Rolf Zander

Proposal for Using a Standardized Terminology on Oxygen Transport to Tissue

The aim of the present proposal is to recommend some definitions of important and frequently used terms in the field of oxygen transport to tissue. The latest glossary on this topic is dated 1973 and was published by the International Union of Physiological Sciences (J. Appl. Physiol. 34, 549 – 558, 1973). In the meantime, some of these definitions are either outdated or are used in another sense.

Cellular Oxygen Concentration

At low oxygen levels the intracellular or intramitochondrial concentration of molecular oxygen together with the amount of reduced cytochrome oxydase determines the rate of oxygen utilization. Below the so-called “critical oxygen concentration”, i.e. the value, at which a drop in the rate of oxygen uptake has its first evidence, the kinetic is described by the oxygen affinity (Km) of the respiratory chain, i.e. the concentration value for half maximal rate of oxygen uptake.

Influence of intracellular convection on the oxygen release by human erythrocytes

SummaryThere is general agreement today that intracellular diffusive transport of HbO2 and O2 limits the rate of oxygen uptake or release by the blood in the exchange vessels. Recent hemorheological results have shown that the mammalian erythrocyte exhibits fluidity as its most unique rheological property: it can be deformed continuously and rapidly, shear and normal stresses can be transmitted to the interior of the cell where systems of laminar flow are induced. These mechanical properties lead to the question whether or not intracellular convection does take place in the erythrocyte and to what extent it plays a part in gas exchange. A method was developed which subjects oxygen-saturated solutions and cell suspensions to an artificial but well defined flow (cone-plate-viscosimeter), and allows simulataneous determination of the initial O2 release indices under standardized conditions (O2 saturation, temperature, time, diffusion area, and difference of O2 partial pressure). The results strongly suggest that intracellular flow resulting from the physiological erythrocyte deformation in flow can supplement the O2 release from intact cells through a convective transport of HbO2 and O2 molecules. The example of osmotic shrinking shows that red cell fluidity is not only a precondition for normal flow in the microcirculation, but also for the normal gas exchange of the cells.

Intracellular mechanisms of oxygen transport in flowing blood

Abstract As a side effect deformation of red cells in the microvasculature produces intracellular convection. Therefore, beside the conventionally assumed diffusive intracellular oxygen transport an additional convective transport must definitely be taken into consideration, which increases the rate of gas exchange by the blood distinctly. In this paper an attempt is made to determine quantitatively the relative role of the four possible mechanisms of intracellular oxygen transport, i.e. diffusion and convection of both dissolved and chemical bound oxygen. They can be detached from each other by measuring the oxygen release of resting and flowing blood before and after inhibiting the HbO2 system by carbon monoxide. Under the present experimental conditions (packed cells in viscometric flow) intracellular convective oxygen transport is of greater significance than the diffusive; its relative role increases with time of deoxygenation.

Solubility of NH3 and apparent pK of NH4+ in human plasma, isotonic salt solutions and water at 37°C

Abstract The solubility of ammonia, α NH 3 (mM/mmHg), was determined at 37°C and low ammonia partial pressure (0.02–1 mmHg) in pure water ( n =24) as 46.7±0.40; aqueous isotonic salt solutions ( n =7) as 46.8±0.81; and human plasma ( n =5) as 42.0±0.66. The last figure increases to 45.3±0.63 if expressed in molal units (mmol/kg plasma water·mmHg) instead of molarity with respect to the water content of the plasma (mean from four healthy and fasting donors: 0.908±0.005 kg H 2 O/kg plasma; mean density at 37°C: 1.020±0.002 kg/l). In pure water, the solubility value is the mean of three different methods: (a) extrapolation of the salting-out effect of ammonia in aqueous NaOH to zero concentration; (b) slope of Henry–Daltons law and (c) directly measured in pure water and 0.001 M aqueous NaOH. Based on the Henderson–Hasselbalch equation for the system NH 4 + /NH 3 in isotonic salt solutions and human plasma, both constants, apparent p K and solubility, can be derived from total ammonia concentration and pH at equilibrium with defined ammonia gas phase, if additionally the concentration of NH 4 + or NH 3 is known. This was verified, in the first case, by determining the concentration of NH 4 + by the experimental conditions, and in the second, by two measurements of total ammonia concentration at two different pH values. Total ammonia concentration was measured by a specific enzymatic standard test and pH with the glass electrode. The mean apparent p K was 8.968±0.013 in isotonic salt solutions ( n =7), and in human plasma ( n =10) it was 9.014±0.033.

