Biomedical subjects
Publications and source records attributed to J E Lafosse.
A case of thoraco-abdominal rigidity leading to respiratory failure is described in the post-operative period in an elderly patient who received a moderate dose of fentanyl. This was successfully reversed by naloxone. The mechanisms possibly implicated in this accident are discussed.
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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.
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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.