PEEP Valves in Anesthesia Circuits
Hazard [Health Devices Nov 1983;13(1):24]
ECRI investigated an incident caused by incorrect placement of a positive
end-expiratory pressure (PEEP) valve in the inspiratory limb of an anesthesia circle
system. The combination of the one-way-flow design of the valve and its improper placement
occluded gas flow to the patient and caused serious injury.
PEEP valves are designed to generate positive end-expiratory pressure when
properly oriented in the expiratory limb of the breathing circuit. PEEP acts to improve
ventilation by keeping the patient's airways from collapsing.
PEEP valves may be divided into two groups, depending on whether they
allow gas to flow through them in one direction (unidirectional) or both directions
(bidirectional). Both unidirectional and bidirectional flow PEEP valves will generate PEEP
only with gas flowing through them in the correct direction of gas flow.
Incorrectly orienting a unidirectional flow PEEP valve against the flow of
gas in the inspiratory or expiratory limbs will occlude gas flow, leaving the patient
unventilated. During mechanical ventilation, an occlusion of the expiratory limb may also
build pressure and cause barotrauma.
Incorrectly placing a bidirectional flow PEEP valve against the direction
of either inspiratory or expiratory flow will not occlude the limbs. However, although the
patient will still be ventilated, no PEEP will be generated. If undetected, the lack of
PEEP may seriously jeopardize the ventilation of patients who need it. Incorrect placement
of properly oriented unidirectional or bidirectional flow PEEP valves in the inspiratory
limb will also prevent PEEP from being generated.
All currently available PEEP valve systems are easy to install. However,
since the connectors for the inspiratory and expiratory limbs of breathing circuits are
the same, users may easily insert a PEEP valve in the wrong limb and/or orient it
improperly. Such incorrect placement may seriously or fatally injure the patient.
Users must be well-trained, vigilant, and alerted to the problems
associated with improper placement and orientation of PEEP valves. Until breathing circuit
standards are developed and widely implemented to reduce the chance of user error, the
strong possibility for misconnection of PEEP valves and serious injury to the patient will
continue to exist.
When using PEEP valves in anesthesia circuits, users should use extreme
care to properly connect the valves according to the manufacturer's instructions. The
patient should be rechecked for effective ventilation immediately after the valve is
connected, preferably with a stethoscope.
When using PEEP valves, it is critically important to use a pressure
manometer to monitor the level of PEEP. Never rely on the dial settings of the PEEP valve
to determine the level of PEEP, since many PEEP valves are flow sensitive and require
periodic adjustment. The pressure manometer will indicate if PEEP is present when not
needed (e.g., due to a valve's being left on or not removed from the last case).
Inadvertently giving a patient PEEP when it is not desired, or delivering other than the
desired levels, may result in serious cardiopulmonary complications. Proper monitoring of
PEEP levels will help to prevent this and to identify when PEEP is responsible for a
change in the patient's cardiopulmonary status.
Alarm systems are available that will help sense occlusion of the
inspiratory or expiratory limbs due to an improperly placed PEEP valve. For mechanically
ventilated patients, a low-pressure alarm may sense the occlusion of the inspiratory limb,
while a high-pressure alarm may sense occlusion of the expiratory limb. When using
pressure alarms, it is important that the pressure-sensing line be placed in a position
that accurately reflects the pressure at the patient (see "Low-Pressure Alarms for
Sensing Ventilator Disconnects," Health Devices
12:260-1, July-August 1983).
Spirometer alarms may be used to detect occlusions of the inspiratory or expiratory limbs
for patients who are breathing spontaneously, as well as for those who are being manually
or mechanically ventilated.
- Alert all users of anesthesia circuits to the
hazards associated with PEEP valves. Improperly installed and/or improperly
oriented PEEP valves in the inspiratory and expiratory limbs may result in
their occlusion and/or no PEEP.
- Users should carefully follow the manufacturer's
instructions for proper PEEP valve setup and connection.
- After connecting the valve, immediately recheck for
proper ventilation of the patient, preferably with a stethoscope.
- Use a pressure manometer to monitor the PEEP level.
(Depending on the position of the PEEP valve and the anesthesia unit's
pressure manometer, a second manometer may be needed in the breathing
circuit to properly monitor the PEEP level.)
- With mechanically ventilated patients, use a spirometer alarm and/or a
pressure monitor with a low- and high-pressure alarm that senses the
pressure at the patient to monitor for an occlusion of the inspiratory or
expiratory limb. For spontaneously breathing patients, a spirometer alarm
alone may be used (since a low-pressure alarm will not detect an
- Breathing Circuits, Anesthesia [10-139]
- Valves, Positive End-Expiratory Pressure [14-337]
Cause of Device-Related Incident
Device factor: Design/labeling error
User errors: Device misassembly; Failure to perform pre-use inspection
Support system failure: Lack or failure of incoming and pre-use inspections
Mechanism of Injury or Death