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(Chest. 1970;57:163-169.)
© 1970 American College of Chest Physicians

Air Leaks as a Source of Distortion in Apexcardiography

John A. Kastor M.D.1; Saul Aronow Ph.D.2; Robert E. Nagle M.B., M.R.C.P.3; Thomas Garber S.M. (E.E.)4; and Harriet Walker 5

1 Instructor in Medicine, Harvard Medical School; Assistant in Medicine, Massachusetts General Hospital, Boston, Massachusetts
2 Research Associate in Medicine, Harvard Medical School. Associate Applied Physicist, Massachusetts General Hospital, Boston
3 Queen Elizabeth Hospital, Birmingham, England
4 Senior engineer, Waltham Division, Hewlett-Packard Company, Waltham, Massachusetts
5 Phonocardiographic Technician, Massachusetts General Hospital, Boston

Small 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.






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