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Biomedical subjects

B Magnuson

Publications and source records attributed to B Magnuson.

At least 19 recordsLinked to original sources
PubMed1997

Hearing results in otosclerosis surgery after partial stapedectomy, total stapedectomy and stapedotomy.

Hearing results in a consecutive series of 407 patients with otosclerosis undergoing primary stapes surgery were analysed (437 operated ears). Partial stapedectomy was performed in 70 ears (16%), total stapedectomy in 205 ears (47%), in both groups using the House steel wire prosthesis on fascia in the oval window. The remaining 162 ears (37%) underwent stapedotomy using the Fisch 0.4 mm teflon-platinum piston. No case of cochlear loss (> 15 dB) occurred in the total series. The comparison between the three groups one year postoperatively showed that the air-bone gap was smaller for partial and total stapedectomy for all frequencies except 4 kHz. The air-bone gap was calculated as the difference between the preoperative bone conduction and the postoperative air conduction thresholds. Partial and total stapedectomy also showed larger improvements of bone conduction thresholds compared with stapedotomy for all frequencies but 4 kHz. At the 3-year follow-up, the hearing gain for all frequencies (250-8000 Hz) was larger for partial and total stapedectomy. Yet, when comparing the decline of hearing from 1 to 3 year postoperatively, the hearing gain achieved with partial and total stapedectomy seemed to deteriorate at a higher rate, which was considered to be caused by impaired sensorineural function. Our results show that in the short-term perspective partial or total stapedectomy can still compete for better hearing results even at higher frequencies, but stapedotomy seems to yield more stable hearing results over time and should therefore be considered as the method of choice.

Adolescent↗
PubMed1995

Structural changes in the rat tympanic membrane following repeated pressure loads.

Healthy adult laboratory rats were exposed to alternating negative pressure and atmospheric pressure to replicate the clinical situation found in patients with chronic sniffing habits and chronic middle ear disease. The rats were placed in a box in which the pressure changed at intervals of 30 s between atmospheric pressure and a negative pressure of -3 kPa. This was repeated continuously for periods of 3 and 7 days. At completion of the experimental period, all rats had a normal otomicroscopic status. However, histological studies demonstrated that the pars flaccida was wrinkled and the loose connective tissue contained large fibroblasts with their long axes lying in a disorganized manner. The cells of the keratinizing epithelium were thicker than normal and mitoses were seen. Epithelial crypts filled with keratin were numerous along the epithelium. In the pars tensa, all layers were thicker than normal. These findings demonstrate that repeated pressure loading can create structural changes in the tympanic membrane.

Animals↗
PubMed1994

Pentobarbital coma in neurosurgical patients: nutrition considerations.

Neurosurgical patients in pentobarbital coma are a complex nutrition support population. Physiologic changes associated with the primary injury to the brain, combined with the pharmacodynamic influences of barbiturate therapy, contribute to the difficulties of initiating aggressive nutrition support. Early nutritional repletion is important to the overall outcome of traumatically injured patients. Consequently, factors that influence nutrition support decisions must be understood to assure appropriate intervention. The metabolic changes associated with traumatic head injury, pentobarbital therapy, and nutrition support strategies are reviewed.

Coma↗
PubMed1990

Different tympanometric procedures compared with direct pressure measurements in healthy ears.

Different tympanometric procedures were compared regarding their reliability and systematic differences in middle ear pressure estimation in healthy adults. In a second part of the study the accuracy of measurement was judged by correlating tympanometric readings, obtained by using the different procedures, with known pressure levels applied after cannulating the mastoid air cell system. There were no significant differences in reliability between the different tympanometric procedures tested (p greater than 0.05). However, forward-backward tracing tympanometry and 'zero sweep rate' tympanometry gave smaller errors in the middle ear pressure estimates than the conventional decreasing pressure sweeps. Forward-backward tracing tympanometry at high sweep rate is recommended both for pressure measurements during physiological studies and in clinical practice.

Acoustic Impedance Tests↗
PubMed1988

Regulation of negative middle ear pressure without tubal opening.

We studied the capacity of the middle ear to regulate a negative pressure despite a closed eustachian tube. The test was performed in a pressure chamber designed for subatmospheric pressures, which enabled us to apply a negative middle ear pressure. In recumbent subjects, the hydrostatic effects of the body position and the negative pressure locked the tube. The subsequent pressure change was monitored by serial tympanometry. Despite a closed eustachian tube, a substantial capacity of reducing negative pressure was present. This capacity is not explained only by hydrostatic effects. The classical "hydrops ex vacuo" theory, which postulates a continuous gas absorption under the present conditions, is not consistent with our findings. Instead, they are in agreement with the view that the turnover of middle ear gas by diffusion is a bidirectional process that may even show a positive balance.

