Cause of Device-Related Incident
Device factors; Support system failures; User errors

Clinical Specialty or Hospital Department
Anesthesia; Pulmonary / Respiratory Therapy

Device Factors
Design / labeling error

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Barotrauma; Suffocation

Support System Failures
Lack or failure of incoming and pre-use inspections

Tampering and/or Sabotage
*Not stated

User Errors
Device misassembly; Failure to perform pre-use inspection

UMDNS
Breathing Circuits, Anesthesia [10-139]; Valves, Positive End-Expiratory Pressure [14-337]

PEEP Valves in Anesthesia Circuits



Hazard [Health Devices Nov 1983;13(1):24]

Problem

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.

Discussion

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.

Recommendations

  1. 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.
  2. Users should carefully follow the manufacturer's instructions for proper PEEP valve setup and connection.
  3. After connecting the valve, immediately recheck for proper ventilation of the patient, preferably with a stethoscope.
  4. 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.)
  5. 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 occlusion).

UMDNS Terms

  • 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

Barotrauma; Suffocation


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