Transfer function for vital infrasound pressures between the carotid artery and the tympanic membrane.
While occupational injury is associated with numerous individual and work-related risk factors, including long working hours and short sleep duration, the complex mechanisms causing such injuries are not yet fully understood. The relationship between the infrasound pressures of the tympanic membrane [ear canal pressure (ECP)], detected using an earplug embedded with a low-frequency microphone, and the carotid artery [carotid artery pressure (CAP)], detected using a stethoscope fitted with the same microphone, can be quantitatively characterized using systems analysis. The transfer functions of 40 normal workers (19 to 57 years old) were characterized, involving the analysis of 446 data points. The ECP waveform exhibits a pulsatile character with a slow respiratory component, which is superimposed on a biphasic recording that is synchronous with the cardiac cycle. The respiratory ECP waveform correlates with the instantaneous heart rate. The results also revealed that various fatigue-related risk factors may affect the mean magnitudes of the measured pressures and the delay transfer functions between CAP and ECP in the study population; these factors include systolic blood pressure, salivary amylase activity, age, sleep duration, postural changes, chronic fatigue, and pulse rate.
Department of Electrical and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8533 Japan. kennfur@shinshu-u.ac.jp
Kenji
K
Furihata
Masato
M
Yamashita
D000328:Adult; D062186:Arterial Pressure; D001274:Atmospheric Pressure; D002339:Carotid Arteries / Q000502:physiology*; D016002:Discriminant Analysis; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009784:Occupational Diseases / Q000209:etiology / Q000503:physiopathology; D011187:Posture; D012044:Regression Analysis; D056152:Respiratory Rate; D012307:Risk Factors; D019023:Stethoscopes; D013997:Time Factors; D014160:Transducers, Pressure; D014432:Tympanic Membrane / Q000502:physiology*; D055815:Young Adult