Checking the correct placement of a feeding tube is one of the most crucial issues in intensive care nursing (MarIan & Allen 1998, Sanko 2004, Bourgault et al. 2007). Most feeding tube complications, such as pulmonary aspiration and feeding intolerance are associated with a displaced tube, and it is recommended that feeding tubes should be checked every shift and before each administration (Stroud et al. 2003, McClave et al. 2009).
Various methods have been created to confirm correct tube placement and to detect aspiration. The X-ray method is still a highly reliable indicator and widely accepted among practitioners to confirm both endotracheal tube and feeding tube placement (McClave & Dryden 2003, McClave et al. 2009). Often regarded as the gold standard, X-ray after tube insertion was rated ‘9 out of 9’ indicating the necessity of confirming tube placement through radiography immediately after insertion (Amorosa et al. 2008). Therefore, using chest X-ray for ICU patients on a daily basis would assist health professions to confirm tube location even when the reason for X-ray is to assess a patient’s lung status (Amorosa et al. 2008).
The pH method is also preferred over auscultation in terms of accuracy and over X-ray in terms of cost effectiveness and reducing radiological exposure (Padula et al. 2004, McClave et al. 2009). However, the pH technique requires vigilance when interpreting the pH strip because incorrect interpretation is possible (Williams & Leslie 2005). Therefore, I would entirely agree with the suggestion that a pH meter is used instead of a colorimetric pH strip as the latter may result in either an over-estimation or an under-estimation of the result (Sanko 2004).
From the paper by Turgay and Khorshid (2010), two important issues emerge. First, the results obtained from the analysis of pH samples could be affected because of the use of medications that modify gastric acidity and therefore could reveal false-negative results. It is rare that there is no significant difference between pH results in patients receiving H2 blockers and patients not receiving them. Parviainen et al. (1996) reported that the use of H2 blockers modifies the normal values for gastric pH in healthy subjects. This confirms that patients using these agents are more likely to have higher pH values compared with patients who are not. As a result, it is often suggested that an appropriate time for pH testing should be two hours from administration of any H2 blockers (Parviainen et al. 1996).
Furthermore, various kinds of proton pump inhibitors (PPIs) can have varying effects on the gastric pH in critically ill patients. Gursoy and Memis (2006) found that that using pantoprazole, esomeprazole and rabeprazole increased the gastric pH and decreased the gastric volume significantly when compared to omeprazole which is widely used in intensive care, meaning that not all PPIs agents have the same effect on gastric pH and this should be considered prior to checking tube placement. A similar situation exists for anti-acids which are also agents used to neutralise gastric pH. Accordingly, the pH technique should not be carried out without a thorough appraisal of all the potential medication affects that could result in an unreliable interpretation of pH testing (Stroud et al. 2003, McClave et al. 2009).
A further issue relates to the proximal tip of the feeding tube. A study by Phang et al. (2004) examined 82 patients with gastric intubation. Both pH values and fluoroscopy were used to confirm tube placement, then tubes were advanced into small intestine and then same techniques of checking tube placement were repeated. The results indicated that the mean values of pH in patients who receiving an acid-suppressing agent for gastric and intestinal intubation were 5·0 (SD 2·3) and 7·2 (SD 1·0), respectively. For subjects not receiving an acid-suppressing agent, the pH values were 4·0 (SD 2·5) and 6·7 (SD 1·1), respectively. This study confirms that pH vales can differ from one site to another, and we should not rely solely on a predetermined range of pH values to confirm a feeding tubes location. In addition, because there is an apparent low sensitivity of using pH values to detect gastric and intestinal intubations, this reinforces the use of radiographic confirmation even though pH technique is considered a reliable predictor of tube location (Phang et al. 2004).
Finally, it is important that practitioners recognise that mechanical ventilation can cause additional feeding tube displacement issues. Patients maintained on mechanical ventilation usually have a prolonged length of stay, inadequate feeding delivery and are at higher risk of pulmonary complications than other patients (Ibrahim et al. 2002, O’Meara et al. 2008, Metheny et al. 2010). Therefore, the risk of tube dislodgment, coiling and displacement is higher with these patients and as such, the feeding tube should be checked more frequently to avoid any undetectable tube movement as a result of patient’s coughing, vomiting or gag reflex during suctioning (Pancorbo et al. 2001, Metheny et al. 2008, 2010).