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Biomedical subjects

N B Pride

Publications and source records attributed to N B Pride.

At least 109 records · Page 6Linked to original sources
PubMed1984

Computed tomography in pre-operative assessment of bullous emphysema.

Nine patients with bullous emphysema for which surgery was being considered have been investigated with computed tomography (CT). In six out of nine patients (67%) CT showed more extensive disease or bilateral disease where only unilateral was suspected from postero-anterior and lateral chest radiographs. Only one patient proceeded to surgery and post-operative CT showed satisfactory re-expansion of the compressed lung. Surgery was abandoned in one patient as a result of the CT findings. Computed tomography is of value in patients with bullous emphysema in assessing the extent of disease and may assist the surgeon in operative planning.

Adult↗
PubMed1984

The effects of oral almitrine on pattern of breathing and gas exchange in patients with chronic obstructive pulmonary disease.

Almitrine at a low dose of 100 mg orally significantly raises PaO2 and lowers PaCO2 in patients with chronic obstructive pulmonary disease, compared with placebo, when they were breathing air or 28% oxygen. The estimated ideal alveolar-arterial PO2 difference was less after almitrine compared with placebo, when patients were breathing either air or 28% oxygen. After almitrine overall ventilation breathing air increased by 10% but this did not reach statistical significance. During 28% oxygen breathing almitrine hardly altered overall ventilation but the inspiratory duty cycle (Ti/Ttot.) decreased and mean inspiratory flow rate (VT/Ti) increased compared with placebo. These changes were significant on a paired t-test (P less than 0.05). Changes in both volume and pattern of breathing may explain the improved gas exchange in the lung after almitrine.

Administration, Oral↗
PubMed1983

Dose-response curves to inhaled beta-adrenoceptor agonists in normal and asthmatic subjects.

We have compared bronchodilator dose-response curves to inhaled salbutamol in seven normal and eight asthmatic subjects. In all normal subjects maximal bronchodilatation measured by partial flow volume curves was achieved at a cumulative dose of 110 micrograms. The dose necessary to produce half maximal response (ED50) was 23 +/- 2 micrograms (mean +/- s.e. mean) with a range of 18-28 micrograms. In asthmatic subjects maximal bronchodilatation measured by FEV1 and by maximal flow volume curves was achieved at significantly higher (P less than 0.01) doses of salbutamol with a mean ED50 of 83 +/- 28 micrograms and range of 25-251 micrograms. There was a significant (P less than 0.05) correlation between ED50 and % predicted baseline FEV1. This is more likely to reflect impaired access of drug for airway beta-adrenoceptors than impaired beta-adrenoceptor function in asthma. In five asthmatic subjects dose-response curves to salbutamol and isoprenaline were compared and found to be similar, thus providing no evidence that salbutamol is a partial agonist in vivo, as it appears to be in vitro.

Adrenergic beta-Agonists↗
PubMed1983

Pattern of breathing and gas exchange following oral almitrine bismesylate in patients with chronic obstructive pulmonary disease.

Almitrine bismesylate (100 mg orally) significantly raised PaO2 and lowered PaCO2 in six patients with chronic obstructive pulmonary disease, compared to placebo, when they were breathing air or 28% oxygen. The estimated ideal alveolar arterial PO2 difference (AaDO2) was less after almitrine bismesylate compared to placebo, when patients were breathing either air or 28% oxygen. After almitrine bismesylate overall ventilation breathing air increased by 10% but this did not reach statistical significance. During 28% oxygen breathing, almitrine bismesylate hardly altered overall ventilation but the inspiratory duty cycle (TI/TTOT) decreased and mean inspiratory flow rate (VT/TI) increased compared to placebo. These changes were significant on a paired T test (P less than 0.05). The improvement in AaDO2 correlated with the rise in VT/TI (r = 0.67, P = 0.02) and thus we suggest that changes in both volume and pattern of breathing might explain the improved gas exchange in the lung after almitrine bismesylate .

Administration, Oral↗
PubMed1982

Measurement of pulmonary erythromycin concentration in patients with lobar pneumonia by means of positron tomography.

