Mechanics of the Eustachian tube as it influences susceptibility to and persistence of middle ear effusions in children.
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Child↗
Biomedical subjects
C D Bluestone
Publications and source records attributed to C D Bluestone.
Tympanometric pattern classification in relation to middle ear effusions.
Tympanometric evaluation using an otoadmittance meter and X-Y plotter was performed on 129 ears of 70 children with history of recurrent acute otitis media, or evidence otoscopically of persistent middle ear effusion, or both. Myringotomy, performed immediately following the tympanometric procedure, confirmed the presence or absence of effusion. Following myringotomy, tympanometric patterns, as shown by susceptance and conductance tracings at 220 and 660 Hz, were identified and middle ear pressures and otoadmittance peak values were determined. These findings were compared and criteria were developed which best determined the presence or absence of effusion. The results revealed the following: 1) High negative middle ear pressure is not necessarily a reliable indicator of middle ear effusion. 2) Tympanometry can be used reliably as an indicator of effusion. A combination of pattern classification and susceptance criteria enabled correct prediction of effusion in 93% of these children. One pattern at B660 was found to be pathognomonic of effusion. 3) In general, otoadmittance at 660 Hz appears to be a better indicator of effusion than 220 Hz.
Acute Disease↗
Eustachian tube ventilatory function in relation to cleft palate.
The ventilatory function of the Eustachian tube was assessed in a group of infants and children with cleft palate, some of whom had received palatal repair. Those whose palates had been repaired were better able, in general, to equilibrate applied positive middle ear pressures than were those with open clefts. In many of the patients whose palates had been repaired, the results of Eustachian tube function studies were similar to those in normal subjects. Differences in Eustachian tube ventilatory function are assumed to be related to differences in tubal compliance. Excessive compliance probably results in, or exaggerates, functional Eustachian tube obstruction. Improvement in tubal function following palate repair is probably related to factors resulting in greater tubal stiffness.
Adolescent↗
Obstructive adenoids in relation to otitis media.
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Adenoidectomy↗
Eustachian tube ventilatory function in children.
In order to establish a simple stimulus-response characteristic of Eustachian tube physiology in children, the tubal ventilatory function was studied. The parameters of active and passive opening of the tube were measured for three groups of patients with nonintact tympanic membranes. The group with traumatic perforations of the tympanic membrane without any history of middle ear disease had better active equilibration function than the group with chronic otitis media and perforations of the tympanic membrane and the group with tympanostomy tubes in the tympanic membrane. Quantitatively, this could be expressed in terms of residual positive pressures. In the study of repeated inflation of the middle ear, all groups had lower second opening pressures which are attributed to the effect of surface forces.
Adolescent↗
Concepts on the pathogenesis of middle ear effusions.
Several concepts related to the pathogenesis of middle ear effusions are postulated. The mechanisms proposed are based on an understanding of fluid mechanics. A flask with a long, narrow neck is presented as a model of the Eustachian tube-middle ear-mastoid system. Fluid flow into and out of the flask is dependent upon the pressure gradient, compliance of the narrow neck and whether or not the bulbous portion is intact. It is suggested that locking of the tube may be dependent upon the speed of the application of the negative pressure and the compliance. Eustachian tube opening appears to be related not only to active muscle forces but may also be dependent upon the presence of a pressure gradient which passively assists tubal function. It is proposed that middle ear effusions result from reflux, aspiration or insufflation of nasopharyngeal secretions (acute otitis media), or from persistent functional or mechanical Eustachian tube obstruction (secretory otitis media) or both.
Ear, Middle↗
Membrane ventilating tube for the middle ear.
A pilot study was conducted to evaluate the efficacy of a membrane ventilating tube as a Eustachian tube prosthesis in 20 patients with otitis media. The design was based partly on assumptions since many of the physiological parameters required to calculate the gas transport processes have not been previously reported. An elementary gas transport model with assumed partial pressures of gases was developed. A semipermeable membrane covering a tympanostomy tube was fashioned and used to ventilate the middle ear cavity. From this preliminary investigation, the device successfully maintained atmospheric pressures in the tympanum, compensated for Eustachian tube malfunction, prevented otorrhea and recurrence of middle ear effusions.
