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Biomedical subjects

P Gayrard

Publications and source records attributed to P Gayrard.

At least 19 recordsLinked to original sources
PubMed1988

[Respiratory function test, a key in the etiologic diagnosis of dyspnea or a simple quantitative test?].

When confronted with a case of dyspnoea, three questions must be asked: is the dyspnoea due to a pulmonary organic disease? How severe is it? What is its nature or its origin? In the majority of cases these questions are answered by elementary lung function tests (spirometry and measurement of the residual volume), but for these answers to be valid it must be borne in mind that respiratory function test (RFT) is primarily a physical exercise: no measurement is valid unless the operator is fully involved and the subject explored participates to the best of his possibilities. RFT also is a mental exercise: the data obtained can be well understood only if the operator is conversant with the data described in this article. RFT has multiple applications, and yet this examination is notoriously underestimated and underused by the medical profession. Good practice is its best publicity.

Dyspnea↗
PubMed1987

Different bronchoconstrictor effects of carbachol boluses inhaled near residual volume or total lung capacity.

The purpose of this study was to determine if the lung volume at which aerosol inhalation begins (LVi) influences airway responses to bronchoconstrictor agents. We compared the effects of carbachol boluses (25, 50 and 100 ml), inhaled at high and low LVi (averaging 72.2 and 15.8% of vital capacity, respectively) on specific airway resistance (SRaw). In order to eliminate the possible influence of airway obstruction on aerosol distribution and deposition, we selected 5 asthmatic subjects with normal respiratory function (spirometry, SRaw, nitrogen washout and closing volume); furthermore, non-cumulative dose-response curves were obtained (i.e. the patients inhaled only one dose of carbachol on a given test day). Inhaling carbachol at low LVi yielded a significantly (p less than 0.01) larger degree of bronchoconstriction. Differences in bronchial responses were probably due to differences in the amount of particles deposited in the airways and/or to their distribution. These data suggest that LVi should be controlled for quantified inhalation provocation tests.

Adult↗
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↗
PubMed1980

[Inadequate use of pressurized aerosols by asthmatic patients [author's transl].

The purpose of this study was to determine in a population of asthmatics, the number of patients who correctly used the pressurized aerosols (bronchodilator drugs or steroids) spontaneously, or after training sessions. 115 asthmatics (in- or outpatients, 14-70 years old) were asked to use their inhaler in the presence of an observer. The inhalation technique was considered correct when (1) the puff release was coordinated with a deep inspiration and (2) when the inspiration was followed by a few seconds' breath-holding. The patients were divided into two groups: a trained group of 46 patients who were observed for 1 month or more after the two above-mentioned maneuvres had been demonstrated to them by a physician and the need for correct use strongly emphasized. The other group (the untrained group) comprised 69 patients who were presumably using their inhalers according to the manufacturer's instructions: (1) expiration; (2) inspiration and actuation, and (3) apnea. In the trained group 52% of the patients were classified by the observer as correct users, as compared to 28% in the untrained group. The results were not influenced by sex. age or occupational differences. These observations suggest that a majority of asthmatics probably derived incomplete benefit from the use of pressurized aerosols. Although training apparently results in a more efficient use of the canisters, this study shows that training sessions must be repeated, and the results checked at regular intervals by a member of the medical staff. In subjects who repeatedly fail to achieve a correct inhalation technique the drug should be given by another route.

Adolescent↗
PubMed1979

Mechanisms of the bronchoconstrictor effects of deep inspiration in asthmatic patients.

A single deep inspiration (DI) is commonly followed by transient airflow obstruction in asthmatic patients. In some patients, however, DI results in a sustained response which suggests that more than one mechanism may be responsible. We have studied the characteristics of the response to repeated DI, and their modificatiion by various pharmacological agents, by measuring specific airway resistance (sRaw) in ten subjects who showed reproducible and consistent increases in sRaw after DI. Two types of reaction were observed: type A (n = 8) had an immediate maximum and usually short persistence; type B (n = 2) had a delayed maximum with a progressive increase. In type A reactions repetition of DI showed different patterns of response--either a reproducible reaction to each DI or a plateau effect. In type B reactions the response spontaneously increased with repeated DI. Type A responses to DI were inhibited completely by a beta-adrenergic stimulant (BAS), largely by an anticholinergic drug (AC, ipratropium bromide), but in no case by disodium cromoglycate (DSCG). Type B responses were inhibited completely by BAS, largely by DSCG, and partially by AC. These findings suggest that the response to DI is due to bronchoconstriction, which in type A reactions is of reflex origin, vagally mediated, and is due in part or wholly to mediator-release in type B reactions.

Adolescent↗
PubMed1977

Bronchial response to inhaled prostaglandin F2alpha in patients with common or aspirin-sensitive asthma.

The effect of aerosolized prostaglandin F2alpha (PGF2alpha) on specific airway resistance (SRaw) has been measured in patients with common (n = 10) or aspirin-sensitive asthma (n = 5). In all subjects PGF2alpha caused a dose-related increase in SRaw, but considerable individual differences in sensitivity were observed. The patients with aspirin intolerance did not differ from regular asthmatics in terms of their response to PGF2alpha. Two types of reactions to PGF2alpha could be distinguished from their time-course: immediate and short-lasting (3 cases) or delayed and long-lasting (12 cases). Inhalation of a beta-adrenergic drug rapidly and completely reversed the effect of PGF2alpha, suggesting that the increase in SRaw was due to bronchospasm. In 7 subjects the inhalation of an anticholinergic drug (SCH 1000) prior to PGF2alpha inhibited to a large extent the effect of the latter, suggesting that the cholinergic system played an important role in the bronchial response to PGF2alpha. In 9 subjects no correlation was found between the bronchial sensitivity to carbachol and PGF2alpha.

