Pediatric tracheostomy: a changing procedure?

In 1982, the experience with tracheostomy at The Children's Hospital of Philadelphia was reported for 1971 through 1980. We have now reviewed 450 cases for the period from 1981 through 1992, and compared the characteristics of these cases with those in the previous review. Long-term follow-up was available on 83% of cases, and the median follow-up was 2.96 years. Patients received a tracheostomy for airway obstruction (38%), chronic ventilation (53%), or multiple indications (9%). The mean duration of tracheotomy (adjusted for death and loss to follow-up) was 2.13 years. The tracheostomy-related mortality was 0.5%, and the nontracheostomy-related mortality was 22%. Nineteen percent of patients had complications in the first postoperative week, and 58% had 1 or more late complications. In comparison with the previous study from our institution, there was a great increase in long-term tracheostomy and a continuing trend away from tracheostomy for short-term airway management. Better monitoring and improvements in parental teaching may have contributed to a decrease in tracheostomy-related mortality.

Congenital airway abnormalities in patients requiring hospitalization

OBJECTIVE

To determine the cause of congenital airway abnormalities in pediatric patients requiring hospitalization for their respiratory status.

DESIGN AND SETTING

Case series in a tertiary care center.

PATIENTS

A 5-year retrospective chart review was conducted at our institution. A total of 174 patients were identified who required hospitalization for their respiratory status as a result of a congenital airway abnormality.

RESULTS

Of the 174 patients, 114 (65.5%) were male and 60 (34.5%) were female. Eighty patients (47%) presented within the first 3 months of life. Forty-six patients (26%) were born prematurely, and 49 patients (28%) were diagnosed as having gastroesophageal reflux. The majority of patients (139 [80%]) had multiple presenting symptoms or signs. Stridor was the most common (129 [74%]), followed by accessory respiratory effort, cyanosis, apnea, and failure to thrive. Diagnosis was made at the time of surgical evaluation in 91% of the patients, with the remaining diagnoses made using radiological findings and/or clinical evaluation. Sixty-five patients (37%) had multiple sites of airway abnormalities; laryngeal abnormalities were noted almost 3 times as often as tracheal abnormalities (161 vs 62, respectively). Of the laryngeal abnormalities, laryngomalacia was the most common, followed by glottic web, subglottic stenosis, vocal-cord paralysis, and subglottic hemangioma. Tracheomalacia was the most common tracheal abnormality, followed by external compression and tracheal stenosis. Thirty-three patients (19%) required tracheotomy for management of recurrent respiratory decompensation.

CONCLUSIONS

While congenital airway abnormalities are usually self-limited, those patients requiring hospitalization represent a group with a more severe respiratory status who have a greater chance of requiring tracheotomy. The recognizable percentage of patients with gastroesophageal reflux and prematurity accounts for comorbid factors in the need for hospitalization for respiratory issues related to congenital airway abnormalities.

Conditional Length of Stay

OBJECTIVE

To develop and test a new outcome measure, Conditional Length of Stay (CLOS), to assess hospital performance when deaths are rare and complication data are not available.

DATA SOURCES

The 1991 and 1992 MedisGroups National Comparative Data Base.

STUDY DESIGN

We use engineering reliability theory traditionally applied to estimate mechanical failure rates to construct a CLOS measure. Specifically, we use the Hollander-Proschan statistic to test if LOS distributions display an "extended" pattern of decreasing hazards after a transition point, suggesting that "the longer a patient has stayed in the hospital, the longer a patient will likely stay in the hospital" versus an alternative possibility that "the longer a patient has stayed in the hospital, the faster a patient will likely be discharged from the hospital."

DATA COLLECTION/EXTRACTION METHODS

Abstracted records from 7,777 pediatric pneumonia cases and 3,413 pediatric appendectomy cases were available for analysis.

PRINCIPAL FINDINGS

For both conditions, the Hollander-Proschan statistic strongly displays an "extended" pattern of LOS by day 3 (p<.0001) associated with declining rates of discharge. This extended pattern coincides with increasing patient complication rates. Worse admission severity and chronic disease contribute to lower rates of discharge after day 3.

CONCLUSIONS

Patient stays tend to become prolonged after complications. By studying CLOS, one can determine when the rate of hospital discharge begins to diminish--without the need to directly observe complications. Policymakers looking for an objective outcome measure may find that CLOS aids in the analysis of a hospital's management of complicated patients without requiring complication data, thereby facilitating analyses concerning the management of patients whose care has become complicated.

