1. Department of Thoracic Surgery, The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE, UK
2. Department of Anaesthesia, The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE, UK
3. Department of Pulmonary and Oesophageal Physiology, The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE, UK