Abstract
A long version of the Bain breathing system is commonly used when remote anaesthesia is required, such as during magnetic resonance imaging or radiotherapy. We compared the static compliance and distal pressures over a range of flows in a 1.6 and 9.6βm Bain system. We examined the effect on ventilation of increasing the length of the Bain system in lung models for 10, 20 and 70βkg patients. We found that static compliance was increased in the long Bain system. We found that with matched peak inspiratory ventilator pressures there was a reduction in peak inspiratory pressures at the patient end with the longer system (pβ<β0.001). A reduction in tidal volume was found with the 9.6βm Bain (pβ<β0.001), and positive endβexpiratory pressure was increased (pβ=β0.01). Although the effect on tidal volume was proportionally small in the 70βkg simulation (660 and 617βml in 1.6 and 9.6βm systems, respectively) it increases in significance in children, with a 23% reduction in tidal volume in the 10βkg mock lung (95 and 73βml in 1.6 and 9.6βm systems, respectively). Anaesthetists should be aware of the reduction in tidal volume and increased positive endβexpiratory pressure. During remote anaesthesia with a long Bain system, the ventilator should be adjusted to compensate.