Fiction: In the film, Kitai discovers that the Earth's atmosphere has adapted in at least one specific way to discourage human habitation -- there's not enough oxygen to survive. So he must use a futuristic inhaler which, his father explains, will coat his lungs and boost oxygen absorption.

Science: Modern asthma inhalers don't technically increase oxygen absorption into the bloodstream, but they do facilitate lung function by way of two main types of aerosolized medication: Bronchodilators relax muscle constriction, and anti-inflammatory agents suppress inflammation.