Perioperative changes in diaphragm thickening fraction in cardiac surgery patients

Diaphragmatic dysfunction is a recognized contributor to postoperative respiratory complications following cardiac surgery. Diaphragm ultrasonography has been proposed as a bedside tool to assess diaphragm function. In this prospective study, 133 patients undergoing elective cardiac surgery were evaluated. Diaphragm thickening fraction (TF) was measured using ultrasound one day before and one day after surgery. The perioperative change in TF (ΔTF) was also calculated. The primary outcome was ICU length of stay. Multivariable linear regression analysis was performed to assess independent associations. Postoperative TF values decreased compared to preoperative measurements. In unadjusted analyses, diaphragm thickening fraction was not significantly associated with extubation time or ICU length of stay. Multivariable analysis demonstrated that cardiopulmonary bypass time and cross-clamp duration were independently associated with ICU stay, whereas diaphragm thickening fraction parameters were not independently associated with ICU length of stay. No significant correlation was observed between TF parameters and extubation time. ROC analysis showed limited discriminative ability of TF for predicting ICU stay (AUC < 0.70). In exploratory analysis, higher ΔTF (≥76%) was associated with shorter ICU stay; however, this finding was not confirmed after adjustment. Diaphragm thickening fraction was not an independent predictor of ICU length of stay in patients undergoing cardiac surgery. TF may reflect perioperative physiological changes rather than serve as a standalone prognostic marker.