# Management of Acute Life-Threatening Asthma Exacerbations in the Intensive Care Unit
## 4 Acute Life-Threatening Asthma Advanced Management in the ICU
### Ecmo  
Extracorporeal membrane oxygenation (ECMO) is an invasive supportive treatment used in critical care for several respiratory pathologies refractory to standard intensive clinical practices (including pneumonia, ARDS, pulmonary embolism, and trauma) [112]. The various mechanisms by which ECMO can provide organ support depend upon its configuration. Blood extracted from a central vein passes through an oxygenator, which extracts carbon dioxide whilst saturating the blood with oxygen. The blood then passes back to the body via the same or different central vein (V-V-ECMO). V-V ECMO provides respiratory support by essentially bypassing the lungs; however, it necessitates a stable functioning circulatory system. An alternative configuration is to return the blood at higher pressures directly to the arterial circulation (V-A-ECMO), thus bypassing both the heart and lungs, providing cardiovascular and respiratory support [113; 114]. The physiological benefits of ECMO during acute respiratory failure are to provide sufficient gas exchange whilst preventing ventilator-induced lung injury, reduce metabolic demand of breathing, and provide a means of lung \"ultra-protection\" with the use of low tidal volumes and prevention of atelectasis and barotrauma [115]. Furthermore, patients on ECMO can better tolerate more invasive airway clearance manoeuvres, such as bronchoscopy and bronchial washes, reducing the incidence of mucus plugging [116]. Following the CESAR trial in 2009 and the recent COVID-19 pandemic, the global utilisation of ECMO has expanded greatly, and in the UK, ECMO is only delivered by dedicated specialist centres. The CESAR results demonstrated a relative risk of survival to 6 months without disability when ECMO was used on adults with severe, potentially reversible respiratory failure compared to standard therapy alone [117]. An important confounder in this study was that there was demonstrable improved success in patients admitted directly to ECMO centres versus those who had to be transferred to them, highlighting the importance of earlier intervention for those who require it. Delivery without complications, however, require both specialist equipment and staff; therefore, expansion without appreciation for this may in fact worsen outcomes [118; 119]. In asthma refractory to standard intensive therapy (near-fatal asthma or status asthmatics), ECMO may help to improve gas exchange without the expense of aggressive IMV. Data from the extra corporeal life support organisation registry from 1992 to 2016 demonstrated that in 272 patients with life threatening asthma, the survival rate to hospital discharge was 83.5%, with improvements in the fraction of inspired oxygen, peak inspiratory pressures, driving pressures, and mean airway pressure following the initiation of ECMO [120]. Additionally, an analysis of 1205 patients in the UK who required ECMO demonstrated an overall survival rate 74%, but near-fatal asthma as an indication for ECMO (10%) was associated with a survival rate of 95% compared to 71% for other respiratory pathologies. Additionally, younger patients and those with better oxygenation at the point of ECMO initiation were more likely to survive [121]. The most frequently observed complications of ECMO are mainly related to cannulation and include bleeding/thrombosis and infection. The rate of complication determined by [PERSON] et al. (2017) was 65.1%, with haemorrhage at 28.3%, but this resulted in very few deaths; however, bleeding was an independent risk factor for in-hospital mortality [120]. More conservative anticoagulation may reduce the incidence of this complication [122]. However, treading the line between bleeding and clotting is difficult in critical care, and the use of ECMO can make this even more challenging. Clinicians must evaluate clotting/bleeding risk both at initiation and throughout ECMO delivery. Despite the survival benefit demonstrated above and in numerous case reports [123; 124; 125; 126], high-quality comparative data to support ECMO use is limited.