Search PubMed⌕ Search

Biomedical subjects

C J Newth

Publications and source records attributed to C J Newth.

At least 73 records · Page 4Linked to original sources
PubMed1986

Pulmonary and systemic effects of increased negative inspiratory intrathoracic pressure in dogs.

Croup and epiglottitis, which cause greater than normal negative inspiratory intrathoracic pressure (NIIP), have been associated with pulmonary edema. To examine the effects of increased NIIP per se on blood gases, hemodynamics, and lung water content, we carried out 2 types of experiments in 18 anesthetized dogs. Short-term, low-pressure experiments (6 control dogs and 6 dogs that generated intratracheal pressures of -12 cm H2O during inspiration for 3 h) and long-term, high-pressure experiments (6 dogs that generated -20 cm H2O during inspiration for 6 h). In the short-term, low-pressure experiments, animals made to generate negative inspiratory pressure differed from control dogs by demonstrating decreased pleural pressure (p less than 0.01), increased arterial PCO2 (p less than 0.05), and decreased minute volume (p less than 0.05); no differences occurred in hemodynamic data (pulmonary arterial, left atrial, and aortic pressures and cardiac index) and in extravascular lung water (indicator dilution and gravimetric analyses). Similarly, in the long-term, high-pressure dogs, arterial PCO2 increased (p less than 0.05) and lung water was normal by gravimetric analysis. We conclude that both 3 and 6 h of increased NIIP cause CO2 retention but have minimal effects on hemodynamics and lung fluid exchange.

Animals↗
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

Preparation and evaluation of microencapsulated and coated ion-exchange resin beads containing theophylline.

Anion-exchange resin beads in the theophylline form were prepared and coated with paraffin or encapsulated with ethylcellulose by various methods; one of these products was subsequently coated with paraffin in order to achieve a wide range of release rates and patterns of release. The various products were subjected to rate studies, and it was found that the patterns of release and the rates could be controlled by the cross-linking of the resin and the coating procedures used. A medium and almost constant rate of release was obtained by using ethylcellulose microencapsulation, a coating of hard paraffin, or a combination of both. The amount of coating and the total amount of drug released was also determined.

Chemical Phenomena↗
PubMed1985

Pharmacokinetics of a sustained-release theophylline preparation in infants and preschool children with asthma.

Sustained-release theophylline formulations should be most useful in young children who have rapid clearance and long sleep intervals. Somophyllin-12 is a recently introduced, newly designed, bead-filled capsule. We tested its ability to provide adequate serum concentrations at steady state in 16 children ages 0.9 to 5.1 yr. On a 12 hourly dosing schedule, mean dose was 25.9 mg/kg per day, and mean fluctuation was 138%. Seven children (43.8%) had fluctuations less than 100%, whereas four children (25%) had fluctuations more than 200%. Six patients with excessive fluctuation (greater than 100%) were restudied on an eight hourly dosing schedule. Mean dose was 28.7 mg/kg per day, and fluctuation was 59%. Because of the excessive fluctuation (greater than 100%) experienced by half these young children, therapy with this product should be initiated with an eight hourly dosing schedule. However, when dose and dosing interval are subsequently individualized, many young children can be switched to twice daily dosing with its improved compliance and convenience.

Asthma↗
PubMed1985

Fatal pulmonary hypertension following renal transplantation.

We present a case of fatal pulmonary hypertension occurring in a child several years following renal transplantation for membranoproliferative glomerulonephritis. Premortem investigations failed to reveal a cause for the pulmonary hypertension. Histological features in the lung at autopsy were consistent with a diagnosis of PVOD. The possible common pathogenesis of these seemingly unrelated disorders is discussed.

Adolescent↗
PubMed1984

Radionuclide assessment of cardiac performance in cystic fibrosis. Reproducibility and effect of theophylline on cardiac function.

A study was designed to evaluate the reproducibility of right and left ventricular ejection fraction measurements (RVEF, LVEF) by equilibrium radionuclide angiography in cystic fibrosis (CF) and to determine the effect of the acute administration of aminophylline on RVEF and LVEF in this disease. Both RVEF and LVEF were measured at rest and during incremental supine bicycle exercise by equilibrium radionuclide angiography in 18 patients with CF. In 9 of these patients, radionuclide studies were repeated after an infusion of aminophylline (9 mg/kg), whereas the remaining patients had radionuclide studies repeated after a placebo infusion. No significant increase in mean RVEF or LVEF values either at rest or at peak exercise was seen after aminophylline infusion. In the patients who underwent sequential radionuclide studies without intervening active drug intervention, the mean (+/- standard deviation) variability in RVEF and LVEF measurements between the 2 studies was 2.6 +/- 2% and 3.6 +/- 2.9%, respectively. We conclude that (1) equilibrium radionuclide angiography is a reasonably reproducible technique for serial assessment of biventricular function at rest and during exercise in CF, and that (2) the acute administration of aminophylline does not augment cardiac function either at rest or during exercise in this disease.

Adolescent↗
PubMed1984

Radionuclide assessment of right and left ventricular function during bicycle exercise in young patients with cystic fibrosis.

