Leonard M. Sieracki, an engineer who was co-inventor of a medical breathing system that optimized the intake of oxygen in patients, died June 27 at Anne Arundel Medical Center in Annapolis. He was 72.

He had complications from Parkinson’s disease, said his son, Jeff Sieracki.

Mr. Sieracki founded TriTec, a Columbia-based corporation that specialized in fluidic systems, in 1977. He helped develop the gas-supply method and apparatus for the demand oxygen controller (DOC), a system that delivers oxygen to patients when they inhale, as opposed to providing continuous oxygen flow.

The oxygen-saving mechanism has been used in aviation equipment and hospital breathing-assistance devices, his son said. On behalf of his company, Mr. Sieracki received an awarwd in 1981 from Industrial Research magazing for his work on the demand oxygen controller.

In 1991, Mr. Sieracki sold TriTec and founded Manx Motors, a now-defunct kit-car company in Columbia. He closed the business in 1993 and moved to Olney in 2010.

Leonard Mark Sieracki was born in Meriden, Conn. He received a bachelor’s degree in 1963 and a master’s degree in ocean engineering in 1964, both from Catholic University. He received a master’s degree in business administration from Johns Hopkins University in 1977.

Early in his career, he founded and managed Lorelei Corp., an engineering consulting business in Gaithersburg.

After his Parkinson’s diagnosis at age 43, Mr. Sieracki founded a young-onset Parkinson’s disease support group at Johns Hopkins Hospital in 1986, his son said.

Survivors include his wife of 48 years, Martha Shermeta Sieracki of Olney; four children, Jeffrey Sieracki of Clarksville, Jennifer Burke of Annapolis, Julie Jordan of Denver and Kathryn Koczot of San Diego; a sister; and six grandchildren.

— Megan McDonough