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Biomedical subjects

R T Brouillette

Publications and source records attributed to R T Brouillette.

At least 55 records · Page 3Linked to original sources
PubMed1989

Diaphragm pacing in infants and children. A life-table analysis of implanted components.

Since 1976, we have implanted bilateral phrenic nerve electrodes for diaphragm pacing in 33 infants and children. This population includes 23 patients with congenital central hypoventilation syndrome (CHS), two with late onset CHS and hypothalamic dysfunction, three with hypoventilation associated with Chiari II malformation and myelomeningocele, and five with quadriplegia. Our experience, totalling 192 system-years and 96 patient-years of pacing, has enabled us to document the nature and frequency of problems related to the implanted components of the Avery Laboratories (S-232-1) pacemaker system when used in a pediatric population. By life table analysis, the mean time to need for replacement of any implanted component was 56.3 months. A total of 26 failures requiring component replacement occurred and were classified into four types: (1) receiver failure (15 cases), (2) electrode wire or wire insulation breakage (six cases), (3) infection requiring diaphragm pacer system removal (three cases), and (4) mechanical nerve injury (two cases). We conclude that the present diaphragm pacing system is effective but not without risk of biomedical component failure. The present system might be substantially improved by (1) a modified receiver design with a hermetic seal to prevent fluid penetration, (2) stronger, better insulated electrode wires, and (3) modifications of surgical technique and electrode type to prevent phrenic nerve damage.

Actuarial Analysis↗
PubMed1988

Apnea-onset definition significantly affects pneumogram results.

Pneumogram (PG) scoring methods have not been standardized. To determine the extent to which varying definitions for apnea-onset and apnea-termination will result in clinically significant differences in calculated apnea density (A6/D%) and periodic breathing, we analyzed 40 randomly selected PGs. All PGs were initially scored using end-expiration (EE) to mark the beginning of each apnea. As the second definition, peak inspiration (PI) was used to identify the onset of each apnea. All apneas greater than or equal to 6 s in duration and all episodes of periodic breathing were identified. The differences between results obtained by each definition were compared by paired t-test. The differences between the EE and PI definitions were statistically significant (p less than 0.01) for A6/D%, periodic breathing, longest apnea, and number of apneas greater than 11 s, with the PI definition consistently resulting in higher values. In summary, calculated PG results are significantly different, both clinically and statistically, depending on the scoring definition utilized for apnea-onset. Although each definition will yield results that are internally consistent, it is crucial that the normative standards used for comparison be derived utilizing the same scoring definition.

Cardiography, Impedance↗
PubMed1988

Fundamental considerations in pacing of the diaphragm for chronic ventilatory insufficiency: a multi-center study.

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results from the Center group yielded information on the early experience with diaphragm pacing important to its future application.

Diaphragm↗
PubMed1988

Diaphragm pacing in infants and children.

Since 1976 we have implanted bilateral diaphragm pacers in 34 infants and children: 26 with central hypoventilation syndrome (CHS), three with myelomeningocele, and five with quadriplegia. Compared to adults, several modifications have been necessary to achieve effective ventilation in infants and younger children. In all instances, a tracheostomy has been necessary due to impaired neuromuscular control of upper airway patency during pacing. Bilateral pacing has been necessary to achieve adequate ventilation; in the CHS children with normal awake ventilation, bilateral pacing during sleep eliminates the need for positive pressure ventilation. For the remaining children, adequate awake ventilation is achieved with bilateral pacing, thus permitting substantially greater mobility and limiting use of the ventilator to sleep time. Our longest survivor has now been paced for 10.7 years, and in no instance has phrenic nerve damage occurred secondary to electrical stimulation. Our current pacing regime is characterized by moderate respiratory rates (21 breaths/min), long interpulse intervals (95 ms), and short inspiratory times (0.6 sec), resulting in 50%-75% fewer stimuli/min compared to our previous regime. For all infants and children requiring 24-hour ventilatory assistance, our recent successes in maintaining ventilation using significantly fewer stimuli suggest that long-term continuous pacing is a realistic future goal.

Child↗
PubMed1988

Effects of almitrine on respiration in unanesthetized newborn rabbits.

