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Biomedical subjects

G Atlan

Publications and source records attributed to G Atlan.

At least 55 records · Page 3Linked to original sources
PubMed1982

Improved method in the computer determination of plethysmographic thoracic gas volume.

To improve the computer determination of thoracic gas volume (TGV), two new approaches were worked out. 1) A new program was designed, which overcomes the difficulties encountered in the time recognition of the panting maneuver and rules out the artifacts. Such a procedure is based on the data analysis in the pressure-volume time derivatives plane. 2) A hyperbolic fitting of the signals recorded during the panting maneuver was introduced. This last procedure, lying on Boyle's law, has proved to be useful in case of large mouth pressure changes. In fact the error induced by the conventional linear fitting may reach 500 ml (9% of the TGV value).

Computers↗
PubMed1981

Correction for nonlinearity of body flow plethysmograph.

A modification of conventional signal processing for the pressure-compensated flow plethysmograph is proposed to correct the nonlinearity of the flow element that appears for high flows as encountered during forced expiration. Woven screens behave as porous media with a viscous and an inertial component in the resistance; this explains the nonlinearity (23% at 15.1.s-1 with a 400-mesh wire screen area = 50 cm2). It was shown that the pressure drop-flow relationship can be described by a second-degree equation, which can be included in the computation of the thoracic signal from the box pressure. The need for such a correction is evidenced by testing the plethysmograph with a flow step input (0-15 l.s-1) equivalent both in amplitude and in frequency to the thoracic flow during a forced expiration. Such correction for nonlinearity avoids an overestimation of the thoracic forced vital capacity of up to 0.5 liter in normal subjects.

Humans↗
PubMed1980

Computer determination of thoracic gas volume using plethysmographic "thoracic flow".

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume

Diagnosis, Computer-Assisted↗
PubMed1977

Lymphocutaneous nocardiosis due to nocardia brasiliensis.

A farmer had chaining lymphocutaneous granuloma on the right hand and arm. Clinically the syndrome seemed typical for sporotrichosis. Bacteriological examination revealed Nocardia brasiliensis as the only etiologic agent. Since 1920, eight similar cases of sporotrichoid nocardiosis have been reported from various parts of the world. To our knowledge, isolation of N brasiliensis has not been reported previously in this geographical area.

Diagnosis, Differential↗
PubMed1975

[Chronic respiratory insufficiency. Incidence in the results of surgical valvular replacement].

Out of 400 files of patients who underwent valvar correction between 1968 and 1974 under extra corporeal circulation by the thoracic route through median sternotomy 180 were kept for this study. All these 180 patients had a complete functional spirometric examination before operation, analysed in correlation with their valve disease. 39 of them had severe ventilatory insufficiency. Nevertheless the post-operative period was usually simple, and respiratory insufficiency was responsible for one death only of this series. These data were confirmed by the study of 45 autopsied patients who died after operation. At distance from operation, 80 patients were studied, 25 of whom had severe ventilatory insufficiency. In more than half the cases, and particularly in the mitral ones, the ventilatory deficiency was improved. Thus it is concluded that, respiratory insufficiency is rarely a contra-indication to valve replacement surgery in habitual conditions of the median sternotomy as a thoracic route.

Adolescent↗