Sir,
The detection of faulty parts in anesthesia machine may be during routine check-up or accidental. Discs in the unidirectional valves are hydrophobic to reduce water absorption and sticking. Sticking of valves does exist. It is important to note the free movement of disc while squeezing the bag with patient end closed position, failing of which will result in rebreathing of expired gases without carbon dioxide removal. We report an accidental detection of sticky, damaged, and malpositioned disc of unidirectional expiratory valve, which could have led to disastrous hypercarbia by rebreathing and further catastrophe in patient.
The 2008 anesthesia apparatus checkout recommendation, recommends that 15 separate items should be checked or verified at the beginning of each day or whenever a machine is moved, serviced or the vaporizers changed. Eight of these items should be checked prior to each procedure. Some of these steps may be part of an automated checkout process on many machines. Following these check-lists will typically require <5 min at the beginning of the day, and <2 min between cases, but will provide us the confidence that the machine will be able to provide all essential life support functions before we begin a case.
Different problems are noted previously in relation to expiratory valve and its components. Author describes patient developing bilateral pneumothorax due to misplaced expiratory valve.[1] Testing of valve competence in circle system involves, visual inspection of movement i.e., opening and closing fully.
We could early recognize the damaged part of the expiratory valve as shown in Figures 1 and 2 and could avoid hazard caused by it. Usually, the malfunction of the expiratory valve is detected through the spirometer with reverse flow detection as it will alarm when gas flows in reverse in the expiratory limb. The end tidal carbon dioxide monitoring is also important as it shows elevated carbon dioxide baseline as a large volume of exhaled gas will return to the patient. In our workstation, we could not recognize what is the exact cause for the damage and misplaced valve disc. The probable cause could be manual error by the technician; by improper placement of disc within the valve and closing it after cleaning.
Figure 1.
Unidirectional valves in circle system
Figure 2.
Damaged expiratory valve
Mishaps related to faulty technique, machine dysfunction, device failures may lead to increased morbidity and mortality. Hence, one should never miss anesthesia machine check, maintaining machine standards, reverse flow alarm system for flow sensors must considered.[2]
The key message is to make readers alert while checking the machine, not to miss the unidirectional valves. The anesthesiologist is responsible for ensuring that the machine used for anesthesia is in a safe condition before the start. I hope reporting such errors will help in improvising the quality control during the manufacturing of anesthesia products, and will contribute for retrospective studies related to malfunctioning or damaged part of anesthesia workstation.
REFERENCES
- 1.Dean HN, Parsons DE, Raphaely RC. Bilateral tension pneumothorax from mechanical failure of anesthesia machine due to misplaced expiratory valve. Anesth Analg. 1971;50:195–8. [PubMed] [Google Scholar]
- 2.Vasudevan A, Parida S, Elakkumanan LB, Mishra S. Carbon dioxide rebreathing caused by deformed silicon leaflet in the expiratory unidirectional valve. J Anaesthesiol Clin Pharmacol. 2013;29:108–10. doi: 10.4103/0970-9185.105816. [DOI] [PMC free article] [PubMed] [Google Scholar]
