He was pulled from the cold river in cardiac arrest but was saved by a treatment that oxygenated and warmed his blood.
The Great North Air Ambulance Service (GNASS) worked with fire crews, police and ambulance staff to save the teen's life, after the incident in Appleby, Cumbria.
One of the most significant factors in Kacper's survival was the use of Extracorporeal Membrane Oxygenation (ECMO).
The ECMO machine is able to carry out the functions of both the heart and lungs, to provide blood flow and oxygen to the body. A cannula tube takes the patient's blood out of a large vein, to pass through the machine.
The machine is also able to warm the blood, which was important as Kacper's body temperature had cooled significantly while submerged in the river.
Dr Gospel, aircrew doctor and clinical fellow in paediatric intensive care at the Freeman Hospital in Newcastle, was part of the team responsible for delivering the ECMO therapy in hospital.
DailyMail