University of Washington School of Public Health and Community Medicine, Department of Epidemiology, Seattle, WA, USA.
Resuscitation. 2010 May;81(5):622-5. doi: 10.1016/j.resuscitation.2010.02.004. Epub 2010 Mar 6.
We examined the relationship between time from collapse to arrival of emergency medical services (EMS) and survival to hospital discharge for out-of-hospital ventricular fibrillation cardiac arrests in order to determine meaningful interpretations of this association.
We calculated survival rates in 1-min intervals from collapse to EMS arrival. Additionally, we used logistic regression to determine the absolute probability of survival per minute of delayed EMS arrival. We created a logistic regression model with spline terms for the time variable to examine the decline in survival in intervals that are hypothesized to be physiologically relevant.
The observed data showed survival declined, on average, by 3% for each minute that EMS was delayed following collapse. Survival rates did not decline appreciably if the time between collapse and arrival of EMS was 4 min or less but they declined by 5.2% per minute between 5 and 10 min. EMS arrival 11-15 min after collapse showed a less steep decline in survival of 1.9% per minute. The spline model that incorporated changes in slope in the time interval variable modeled this relationship more accurately than a model with a continuous term for time (p=0.01).
The results of our analyses show that survival from out-of-hospital cardiac arrest does not decline at a constant rate following collapse. Models that incorporate changes that reflect the physiological alterations that occur following cardiac arrests are a more accurate way to describe changes in survival rates over time than models that include only a continuous term for time.
我们研究了院外室颤性心脏骤停患者从心脏骤停到紧急医疗服务（EMS）到达的时间与存活至出院之间的关系，以便确定对这种关联的有意义的解释。
我们计算了从心脏骤停到 EMS 到达的每 1 分钟的存活率。此外，我们使用逻辑回归来确定每延迟 1 分钟 EMS 到达的绝对存活概率。我们创建了一个带有时间变量样条项的逻辑回归模型，以检查假设在生理相关的间隔内存活的下降。
观察数据显示，在 EMS 延迟到达后的每 1 分钟，平均存活下降 3%。如果心脏骤停与 EMS 到达之间的时间间隔为 4 分钟或更短，则存活下降不会明显下降，但如果时间间隔为 5 至 10 分钟，则每分钟下降 5.2%。EMS 在心脏骤停后 11-15 分钟到达时，存活下降的斜率较小，为每分钟 1.9%。包含时间间隔变量斜率变化的样条模型比包含时间连续项的模型更准确地描述了这种关系（p=0.01）。
我们的分析结果表明，院外心脏骤停后的存活并不以恒定的速率从心脏骤停后下降。包含反映心脏骤停后发生的生理变化的变化的模型比仅包含时间连续项的模型更能准确描述随时间变化的存活率变化。
