The long Bain breathing system: an investigation into the implications of remote ventilation.

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 9.6 m Bain system. We examined the effect on ventilation of increasing the length of the Bain system in lung models for 10, 20 and 70 kg 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 (p < 0.001). A reduction in tidal volume was found with the 9.6 m Bain (p < 0.001), and positive end-expiratory pressure was increased (p = 0.01). Although the effect on tidal volume was proportionally small in the 70 kg simulation (660 and 617 ml in 1.6 and 9.6 m systems, respectively) it increases in significance in children, with a 23% reduction in tidal volume in the 10 kg mock lung (95 and 73 ml in 1.6 and 9.6 m systems, respectively). Anaesthetists should be aware of the reduction in tidal volume and increased positive end-expiratory pressure. During remote anaesthesia with a long Bain system, the ventilator should be adjusted to compensate.