Time-Dependent Association of Thoracic Anthropometric Parameters with Survival After In-Hospital Cardiac Arrest: A Retrospective Single-Center Observational Study

Background: Current cardiopulmonary resuscitation (CPR) guidelines recommend a uniform chest compression depth (5–6 cm) for all adults, disregarding anatomical variability. The primary objective was to determine whether thoracic anthropometric parameters are associated with 28-day mortality after in-hospital cardiac arrest (IHCA); the secondary objective was whether these associations vary with CPR duration. Methods: In this retrospective single-center cohort, 431 adults with IHCA and available chest computed tomography (CT) were analyzed. Body mass index (BMI), internal anteroposterior diameter (IAPD), and external anteroposterior diameter (EAPD) were measured. Patients were stratified by CPR duration (≤5, 5–10, >10 min), and multivariable logistic regression with interaction terms tested time-dependent effects on 28-day mortality. Results: Overall 28-day survival was 40.8% (176/431). During the early phase (≤5 min), higher BMI, IAPD, and EAPD were each associated with increased mortality, and underweight patients had lower mortality than normal-weight and overweight patients. These anatomical associations attenuated and lost significance during prolonged resuscitation (>10 min), when CPR duration dominated outcomes. Conclusions: The prognostic value of body composition after IHCA is time-dependent, being greatest during the first five minutes, supporting individualized, body composition-guided chest compression—particularly using readily available BMI—during early resuscitation.