An in vitro model for chemical extraction of carbon dioxide via modified peritoneal dialysis

An in vitro model of a new method for paracorporeal removal of CO2, consisting of modified peritoneal dialysis combined with chemical extraction of predominantly bicarbonate CO2, is presented. The peritoneal cavity was simulated by a bubble oxygenator into which 10% CO2 was diffused. Bicarbonate was initially added, but subsequently regenerated by the system. An insoluble chemical (barium hydroxide lime) was used to precipitate the bicarbonate and produce OH- ions, which prevent the acidosis anticipated with the loss of bicarbonate. CO2 removal was computed from the gas flow rate and CO2 concentration as measured with an infrared analyzer. The rate of CO2 removal was found to be a directly linear function of dialysate flow rate, gas flow rate, and concentration of bicarbonate. The model removed 60 ml/min of CO2, but it is capable of removing more, since the variables affecting CO2 removal are controllable by the observer. This new method can extract bicarbonate CO2 without causing depletion of bicarbonate or requiring an infusion of alkali. It is potentially useful in management of hypercapnic respiratory failure and as an adjunct to "apneic oxygenation" in respiratory distress syndrome.