Background: Patients with decreased pulmonary function and lung tumors are often candidates for thermal ablation. Ablation of lesions adjacent to the course of the phrenic nerve carries special risk in this population, since diaphragm paralysis or dysfunction can have significant clinical impact on patients with baseline respiratory compromise.

Methods: Retrospective case review with imaging review of phrenic nerve anatomy.

Results: A 68 year old man with COPD and FEV1 63% predicted underwent radiofrequency ablation of a right paramediastinal non-small cell lung carcinoma. The lesion, which appeared well separated from the expected region of the phrenic nerve on diagnostic imaging, was significantly closer to the expected course of the nerve with mechanical ventilation and lower lung volumes during the procedure. His postprocedure course was complicated by elevation of the right hemidiaphragm and increased oxygen requirement, findings consistent with injury to the phrenic nerve.

Conclusions: The relationship of paramediastinal lung lesions to the expected course of the phrenic nerve can be altered by lung volume differences between inspiratory diagnostic scans and procedural scans obtained with mechanical ventilation. Knowledge of phrenic nerve anatomy and available separation techniques is important for procedural planning and could lead to improved patient outcomes.