aka Anaesthetic Addler 002.2
OK, Airway Sherlocks here is the answer. Remember the situation:
An ICU patient’s endotracheal tube was deemed to be sitting too low in the trachea based on a post-intubation chest x-ray. The cuff was deflated and the ETT was withdrawn 2 cm, so that the tip was correctly positioned in the mid-trachea. The cuff was reinflated.
Subsequently, when the cuff pressure was checked, the manometer measured a pressure of zero. Another manometer was used and the same result obtained – zero.
No air leak could be heard on auscultating the neck while the patient was bagged, and there was no air leak detected by the ventilator. The pilot balloon of the endotracheal tube was still inflated and felt firm. The patient remained stable. The manometers worked perfectly when used on other patients.
Here is how the puzzle was solved at the time:
The endotracheal tube was replaced by placing a bougie down it, removing it, then railroading a new one. This was done in a accordance with the airway mantra “if in doubt, take it out”. The main concern was an otherwise undetected cuff rupture/ leak.
The problem was immediately apparent on removal of the tube.
Earlier, when the endotracheal tube was withdrawn 2 cm the knot of the tie securing the tube was slid down and re-tightened. It wasn’t noticed that the knot had slid over the point where the line to the pilot balloon connects onto the shaft of endotracheal tube causing a kink in the pilot balloon line.
After removal of the endotracheal tube it was checked again. When the manometer was used, while squeezing the cuff with a free hand, the pressure readings correlated with how forcefully the cuff was squeezed.
When the pilot balloon line was manually kinked, the phenomenon of zero pressure readings recurred despite and inflated cuff recurred even when the cuff was squeezed.
There were a number of other great suggestions for why this problem may have occurred — the differential diagnosis for abnormal manometer readings when checking cuff pressures is surprisingly long!
The first to correctly identify the problem in this case was Seth Trueger, now F.UCEM. Seth evidently has ‘been there, done that’ with this one. Congrats!
The other lesson from this, is that it is best to completely remove whatever is securing the endotracheal tube before adjusting its position. Furthermore, if there is a problem with cuff pressure measurement make sure the pilot balloon line is checked, especially where it joins the shaft of the endotracheal tube.