Acoustic Impedance Tests↗
PubMed1987

Middle-ear pressure under basal conditions.

Spontaneous pressure changes in the middle ear were measured under basal conditions in ten subjects with healthy ears. A special "zero sweep rate" tympanometric procedure was developed in order to improve the accuracy of measurement. The respiratory carbon dioxide tension was recorded, and swallowings were indicated automatically. Results showed that the pressure in the majority of ears remained slightly above the atmospheric pressure. In some ears, the pressure increased during periods of drowsiness or sleep when the end-expiratory carbon dioxide tension was rising and the number of swallowings declined. In two ears, the middle-ear pressure showed a slow continuous increase during a two-hour observation period. The present results indicate that the gas turnover in the middle ear by diffusion shows a positive balance during basal conditions. Our findings thus speak against the common belief that the middle-ear gas is continuously being absorbed.

Acoustic Impedance Tests↗
PubMed1985

Morning pressure in the middle ear.

Tympanograms were taken in the early morning in 25 persons with healthy ears. A first tympanogram was obtained shortly after waking up while the subject was still recumbent, and a second tympanogram was taken in the upright position after chewing and swallowing. Positive middle-ear pressure was found in a majority of ears, and the pressure was reduced after swallowing. The present results indicate that gas absorption from the middle ear is not important in quantitative terms during sleep. Otherwise the morning pressure would be expected to be negative. Two other experiments showed that the middle-ear pressure increased during shallow "sleep-type" breathing, and decreased during hyperventilation. The present results can be explained by diffusion of carbon dioxide over the middle-ear mucosa, the direction of gas transfer being dependent on the breathing pattern.

Absorption↗
PubMed1984

Eustachian tube closing failure. Occurrence in patients with cleft palate and middle ear disease.

Previous studies in patients with middle ear disease have shown that high negative pressure is frequently induced actively in the middle ear cavity by sniffing. The present study concerns 84 ears in 42 patients with cleft palate and middle ear disease. Sniff-induced evacuation of the middle ear was studied by direct pressure recording or tympanometry. Sixty-one percent of diseased ears showed tubal closing failure; 18% had constantly or intermittently wide-open tubes. In most cases, negative intratympanic pressure was not equalized on swallowing. It is suggested that eustachian tube malfunction in patients with cleft palate is constituted by the combination of closing failure with evacuation of the middle ear on sniffing, and by a secondary opening failure with inability to equalize the sniff-induced negative intratympanic pressure.

Acoustic Impedance Tests↗
PubMed1984

Test-retest variability of eustachian tube responses in children with persistent middle ear effusion.

In our previous studies on eustachian tube function in children with middle ear effusion, we found that many ears were evacuated by the act of sniffing. When subjects were tested repeatedly, however, responses to sniffing were very variable. In order to study the spontaneous variability, a total of 51 subjects (81 ears) were retested. The results of the retest were very similar to those of the first test when all the ears were considered as a group. However, in individual ears pronounced variability was seen. In the sniff test, responses changed qualitatively in 30% of the ears, and in 27% of the ears there was a change in the ability to equalize pressure by swallowing. Thus, the results of the group were highly reproducible, while at the same time individual results were highly variable with time.

Adolescent↗
PubMed1984

Eustachian tube closing failure in children with persistent middle ear effusion.

One important role of the Eustachian tube is to protect the middle ear from the extensive physiological pressure variations that take place in the nasopharynx, for example on sniffing. In a previous investigation in 50 children with persistent middle ear effusion a surprisingly high percentage of ears were evacuated by sniffing. The present study was undertaken in a second series of children, and results were found to be reproducible. In total 156 ears in 100 children have been investigated. In 63% of ears (73% of subjects) evacuation of the middle ear took place on sniffing. Results show that Eustachian tube malfunction in these subjects is characterized by a reduced protective function; a condition denoted "Eustachian tube closing failure".

Adolescent↗
PubMed1984

Evacuation of the middle ear by sniffing: a cause of high negative pressure and development of middle ear disease.

Previous research on eustachian tube function has been devoted mainly to the study of the tubal opening ability and pressure equalization. This article summarizes a series of experimental studies focusing on the closing ability of the tube. Results support the belief that the purpose of the tube should be seen primarily as protecting the middle ear from the extensive pressure variations that physiologically take place in the nasopharynx. A number of studies of diseased ears have shown that tubal malfunction was characterized mainly by a reduced ability to withstand negative pressure in the nasopharynx. Sniffing can evacuate the middle ear, causing high negative intratympanic pressure. It seems likely that this mechanism is involved in the development of middle ear effusion and manifest retraction-type middle ear disease.

Child↗
PubMed1984

Diagnosis and management of eustachian tube malfunction.

