A respiratory monitoring apparatus (10) includes a central venous pressure sensor (24) configured to measure a central venous pressure (CVP) signal of a patient. At least one processor (32, 34, 36, 38, 40, 42, 44, 58) is programmed to process the CVP signal to generate respiratory information for the patient by operations including: segmenting the CVP signal based on detected breath intervals； calculating a surrogate muscle pressure signal from the segmented CVP signal； and filtering the surrogate muscle pressure signal to remove a cardiac activity component a cardiac activity component of the surrogate respiratory muscle pressure signal.
