Reduced ventilator pressure and improved P/F ratio during percutaneous arteriovenous carbon dioxide removal for severe respiratory failure

Objective To evaluate the effect of percutaneous arteriovenous carbon dioxide removal (AVCO(2)R) on ventilator pressures and P/F ratio in a clinically relevant large-animal model of severe respiratory failure. Summary Background Data AVCO(2)R was developed as a simple arteriovenous shunt with a commercially available low-resistance gas exchange device of sufficient surface area for near-total CO2 removal. With an AV shunt 10% to 15% of cardiac output, AVC O(2)R allows a reduction in ventilator airway pressures without hypercapnia or the complex circuitry and monitoring required for conventional ECMO. Methods AVCO(2)R was applied to a new, clinically relevant large-animal model of se vere respiratory failure created by smoke inhalation and cutaneous flame bu rn injury. Adult sheep (n = 9, 38 +/- 6 kg) received a 40% total body surfa ce area, third-degree cutaneous flame burn and 36 breaths of cotton smoke i nsufflation. After injury, all animals were placed on volume-controlled mec hanical ventilation to achieve PaO2 > 60 mmHg and PaCO2 < 40 mmHg. Animals were placed AVCO(2)R within 40 to 48 hours of injury when the PaO2/FiO(2), was <200. Animals underwent cannulation of the carotid artery and jugular v ein with percutaneous 10F arterial and 14F venous cannulas. Shunt flow was continuously monitored using an ultrasonic flow probe and calculated as a p ercentage of cardiac output. Results AVCO(2)R flows of 800 to 900 ml/min (11% to 13% cardiac output) achieved 77 to 104 ml/min of CO2 removal (95% to 97% total CO2 production) while maint aining normocapnia. Significant reductions in ventilator settings were tida l volume, 421.3 +/- 39.8 to 270.0 +/- 6.3 ml; peak inspiratory pressure, 24 .8 +/- 2.4 to 13.7 +/- 0.7 cm H2O; minute ventilation, 12.7 +/- 1.4 to 6.2 +/- 0.8 L/min; respiratory rate, 25.4 +/- 1.3 to 18.4 +/- 1.8 breaths/min; and FiO(2), 0.88 +/- 0.1 to 0.39 +/- 0.1. The P/F ratio increased from 151. 5 +/- 40.0 at baseline to 320.0 +/- 17.8 after 72 hours. Conclusions Percutaneous AVCO(2)R allows near-total CO2 removal and significant reducti ons in ventilator pressures with improvement in the P/F ratio.