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Biomedical subjects

V Brusasco

Publications and source records attributed to V Brusasco.

107 records · Page 6Linked to original sources
PubMed1986

Adenosine-induced bronchoconstriction: premedication with chlorpheniramine and nedocromil sodium.

The mechanism for adenosine-induced bronchospasm was investigated in asthmatic patients. Nedocromil sodium 4 mg given by aerosol 10 min before challenge effectively inhibited adenosine-induced bronchospasm. The H1-antagonist chlorpheniramine 4 mg given orally 1 h before challenge did not inhibit adenosine-induced bronchospasm, suggesting either that histaminergic pathways are not involved or that the dose was not sufficient to elicit an effect in the lung. Nedocromil sodium did not reduce the bronchial response to methacholine, supporting the view that adenosine-induced bronchospasm is not mediated through cholinergic pathways. The mechanism(s) by which nedocromil sodium inhibits the bronchial response requires further investigation.

Adenosine↗
PubMed1986

Dual asthmatic reactions to inhaled Dermatophagoides pteronyssinus: reproducibility and antagonism by cromolyn sodium.

Twenty-four asthmatic patients sensitized to Dermatophagoides pteronyssinus were challenged with a standardized extract of this allergen. All the patients selected on the basis of skin tests and RAST, had an early asthmatic reaction (EAR). Seventeen of them also had a late asthmatic reaction (LAR). Eleven patients were rechallenged in order to study the reproducibility of both EAR and LAR. Six patients were also challenged after cromolyn sodium premedication Results show that (1) reproducibility of both EAR and LAR is satisfactory (coefficient of variation = 14%), (2) patients with reproducible EAR also have reproducible LAR, and (3) a single dose of cromolyn given before challenge can prevent EAR and markedly attenuate LAR.

Adolescent↗
PubMed1985

Bronchial provocation tests with RAST-standardized allergens and dosimetric technique.

58 patients with proven allergic asthma (positive prick and RAST) were challenged with allergen extracts dosed in RAST arbitrary units; 14 of them were rechallenged after some months to evaluate the reproducibility of results; 41 underwent also a nonspecific challenge with methacholine. The results of the specific bronchial provocation test were well reproducible, with similar coefficients of variation for both early and late reactions. The specific bronchial provocation test was found to be more related to the allergic status, as reflected by specific IgE levels, than to nonspecific bronchial hyperreactivity, as reflected by response to methacholine.

Adolescent↗
PubMed1984

Effects of beta-adrenoceptor blockade on exercise performance and respiratory response in healthy, physically untrained humans.

The effects of propranolol 80 mg orally were compared with those of placebo on the response to a stepwise increasing exercise test in 17 healthy and physically untrained volunteers, of whom eight were female. Propranolol showed no significant effects on maximum work rate or perceived exertion rate. However, submaximal O2 uptake, CO2 output and minute ventilation tended to be lower after propranolol than after placebo. It is concluded that in subjects with a low work capacity, beta-adrenoceptor blockade does not impair maximal exercise capacity. The mechanisms underlying changes in respiratory response to exercise after propranolol are not fully explained. However, changes in substrate utilisation, the reduction in cardiac output and an alteration in respiratory drive may all be involved.

Adrenergic beta-Antagonists↗
PubMed1984

Ventilation-perfusion relationship during high-frequency ventilation.

The efficiency of oxygenation and the uniformity of the distribution of regional ventilation (Vr) to regional perfusion (Qr) along the vertical and horizontal axes was compared in anesthetized dogs between conventional mechanical ventilation (CMV) and high-frequency ventilation (HFV) at 5.8, 15.0, and 29.8 Hz. Both CMV and HFV were adjusted to result in similar arterial CO2 tensions. The distribution of Vr/Qr during HFV at 5.8 Hz tended to be more uniform than during HFV at 15.0 or 29.8 Hz or during CMV. Consistent with this observation, arterial O2 tension (PaO2) tended to be higher during HFV at 5.8 Hz (means +/- SD, 90 +/- 9 Torr) than during HFV at 15.0 Hz (83 +/- 9 Torr) or 29.8 Hz (78 +/- 10 Torr); PaO2 was significantly higher during HFV at 5.8 Hz than during CMV (83 +/- 7 Torr).

Animals↗
PubMed1983

Gas transport during high-frequency ventilation.

During high-frequency small-volume ventilation (HFV), the transport rate of gas from the mouth to a lung region is a function of two conductances (conductance is the transfer rate of a gas divided by its partial pressure difference): regional longitudinal gas conductance along the airways (Grlongi) and gas conductance between lung regions (Ginter). Grlongi per unit regional lung (gas) volume [Grlongi/(Vr beta g)] was determined during HFV in 11 anesthetized paralyzed dogs lying supine. The distribution of Grlongi/(Vr beta g) was nearly uniform during HFV when stroke volumes were less than approximately two-thirds of the Fowler dead-space volume. By contrast, the distribution of Grlongi/(Vr beta g) was nonuniform when the stroke volume exceeded approximately two-thirds of the Fowler dead-space volume and the oscillation frequency was 5 Hz. Gas conductance along the airways per unit lung gas volume [average Glongi/(V beta g)], for the entire lung, increased with stroke volume at all frequencies, but for a given product of oscillation frequency and stroke volume, the average Glongi/(V beta g) was greater when stroke volume was large and oscillation frequency was low. The average Glongi/(V beta g) increased with frequency up to a maximal value; the frequency at which the maximum occurred depended on the kinematic viscosity of the inspired gas mixture.

