Respiratory sarcopenia defined by paraspinal muscle mass and peak expiratory flow predicts postoperative pneumonia after esophagectomy for esophageal cancer: a comparison with sternocleidomastoid muscle mass.

BACKGROUND: Sarcopenia is a predictor of postoperative pneumonia after esophagectomy. Recently, respiratory sarcopenia has been proposed as a predictor of postoperative pneumonia that captures respiratory vulnerability more directly than sarcopenia. Respiratory sarcopenia is defined by decreased respiratory muscle strength (RMS) and respiratory muscle mass (RPM). As RPM does not have an established assessment method, previous studies used skeletal muscle mass at L3, including the psoas major (PM) and paraspinal (PS) muscles. However, this may not accurately reflect respiratory muscle status. Therefore, we focused on the sternocleidomastoid (SCM) muscle, an accessory respiratory muscle. We investigated which muscle mass measure for defining respiratory sarcopenia shows the strongest association with postoperative pneumonia after esophagectomy: SCM at C3, PM at L3, or PS at L3. METHODS: We reviewed 500 patients who underwent radical subtotal esophagectomy from 2007 to 2024. Based on preoperative CT, muscle mass was calculated as the areas of the three muscles normalized by height squared. RMS was assessed by percent predicted peak expiratory flow (%PEF). Respiratory sarcopenia was defined as low %PEF and low muscle mass. Univariable and multivariable logistic regression evaluated factors associated with postoperative pneumonia. RESULTS: Eighty patients (16.0%) developed postoperative pneumonia. In multivariable analysis, respiratory sarcopenia defined by PS mass was associated with postoperative pneumonia after adjustment for covariates (OR: 2.76, 95% CI 1.32-5.79, P = 0.007). SCM- and PM-based definitions were not significantly associated with postoperative pneumonia. CONCLUSION: Respiratory sarcopenia defined by decreased %PEF and PS mass is associated with postoperative pneumonia after esophagectomy.