Development of the paranasal sinuses in children with sinus disease

In a previous report, the authors defined the normal development of the paranasal sinuses. Landmarks and dimensions relevant to functional endoscopic sinus surgery were measured on the computed-tomography images of 145 children who were free of significant sinusitis. The present study compares those normal values to the same measurements in 235 cases of sinus disease. No significant difference was found between normal and diseased groups in any of the 10 dimensions originally reported or in six derived measures. There appears to be no association between sinus disease and any of these dimensions. The previously reported norms are applicable to cases of pediatric sinus disease.

Congenital airway abnormalities requiring tracheotomy: a profile of 56 patients and their diagnoses over a 9 year period

We reviewed the 9 year experience at the Children's Hospital of Philadelphia with patients requiring tracheotomy for a diagnosis of congenital airway abnormalities. Of the 56 patients, 28 (50%) had cardiovascular, or chromosomal abnormalities, neurologic conditions, or congenital syndromes, 24 (43%) were born prematurely, and 13 (23%) were found to have gastroesophageal reflux. Only 18 (32%) went on to eventual decannulation of their tracheotomy with a mean tracheotomy duration of 1.75 years. The majority of patients (75%) had multiple presenting signs. Stridor was the most common (54%), followed by accessory respiratory effort (39%), cyanosis (30%), apnea (29%), and failure to thrive (23%). Twenty eight patients (50%) had multiple airway abnormalities contributing to their need of a tracheotomy for airway protection orr ventilator dependence. Laryngeal abnormalities were found in 71% of patients, tracheal abnormalities in 48% of patients, bronchial abnormalities in 11%, and upper airway obstruction in 14%. Of the laryngeal abnormalities, laryngomalacia was the most common, followed by subglottic stenosis, glottic web, and vocal cord paralysis. Tracheomalacia was the most common tracheal abnormality. The relatively large percentage of patients with cardiovascular or other major malformations, and prematurity, accounts for comorbid factors in the need for prolonged tracheotomy (and low early decannulation rate). Although gastroesophageal reflux was found in a recognizable portion off the patients, it is unclear whether this represents a comorbid condition.

Dexamethasone in adenotonsillectomy

Edema contributes substantially to the postoperative discomfort and morbidity of adenotonsillectomy. In a double-blind study, 58 children undergoing adenotonsillectomy were given a single intraoperative dose of either dexamethasone or saline. The steroid markedly affected the postoperative course in the first day after surgery. According to parental reports, the percentage of patients vomiting was reduced from 48 to 4%. Severe throat pain was reported in 57% of controls and only 20% of dexamethasone patients. Twice as many steroid patients as controls tolerated some soft food on the first postoperative day. It appears that dexamethasone can greatly improve patient diet and comfort after adenotonsillectomy.

Tympanoplasty for the anterior-superior perforation in children

Anterior-superior perforations of the tympanic membrane have proven more difficult to repair than other perforations, and many investigators have found such repairs to be problematic. We report a technique in which the tympanic membrane is released from the malleus, and the graft is placed medical to the remnant, lateral to the malleus, and medial to the tympanomeatal flap. In a series of 42 cases the short-term surgical success rate (represented by an intact graft at 6 months) was 98%, with 95% of ears remaining free of reperforation to the end of follow-up. Postoperatively, 90% of children had an air-bone gap of 20 dB or less and 100% of children had an air-bone gap of 30 dB or less. Eighty-seven percent of subjects demonstrated a speech reception threshold (SRT) of 20 dB or better, whereas 100% of subjects demonstrated an SRT of 30 dB or better. These results compare favorably with those reported at this institution for repair of perforations of any quadrant in children, and those of other investigators for anterior superior perforations in adults.

Infant salt taste: developmental, methodological, and contextual factors

Two studies investigated the human infant's response to salt during development. In the first study, measures of intake and sucking were obtained from two groups of infants, newborns and 4- to 8-month-olds, in response to brief presentations of two concentrations of salt (0.2 or 0.4 M) and water. For several measures of sucking and for intake, there were significant age and concentration effects. Generally, newborn infants tended to reject saline relative to water more than did 4- to 8-month-old infants. This result, consistent with previously published research, suggests a developmental change in salt acceptability and, probably, sensitivity in the human infant. In the second longitudinal study, the response to salted (0.15 M) versus unsalted formulas was evaluated monthly in infants 2 to 7 months of age. Again, a developmental change was observed: Based on some sucking measures, younger infants appeared to be indifferent to the salted formula relative to the unsalted formula whereas older infants tended to reject the salted formula, presumably because either it was less sweet than the unsalted formulas or because it was novel. These data are consistent with the hypothesis developed from animal model studies that during early human postnatal development, transductive elements sensitive to saltiness mature.

