Two-year-old Maisie Harris leaves hospital for the first time
7 October 2013 Last updated at 12:11 BST
Maisie Harris is connected to a ventilator 24 hours a day.
She suffers from a genetic disorder which means her brain does not send the right messages to her lungs in order to breathe.
Now just weeks away from turning three, she is heading home for the first time in her life because her ventilator has become portable. It has batteries and a carry-case so Maisie will be able to go on outings with her family and go to school when she is older.
Graham Satchell went to see her leaving hospital and spoke to her parents Andrew and Rachel, and Kate Harkus from Great Ormond Street Hospital.