Search PubMed⌕ Search

Biomedical subjects

J S Sillman

Publications and source records attributed to J S Sillman.

11 recordsLinked to original sources
PubMed1995

Signal averaging and waveform analysis of laser Doppler flowmetry monitoring of porcine myocutaneous flaps: I. Acute assessment of flap viability.

Postoperative monitoring of microvascular free-tissue transfer is essential to the early identification and correction of vascular compromise. Laser Doppler flowmetry is a noninvasive monitor of capillary bed perfusion. Its current clinical use requires continuous monitoring and trend analysis to detect changes in capillary perfusion. This study investigated the hypothesis that signal averaging of laser Doppler flowmetry output triggered by a fixed point in the cardiac cycle would provide accurate information about the microvascular flow patterns not dependent on trend analysis. These results indicate that averaged waveform analysis allowed for a rapid, objective, and statistically significant distinction between a viable myocutaneous flap and one with vascular compromise in a porcine model. Moreover, this technique allows for distinction between venous and arterial insufficiency.

Animals↗
PubMed1994

Laser Doppler measurements of intratemporal facial nerve blood flow.

Whereas the anatomy of the vasculature supplying the intratemporal facial nerve is well known, little is known of the dynamics of blood flow within the nerve. The present study was performed to ascertain whether laser Doppler flowmetry (LDF) could detect changes in blood flow within the tympanic segment of the rabbit facial nerve. Compression of the facial nerve immediately distal to the geniculate ganglion resulted in an 80-95 percent reduction in blood flow in the tympanic segment of the nerve, whereas distal neurovascular compression had no effect. Blood flow in the tympanic segment of the nerve fell 40-60 percent during ipsilateral common carotid artery occlusion, but no change occurred with contralateral carotid occlusion. Signal-averaging techniques detected a sinusoidal amplitude modulation of the LDF flow signal that was synchronous with the cardiac cycle. The peak-to-peak amplitude of this modulation was reduced by proximal nerve compression, and the reduction in amplitude was in proportion to the overall reduction in the LDF flow signal. The authors conclude that the direction of blood flow in the tympanic segment of the rabbit facial nerve is primarily proximal to distal. Acute changes in blood flow within the tympanic segment of the nerve could readily be detected using LDF. This technique offers the possibility of monitoring human facial nerve blood flow, and may help elucidate the pathophysiology of various facial neuropathies.

Animals↗
PubMed1992

The effect of pentoxifylline on cochlear blood flow.

Pentoxifylline, a phosphodiesterase inhibitor and hemorrheologic agent has been found to increase oxygen delivery to ischemic tissue. Intravenous pentoxifylline was administered to normal guinea pigs in order to assess the effect of pentoxifylline on cochlear blood flow and to elucidate its mechanism of action. Intravenous pentoxifylline was found to acutely increase cochlear blood flow in a dose-dependent manner. In normal animals, the effect appeared strongly related to the rheologic properties of this agent rather than a vasodilative action. Normovolemic hemodilution with 75% dextran resulted in no increase in cochlear blood flow during infusion of pentoxifylline, whereas the application of nitroprusside over the round window failed to abolish the effect of pentoxifylline.

Animals↗
PubMed1992

Prognostic value of evoked and standard electromyography in acute facial paralysis.

Ninety-one patients with idiopathic (n = 62) and traumatic (n = 29) facial paralyses were available for evaluation at least 1 year after the onset of paralysis. In nine cases of idiopathic paralysis and in 12 cases of traumatic paralysis, total intratemporal nerve decompression was performed. The remaining patients were treated with steroids alone. All patients underwent evoked electromyography (EEMG) testing within 2 weeks of the onset of paralysis. Facial nerve recovery was graded using the House-Brackmann facial nerve recovery scale. Subjects were grouped according to maximal decline of compound muscle action potential (CAP), as determined by EEMG, and by level of recovery 1 year after onset of paralysis. Among patients who did not undergo surgical decompression of the facial nerve, incomplete clinical recovery (grade III or higher) was significantly associated with CAP decline of greater than 90% (p less than 0.05) for idiopathic paralysis. In contrast, there was no significant association between CAP decline of greater than 90% and clinical outcome in traumatic paralysis. These findings support previous reports of the prognostic value of EEMG in idiopathic facial paralysis, but suggest that this test may have less predictive value in the evaluation of facial paralysis as a result of trauma.

Action Potentials↗
PubMed1989

Electrically stimulated increases in cochlear blood flow: I. Frequency and intensity effects.

Charge-balanced, sinusoidal current was passed differentially between the apex and round window of the guinea pig cochlea. Cochlear blood flow was measured using a laser Doppler flow monitor. Systemic blood pressure was monitored from a cannula within the common carotid artery. Electrical stimulation increased cochlear blood flow, while systemic blood pressure was unaffected. A cochlear blood flow response parameter, normalized for transient changes in systemic blood pressure, was defined. The magnitude of the response parameter was found to be frequency selective and was also found to be an increasing function of current intensity, with maximum responses obtained with 500 Hz sinusoids. This cochlear blood flow response was not observed in dead animals; was present in preparations paralyzed with gallamine hydrochloride; and was correlated with an increase in cochlear red blood cell velocity, as directly observed by intravital microscopy. These observations imply that electrical stimulation induces a local vasodilation within the temporal bone. The fact that decreased cochlear blood flow was never observed with current injection implies that ischemia is not a likely mechanism of electrically induced tissue damage within the inner ear. The mechanism of this cochlear blood flow response is addressed in a companion report.