Adolescent↗
Adenoidectomy in relation to otitis media.
Past studies of the efficacy of adenoidectomy in the management of children with otitis media have been inconclusive due to significant limitations in experimental design. At the Children's Hospital of Pittsburgh, the effect of adenoidectomy on the outcome of otitis media is currently being studied in a prospective manner. An attempt is being made to document and to control those factors cited as lacking in the previous studies. This report describes the techniques for assessment of nasal and Eustachian tube function and for the completeness of adenoidectomy.
Adenoidectomy↗
Nasal decongestant activity of pseudoephedrine.
The effectiveness of orally administered pseudoephedrine in patients with acute or chronic nonsuppurative rhinitis was evaluated under double-blind conditions. Intranasally administered ephedrine which was given to all patients at the end of this study served as the positive control. Marked nasal decongestant effects of a single oral dose of pseudoephedrine (60 mg tablet), as determined by a modified passive anterior, rhinometric technique occurred within 30 minutes and were maintained for at least four hours. The mean nasal decongestant response (delta % of baseline) of 57.2% was associated with a mean peak, plasma pseudoephedrine level of 274 ng/ml. In addition, the maximum response to oral pseudoephedrine treatment was equivalent to the response produced by ephedrine nasal spray. These results suggest that pseudoephedrine is an orally, effective nasal decongestant.
Acute Disease↗
Congenital cricopharyngeal achalasia.
Fifteen infants with congenital cricopharyngeal achalasia are reviewed. Although most of the patients had symptoms at birth, the diagnosis was frequently not confirmed until later in the first year of life. While four of the infants had only cricopharyngeal achalasia, 11 had associated diseases related to the central nervous system. Those patients without associated diseases improved spontaneously with conservative management; most of the infants with other abnormalities also improved, although their clinical progress was slower and more complicated. In three of the patients, the symptoms were persistent and there were two deaths related to associated diseases. Cricopharyngeal myotomy was performed on two children with only moderate improvement in symptoms. Congenital cricopharyngeal achalasia is more common than formerly recognized. When suspected, an esophagram with tele- or cineradiography is essential to confirm the diagnosis. Esophageal motility studies will quantify changes and also evaluate lower esophageal dysfunction not easily identified on esophagrams.
Deglutition Disorders↗
Normal and abnormal middle ear ventilation.
Studies in infants and children have suggested a functional rather than mechanical obstruction of the Eustachian tube as a predisposing factor in middle ear effusions (MEE). To simulate this condition in the laboratory, an animal model was prepared using juvenile Rhesus monkeys. The tensor veli palatini muscle was transected or expunged posterior to the hamulus of the medial pterygoid lamina. Transection of the muscle resulted in negative middle ear pressure without effusion, whereas when the muscle was expunged, the animals developed a brief episode of negative middle ear pressure followed by a persistent MEE that was sterile for bacteria. An acute bacterial MEE developed following instillation of Streptococcus pneumoniae into the nasopharynx of animals that had had a previous unilateral transection of the muscle. The condition of the middle ear was documented by impedance measurements and presence of the effusion was verified by myringotomy. Animals were periodically examined and tested for Eustachian tube ventilatory function over a period of one year. Before surgical alteration of the tensor muscle. Eustachian tube function tests demonstrated normal ventilatory function, whereas, functional Eustachian tube obstruction patterns similar to studies in children who had MEE were found during the postoperative period. Only after the development of a reliable animal model can current and future methods of management of MEE be tested under controlled laboratory conditions. These data suggest that the Rhesus monkey appears to be an excellent model for the study of normal as well as abnormal tubal function.
Animals↗
Tympanometric patterns found in middle ear effusions.
