Respiratory function monitor especially for very young children - employs differential amplifier for compensation of extraneous interference with breathing sounds filtered and recorded graphically.

摘要

The monitor is based on an acoustic waveguide (6) with apertures (9) in the vicinity of the patient's nostrils (8). A stopper (15) divides the waveguide into two portions (13,14) terminated at separate microphones (2,3). One portion (13) conveys the sounds of breathing, while the other (14) having oppositely directed apertures collects extraneous noise. The two microphones are wired to a differential amplifier feeding a chart recorder via low-pass and high-pass filters in succession. Only signals in the frequency band between about 1 and 3 kHz are recorded.