Effect of anesthetic gas on middle ear fluid

Tympanometry was performed before (preoperative) and after (intraoperative) the administration of inhalation anesthesia including nitrous oxide and halothane on 109 children undergoing myringotomy with pressure equalization tube insertion. A total of 213 preoperative tympanograms were compared with their intraoperative counterparts and the presence or absence of middle ear effusion at myringotomy. When preoperative tympanograms were consistent with pneumatized middle ears, intraoperative findings demonstrated a mean middle ear pressure increase of +147 daPa. When preoperative tympanometry suggested middle ear effusion, less than 1% demonstrated intraoperative tympanometric changes and/or findings at surgery that would support anesthesia clearing middle ear effusion. Preoperative tympanometric data were poor predictors of the presence or absence of effusion at myringotomy. The relationship between inhalation anesthetics (i.e., nitrous oxide and halothane) and middle ear fluids, and the reliability of tympanometry to predict middle ear effusion are discussed.

Type 1 tympanoplasty in children

OBJECTIVE

To identify factors affecting the surgical success rate and reperforation rate in type 1 tympanoplasty. Controversy continues regarding the advisability of this procedure in young children, largely because of the likelihood of recurrent middle ear disease and eustachian tube dysfunction.

DESIGN

Retrospective medical record review of a case series.

SETTING

Pediatric hospital that serves both as a primary care and referral center.

PATIENTS

All private patients younger than 18 years, undergoing type 1 tympanoplasty from 1985 through 1989, for whom at least 6 months' follow-up was available. Two hundred nine tympanoplasties on 183 patients were included; 22 patients were excluded for insufficient follow-up.

MAIN OUTCOME MEASURES

Surgical success was defined by confirmation of an intact tympanic membrane at least 6 months postoperatively. Procedures were deemed long-term successes if the tympanic membrane remained free of perforation to the end of follow-up.

RESULTS

The overall short-term surgical success rate was 92%, with 87% of ears remaining free of reperforation to the end of follow-up. If the perforation involved the margin, the surgical success and long-term success rates dropped to 86% and 77%, respectively. Although reperforation was more likely in patients younger than 6 years or in those with contralateral otitis media at surgery, even these groups had long-term success rates of 81% and 74%, respectively.

CONCLUSIONS

Tympanoplasty may be considered at any age. Even in young children, there is a high likelihood of return to normal function.

Total and partial ossicular replacement prostheses in children

Although ossicular reconstruction in children may carry a risk of failure because of recurrent middle ear disease, the procedure offers the potential for restoring binaural hearing during the school years when it is so critical. Of a series of 45 reconstructions with total and partial ossicular replacement prostheses, 6 were extruded for a surgical success rate of 87%. Of the successful cases, 74% had air-bone gaps of 30 dB or better, and 74% had speech reception thresholds of 30 dB or better on initial postoperative audiogram. Outcomes for these children were comparable with those reported for adults, supporting the value of early reconstruction.

Concurrent right and left ear auditory brain stem response recording

In auditory brain stem response testing, it is often advantageous to record the responses to right and left ear stimulation quickly. A method is described in which both ears are tested concurrently, each ear at a slightly different stimulus rate. With appropriate temporal parameters, the response of each ear can be recorded without contamination by the contralateral ear's response. When both ears were tested at the same intensity, either 40 or 70 dB nHL, there was little attenuation of wave V. When one ear was stimulated at 80 dB nHL, the response of the other ear at intensities down to 40 dB was not seriously affected; the response at 20 dB nHL was, however, so diminished by contralateral stimulation at 80 dB that binaural testing would save no time. This method has promise for intraoperative monitoring and infant screening, and could be used in threshold determination if the stimulus intensities for the two ears are not too dissimilar.

Childhood epiglottitis in recent years

Fifty-five cases of acute epiglottitis were diagnosed and treated at the Children's Hospital of Philadelphia between 1985 and 1991. To evaluate the changing patterns of the disease over recent years, we compared the current results with those obtained from an earlier study reported at our institution in 1979. The overall annual incidence was higher in recent years than in the earlier study, with a sharp decline in new cases over the last two years. Thirty-six percent of the Hemophilus influenzae type B (HIB) infections were ampicillin-resistant in recent years, while no resistance had been found in the past. Twenty-seven percent of the cases were vaccine failures, all before 1990. Endotracheal intubation was the sole method for upper airway maintenance, while in the past 31% of the children underwent a tracheotomy. No mortality or long-term complications were found in either study.

