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Biomedical subjects

C Grimaud

Publications and source records attributed to C Grimaud.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1977

Interaction between vagal and chemoreceptors afferents in ventilatory response to transient hypercapnia (anaesthetized rabbit).

In rabbits anaesthetized with ethyl-carbamate, stimulation of chemoreceptors afferents was allowed by transient hypercapnia, before and after vagal blockade by DC current. In these relatively fast breathing animals, the transient hypercapnia produced light changes of inspiratory tidal volume (VI), inspiratory (TI) and expiratory durations (TE). Despite the identity of transient hypercapnia, it ensued that: (1) the higher the spontaneous VI and the lower the respiratory frequency (fR), the greater their respective changes (deltaVI and deltafR) during the ventilatory response; (2) after vagal blockade, greater changes in VI, TI, TE and mean inspiratory flow rate (VI/TI) occurred than in control state, while the relation between deltafR and fR was more significant than in control state. Respective roles played by vagal and chemoreceptors afferents in the ventilatory response to transient hypercapnia are discussed.

Animals↗
PubMed1977

A new simple spirometric index for use with bronchial provocation tests.

Spirometric indices such as the forced expiratory volume in one second (FEV1), the maximal expiratory flow rate (MEFR) and the maximal midexpiratory flow rate (MMFR) can be criticized for use with bronchial provocation tests since they are either partly effort-dependent or dependent on the forced vital capacity (FVC). These criticisms can be avoided by the use of a new index corresponding to the volume of air expired in one second starting at 75% of the control FVC, called the (FEV1)-25. This study was performed to evaluate the relative sensitivity of the (FEV1)-25 and the classical FEV1 in detecting airway obstruction caused by an inhaled carbachol aerosol in 20 asthmatic subjects. The mean fall in (FEV1)-25 of 46% following carbachol inhalation compared with a mean fall in FEV1 of 35% indicates that, in addition to its theoretical advantages, the (FEV1)-25 is a sensitive index for use with bronchial provocation tests.

Adolescent↗
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

Relationships between eupnoeic pattern of breathing and ventilatory control in man: I. Response to airways occlusion during active lung inflation.

The apnoeic response following interruption of the air flow at different levels of the inspiratory capacity (deltaVL) was studied in conscious children and adults. Changes in mouth pressure were used to measured the duration of the apnoe. The total duration of the interrupted breath (T1) was compared to mean value of the ventilatory period of the five preceding breaths (T0). A monoexponential regression could be fitted to the relationship between T1/T0 ratio and change in lung volume (deltaVL) measured at the onset of interruption: T1/T0=k-exp (S-deltaVL), S begin the sensitivity of the response to lung inflation. When T1/T0=1, the intrathoracic lung volume was called threshold volume (VTh.L.). The parameters S and VTh.L. were used for characterization of the individual importance of the Breuer-Hering inspiratory-inhibitory reflex (B.H. reflex). The high reproducibility of the T1/T0 vs. deltaVL relationship in many subjects showed the light influence of voluntary control on apnoea's duration. In each subject, S and VTh.L. were compared with ventilatory variables measured during eupnoea. A fast pattern of breathing (i.e. small inspired volume and short inspiratory duration) was associated with high value of S and low VTh.L. Moreover VTh.L. was near the tidal volume range in subjects where the B.H. reflex was the more potent. Thus, vagal afferents relating to this reflex could modulate the eupnoeic pattern of some subjects.

Adolescent↗
PubMed1976

Relationships between eupnoeic pattern of breathing and ventilatory control in man II. Early response to transient hypercapnia.

The individual importance of peripheral chemosensitive afferents was studied using a transient hypercapnia (inhalation of a 5% or a 10% CO2 in air gas mixture respectively during 4 or 2 breaths) in human conscious subjects chosen for their different eupnoeic ventilatory patterns. Calculation of the speed of change in end-tidal CO2 pressure in tracheal gas (sPETCO2) and of the rate of change in tidal volume (sVI) gave assessment for quantifying the sensitivity of arterial chemoreceptors to hypercapnia (sCO2=SVI/SPETCO2). Our results showed that, independently of any outside influence of the eupnoeic ventilatory pattern on the components of the chemical stimulus, sVI and sCO2 were found to be much smaller in subjects whose pattern of breathing was slow (i.e. having a large tidal volume). The possible causes of the weak importance of peripheral chemosensitive afferents in such subjects were discussed.

Adolescent↗
PubMed1976

[Relationship between the control of the duration of inspiration and the resting ventilation pattern in conscious man].

