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ACEP Now: Vol 40 – No 05 – May 2021

Figure 1: Western Trauma Association rib fracture algorithm.

Higher spirometry values and grip strength were associated with early discharge from the hospital

Outcomes:

• Primary Outcomes: Discharge disposition and LOS
  • The FEV1 adjusted odds ratio (aOR) was 1.03 (95 percent confidence interval, 1.01–1.06; P=0.001).
  • Grip strength was also significantly associated with being discharged home.
  • FVC and NIF values were not statistically significant in providing prognostic information.
  • Pain score was poorly predicative of hospital LOS.
• Secondary Outcomes: A few patients experienced some of the secondary outcomes of interest (n). This included mortality (1), pneumonia (2), intubation (1), unplanned transfer to higher level of care (3), and hospital readmission within 30 days (3).
• Evidence-Based Medicine Commentary

1. Selection Bias: All patients were screened except when an investigator was unavailable. Three-quarters of patients (260 of 346) were excluded for a variety of reasons, but no breakdowns were provided in the manuscript. This introduces the possibility of selection bias that may impact the results.

2. Power: There was no formal power calculation prior to the study, though the authors say a “rough” estimate to find a difference between the two groups would have been about 400 patients. It is unclear exactly how they arrived at this number. They did estimate a complication rate of about 20 percent based on the Geriatric Trauma Outcome Score, which is calculated by taking the patients age + (injury severity score x 2.5) + 22 (if given packed red blood cells by 24 hours).⁴

Older patients often present to the emergency department with traumatic rib fractures.

It is good practice to do a power calculation when planning a research project. Moreover, doing a post-hoc power (PHP) calculation can be misleading. It is better just to look at the confidence interval around the point estimate. Looking backwards with a PHP calculation does not help interpret the results.^5–7

3. Blinding: The investigators in this study were not blinded. Although spirometry seems like an objective measurement, it does require significant instructing of the patient. The fact that the same investigator performed both the pain assessment and the spirometry could have introduced “coaching bias.” Coaching bias could be conscious or unconscious. It may have occurred when investigators failed to encourage patients equally depending on their perceived level of pain.

4. Rib Fractures: Rib fractures are missed on initial chest X-ray in up to 50 percent of cases. One rib fracture on chest X-ray is associated with a high risk of multiple rib fractures.⁸ In this study, all but four patients had their injuries identified by CT scan. This suggests that there could have been denominator neglect (ie, some patients may have been discharged from the emergency department with undiagnosed multiple rib fractures). The authors did not screen 322 acutely injured patients who were discharged directly from the emergency department. Three were believed to have subacute rib fractures by imaging characteristics.

5. Follow-up: Secondary outcomes included pneumonia, readmission, and mortality at 30 days. Very few patients were observed to have any of these outcomes. It is possible that some patients deteriorated more gradually and that these secondary outcomes were not captured within the one-month time frame.