Signal to noise constraints on maximum length sequence auditory brain stem responses

In conventional auditory brain stem response (ABR) testing, the stimulus rate must be low enough that the responses do not overlap. By using stimulus patterns derived from the pseudorandom binary series known as maximum length sequences (MLSs), it is possible to stimulate at mean rates of hundreds of clicks per second, and extract the responses. It has been suggested that this could reduce test time appreciably, but there is reason to believe that the MLS ABR is intrinsically noisier than conventional averaging. To test this premise, 10 ears were tested with conventional ABR procedures and with MLS ABRs having 2, 4, and 8 times as many stimuli per second as the conventional condition. Noise levels in control runs were in agreement with predictions. With a 40 dB nHL stimulus, wave V amplitude decreased in the MLS ABRs to the extent that none of the MLS conditions was as efficient as the conventional ABR. Any assessment of the value of MLS ABRs in reducing test time must take into consideration the higher noise levels inherent in this procedure.

Usefulness of computed tomographic scan in the evaluation of sensorineural hearing loss in children

A retrospective chart study was conducted to determine the diagnostic yield of temporal bone imaging for children with sensorineural hearing loss of unknown cause. Seventy consecutive cases, spanning 4.5 years, were identified and individual computed tomography films reviewed. Cases were analyzed with respect to patients' age, duration of hearing loss, sudden onset vs progressive loss, unilateral vs bilateral, and other symptoms. Of the 70 computed tomographic scans, nine showed temporal bone or other intracranial abnormalities. The majority of these findings were localized to structures in the posterior and middle cranial fossae. No eight nerve tumors were identified. Congenital hearing loss and hearing loss secondary to viral infections are the most common cause of sensorineural hearing loss when discovered in early childhood and, often, have no radiographic abnormality. The decision to explore an ear for a presumed perilymph fistula is based almost exclusively on the history and physical examination, and not on the demonstration of any radiographic findings. For the children presenting with stable hearing impairment in the absence of other findings, computed tomographic scans were either negative or did not contribute to diagnosis. Since tumors of the eighth nerve are rare in children under 16 years of age (without neurofibromatosis), and radiologic studies have a low yield in identifying perilymph fistulas, the routine use of computed tomographic imaging in such children may be unjustified.

Developmental patterns of normal nutritive sucking in infants

The purpose of this investigation was to quantify normal nutritive sucking, using a microcomputer-based instrument which replicated the infant's customary bottle-feeding routine. 86 feeding sessions were recorded from infants ranging between 1.5 and 11.5 months of age. Suck height, suck area and percentage of time spent sucking were unrelated to age. Volume per suck declined with age, as did intersuck interval, which corresponded to a more rapid sucking rate. This meant that volume per minute of sucking time was fairly constant. The apparatus provided an objective description of the patterns of normal nutritive sucking in infants to which abnormal sucking patterns may be compared.

The auditory brain stem response recorded with 60 Hz notch filters

Line-frequency (60 Hz in the USA) interference is a common source of contamination during recording of the auditory brain stem response (ABR). Notch filters are undeniably effective in eliminating this artifact, but concerns have been expressed as to their effect on the ABR itself. Theoretical considerations suggest that the degree of distortion should be minimal if the filter is sufficiently sharp and the stimulus rate has no multiples very close to 60 Hz. Responses simultaneously recorded through three notch filters of varying sharpness confirmed this: Latency was virtually unaffected with any filter or stimulus rate, and distortion was minimal when a sharply tuned filter was used in conjunction with a stimulus rate of 23.3 Hz, whose nearest harmonic to 60 is 69.9 Hz.

Hearing impairment in ventilator-dependent infants and children

Bronchopulmonary dysplasia is a complication of prematurity that can require months or years of ventilatory support. Among a cohort of 12 such ventilator-dependent patients, half had auditory brainstem response thresholds of 40 dB nHL or worse in the better ear. In 10 of 23 ears the threshold was 50 dB or worse. This incidence of hearing impairment is much greater than for other high-risk premature infants. Although conductive impairment was implicated in many cases, the degree of impairment is greater than that ordinarily seen with middle ear effusion.

