Equipment Friday again 🙂
BT_SQ 1.12 Describe the principles and safe operation of vaporisers
TRUE/FALSE The Aladin cassette vaporiser is an example of an injection vaporiser system
TRUE/FALSE Modern vaporisers use an electrical heating coil to compensate for the cooling caused by latent heat of vaporisation
TRUE/FALSE A plenum vaporiser is designed so that the gas leaving the bypass is fully saturated under normal conditions
TRUE/FALSE Thymol in sevoflurane can cause the bimetalic strip of older vaporisers to stick
TRUE/FALSE The Quick-Fill system is used only for sevoflurane
Here is a picture of a cut open Vapor 2000. See if you can identify the features shown in the picture in Dorsch & Dorsch.
The vaporisers you are used to are out of circuit with a high internal resistance. If the internal resistance is high, what is the driving pressure to force the gas through them?
How can you use a vaporiser in an area which doesn’t have a pressurised gas supply? What kind of circuit would you use?
(You should know how to answer the above questions, but the following is provided for interest rather than examination purposes)
This is an example of a drawover vaporiser. The patients’ respiratory effort draws the fresh gas through the device. These vaporisers must therefore have a low internal resistance.
If you don’t have bulk gas supply, you can’t use a circle or Mapleson style circuit. The attached circuit uses an ‘Ambu’ style non rebreathing valve. The gas is drawn in through an inlet on the other side of the vaporiser, and is vented at the valve attached to the mask.
The mask is called an Everseal, and designed for prolonged mask holding. The bottom of the mask lifts up the chin to help maintain an open airway.
What would you do if you need to ventilate them? You could always use a self inflating resuscitation bag, but then it is difficult to see if the patient is breathing spontaneously.
Below is a picture of an Oxford Inflating Bellows. It can be used to hand ventilate a patient in conjunction with a drawover vaporiser. The bellows is spring loaded to make it open to the halfway position, which lets you use it with spontaneous ventilation as well.
If you use this bellows without disabling the outlet valve, the back pressure on exhalation will stop the ‘Ambu’ valve from opening. This is important because it can cause a pneumothorax. The red horseshoe magnet is used to disable the valve, which allows the bellows be used with the circuit depicted above. It can be taken off if you want to use the device with a different circuit.