Shigeji Fukuta

Spectral analysis of airflow sounds in patent versus occluded tracheostomy tubes: a pilot study in tracheostomized adult patients.

Cannula occlusion is a life‐threatening postoperative complication of tracheostomy. Current management largely relies on nursing care for prevention of fatalities because no proven mechanical, machine‐based support monitoring exists. The objective of this paper was to address the problem of monitoring the state of cannula patency, based on analysis of airflow acoustic spectral patterns in tracheostomized adult patients in the patent and partially occluded cannula. Tracheal airflow sounds were picked up via a condenser microphone air‐coupled to the skin just below the tracheal stoma. Signal output from Mic was amplified, high‐pass filtered, digital tape‐recorded, and analyzed on a mainframe computer. Although airflow frequencies for patent cannulae were predominantly low‐pitched (0.1 to 0.3 kHz), occluded tubes had discrete high‐pitched spectral peaks (1.3 to 1.6 kHz). These results suggest that frequency analysis of airflow sounds can identify a change in the status of cannula patency.

Effects of persistent perilymph fistula on the inner ear.

To study the effects of a persistent perilymph fistula on the cochlea, a small cannula was inserted into the scala tympani of the basal turn of cochlea in guinea pigs. A month later, cochlear morphology and blood flow were studied using either histological evaluation or the microsphere surface preparation technique. Some animals showed no cochlear morphologic changes or no cochlear blood‐flow reduction, even if tubal patency was maintained and perilymph leakage lasted for 1 month. This suggests that a prolonged perilymph fistula, per se, causes no permanent cochlear damage. However, in some animals, hair cell damage and cochlear blood‐flow disorders were observed. These observations and the causes of hearing loss in clinical cases of perilymph fistula were studied.

Inner Ear Disorders Caused by Barotrauma in Guinea Pigs

To determine the mechanism of hair cell damage caused by barotrauma to the inner ear, we investigated morphological changes in the organ of Corti and stria vascularis using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Fractures of the stereocilia with minimal intracellular changes were observed immediately after trauma. One day later, there was marked degeneration of outer hair cells and expansion of supporting cells. The damage to stereocilia clearly preceded morphological alterations within the hair cell bodies. Most outer hair cells eventually disappeared and were replaced by supporting cells. Inner hair cells degenerated slowly: some were almost intact 1 month after the trauma despite the disappearance of stereocilia. The continuity of reticular lamina was maintained throughout the period of hair cell degeneration, preventing leakage of endolymph into the organ of Corti. Reversible dendritic swelling of inner hair cells occurred immediately after trauma. No change in the stria vascularis was observed over time. Our results suggest that the mechanism of hair cell damage caused by inner ear barotrauma is related to a deformity of the organ of Corti caused by a pressure discrepancy between the perilymph and endolymph, resulting in injury to stereocilia.

A case of pleomorphic adenoma of the epiglottis Bilateral vocal-cord paralysis after YAG laser surgery

Pleomorphic adenoma of the larynx is a rare disorder, and until recently has been treated mainly by approaches involving pharyngotomy. We encountered a case of pleomorphic adenoma originating from the laryngeal surface of the epiglottis and removed it using a YAG laser through a suspension laryngoscope. This case was complicated by delayed-onset bilateral vocal-cord paralysis, the causes of which are also discussed.