Dear Editor, Endotracheal intubation especially for one-lung ventilation (OLV) is an important procedure during thoracic surgery.1 Thus, accurate selection of the appropriate double-lumen tube (DLT) size is critical to achieving effective ventilation and minimizing surgical complications. However, the available methods for determining DLT size mainly rely on height and sex, and are primarily based on Western populations,1 limiting their applicability to Asian populations, especially Asian females.