A reversibly operable motor is mechanically connected to automatically position the piston (27) of an air syringe (26) that is pneumatically connected to the inflatable/deflatable seal ring or cuff (19) of a laryngeal mask airway device (LMA) (12) that is installed in a patient, who is being ventilated and/or anaesthetized via the airway of the LMA device (12). Ideally, (i) the air at the head end of the syringe (26), plus (ii) the air contained in the inflatable cuff (19) of the LMA (12), plus (iii) the air contained in their interconnection, is a 'substantially constant' volume which is shared at these three locations but which is automatically shifted by piston (27) displacement, such that air pressure in the substantially constant volume is caused to correct as necessary for conformance to a predetermined level of set-point pressure. Various instrumentalities (10), including microprocessor-controlled instrumentalities, continuously monitor patterns of system response to observed pattern abnormality, with audibly and visually reported warnings to the anaesthetist.
