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Biomedical subjects

L Brasseur

Publications and source records attributed to L Brasseur.

At least 73 records · Page 4Linked to original sources
PubMed1979

Frequency dependence of respiratory resistance in healthy children.

We measured in 130 (61 girls) children aged 3--14 yr respiratory resistance (Rrs), with the oscillation technique, between 4 and 9 Hz. Rrs, at both 4 and 9 Hz, decreased as a function of height (r = 0.74, P less than 0.001). No statistical difference was found between boys and girls. Frequency dependence of resistance (Rrs 4 Hz-Rrs 9 Hz) was found in children at all ages, and decreased with increasing height (r = 0.50, P less than 0.001). We suggest that frequency dependence of resistance in children can be explained on the basis of an increased peripheral resistance, which produces an asynchronous distribution of tidal volume between dead space and lung parenchyma. During growth peripheral resistance decreases and Rrs bcome less frequency dependent to reach at about 15--16 yr independency of frequence.

Adult↗
PubMed1979

Constancy of effort and variability of maximal expiratory flow rates.

In 14 normal subjects and in 13 patients with obstructive pulmonary diseases, we studied the variability within an individual of values for the maximal expiratory flow rate (Vmax) recorded simultaneously vs expired pulmonary volume (at the mouth) and vs thoracic volume (measured with a body plethysmograph). We found that the variance of Vmax within an individual at 25, 50, and 75 percent of the expired vital capacity did not differ statistically whether pulmonary volume was the expired or the thoracic gas volume. In ten healthy subjects on two occasions (at an interval of 12 days, on the average), we measured the peak expiratory flow rate and Vmax at different levels of inflation, with respect to either expired or thoracic volume. There was no statistical differences in Vmax between the first and the last day. A larger variability of Vmax measured vs expired volume implies a change in the expiratory effort from one forced expiration to another and a different degree of compression of intrathoracic air. Since this was not the case, we conclude that muscular effort during repeated forced expirations is similar. The good reproducibility of effort explains in great measure the good reproducibility of Vmax.

Adult↗
PubMed1978

Even distribution of 133Xe bolus inhaled at residual volume in healthy subjects.

We selected from among 46 healthy students (22 to 31-yr-old) 7 subjects (group A) in whom the normalized height of phase IV (height of phase IV/phase IIIx100), after inhaling a bolus of He at RV, was very small (10%). We compared them with 6 subjects (group B) selected on the basis of a tall phase IV (78%, A vs. P P less than 0.005). Age and height were comparable, but weight was lower (P less than 0.05) and RV/TLC ratio (but not other spirographic indices) was larger (P less than 0.025) in group A. The average amplitude of cardiac oscillations was 4 times higher in group B (P less than 0.005). He closing volume, but not closing capacity was less in group A (P less than 0.05). A bolus of 133Xe inhaled at RV was nearly uniformly distributed in group A while producing a large vertical gradient in group B. The difference between groups A and B may reflect a difference in the mechanical properties of the chest wall leading to a less complete empting of the lung in the former group.

Adult↗
PubMed1978

Influence of resting ECG abnormalities on the ECG response to maximal exercise in women suspected of coronary heart disease.

Coronary arteriographic data have been compared with the ECG response to a maximal exercise test in 53 women with typical or atypical complaints of angina pectoris (AP). All patients with factors known as influencing the repolarization at rest were eliminated and the cases were subdivided according to the presence of a normal (n=26) or abnormal (n=27) resting ECG. The sensitivity (88%) and specificity (81%) of the exertional ECG was not affected by the clinical history nor by the resting ECG data. False positive responses were frequent (32%), particularly among women with atypical AP (50%), but their prevalence was not influenced by the resting ECG data. We conclude that, even in the absence of drug therapy, non-specific resting ECG abnormalities do not influence the ECG response to exercise in women and that they cannot be considered as a factor contributing to the false positive responses: the latter appear to be related to the low prevalence of coronary artery disease in women.

Adult↗
PubMed1977

Difference between the He bolus and N2 technique for measuring closing volume.

We measured closing volume in sixteen healthy subjects simultaneously and separately with a bolus of He (using a rapid catharaometer) and with the N2 technique. In another group of 35 active workers (some with airway obstruction), closing volume was measured separately with those two methods. In both groups the He closing volume was significantly higher than the N2 closing volume. We attribute this difference to a less marked vertical N2 concentration gradient, leading to a less clearly defined separation between phase III and IV and resulting in an underestimation of the N2 closing volume. Indeed, increasing the N2 gradient in the lung, by inspiring O2 from a higher than residual volume level, increased the N2 closing volume which became comparable to the He closing volume. We also found, for both He and N2 tracings, a significant between-observers difference in reading of the closing volume. However, the difference in reading of ts difference in reading of the closing volume. However, the difference was less important for He closing volumes. We conclude that the bolus method improves the resolution of closing volume and decreases the interobserver variability.

Adult↗
PubMed1977

[Evaluation of the effects of cooling clothes on the adaptation to prolonged exertion in high temperatures by miners].