In 120 ears of 67 children with a history of recurrent acute otitis media or otoscopic evidence of persistent middle ear effusion, or both, tympanograms were obtained using an otoadmittance meter and an electro-acoustic impedance bridge. Myringotomy was performed immediately following the tympanometric evaluation confirming the presence or absence of middle ear effusion. The comparison of myringotomy findings with a tympanometric pattern classification revealed 85.8% overall correct association with the presence or absence of a middle ear effusion for both instruments. In 83.3% of the cases, there was agreement in the classification of the tympanogram between the otoadmittance meter and the electro-acoustic bridge.
Adolescent↗
Sudden or fluctuating hearing loss and vertigo in children due to perilymph fistula.
Five cases are presented of children with rapid onset of sensorineural hearing loss, disequilibrium, or both, who were found at exploratory tympanotomy to have a perilymph fistula. Four of the children had histories suggesting that antecedent barotrauma or physical exertion contributed to the development of the fistula. One child with congenital unilateral craniosynostosis had a residual temporal bone abnormality on the same side as the perilymph fistula. Two children had identifiable anatomic abnormalities in the middle ear. A classification of perilymph fistula is proposed that describes a congenital, an acquired, and a combined type of fistula. Inner ear fluid dynamics and patency of the cochlear aqueduct appear to be important factors in pathogenesis. Children with unexplained fluctuating or sudden onset of sensorineural hearing loss, and children with unexplained disequilibrium or vertigo should be suspected of having a perilymph fistula. The history can be singularly important in raising the suspicion that a perilymph fistula may be present. Although audiometric, vestibular, and radiographic studies can be helpful, there is no way to prove the presence or absence of a fistula without directly viewing the middle ear. Tympanotomy with repair of the fistula does not assure improvement in hearing.
Adolescent↗
Dilation of the eustachian tube by electrical stimulation of the mandibular nerve.
The recent studies of the anatomy of the eustachian tube and related structures in the Rhesus monkey (Macaca mulatta) have shown that the monkey tubal system is similar to the human. This investigation in Rhesus monkeys was an attempt to verify previous studies in other animals that the tensor veli palatini muscle was the only dilator of the eustachian tube. Two unipolar stimulating electrodes were introduced into the foramen ovale, and the mandibular branch of the trigeminal nerve was electrically stimulated. Simultaneously, pressure-flow recordings through the eustachian tube were monitored. Stimulus-response relationships were obtained for five Rhesus monkeys. The degree of tubal dilation by the tensor veli palatini muscle contraction was shown to be a function of stimulating current levels. Artifically induced dilations were quite similar to the physiological dilations during swallowing when these animals were tested alert. Following complete transection of the tensor muscle, regardless of the stimulus level, no tubal dilations were observed. Stimulation of the nerve to the internal pterygoid and stimulation of the levator veli palatini muscle induced only constrictions of the tube. The tensor veli palatini muscle is the only paratubal muscle responsible for active dilation of the eustachian tube in the Rhesus monkey, and its motor innervation is the mandibular division of the trigeminal nerve.
Animals↗
Airflow through the eustachian tube.
In an attempt to distinguish normal from abnormal eustachian tube function, two groups of adults with nonintact tympanic membranes were tested. Six subjects had traumatic perforations of the tympanic membrane and a negative otologic histroy while five subjects had perforations as a sequela of otitis media. The subjects were tested with two methods: the middle ear inflation-deflation technique and a newly introduced forced-response technique. The comparison of the two groups revealed marked differences between normal subjects and patients with middle ear disease in active tubal dilation mechanisms and biomechanics of the eustachian tube. The forced-response test appeared to be a better method to determine the degree of actual tubal function.
Adult↗
Design factors in the characterization and identification of otitis media and certain related conditions.
