Search PubMed⌕ Search

Biomedical subjects

J Orehek

Publications and source records attributed to J Orehek.

At least 37 records · Page 2Linked to original sources
PubMed1987

Asthma without airway hyperresponsiveness to carbachol.

Generally, asthma is closely associated with hyperresponsiveness to bronchoconstrictor agents. However, we have observed three patients who initially had symptoms of asthma but no hyperresponsiveness. Responsiveness to carbachol was assessed by specific airway resistance (SRaw) measurement after bronchodilatators had been discontinued. The carbachol challenge was repeated 6-18 months later. Initially, no change in SRaw was observed after inhalation of 3 mg carbachol (cumulated dose). On the second occasion, carbachol responsiveness increased into the asthmatic range while the baseline values of SRaw were not different. Since we have used the SRaw measurement, the bronchodilatator effect of maximal inspiration is not the explanation for the failure to demonstrate hyperresponsiveness. These observations suggest that airway hyperresponsiveness is not a necessary condition for induction of asthma and symptoms of asthma may precede the appearance of airway hyperresponsiveness.

Adolescent↗
PubMed1984

Spontaneous and provoked resistance to isoproterenol in isolated human bronchi.

Cumulative concentration-response curves to isoproterenol were constructed in 74 preparations of human airways (group A) contracted with acetylcholine (80% of maximal contraction). In 52 bronchi (group A1), the maximal relaxation to isoproterenol represented at least 70% of the acetylcholine contraction (average 98% +/- 3) and the mean concentration (+/- SD) causing 50% of the relaxation (EC50) was 6.0 X 10(-8)M +/- 0.8. Resistance to isoproterenol (significant decrease of the maximal relaxation and right shift of the concentration-response curve) was provoked in 25 preparations by incubating them with isoproterenol (concentration 100 times higher than the individual EC50) for 30 min. The response to isoproterenol remained stable over the same time interval in eight control preparations. Incubation with isoproterenol did not modify the relaxing response to theophylline (n = 8). Indomethacin had no effect on the resistance provoked by isoproterenol incubation (n = 11). Incomplete relaxation to isoproterenol (maximal relaxation averaging 47% +/- 2 of the acetylcholine contraction) was observed in 22 preparations (group A2; mean EC50 = 1 X 10(-6)M +/- 0.2, significantly different [p less than 0.001] from group A1). Such preparations could be completely relaxed by theophylline (n = 7). For the whole group A, a significant negative correlation was found between isoproterenol EC50 and the magnitude of the maximal relaxation to isoproterenol (expressed as percent of acetylcholine contraction). There was no significant correlation between acetylcholine EC50 and isoproterenol maximum relaxation. Spontaneous resistance to isoproterenol was neither related to the technique of isoproterenol administration (cumulative versus noncumulative; n = 11) nor the magnitude of acetylcholine contraction (70% and 95% of maximal contraction; 14 bronchi, group B).

Airway Resistance↗
PubMed1984

Seasonal increase of carbachol airway responsiveness in patients allergic to grass pollen. Reversal by corticosteroids.

By measuring airway resistance (Raw) as an index of response, dose-response curves to aerosolized carbachol were constructed in 10 patients suffering from grass pollen allergy. The subjects were first tested before the pollen season (March). During the pollen season (May and June), another control test was performed; the patients were then treated (double blind and at random) with placebo or methylprednisolone (16 mg/day given orally) for 7 days and then retested. After a 10-day interval devoid of treatment, the 2 treatments were crossed over and a fourth carbachol test was performed. Baseline function values were comparable for all 4 tests. In all but one subject (who was a smoker), carbachol increased Raw by more than 150% over baseline for each of the 4 tests. In these 9 patients, carbachol responsiveness significantly increased during the pollen season and returned to its preseason level after corticosteroid treatment. The data suggest that airway inflammation was responsible for the seasonal increase in airway reactivity.

Adolescent↗
PubMed1984

[Measurement of the effect of a bronchodilator using FEV1: how to express it?].

An assessment of the effect of a bronchodilator on VEMS (FEV1) is based on a "before and after" comparison with the chosen drug. Most often the percentage rise in FEV1 compared to the initial value is calculated (I), and a minimum of 20% reversibility is expected for asthma. But the change of FEV1 expressed as a percentage of predicted theoretical value (II) may also be calculated. With the help of 50 cases of asthma selected by the first criteria (I) after an inhalation of an adrenergic stimulant the following changes were shown: That the first method (I) is biased, over estimating for low initial values; That the second method (II) was not inconvenient and furnished all the information derived. It shows in particular that 14/50 subjects have a variation of FEV1 less than 10% of their theoretical value, which has considerable therapeutic interest and merits further discussion.

Adult↗
PubMed1983

The concept of airway "sensitivity" and "reactivity".