Aerosols↗
PubMed1977

Airway response to carbachol in normal and asthmatic subjects: distinction between bronchial sensitivity and reactivity.

By constructing cumulative dose-response curves to inhaled carbachol in 12 normal and 17 asthmatic subjects with comparable baseline specific airway conductance, we have shown that there were wide variations among subjects in the dose of carbachol needed to cause a 25 per cent decrease in specific airway conductance (bronchial sensitivity) and in the slopes of the curves (bronchial reactivity). Furthermore, there was no significant correlation between these 2 characteristics of the bronchial response to carbachol. The mean dose-response curves of the asthmatic and the normal subjects were widely divergent, indicating that the asthmatic subjects differed from normal subjects more in terms of bronchial reactivity than in bronchial sensitivity. This suggests that different mechanisms determine the sensitivity and reactivity of the bronchial tree, and that hyper-reactivity is the main feature of the asthmatic response. Both should be assessed when the bronchial response to bronchoconstrictor agents is measured.

Asthma↗
PubMed1976

[Paradoxical effect of forced inspiration: a new characteristic of asthmatic disease?].

In normal subjects, forced inspiration may dilate the bronchi and be considered as a defence or compensatory reaction in certain cases. In asthma, forced inspiration has the opposite effect. Bronchospasm occurs or becomes worse, usually moderately and transiently, but sometimes to a marked and lasting degree. These reactions may be prevented by anticholinergic and sympathomimetic drugs. They should be avoided and one should thus prohibit the manoeuvres which trigger them off. One should take them into consideration during respiratory function tests. This paradoxical effect of forced inspiration seems to exist to various degrees in most asthmatic patients, it may be considered as a diagnostic sign of asthma.

Asthma↗
PubMed1976

Effect of short-term, low-level nitrogen dioxide exposure on bronchial sensitivity of asthmatic patients.

Our purpose was to determine whether exposure to a realistic concentration of nitrogen dioxide (NO2) could increase the bronchial sensitivity of asthmatic patients to bronchoconstrictor agents. We established dose-response curves for changes in specific airway resistance (SRaw) in response to aerosolized carbachol in 20 asthmatics after each had spent 1 h in an exposure chamber breathing on one occasion unpolluted air and on a separate occasion 0.1 ppm NO2: sequence of exposures to unpolluted air and to low levels of NO2 were randomized in a single-blind fashion. NO2 induced a slight but significant increase in initial SRaw and enhanced the bronchoconstrictor effect of carbachol in 13 subjects: curves were shifted to the left and the mean dose of carbachol producing a twofold increase in initial SRaw was decreased from 0.66 mg to 0.36 mg (P less than 0.001). In contrast, NO2 neither modified the initial SRaw nor the bronchoconstrictor effect of carbachol in seven subjects. In 4 out of the 20 subjects, exposure to a higher concentration of NO2 (0.2 ppm) yielded variable results. Potentiation of the carbachol bronchoconstrictor response by NO2 could not be related to any physical or clinical characteristics of the subjects tested. Although the mechanisms underlying the NO2 effect remain controversial, the present results demonstrate that very low levels of NO2 can adversely affect some asthmatics.

Adolescent↗
PubMed1976

[Bronchomotor tonus: per-operative bronchospasm].

The comprehension of the occurrence of bronchospasm during surgery is based on the knowledge of the factors which control bronchomotility: parasympathetic or cholinergic system, essentially bronchoconstrictor; sympathetic adrenergic system, with beta-2 effect, bronchodilator, and with alpha-bronchoconstrictor effect. It is also worth bearing in mind the chemical midiators, in particular, histamine contained in the mast cells, "slow reacting substance of anaphylaxis" which is a bronchoconstrictor substance of slow and prolonged action, Serotonin whose role is more modest. The last mediators known, prostaglandins, play an important role in the regulation of bronchomotility, PGE' are bronchodilators, PGF 2 alpha are bronchoconstrictors. With reference to the development of bronchospasm during anesthesia, one must bear in mind the background, and in particular of the allergy, of a past history of asthma and of the pre-operative functional respiratory condition. One must also bear in mind the anaesthesia, and the pharmacodynamic action of the substances used which can interfere with the phenomena controlling bronchomotor tone.

Adrenergic Fibers↗
PubMed1975

[Exercise test in the asthmatic patient. Study of 75 patients].

Frequency of exercise-induced asthma has been studied in 75 unselected asthmatic patients (adults and children) by measuring the forced expiratory volume at one second (FEV1) and the vital capacity (VC) before and after a treadmill exercise, continued until heart rate was at least equal to 80 p.cent-85 p.cent of maximum heart rate. In 19 subjects (25 p.cent), a more than 20 p.cent decrease from control value of FEV1 was recorded ten minutes after exercise ended. Exercise-induced bronchial obstruction was relieved by a beta adrenergic bronchodilator aerosol inhalation. In the group of 19 subjects having exercise-induced asthma, a significant positive correlation was found between pre-exercise FEV1 values and post-exercise FEV1 decreases. In the whole group of 75 subjects exercise-induced asthma was related to the severity of asthma and not to other clinical or physical characteristics of the subjects. From the data of other authors it appears that frequency of exercise-induced asthma is variable. The reasons of those differences are discussed.

Adolescent↗