Recovery of the basilar papilla following intense sound exposure in the chick

Newly hatched chicks were exposed to a 900-Hz tone at 120 dB SPL for 48 hours, then sacrificed, along with unexposed controls, at intervals of 0-15 days following exposure. Examination of the basilar papilla by scanning electron microscopy demonstrated a 32% loss of hair cells within the lesion area with substantial shrinkage of the apical surfaces of the survivors. Within days, the papilla returned to a nearly normal appearance, and new hair cells were seen, but the number of new cells was only a fraction--approximately 22%--of the number lost. Expansion of the apical surfaces of the surviving cells to larger than normal size was a major factor in the recovery of the papilla.

Reliability of sleep sonography in detecting upper airway obstruction in children

In children, lymphoid hyperplasia is by far the most common cause of airway obstruction during sleep, but the determination as to presence or degree of obstruction is seldom made objectively, because of the expense and stress of polysomnography. If audio recordings are made by parents at home with standardized equipment, however, obstruction can be recognized readily. Such recordings obtained from 50 patients were computer processed and the resulting displays were independently rated by two judges. Interobserver correlation was 0.87 and split-half reliability was 0.83, demonstrating very good reliability of the processing and scoring procedures. Recordings made on successive nights were highly consistent as well (test-retest reliabilities of 0.78 and 0.86 for the two raters). This recording method, which is well accepted by parents and children, has both clinical and research value in the assessment of airway obstruction.

Ototoxicity of antimycotics

Neither otomycoses nor defects of the tympanic membrane are rare. In cases of fungal infection when the tympanic membrane is not intact, the possibility exists that antimycotic medication could enter the middle ear and diffuse into the cochlea via the round window. Five antimycotic preparations were tested for acute ototoxic potential in guinea pigs. Those containing acetic acid or propylene glycol caused appreciable elevation of brainstem response thresholds, while little or no impairment resulted from tolnaftate or clotrimazole solutions in polyethylene glycol 400.

A prospective study of titanium ventilation tubes

A prospective controlled study was undertaken in which in 100 children a titanium ventilation tube was inserted in one ear, and a Paparella silicone tube was inserted in the contralateral ear as a control. The tubes were evaluated with respect to length of time of intubation, episodes of otorrhea, and early occlusion. Sixty-five patients were followed for at least one year, or until both tubes had extruded. Long-term follow-up of these patients has revealed little difference in the incidence of tube occlusion, early extrusion, or infection with otorrhea. Since the titanium tube is more than twice as expensive and has no proven advantages over a silicone tube of similar design, we have no reason to recommend its use over the less costly, standard silicon ventilation tube.

Digital filtering of auditory evoked potentials

Digital filters have been proposed by many authors for analysis and enhancement of the auditory brain stem response and related potentials. Because these techniques are unfamiliar to many, and require attention to underlying assumptions, an overview of the field is presented, with emphasis on limitations and risks of each method. Topics include Fourier transforms, finite impulse response (convolutional) filters, and infinite impulse response (recursive) filters.

A controlled study of a 'new' ventilating tube. The gold standard?

A prospective controlled study of a gold ventilation tube was undertaken in which a gold tube was inserted in one ear of 88 children and a Paparella silicone tube was inserted in the contralateral ear as a control. The tubes were evaluated with respect to length of time of intubation, episodes of otorrhea and early occlusion. Sixty-three patients were available for a follow-up of at least 6 months. The gold tube remained in place for a shorter period of time when compared to the control tube. Episodes of otorrhea were infrequent and there was not any significant difference between the two types of tubes. The gold tube became occluded more frequently than the control tube. Since the gold tube is approximately 3 times more expensive and has no proven advantages over our conventional silicone tube, we have no reason to recommend its use in preference to any other available tube.

Auditory brainstem responses and behavioural responses in pre-term infants

Auditory brainstem responses (ABRs) and behavioural thresholds were studied in 25 pre-term infants with post-conceptional ages of approximately 40 weeks to ascertain whether there were differences in the ABR between normal preterm and full-term new born infants to compare behavioural thresholds around 40 weeks of post-conceptional age and to follow changes of their behavioural thresholds in the first year of life. ABR thresholds, peak latencies of Waves I and V and the I-V peak interwave latency were measured. Behavioural audiometric thresholds to pure tones were determined through behavioural observation audiometry and conditioned orientation-reflex audiometry. The ABR thresholds of the pre-term infants, whether they were small for date (SFD) or appropriate for date (AFD), were in the normal ranges of the controls. Moreover, there were no significant differences between either the SFD or the AFD group and controls, as far as Wave I or V latency or I-V interval are concerned. Thus, the ABR was apparently unaffected by the infant being small-for dates. Behavioural audiometry disclosed that all normal full-term infants responded to pure tone stimuli, with mean thresholds of 85 dB, while only 42% of AFD and 30% of SFD would respond to pure tone stimuli at 90 dB or less. Behavioural thresholds caught up with the normal range by 12 months of age, except for a few infants.

