The Case

A 71-year-old man presents to the emergency department after a ground-level fall. He has a history of hypertension and benign prostatic hypertrophy. His vital signs are all normal, and he declines any pain medication. Investigations reveal rib fractures on the right side. Guidelines recommend admitting him, but he would like to go home.

Clinical Question

In patients 60 years of age and older and with three or more rib fractures, can spirometry identify those who can safely be discharged home from the emergency department?

Background

Older patients often present to the emergency department with traumatic rib fractures. These injuries can lead to life-threatening complications such as pneumonia, pneumothorax, and acute respiratory distress syndrome. The Western Trauma Association guidelines recommend admitting patients older than 65 years of age with two or more rib fractures to an ICU or other step-down monitored setting (see Figure 1).¹

There are some studies suggesting that early spirometry may be a useful prognostic indicator in patients with multiple rib fractures.² Spirometry measurements include forced vital capacity (FVC), peak expiratory flow (PEF), forced expiratory volume in 1 second (FEV1), and negative inspiratory force (NIF). While PEF has not been demonstrated to be closely correlated with patient outcomes, it remains possible that spirometry could be used to identify patients who could avoid unnecessary hospitalization and be discharged home.³ However, these studies were all limited by their retrospective observational nature.

Reference: Schuster KM, Sanghvi M, O’Connor R, et al. Spirometry not pain level predicts outcomes in geriatric patients with isolated rib fractures. J Trauma Acute Care Surg. 2020;89(5):947-954.

• Population: Patients 60 years of age and older admitted to the hospital with at least three rib fractures within 24 hours of injury.
• Exclusions: Injury occurred greater than 24 hours before presentation, significant additional musculoskeletal injury, or cognitive impairment and able to cooperate with testing.
• Exposure: Spirometry measuring (FVC, FEV1, and NIF).
• Comparison: Handgrip strength to assess frailty and pain measured on a visual analog scale (VAS).
• Outcomes:
  • Primary Outcomes: Discharge disposition and length of stay (LOS).
  • Secondary Outcomes: Mortality, pneumonia, intubation, unplanned transfer to higher level of care, and readmission (within 30 days).
  • Authors’ Conclusions

“Spirometry measurements early in the hospital stay predict ultimate discharge home, and this may allow immediate or early discharge. The impact of pain control on pulmonary function requires further study.”

Key Results

There were 346 patients over the age of 60 with isolated rib fractures requiring admission to the hospital. Of those, 260 met the exclusion criteria. This resulted in a cohort of 86 patients with a mean age of 77 years that was 50 percent female. Just over half (45 of 86) were admitted to the step-down unit, 19 of 86 (22 percent) to the ICU, and 22 of 86 (26 percent) to the surgical floor. The mechanisms of injury were falls (54 percent), motor vehicle collisions (45 percent), or motorcycle collisions (1 percent). The median number of fractured ribs was five. Pneumothorax was present in 5 percent and hemothorax in 4 percent of the patients included in the analysis. One patient out of 86 died (1.2 percent).

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.

Bottom Line

The use of spirometry as a simple prognostic tool for older patients with multiple rib fractures is interesting. However, there is not enough high-quality evidence for it to guide us in discharging patients home from the emergency department at this time.

Case Resolution

You perform a spirometry, and the patient’s FEV1 is 64 percent of predicted. This provides a baseline but does not affect your decision to admit him to hospital on a monitored bed with the hope that he can be discharged home within the next 24 to 48 hours.

Thank you to Dr. Emil Iversen, an emergency medicine resident at the University Hospital of Zealand and vice-chair of the Danish Society for Emergency Medicine, for his help with this review.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References

1. Brasel JK, Moore EE, Albrecht RA, et al. Western trauma association critical decisions in trauma: management of rib fractures. J Trauma Acute Care Surg. 2017;82(1):200-203.
2. Sadler CA, Burgess JR, Dougherty KE, et al. Bedside incentive spirometry predicts risk of pulmonary complication in patients with rib fractures. Am Surg. 2019;85(9):1051-1055.
3. Butts CA, Brady JJ, Wilhelm S, et al. Do simple bedside lung function tests predict morbidity after rib fractures? Am J Surg. 2017;213(3):473-477.
4. Cook AC, Joseph B, Inaba K, et al. Multicenter external validation of the Geriatric Trauma Outcome Score: a study by the Prognostic Assessment of Life and Limitations After Trauma in the Elderly (PALLIATE) consortium. J Trauma Acute Care Surg. 2016;80(2):204-209.
5. Hoenig JM, Heisey DM. The abuse of power: the pervasive fallacy of power calculations for data analysis. Am Stat. 2001;55(1):19-24.
6. Althouse AD. Post hoc power: not empowering, just misleading. J Surg Res. 2021;259:A3-A6.
7. Dziak JJ, Dierker LC, Abar B. The interpretation of statistical power after the data have been gathered. Curr Psychol. 2020;39(3):870-877.
8. Livingston DH, Shogan B, John P, et al. CT diagnosis of rib fractures and the prediction of acute respiratory failure. J Trauma. 2008;64(4):905-911.