Ultra-protective and independent lung ventilation enabled by minimally invasive extracorporeal carbon dioxide removal: A case report
Vito Fanelli, MD
University Hospital of Molinette San Giovanni Battista of Torino, Italy
This report describes a unique case of a difficult-to-ventilate patient with severe drug poisoning resulting in coma and aspiration pneumonia of the right lung. There was a large difference between the size and compliance of the right versus left lung due to a prior right lung transplant for underlying fibroelastosis, resulting in significant ventilation and perfusion mismatch. Low-flow extracorporeal CO2 removal (ECCO2R) with the Hemolung Respiratory Assist System (RAS) was used successfully to enable both independent and ultra-protective lung ventilation.
A 42 year old female was brought to the emergency department in respiratory failure with a Glasgow Coma score of 3 resulting from a drug overdose. Ten years prior to this incident, the patient had received a monolateral right lung transplant due to fibroelastosis, a disease of the connective tissue that progressively enlarges airways with increasing dead space fraction and development of respiratory failure. The patient was intubated in the emergency department and transferred to the ICU the next day with a diagnosis of coma and aspiration pneumonia in the transplanted right lung.
The patient improved on wide spectrum antibiotics and was extubated to noninvasive ventilation on the fourth day. However, on day 13, the pneumonia suddenly worsened with complete right side involvement, requiring emergent reintubation. Shortly after intubation, the patient developed severe respiratory acidosis with an arterial PCO2 of 121 mmHg and a pH of 7.14, reflecting differing respiratory mechanics between the left and right lung and significant mismatch of ventilation and perfusion. The right lung displayed very low compliance due to the pneumonia, with high perfusion and low ventilation. In contrast, the native left lung had a higher compliance, but represented primarily dead space due to higher ventilation and lower perfusion associated with the underlying connective tissue disease as shown in Figure 1.
In order to control the respiratory acidosis and to immediately implement lung-protective ventilation, low-flow ECCO2R with the Hemolung RAS was initiated. A Hemolung 15.5 Fr dual-lumen catheter was placed in the left femoral vein. ECCO2R therapy was initiated with a blood flow of 400 mL/min at a pump speed of 1400 RPM, and a CO2 removal rate of 80 mL/min at a sweep gas flow of 7.2 L/min. The delta between the baseline arterial PCO2 and the end tidal CO2 was monitored in lieu of continuous ABGs to avoid any abrupt change in PCO2 and to identify the point of stabilization. Within one hour of Hemolung initiation, arterial PCO2 was reduced to 53 mmHg and pH had increased to 7.41.
A subsequent chest x-ray confirmed significant difference in lung size and ventilation/perfusion mismatch which can be seen in Figure 2. Based on this observation and on worsening PO2, independent lung ventilation was implemented with a dual lumen endotracheal tube to recruit the right lung for better oxygenation without causing further damage to the left. Ultra-protective ventilation was applied with low tidal volumes (250 mL for the left lung and 200 mL for the right lung) and a very low respiratory rate of 6–8 breaths per minute. On the left side, a PEEP of 0 mmHg was used whereas on the right side, which was most affected by the pneumonia, a PEEP of 10 mmHg was applied for greater recruitment.
This was a patient who was very difficult to ventilate, and the use of minimally invasive partial ECCO2R enabled the successful application of both independent and ultraprotective lung ventilation, thus minimizing the risk of ventilator induced lung injury. Hemolung therapy was applied for 7 days during which control of arterial PCO2 and pH was effectively maintained. The rate of CO2 removal throughout therapy, which is measured and displayed by the Hemolung controller, ranged from 70–80 mL/min at blood flows of 400–460 mL/min.
On day 21, the patient was fully weaned from Hemolung therapy after which she was returned to conventional ventilation and tracheostomized due to malnutrition, chronic steroids, and length of time in the ICU. On day 26, she was discharged to a respiratory medicine ward, and one week later to a long term facility requiring only nocturnal ventilation.
Discussion with Dr. Fanelli
Q: At any point during therapy, did the patient experience severe hypoxia?
A: Yes, prior to the application of independent ventilation, the patient was at the edge of requiring extracorporeal membrane oxygenation (ECMO). She had a very low PO2 of 60 mmHg on an FiO2 of 0.6. However, this patient had previously experienced chronic hypoxia because the native left lung did not provide much oxygenation due to the underlying disease. We started with the Hemolung RAS as opposed to ECMO because the predominant problem at the time was severe respiratory acidosis. When the patient became more severely hypoxic, we were able to recruit the right lung using independent ventilation, resulting in improved oxygenation and allowing continuation with the Hemolung RAS and ultra-protective ventilation.
Q: Why was partial CO2 removal with the Hemolung used instead of ECMO?
A: We prefer to provide therapy in an escalating manner, meaning that as a patient’s condition progressively worsens, increasingly higher risk therapies are utilized. For this patient, we wanted to go with the least risky system needed for the predominant problem of respiratory acidosis. We felt this could be
best managed with the low-flow Hemolung device, which by definition, is less invasive than the alternative of ECMO. We realized we could work on recruitment of the right lung to improve oxygenation thus avoiding hyperinflation of left lung. If we had been unable to recruit the right lung and improve oxygenation, ECMO would have then been utilized. We feel that if there is space to improve oxygenation in a timely manner, a less invasive system can be applied, but we are prepared to apply ECMO if needed.
Q: Did the patient experience any complications associated with Hemolung therapy?
A: She had pleural effusion on the right side that was related to the pneumonia with some hemothorax during Hemolung therapy due to anticoagulation. We treated this with a chest tube. We use a standardized protocol for anticoagulation to maintain a target aPTT in the range of 1.5 to 2.4 times baseline. When we observe minor bleeding during extracorporeal therapy, such as with this patient, we try to stay towards the lower end of the target aPTT range.
Q: How was the Hemolung system perceived in your ICU?
A: A common observation among the nurses who operated the Hemolung RAS was that it was very consistent in its performance. One expression that we heard was that one could “start it and forget it”.
About the Author
Dr. Vito Fanelli is an assistant professor at the University Hospital of Molinette San Giovanni Battista in Torino Italy. He received no compensation in association with this case report and has no conflicts of interest to disclose. Dr. Fanelli can be reached via email at firstname.lastname@example.org.
About the Hemolung RAS
The Hemolung RAS from ALung Technologies provides Respiratory Dialysis®, a simple, minimally-invasive form of extracorporeal carbon dioxide removal (ECCO2R). The system utilizes patented technology to provide highly efficient CO2 removal at dialysis-like blood flow rates which are achieved through a single 15.5 Fr venous catheter. For more information, please visit https://www.alung.com/products/hemolung-ras/
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