A cannula receives respiratory airflows (RA) from a subject (12) and interface airflows (IA) from an area (38) near the cannula. The respiratory airflows (RA) and interface airflows (IA) are directed to a differential pressure transducer (P) to determine pressure differentials between the respiratory airflows (RA) and interface airflows (IA), which effectuate a change in a breathing circuit of the subject (12) in response to the pressure differentials. Preferably, the pressure differentials are directed to a ventilator (22), which is configured to respond to the pressure differentials. In additional embodiments, the cannula also receives first respiratory airflows (1 ST RA) and second respiratory airflows (2 ND RA) from the subject (12), as well as exhaled gases therefrom. Corresponding respiratory monitoring methods also receive the same.
