ELECTROSTETHOGRAPHY. 1. CATHODE RAY VISUALIZATION OF LUNG CHEST SOUNDS

Abstract

An electro-stethograph was described utilizing a crystal microphone with mechanical contact, an electron amplifier and cathode ray tube recorder with a wide and uniform frequency response. By application of various improvements in design the apparatus except for cameras can be enclosed in a small case weighing less than 15 lbs. Utilizing phonation and a sweep circuit the method permits visual study of the transmission of chest sounds to the chest wall, and also permits single photographic exposures. In the normal the characteristic wave forms observed in the upper chest comprise a fundamental frequency and an harmonic. The waveforms become progressively simplified being sine waves at the lower border of the lungs. The lung borders can be accurately outlined. Behind the heart on the left the wave forms show differences as compared with the symmetric area on the right. Changes in wave form observed are described in a few pulmonary diseases. These consist of marked changes in amplitude and in harmonic content including square wave formation. The phonation method described offers definite refinements in the study of chest sounds. Simplicity of operation and compactness make the method a practical one for the study of pulmonary disease.