College Answer

A practical problem. It may be addressed thus: 

(a) Sit the patient up if possible. 
(b) Determine if the patient is actually aspirating NG feed by mixing food dye or methylene blue with feeds and repeat ETI suctioning intermittently. 
(c) Check tracheal cuff pressures and absence of air leak. presence of seal. Ensure appropriate size tracheostomy in situ. Check tracheostomy tube position above carina and that cuff is at least 2 em below the cords. 
(d) Check position of NG tube in stomach. 
(e) If all the above conditions are satisfactory and the patient still appears to be aspirating, the feeds will have to be ceased and investigations for a trachco-oesophageal fistula may need to be instigated.

Discussion

The causes of aspiration may numerous. One must identify which of the follwoing problems is present:

• Simple feed intolerance with regurgitation
• Impaired swallowing of oral contents
• failure of the tracheostomy cuff to maintain a sealed airway (i.e. cuff is failing to maintain pressure, or the whole tracheostomy has migrated out of the stoma and there is nothing in the trachea)
• Tracheo-oesophageal fistula.

A practical approach would resemble the following sequence:

• Ensure the airway equipment is not at fault:
  • Check tracheostomy position on CXR
  • Check the cuff for absence of leak
  • Check the seal of the cuff for presence of air leak 
• Ensure the feeding tube is not at fault:
  • Check NGT position on Xray
  • Ensure that the NGT is not fractured and leaking into the oral cavity
• Ensure that there is no feed intolerance
  • Check gastric residal volumes
  • Consider changing to a post-pyloric tube
• Confirm that aspiration of feeds is taking place
  • This is a step which may be omitted.
  • Historically, the "blue dye test" had been used. Evan's Blue had been mixed with the NG feeds, and the tracheal aspirates were observed for blueness. This test is far from reliable, and has been largely abandoned as it neither identifies nor excludes all aspiration, and may give a false sense of security
• Investigate oesophageal intergrity, motility, and swallow coordingation: the gold standard is videofluoroscopy, or the modified barium swallow.