Apnea monitoring by acoustic detection of airflow.

An acoustic monitor to detect apnea in infants has been developed. Recordings of a signal derived from breath sounds at the nose were made in eight premature infants and compared with observation of the infant and with transthoracic impedance and ECG monitoring. The acoustic monitor detected 26 episodes of apnea lasting 15 seconds or longer which were confirmed by observation and by heart rate slowing of at least 20 beats per minute. Only seven of these episodes were detected by the impedance monitor. The ECG monitor alarmed during the nine spells in which heart rate dropped below 100 beats per minute, 27.5 +/- 9.7 seconds after breath sounds ceased. Inasmuch as the acoustic device detects absent airflow during central or obstructive apnea before bradycardia occurs and is insensitive to body movements, it represents an improved monitoring technique for infants with apnea.