Sudden Development of Anesthesia Circuit Obstruction by an End-Tidal CO2 Cap in the Gas Sampling Elbow

Abstract

To the Editor: An ASA physical status I patient presented to the operating suite for arthroscopic surgery of the knee. An anesthesia system check was performed just prior to patient arrival. Monitors were applied and preoxygenation began, followed by intravenous induction. Hand and bag mask ventilation began normally in the now apneic patient but after a few breaths became impossible. Attempts to improve mask ventilation were to no avail. The anesthetist proceeded to intubate the trachea via direct laryngoscopy with ease and was certain of proper tube placement. Attempts to ventilate the patient via the endotracheal tube were also impossible. At this time the author was summoned for assistance. Chest auscultation revealed wheezing bilaterally and markedly diminished breath sounds. An end-tidal CO2 waveform was present but severely dampened. An attempt to ventilate the patient via bag compression was met with extreme resistance. A quick glance at the anesthesia circuit revealed the problem. A small, white, circular cap that attaches to the gas sampling port was inside the elbow that connects to the "Y" portion of the corrugated tubing Figure 1. This caused virtually complete obstruction. The problem was rectified in a timely manner without the patient experiencing adverse reactions or changes in vital signs, oxygen saturation, etc.Figure 1: A small, white, circular cap attached to the gas sampling port and inside the elbow that connects to the "Y" portion of the corrugated tubing.We believe that, when positive-pressure bag mask ventilation began, the cap was initially inside the "Y" portion of the corrugated circuit, allowing normal function, and then migrated into the elbow, causing obstruction. If hand pressure had been on the bag when the face mask was removed from the patient prior to intubation, the failure to deflate would have heralded that the anesthesia system was now suddenly faulty. We believe that the cap was present in the circuit as received from the manufacturer and not somehow placed into the circuit errantly at our facility. The circuits are supplied as single-use disposable units in a sealed plastic bag and installed by anesthesia technicians at our hospital. Correspondence with the manufacturer (Intertech Mfg., Ft. Myers, FL) revealed this to be the first reported incident of this mechanism of obstruction. We conclude that one can never be too thorough when inspecting and testing the anesthesia system. Dismantling the elbow from the corrugated circuit should be performed routinely and an internal visual check of the lumen performed because the opaque nature of the circuit makes visual identification of debris difficult when examined externally. In the event that a similar occurrence is experienced, we suggest that hand pressure be applied to the bag and expose the distal end of the circuit to room atmospheric pressure. This would rapidly give a clue as to whether the problem was with the patient or with the anesthesia system. A manual resuscitator should always be available while administering anesthesia in the event of such occurrences, and the problem is not readily identified or easily correctable. This case was unusual in that the obstruction developed suddenly and completely after normal checkout and functioning and at a most inopportune time. Thaddeus J. Krensavage, DO Edward Richards, CRNA Department of Anesthesia, Morton Hospital, Taunton, MA 02780