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Biomedical subjects

I Mitchell

Publications and source records attributed to I Mitchell.

At least 55 records · Page 3Linked to original sources
PubMed1993

The measurement of thoraco-abdominal asynchrony in infants with severe laryngotracheobronchitis.

Retractions of the lower ribcage (chest wall distortion [CWD]) during inspiration are frequently observed with moderate to severe respiratory disease in the infant. Laryngotracheobronchitis (LTB) results in a reversible partial airway obstruction with severe CWD. We wished to measure the motion of the chest wall during distortion to determine the changes in minute ventilation (VE) and to evaluate this clinical sign as a means of assessing disease severity. The respiratory inductance plethysmograph was used to determine the distortion of the lower chest wall, and distortion was correlated with VE, measured at the mouth, in six infants with severe LTB and ventilatory failure. As the conditions of these infants improved, the CWD decreased with decreasing transcutaneous carbon dioxide tension (tcPCO2), VE increased from 0.27 +/- 0.12 L.min-1 x kg-1 at a tcPCO2 of 64 mm Hg to 0.64 +/- 0.06 L.min-1 x kg-1 when the tcPCO2 had fallen to 28 mm Hg. Over the same change in tcPCO2, the tidal volume (VT) increased from 4.8 +/- 0.5 ml.kg-1 to 15.7 +/- 1.4 ml.kg-1. In the most severe disease state, the excursion of the chest wall (as an inductance) was -14 +/- 3 mV in severe obstruction, but increased to 75 mV +/- 4 mV with resolution of the illness. The timing and vector of movement of the abdomen and chest wall were expressed as a Lissajous figure, which is measured as a phase angle. The severity of the disease process, as determined by tcPCO2 was directly related to the phase relationship, and thus reflected both VE and VT. The severity of the CWD may be assessed rapidly by the use of Lissajous figures.

Abdomen↗
PubMed1993

Apnea and factitious illness (Munchausen syndrome) by proxy.

OBJECTIVE: Munchausen syndrome by proxy (MSP) is recognized in the differential diagnosis of apparent life-threatening events, but the early signs and the full spectrum of this presentation are not well recognized. We aim to describe MSP presenting with apnea to illustrate this spectrum and the evolution in our management over a period of 10 years. PATIENTS AND RESULTS: Eleven children in five families seen in one institution and assessed by one team are described in detail. The children had apnea and/or pallor, but with a wider age range than usually seen with apparent life-threatening events, sometimes associated with other injuries, and a large percentage of parents were health care providers. In no case was apnea witnessed by health care professionals other than the parents. There were frequent disagreements in management between professionals and, consequently, delays in considering the diagnosis at first. There were two deaths. A team developed, allowing the diagnosis of MSP to be considered sooner and the cases to be assessed and managed consistently. CONCLUSION: MSP is part of child abuse, and it needs to be recognized by all physicians. Family assessment is required and the development of a team interested in MSP facilitates assessment and management.

Apnea↗
PubMed1992

Intensive care course and outcome of patients infected with respiratory syncytial virus.

PICU admissions of 97 children positive for respiratory syncytial virus on fluorescent antibody screening were reviewed; 68% of 44 patients without history of preceding disease (Group I) and 79% of 53 patients with preceding pulmonary, cardiac, or other disease (Group II) required ventilation. In Group I ventilated children weighted significantly less (P = 0.001) and were of lower chronological (P = 0.02) and post-conceptional ages (P = 0.02) than those not ventilated. Eighteen infants ventilated for apnea weighted significantly less (P = 0.003), were more often born at less than or equal to 37 weeks gestation (P = 0.001) and were at lower post-conceptional age than 11 infants ventilated for progressive respiratory deterioration. There was no significant difference in mean weight, chronological age, post-conceptional age, CO2, or pH between 12 admissions with BPD who required ventilation for RSV infection and 5 who did not require ventilation. Ribavirin administration to five ventilated patients with BPD did not significantly alter the duration of intubation of PICU stay. Six patients with cardiac disease required longer periods of ventilation than others (Group I, P = 0.001; all others in Group II, P = 0.04). No deaths occurred in Group I, while 6 of 53 (11%) patients in Group II died. In this series immuno compromise placed patients at greatest risk of dying. Mechanical ventilation can be safely managed in previously healthy, RSV infected infants and should be initiated before significant cardiorespiratory compromise arises.