Animals↗
PubMed1989

Electrically stimulated increases in cochlear blood flow: II. Evidence of neural mediation.

In a companion paper, we reported that electrical stimulation increased cochlear blood flow (CBF). This response was found to be an increasing function of current intensity and was frequency-selective, with the best response at approximately 500 Hz continuous sinusoidal current. The present investigation seeks to discover the mechanism of this effect. Direct measurement of cochlear temperature during electrical stimulation revealed no evidence of local heating. Autonomic neuronal activation is not likely, as neither atropine, hexamethonium, nor propranolol abolished the evoked CBF response. Strial activity could be suppressed by the use of furosemide, but the evoked CBF response persisted. Inactivation of auditory afferent neurons with kainic acid also did not change the evoked CBF response. Dimethyl sulfoxide, a potent oxygen-free radical scavenger, did suppress the evoked CBF response to a small but significant degree. This suggests that oxygen-free radicals may be produced within the cochlea during electrical stimulation. Finally, the evoked CBF response was completely suppressed by procaine and tetrodotoxin, with recovery of evoked CBF response accompanying recovery of cochlear action potentials. These data indicate that stimulation of neural fibers, distinct from autonomic and auditory afferent neurons, may modulate CBF.

Animals↗
PubMed1989

A comparison of laser Doppler and intravital microscopic measures of cochlear blood flow.

Many inner ear disorders may be caused by alterations in cochlear blood flow (CBF). However, each measurement technique used to monitor CBF has limitations in examining the relationship between otopathologic states and blood flow. This study investigates laser Doppler flowmetry (LDF) and its fundamental drawback: the unknown relationship of LDF output to actual CBF. LDF readings are directly compared with concurrent intravital microscopy (IVM) measures of erythrocyte velocity in the lateral wall of the guinea pig cochlea. Positive end expiratory pressure, spontaneous respiration of 5% and 10% carbon dioxide, phenylephrine, and direct electrical stimulation of the cochlea were used to manipulate CBF. High, positive correlations were found between simultaneous LDF and IVM measurements of CBF. In addition, the study demonstrated that current microdissection techniques used to perform IVM do not cause changes in CBF. IVM measurements of CBF are a more sensitive indicator of CBF changes than are LDF measures. Despite the high correlation between measurement techniques within a single manipulation, simultaneous LDF and IVM measurements differed between manipulations. This may reflect regional changes in CBF affected by these manipulations and differences in the sampled vascular beds contributing to these two measures. It is unlikely that a single calibration factor can be defined that would allow the conversion of LDF output to actual units of blood flow across different manipulations used to alter CBF.

Animals↗
PubMed1988

Pattern of blood vessels in forelimbs of three strains of mice.

A technique was developed for visualizing the pattern of arteries in the adult mouse forelimb. The aorta was cannulated and injected with blue stained Batson's Number 17 Anatomic Compound to perfuse the forelimb arteries; the ossified skeleton was stained and the soft tissues were cleared, making it possible to examine the entire arterial system in the intact specimen. The pattern of distribution of arteries were compared in 120 forelimbs from three strains of mice, two inbred and one hybrid. Significant differences between the three strains were found for 9 of 16 variations evaluated. Differences in the point of origin of vessels were the most common; differences in the fusion of vessels, the extension of vessels and the presence of extra vessels were also identified. The patterns were much more constant in the two inbred strains than in the hybrid strain, suggesting the importance of genetic factors in determining the arterial pattern. Absence of major vessels and an abnormal persistence of embryonic vessels, which have been observed in association with skeletal malformations, were not observed in any of the 120 normal adult mouse forelimbs examined.

Animals↗
PubMed1985

Metabolic facial paralysis in an infant.

A 2-month-old infant developed facial paralysis with a presentation that masqueraded as a possible middle ear tumor. The cause of the paralysis eventually was related to a metabolic consequence of his underlying disorder, cystic fibrosis. To our knowledge, the association of vitamin A imbalance, pseudotumor cerebri, and facial paralysis has not previously been discussed in the otolaryngologic literature.

Cystic Fibrosis↗
PubMedDate not supplied

Recent advances in cochlear blood flow measurements.

Changes in blood flow to the inner ear have been thought to influence or underlie a number of cochlear diseases, including some forms of noise-induced hearing loss, sudden hearing loss, and Meniere's disease. Recently, important advances have been made in two technologies for the study of cochlear blood flow. The first is in the area of vital microscopic studies of cochlear microcirculation, and the second is based on the introduction of laser technology in the form of laser Doppler flowmetry. In this report, measurements are given of changes in cochlear circulation caused by carbon dioxide breathing, intravenous phenylephrine injection, systemic hemodilution, positive end expiratory pressure, and direct electrical stimulation of the cochlea. From these changes, we observe that cochlear blood circulation responds to systemic blood pressure alterations and is subject to local flow control mechanisms. Linearity and speed of response of the laser Doppler instrumentation also are shown. These advances show promise for contributing to our knowledge of control mechanisms of inner ear blood flow and for revealing the influence of various pharmacologic agents of potential clinical value.

Animals↗