Accidental insertion of a feeding tube into the lungs can have serious consequences once instillation of the feeding mixture has begun. Attaching the tube to a capnography unit allows monitoring of carbon dioxide levels during the tube insertion. This can help prevent improper tube insertion, especially when the patient is unconscious or has a depressed cough reflex. The technique is rapid, low cost and noninvasive.


Types of tubes to be inserted:

(1) Salem sump (SS) tube

(2) small bore feeding (SBF) tube: highly flexible and easily misplaced


Capnography unit: capable of both showing the carbon dioxide waveform and level in mm Hg.


Steps (Figure 3, page 938, Burns, 2001):

(1) Make sure the capnography unit is functioning properly.

(2) Connect the capnography unit to the proximal end of the tube being inserted. Figures on page 937 (Burns, 2001) indicate the connectors required for connecting each type of tube to the capnography unit.

(3) Insert the tube and monitor the capnography unit.

(4) If a CO2 waveform appears, stop the insertion at that point and determine the carbon dioxide level.

(a) If the CO2 level >= 15 mm Hg, withdraw the tube and attempt a reinsertion.

(b) If the CO2 level < 15 mm Hg, wait 3 breaths and examine the capnograph. If the CO2 level has not dissipated towards 0, or if a waveform persists (not flat), then withdraw the tube and attempt a reinsertion.

(c) If after 3 breaths the CO2 has dissipated and the waveform is flat, continue with insertion.

(5) Once the tube appears to have been inserted properly, confirm placement


Final confirmation of tube placement:

(1) Salem sump tube: auscultation, aspiration of contents and radiograph

(2) small bore feeding tube: ausculation and aspiration of contents


For auscultation air is injected into the tube while the operator listens for gurgling with stethoscope over the upper abdomen. False positives can occur with tubes placed in the tracheobronchial tree.


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