To the Editor:—
Recently, a 44-yr-old woman came to the operating room for the resection of a liver mass. After induction of general anesthesia, her trachea was intubated, and the patient was placed on mechanical ventilation using a previously checked Draeger Fabius GS anesthesia machine (Draeger Medical Inc., Telford, PA). There were no problems with mechanical ventilation. Approximately 10 min later, the mechanical ventilator stopped working, and the anesthesia machine monitor display reported a ventilator failure. We continued to ventilate the patient using manual ventilation.
In looking for the cause of the ventilator failure, we found a plastic cap lodged under the lower rim of the mechanical ventilator piston (fig. 1). Although it is possible for this cap to have entered the ventilator housing before the start of the case, we hypothesize that the cap rolled under the lower rim sometime after the institution of mechanical ventilation.
The Draeger Fabius GS anesthesia machine mechanical ventilator is housed within a see-through compartment that can be opened by simply swinging it out. This creates an entry route for objects to fall into the ventilator compartment. The ventilator operates using a piston driven by a motor and ball-screw arrangement. A light-activated position sensor on the ventilator signals the control board when the piston has reached its lower limit. When this does not occur, the zeroing position is invalid, and the ventilator will not work. This is known as error code V002 in the Draeger Fabius GS reporting nomenclature.
There is no mechanism to lock the ventilator compartment in the closed position. Furthermore, the auxiliary oxygen source is mounted on the swing-out door. Therefore, the compartment is easily opened under a variety circumstances, such as pulling on oxygen tubing connected to the auxiliary source.
Small objects, particularly plastic caps, are ubiquitous in the operating room. The upper shelf edge in the Draeger Fabius GS lies just above the opening created when the ventilator compartment is swung out. One can easily envision how small objects can find their way into this chamber. After discussing the case with our biomedical engineers, they reported that they have previously retrieved a few small objects from these ventilator compartments.
Considering the importance of mechanical ventilation in an anesthesia machine, equipment manufacturers must find a way to prevent these incidents. It is ironic that such an expensive and vital piece of equipment can be totally disabled by a simple plastic cap.
*Boston University Medical Center, Boston, Massachusetts. firstname.lastname@example.org