Adolescent↗
PubMed1992

On controlling inert gas narcosis.

Ten subjects breathed experimental mixtures of 20% and 35% nitrous oxide (N2O) balanced with oxygen and then aligned a pointer with a target using vision, kinesthesis, or combinations of these senses. In a prior session the subjects had been trained on the task with feedback while breathing N2O. The results showed that N2O did not influence variable error (VE), constant error, (CE), or absolute CE, but perceptual conditions influenced VE and absolute CE. These results suggest that the demonstration by Legge (1965) of changes in the variability and accuracy of matching on this task under N2O are indicative of changes in response bias and/or attention rather than perceptual sensitivity. It is argued that narcosis slows rather than distorts information processing. Slowing is accompanied by strategic changes that may be maladaptive. This suggests that, contrary to conventional wisdom, the safety and efficiency of divers exposed to narcosis could be improved with training.

Adult↗
PubMed1992

Histamine challenge in young children using computerized lung sounds analysis.

The use of the histamine challenge test (HCT) for the diagnosis of asthma has so far been limited to older children who can perform spirometry consistently. Recently, wheeze detection by tracheal auscultation with analog recording into a tape recorder has been utilized in young children in place of spirometry. Wheezing can also be identified using computerized lung sounds analysis (LSA) by a typical pattern on spectral analysis. Our aim was to develop a practical computerized system in which the response to histamine could be identified in an objective manner and documented on hard copy. Lung sounds were recorded with a Hewlett-Packard HP 21050A contact sensor placed over the right upper anterior chest. Sounds were amplified, band-filtered (50 to 2,000 Hz), and digitized at a sampling rate of 5.5 kHz into a Macintosh SE computer, and spectral LSA was performed. To validate our method, six older children (ages 9 to 16 years) with mild or moderate asthma underwent HCT. The identification of typical wheezing pattern (discrete, high-amplitude power peaks) on LSA was compared to 20 percent fall in FEV1 (PC20) and symptoms (cough, wheeze, chest tightness). In five children, the histamine concentration required to produce the characteristic wheezing pattern on LSA was half that required to produce a 20 percent fall in FEV1. In the sixth patient, wheezing on LSA and PC20 occurred at the same histamine concentration. To determine the technique's applicability to young children, we then studied six young asthmatic children (age 2 to 5 years). All children showed the wheezing pattern at a histamine concentration of 25 percent or 50 percent (one or two steps prior) to that producing symptoms (cough, wheeze, chest tightness) or wheezing on tracheal auscultation. Six age- and sex-matched nonasthmatic children (control subjects) did not show this pattern on LSA and had no symptoms or tracheal wheeze with HCT. We describe a sensitive method enabling application of HCT to young children who are unable to perform spirometry. This method is as sensitive as, and often more sensitive than, conventional PC20 with spirometry or tracheal auscultation.

Adolescent↗
PubMed1991

Comparison of three forward mutation systems in Saccharomyces cerevisiae for sensitivity to polycyclic and heterocyclic compounds.

Forward mutation to cycloheximide resistance, L-canavanine resistance and DL-alpha-aminoadipic acid resistance in Saccharomyces cerevisiae wild-type strain S7a was tested for sensitivity to nine mutagens in treat-and-plate assays. Eight of these agents, 2-aminofluorene, 2-acetylaminofluorene, benzo[a]pyrene, benzidine, cyclophosphamide, acriflavine, 7,12-dimethylbenz[a]anthracene and 2-aminoanthracene were known or suspected to be difficult to detect whilst one, methyl methanesulphonate, was known to be very active in yeast. Forward mutation to cycloheximide resistance was, overall, the most sensitive system, detecting all nine agents under optimal conditions, although neither benzidine nor benzo[a]pyrene were consistently positive. Mutation to adipic acid resistance occasionally gave responses superior to those at the cycloheximide loci, but mutation to canavanine resistance was never more sensitive than the cycloheximide resistance system. We conclude that forward mutation in strain S7a using both cycloheximide and adipic acid resistance loci is capable of detecting the genetic effects of a range of polycyclic and heterocyclic compounds with greater sensitivity than is seen in other published gene mutation assays with yeast. Although sensitivity is much lower than in bacterial assays, such yeast assays provide a reasonable alternative to bacterial genotoxicity screening for agents such as potent bactericides.

