His primary research focus is in the area of cardiovascular emergencies, especially resuscitation science and diagnostic decisions for potential Acute Coronary Syndromes. He currently is a Co-Principal Investigator and past Chair of the Steering Committee for the Canadian Resuscitation Outcomes Consortium which aims to improve care through early interventions in cardiac arrest and trauma across Canada. He is also the Principal Investigator of a neuroprotective intervention given by paramedics to patients with severe stroke (The FRONTIER Trial). Dr. Christenson leads a team that built and launched the BC Emergency Medicine Network (EMN) to facilitate knowledge sharing and clinical support for all emergency practitioners in British Columbia. It is growing quickly and changing the way physicians communicate about new knowledge and practice change. The EMN is currently funded by CIHR to improve emergency care in 4 Nuu Chah Nuulth remote communities on the west coast of Vancouver Island.

He has been a volunteer for the Heart and Stroke Foundation of Canada for over 30 years and is currently the chair of the Resuscitation Advisory Committee.