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G Thews

Publications and source records attributed to G Thews.

11 recordsLinked to original sources
PubMed1976

Partitioning of the alveolar-arterial O2 pressure difference under normal, hypoxic and hyperoxic conditions.

The alveolar-arterial O2 pressure difference (AaDO2) is composed of three parts which depend on inhomogeneities of the ventilation-perfusion ratio (AaD(distr.) 1), on size and distribution of the diffusing capacity-perfusion ratio (AaD(distr.) 2), and on the effect of the shunt perfusion (AaD(sh)). These three parts can be calculated for normal, hypoxic and hyperoxic breathing conditions if the inhomogeneities of the function parameters and the size of the shunt perfusion are known. The calculation based on experimental data in 28 healthy subjects shows the following results: (1) Under hypoxic breathing conditions the AaD(distr.) 2 due to diffusion dominates. However, even at alveolar O2 pressures below 45 mm Hg the AaD(distr.) 1 must not be ignored. (2) Under normal breathing conditions AaD(distr.) 2 may be ignored and will under pathological conditions become relevant only if the diffusing capacity-perfusion ratio is below 3.10(-3) mm Hg(-1). (3) Under hyperoxic breathing conditions the AaD(sh) is predominant. However, even with the inhalation of pure oxygen, the AaD(distr.) 1 contributes 10% of the total AaDO2. (4) When evaluating the methods of measurement of the O2 diffusing capacity and of the shunt perfusion the inhomogeneities of ventilation, perfusion and diffusion must be considered.

Humans↗
PubMed1975

Critical diffusion ranges for oxygen and glucose in tumor tissue considering Michaelis-Menten kinetics.

The supply conditions for O2 and glucose in tumor tissue distinctly deteriorate with increasing tumor mass. As a result retardation in growth, lysis and necrosis take place because critical diffusion ranges are partially surpassed in heavier tumors. Applying in vivo-data to a special analogue computer it is possible to investigate the supply conditions including the range of very low O2 tensions and glucose concentrations. Using a definite arrangement of blood vessels it can be shown that the supply conditions only for one of the limiting substrates, i.e. for O2, are better than assumed hitherto. However, even the more realistic model reveals that regional failure in glucose and O2 obligatorily occurs during tumor cell proliferation.

Animals↗
PubMed1975

[PO-2-PCO-2-pH-nomograms for rat blood at 37 degrees C (author's transl)].

In order to determine the interdependence of the parameters of the respiratory gas transport in rat blood (Sprague-Dawley) CO-2-equilibration curves in fully oxygenated and deoxygenated blood are measured. The results are presented in the form of pH-log P-CO-2-diagrams. O-2-dissociation curves of rat blood are registered at different CO-2 partial pressures. The P-02 at S-02 equals 50% ranged between 27.7 mm Hg for P-C0-2 equals 20 mm Hg. 35.1 mm Hg for P-C0-2 equals 40 mm Hg and 42.2 for P-C0-2 equals 60 mm Hg. Cartesian and alignment nomograms are constructed using CO-2 equilibration curves and O-2 dissociation curves. These nomograms give the interrelations between P-O-2, P-CO-2, pH and S-0-2 of rat blood. Separate nomograms are presented for Hb-concentrations of 10-13 g-% and 13.1-16 g-% because of great variations of Hb concentration in rat blood. If two of these values are known the nomograms permit the reading of the remaining paramters.

Animals↗