Tommy was extremely injured and the anesthesia wasn't working and he continued fighting and you came grabbed the anesthesia mask and started breathing in front of him and the others you were showing tommy to breath in the gas

Wilbur: "What are you doing?"

you didn't respond and put the mask over tommys mouth he didn't breath it and you breath it again

Tubbo: "What's she doing"

you put the mask over his face again and he finally breathed it and fell asleep

Ranboo: "care to explain?"