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Biomedical subjects

R Peslin

Publications and source records attributed to R Peslin.

174 records · Page 10Linked to original sources
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[Experimental chronic paraquat poisoning. Functional and histopathological pulmonary changes].

An experimental model of pulmonary interstitial fibrosis was attempted in beagle dogs by intravenous administration of weak doses of paraquat. After various trials, the final protocol involved the intravenous injection of 2 mg/kg repeated every eight days for three weeks, and then every 15 days. On the 70th day, areas of localized interstitial fibrosis were observed (less than 10% of the surface of the tissue sections) in an otherwise healthy parenchyma. There was no marked hepatic or renal lesion. The evolution of the inflammatory and toxic processes was followed by the changes: 1) in the animal's weight (drop in weight after the injection of paraquat), 2) in blood gases (essentially drop in PaO2 and in SaO2), 3) in ventilation and respiratory exchanges (increase of VE and ventilatory frequency, decrease of Duco2), and 4) in static pulmonary compliance (distinct fall after injection). All these modifications showed a close relationship to the pattern of the paraquat injections. They receded 15 days after the last injection and reappeared after a new injection. The pulmonary hemodynamic study carried out only at the beginning of the experiment and before the animal was killed showed only a few anomalies (reduction of the average pressure of the right atrium).

Animals↗
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[Forced expiration index, signal and noise].

Although forced expiration measurements are extensively used, there is no general agreement concerning the best way to quantify the data. In this context, it may be of interest to examine indices from the point of view of their signal/noise ratio. The signal depends upon the actual sensitivity of the index to the kind of abnormality which is to be detected. In general, the relationship between signal and degree of abnormality is strongly non-linear, so that sensitivity is not a constant. The noise depends upon the kind of investigation which is made. When a subject is compared to himself (bronchomotor challenge, follow-up studies, etc.), it is mainly due to intraindividual variability. FEV1 is an example of index with a low sensitivity to peripheral airway abnormality, but a high reproducibility, so that its signal/noise ratio for paired measurements is comparatively good. When two groups are to be compared, the relevant noise is interindividual variability. Coefficient of variation of transit times and slope ratios are quite effective in detecting abnormalities in young smokers, probably because their sensitivity to mild peripheral airway disease is large compared to their interindividual variability. It follows that, according to the type of study, as well as to the nature and extent of abnormality, many indices may qualify as being the best.

Forced Expiratory Flow Rates↗
PubMedDate not supplied

[Harmonic content of the flow signal during forced expiration in normal man (author's transl)].

In order to define the minimal frequency response requirements for spirometric measurements, the harmonic content of forced expiratory flow has been assessed in 63 healthy subjects. The amplitude of the harmonics has been found to decrease almost exponentially with increasing frequency. On the average, the cumulated frequency content beyond 10 Hz represented less than 5% of the total frequency content in men, and less than 3% in women. No significant difference has been observed between male smokers and non-smokers. The harmonic content per unit frequency has been found to be correlated to maximal flows at middle and low lung volumes and to maximal mid-expiratory flow up to 4 Hz. For FEV1, maximal flow at 75% of the vital capacity and, particularly, peak expiratory flow rate (PEFR), the correlations were still significant at quite higher frequencies. The data suggest that, except for PEFR, all these indices may be obtained with a good accuracy when the frequency response of the equipment is flat up to 5-7 Hz.

Adult↗
PubMedDate not supplied

The unreliability of indirect lung compliance in healthy subjects and patients with chronic lung disorders.

The clinical usefulness of lung compliance calculated indirectly was reassessed in a large number of healthy subjects and patients with chronic airflow obstruction or restrictive lung disorders. Indirect compliance was calculated from maximal expiratory flow-volume (MEFV) curve and airway resistance measured plethysmographically according to two approaches. In the first (approach A) all calculations were done at the functional residual capacity, whereas in the second (approach B) they were obtained over the 50-75% volume range of the forced vital capacity; values were compared to those of direct compliance measured concurrently. For the group as a whole, the correlations between indirect and direct values were poor regardless of the approach. Examined separately, the best correlations were found for the healthy group using approach A (r = 0.501) and for the obstructive group using approach B (r = 0.312). Failure to derive a valuable indirect compliance is due to the fact that there is a very poor correlation between upstream resistance and airway resistance measured by body plethysmography.U

Adult↗
PubMedDate not supplied

Comparison of four methods for calculating the total lung capacity measured by body plethysmography.

Static lung volumes were measured plethysmographically one hour apart in healthy subjects (n = 14) and in patients with chronic pulmonary disorders of various etiologies (n = 25). The total lung capacity (TLC) obtained from paired measurements of functional residual capacity (FRC) and inspiratory capacity (IC) was calculated according to the four following methods: 1) average FRC plus the largest IC, 2) average FRC plus the average IC, 3) largest sum of FRC and corresponding IC, and 4) average of individual FRC and IC sums. The data, analysed for average values and for reproducibility in the group as a whole and in the healthy subjects and patients separately indicate that: a) For the group as a whole the largest average TLC values were found with method 3 followed by methods 4 and 1. The differences were statistically significant for all comparisons but one (method 1 vs method 4). A similar pattern was found for the healthy subjects and patients separately. b) For the group as a whole, the one hour reproducibility tended to be worse from method 1 through method 4 but the intermethod differences were not statistically significant. For the healthy subjects, the reproducibility tended to be better for methods 3 and 4 and for the patients this was the case for methods 1 and 2. The average reproducibiltiy of methods 1 and 2 was similar for both the healthy and patient groups and these methods seemed more suitable for TLC calculations. Because it is more widely employed, method 1 is recommended.

Adolescent↗
PubMedDate not supplied

[Mechanical impedance of the chest in smokers and non-smokers (author's transl)].

Mechanical impedance of the respiratory system was measured at 5, 10, 15 and 20 Hz in 47 healthy non-smokers, 20 ex-smokers and 51 current smokers. Besides the resistance and its frequency dependence, the compliance, the inertance and the resonant frequency of the respiratory system were computed using the assumption of a second order linear system. The data were normalized for sex, age and body height on the basis of correlations observed in non-smokers. No significant difference was found in ex-smokers. In smokers the resistance was significantly increased at all frequencies. However, it was normal in a number of subjects with abnormally low maximal expiratory flows. unlike maximal flows, forced oscillations indices were not correlated to tobacco consumption expressed in pack-years. The results do not indicate that impedance measurements breathing air may be specially useful for early detection of airway abnormalities.

Adult↗