We previously demonstrated that almitrine, a peripheral chemoreceptor stimulant, increased tidal volume (VT), expired minute ventilation (VE), and respiratory frequency (f) and decreased inspiratory (TI) and expiratory time (TE) in sleeping adult cats. We now hypothesized that almitrine would induce an increase in ventilation in a young animal model. Respiration was studied by the barometric method in 11 unanesthetized New Zealand White rabbit pups between 3 and 6 days of age. Recordings were made in 0.21 FIO2 at base line and after cumulative intraperitoneal infusions of almitrine (2.5, 5.0, and 7.5 mg/kg). The chamber pressure deflection (proportional to VT after appropriate calculation) was computer sampled at 200 Hz. At least 100 breaths for each dose in each animal were analyzed. We found that a 7.5-mg/kg intraperitoneal dose of almitrine increased f to 135 +/- 9% (SE) of base line and decreased TE and TI to 72 +/- 8% and 79 +/- 8% of base line, respectively. Changes in VE, VT/TI, and VT were not significant. Recognizing that apnea is associated with inadequate ventilation and a prolonged TE (failure of the "inspiratory on-switch"), these results, particularly the increase in f and decrease in TE, suggest that almitrine might be useful in treating apnea in preterm infants.

Almitrine↗
PubMed1988

Magnetic resonance imaging and computerized tomography in central hypoventilation.

Central hypoventilation syndrome (CHS) is a disorder of respiratory control. It may be an idiopathic primary disease or it may be the secondary consequence of an infectious process or Chiari II malformation. Clinical data suggest that the primary defect involves the brainstem respiratory centers. To date, pathologic evaluation has linked primary CHS with decreased density of neurons and myelinated nerve fibers in the medulla and brainstem gliosis, and absence of the external arcuate nucleus. Magnetic resonance imaging (MRI) is now considered the most reliable imaging technique for evaluating the brainstem. In the hope of finding gross structural abnormalities that might correlate with the clinical and pathologic features of CHS, we used MRI and computerized tomography (CT) to evaluate the brain, brainstem, and spinal cord of 17 infants and children with central hypoventilation (11 primary, 6 secondary). Each of the 11 children with primary CHS demonstrated a normal brainstem and spinal cord by MRI. However, 9 of 11 infants had mild ventricular dilatation and modest prominence of the sulci interpreted as either mild atrophy or mild extraventricular obstructive hydrocephalus. Results of studies in the one child with postinfectious disease were normal. The 5 infants with Chiari II malformation demonstrated characteristic brainstem changes. MRI results modified clinical care, resulting in symptomatic improvement after hindbrain decompression by cervical laminectomy in 1 infant and surgical drainage of syringobulbia in 1 child. In summary, in primary CHS, the MRI and CT provided evidence for a more diffuse CNS process rather than a specific brainstem lesion. Such a lesion may be too small or too subtle to resolve with MRI or CT. In secondary central hypoventilation, MRI modified surgical management in 2 cases, resulting in symptomatic improvement of hypoventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Arnold-Chiari Malformation↗
PubMed1987

Sudden infant death syndrome: 1987 perspective.

The pathophysiology of SIDS remains unknown. Although a multifactorial cause appears plausible on the basis of available data, new data are needed to determine which components of this multifactorial hypothesis are most important and whether other factors need to be added. We need to better understand control of breathing in the newborn infant and the manner in which maturation of cardiorespiratory control progresses during infancy. The unique period of vulnerability for SIDS, in which risk is less in the neonate than at 2 to 6 months of age, remains unexplained. Is there a worsening in some aspect of cardiorespiratory control in infants destined to die of SIDS? An improved understanding of the increased risk in black infants, preterm infants, and infants with intrauterine drug exposure, although only a small percentage of all SIDS deaths, should contribute substantially to our understanding. Appropriately designed and well-controlled prospective studies are needed in asymptomatic infants at risk, to determine the true contemporary nonintervention rate of SIDS and the extent to which any assessment or intervention lowers this rate. Prospective pneumogram screening studies have demonstrated significant group differences in respiratory patterns in normal infants compared with later SIDS victims, but have failed to achieve sufficient sensitivity and specificity to be useful for populationwide prospective screening. To assess aspects of brainstem cardiorespiratory control in addition to those assessed by a conventional pneumogram, future studies will need to be based on an expanded or modified technology. On the basis of both physiologic considerations and available technology, addition of an oxygen saturation channel offers the most promise for providing a more comprehensive assessment of cardiorespiratory control. If there is an underlying deficiency in asphyxic arousal responsiveness, for example, with or without other respiratory control deficits, continuous monitoring of oxygen saturation as part of a second-generation pneumogram system currently has the greatest promise for providing a modified pneumogram assessment of greater clinical use. The use of continuous oxygen saturation as a home monitoring technique should also be investigated. Power spectrum analysis of cardiorespiratory variability also appears to have potential advantages over conventional pneumogram analyses, and needs to be evaluated in prospective studies. The following statements summarize our current knowledge regarding SIDS, apnea, pneumograms, and home monitors: The cause(s) of SIDS remains unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Apnea↗
PubMed1987