The concentration achieved in the infected tissue is of fundamental importance in the use of antibiotics. Erythromycin labelled with the positron-emitting nuclide carbon-11 and positron tomography were used to compare local concentrations of this antibiotic in the pneumonic and unaffected lungs of five patients with lobar pneumonia. The time course of uptake of erythromycin into the extravascular compartment (i.e., the intracellular, interstitial, and alveolar compartments) of the pneumonic lung was measured. The mean extravascular concentrations obtained during the first hour after an intravenous injection of 270 mg erythromycin lactobionate were similar in the pneumonic lung and the unaffected lung (5.5 +/- 2.2 and 6.6 +/- 2.2 micrograms/g, respectively). An effective concentration of erythromycin was reached in the pneumonic lung within 10 min of the injection and was maintained throughout the period of measurement (60 min).

Acute Disease↗
PubMed1982

The effects of almitrine on the ventilatory response to hypoxia and hypercapnia in normal subjects.

1. Almitrine at a dose of 0.5 mg h-1 kg-1 given intravenously over 2 h had no effect on resting ventilation in normal males. 2. There was a small, but insignificant, rise in the hypercapnic drive to breathe as compared with placebo. 3. A large rise in the hypoxic drive to breathe was seen in response to almitrine. 4. These findings support the claim that almitrine has its action on ventilation via the peripheral chemoreceptors. 5. No correlation between blood levels of almitrine and the rise in hypoxic response was seen.

Adult↗
PubMed1982

Relation between tracheal size and forced expiratory volume in one second in young men.

Maximal expiratory flow-volume curves and spirometry were measured in 49 white, nonsmoking, asymptomatic men 19 to 23 yr of age and 179 to 184 cm tall. Because of the uniformity of sex, age, height, and ethnic group, conventional predicted values for these men were virtually identical. Nevertheless, the between-subject coefficient of variation in spirometric and maximal flow results varied from 10% for vital capacity (VC) and forced expiratory volume in one second (FEV1) to 29% for maximal flow when 25% of VC remained to be expired. Confirming previous results, between-subject coefficient of variation was not reduced by expressing flow as VC/s instead of L/s. Eighteen of these men had standard posteroanterior and lateral chest radiographs to measure tracheal diameters at total lung capacity. Both tracheal cross-sectional area and anteroposterior diameter were positively related to FEV1 (r = 0.73, p = 0.001), the relationship being slightly stronger than with peak expiratory flow. There was a trend for VC also to be related to tracheal dimensions. As 50% of residual between-subject variation in FEV1 in these men was accounted for by variation in tracheal size, predicted values of FEV1 in an individual subject might be usefully refined by measuring tracheal size in epidemiologic surveys, thus allowing interpretation of small deviations from mean predicted values. Further studies are required on the variation in tracheal size in a more heterogeneous population.

Adult↗
PubMed1981

Sustained release oral aminophylline in patients with airflow obstruction.

Twenty-four patients with reversible airflow obstruction under suboptimal control on conventional therapy entered a double-blind placebo-controlled trial of additional oral sustained release aminophylline. Assessment was by diary cards, twice daily PEFR, and weekly FEV1. Nineteen patients completed the trial satisfactorily. Eleven were improved subjectively by addition of aminophylline. The mean PEFR for all 19 patients rose from 232 1 min-1 SEM +/- 5, to 247 1 min-1 SEM +/- 4 (p less than 0.0001); nine individuals showed a statistically significant improvement in mean PEFR and 10 showed an improvement of greater than 200 ml in their FEV1. Improvement in PEFR on aminophylline was not at the expense of benefit from inhaled salbutamol. Unwanted effects of nausea, headache, and abdominal discomfort were recorded by 12 of the 24 patients entering the trial. Seventeen of the 19 patients completing the trial had plasma theophylline levels in the accepted therapeutic range of 10-20 mg 1(-1). The drug doses required to achieve these levels varied from 8.6-30.8 mg kg-1 24 hr-1 in the patients with no clinical or biochemical evidence of liver disease. Oral aminophylline can improve control of airflow obstruction in patients with moderately severe disease who are already receiving multiple medication, but side-effects often limit its use. The wide dose range required to achieve therapeutic plasma levels indicates that measurements of plasma theophylline are necessary for adequate interpretation of trials of theophylline compounds.

Adult↗
PubMed1981

Partial flow-volume curves to measure bronchodilator dos-response curves in normal humans.