In order to improve the working conditions of coalminers exposed to high ambient temperature, the authors have studied the effects of wearing an under-vest and a cowl covering the head and shoulders made in sponge-cloth and soaked with cold water (cooling clothes). Eight coalminers volunteered for this study which included three sessions of prolonged intermittent exercise performed in a climatic room with the following ambient temperatures:--experiment A (comfortable environment): td = 28 degrees C; twb = 20 degrees C; bare head and bare torso;--experiment B (hot environment) :td = 38 degrees C; twb = 30 degrees C; bare head and bare torso;--experiment C (hot environment and cooling clothes) : td = 38 degrees C; twb = 30 degrees C; wet undervest and cowl soaked with cold water (16 degrees C) every 15 minutes. Each experiment included 5 periods of exercise each lasting 15 minutes separated by periods of rest lasting 15 minutes; the exercises were performed on a bicycle ergometer or on a treadmill and their intensity corresponded to 50% of the maximal oxygen intake. In the comfortable environment (experiment A), all subjects completed the experiment without undue fatigue; the final heart rate was 81/min and the final rectal temperature was 37.6 degrees C; the weight loss never exceeded 1 Kg. In the hot environment (experiment B), all subjects were exhausted at the end of the study which had to be shortened in 2 cases. The final heart rate was 125/min and the final rectal temperature 38.8 degrees C; the weight loss was above 2 Kg. The use of the "cooling clothes" in the hot environment (experiment C) resulted in significantly (p less than 0.001) lower heart rate (104/min), rectal temperature (38.3 degrees C) and weight loss (1.5 Kg); all subjects completed the experiment, none was exhausted and the "cooling clothes" were appreciated by all subjects. We conclude that the "cooling clothes" tested in the present study significantly reduce the physiological and subjective strain due to intermittent work in a hot environment; this cooling system is simple, of low cost and our results indicate that it is will be very useful in climatic conditions similar to those adopted in the present experimental protocol. Its usefulness in less severe climates has to be established but it might be limited by the subjective reactions of the subjects to the transient but sudden sensation of cold given by the "cooling clothes".

Adaptation, Physiological↗
PubMed1976

Evaluation of lung function indices for bronchodilator trials. Results of a cross-over study of fenoterol.

In 10 patients with airway obstruction, spirographic indices and maximal expiratory flow rates were measured before inhalation of fenoterol and at different time intervals, for 5 h, following the inhalation of 200 mug of this substance. 10 min after inhalation of fenoterol, there was a statistically significant increase in all lung function indices. A further increase was observed later. 3 h after inhalation of fenoterol, all indices were still significantly higher than control values. No side effects were observed. At all time intervals, the increase of the forced expiratory volume in 1 sec (FEV1.0), peak expiratory flow rate (PEFR) and maximal expiratory flow rate at 50 and 75% of the vital capacity reached a similar level of statistical significance. It is concluded that for the trial of the bronchodilator drugs, any of these indices may be used, and for practical purposes FEV1.0 and PEFR are best suited.

Adult↗
PubMed1975

A modified measurement of respiratory resistance by forced oscillation during normal breathing.

We have modified the measurements of the resistance of the respiratory system, Rrs, by the forced oscillation technique and we have developed equipment to automatically compute Rrs. Flow rate and mouth pressure are treated by selective averaging filters that remove the interference of the subject's respiratory flow on the imposed oscillations. The filtered mean Rrs represents a weighted ensemble average computer over both inspiration and expiration. This method avoids aberrant Rrs values, decreases the variability, and yields an unbiased mean Rrs. Rrs may be measured during slow or rapid spontaneous breathing, in normals and in obstructive patients, over a range of 3-9 Hz. A good reproducibility of Rrs at several days' interval was demonstrated. Frequency dependence of Rrs was found in patients with obstructive lung disease but not in healthy nonsmokers.

Airway Resistance↗
PubMed1975

Smoking and pulmonary diffusing capacity.

The pulmonary diffusing capacity (DLCO SB) and its two components, the capillary blood volume (Vc) and the diffusing capacity of the membrane (DMCO), expressed in absolute values and per litre of alveolar volume (VA'), were measured at rest and on exercise in healthy male smokers and nonsmokers of similar age and height, and with identical values for haemoglobin and spirographic data. DLCO, DLCO/VA', DMCO and DMCO/VA' are significantly lower in smokers, at rest and on exercise; the decrease in Vc and thetaVc/VA' in smokers at rest is due to a higher level of carboxyhaemoglobin. The decrease of DLCO, DLCO/VA', DMCO and DMCO/VA' is apparently not due to carboxyhaemoglobin or distributional factors but to anatomical lesions, probably of emphysematous nature, altering the pulmonary membrane. Formulas predicting DLCO, DMCO, Vc, DLCO/VA', DMCO/VA' and thetaVc/VA' in terms of age and height were established in smokers and in nonsmokers.

Adult↗
PubMed1975

Pulmonary gas exchange in asymptomatic smokers and nonsmokers.

Pulmonary gas exchange has been studied in 14 healthy smokers and 16 healthy nonsmokers (mean age: 36 years) breathing hypoxic, normoxic and hyperoxic gas mixtures, in a sitting position, at rest and on exercise. Alveolar-arterial oxygen tension difference is increased in smokers in hypoxia, at rest and on exercise, and the pulmonary diffusing capacity for oxygen is decreased. In normoxia the alveolar-arterial oxygen tension difference is increased on exercise. There is no difference between the two groups in hyperoxia. For the whole group there exists a negative relationship between (A-a)DO2 in normoxia and the diffusion indices measured on exercise. Arterio-alveolar carbon dioxide tension difference and the ratio physiological dead space/tidal volume are almost identical in both groups in any condition. A diffusion defect seems to be the more constant alteration of gas exchange in asymptomatic smokers.

Adult↗