Aspiration of gastric contents
The ability to aspirate gastric acid is influenced by the
diameter, length and position of the tube in the gastrointestinal
tract. If the patient is checking this themselves, it also depends
on them having sufficient external tube length, manual
dexterity and the flexibility to withdraw aspirate from the
tube. Some patients may find this difficult and others may
find using a mirror useful.
The patient should be made aware that it is not uncommon
to take more than one attempt to retrieve aspirate, particularly
if the tube has moved slightly. In such cases, some adjustment
of tube position may be necessary by advancing the tube at
the nostril or withdrawing it slightly to assist in obtaining
gastric aspirate. Less than 1ml of aspirate is sufficient to check
tube position (NPSA, 2005).
Only a purple enteral syringe should be attached to an
enteral feeding tube (NPSA, 2007) and should be used when
obtaining gastric aspirate. Once aspirate has been obtained
its pH should be checked using CE marked pH-specific
indicator strips (Department for Business, Innovation and
Skills, 2012). A pH of 1–5.5 indicates gastric placement. In
some patients it has been thought that gastric pH may be
affected by the administration of acid-inhibiting medication,
such as proton pump inhibitors. Waiting for up to an hour
will allow time for the stomach to empty and the pH to fall
(NPSA, 2005).