A BIOACOUSTIC METHOD FOR TIMING OF RESPIRATION AT CARDIAC INVESTIGATIONS

At cardiac investigations Doppler echocardiography is an established t echnique for the recording of intracardial and intravascular now veloc ities. Transvalvular and venous flows are, however, markedly influence d by respiration. Since the start of inspiration is the important time of reference, accurate recording of the respiratory phase is importan t when analysing these flow velocities. A bioacoustic technique was th erefore adopted to meet this demand and was tested in 10 normal subjec ts. Oesophageal balloon technique was used as a reference, and the bio acoustic technique was compared with a respiratory inductive plethysmo graph. The average delay for the acoustic sensor signal compared to th e oesophageal pressure changes was 205+/-46 (SD) ms, ranging from 160 to 320 ms for normal breathing, and is comparable to that of the respi ratory inductive plethysmograph (210+/-90 ms). The bioacoustic techniq ue is easier to apply than the respiratory inductive plethysmograph. T he sensitivity to disturbances can be further reduced by signal proces sing and the method has clinical potential for the future.