Relief of upper airway obstruction by adenotonsillectomy

Adenotonsillectomy is often performed to relieve upper airway obstruction, even in children who do not present with severe apnea. Although adenotonsillectomy provides dramatic relief from obstructive sleep apnea, little evidence is available as to the efficacy of surgery in the far more prevalent cases of partial airway obstruction. We report the results of a prospective study of 100 children with adenotonsillar obstruction (without severe apnea) and 50 age-matched control children. The majority of patients exhibited appreciable sleep disturbances preoperatively, as compared to controls, and had substantial postoperative improvement, as demonstrated by parental questionnaire and sleep sonography--the computer-aided analysis of respiratory sounds. Mouth breathing and behavior problems were also prevalent preoperatively and were affected positively by adenotonsillectomy. It appears that surgery in such cases can have far-ranging benefits, even for the child whose obstruction does not demonstrate severe apnea.

Auditory brainstem responses in young children with Down's syndrome

Auditory brainstem evoked responses (ABRs) were studied in 37 Japanese infants and children with Down's syndrome to determine the level of the lesion causing their unresponsiveness to sound stimuli. ABR thresholds, peak latencies of waves I and the peak interval latency of wave I-V were measured. For comparison with ABR thresholds, behavioral audiometry was performed. Thirty-two percent of the patients (12 cases) with Down's syndrome showed no responses by ABR as well as behavioral audiometry. The other ABR abnormalities with respect to age-matched controls were classified into 6 types: shorter wave I latencies (2 cases, 5%), shorter wave V latencies (7 cases, 19%), shorter wave I-V intervals (8 cases, 22%), wave I prolongation (13 cases, 35%), wave V prolongation (5 cases, 14%) and prolongation of wave I-V peak interval (no case, 0%). Our results demonstrate a high incidence of hearing loss at middle and inner ear levels, and suggest some anomaly within the auditory brainstem in Japanese cases of Down's syndrome.

The lateral neck radiograph in adenotonsillar hyperplasia

In this study we have considered whether the lateral neck radiograph is useful in predicting the degree of airway obstruction, and whether supine and erect views are more useful than a single film. We evaluated the supine and erect lateral neck radiographs of 50 patients with upper airway obstruction due to enlarged tonsils and adenoids. Our results show that the supine radiograph, which is technically easier to perform, is entirely satisfactory for appraising the size of the tonsils and adenoids, but that neither view tells us much about the degree of airway obstruction during sleep.

The auditory pathology of brain death as revealed by auditory evoked potentials

A case of brain death is reported in which the auditory brainstem response, middle latency component, and slow vertex response were recorded before and after the cessation of cortical activity, and in which histological examination of the temporal bone and central auditory pathways was performed post mortem. Brain death of at least 48 hours' duration was demonstrated by neurological examination, flat electroencephalographic recording, and persistent absence of auditory evoked responses. The postmortem examination was performed 3 hours after death. The pathological studies of the whole length of the auditory pathway revealed total autolysis of the organ of Corti, marked cell loss in the dorsal cochlear nucleus, and moderate cell loss in other nuclei of the central auditory pathway. It should be considered that total autolysis of the organ of Corti and severe cell loss of the cochlear nucleus may occur if the auditory brainstem response becomes absent in comatose patients.

Hearing loss and visco-elasticity of middle ear fluid

It has been suggested that the physical properties of middle ear effusion--its viscosity and elasticity--affect the degree of conductive impairment. Exogenous mucus having substantial visco-elasticity was instilled in the bullae of guinea pigs, and the resulting hearing loss was determined by measurements of the cochlear microphonic potential. In this preparation the hearing loss induced by mucus did not differ significantly from that found when the bulla was filled with saline. We find no evidence of a relationship between visco-elasticity of middle ear fluid and amount of conductive impairment.

Auditory and vestibular function in hyperbaric oxygen

The therapeutic value of high partial pressures of oxygen is limited by the toxicity of oxygen. Pulmonary damage, visual impairment, and convulsions are known hazards during hyperoxic exposure, but dose-effect relationships have not been quantified for specific organs or functions. As part of an integrated study of organ oxygen tolerance in man (Predictive Study V of the Institute for Environmental Medicine), auditory and vestibular function was evaluated in man before, during, and after exposure to 100% oxygen at 3 atmospheres absolute pressure for 2 to 3.5 hours. No alterations in hearing or equilibrium were detected, suggesting that ototoxicity is not a factor that would limit exposure under these conditions.