2-Aminoadipic Acid↗
PubMed1990

Congenital tracheal stenosis in Pfeiffer syndrome.

We report an infant with Pfeiffer syndrome (acrocephalosyndactyly type V) and a solid cartilaginous trachea lacking rings. This airway abnormality has been reported in a child with Crouzon syndrome but has not been described in Pfeiffer syndrome.

Acrocephalosyndactylia↗
PubMed1989

Cavopulmonary anastomosis as long-term palliation for patients with tricuspid atresia.

Prior to 1970, most patients with tricuspid atresia (TA) and reduced pulmonary blood flow were palliated by means of a systemic to pulmonary artery shunt (SPAS). In Birmingham between 1967 and 1988, 19 patients with TA (aged 16 days to 23 years, mean 3.8 years) have undergone side-to-side cavopulmonary anastomosis (CPA) with preservation of pulmonary artery continuity. One had undergone a previous right Blalock-Taussig shunt and in 1 patient with left and right SVCs, bilateral CPAs were performed. Nine patients were less than 1 year old at the time of operation. There were no operative deaths. One late death occurred due to pneumonia. Immediate clinical improvement occurred in all cases. Six symptomatic patients subsequently required further surgery (mean interval between operations 8.9 years, range 4.6-14.2 years). The remaining 12 patients have recently been reviewed. Mean follow-up was 9.5 years (range 5 weeks to 21 years). Exercise tolerance remains good (9 in NY-HA Class 1 or 2) and resting transcutaneous oxygen saturations are higher (mean 85%, range 70%-89%) compared with preoperative values (P less than 0.01). In small children, CPA avoids the complications of SPAS and, in some patients, may itself achieve adequate long-term definitive palliation.

Adolescent↗
PubMed1989

Divergent effects of interferons on the growth of human benign prostatic hyperplasia cells in primary culture.

Epithelial cells from human benign prostatic hyperplasia tissues were grown in primary cultures for up to 21 days and the effects of interferons on the growth of the cells were investigated. Interferon-alpha (Wellferon) showed growth inhibition both in the presence and in the absence of 3 x 10(-10)M testosterone propionate (TP) whereas interferon-gamma stimulated growth in a dose dependent manner under similar conditions. Interferon-beta had little effect on growth at the dose levels used in the study. The growth inhibition by interferon-alpha can be induced after stimulation of growth is achieved either with TP or with interferon-gamma. Implications of these findings for clinical use of these lymphokines is discussed.

Cell Division↗
PubMed1989

Enzyme studies in human transitional cell carcinoma of the urinary bladder.

The activities of six enzymes of carbohydrate metabolism were estimated in tissue samples from 99 patients with transitional cell carcinoma of the urinary bladder undergoing transurethral resection. The results were analysed according to the stage of the disease and the malignancy grade of the carcinoma. There were statistically significant differences in the activities of three enzymes between various stages and grades. The activities of phosphofructokinase (PFK), alpha-glycerolphosphate dehydrogenase (alpha-GPDH), and phosphohexose isomerase (PHI) showed significant decreases with increased stage and grade. Of the total of 64 patients with superficial disease at presentation, five developed progressive disease during the course of this investigation. The activities of the three enzymes in these patients were compared to the median values for the group of patients with superficial disease. The activity of PFK was observed to be below the median value in all the five patients whereas the activities of alpha-GPDH and PHI showed similar patterns in four of the five patients. These preliminary data indicate that, in association with established clinical parameters, the measurement of the activity of these three enzymes may prove useful in selecting patients with an increased potential for developing progressive disease.

