ABSTRACT
Intermittent positive pressure ventilation is used as a respiratory support for acute respiratroy failure. Adult respiratory distress syndrome(ARDS) revealed mortality rate of 70% as yet. Hypoxemia is foremost problem in ARDS. Though various ventilatory support is tried on ARDS, extracorporeal membrane oxygenation(ECMO) is to be recommended when hypoxemia and hypercarbia are refractory to conventional treatments. Neonatal venoarterial (VA) ECMO in USA is recognized as a therapeutic modality for neonatal respiratory failure and extracorporeal carhon dioxide removal(ECCO2R) in Europe is used for adult respiratory distress syndome. The partial bypass using the membrane oxygenator aims at lung rest while relieving the hard ventilatory setting on the diseased lung. VA ECMO can provide circulatory support as well but the right internal jugular vein and the right common carotid artery are ligated for the cannulation of draiaage and perfusion catheters. Recent follow up study shows that VA ECMO may not be completely free from neurologic complications such as embolism in the systemic circulation and ill effects due to the reduction of blood supply to the immature lungs. ECCO2R adopts low-flow venovenous(VV) bypass. It has been reported to be valuable for treatment of neonatal respiratory failure. VV bypass provides gas exchange but no cardiac support. Venous drainage and perfusion catheters are placed in the right atrium or vena cavae via the femoral or internal jugular veins. Compared to VA bypass, the consequences of embolizations are potentially fewer, no major artery is sacrificed. Highly oxygenated blood flows into pulmonary eirculatiom which may relieve pulmonary artery hypertension. Total respiratory support may be obtained by VV bypass, VV bypass requires approximately 20-50% more flow for total respiratory sopport due to recirculation of oxygenated blood. Recently VV bypass is chosen for neonatal resyiratoty failure in USA. They alliveate the entry criteria for ECMO using the parameter of oxygenation index(OI). VV ECCO2R using to-and-fro system is tried also for neonatal respiratory failure in Europe. A double lumen tube was developed to reduce the number of veins to be cannulated during VV bypass. It is constructed with the outer drainage cannula( 14 Fr.) and the inner perfusion cannula( 8 Fr.) whose opening is placed on the left side of outer cannula. If perfusion opening is placed on the right atrium facing the right ventricle, the venous blood can be drained from both superior and inferior vena cavae through several drainage opening. To evaluate the effectiveness of ECCO2R with a double lumen tube, we developed an experimental model of acute respiratory failure on 8 mongrel dogs. Under general anesthesia with i.v, pentobarbital, a double lumen tube was introduced via the right internal jugular vein and it was connected with the extracorporeal circuit. Without ventilating the oxygenator during VV bypass, respiratory failure was induced by hypoventilation. After obtaining control hemodynamic and blood gas values under hypoventilation, we proceed to apneic oxygenation(AO), extracorporeal CO2 removal(ECCO2R) and controlled mechanical ventilation(CMV) in that order. Arterial pH in control was 7.180.09(meanSD), and it was increased to 7.33+/-0.08 and 7.28+/-0.08 in ECCO2R and CMV, respectively. PaCO2 in control was 69+/-9mmHg and it was decreased to 41+/-4mmHg and 47+/-7mmHg in ECCO R and CMV respectively. PaCO2 in control was 62+/-15 mmHg and it was increased in AO, ECCO2R and CMV. Mixed venous blood gas analysis showed the same result as arterial blood gas analysis. There was no difference between ECCO2R and CMV. The bypass flow enough to remove CO2 was 30-50% of cardiac output. It is concluded that ECCO2R using a double lumen tube was effective to control the carbon dioxide tension in arterial blood, and a double lumen tube may permit the simplicity of an operation and patient care as well as minimizing the bleeding during extracorporeal respiratory support.