Risk factors that predict mortality in patients with blunt chest wall trauma: a systematic review and meta-analysis

Background: The risk factors for mortality following blunt chest wall trauma have neither been well established or summarised.

Objective: To summarise the risk factors for mortality in blunt chest wall trauma patients based on available evidence in the literature.

Data sources: A systematic review of English and non-English articles using MEDLINE, EMBASE and the Cochrane Library from their introduction until May 2010. Additional studies were identified by hand-searching bibliographies and contacting relevant clinical experts. Grey literature was sought by searching abstracts from all Emergency Medicine conferences. Broad search terms and inclusion criteria were used to reduce the number of missed studies.

Study selection: A two step study selection process was used. All published and unpublished observational studies were included if they investigated estimates of association between a risk factor and mortality for blunt chest wall trauma patients.

Data extraction: A two step data extraction process using pre-defined data fields, including study quality indicators.

Study appraisal and synthesis: Each study was appraised using a previously designed quality assessment tool and the STROBE checklist. Where sufficient data were available, odds ratios with 95% confidence intervals were calculated using Mantel-Haenszel method for the risk factors investigated. The I(2) statistic was calculated for combined studies in order to assess heterogeneity.

Results: Age, number of rib fractures, presence of pre-existing disease and pneumonia were found to be related to mortality in 29 identified studies. Combined odds ratio of 1.98 (1.86-2.11, 95% CI), 2.02 (1.89-2.15, 95% CI), 2.43 (1.03-5.72, 95% CI) and 5.24 (3.51-7.82) for mortality were calculated for blunt chest wall trauma patients aged 65 years or more, with three or more rib fractures, pre-existing conditions and pneumonia respectively.

Conclusions: The risk factors for mortality in patients sustaining blunt chest wall trauma were a patient age of 65 years or more, three or more rib fractures and the presence of pre-existing disease especially cardiopulmonary disease. The development of pneumonia post injury was also a significant risk factor for mortality. As a result of the variable quality in the studies, the results of the selected studies should be interpreted with caution.