Welcome back to the tasty morsels of critical care podcast.
In a break from the not quite established tradition on this show, I’ve split this into two parts. Number 13 covers the process of putting them in. This one focusses more on some physiology and when to take it out.
Some useful points on anatomy and physiology
- 18-22 rings
- cricoid to carina about 11cm
- compared to normal breathing, tracheostomy removes dead space by ~100mls. Probably no realistic change in dead space from an ET tube.
- most resistance in breathing is through the nose and the mouth so a tracheostomy theoretically removes that but the size of a tracheostomy (ID of 6-8mm) means that you lose that benefit
- overall less work of breathing in spont breathing patients with tracheostomy
- when weaning we often cap the tube to allow the patient to breath around it. A smaller tube makes this easier, as do fenetrations. How well the cuff deflates makes a big difference too
- several studies suggesting reduced WOB with tracheostomy v ETT
Dongles you might find on the the end of a tracheostomy
- Swedish nose. Effectively an HME with an O2 port on it
- Passy-Muir. Speaking Valve allowing air in but not out
This is not a straightforward question but there a few things to consider when thinking about taking it out.
- is the underlying condition resolved/stable
- ensure there is no ongoing mechanical ventilation need. Including no need for NIV as you wont be able to use NIV in the immediate decanulation period without making the patient look like a michelin man.
- is there a good cough, good strength
- what about the secretion burden (though note presence of trache can itself stimulate secretions)
- have they passed a trial of cuff down (up to 72 hrs) (though I did read a recent RCT that suggested that decannulating based on suctioning frequency rather than passing a capping trial significantly improved time to and successful decannulation)
- able to tolerate a 25% increase in WOB that comes with moving orifice from neck to mouth.
What do you do if it falls out?
- this is a recurring perennial cause of airway misadventure frequently resulting in death. The UK National Tracheostomy Safety Project is an excellent resource that is well worth some time. I interviewed Brendan Mcgrath for the RCEM Learning podcast and it is well worth a listen
- The single take home point might be – if it’s not been in very long then it’s safest to just re-intubate from the top end.
References and rationalisations:
Epstein SK. Anatomy and physiology of tracheostomy. Respir Care. 2005 Apr;50(4):476-82. PMID: 15807905.