tthew Heui-Ming Ma

Basic life support equipped with automated external defibrillator may not be categorized the same as traditional basic life support in meta-analysis.

We read with great interests the meta-analysis reported by akalos et al.1 comparing patient survival with advanced life suport (ALS) versus basic life support (BLS) in the pre-hospital setting nd would like to present our opinions on its appropriateness for on-traumatic cardiac arrest. An emergency medical services (EMS) system that provides BLS quipped with rapid defibrillation (BLS-D with automated exteral defibrillator) should not be placed in the same category as an MS that provides BLS without a defibrillation capacity. Based on he contribution of early defibrillation to patient outcomes, a mixure of the two may result in misclassification and measurement ias. We recently presented as an abstract, several years of data omparing ALS versus BLS-D,2 and previously reported a one-year ata analysis.3 Including ours, there were only three large commuity studies comparing ALS versus BLS-D in a modern EMS.4,5 In he meta-analysis reported by Bakalos et al., all these three studes were mixed with other earlier studies that compared ALS with raditional BLS without defibrillation capability. In addition, among the other six studies out of the final nine ncluded in the meta-analysis (Table 3 in the article)1: Olasveengen t al. compared ALS with physicians versus ALS without physicians, nd not ALS versus BLS; Soo et al. described their paramedics as LS level but that was not adequately counted as ALS data in the eta-analysis; Mitchell et al. compared an EMS consisting of BLS/ALS/physician with another EMS of BLS-D/ALS, not ALS versus LS; Dickson et al. compared one-year data of ALS with physicians ersus ALS without physicians, not ALS versus BLS. Therefore, the o-called BLS data listed in Table 3 of the article is a mixture of traitional BLS, BLS-D, and even different forms of ALS, and again meaurement bias might occur. We suggest that the numerators (numer of survivors at hospital discharge) and the denominators (numer of patients receiving ALS or BLS care) in Table 3 be re-evaluated.