MRCP2-0097

The orthopaedic surgeons are seeking a medical opinion on an 80-year-old man who is 10 days post-total hip replacement surgery. The patient had a smooth operation and has been doing well in the postoperative period. However, he suddenly experienced left-sided chest pain and shortness of breath. Upon examination, his pulse was 120/minute and respiratory rate was 22/minute. His chest was clear upon auscultation and heart sounds were normal. An ECG revealed left bundle branch block (LBBB). Arterial blood gases on air showed a pH of 7.44 (7.36-7.44), pO2 of 9.5 kPa (11.3-12.6), and pCO2 of 3.4 kPa (4.7-6.0). What is the most probable diagnosis?