Anaesthetic management can be challenging when patients have multiple co-morbidities. This report presents one such case: a pug with brachycephalic airway syndrome, in late gestation, presented with a lung lobe torsion. Under general anaesthesia the dog had initially low PaO2, with severe ventilation perfusion mismatch and pulmonary shunt, this was mildly improved with patient positioning with head-up tilted table in right lateral recumbency. Tension pneumothorax developed after initiation of positive pressure ventilation, and was resolved with rapid entry into thoracic cavity. Ventilation was adjusted with the aid of spirometry, blood gases, capnography and direct visualisation of lung tissue. The dog made a full recovery and was discharged from hospital 5 days post-operatively.