A nasal breathing apparatus with multifunction has two nasal inserts and one tubular chamber. In one embodiment, the first nasal insert forms an airtight barrier inside one nostril for delivering gases. The second nasal insert does not block the other nostril and is for sampling gases. The tubular chamber is in fluid communication with the first nasal insert but not the second nasal insert and has an outlet for discharging and delivering gases and for providing continuous positive airway pressure and ventilation. In another embodiment, both nasal inserts form an airtight barrier in the corresponding nostrils. The first nasal insert is dedicated for delivering gases and the second nasal insert for sampling gases. The tubular chamber is in fluid communication with both nasal inserts and has an outlet for discharging and delivering gases and for providing continuous positive airway pressure and ventilation.