2. Materials and methods
2.1. Patients
This prospective observational study was conducted from September 2009 until the end of December 2012 at the AZ Nikolaas Hospital in Sint-Niklaas (Belgium). Preliminary findings from this study were earlier published by Boeykens and Steeman (2012) in a Dutch scientific nursing journal. A total of 331 nasogastric tubes were placed in 314 patients (≥18 years) who had been admitted to hospital and had no medical contra-indication for a NG feeding tube. All nasogastric tubes were ordered by the attending physician (for full or additional tube feeding, water and/or medications) and placed and controlled for positioning by, or placed and controlled under supervision of the same advanced practice nurse. The study was approved by the Ethical Committee of the AZ Nikolaas Hospital in Sint Niklaas and all patients or their legal representatives signed an informed consent.
2.2. Materials and protocol
All placed nasogastric tubes were single-port feeding tubes made from radio-opaque polyurethane (PUR) 10 or 14 French (FR) with a guide wire (Flocare®, Nutricia). The tubes were placed in conscious, somnolent or comatose patients. Only those conscious patients who exhibited no swallowing problems were asked to drink a sip of water through a straw during placement of the tube to promote the passing of the tube from the throat into the esophagus. The length of tube to be passed was initially estimated using the NEX-method (nose-earlobe-xiphoid). In this method the distance between the nose and the earlobe and the earlobe to the bottom of the xiphisternum is measured. This insertion-length predictor remains the most commonly used method in clinical practise (NPSA, 2011 and Ellett, 2012). After placement of the nasogastric tube the guide wire was removed to facilitate aspiration. The nasogastric tube was then fixed to the nose. For aspiration a large syringe (60 ml) with a conical end was used. Slow aspiration using a large syringe, as opposed to a smaller syringe, usually prevents the adhesion of the gastric mucosa to the tip of the nasogastric tube (Burnham, 2000). In those cases where no aspirate could initially be obtained, slow aspiration was repeated several times. If this was successful, a few drops of the aspirate were placed on a pH testing strip intended to test human gastric aspirate. (Merck® pH indicator strip/pH 2.0–9.0,) with a colour 0.5 pH units scale. When the pH was found to be ≤ 5.5, it was assumed that the end of the nasogastric tube was correctly situated in the stomach. When the results showed a pH ≥ 6.0, the characteristics (colour and consistency) of the aspirate were registered. Subsequently, 20–30 ml of air was administered through the tube and a stethoscope was used to listen for a whooshing sound below the diaphragm. If a whooshing sound could be heard, a subjective distinction was made between a loud whooshing sound, some degree of whooshing sounds (inconclusive) and no whooshing sound