Review of: Shy D, Rea T, Becker L, et al: “Time to intubation and survival in prehospital cardiac arrest.” Prehospital Emergency Care. 8(4):394-399, 2004.
This study from King County in Washington examined cardiac arrest records for a 12-year period from 1991 to 2003. The authors recorded the time from patient collapse until intubation and survival rate. They found that those patients that were intubated within 12 minutes had a survival rate of 46%, while those intubated after 13 minutes had a survival rate of 23%. The authors conclude that earlier intubation is associated with higher survival rate.
Just because one action is “associated” with another does not prove cause and effect. If you examine this study more closely, you see that all patients received BLS by EMT-Basics within four to six minutes. The major cause for delay in intubation was the delay in arrival of the paramedics. Also, patients intubated after 12 minutes were more likely to be in asystole, which is going to have a dismal survival rate despite intubation. The authors contend they took these factors into consideration, but I don t see it in the paper.
Additionally, Washington state EMT-Basics do not have advanced-airway training and therefore must rely on BVM airway management alone. This paper may represent more of a need for better BLS airway management than faster paramedics with ET tubes.
While I respect the passion for which these authors have approached the analysis of cardiac arrest, in the past, recent data suggest that intubation in and of itself is not associated with increased survival. We know that chest-compression-only CPR with an open and patent airway works, and airway management can interrupt chest compressions and increase intrathoracic pressures, both of which are associated with lower rates of survival.