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S C Luijendijk

Publications and source records attributed to S C Luijendijk.

41 records · Page 3Linked to original sources
PubMed1981

Evaluation of alveolar amplitude response technique for determination of lung perfusion in exercise.

We investigated the influence of tracer gas venous return on the determination of pulmonary perfusion (Qp) using the alveolar amplitude response technique (AART) to evaluate the applicability of this technique at rest and during exercise. The venous return influence was calculated by a computer simulation applied to a simplified body compartment model. Using the AART method, which neglects the influence of venous return, a simulation based on acetylene as a tracer gas predicted an overestimation of the actual value of Qp ranging from 0 to 10% for all work loads investigated. These theoretical results were compared with experimental results. Experiments with human subjects with acetylene as the tracer gas yielded an underestimation of Qp of about 20% at rest and an overestimation of about 7% under different exercise conditions. Experiments with anesthetized dogs showed an underestimation of Qp of about 12% for acetylene and about 6% for halothane. The theoretical and experimental results related to exercise conditions are thus in good quantitative agreement. The experimental data obtained for acetylene with human subjects at rest and with anesthetized dogs are also in good quantitative agreement. However, they deviate considerably from theoretical predictions. This discrepancy may be due to the simplified body compartment model used in the calculations, which can considerably influence the calculated results, especially for conditions at rest. The main conclusion of this paper is that recirculating tracer gas does not unduly influence results for Qp obtained with the AART method when halothane is used as the tracer gas.

Acetylene↗
PubMed1981

Helium and sulfur hexafluoride washout in asymmetric lung models.

Model calculations were carried out on extensible lung models that are characterized by asymmetries in branching pattern or cross section within the acinus. The calculations contribute to a better understanding of the intrapulmonary mixing of gases poorly soluble in blood. For single-breath washout stimulations of helium (He) and sulfur hexafluoride (SF6), only small differences were found between the results obtained from a lung model with an asymmetric branching pattern using either a local homogeneous or inhomogeneous delta V/V distribution. This indicates that the geometry of this model is the most important factor for generating realistic values for the slope of the alveolar plateau, the Bohr dead space and the end-tidal concentration ratio for SF6 and He. The calculated relation between the decrease in the slope of the alveolar plateau and postinspiratory breath-holding times showed good agreement with experimental findings in healthy adult subjects. Multiple-breath washout simulations enabled us to explain the experimentally observed high dilution of poorly soluble tracer gases in the end-tidal gas for the first few breaths during the washout procedure. Simulations of simultaneous multiple-breath washout experiments of He and SF6 showed that a shift in the crossover point of the normalized end-tidal washout curves is related in particular to cross-section asymmetry of the lung model. These asymmetric lung models are the only ones described up to now that explain many of the features of single- and multiple-breath washout experiments for gases poorly soluble in blood.

Fluorides↗
PubMed1980

The sloping alveolar plateau at synchronous ventilation.

We performed model calculations on the slope of the alveolar plateau at single breath washout of helium (He) and sulphurhexafluoride (SF6). Calculations wre carried out on an extensible axis-symmetric lung model, which was synchronously ventilated either equally or unequally. The calculated slopes of the alveolar plateau were small (<0.3%), which is in agreement with the results of other investigators. However, calculations carried out on a synchronously equally ventilated axis-asymmetric lung model related to the terminal lung unit (acinus), yielded slopes for the alveolar plateau ranging from 0 up to 14% per liter between 1.2 and 1.8 1 expired volume. Even with a post inspiratory apnea of 1 s, we still found slopes ranging from 0--4%. Our findings are in contrast to the conclusions of Engel et al. (1979), who ascribe the slope of the alveolar plateau to asynchronous unequal ventilation.

Computers↗