Imperial College London

Emeritus ProfessorStephenSemple

Faculty of MedicineNational Heart & Lung Institute

Emeritus Professor of Medicine



+44 (0)20 7594 8192s.semple




102 ( J )Sir Alexander Fleming BuildingSouth Kensington Campus





Stephen Semple is Emeritus Professor at the National Heart and Lung Institute, Imperial College London.

Professor Semple trained London University at St Thomas’s Hospital. After qualification he trained and worked in the Department of Medicine there but in addition, he spent two years as a Medical Specialist in the RAMC (National Service) and two years in The Department of Pharmacology in The University of Pennsylvania, Philadelphia. In 1970 he was appointed to The Middlesex Hospital and Medical School as Head of the Department of Medicine. Later, when the School joined University College London he became Head of the Joint Department of Medicine.

After retirement he was invited by Professor Abe Guz to join the Department of Respiratory Medicine as Visiting Professor of Medicine in the Charing  Cross & Westminster Medical School.  Later in 2001 he was granted the Title of Professor Emeritus of Medicine and Senior Research Investigator at Imperial College London.

His main interest in Research has been in the chemical control of pulmonary ventilation with special reference to the role of carbon dioxide. When he started research the relationship between the mean level of carbon dioxide (PCO2) and Ventilation was well studied. However PCO2 is a signal which oscillates with each breath and initially he started, with colleagues in the Departments of Medicine and Physiology at St Thomas’, to determine if this oscillatory signal, independent of the mean, could influence ventilation. To do this theyhad to develop a rapidly responding intraarterial indwelling pH electrode. Armed with this technical development they found that the peripheral chemoreceptors were sufficiently sensitive to respond to these small oscillations (approx 2mm Hg), and that the response was not simply proportional but contained a large rate of change component. Alteration in the temporal relationship between the oscillations in PCO2 and inspiration produced changes of approximately 20% of breath volume. These and other experiments were carried out in animals so when he joined the Department of Respiratory Medicine here he set about development of the fast response electrode for use in humans in the radial artery. This was a time consuming and a technical challenge requiring initial trials in the peripheral artery of the dog. Eventually this was successful and proved to be safe, and they have gone on to record arterial pH in the intensive care unit and the sleep laboratory here at the Charing Cross campus. In a group of normal subjects we used the electrode in experiments in defining the apnoea threshold at sleep onset.

More recently he was one of the investigators in a study of the use of cannabinoids for the amelioration of breathlessness induced by carbon dioxide in the laboratory.  Based on the neurophysiology of dypsnoea and the distribution of cannabis receptors within the central nervous system, the hypothesis was that the unpleasantness of breathlessness would be ameliorated in humans by cannabinoids without respiratory depression. They carried out a pilot study on ten subjects, four of which were patients with chronic obstructive pulmonary disease (COPD). Breathlessness was assessed using a visual analogue scale (VAS) and their response to a group of eight respiratory descriptors. No difference in breathlessness VAS scores were found after placebo or drug. After drug administration, COPD patients picked air hunger breathlessness descriptors less frequently compared to placebo. This interesting observation suggests cannabinoids might ameliorate breathlessness in patients with COPD but will need to be followed up in a larger group of patients.

In teaching, Professor Semple does a weekly ward based teaching round from October to May. He lectures the first year students on the Life Support System and this year he is joint course leader for the respiratory section of that course.

In 2009, Professor Semple was awarded The British Thoracic Society Medal for that year.


Pickering EE, Semple SJ, Nazir MS, et al., 2011, Cannabinoid effects on ventilation and breathlessness: A pilot study of efficacy and safety, Chronic Respiratory Disease, Vol:8, ISSN:1479-9723, Pages:109-118

Thomson S, Morrell MJ, Cordingley JJ, et al., 2005, Ventilation is unstable during drowsiness before sleep onset, Journal of Applied Physiology, Vol:99, ISSN:8750-7587, Pages:2036-2044

Cordingley JJ, Palazzo MG, Thomson S, et al., 1998, A fast responding intra-arterial pH electrode for use in the peripheral artery of adult humans and large mammals: a technical development for use in research., J Med Eng Technol, Vol:22, ISSN:0309-1902, Pages:233-240


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