Reduced Ventilator Pressure and Improved P/F Ratio During Percutaneous Arteriovenous Carbon Dioxide Removal for Severe Respiratory Failure

Abstract

ObjectiveTo 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 DataAVCO 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 CO 2 removal. With an AV shunt 10% to 15% of cardiac output, AVCO 2 R allows a reduction in ventilator airway pressures without hypercapnia or the complex circuitry and monitoring required for conventional ECMO. MethodsAVCO 2 R was applied to a new, clinically relevant large-animal model of severe respiratory failure created by smoke inhalation and cutaneous flame burn injury. Adult sheep (n ϭ 9, 38 Ϯ 6 kg) received a 40% total body surface area, third-degree cutaneous flame burn and 36 breaths of cotton smoke insufflation. After injury, all animals were placed on volumecontrolled mechanical ventilation to achieve PaO 2 Ͼ 60 mmHg and PaCO 2 Ͻ 40 mmHg. Animals were placed on AVCO 2 R within 40 to 48 hours of injury when the PaO 2 /FiO 2 was Ͻ200. Animals underwent cannulation of the carotid artery and jugular vein with percutaneous 10F arterial and 14F venous cannulas. Shunt flow was continuously monitored using an ultrasonic flow probe and calculated as a percentage of cardiac output. ResultsAVCO 2 R flows of 800 to 900 ml/min (11% to 13% cardiac output) achieved 77 to 104 ml/min of CO 2 removal (95% to 97% total CO 2 production) while maintaining normocapnia. Significant reductions in ventilator settings were tidal volume, 421.3 Ϯ 39.8 to 270.0 Ϯ 6.3 ml; peak inspiratory pressure, 24.8 Ϯ 2.4 to 13.7 Ϯ 0.7 cm H 2 O; minute ventilation, 12.7 Ϯ 1.4 to 6.2 Ϯ 0.8 L/min; respiratory rate, 25.4 Ϯ 1.3 to 18.4 Ϯ 1.8 breaths/min; and FiO 2 , 0.88 Ϯ 0.1 to 0.39 Ϯ 0.1. The P/F ratio increased from 151.5 Ϯ 40.0 at baseline to 320.0 Ϯ 17.8 after 72 hours. ConclusionsPercutaneous AVCO 2 R allows near-total CO 2 removal and significant reductions in ventilator pressures with improvement in the P/F ratio.

Total extracorporeal arteriovenous carbon dioxide removal in acute respiratory failure: a phase I clinical study

“…The limits of blood flow predicted by mathematical modeling were confirmed in experimental studies by Brunston et al [11]. Large animal studies confirmed that AVCO 2 R can transfer sufficient quantities of carbon dioxide to impact ventilatory support [14,15].…”

“…Pumpless arteriovenous CO 2 removal (AVCO 2 R) using percutaneous cannulation is an alternative to traditional pumped extracorporeal systems. We have previously demonstrated in both mathematical and animal models that AVCO 2 R can remove clinically significant amounts of carbon dioxide [11,12,13] and permit significant reduction in ventilatory volumes and pressures [14,15,16]. Mathematical modeling has suggested that total carbon dioxide removal in humans is possible with the use of physiologically tolerable arteriovenous blood flow and the existing gas exchange capabilities of currently available membrane oxygenators [13].…”

Ovine Smoke/Burn ARDS Model: A New Ventilator-Controlled Smoke Delivery System

“…Alpard et al [17] developed a clinically relevant, smoke/burn ovine model of respiratory failure which has been utilized for more than a decade [18][19][20] in our large animal research lab. This model utilized a ''three hit'' injury consisting of a 40% flank burn, smoke inhalation, and barotrauma from high tidal volume ventilation to develop a clinically relevant model of severe human ARDS.…”

Arterio-Venous CO 2 Removal (AVCO 2 R) Perioperative Management: Rapid Recovery and Enhanced Survival

“…At 48 h, AVCO 2 R allowed signi cant reductions compared to time off onset of ARDS entry criteria (PaO 2 /FiO 2 ratio 200) in minute ventilation (12.4 § 1.5 to 6.5 § 0.6 L/min), tidal volume (398.8 § 42.1 to 274.0 § 7.5 mL), peak inspiratory pressure (23.4 § 2.9 to 18.8 § 0.8 cm H 2 O), respiratory rate (RR; 24.0 § 1.7 to 17.0 § 2.0 breaths/min), and FiO 2 (0.88 to 0.35 § 0.1) while normocapnia was maintained. The PaO 2 /FiO 2 ratio improved from 151.5 § 40.0 at the introduction of AVCO 2 R to >200 over 36 h with further improvement to >300 (320.0 § 17.8) by 72 h [9]. Animals were weaned from AVCO 2 R beginning…”