Animals↗
PubMed1981

Effects of volume history and time dependence of flow-volume curves on assessment of bronchial response to inhaled methacholine in normals.

The behavior of maximum expiratory flow-volume curves and partial expiratory flow-volume curves with and without volume history of total lung capacity was studied in 11 healthy subjects before and after methacholine inhalation challenge. Flow-volume curves were superimposed at absolute lung volumes by measuring thoracic gas volumes at which inspiratory maneuvers began. The results show that maximum inspiratory effort reduced significantly residual volume, either before or after challenge, while flow rates at 40% of control total lung capacity achieved with partial expiratory flow-volume curves with history of total lung capacity were significantly greater than those without history of maximal inflation. These findings are explained by the stress relaxation as an effect of volume history ot total lung capacity and by the appearance of time dependence as an index of inhomogeneity of lung emptying. After methacholine the effects of volume history on maximum flows and residual volume were increased. In conclusion, the results of this study emphasize the probability of errors when only maximum expiratory flow-volume curve are used in assessment of bronchial responses.

Adult↗
PubMed1981

Inspiratory flow and intrapulmonary gas distribution.

The effect of flow of inspired gas on intrapulmonary gas distribution was examined by analysis of regional pulmonary 133Xe clearances and of total pulmonary 133Xe clearance measured at the mouth after equilibration of the lungs with 133Xe. Five awake healthy volunteers (24 to 40 yr of age) and another 5 healthy, anesthetized-paralyzed volunteers (26 to 28 yr of age) were studied while they were in the right lateral decubitus position. The awake subjects were studied at 3 inspiratory flows (0.4, 0.7, and 1.0 L/s) and the anesthetized-paralyzed subjects at 4 inspiratory flows (0.2, 0.5, 1.1, and 1.6 L/s). Interregional differences in 133Xe clearances along the vertical axis were significantly less during anesthesia-paralysis and mechanical ventilation than during spontaneous breathing in the awake state. No differences in the regional or total pulmonary 133Xe clearances were detected at these different flows in either of the two states, i.e., the difference between the awake and anesthetized-paralyzed states persisted.

Adult↗
PubMed1980

Identification and parameter estimation of the mechanical ventilatory system.

Oesophageal pressure and mouth volume were measured by oesophageal balloon and pneumotachography, respectively, in 10 men (both normal and diseases) under different experimental conditions, i.e. spontaneous ventilation, quasi-static manoeuvres and respiration at high frequencies. The recorded data were then analyzed by an identification and parameter estimation computer programme, to determine a mathematical model for the process. Contrary to other recently published papers dealing with frequency analysis, we studied a time-dependent model, represented by a linear time-invariant differential equation. The results were quite satisfactory since a relatively second-order model seems to be adequate for describing the process. Differences in the parameter values between normal and diseased subjects were characterized by increases in the patients' lung viscous component. In conclusion, our identification test results in the mechanical ventilatory system seem to indicate that a simple second-order mathematical model is consistent with the experimental data.

Adult↗
PubMed1980

Analysis of nitrogen multibreath washout curves through a statistical approach.

A new method for analyzing nitrogen multibreath washout curves, founded on a statistical multicompartment model is presented. This method consists of two phases: (i) the preliminary conversion by mathematical means of the nitrogen end-tidal concentration curves - as usually available in routine practice - into the corresponding lung nitrogen decay curves normalized for ventilation rate and function al residual capacity and (ii) the determination of distribution function G(k) in the Laplace integral y(t) = integral of infinity,G(k)e-ktdk (where y(t) represents the experimental curve, k is the compartmental rate constant and the random variable of the statistical set). G(k) values are approximated by an accurate calculation of the distribution moments and the use of Edgeworth-Cramér series expansion. The clinical usefulness of the method was verified in normal subjects and in patients with chronic obstructive pulmonary disease. An excellent separation of the two groups was achieved by calculating the following parameters: the first moment (m1), the standard deviation (sigma) and the coefficient of dispersion (sigma/m). Besides, further information about the lung ventilation pattern could be obtained by a skillful inspection of the approximated distribution function curves of the rate constant k.

Adult↗
PubMed1980

Comparison between intracutaneous and prick tests in detecting sensitizations to common Mediterranean allergens.

The role of the intracutaneous test (IC) in clinical allergy routine was evaluated comparing its results with those from the prick test, the radioallergosorbent test (RAST), and the specific bronchial provocation test (BPT). The study was carried out making an a posteriori survey of 384 patients suffering from symptoms of perennial and seasonal rhinitis and/or bronchial asthma. They were tested with the most common allergens in the Mediterranean countries; 681 prick tests and 489 IC tests were compared with RAST and 69 with BPT. The IC tests showed disagreement with RAST and BPT more frequently than prick tests: this is attributable to a lesser degree of specificity of IC test performed with the usual concentrations, and depends on the nature of the allergens. On the other hand the prick test is no less sensitive than the IC test, being the occurrence of RAST positivity in patients with negative skin tests similar for the prick and IC tests. These results support the concept of the prick test as preferable with respect to the IC test because of its specificity and sensitivity.