Auditory testing of dogs with inherited retinal degeneration

Auditory function was tested by brainstem-evoked response (BSR) audiometry in dogs affected by hereditary retinal degeneration (HRD). Comparison of BSR thresholds and latency-intensity functions revealed no significant difference between progressive rod-cone degeneration (PRCD) affected and unaffected miniature poodles, and no evidence of sensorineural hearing loss in HRD-affected English cocker spaniels and miniature schnauzers. The authors conclude that hearing loss is not a feature of the retinal degenerations in these dogs.

Drugs affecting clearance of middle ear secretions: a perspective for the management of otitis media with effusion

Otitis media with effusion (OME) is characterized by the production and accumulation in the middle ear of mucus secretions, whose physicochemical properties are an important feature in the etiology and treatment of the disease. Many types of pharmaceutical agents, including anti-inflammatory agents, antihistamines, antibiotics, and mucolytics, have been used in attempts to improve the clinical status of patients with OME. This study critically reviews the literature from the point of view of possible changes induced by these agents in the physicochemical properties of the secretions and hence their clearance from the middle ear. In vitro studies on mucociliary clearance of respiratory (tracheobronchial) secretions and middle ear effusions are cited as the basis for analyzing the important parameters expected to govern middle ear clearance and to determine the rationale for use (or nonuse) of various classes of drugs. It is expected that this analysis will prove useful in the design of properly controlled trials of such agents.

Auditory short, middle, and long latency responses in acutely comatose patients

For assessing comatose patients, the combination of auditory short, middle, and long latency evoked potentials (auditory brain stem response [ABR], middle latency component [MLC], and slow vertex response [SVR] ) is more comprehensive than auditory brain stem response (ABR) only or ABR with slow vertex response (SVR). Fifty-four acutely comatose patients were studied. Thirty-four of the patients had severe head injury and others had coma of varied etiology. Within two months after admission, 25 patients survived, while 29 patients died. Auditory evoked response measurements were conducted usually within 48 to 72 hours after admission. For patients with normal SVR, MLC, and ABR, there was 100% survival; with absent SVR but normal MLC and ABR, survival was 91%; with absent SVR and MLC and normal ABR, it was 60%; with abnormal ABR, it was 10%; no patient survived whose ABR was absent. It is emphasized that a normal MLC is clearly a predictor of survival of comatose patients, but a normal ABR is not always a reliable indicator of survival.

Mucociliary transport of human ear secretions in otitis media with effusion

Rheologically active mucus glycoproteins (mucins) were isolated from the middle ear effusions of 282 patients (344 ears) presenting with secretory otitis media (SOM). The mucins were pooled according to the pathologic condition associated with the SOM. Pools were reconstituted to the same conditions and tested for ciliary transport rates with the use of the frog palate transport model. Mucin obtained from cleft palate patients showed significant differences in transport behavior in comparison with mucins from other groups of patients with SOM.

Resistance of the auditory brain stem response to high barbiturate levels

In the comatose patient the auditory brain stem response may be one of the few indices of CNS function available. Because barbiturates may be administered to control intracranial pressure and its sequelae, demonstration of the effect of barbiturates on the brain stem response is desirable. In cats preloaded with 63 mg/kg of pentobarbital, intravenous injection of an additional 60 mg/kg reduced, but did not abolish, the later waves of the response. One cat that survived a cumulative dose of 183 mg/kg continued to show a well-defined brain stem response. Even doses of barbiturate nearly incompatible with survival do not abolish this response.

Sedation in brainstem response audiometry

In many children, sedation is virtually essential for reducing myogenic interference during brainstem response (BSR) audiometry. The most widely accepted sedative for young children is chloral hydrate. Children who are tired before the sedation is given fall asleep much more quickly with sedation, and in turn, require fewer doses of chloral hydrate. Instructing the parents to keep the child tired has produced significant increases in percent of those sleeping after the first dose (z = 2.08, P less than 0.05).

Auditory brain-stem response and temperature: relationship in the guinea pig

The neurological applications of the auditory brain-stem response depend largely on the stability of the interval between the peaks of waves I and V. Using guinea pigs, it was demonstrated that hyperthermia and small temperature changes, as well as hypothermia, may affect interpeak latency (IPL) sufficiently to affect its clinical interpretation. The relationship between temperature and IPL is specified by a power function such that there is a 5.3% increase in IPL for a 1 degree C drop. Although the constant for humans may differ from that of guinea pigs, the results of this animal study demonstrate that the relationship between temperature and IPL is invariant from 27 degrees C to 40 degrees C.