A sensitive continuous and discontinuous photometric determination of oxygen, carbon dioxide, and carbon monoxide in gases and fluids

Abstract The paper describes a sensitive, rapid, and precise photometric method for the continuous and discontinuous determination of O 2 , CO 2 , and CO. The method is based on highly specific color reactions: O 2 is determined by its reaction with alkaline catechol + Fe 2+ yielding intensively colored products, CO 2 is determined by its color reaction with a solution of fuchsin + hydrazine; and CO is determined by its reaction with hemoglobin. The basic experimental equipment is that of the AutoAnalyzer (cf. Wolf, Zander, and Lang, 1976 , Anal. Biochem. 74 , 585), with an additional chamber for the injection of small gas samples in the case of the discontinuous analysis. Continuously analyzing in a standardized gas flow of 1 ml · min −1 (STPD), the lower limits of the sensitivities are 50 ppm for O 2 , 100 ppm for CO 2 , and 50 ppm for CO. The discontinuous analysis of the three gases requires the basic experimental equipment plus an airtight chamber. The lower limits of the amounts are 0.1 μl (STPD) for O 2 , 0.2 μl for CO 2 , and 0.1 μl for CO.

Optimal Pre-Oxygenation: The Nasoral-System

The human body’s intra-and extrapulmonary O2 reserves, i.e. the oxygen stores of the functional residual capacity (FRC) and the blood, will be rapidly depleted during any kind of respiratory arrest (apnea). Application of oxygen prior to iatrogenic apnea (e.g. for endotracheal intubation procedures), therefore, commonly is discussed [e.g. Miller, 1990] as the proposed measure designed to achieve an increase in the human body’s oxygen stores sufficient to avoid hypoxemia. This prophylactic application of oxygen simply has become to be termed “pre-oxygenation”, regardless of the amount of increase in the O2 stores actually achieved. A myriad of different techniques and procedures are practically used, although only few information has been provided by textbooks referring to this so-called “pre-oxygenation” [e.g. Atkinson et al., 1986; Larsen, 1989; Miller, 1990].

Clinical Use of Oxygen Stores: Pre-oxygenation and Apneic Oxygenation

During states of respiratory arrest the human oxygen stores may be used therapeutically, regardless of the origin, i.e. either prior to the routinely induced apnea for endotracheal intubation or as an emergency measure in any other case of apnea. The present considerations focus on the clinical use of the oxygen stores available, applying.

The Determination of Haemoglobin äs Cyanhaemiglobin or äs Alkaline Haematin D-575 Comparison of Method-Related Errors

In order to compare the accuracy of haemoglobin (Hb) determination methods, the commonly used cyanhaemiglobin (HiCN) method and the recently developed alkaline haematin D-575 (AHD) method (R. Zander, W. Lang & H. U. Wolf (1984) Clin. Chim. Acta 136, 83-93; H. U. Wolf, W. Lang & R. Zander (1984) Clin. Chim. Acta 136, 95-104) were tested with respect to method-related errors such as plasma, cell, and Hb errors. Both methods yield a series of more or less significant errors which generally lead to an overestimation of the Hb concentration in the order of 1%. However, in all three cases of plasma errors, i.e. normal plasma error, plasma error in lipaemic blood, and plasma error in bilirubinaemic blood, the AHD method shows significantly lower values of errors than the HiCN method. In the case of cell errors such as ghost and leukocyte errors, the overestimation of the Hb concentration by the HiCN method is 60% higher than that by the AHD method. In the case of Hb errors such as fetal Hb and carboxy Hb errors, there is a significant overestimation of the Hb concentration by the HiCN method, which amounts 3 min after mixing of blood and HiCN solution to 0.7% in the case of fetal Hb and to 13.2% in the case of carboxy Hb. The latter value yields an overestimation of 1.3%, when 10% carboxy Hb in a blood sample is present. In contrast, there is no detectable overestimation after 3 min in the case of the AHD method. Thus, the AHD method provides a higher accuracy in Hb determination than the commonly used HiCN method.

Corneal Oxygen Supply Conditions

Pronounced cornea hypoxia induces swelling and a loss of transparency. Hypoxia of longer duration causes necrosis, particularly of the corneal endothelium. These findings were observed after ligation of the cilial arteries and the arteria carotis interna, after reduction of oxygen tension on the anterior corneal surface as well as after prolonged wearing of ill-fitted contact lenses (11, 15, 18, 22, 23). Because the normal function of the corneal endothelium plays a central role in maintaining transparency, an insufficient endothelial oxygen supply can directly influence vision (3, 17).