Professor Steier's research is specialised in respiratory physiology, sleep-disordered breathing and the development of new treatments for sleep apnoea. He advises patient charities (Hope2Sleep, British Lung Foundation) and is member of the editorial board of the Journal of Thoracic Disease and associate editor of BMJ Open Respiratory Research. He has previously been been involved with formal roles for the British Thoracic Society (BTS) and the European Respiratory Society (ERS), and currently serves on the executive committee of the British Sleep Society (BSS) as immediate Past President. His current research programme on "Transcutaneous Electrical Stimulation in Obstructive Sleep Apnoea" (TESLA) and patient based physiological markers of respiratory symptoms and effort recruits for several clinical trials. Besides numerous peer-reviewed scientific publications Professor Steier has edited several text books on lung function and physiotherapy, and multiple book chapters in the field of Respiratory, Sleep and Critical Care Medicine.

Professor Steier's training in medicine commenced at the University of Leipzig in Saxony. Following graduation, he worked on his MD thesis entitled “Transthoracic Echocardiography in Pulmonary Hypertension” and gathered work experience in Zurich (CH), at the University of Alabama in Birmingham (US) and in Bavaria (D). His respiratory training led him to the Western German Lung Centre at the University of Essen. His interest in respiratory physiology and sleep-disordered breathing led him to London on a long-term research fellowship of the European Respiratory Society (ERS). His studies concluded in the PhD thesis on "Sleep-Disordered Breathing and the Respiratory Muscles” at King’s College London. His projects with the London Respiratory Physiology group resulted in research publications with involvement in an impact case,  the development of new intellectual property (ce-marked product), and the founding of a new company. His work in the field of respiratory and sleep physiology has evolved into collaborations across the world. Professor Steier works as Consultant at Guy’s & St Thomas’ NHS Foundation Trust in the Lane Fox Unit, a tertiary service for weaning and non-invasive ventilation. He is also placed at the British Sleep Society (BSS) accredited Sleep Disorders Centre at King’s Health Partners. He was awarded the chair for Respiratory and Sleep Medicine at King’s College London. He is member of the executive committee of the British Sleep Society (BSS) since 2017, President 2019-2023, and now Past President.