ECM is performed through the same cervical incision used for mediastinoscopy. The innominate artery is palpated on its superior surface, directing the finger towards its origin from the aorta. The innominate artery and the aorta are examined digitally to rule out large atheromatous plaques. It is not recommended to proceed further if digital palpation or CT suggests excessive plaque formation [13]. Once this has been ascertained and following the technique described by Ginsberg et al. [12], the fascia between these two vessels is torn with the finger, and the finger can be advanced easily over the aortic arch (Fig. 3.2a) [19]. Lopez et al. [14] have described a modification of this technique in which the retrosternal space is dissected between the anterior surface of the innominate vein and the posterior surface of the sternum.

After this digital dissection to create a tunnel, over or under the left innominate vein, the mediastinoscope is advanced over the aortic arch between the innominate artery and the left carotid artery and over the hemiazygos accessory vein (Figs. 3.2 and 3.3) [20]. Lymph nodes can be found among fatty tissue (Fig. 3.2b). By moving the mediastinoscope medially, the para-aortic nodes also can be explored, although differentiating between subaortic (station 5) and para-aortic nodes (station 6) is difficult because mobilization of the mediastinoscope is limited by the bony structures of the chest wall. Before biopsying nodes in this location, it is recommended to puncture any structure of dubious nature to avoid bleeding [13, 20].

One limitation of ECM is that it does not allow the surgeon to palpate the subaortic space properly. If palpation is needed to differentiate between mere contact and tumour invasion in this area, then parasternal mediastinotomy is recommended [20].