Capillary oxygenator

Ang C, Tan TH, Walters WAW, Wood C. Postural influence on maternal capillary oxygen and carbon dioxide tension. Br Med J 1969 4 201-203. 

The largest current application of gas-separation membranes is separation of nitrogen (N2) from air. Capillary modules formed into bore-side feed modules are used almost exclusively in this application [10, 11]. The feed air is compressed to 6-10 bar and pumped through the membrane capillaries. Oxygen (02) permeates the membrane preferentially, leaving an oxygen-depleted, nitrogen-rich residue stream. The first membranes used for this application were based on poly(4-methyl-l-pentene) and ethyl cellulose, and had 02/N2 selectivities of about 4. Because of the modest... 

The predicted partial pressure in the capillary can be computed by inverting Equation (8.14) to convert from total oxygen to partial pressure. The oxygen profile in the tissue as a function of r and z is given by combining Equation (8.19), which gives the capillary oxygen concentration as a function of z, with Equation (8.11),... 

In theory, there are three causes for the occurrence of HPS (since hypoventilation is not deemed a possible cause) (1.) arteriovenous shunts, (2.) disturbed alveolo-capillary oxygen diffusion in terms of impaired diffusion-perfusion, and (3.) mismatches between ventilation and perfusion. Consequently, there are numerous liver diseases which are associated with HPS. Transient HPS in acute viral hepatitis A and B has recently been reported. (17, 38) (s. tab. 18.1)... 

Since the consumption of oxygen by the fetus is not considered in this study, a maternal blood velocity change to a zero velocity would result in a fetal end capillary oxygen concentration that is equal to the... 

Examination of the curves of Figure 21 shows that as the magnitude of the period of oscillation of the velocity function decreases (from 45 sec to 15 sec), the minimum fetal blood end capillary oxygen concentration increases from 26.3 mm Hg for a period of 45 sec to 27.8 mm Hg for a period of 15 sec. Additionally, the maximum fetal oxygen concentration decreases from 30 mm Hg (the normal value) for the 45-sec period to 28.6 mm Hg for the period of 15 sec. Thus, longer periods of contrac-... 

Unsteady-State Analysis Including Axial Dispersion. As in the previous unsteady-state analysis, the effects of placental barrier tissue oxygen consumption are neglected in this study. For the unsteady-state analysis of the model in which axial dispersion was included, one study was conducted. This study involved placing a step change on the maternal blood velocity to a new maternal blood velocity of 0.125 times the normal in an attempt to determine the effects of axial dispersion on the system at low maternal blood velocities. The discussion of this study is divided into the following two parts first, the effect of axial dispersion on the response of the fetal blood end capillary oxygen concentration, and second, the effect on the transient axial profiles. 

A capillary oxygenator has been used on a number of infants with good performance (5). Present difficulties with the capillary lung lie in the area of fabrication, particularly in the manifolding of blood into the capillary channels. 

However, as blood flows along the capillary, oxygen is extracted by the tissue and the oxygen partial pressure in the blood declines rapidly. The oxygen partial pressure in the tissue also declines rapidly and a point is reached where zero-order kinetics no longer applies. The complete form of the Michaelis-Menten equation must be used, requiring a numerical solution of equation (1-118). McGuire and Secomb (2001) showed numerically that under the set of conditions considered in this example, as much as 37% of the tissue was hypoxic. 

Number of capillaries Density of capillaries Oxygen affinity of blood Total peripheral resistance... 

The pOj in blood is distributed so that the oxygen dissociation curve for hemoglobin has the steepest slope in the arterioles where the adrenergic sensor system has the highest density [76]. Arterioles ahead of this fulcrum deliver most of the oxygen to the tissues at rest. Capillary oxygen delivery becomes predominant in working tissue [78]. 

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