**7. Future directions**

and mortality, and it was not until maturation of the technology and critical care that ECMO could clearly demonstrate benefit to patients. The decision to cannulate a patient and initiate ECMO therapy is viewed as the pinnacle of aggressive modern critical care, and early identification of a decannulation strategy can pose an ethical concern. This is particularly important for patients who are unlikely to recover and will not be a candidate for transplantation. For the patient supported on ECMO for a prolonged duration, the principle ethical concern arises when determining that continuation of ECMO therapy is futile, and this section explores the concept. Indeed, the ethical dilemmas surrounding ECMO may have contributed to the use of ECMO for long-term treatment, as disagreements between the patient's family and treatment

A reported case of a 44-year-old patient who received 37 days of venovenous ECMO for severe *Klebsiella pneumonia* offers an insight into the ethical conundrum facing patients, their family, and the medical team. The case reports that the patient was not a candidate for lung transplant and was treated with long-term venovenous ECMO due to severe respiratory failure. With radiographic signs of irreversible lung damage, the treatment team recommended discontinuation of ECMO. The patient's family would not accept this outcome, however, and despite support from the hospital ethics board to withdraw care, threats of medicolegal action challenged the transition to comfort care. Ultimately, the patient died on day 88 of ECMO after deteriorating with septic shock. This case highlights important guidelines to be established to prevent ethical disagreements with patients and family members. Specifically, the authors suggest that ECMO centers specify (1) guidelines for patient selection, (2) consent process, (3) family engagement and education, (4) protocols for circuit configuration and concomitant care, (5) duration of ECMO therapy, (6) futility, (7) managing impasse, and (8) Quality Assurance [29]. The authors specify that the consent process should include indications for ECMO withdrawal in case of futility and further indicate that venoarterial ECMO of greater than 3 weeks or venovenous ECMO for greater than 3 months should be considered as unusual circumstances. The management of ECMO therapy in patients without a decannulation strategy is further complicated when the patient is awake and an active participant in their care. A case report by Moon et al. presented a 53-year-old patient on venovenous ECMO for acute respiratory failure [30]. After 4 weeks of ECMO treatment, recovery of native lung function appeared unlikely, and a lung transplant was suggested to the patient. The patient refused transplantation due to cost and unspecified personal concerns, however. After discussion with the center's ethics committee, a written do not resuscitate (DNR) was obtained and the plan to forgo further oxygenator changes was agreed upon. After 95 days of ECMO therapy, however, the patient showed signs of radiographic improvement, and he was successfully weaned off ECMO care after 104 days. Due to the novelty of prolonged ECMO therapy, it remains a challenge for physicians to fully define the futility of treatment, as it is unclear which patients will recover on prolonged ECMO treatment. In 2013, a physician survey was conducted to examine the nature of authoritative decisionmaking during venoarterial ECMO care [31]. The purpose of the study was to assess physician attitudes toward the doctor-patient engagement in ECMO therapy versus a medical professional dominated form of decision-making. This survey of 179 physicians concluded that the majority of physicians with experience in administration of venoarterial ECMO are in favor of physicians having authority for decision-making. The majority of the physicians surveyed also

teams can result in prolonged duration of ECMO therapy.

226 Advances in Extra-corporeal Perfusion Therapies

If current trends are indicative of the future, ECMO will continue to be used for long-term respiratory and circulatory support, with the duration of support continuing to increase. Currently, animal studies in ECMO are focusing on high-mobility devices, with the current designs being compact, paracorporeal, and portable. The immediate goal of these devices is to allow the patients to freely ambulate with minimal assistance, with the long-term goal of allowing patients to leave the ICU, and possibly leave the hospital.

Advances in control systems may allow for the development of adaptive ECMO systems, which can automatically modify the blood and sweep gas flows to match the metabolic demands of patients. These devices aim to allow for increased mobility, greater device efficiency (and smaller size), and improved safety. Currently, such devices are in benchtop or animal studies, without incorporation into clinical practice. In one study of six adult pigs placed on venovenous ECMO, a control system was able to maintain automated blood and sweep gas flows over a 6-hour period [32]. Other such reports exist in the literature, and ECMO is ripe for application of advancements in biomedical engineering.

One further area of investigation is the use of novel surface coatings to reduce the need for anticoagulation and improve the biocompatibility of the ECMO circuit. Development in this area will reduce the risk of hemorrhagic and thromboembolic complications associated with ECMO and may prove to reduce immune cell activation and infectious complications as well.
