72 yo m with sob for 3 days. hx of htn and cad. receiving 2 l/min of o2 via nasal cannula. temp 37 c, p 110/min, resp 20/min, bp 150/80. bilateral crackles and wheezes. hct is 28%, leukocyte count is 8000. pulmonary artery cath shows cardiac index of 2 l/min (n = 2.5 – 4.2) and a pulmonary artery occlusion pressure of 28. abg shows ph 7.49; pco2 30; po2 58. most appropriate next step in management