication, inhaling requires less total medication and less frequent doses, reducing side effects and cost, and it should be possible to extend these benefits to other drugs. "If you could also deliver antibiotics or insulin through the airways," says Hammersley, "you have the potential to eliminate the risk and discomfort of needles and immensely reduce treatment costs for a wide range of diseases."
Hammersley is a lung specialist at the Medical College of Ohio, and he combines his medical knowledge with engineering training in fluid dynamics. Using the CRAY C90 at the Pittsburgh Supercomputing Center, he has begun to create a computational model of airflow in the lungs. He collaborates with colleagues in engineering and computer science at the University of Arkansas, the NSF Engineering Research Center at Mississippi State and the University of Toledo. Together they have converted computational fluid dynamics (CFD) techniques used in the design of cars, airplanes and aerospace vehicles for use in the complex branching geometry of the lung's small airways.
These graphical results from 3-D lung airflow modeling on the CRAY C90 depict flow velocity at selected cross-sections in a single bifurcation. Velocity (in dimensionless units) ranges from zero (black) through dark blue to red to maximum (white).
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