Linear dose-response relationships can be obtained in vivo by measuring changes in airway conductance induced by graded doses of aerosolized bronchoconstrictor agents. Bronchial Sensitivity is defined as the dose causing the threshold response whereas Reactivity is the rate of response (slope of dose-response line). Determinants of bronchial response are complex and factors other than airway smooth muscle may play an important role (e.g. mucosal thickness). Examples are given of situations in which the concept of Reactivity and Sensitivity may be useful. Differences between in vitro and in vivo dose-response relationships are discussed.

Airway Resistance↗
PubMed1983

Deep-inspiration induced bronchoconstriction: a mechanism for beclomethasone aerosol intolerance.

We studied 17 asthmatic patients complaining of coughing attacks, with or without asthma, when inhaling beclomethasone dipropionate aerosol (Becotide). Specific airway resistance (SRaw) was measured immediately after a maximal inspiration (MI) and after Becotide inhalation. The effect of a second inhalation of Becotide was measured 10 min after inhalation of salbutamol. MI and Becotide induced large, but transient, SRaw increases in all patients; in addition, the latter induced coughing reactions. After salbutamol pretreatment, Becotide inhalation did not increase SRaw but coughing usually persisted. In 6 patients only, the increase in SRaw after Becotide was larger than that observed after MI. In those patients, placebo and Aldecine (similar to Becotide except for the metering valve) aerosols induced SRaw increases similar to that observed after Becotide. These data suggest that Becotide-induced bronchoconstriction is mainly related to the deep breath required for the inhalation. Non-specific irritation of the airways was probably responsible for the additional bronchoconstriction noticed in some patients.

Aerosols↗
PubMed1983

Airway response of asthmatics to carbachol and to deep inspiration.

Dose-response curves were established in asthmatics by using graded doses of aerosolized carbachol and specific airway conductance (SGaw) measurements. After carbachol inhalation, we evaluated the influence on SGaw of a deep inspiration to total lung capacity followed by a passive expiration to functional residual capacity. When SGaw had returned to its pre-deep-inspiration value, forced expiratory volume in one second (FEV1) was obtained. Two groups of patients were selected according to the effect of deep inspiration on SGaw: group A (22 patients) with a less than 25% SGaw increase after deep inspiration, and group B (21 patients) with a more than 75% SGaw increase. Both groups were comparable in age and initial SGaw and FEV1 values. Carbachol inhalation induced a similar SGaw decrease in both groups, whereas FEV1 decreased more (p less than 0.05) in group A than in group B. The two groups did not differ significantly regarding the dose of carbachol causing a 25% SGaw decrease and in the slope of the dose-response curve. We conclude that, in asthmatic patients, airway response to an inhaled broncho-constrictor agent is not related to the airway response to deep inspiration. This suggests that previous studies of airway response to bronchoconstrictor agents which have been performed by using only FEV1 measurements, may need to be reassessed.

Adult↗
PubMed1982

Factors influencing the bronchodilator effect of a deep inspiration in asthmatic patients with provoked bronchoconstriction.

We have studied 26 asthmatic patients in whom deep inspiration induced a transient but marked bronchodilatation when carbachol-induced bronchoconstriction was present. Changes in bronchial tone were assessed by specific airway resistance measurements. Bronchodilatation after a slow inspiration (eight subjects) or a 10-second breath-hold at total lung capacity (13 subjects) was significantly less than that observed after either a fast inspiration or no breath-holding period. The magnitude of the bronchodilatation induced by a fast inspiration without breath-holding was directly and significantly related to the magnitude of the carbachol-induced bronchoconstriction in five subjects.

Adult↗
PubMed1981

Influence of the previous deep inspiration on the spirometric measurement of provoked bronchoconstriction in asthma.

The measurement of the forced expiratory volume in one second (FEV1) after a maximal inspiration is often used to assess the effect of inhaled bronchoconstrictor agents. In persons with asthma, a deep inspiration transiently alters the bronchial tone in a variable way. This may result in a variable decrease of FEV1 despite a similar degree of pharmacologically induced bronchospasm. In 71 patients with asthma we induced a comparable increase (approximating 200%) in airway resistance (Raw) with aerosolized carbachol. We then measured the change in Raw induced by one deep inspiration; when Raw had returned to the value observed before deep inspiration, the FEV1 was measured. A significant correlation (r = 0.74; p less than 0.001) was found between the transient changes in Raw induced by a deep inspiration (ranging individually from a 33% increase to a 70% decrease) and the decrease in FEV1 (from 0 to 70%). The decrease in FEV1 was greatest in patients in whom a deep inspiration increased Raw and least in those in whom Raw decreased. The initial and post-carbachol Raw values of the 17 patients exhibiting a less than 20% decrease in FEV1 were similar to those of the 54 patients with a decrease in FEV1 of more than 20%. Because a prior deep inspiration prevents changes in FEV1 in some patients with asthma, the use of the FEV1 for bronchial provocation tests can be misleading.

Asthma↗