Investigating the effects of random balloon pulsation on gas exchange in a respiratory assist catheter.

We are developing an intravenous respiratory assist catheter, which uses hollow-fiber membranes wrapped around a pulsating balloon that increases oxygenation and CO2 removal with increased balloon pulsation. Our current pulsation system operates with a constant rate of pulsation and delivered balloon volume. This study examined the hypothesis that random balloon pulsation would disrupt fluid entrainment within the fiber bundle and increase our overall gas exchange. We implemented two different modes for random (rates and delivered volume) versus constant pulsation. The impact on gas exchange was measured in a 3 l/min water flow loop at 37 degrees C. CO2 gas exchange for randomized beat rate mode was comparable to its corresponding average constant pulsation (e.g., constant 286 beats/min versus randomized 200-400 beats/min was 299.5+/-0.9 and 302.2+/-1.4 ml/min/m, respectively). Random volume mode CO2 exchange was also comparable to constant delivered balloon volume (100% inflation and deflation) (e.g., 294.3+/-0.6 and 301.1+/-1.7 ml/min/m, random 50-100% inflation and constant, respectively). Greater active mixing was seen with constant pulsation as compared with randomly changing the parameters of balloon pulsation.