Air Leaks as a Source of Distortion in Apexcardiography

Snudi air leaks have been observed to be frequently present in a popular crystal transducer and to cause significant distortion of the apexcardiogram. Such leaks introduce a short time constant thereby differentiating the wave form and producing: (1) peaked and amplified A waves; (2) early fall off of the systolic wave; (3) increase in slope and relative duration of the rapid filling wave. Leaking was found to develop at the seal between the transducer housing and a gasket and was easily eliminated with the application of silicone lubricant. A test “square wave” was produced by quickly clamping the tube connection from bell to transducer, and a short time constant thereby observed as a clue to the presence of leaking. The possibility of such leaks and of certain other physical limitations discussed in this paper support the need for a new device which can simultaneously reproduce the phonocardiogram and apexcardiogram.