Apparatus (40) for monitoring oro-nasal respiratory flow is disclosed. The apparatus (40) is formed of a curved plate (42) to which is substantially perpendicularly arranged a planar member (44), the plate (42) and the member (44) are connected by a neck portion (46). Mounted in an upstanding fashion from the planar member (44) are two nasal prongs (48, 50). Two PVDF sensors (60) are mounted from, and lie in, the plane of the planar member (44), co-operating with a respective nasal prong (48, 50). A further PVDF sensor (80) in planar form is arranged to be downwardly directed and perpendicular to the planar member (44) so as to be located in the vicinity of the mouth when the apparatus (40) is being worn by a patient. The PVDF sensors (60, 80) deflect respectively under the influence of nasal and oral airflow, and generate electrical charge having a determined relationship with the airflow.