A 65-year-old woman with a 30-year history of recurrent cough, sputum production, and wheezing was admitted due to worsening symptoms for 1 week. Examination: conscious, cyanotic, jugular vein distension, scattered medium and fine crackles and rhonchi in both lungs, heart rate 120 bpm with regular rhythm. Liver 3 cm below the costal margin, pitting edema in both lower limbs. Peripheral WBC count 12×10<sup>9</sup>/L (neutrophils 80%). CXR shows right inferior pulmonary artery trunk 17 cm and prominent lung markings. The most critical treatment for this patient is: