Following an air ambulance crash with five fatalities, critical incident stress debriefing (CISD) was provided for involved paramedics, physicians, and nurses. A study was conducted to evaluate the long-term effects of a critical incident with critical incident stress debriefing according to the Mitchell model.

Six months following the incident, empirically designed questionnaires were mailed to all transport paramedics and directly involved medical staff, and a random sample of both nurses from the dispatch/receiving institution and paramedics from around the province. Twenty-four months post-incident, all members of the transport paramedics completed the Impact of Events Scale and the General Health Questionnaires.

There were no differences between groups on any scores, except for disturbed sleep patterns, bad dreams, and the need for personal counseling being greater among transport paramedics at one day. There was no correlation between how well the deceased individuals were known, amount of debriefing, and symptom severity. A trend was seen for those with pre-existing stress management routines to have less severe symptoms at six months (p = 0.07). At two years, 16% of transport paramedics still had significant abnormal behavior.

CISD did not appear to affect the severity of stress symptoms, whereas having pre-existing stress management strategies may. These findings give justification for proceeding to a randomized, controlled trial of different levels of critical incident stress intervention.