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R Georges

Publications and source records attributed to R Georges.

68 records · Page 4Linked to original sources
PubMedDate not supplied

[Variation of effective compliance with respiratory frequency. Test of inhomogeneity of the ventilatory mechanical system (author's transl)].

A decrease in effective compliance (Ce) with increase in respiratory frequency (f) is considered as representing an inhomogeneity in the distribution of the pulmonary time constants. The Ce variation in relation with f reflects the inadequacy of the first order linear mono-alveolar model usually used to describe the ventilatory mechanical properties. Such an assertion is widely accepted, but few attempts have been done to validate this point in patients and to determine the various components likely to affect the Ce, f relationship. In 171 patients, selected in order to sample different types of lesions of some pulmonary structures, the authors calculated the next functional parameters : VC/theoretical VC ratio, RV by dilution method and by plethysmography, airway resistance and distribution index of inspired gas. Moreover, by means of a computerised system, the effective compliance and its variation with respiratory frequency have been calculated. After discussion of the procedure and of the method used to express the compliance-frequency relationship (linear regression), the authors develop the arguments which allow to assert that despite the elementary type of expression the relation is a good discriminative parameter. Its signification is discussed by analysing results obtained in patients and by simulating a mathematical model of the ventilatory mechanics where the mechanical parameters are distributed. It seems likely that a negative slope of the compliance-frequency relationship expresses an important mechanical inhomogeneity. Taking into account the fact that the whole frequency-compliance relationship gives little information, at this moment, in the face of an unpleasant test for the patients, the authors propose a simplified procedure, adapted to the usual practice.

Asthma↗
PubMedDate not supplied

Respiratory function in recent pulmonary sarcoidosis with special reference to small airways.

This study was designed to evaluate airway dysfunction in relation to duration of disease in patients with pulmonary sarcoidosis for less than two years. Twenty four subjects with recent disease were compared with nine subjects with disease of more than two years' duration. They underwent lung function testing (lung volumes, lung transfer factor for CO and pulmonary mechanics). Small airway function was assessed using frequency dependence of compliance, closing volume, nitrogen single breath test and flow-volume curves breathing air and helium-oxygen mixture. Airway dysfunction was seen in pulmonary sarcoidosis even in some patients with recent disease and it became more evident in disease of longer duration. The results suggest small airway involvement. The frequency of airway dysfunction is difficult to evaluate, varying from estimates of 0% using flow-volume curves to 79% with frequency dependence of compliance. This apparent discrepancy could be explained by the consequences of parenchymal involvement leading to inhomogeneities in distribution of compliance, and of elastic lung recoil. We conclude that patients with recent sarcoidosis are probably affected by intrinsic small airway disease, but an increase in elastic recoil often conceals its consequences. The airway disease may not be apparent using conventional function tests and published predicted values.

Adult↗
PubMedDate not supplied

Lung transfer factor for carbon monoxide measured during a slow single breath without breath-holding and during slow exhalation.

We considered whether a slow single breath with neither breath-holding nor carefully controlled flows could provide estimates of lung transfer factor for CO (TLCO) similar to those obtained with the usual standardized single breath technique. This technique requires actual flow rates and volume variations to be taken into account [10], as well as the use of a fast CO analyser and computerized calculations. TLCO values found with this method (TLCOsb) for 5 normal subjects and 29 patients with various respiratory diseases did not differ from those obtained with the standardized test (p less than 0.001). TLCO was also measured during exhalation only, by the use of a single compartment, constant TLCO equation and a computational procedure which provided a mean TLCO value for a given expired volume range (TLCOex). A unique TLCOex was sufficient to account for the whole exhalation in normal subjects and certain patients. In most patients two TLCOex were necessary, one for large lung volume after dead space washout and the other one accounting for the second half of expiration until closing volume. Most TLCOex were larger than TLCOsb calculated during the same slow breath. This over-estimation was found to be correlated (p less than 0.001) with the phase III argon slope. In patients where two TLCOex values were required to describe the exhaled CO course, we found that TLCOex decreased with lung volume. This decrease was also correlated with the argon slope (p less than 0.001). The observed difference between TLCOsb and TLCOex values and the decrease of TLCOex with lung volume probably reflect inhomogeneous ventilation distribution.

Adult↗
PubMedDate not supplied

[Closing volume and inhomogeneity of the ventilatory mechanical system (author's transl)].

The use of the closing volume (VF) to detect small airway lesions is based on physiological data : it would reflect a special and physiological distribution of the pulmonary inhomogeneity. The aim of this work is to discuss the closing volume as used to determine a pathological process or, in other words, the relationship between the observed profile of closing volume and other functional parameters, whose abnormalities are likely to reflect the inhomogeneity of the ventilatory mechanical system. In 126 patients, who represent a wide range of pathological processes, the authors calculated the closing volume and the following functional parameters : the VC/theoretical VC ratio, the RV measured by dilution method and by plethysmography, the FEV1.0/VC ratio, the expiratory total pulmonary resistance (RPTE), the efficient resistance (R), the airway resistance (Raw), the effective compliance (Ce) measured at the spontaneous respiratory frequency, and its variation in relation with respiratory frequency (f), and a distribution index of inspired gas. After discussion of the procedure and of the reproducibility of the closing volume measurements, the authors recall the significant of the lack of phase IV during the closing volume estimation and expose the reasons which allow to think that closing volume extent and inhomogeneity of the ventilatory mechanics have a parallel evolution. The increase in distribution inhomogeneity of the pulmonary time constants (shown by the slope of the Ce variation in relation with f and gas distribution index) is concomitant with an increase in closing volume. The results show that although the lack of phase IV does not have a univocal signification (and this is a limit to the utilization of the closing volume alone as a detection test) the quantification of the closing volume brings, as the Ce, f relation does, an original element, but the evaluation of Ce, f is more difficult to realize in practice.

Humans↗