Lack Co-Axial Breathing System

The MIE Lack circuit was the first and original Lack breathing circuit designed and developed by Dr Alastair Lack and Bill Quick of MIE.

The Lack Co-Axial Circuit was designed to overcome the problems of inaccessibility of the expiratory valve at the patient end of the circuit. The fresh gases are led to the patient via the outer channel of the two concentric tubes, while expired gases return along the inner tube to be discharged outside the theatre via the MIE Exhaust valve.

It offers distinct advantages over the Mapleson 'A' or Magill Circuit. A Mapleson 'A' or Magill Circuit are highly efficient providing a fresh gas flow requirements theoretically equal to a little more than the alveolar ventilation, i.e. 4-5 litre/min for a 70Kg adult. Their principal disadvantages however are that the expiratory valve is located at the patient end of the circuit, so being inaccessible to the anaesthetist and adding undesirable weight near the point of connection to the patient.

The reservior bag is in the fresh gas line as in the Mapleson 'A' circuit (in contrast to the Mapleson 'D' and Bain Circuits where reservior bags are placed in the expired line which considerably reduces efficiency with spontaneous respiration).

The dead space of the MIE Lack Co-Axial circuit with a 15mm male catheter in place is approximately 4cc and the MIE Exhaust Expiratory Valve has a minimal expiratory resistance so making the circuit suitable for all but small babies.