Comparison of respiratory inductive plethysmography and thoracic impedance for apnea monitoring.

Thoracic impedance apnea monitors may fail to detect obstructive apnea, may falsely alarm when the infant is breathing, and may confuse cardiac artifact with respiratory impedance. Therefore, we compared the performance of a respiratory inductive plethysmograph and a thoracic impedance monitor with a reliable measure of airflow, either nasal CO2 or pneumotachograph, during 29 studies in 28 patients referred for sleep laboratory evaluation. Sleep time averaged 72 +/- 37 (SD) minutes. The inductance plethysmography and the impedance monitor detected 99.6% +/- 0.6% and 98.3% +/- 3.0% of breaths, respectively. However, in two studies, the impedance monitor detected many extra breaths, once because of cardiac-induced impedance changes and once because of partial airway obstruction-induced impedance changes. In 11 studies, cardiac artifact was sometimes misinterpreted as a breath by the impedance monitor. The impedance monitor, but not the inductance plethysmograph, missed breaths following sighs in 16 of 29 studies. Both monitors detected all 60 episodes of central apnea. The inductance plethysmography detected 35 of 38 episodes of obstructive apnea, but the impedance monitor identified only two such events. Apnea was detected falsely four times by the inductance plethysmograph and 14 times by the impedance monitor. These results suggests that a respiratory inductive plethysmograph would have significant advantages over impedance monitoring, including the ability to detect obstructive apnea, and freedom from cardiac artifact.

Apnea↗
PubMed1987

Risk factors associated with candidemia in the neonatal intensive care unit: a case-control study.

Systemic candidiasis, especially candidemia, is an increasing problem among high risk neonates. Although possible predisposing factors have been suggested, no case-control study has evaluated potential risk factors. By retrospective chart review we identified 21 infants admitted to the neonatal intensive care unit between 1976 and 1983 (0.9% of all admissions) who had documented nosocomial candidemia before 4 months of age. Twenty patients were matched to a control infant with similar birth weight and date of admission. We found that the median durations of exposure to the following risk factors were significantly longer in patients compared with controls: hyperalimentation; intravenous fat emulsion; endotracheal tubes; and/or tracheostomies and antibiotic therapy. However, by discriminant analysis, duration of antibiotic therapy remained the variable most strongly (and independently) associated with the development of candidemia. Treatment of the 22 episodes of candidemia was variable including catheter removal alone in 12 and a combination of catheter removal, amphotericin, 5-fluorocytosine and/or ketaconazole in the others. Although the overall mortality for the series was 5 of 20 cases (25%), no infant larger than 2000 g died. We conclude that development of candidemia in neonates is associated with, and possibly caused by, prolonged exposure to antibiotics (as documented by multivariate analysis), hyperalimentation, intravenous fat emulsion and tracheal intubation (as documented by univariate analysis). To the greatest extent possible consistent with good clinical care, exposure to these risk factors should be minimized in high risk neonates.

Anti-Bacterial Agents↗
PubMed1986

Successful reinnervation of the diaphragm after phrenic nerve transection.

A 16-month-old infant presented with bilateral diaphragmatic paralysis and respiratory failure after removal of a thoracic teratoma. Right diaphragmatic function recovered after end-to-end anastomosis of a transected phrenic nerve. We conclude that phrenic nerve repair can restore diaphragmatic function and should be attempted in selected cases of diaphragmatic paralysis due to phrenic nerve injury.

