title: Performance of adjustable pressure-limiting (APL) valves in two different modern anaesthesia machines.
abstract: The ability to gently ventilate a patient's lungs using a self-inflating bag requires a properly working adjustable pressure-limiting (APL) valve. We compared the performance of the APL valves of the GE Aisys CS2and the Draeger Fabius anaesthetic machines during closure and opening from 1-20 and from 20-1 cmH2O, using standardised experimental baby and adolescent patient lung models. Airway pressures and inspiratory tidal volumes were measured using an ASL-5000 test lung and a GE Aisys CS2near-patient spirometry sensors. In both lung models, the GE Aisys CS2APL valves demonstrated non-linear behaviours for airway pressures and for inspiratory tidal volumes, with a sharp increase at set APL pressure levels of 8-10 cmH2O. With further closure of the GE Aisys CS2APL valves up to 20 cmH2O, inspiratory tidal volumes decreased to ~50% of the highest values measured. Airway pressures in the Draeger Fabius APL valves demonstrated a near linear increase and decrease. Airway pressure values measured in the Draeger Fabius were never higher than those set by the APL valves, whereas in the GE Aisys CS2, they considerably exceeded set pressures (by up to 27 cmH2O). We conclude that the performance of the GE Aisys CS2APL valve does not allow safe bag-assisted ventilation of a patient's lungs.
authors.affiliation: Department of Anaesthesia and Children's Research Centre, University Children's Hospital, Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Thomas
authors.affiliation: Department of Anaesthesia and Children's Research Centre, University Children's Hospital, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Weiss
authors.affiliation: Department of Anaesthesia and Children's Research Centre, University Children's Hospital, Zurich, Switzerland.
authors.forename: A R
authors.initials: AR
authors.lastname: Schmidt
authors.affiliation: Department of Anaesthesia and Children's Research Centre, University Children's Hospital, Zurich, Switzerland.
authors.forename: P K
authors.initials: PK
authors.lastname: Buehler
mesh_terms: D000399:Air Pressure; D000769:Anesthesia, Inhalation / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial / Q000295:instrumentation*; D013147:Spirometry / Q000379:methods; D013990:Tidal Volume / Q000502:physiology
keywords: adjustable pressure limiting valve; equipment; ventilation