Transfer function for vital infrasound pressures between the carotid artery and the tympanic membrane

Abstract

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.

Natural resonance frequency of the brain depends on only intracranial pressure: clinical research

“…Our motivation for this research is to predict the ICP value by analysing the extra-auditory canal pressure waveform (EACPW). It is considered that the EACPW includes the component of ICP value because of their anatomical connection 5,6,[12][13][14][15][16] . We theorised that the ICP value could be predicted with the use of the transfer function method from the cervical cardiac pulse waveform (CCPW) to EACPW 12 .…”

“…It is considered that the EACPW includes the component of ICP value because of their anatomical connection 5,6,[12][13][14][15][16] . We theorised that the ICP value could be predicted with the use of the transfer function method from the cervical cardiac pulse waveform (CCPW) to EACPW 12 . To predict the ICP value from EACPW, for which there is no information of the direct current components included, we focused on the natural resonance frequency (NRF) of the brain.…”