The HME is covered in greater detail elsewhere in a small chapter dedicated to its rugged beauty. Here, one will find only a brief point form summary, designed with the intention of answering Question 27.1 from the first paper of 2012. The question shows a picture of the HME, and asks the candidate to "list the features of the device depicted". Only 38% of the candidates passed that question. Earlier, in Question 15 from the first paper of 2005, the college also wanted their candidates to compare the HME with a wet circuit. In Question 30 from the first paper of 2018, they wanted too know when this sort of humidifier is inappropriate.
In brief, the HME is a device for the passive humidification of inspired gas in short-term invasively ventilated patients. It is not as effective as a water-bath humidifier, insofar as it achieves less gas humidification; however in the short term (in the first 24-28 hours) it is equivalent to a "wet" circuit, and much cheaper
Indications for the use of a HME:
Drager have a nice brochure, spruiking the virtues of their HME systems.
However, the depicted item is the Pall Ultipor 25 Breathing System Filter.
Its all I had. Thank you to the theatre staff for kindly letting me break this piece of equipment.
The international standard for adequate humidifcation can be found here, at the ISO:
Respiratory tract humidifiers for medical use -- Particular requirements for respiratory humidification systems
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