A trial of Biolite ventilation tubes in children: is further use warranted?

A prospective controlled pilot study was undertaken in which Biolite (carbon-coated) ventilation tubes were placed in 44 ears and a conventional silicone tube in the contralateral ear. Long-term follow-up of these patients has revealed little difference in the incidence of tube occlusion or early extrusion. In addition, there were several disadvantages noted with the Biolite tubes: incomplete coating of the tube (especially within the lumen), shedding of the Biolite coating over time, "tattooing" of the tympanic membrane, poor otoscopic visibility, and the higher cost of these tubes. Since the Biolite tube has no documented advantages and, actually, several disadvantages, we believe its use in the treatment of middle ear disorders should be discontinued until significant benefits are demonstrated and present deficiencies are corrected.

Hearing loss induced by viscous fluids in the middle ear

Dextran solutions of low viscosity (7.5 centipoise) and high viscosity (2.2 poise) were instilled in turn into the middle ears of guinea pigs, using an open bulla preparation. The degree of conductive hearing loss induced was assessed by measurement of the cochlear microphonic. Both solutions produced a comparable degree of hearing loss which was frequency dependent, ranging from 30 dB at 500 Hz to almost zero at 4000 Hz. The results indicate that the degree of conductive hearing loss produced by a serous effusion in otitis media is due solely to an effect on compliance in the middle ear and is independent of the viscosity of the effusion.

Auditory brain stem responses in infantile spasms

Auditory brain stem evoked responses (ABRs) and behavioral thresholds were studied in 30 infants with infantile spasms to determine the level of the lesion causing their inattention to sound stimuli. ABR thresholds, peak latencies of waves I and V and the peak interval latency of wave V-I were measured; behavioral audiometric thresholds were determined through conditioned-orientation-reflex (COR) audiometry. Thirty per cent of the infants (9 cases) with infantile spasms showed ABR abnormalities with respect to age-matched controls. The ABR abnormalities were classified into partial disappearance of latter waves (5 cases), prolongation of the wave V-I peak interval (3 cases) and no response (1 case). These findings are clear evidence that brain stem involvement may occur in infantile spasms. Eighty-six per cent of the patients showed threshold elevation by behavioral audiometry which may reflect by cortical dysfunction inherent in psychomotor retardation, as there was no peripheral hearing loss. Our results reveal that brain stem involvement can occur in patients with infantile spasms and their poor responses to sound are due to psychomotor retardation.

Contributing generator of frequency-following response in man

A contributing generator of the frequency-following response (FFR) was identified in a patient with severe neurological impairment, by comparing latencies and phase shifts of the FFR to the latency of the auditory brainstem evoked responses (ABR), and by comparing the duration of the FFR to that of the acoustic stimulus. In this patient, the ABR comprised only waves I and II; activity in the inferior colliculus was not identified. Both onset and offset latencies and phase shifts of the FFR were substantially shorter than the latency of the first wave of the ABR. The duration of the FFR corresponded precisely to that of the acoustic stimulus. These results are interpreted as supporting the view that the cochlear microphonic potential (CM) contributes to the scalp-recorded FFR.

A recorder for off-line acquisition of brain stem auditory response data

A modified cassette tape recorder collects brain stem response data for later off-line analysis. This simple device permits assessments of brain stem function when a signal-averaging computer is not immediately available, and at locations not readily accessible to the computer.

Effect of site of stimulation on the guinea pig's electrically evoked brain stem response

Stimulation by a bipolar modiolus electrode yields a wider dynamic range than does monopolar stimulation at the same site. Stimulation via a single electrode in the scala tympani or scala vestibuli is characterized by a precipitous input-output function, but current passing from one scala to the other generates a discontinuous function with a shallow slope at low intensities and a steep slope at high intensities.

Brain stem response evoked by electrical stimulation of the round window of the guinea pig

The wave that is believed to correspond to wave V in man is an appropriate indicator of auditory nerve excitability because it is not contaminated by nonauditory neurogenic responses to electrical stimulation. The responses to direct electrical stimulation of the auditory nerve could be distinguished from the electrophonic response by the steep input-output function and constant latency of the former. Myogenic responses are prominent unless a muscle relaxant is administered.