A health worker holds the hand of the British pilot at Cho Ray Hospital. (Source: Daily Mail)

He was admitted to the Hospital for Tropical Diseases in Ho Chi Minh City on March 18 and became the country's most-critical patient, with his lung function dropping to just 10 percent. Reports state he is receiving physical therapy twice a day as his recovery continues and his lower limb strength is up to around 40 percent, with his upper limbs at around 60 percent, according to the Daily Mail.

His kidney has now seemingly recovered after he was taken off dialysis on May 27, with consistently positive results from tests for three consecutive days.

The pilot is still using an ECMO (extracorporeal membrane oxygenation) system but the blood rate through the system is down to 3.7 litres per minute, compared to 5.7 litres per minute at his worst condition.

The ECMO pumps bloody out of the body to a machine which carries out the functions of the heart and lungs, removing carbon dioxide and sending oxygen-filled blood back. The team hope to reduce the flow going through the system to 2.5 litres per minute as his lungs begin to play a bigger role in oxygenation.

He remains in a serious condition and doctors are reportedly looking for suitable donors for a lung transplant.

He woke from his coma last week, with Tran Thanh Linh, the deputy head of the hospital saying that he was able to communicate after his doses of muscle relaxants and sedatives had been reduced.

Local media reported the pilot can move his fingers and toes but still has problems breathing. He was declared free of COVID-19 on 21st May and was transferred from the Hospital for Tropical Diseases to his current facility.

The Director of the Administration of Medical Examination and Treatment at Vietnam's Ministry of Health, Luong Ngoc Khue, said the hospital 'fulfilled its mission of treating the British man', said the DailyMail.

The patient had suffered from cytokine storm syndrome when his immune system overreacted to the coronavirus attacking his body and released too many cytokines, damaging his organs.

In his letter of thanks addressed to Ho Chi Minh City People's Committee Chairman Nguyen Thanh Phong, British Consul General Ian Gibbons expressed his gratitude to the Hospital of Tropical Diseases and Cho Ray Hospital for their 'excellent care'.

He wrote: 'They have worked tirelessly and spared no efforts in helping him during the time he has been critically ill in hospital. We have been in very close touch with all the relevant authorities throughout the time he has been so unwell.

'We are in regular contact with his family and close friends. We could not have asked for better treatment. Once again, my sincere and personal thanks to all involved in his care.'