A system (20) includes circuitry (26, 42) and one or more processors (28, 36), configured to cooperatively carry out a process that includes receiving, from the circuitry, a speech signal (62) that represents speech uttered by a subject (22), the speech including one or more speech segments, dividing the speech signal into multiple frames (64), such that one or more sequences (66) of the frames represent the speech segments, respectively, computing respective estimated total volumes of air exhaled by the subject while the speech segments were uttered, by, for each of the sequences, computing respective estimated flow rates of air exhaled by the subject during the frames belonging to the sequence and based on the estimated flow rates computing a respective one of the estimated total volumes of air, and in response to the estimated total volumes of air, generating an alert. Other embodiments are also described.