The relationship between tidal volume (V1) and inspiratory duration (T1) was studied in 5 subjects by a rebreathing procedure in pure O2. The range of this relationship marked by a decrease of T1 with increasing V1, related by Clark and Von Euler to the inhibitory vagal feed-back loop Breuer Hering or B.H. reflex, was only found in 3 subjects possessing the B.H. reflex. In the others, whose pattern of breathing was very slow, nor this range nor the B.H. reflex were found. These findings confirm previous owner data (2). Indeed in our subjects having a slow pattern of breathing, the control of T1 seems to be unrelated to vagal afferences coming from lung stretch receptors.

Adult↗
PubMed1976

[A new method for rapid determination of blood L-lactate using an enzymatic lactate sensor (author's transl)].

We determined the lactate concentration in 112 samples of arterial blood, simultaneously by two-different technic: 1) The usual enzymatic technic (plasmatic and intracellular lactates). 2) A new technic using an enzymatic lactate sensor ("lactate analyzer 5400") which measures the plasmatic lactates only. The data obtained with the two technics were very similar (r = 0,982). The small volume of blood used and the handiness and rapidity of the new procedure are to be noted.

Autoanalysis↗
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↗
PubMed1975

Effect of maximal respiratory manoeuvres on bronchial sensitivity of asthmatic patients as compared to normal people.

Cumulative dose-response curves to carbachol given by aerosol were established using plethysmographic measurements of specific airways resistance (SRaw) in 10 patients with asthma and five healthy subjects. Two experiments were performed--a control test and one in which maximal respiratory manoeuvres (MRM) (two maximal inspirations and two maximal expirations) were made before each carbachol inhalation. MRM did not modify the dose-response curves in the normal subjects. In the patients these manoeuvres enhanced the bronchoconstrictor effect of carbachol: curves were shifted to the left and the mean dose of carbachol producing a twofold increase in initial SRaw was decreased from 0.373 mg to 0.189 mg (P less than 0.001). Bronchial provocation tests using methods which require MRM--for example, forced expiratory volume at one second--could overestimate the bronchial sensitivity of patients with asthma.

Adolescent↗
PubMed1975

Effect of beta adrenergic blockage on bronchial sensitivity to inhaled acetylcholine in normal subjects.

Dose-responses curves were established in 10 normal subjects by measuring, with a body plethysmograph, the changes of specific airway conductance (SGaw) produced by aerosolized acetylcholine. Doses of acetylcholine producing a 50 per cent decrease of control SGaw (ED50) were found to be largely variable among individuals. Beta-adrenergic blockade with intravenous propranolol (0.2 mg per kilogram) resulted in a mean potentiation of the acetycholine effect (mean ED50 after propranolol was significantly lower than mean ED50 before). This potentiating effect of propranolol, however, was also subjected to individual variations, suggesting individual variability of the sympathetic system. The range of variation in acetylcholine sensitivity was not narrowed by propranolol treatment and no correlation was found between initial acetylcholine sensitivity and propranolol potentiation. This suggests that variability of the sympathetic system is not the main factor in determining individual variation in acetylcholine sensitivity. Even when propranolol was very effective in increasing airway sensitivity, this sensitivity was still less marked than usually encountered in asthmatic patients. This suggests that beta-adrenergic blockade cannot create, if alone, the bronchial hypersensitivity characteristic of asthma.

Acetylcholine↗
PubMed1975

Beta-adrenergic function in airways of healthy and asthmatic subjects.

We measured the short-term effects of beta-adrenergic blockade with propranolol (0.2 mg/kg iv), followed by stimulation with salbutamol (200 mug inhaled), on specific airway conductance (SGaw) heart rate, and systemic blood pressure (BP) in 11 healthy subjects, and 11 symptom-free asthmatics with normal lung function values. Propranolol induced a significant bronchoconstrictor effect in both groups, stronger in asthmatics than in normals: mean SGaw decreased 34.6 +/- 25% against 9.4 +/- 9% (p less than 0.01). Six of the 11 asthmatics exhibited a more pronounced bronchoconstriction than the most responsive healthy subject. Large individual variations were seen in both groups although they were greater in the asthmatics. A similar rise in SGaw was produced by salbutamol in both groups. The decrease of heart rate provoked by propranolol was similar in the two groups, averaging 18.6%, with no further change after salbutamol. The blood pressure was slightly decreased by propranolol in both groups. The results indicate that normal subjects have a weak and variable bronchodilator beta-adrenergic activity. In most asthmatics beta-adrenergic tone appeared more pronounced. The individual differences in response to propranolol observed in both groups suggest that asthmatic patients differ quantitatively rather than qualitatively from healthy subjects with respect to beta-adrenergic receptor function. There was no association between clinical findings and the degree of bronchomotor effect of propranolol in the patients with asthma. This study does not support the view that airways of asthmatic patients have a decreased beta-adrengeric receptor function.

Adult↗