Dr. Trapnell received his medical degree from the University of Maryland in 1985 and medical residency training at The Ohio State University Hospitals. He completed a fellowship in pulmonary medicine and then served as attending physician and senior attending physician at the Clinical Center of the National Institutes of Health. Subsequently, he served as vice president and director of the Division of Pulmonary and Virology Studies at Genetic Therapy, Incorporated, a subsidiary of Novartis.

In 1997, Dr. Trapnell joined Cincinnati Children’s Hospital Medical Center and is now a professor of Medicine and Pediatrics at the UC College of Medicine. At Cincinnati Children's, he directed Cincinnati’s Cystic Fibrosis Therapeutics Development Network Center for more than a decade and participated in numerous clinical trials as principal investigator including studies leading to FDA-approval of Creon® and Pancreaze®. He established and directs the Rare Lung Diseases Clinical Research Consortium (RLDC) in which a study led by Frank McCormack resulted in FDA approval of Sirolimus® as therapy of Lymphangioleiomyomatosis.

Dr. Trapnell’s research group established that GM-CSF autoantibodies caused the rare lung disease autoimmune pulmonary alveolar proteinosis and established clinical laboratory tests for its diagnosis and identified hereditary pulmonary alveolar proteinosis as a new genetic disease caused by mutations in CSF2RA and CSF2RB. His research group developed a novel type of cell transplantation, pulmonary macrophage transplantation, and is currently translating it for testing as therapy in patients with the disease. The group also contributed to the identification, characterization, and methods for diagnosis of indium-related lung disease.

An ardent patient advocate, Dr. Trapnell has worked with patient foundations for cystic fibrosis (CF), alpha-1-antitrypsin deficiency, pulmonary alveolar proteinosis, lymphangioleiomyomatosis, and childhood interstitial lung diseases. He has served as past scientific director for the Alpha-1 Foundation and as co-founder and current scientific director of the Pulmonary Alveolar Proteinosis Foundation. Since coming to Cincinnati, he has provided training in basic, clinical, and translational research at pre- and post-doctoral levels.