When Della was diagnosed with sickle cell trait, it appeared nothing could be done. However, Gregory House came up with a crazy idea - transplant a lobe of a lung from Hugo to Della. This would save Della's life, but would severely lessen Hugo's lifespan. However, Lisa Cuddy forbade House from giving the parents the option.
As Della was dying, George sought out House and asked if there was anything at all that could be done. Despite Cuddy's orders, House told him about using one of Hugo's lungs, but also told him about the risk to Hugo.
George and Claire argued about what they had been told, and when Della heard them arguing, she realized Hugo was involved and tried to commit suicide to keep them from trying it. However, George and Claire finally agreed that they would not risk Hugo. However, this started an argument between House and Cuddy about the ethics of the situation. Hugo overheard them, realized what it was about, and went to Della to offer his lung knowing it would shorten his own life.