Hazard [Health Devices Feb-Mar 1986;15(2-3):64-5]

Problem

A member hospital reported that an enteral pump set was inadvertently connected to the cuff inflation tube (pilot tube) of a cuffed endotracheal tube. The female connector of the pilot tube is similar in shape and color to the connector of the feeding tube that was used on the patient. The enteral formula overinflated the endotracheal tube cuff, completely occluding the tracheal tube. The ventilator alarmed, and the patient suffered respiratory arrest. Fortunately, the patient survived. While less likely, similar misconnections are also possible with other tracheal tubes that have a female connector that is compatible with a male Luer connector. For example, IV pumps could also be misconnected to almost any pilot tube.

The style of involved tracheal tubes (both endotracheal and tracheostomy) have a cuff made of polyurethane foam encapsulated in a silicone elastomer balloon. Before inserting the tracheal tube into the trachea, the user deflates the foam by applying vacuum to the pilot tube. After insertion, the user releases the vacuum, and the cuff passively expands to the desired size at atmospheric pressure. This design is intended to prevent tracheal injury caused by cuff overpressurization and eliminate the risk of deflation associated with inflatable cuff designs. Although it is not intended to be an inflatable cuff, the foam encapsulated cuffs will expand well beyond their normal size when overpressurized. The pressure generated by any enteral feeding pump is sufficient to overinflate such cuffs.

The no-flow alarm systems on currently available enteral pumps will not detect a misconnection to a tracheal tube cuff as long as the cuff can expand. Depending on its elasticity, the cuff could expand enough to occlude the patient's airway or burst before an enteral pump would alarm. Similarly, many IV pumps probably would not alarm soon enough to avoid patient injury.

For mechanically ventilated patients, the ventilator's high-pressure or low-exhaled-volume alarm should detect airway occlusion caused by an overinflated cuff, but only if its limits are set correctly. An overinflated cuff can also impede exhalation, resulting in dangerously high peak-inspiratory and end-expiratory pressures, which can cause severe cardiopulmonary complications. Intubated patients that are not mechanically ventilated, and therefore are not protected by ventilator alarms, would most likely suffocate if the cuff were sufficiently overinflated to occlude the airway.

In this incident, the male connector on the enteral pump set and the female connector on the cuff pilot tube were both red. Although the female connector on the feeding tube is pink, it appears almost identical to the female connector on the endotracheal tube. Therefore, it is possible to mistake the pilot tube connector for the feeding tube connector. Also, because the pilot tube is usually not capped, it invites the insertion of a compatible male connector, especially when the connectors happen to be the same color. Unfortunately, no color coding standards exist to help prevent misconnections.

We believe that misconnections of enteral and IV solution delivery sets to pilot tube connectors of other tracheal tubes may be nearly as likely as the specific incident described because all of these connectors are Luer compatible. Syringes with Luer connectors are necessary to irrigate feeding tubes, administer enteral formula, inflate tracheal tube cuffs, and access the bloodstream. For this reason, the connectors of these fluid delivery products are manufactured to be compatible with the male Luer connector of the syringes. Thus, most parenteral or enteral administration sets can be connected to most IV, enteral, tracheal tube, or urinary catheters. In one case, an enteral administration set was misconnected to an IV catheter, resulting in the patient's death.

We believe that manufacturers have been slow in developing connectors and that standards committees have been slow in developing related standards for parenteral, enteral, urinary, and respiratory products that would make these connectors incompatible with one another but compatible with a tapered Luer. Considering the huge investment in manufacturing parenteral products and the growing investment in manufacturing enteral products, we believe that design efforts to ensure protective incompatibility between parenteral and enteral products should be given high priority by manufacturers.

Undoubtedly, the burden is on the user to trace every fluid delivery line, whether gas or liquid, from the patient to its respective source to prevent misconnections. However, we believe that the existing connector compatibility invites human error.

1. Alert users to the risk of misconnecting a pump set (e.g., enteral or IV) to the inflation tube of a tracheal tube cuff or any other Luer receiver.
2. Whenever possible, position catheters, feeding tubes, and pilot tubes exiting from the patient on different sides of the patient's body. Position the respective delivery system on the same side of the patient from which the catheter exits.
3. Always trace fluid delivery lines from their respective sources before making connections.
4. When the possibility for misconnection exists, affix labels to the catheters and administration sets.
5. Always properly adjust ventilator alarm limits.
6. Encourage manufacturers to supply these products with connectors that cannot be misconnected.

UMDNS Terms

• Cuffs, Tracheal Tube [14-082]
• Cuffs, Tracheostomy Tube [14-094]
• Enteral Feeding Kits [11-677]
• Tubes, Feeding [14-199]
• Tubes, Tracheal [14-085]
• Tubes, Tracheostomy [14-096]

Device factors: Design/labeling error; Device interaction 

User error: Accidental misconnection

Suffocation