Mechanical errors in oxygen humidifier.

Sir,

Anesthesia machine check is an essential component in routine anesthesia practice. As the anesthesia work stations developed the safety features are also developed. For a wide range of anesthesia machines recommendations of Association of Anesthetists of Great Britain and Ireland (AAGBI) 2012 are used.[1] The detection of the faulty parts or non-functioning part is not uncommon. Auxillary oxygen is also a component of anesthesia workstation.

As per the ASA recommendations for pre-anesthesia checkout procedure, the responsible party would fall into 1 of 4 categories i.e. anesthesia provider, technician, technician or provider, or technician and provider.[2] Irrespective of the party ultimate sufferer is “patient”. Here, we report how a technician made an error which could have led to fault in supplementing humidified oxygen. We could identify the problem and prevent unacceptable disaster due to proper machine check.

Scenario 1

The Figure 1 shows the placement of the inner calibrated tube of humidified oxygen assembly in a reverse way. When we tried to adjust the oxygen flow the bobbin was not moving and with the close look we could find this gross mistake. The technician did open for some reason and did not place it in a correct way. We could see bubbles nicely but couldn’t adjust the desired flow. The bobbin was placed at the narrowest part of the tube and got fixed.

Figure 1

Reversed inner tube

Scenario 2

The Figure 2 shows the connection between humidified oxygen and the entry port of the flow meter is missing. There are high chances that anyone can just put the mask and adjust the oxygen flow. Since the bobbin moves as the oxygen enters the inner tube one thinks that the assembly is functioning well. Since the connection between flow meter and humidifying chamber is lost, the oxygen will not be delivered to the patient.

Figure 2

Loss of connection between the flow meter and humidifier

The key message is to make readers alert about checking the flow meter is properly attached, and the inner tube correctly placed if opened for servicing, bobbin is properly moving, presence of adequate distilled water and proper connection is important to avoid morbidity or mortality. It is important to have high index of suspicion in improper oxygen delivery whenever the patient says that difficulty in breathing or suffocating, fall in saturation, and appearance of fog in the mask [Figure 3].

Figure 3

Fog in simple mask

Many a times it happens especially newly joined residents in anesthesia department, may place the mask on patient without starting oxygen or removed and forget to stop oxygen leading to wastage of gas. In our institution, the protocol is to start and adjust desired oxygen flow first then put the mask and while removing, it is to taking off the mask first then to stop flows. This technique prevents correct starting and stopping of oxygen. The auxillary oxygen supply should be included in anesthesia machine check.