A modification to the Maquet Flow-i anaesthesia machine for ICU ventilation

Andrew J Robinson; William London; Lazslo Kotan; Warwick Downing

Total Loss undesirable long-term with HME alone. In order to avoid the circuit rainout issue, the machine could be used in high flow modeand used as a total loss system like an ICU ventilator by setting the Fresh Gas Flow (FGF) above Minute Volume and thus allowing all unused air, oxygen, and carbon dioxide from cellular respiration to be vented to atmosphere or AGS. This renders the HME more efficient in heating, but less so for humidification. Reduced humidification risks drying patient mucosa, ciliary damage, thickened secretions, atelectasis (Branson, 2009) , risks of poorer outcomes (Misset et al., 1991) , and a higher incidence of artificial airway blockage. While a Cochrane review of the available literature suggests there is not a major difference in ICU outcomes between HME and active humidification, it did so with the caveat "HMEs may not be suitable for patients with limited respiratory reserve or prone to airway blockage" (Kelly et al., 2010) , something which certainly pertains in the COVID-19 ARDS cohort of patients. Our ICU uses Fisher & Paykel (F&P) active humidification for patients ventilated for longer than 24 hours, so the HME alone option was considered undesirable.