Diaphragm↗
PubMed1986

Neonatal aortic thrombosis: recent experience.

To evaluate the course, use of diagnostic modalities, management, and outcome of aortic thrombosis associated with umbilical artery catheterization, we reviewed 20 cases of aortic thrombosis diagnosed by ultrasonography (n = 16) or aortography (n = 4) over 4 years. Fourteen of 20 infants had severe perinatal asphyxia, suggesting that asphyxia predisposes to aortic thrombosis. Ultrasonography provided information about the size, location, and configuration of the thrombus and was useful in following thrombus size with therapy. Radionuclide renography-scintigraphy demonstrated abnormal renal function in all 11 patients scanned. Six patients with minor thrombosis (hypertension as the only sign) improved without specific therapy. Nine infants had moderate thrombosis (multiple signs but normal urine output); all survived with a variety of therapies; two were not given anticoagulant or fibrinolytic agents; three improved with heparin alone; and one had surgery without recurrence of the thrombus. Resolution of moderate thrombosis followed streptokinase therapy in two of three infants. All five babies with anuria from major thrombosis died. Hepatic infarction associated with aortic thrombosis was found in three of three autopsies.

Aorta, Abdominal↗
PubMed1986

Effects of birth weight and ethnicity on incidence of sudden infant death syndrome.

Sudden infant death syndrome occurs with increased frequency in low birth weight infants and in black infants. The degree to which the higher LBW rate among blacks might explain this higher SIDS rate is unknown. To address this question, we analyzed the 1233 SIDS deaths that occurred among 252,376 neonatal survivors in Cook County from 1975 to 1980, using computer-coded matched infant birth and death records. Birth weight and ethnic group were identified. The overall SIDS rates in blacks, Hispanics, and whites were 5.1, 1.2, and 1.3/1000 neonatal survivors, respectively. Within each ethnic group, the SIDS rates increased progressively with decreasing birth weight. Within the less than or equal to 1500 gm birth weight groups, the SIDS rates were 16.4, 3.9, and 5.5/1000 neonatal survivors in blacks, Hispanics, and whites. Using direct standardization, we found that 27% of the SIDS rate disparity between blacks and whites could be explained by the higher LBW rate in blacks (14% vs 6% in whites). The good outcomes in both LBW and SIDS rates for the Hispanic population were unexpected because, like blacks, Hispanics are socioeconomically disadvantaged. Findings for this group suggest that the remaining 73% of the increased SIDS rate in blacks cannot be attributed in a straightforward manner to differences in income or educational attainment.

Black or African American↗
PubMed1986

Effects of almitrine on genioglossal and diaphragmatic electromyograms.

We previously demonstrated dose-dependent increases in both hypoglossal and phrenic electroneurograms after almitrine in anesthetized, paralyzed, and vagotomized cats. We have now investigated the effect of this peripheral chemoreceptor stimulant on diaphragmatic and genioglossal (GG, an upper airway-maintaining muscle) electromyograms in five unanesthetized, chronically instrumented, spontaneously breathing adult cats during slow-wave sleep. In 12 studies almitrine doses of 1.0-6.0 mg/kg increased inspired minute ventilation (VI), frequency (f), and tidal volume (VT) and decreased expiratory time (TE). However, almitrine doses as high as 6.0 mg/kg failed to augment phasic inspiratory GG activity. To determine why almitrine induced phasic inspiratory upper airway activity in anesthetized, vagotomized cats but not in sleeping cats, additional studies were performed. In four dose-response studies in three pentobarbital-anesthetized cats, almitrine, 1.0-6.0 mg/kg, did not produce phasic inspiratory GG activity. Almitrine did induce phasic inspiratory GG activity in two of three studies in three vagotomized, tracheostomized, alpha-chloralose-urethan-anesthetized cats. These results suggest that almitrine would not be useful in obstructive sleep apnea, yet because almitrine markedly increased VI, f, and VT and decreased TE in unanesthetized sleeping cats the drug may be effective in patients who lack normal central neural respiratory drive, such as the preterm infant.

