Prognostic Significance of Preoperative Respiratory Sarcopenia for Functional Recovery After Cardiovascular Surgery

Impaired functional recovery after cardiovascular surgery is a common and critical complication. The respiratory system is uniquely vulnerable to the physiologic stress of these procedures, and pre-existing deficits in respiratory muscle strength and mass---termed respiratory sarcopenia---can amplify this vulnerability. In this study we aimed to evaluate the independent prognostic value of preoperative respiratory sarcopenia for impaired functional recovery.

This retrospective study enrolled 231 consecutive patients who underwent elective cardiovascular surgery. Respiratory sarcopenia was defined as low respiratory muscle strength (peak expiratory flow rate < 80%) and low respiratory muscle mass (lowest quartile of diaphragm thickness index [diaphragm thickness / body mass index × 100], measured on computed tomography). The primary outcome was a ≥ 1-point decline in the Short Physical Performance Battery score on postoperative day 14 compared with the preoperative value. Multivariable logistic regression identified independent predictors. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were used to evaluate the incremental predictive value.

Respiratory sarcopenia was present in 40 patients (17.3%). In a multivariable model adjusted for clinical covariates and systemic sarcopenia, respiratory sarcopenia independently predicted impaired functional recovery (odds ratio 3.22, 95% confidence interval 1.36-7.64). Adding respiratory sarcopenia to the baseline model provided significant incremental value by improving risk reclassification (NRI 0.36, IDI 0.037).

Preoperative respiratory sarcopenia, characterized by reduced diaphragm thickness and strength, is a robust independent predictor of impaired functional recovery, providing prognostic information superior to systemic sarcopenia and frailty. This specific phenotype identifies respiratory muscle integrity as a key modifiable target for prehabilitation.