Right and left ventricular performance during exercise was evaluated in 31 patients with cystic fibrosis using equilibrium radionuclide cineangiography. There were 21 males and 10 females (mean age 17, range 10.4 to 34.9 yr) with a wide range of clinical involvement. Thirteen patients had arterial desaturation at rest and an additional 4 became desaturated with exercise. Nine patients (29%) were unable to increase their right ventricular ejection fraction more than 5% during exercise. Left ventricular ejection fraction at rest was normal (greater than 55%) in all but 2, and with exercise, performance was impaired in 9 (29%). No relationship was found between resting or exercise radionuclide ejection fraction, M-mode echocardiography or pulmonary function studies. This study suggests that both right and left ventricular dysfunction may occur during stress in patients with cystic fibrosis without other conventional clinical signs or symptoms. Radionuclide cardiac angiography appears to be a safe method of assessing cardiac response to exercise in patients with chronic lung disease, and may be useful in evaluating therapeutic interventions.

Adolescent↗
PubMed1984

Central hypoventilation syndrome in pyruvate dehydrogenase complex deficiency.

The presentation and treatment of a central hypoventilation syndrome in a boy with pyruvate dehydrogenase complex (PDHC) deficiency are reported. Dephosphorylated PDHC was assayed in disrupted fibroblasts after pretreatment with dichloroacetate, a pyruvate dehydrogenase kinase inhibitor. Maximal specific activity of activated patient PDHC was 10% to 30% of control values. Patient PDHC activity was not increased by alterations in concentrations of pyruvate or cofactors (thiamine pyrophosphate [TPP], coenzyme A [CoA], oxidized form of nicotinamide adenine dinucleotide [NAD+]). Clinically, normalization of plasma lactate by a high-lipid diet did not prevent slowly progressive neurologic decline. The patient manifested intermittent ataxia, episodic profound weakness, moderate psychomotor retardation, ophthalmoplegia, and retinal pigment epithelial changes. A true central hypoventilation syndrome was documented on the basis of rigorous radiologic, electrophysiologic, and pulmonary function criteria. Theophylline, progesterone, and ritalin neither altered ventilatory response to CO2 nor permitted weaning from the ventilator. In contrast, peripheral chemoreceptor stimulants (intravenous doxapram; oral almitrine) effected an acute doubling of minute ventilation with appropriate decreases in PaCO2. However, a positive response to long-term therapy with almitrine could not be unequivocally shown. It was concluded that measurement of disrupted fibroblast PDHC following dichloroacetate activation constitutes an accurate assay for PDHC deficiency. PDHC deficiency must be considered in the differential diagnosis of the central hypoventilation syndrome; this appears to be the first report of such an association. Finally, a therapeutic trial of a peripheral chemoreceptor agonist is warranted in the management of central hypoventilation syndrome.

Almitrine↗
PubMed1983

Respiratory status of children with epiglottitis with and without an artificial airway.

During a ten-year period, 22 children from our 170 cases of acute epiglottitis had reliable records of arterial blood gas data. The arterial/alveolar (a/A) oxygen tension ratios were calculated, with a value less than 0.75 representing abnormal gas exchange. The mean a/A ratio for the whole group, 17 of whom already had an artificial airway, was 0.59 (range, 0.29 to 0.83). A subgroup of five children with blood samples taken during conservative treatment or before airway insertion had a mean a/A ratio of 0.62 (range, 0.49 to 0.77) without hypercapnia (mean Paco2, 32 mm Hg; range, 29 to 39 mm Hg), which seemed to be a late feature. Thirty-three percent of initial chest roentgenograms were abnormal, with the major disorder being atelectasis and/or consolidation. We propose that the radiologic and gas exchange abnormalities result from the common pathophysiologic mechanism of increased lung water.

Adolescent↗
PubMed1982

Comparison of nebulised sodium cromoglycate and oral theophylline in controlling symptoms of chronic asthma in pre-school children: a double blind study.

The efficacy of nebulised sodium cromoglycate and an oral theophylline solution at currently recommended doses were compared in one to six-year-old children with chronic asthma. Twenty-six children completed a 24-week double-blind trial of treatment with sodium cromoglycate (SCG), theophylline and a combination of both. The three regimens were administered, each for eight weeks, in a random sequence. SCG was administered by inhalation as a nebulised solution in standard doses of 20 mg qid and serum drug concentrations were recorded. Theophylline was given as liquid aminophylline. Dosage was individualised with the assistance of serum theophylline measurements and averaged 6.1 mg/kg/dose q6h. Patients had an average of 61% symptom-free days while on SCG and combination regimens, compared with only 46.5% for days free of symptoms when on theophylline alone (p less than 0.05). There was significantly less use of supplementary medication for acute symptoms (p less than 0.05) when on the combination of SCG and theophylline. No regimen was more frequently associated with symptoms of exercise intolerance or decreased appetite. Numerous adverse side effects to theophylline were recorded, but none were recognised with SCG. SCG is at least as effective as theophylline in controlling asthmatic symptoms in the 1-6-year-old age group.

Administration, Oral↗