Studies show that victims who receive bystander CPR are twice as likely to survive as those who do not receive any bystander CPR until EMS arrives. In order to facilitate this change local emergency response dispatchers must be trained in recognition of arrest based on witness statements and training must take place on efficient ways to coach bystanders in CPR.
These changes began being implemented in the Seattle area in 1982, and have since been started in many communities around the country. That being said, the training and roll out of dispatcher coached CPR is far from universal across EMS systems, despite the evidence.
Another factor is that, although many communities state that they teach dispatcher assisted CPR, few may teach dispatchers to be aggressive in questioning that will lead to coaching the bystander into doing so. Dispatchers also need to know how to give clear, simple instructions, and how to cut through extraneous verbage in order to get the job done.
This addresses the core public health function of assurance, with the linking of the population to care and assurance of a competent public health (dispatcher) workforce.
Two determinants of public health are at play here- the healthcare realm, in which people are linked to appropriate care, and the social environment, where community members can render assistance to those in need with on the spot coaching.
These changes were implemented based on a retrospective study of case results showing increased survival to discharge rates of victims of cardiac arrest when immediate bystander CPR was performed.
MUCH more on "assertively" training dispatchers to identify need for CPR and begin coaching is on page 29-30 here: http://www.resuscitationacademy.com/downloads/ebook/TenStepsforImprovingSurvivalFromSuddenCardiacArrest-RA-eBook-PDFFinal-v1_2.pdf