Lifebreath (1997)

Luke Perry stars in this surprisingly moving adult drama about a devoted husband whose wife (Francie Swift) is dying of cystic fibrosis. Because of her rare blood type, she can't get new lungs, so Perry begins a frantic search to find a donor. Eventually, he becomes so desperate that he starts having an affair with a real-estate agent (Gia Carides) whom he plans to murder because she's a match with Swift and has signed her donor card.