BackgroundTraumatic rib fracture is associated with a high morbidity rate and identifying patients at risk of developing pulmonary complications (PC) can guide management and potentially decrease unnecessary intensive care admissions. Therefore, we sought to assess and compare the utility of a physiologic parameter, vital capacity (VC), with the admission radiologic findings (RibScore) in predicting PC in patients with rib fractures. MethodsThis is a single-center retrospective review (2015–2018) of all adult (≥18 years) patients admitted to a Level I trauma center with traumatic rib fracture. Exclusion criteria included no CT scan and absence of VC within 48 h of admission. The cohort was stratified into two groups based on presence or absence of PC (pneumonia, unplanned intubation, unplanned transfer to the intensive care unit for a respiratory concern, or the need for a tracheostomy). Multivariable logistic regression models were constructed to identify predictors of PC. ResultsA total of 654 patients met the inclusion criteria of whom 70 % were males. The median age was 51 years and fall (48 %) was the most common type of injury. A total of 36 patients (5.5 %) developed a pulmonary complication. These patients were more likely to be older, had a higher ISS, and were more likely to require a tube thoracostomy placement. On multivariable logistic regression, first VC ≤30 % (AOR: 4.29), day 1 VC ≤30 % (AOR: 3.61), day 2 VC ≤30 % (AOR: 5.54), Δ(Day2-Day1 VC) (AOR: 0.96), and RibScore ≥2 (AOR: 3.19) were significantly associated with PC. On discrimination analysis, day 2 VC had the highest area under the receiver operating characteristic curve (AuROC), 0.81, and was superior to first VC and day 1 VC in predicting PC. There was no statistically significant difference in predicting PC between day 2 VC and RibScore. On multivariable analysis, first VC ≤30 %, day 1 VC ≤30 %, day 2 VC ≤30 %, and admission RibScore ≥2 were associated with prolonged hospital and ICU LOS. ConclusionVC and RibScore emerged as independent predictors of PC. However, VC was not found to be superior to RibScore in predicting PC. Further prospective research is warranted to validate the findings of this study.