PULM5: Hyperbaric Blood Oxygenation – Basic Considerations and First Results

Abstract

Hyperbaric oxygen therapy is beneficial in several applications, but hyperbaric chambers are scarce. We are developing a novel technology for extracorporeal hyperbaric blood oxygenation (HBOX). This extracorporeal procedure uses pressure to increase the oxygen (O2) concentration in blood. The technology can provide support when large amounts of oxygen are needed: In the treatment of CO poisoning the dissolved oxygen displaces the CO from the blood, removing it from the organism. This way, the oxygen deficiency can be ended rapidly, reducing or preventing secondary damage that frequently occurs. In acute respiratory failure (ARF) the HBOX technology can support lung function, by significantly increasing oxygen transport across a specific membrane area, while maintaining adequate CO2-removal. The prototype of the HBOX consists of 2 roller pumps with a hollow-fiber membrane oxygenator (HFMO) placed in between, a control unit for gas and blood flow and a double lumen catheter. By varying the flow rates of the roller pumps, excess pressure is generated in the HFMO without causing significant blood damage. Simultaneously, the oxygen pressure in the HFMO is increased, allowing for hyperbaric oxygenation. To avoid bubble formation, either O2 increase is limited, or excess O2 is removed in second HFMO before reinfusion. The prototype was tested in-vitro using porcine blood that was either CO poisoned or conditioned to mimic ARF. In acute in-vivo experiments for CO poisoning, we used CO-poisoned pigs (ca. 75 kg, COHb = 43 %, n = 3). For in-vivo experiments for ARF, 70 kg sheep were used with ventilator settings simulating respiratory failure, resulting in SaO2 = 69 %, paCO2 = 72 mmHg (n = 2). In-vitro test results show that the HBOX can fully oxygenate hypoxic blood (sO2 ca. 40 %) with a hilite 800 LT at a flow rate of 2 L/min, which is twice the amount of oxygen transferred, compared to conventional mode, Fig. 1. In in-vivo trials, the CO elimination rate from the animals’ blood doubled when using HBOX + oxygen mask compared to oxygen mask alone, see Fig. 2. In the ARF trials, the HBOX approach resulted in SaO2 of 89, 95, and 99 % and paCO2 was 49, 46, and 39 mmHg at blood flows of 0.5, 1.0, and 1.5 L/min, respectively, see Fig. 3. The HBOX is a promising approach to increase oxygen transport across a specific membrane area. The increased oxygen levels can be used for efficient extracorporeal CO removal. For respiratory support, the hyperbaric technology adds a new dimension to ECMO treatment, allowing the use of smaller oxygenators, potentially reducing the need for anticoagulation, as well as inflammatory responses and thus invasiveness. The hyperbaric technology can be used gradually, so that the membrane efficiency can be increased during intervention. This allows us to build an oxygenator with an ideal flow distribution over a wide range of blood flows, which avoids thrombus formation in the device at lower blood flows.Figure 1. Laboratory results oxygenation performanceFigure 2. Elimination rate COHb in in-vivo trialsFigure 3. Arterial blood gases during in-vivo trial for ARF