Almitrine↗
PubMed1986

Respiratory dysrhythmia. A new cause of central alveolar hypoventilation.

An infant developed chronic respiratory failure after aseptic meningoencephalitis at 5 months of age. Neurologic evaluations at 16 and 17 months were normal except for an abnormal pharyngeal stage of swallowing, lower extremity hypotonia, and a mild left hemiparesis. Spontaneous breathing during sleep at 16 months was characterized by alveolar hypoventilation, athetoid truncal movements, and disorganized respiratory muscle activity. At 27 months of age, improvement in sleep-related breathing was accompanied by a change in respiratory pattern characterized by alternating inspiratory and expiratory muscular activation. The findings indicate that disorganized as well as diminished output from the central respiratory pattern generator may result in central alveolar hypoventilation.

Chronic Disease↗
PubMed1986

Ventilatory effects of almitrine bismesylate in congenital central hypoventilation syndrome.

Patients with congenital central hypoventilation syndrome (CCHS) lack hypercapnic and hypoxic stimulation of ventilation but have demonstrated carotid body function in response to hyperoxia and to pharmacological stimulation with doxapram. This study investigated the ventilatory effects of almitrine bismesylate, a carotid body stimulant, in 12 patients with CCHS. Measurements of minute ventilation, tidal volume (VT), respiratory rate (RR) and transcutaneous PO2 (TCPO2) were taken before and after administration of 4.5 mg/kg and 6 mg/kg of almitrine. Twenty-four hour pharmacokinetic studies were performed in 7 patients who received 4.5 mg/kg and in 6 patients who received 6 mg/kg almitrine. There was no significant improvement in ventilatory and gas exchange parameters at either dose of almitrine despite appropriate peak serum concentration of the drug at the time of the studies. These results suggest that almitrine is not a useful ventilatory stimulant in children with CCHS.

Almitrine↗
PubMed1985

Diaphragmatic pacing in infants: techniques and results.

Phrenic nerve pacing was employed in 8 infants with central hypoventilation syndrome. Their ages ranged from 2.5 to 8.5 months. Preoperative diagnosis was established by demonstrating inadequate ventilatory response to hypercapnia and hypoxia. Percutaneous measurements of phrenic nerve conduction time and diaphragmatic action potentials were performed prior to operation to assess the feasibility of diaphragmatic pacing. A single anterolateral thoracotomy incision was used for both electrode placement in the chest and receiver implantation in the flank. The stimulating electrode was inserted around a segment of intrathoracic phrenic nerve isolated with pleura and perineural blood supply. Follow-up is available on all patients six months to 8 years postoperatively. There were no complications or deaths related to the procedure. In all patients, bilateral phrenic nerve stimulation allowed either marked decrease in or discontinuation of positive-pressure ventilation. Phrenic nerve pacing can be performed safely in infants. It provides an effective alternative method for ventilatory support without the drawbacks of positive-pressure ventilation.

Action Potentials↗
PubMed1985

Respiratory insufficiency in newborns with abdominal wall defects.

Respiratory failure in newborns with abdominal wall defects has been attributed to increased intra-abdominal pressure and elevation of the diaphragm after closure. Despite surgical techniques designed to minimize intra-abdominal pressure, we have observed prolonged respiratory insufficiency in several such infants. We reviewed the charts of 108 infants from 1975 to 1982 who had abdominal wall defects: 53 with gastroschisis, 29 with small omphaloceles, 22 with liver-containing or giant omphaloceles (GO), and four with cloacal exstrophy. Nine infants with GO (41%) had prolonged respiratory insufficiency and five died. Infants with GO required longer periods of oxygenation and ventilation (P less than .001, ANOVA) than infants with other abdominal wall defects. Clinical observation suggested that infants with GO have a small, narrow thorax. We obtained detailed measurements from the chest radiographs of infants in all groups. After correction for birth weight, babies with GO had smaller chest widths (P less than .001) and lung areas (P less than .05) than infants with other abdominal wall defects. At autopsy, one newborn with GO was found to have severe pulmonary hypoplasia. Prolonged respiratory insufficiency in infants with GO may be explained by pulmonary hypoplasia and/or by a narrow chest deformity which limits lung expansion.

Abdominal Muscles↗