We examined the use of partial expiratory flow-volume (PEFV) curves to obtain dose-response curves to an inhaled beta 2-adrenoceptor agonist (salbutamol) in eight normal subjects. Maximum expiratory flow at low lung volumes increased on both PEFV and full expiratory flow-volume curves, but the increase was always considerably greater on PEFV (28.4%) than on full (14.5%) curves. The percent increase in flow on the PEFV curve was not significantly influenced by the preceding volume history being 90-120 s of tidal breathing, forced expiration to residual volume, or breath holding after a full inflation. These results suggest that normal tone during tidal breathing is temporarily reduced but not abolished by a full inflation, and once basal tone has been restored it is not enhanced by a full expiration. In seven of the eight subjects a satisfactory cumulative dose-response curve to inhaled salbutamol was obtained with a plateau value of maximum flow at a dose of 110 microgram. The relatively good reproducibility of PEFV curves and the considerable bronchodilator signal obtained (29-70% increase in flow above base line in different individuals) suggest that such dose-response curves may be useful in studying normal bronchial pharmacology in vivo.

Adult↗
PubMed1981

Static transdiaphragmatic pressures in normal subjects and in patients with chronic hyperinflation.

Transdiaphragmatic pressure (Pdi) during static maximal inspiratory effort was measured in 11 normal subjects and in 4 patients with severe chronic hyperinflation (mean total lung capacity, 138% predicted). The Pdi varied widely among subjects, some production positive abdominal pressure (Pab) at all volumes and some producing Pab close to zero or negative. During modified maximal inspiratory efforts in which the abdomen was protruded, several subjects produced greater Pdi, but in none was pleural pressure (Ppl) more negative, possibly because of inhibition of diaphragmatic activation during spontaneous inspiratory efforts. In the hyperinflated patients, spontaneous maximal inspiratory inspiratory efforts produced smaller values of Pdi, but the diaphragm retained an inspiratory effect and Pdi could still be increased by abdominal protrusion during the effort. Although Pdi during such modified maneuvers probably gives a better index of the strength of the diaphragm, this may not be directly related to its effective capacity as an inspiratory muscle, which may be best assessed by comparing Pdi with Ppl during spontaneous maximal inspiratory efforts.

Abdomen↗
PubMed1980

Importance of airway closure in limiting maximal expiration in normal man.

To elucidate the importance of airway closure in limiting maximum expiration, two complementary plethysmographic techniques have been used to estimate the volume of and pressure within the trapped thoracic gas. Three young (19-23 yr) and three older (43-66 yr) subjects were studied. The first study defined the curve of possible pressure-volume relationships for the trapped gas; the second study attempted to estimate the volume of trapped gas. In the first study the subject in a Mead plethysmograph expired through a pneumotachograph and back into the box. A reduction in box volume greater than that caused by drying and cooling of expired gas implies gas compression due mainly to airway closure. In the second study a known volume of air was withdrawn from the mouth at full expiration and changes in box volume and mouth pressure were recorded. The apparent volume in pressure communication with the mouth (Vpc) was calculated using Boyle's law. In the young subjects we did not detect thoracic gas compression although there was evidence of trapped gas (RV-Vpc greater than 0). In the older subjects there was a larger volume of trapped gas that was compressed to pressures of more than 22 cmH2O. Airway closure appears to limit maximal expiration in older subjects.

Adult↗
PubMed1980

Influence of bronchomotor tone on airway dimensions and resistance in excised dog lungs.

In 10 excised dog lobes we measured total lobar resistance (Rlo) by forced oscillation at various transpulmonary pressures (Ptp) before and after bronchodilators and obtained simultaneous tantalum bronchograms in 5. Mean airway diameter increased up to a Ptp of 30 cmH2O, although the increase was greater between 0 and 10 cmH2O. In contrast, Rlo decreased between 0 and 10 cmH2O but increased again between 10 and 30 cmH2O. At a Ptp of 30 cmH2O, the mean diameter of small airways (< 2 mm) increased 31%, that of large airways (> 7 mm) 2% after aerosolized bronchodilators. At a Ptp of 1 cmH2O, increases were 44 and 15%, respectively. Values of Rlo were reduced at all Ptp after bronchodilator, but minimum Rlo occurred at lower Ptp than before, and the absolute increase in Rlo at greater Ptp was preserved. In four additional lobes, we partitioned Rlo using a retrograde catheter. All of the increase in Rlo at large Ptp was peripheral to the retrograde catheter. We conclude that excised lungs have bronchomotor tone that narrows airways even at high Ptp and that loss of tone magnifies the relative increase in Rlo at high Ptp, supporting suggestions that the increase is due to tissue resistance and hysteresis.

Airway Resistance↗