Abstract: An arrangement and method for detecting spontaneous respiratory effort of a patient receiving ventilatory support via a breathing circuit. A patient/breathing circuit interface is adapted to provide a closed connection between a breathing passage of the patient and the breathing circuit. A sensor is disposed at least partially in the breathing passage of the patient and arranged to sense flow of gas through the breathing passage. The arrangement and method individually or in addition to the airway pressure measurement promotes reliable and rapid detection of breathing efforts of a non-intubated patient to promote efficient augmentation of patient breathing.