1 Sepsis. 2  The most common cause of ARDS is sepsis, a serious and widespread infection of the bloodstream. 3  Inhalation of harmful substances. 4  Breathing high concentrations of smoke or chemical fumes can result in ARDS, as can inhaling (aspirating) vomit.ronchioles and alveoli. The mechanical cause of ARDS is fluid leaked from the smallest blood vessels in the lungs into the tiny air sacs where blood is oxygenated. Normally, a protective membrane keeps this fluid in the vessels.