This study aimed to investigate the association between preoperative diaphragm thickening assessed using ultrasound imaging and PPCs in patients undergoing thoracoscopic esophagectomy for esophageal cancer.
This single-center, prospective, cohort study enrolled patients with esophageal cancer who were scheduled to undergo thoracoscopic esophagectomy between June 2021 and May 2024. Diaphragm thickening fraction (DTF) was measured using ultrasound imaging at preoperatively. Diaphragm thickness (DT) was measured using B‐mode ultrasonography with a linear transducer at the zone of apposition between the eighth or ninth right intercostal space at midway between the anterior axillary and midaxillary line. The DTF was defined as the percentage change in DT during maximal inspiration and maximal expiration. Our primary outcome comprised overall PPCs including atelectasis, sputum expectoration difficulty, pneumonia, or reintubation for respiratory failure. Inverse probability-weighted log regression model within a Bayesian framework were employed to estimate the posterior probability of the odds ratio (OR). Generalized propensity scores for DTF likelihood were estimated from age, smoking status (Brinkman index), comorbidity status (Charlson comorbidity index), advanced cancer stage (clinical stage ≥ II), lung function (forced expiratory volume % in one second), malnutrition (Global Leadership Initiative on Malnutrition criteria), and recurrent laryngeal nerve palsy (RLNP) to generate inverse probability weights.
This study enrolled 73 patients. Eighty-one percent of the subjects were male, with a mean age of 67 years (standard deviation [SD]: 8 years) and a body mass index of 20.8 kg/m2 (SD: 2.8 kg/m2). PPCs occurred in 21 (29%) patients, 10 (14%) of whom had pneumonia. The preoperative DTF in patients with PPCs was 108.3% (SD: 20.9%) compared to 129.3% (SD: 34.0%) in those without PPCs. The mean odds ratio of preoperative DTF to PPCs was 0.82 per 10% increase (95% High density interval: 0.66, 0.97), after adjusting for potential confounders. In the posterior distribution of the model, the probability that the OR of the DTF per 10% increase would be 1 was 98.7%.
Among patients with esophageal cancer undergoing thoracoscopic esophagectomy, preoperative diaphragmatic function was associated with PPCs, and higher preoperative DTF with lower odds of PPCs.
Ultrasound imaging is highly compatible with diaphragm training, as it can be used for visual feedback of diaphragmatic breathing and to set the optimal load of inspiratory muscle training. The results of this study may be used not only for risk assessment of PPCs, but also as potential information for diaphragm strengthening. A future intervention study is needed.
Postoperative pulmonary complication
Esophageal cancer