The eustachian tube is an essential part of the pressure regulating system of the middle ear. The physiologic function of the tube is to equalize the middle ear pressure with that of the atmosphere, and at the same time make the middle ear independent of the nasopharyngeal environment with its loud sounds, extensive respiratory pressure changes, and potentially harmful bacterial flora. Thus, the protective closing action is essential in the normal physiology of the eustachian tube, and lack of protection is central in tubal malfunction. We have come to consider eustachian tube closing failure and the subsequent induction of negative middle ear pressure as an important causative factor in the development of chronic ear disease, for example, persistent middle ear effusion and manifest retraction of the tympanic membrane. Here, the patient's behavior may be of more importance than the simple tubal mechanics. In the presence of tubal closing failure, if the patient sniffs habitually, the middle ear cavity will be evacuated repeatedly. This constitutes a repetitive barotrauma which may have secondary effects. As a result of the negative pressure the tympanic membrane retracts, and increased transudation and secretion of fluid may give rise to effusion. Tubal closing failure also implies reduced protection against ascending infection with increased susceptibility to acute otitis media. Repeated sniff-induced barotrauma and repeated purulent infection may together be responsible for the development of manifest structural lesions seen in chronic ear disease. Is it possible to determine the function of the eustachian tube? This question is crucial since it is difficult or impossible to give normative values for tubal function tests. The variability of tubal responses with time has been found to be considerable. Thus, the result of a test represents only one specific moment in time, having little prognostic value. Tubal function is a continuous and composite variable that cannot be "determined" according to a static scheme. Our knowledge of eustachian tube physiology is still fragmentary, and continued study is necessary in order to learn more. Presently, tubal function tests have little value from the clinical viewpoint. When a tympanoplastic procedure is considered, the need for surgery should be determined by the clinical judgment based on the otomicroscopic findings and the hearing. In the case of a central perforation of the eardrum the prognosis for hearing is good, irrespective of results obtained in tubal function tests.(ABSTRACT TRUNCATED AT 400 WORDS)

Child↗
PubMed1983

Eustachian tube malfunction and middle ear disease in new perspective.

Our traditional concepts relating to the development of middle ear disease are based on the assumption that obstruction of the Eustachian tube with reduced ventilation of the middle ear space leads to the development of high negative pressure in the middle ear and, ultimately, to the development of middle ear disease. This hypothesis, which focuses on Eustachian tube opening failure, has not been verified satisfactorily. Results of recent studies indicate that another approach to the problem can lead to a better understanding of the Eustachian tube pathophysiology leading to the development of ear disease. Direct measurements of middle ear pressure in patients with manifest ear disease have revealed that high negative intratympanic pressure is generated by the voluntary act of sniffing. This type of Eustachian tube malfunction is thus characterized by Eustachian tube closing failure. The repetitive barotrauma induced by sniffing or reverse Valsalva maneuvers seems to be a basic predisposing factor in the development of recurrent middle ear effusion and chronic middle ear disease, including adhesive otitis and cholesteatoma.

Cholesteatoma↗
PubMed1981

The atelectatic ear.

Direct measurements of middle ear pressure were performed in 14 children with recurrent middle ear effusion and deep retraction of the tympanic membrane. In 12 of the 22 ears studied, measurements showed that a high negative pressure in the middle ear space had been induced by sniffing. Results suggest that a combination of closing failure of the Eustachian tube and sniffing is the cause of effusion and progressive retraction of the tympanic membrane in these patients. It is further suggested that cholesteatoma, which was present in three of the patients, was also a result of sniff-induced negative pressure in the middle ear space.

Adolescent↗
PubMed1981

On the origin of the high negative pressure in the middle ear space.

It has generally been assumed that a high negative pressure in the middle ear space results from obstruction of the eustachian tube and the subsequent gas resorption through the middle ear mucosa. There is clinical evidence that quite a different mechanism is operating. The present experimental study verifies, with direct pressure recordings in cases of the retraction type of cholesteatoma and related conditions, that a high negative pressure can be generated by an active evacuation of air through the eustachian tube. The high negative pressure induced may explain the development of tympanic membrane retraction and pocketing, and the subsequent development of cholesteatoma.

Adult↗
PubMed1981

Tubal opening and closing ability in unilateral middle ear disease.

Eustachian tube function tests were performed simultaneously in both ears of 29 patients with strictly unilateral middle ear disease. In 15 of the patients eustachian tube closing failure was evidenced by sniff-induced negative pressure in one or both middle ears. The results of the pressure equalization test showed that there was no conclusive difference between the abilities of healthy and diseased ears to equalize pressure. The forced opening test indicated that the diseased ears had less resistant tubes, but there was a wide overlap of results. Since no distinct difference was seen, the clinical value of tubal function tests used presently seems to be severely restricted.

Adolescent↗