Patients will benefit from improved facilities thanks to a multi-million pound investment at Harefield Hospital.

More beds, larger surgery capacity and new buildings are promised at the hospital, in Hill End Road, Harefield, which is one of the world’s largest and most experienced heart and lung transplant centres.

The investment is part of The Royal Brompton and Harefield NHS Foundation Trust expansion plan, worth at least £20million.

Bob Bell, the trust’s chief executive, said: “This substantial investment represents an exciting new era for Harefield Hospital as it approaches its centenary year in 2015.

“The new and improved facilities will help the trust meet increasing demand for the world-class services provided by our clinical teams.

“The hospital is renowned for its ground-breaking treatments for complex heart and lung conditions.

“This investment means more patients will benefit from this lifesaving and life-changing care.”

The cost will be met from funding sources available to the trust, with contributions from the Royal Brompton and Harefield Hospitals Charity.

If planning permission is granted, the improvements will be implemented in three stages over the next five years, with phase one due for completion by the end of next year.

They include more critical care and inpatient beds, better diagnostic imaging and scanning capability and a new operating theatre and endoscopy suite.

Rebuilt wards and a graduated care unit will increase the number of hospital beds to well over 200 from the hospital’s current number of 176.

By 2020 it is hoped the hospital will be able to carry out an extra 380 chest surgeries on the heart, lung and oesophagus, an extra 100 coronary artery bypass grafts and 90 heart valve operations every year.

More beds will also mean increased heart and lung transplants, emergency treatment for heart attacks and electrical device implantation, such as pacemakers.

The hospital said the investment will also enable it to grow its respiratory services, which includes treatment for asthma and severe emphysema and an opportunity to develop an allergy service.