Adolescent↗
PubMed1980

A clinical trial of oral clenbuterol (NAB 365) in chronic airways obstruction.

A new oral bronchodilator, clenbuterol, was compared with terbutaline during a 5-week single-blind crossover study in 16 patients with chronic airways obstruction and with cough and sputum production. After a run-in period (1 week), the study was performed in two separated 2-week periods (Phase II and Phase IV), separated by a 1-week drug-free period. Oral clenbuterol was administered at 20 to 30 micrograms 3-times daily, oral terbutaline at 2.5 to 5 mg 3-times daily. The forced expiratory volume in 1 second (FEV1) was measured at the beginning and end of Phase II and Phase IV under baseline conditions, and 1 hour after an oral dose of clenbuterol or terbutaline. Parents recorded subjective and objective information in a daily diary and used no bronchidilator therapy for 12 hours before each visit. Clenbuterol and terbutaline significantly improved baseline FEV1 and the bronchodilator effects of single oral doses were similar. The mean dyspnoea, cough and sputum score values after treatments were lower than during the wash-out period (p less than 0.05). Tremors were noted in 6 patients on clenbuterol and 5 on terbutaline. It is suggested that clenbuterol is a good alternative oral drug for treatment of chronic airways obstruction.

Administration, Oral↗
PubMed1978

Dose-response study of a new oral bronchodilator, NAB 365 (clenbuterol).

A new oral bronchodilator, NAB 365 (clenbuterol), at doses of 10, 20, 30 and 40 microgram, was studied in a double-blind placebo-controlled incomplete cross-over study in 10 patients suffering from chronic bronchitis who had reversible airway obstruction. The ventilatory response was assessed by measurement of the forced expiratory volume in 1 sec (FEV1), total airway resistance (Raw) and specific airway conductance (sGaw) before and 30, 60, 120, 180, 240, 360 and 480 min after administration. With the 30 and 40 microgram doses, a significant bronchodilating effect was seen between 30 and 360 min after administration, with peak effects between 120 and 240 min. The maximal effects in ventilatory response after 30 microg were only slightly less than after 40 microgram; the bronchodilating effect of 20 microgram was statistically less marked than those of 30 of 30 and 40 microgram on FEV1, but not statistically different on Raw and sGaw. These findings have been briefly discussed. The effects of 10 microgram and of the placebo were always statistically lower than those of 20 microgram. No significant cardiovascular effects and no subjective side effects were observed. In conclusion, the results suggest that 30 microgram of NAB 365 (clenbuterol) are the suitable acute dose.

Adult↗
PubMed1975

[Modifications in the closing volume due to the inhalation of tobacco smoke].

Two methods, the one making use of nitrogen and the other of body plethysmography were applied to a group of normal young subjects in order to value the effects of the inhalation of tobacco smoke on the "closing volume". The results obtained with the two methods are different; according to authors, this phenomenon may be explained on the base of the physiopathologic meanings of the closing volume, under the condition to admit that tobacco smoke may promote an early closure and before all disorders in the distribution of the residual volume.

Humans↗
PubMedDate not supplied

The effect of inhaled furosemide and acetazolamide on bronchoconstriction induced by deep inspiration in asthma.

In some asthmatics deep inspiration causes a sustained bronchoconstration, which is dependent on Ca2+ uptake. Inhaled diuretics protect against bronchoconstriction induced by a variety of indirect stimuli, by inhibiting the ionic fluxes involving Ca2+ uptake across the cell membrane of airway epithelium. The aim of this study was therefore to investigate the protective effect of inhaled furosemide on the bronchoconstriction induced by deep inspiration in asthma and to compare it with the effect of acetazolamide, an inhibitor of carbonic anhydrase devoid of effect on ion cotransport but possessing inhibitory effects on chloride ion influx and Na+/K+ exchange. The study was carried out on three different study days according to a randomized, double-blind, placebo-controlled, crossover design. Nine non smoking asthmatic subjects first performed a series of 9 controlled deep inspirations to TLC followed by forced expirations to RV within 20 min, which caused a decrease of FEV1 > 20% from baseline. Two hours later, the subjects inhaled either furosemide (40 mg), or acetazolamide (500 mg), or saline (placebo) in random order, and then two more deep-inspiration challenges were performed after 30 and 140 mins. The progressive percent decrement of FEV1 caused by deep-inspiration challenge was taken as an index of bronchoconstriction. Bronchoconstriction was significantly blunted at 30 mins, but not 140 mins, after inhaling furosemide (p < 0.01) or acetazolamide (p < 0.05) compared to control. We interpret these results as due to a modulation of ionic fluxes across the smooth muscle cell membrane afforded by inhaled furosemide and acetazolamide.

Acetazolamide↗