Adult↗
PubMed1989

Home oxygen therapy. Outcome of infants discharged from NICU on continuous treatment.

Forty-four oxygen-dependent infants were discharged home in oxygen from an NICU during an 8-year period. Survivors were followed for 3 years. The infants' discharge diagnoses were bronchopulmonary dysplasia (BPD) (39), sleep apnea (2), and congenital cardiac defects (3). The five infants who had diagnoses other than BPD all died, but 34 of 39 infants with BPD survived. Supplemental oxygen was discontinued at a mean age of 13.4 months. The infants with BPD experienced health, growth, nutritional, neurodevelopmental and sensory problems that necessitated frequent rehospitalizations and utilization of a variety of medical and support services.

Bronchopulmonary Dysplasia↗
PubMed1989

Narcosis has additive rather than interactive effects on discrimination reaction time.

A central feature of the impairment in performance produced by inert gas narcosis, which poses a threat to divers breathing compressed air, is a slowing of reaction time (RT). To investigate the locus of this slowing, the effects of 35% nitrous oxide on Crossman's confusion function were determined using line-length and weight discrimination tasks, with accuracy held constant. For both tasks narcosis slowed RT by increasing the intercept rather than the slope of Crossman's function. These results are interpreted in terms of additive factors method logic as being consistent with the predictions of the slowed processing model that has been proposed to account for the effects of narcosis on human performance.

Confusion↗
PubMed1988

Diffuse necrotizing tracheobronchitis: an acute and chronic disease.

Necrotizing tracheobronchitis (NTB) is characterized by acute episodes of airway obstruction, hypercarbia, and lack of chest movement in mechanically ventilated neonates. Emergency bronchoscopic removal of necrotic tissue is essential for survival. Although postmortem lesions extend into smaller bronchi, survivors have not demonstrated residual tracheobronchial abnormalities. Two infants were treated successfully for NTB but succumbed to diffuse tracheobronchial strictures with progressive pulmonary hyperinflation. A third neonate with esophageal atresia and left pulmonary agenesis developed NTB. Despite initial postbronchoscopic improvement, the infant died at age 6 weeks with diffuse obstructing NTB. All three infants required endotracheal intubation and mechanical ventilation. High-frequency jet ventilation was not used. Tracheal cultures for fungi, bacteria and viruses were negative. Successful treatment of NTB may be followed acutely by recurrence of NTB and chronically by diffuse tracheobronchial strictures and emphysema.

Acute Disease↗
PubMed1987

Antireflux surgery in infants with bronchopulmonary dysplasia.

We reviewed the medical records of nine infants with severe bronchopulmonary dysplasia and gastroesophageal reflux who underwent fundoplication-gastrostomy surgery. All the infants were born prematurely, required preoperative mechanical ventilation, and were failing to thrive. The operative procedure was well tolerated by all the infants. Seven patients were extubated by day 11, and two patients required long-term ventilation. There were two postoperative deaths, both attributed to acute respiratory deterioration followed by cardiorespiratory failure. The postsurgical respiratory response was observed to be a rapid decrease in oxygen requirements and an absence of further aspiration episodes. A mean decrease of 0.14 in fractional inspired oxygen concentration was noted by 30 days postoperatively, and by 180 days the decrease in fractional inspired oxygen concentration was 0.22. All infants were fed by gastrostomy by postoperative day 4, with no evidence of clinical reflux. The nutritional response was noted to be an increase in growth velocity with increasing age (ie, catch-up growth) and ease of feeding. At both 30 and 180 days postoperatively, the mean growth velocity was more than double the preoperative growth velocity. In addition, ease of postoperative feeding reduced the nursing care requirements and allowed earlier discharge from hospital. Fundoplication and gastrostomy is effective in facilitating growth and feeding in addition to decreasing oxygen requirements in infants with severe bronchopulmonary dysplasia and gastroesophageal reflux.

Bronchopulmonary Dysplasia↗