Because the state of our knowledge of many aspects of the etiology and pathogenesis of otitis media and related conditions is deficient, precise characterizations of certain aspects of the disease may not be possible. In fact although most studies in the past have failed to define the specific disease state to be investigated, the specific type of otitis media or related condition to be studied must be as clearly defined as is clinically possible in order for any prospective study of otitis media to be valid. The state of the art of the presently available methods to identify these conditions also poses certain limitations; at present, there are five methods to identify otitis media and related conditions: history, audiometry, tympanocentesis/myringotomy, otoscopy (including otomicroscopy), and impedance measurements (tympanometry and assessment of the middle earl muscle reflex), and they all have inherent elements of unreliability. Historical information obtained from parents or the child is usually unreliable; a positive history may aid in defining the problem, but a negative otologic history does not rule out the presence of otitis media since it is frequently asymptomatic. Audiometry has been shown to be a poor method of identifying otitis media. Although tympanocentesis or myringotomy is the most reliable way to identify otitis media with effusion (OME), it is invasive, frequently requires an anesthetic, and is usually a confounding variable. In an effort to establish the diagnostic value of otoscopy, tympanometry, and the presence or absence of the middle ear muscle reflex in identifying OME, the diagnostic findings by these three methods, were compared with the findings at myringotomy in 239 children (425 ears). The study showed that even experienced clinicians had some difficulty in identifying those ears with effusion (sensitivity) and had even greater difficulty in making a diagnosis of those ears without an effusion (specificity). Tympanometry employing patterns that have been validated with myringotomy findings was found to be as accurate as expert otoscopy. On the other hand, the presence or absence of the middle ear muscle reflex was found not to be a useful method of diagnosing the presence of OME due to its extremely low specificity. An algorithm derived from the combination of the three methods had highest sensitivity and specificity. From this study, the following recommendations regarding the identification of OME are suggested. All investigators who employ otoscopy should be validated by comparing their assessments either with the findings at myringotomy or with a previously validated otoscopist. Interobserver realiability of all otoscopists should be established prior to and maintained during clinical studies of OME. Only electroacoustic impedance instruments in which the tympanometric patterns have been validated should be used. Tympanometry employing validated tympanometric patterns has a high degree of sensitivity and specificity, and as such can provide an objective method to identify OME...
Acoustic Impedance Tests↗
Pulmonary edema following relief of acute upper airway obstruction.
Five children, aged one to five years, with severe upper airway obstruction, three of whom had epiglottitis and two of whom had laryngotracheobronchitis, developed acute pulmonary edema after the obstruction had been relieved by placement of an artificial airway. Although major physiologic changes, such as hypoxemia and massive sympathetic discharge, play a significant role in the development of acute pulmonary edema, we have postulated a possible etiological cause for the development of pulmonary edema in these children which involves a series of physiologic events. The generation of very high transpulmonary pressure gradients during inspiration is opposed by a decreased venous return due to the obstruction during exhalation. Airway pressures then fall abruptly with the insertion of the artifial airway, resulting in a sudden increase in venous return to the central circulation and marked increase in the intravascular hydrostatic pressures. The final result of this series of events is the development of pulmonary hyperemia and edema. The prevention of this situation must begin the moment the airway is inserted and involves the application of moderate amounts of continuous positive pressure to the airway, thus allowing time for circulatory adaption to take place.
Airway Obstruction↗
Eustachian tube function in an American Indian population.
A comparatively high prevalence of acute and chronic otitis media (OM) has been reported for the native American Indian population. The present study reports data on the function of the eustachian tube (ET) in 25 White Mountain Apache Indians ranging in age from 3 to 36 years. All study subjects had a history of OM and reported to the reservation clinic with tympanic membrane perforations and a dry middle ear (ME). The results of inflation-deflation tests on these subjects indicated that the Indians had lower forced opening pressures than had been measured in a group of Caucasians with perforations secondary to chronic OM. Of the 23 subjects studied, 67% equilibrated applied positive ME pressures and 38% equilibrate negative pressures by swallowing. During forced response testing, the passive resistance of the ET was found to be lower and the active resistance equivalent to that of a group of Caucasians with traumatic perforations and otherwise negative otologic histories. While the ET was predilated in these subjects by constant airflow, active swallowing further dilated the tube in 67% of the subjects, constricted the tube in 25%, and had no effect in 8%. This study indicated that the ET of the American Indian was functionally different from that of Caucasians previously studied and was characterized by comparatively abnormal, low passive tubal resistance which may be considered to facilitate ventilatory function and to impair protective function. The difference may account for the high prevalence of OM with perforation and the low incidence of cholesteatoma in this population.
Adolescent↗