Out of Hospital Cardiac Arrest (OHCA) can be the first sign of heart disease in about 25% of patients. It happens suddenly and in many cases in people who appear healthy. OHCA also occurs in patients with known heart disease who have warning signs such as chest pain, jaw aching, shortness of breath or “palpitations”.  OHCA essentially means the heart stops beating and patients are “vital signs absent” or VSA. Without immediate action the chance of survival decreases rapidly, thus triggering 911 is paramount, but what does it trigger and how does it affect survival?

In 1994 studies began in Ontario to determine what affects the survival of patients with an OHCA. From 1994 to 2004 Thunder Bay Regional Hospital’s Base Hospital program in conjunction with Superior North EMS (SNEMS) and Thunder Bay Fire Rescue took part in a series of monumental studies called the Ontario Prehospital Advanced Life Support studies (OPALS). These studies involved 13 cities, 9 EMS services and 13 fire departments serving a population of 3 million. One of the main arms of the study centred on determining what affects the survival in OHCA using “Advanced Life Support” (ALS) tools in addition to rapid defibrillation (shocking the heart). An energetic and dedicated group of paramedics from SNEMS underwent training to upgrade from Primary Care Paramedics to Advanced Care Paramedics. The Base Hospital Program’s role was to educate, train and to oversee the “delegated medical acts” the paramedics undertook.  The EMS service provided rapid response with Advanced Life Support tools and the Fire Service provided rapid CPR and defibrillation. This was all coordinated through the “tiered response” program involving 911 as well as ambulance and fire dispatchers.  With the cooperation of all those involved Thunder Bay quickly became recognized as a major contributor to the province wide OPALS’s studies.

Due to the success of the OPALS studies a North American consortium was created in 2004 called the Resuscitation Outcome Consortium (ROC). The consortium was made up of 268 fire and EMS services, 30,000 EMS personnel covering a population of 24 million people in Canada and the USA. ROC continued from 2004 to 2016.

So, what did the OPALS and ROC studies find?

  1. Survival from OHCA was dependent on two factors: CPR and time to defibrillation (shocking the heart)
  2. CPR was often not being performed according to guidelines
  3. A higher chest compression rate (105 compressions per minute) with a 2-inch compression resulted in a better outcome
  4. The use of medications in OHCA have yet to show any benefit, studies are ongoing

What did this mean in Thunder Bay?

In Thunder Bay survival from OHCA increased from 3.5% up to 9% over the two decades of studying OHCA. With 120 vital signs absent (VSA) calls a year this means 6 to 7 more lives per year have been saved in Thunder Bay as a result of these studies.

After the ROC trials were completed, physicians interested in “resuscitation medicine” from across Canada created CanROC in 2016 ( In May of this year CanROC put the finishing touches on a nation-wide OHCA registry. Having such a registry will allow us to further optimize survival in OHCA.

Northern Hearts invites readers to watch for next month’s Heart Beats column providing further information on the importance of CPR during infectious disease outbreaks such as COVID as well as well as the use of public access defibrillation (PAD).

Submitted by Dr. Andrew Affleck CCFP(EM) FIFEM, Emergency Physician, Past Medical Director Northwest Region Prehospital Care Program, Northern Hearts Board member