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Guided Learning

Nasogastric tubes 1: insertion technique and confirming position

Indications for nasogastric tube insertion, the procedure for inserting a nasogastric tube and how to check whether it is in the correct position

 

Abstract

Durai, R. et al (2009) Nasogastric tubes 1: insertion technique and confirming position. Nursing Times; 105: 16, early online publication.

This is the first in a two-part unit on nasogastric tube management. It discusses the indications, patient preparation, insertion technique and various methods of confirming the tube’s position. According to the National Patient Safety Agency, 11 deaths and one case of serious harm occurred due to misplaced nasogastric feeding tubes over a two-year period (2003-2005). It is therefore vital for staff inserting these tubes to know both the correct insertion methods and the procedure for verifying their correct intragastric positioning.  

Keywords: Nasogastric tube, Insertion, Positioning, Patient safety

 

Authors

Rajaraman Durai, MS, MD, MRCSEd, MRCSGlas, is specialist registrar, general surgery,University Hospital Lewisham; Ramya Venkatraman, MRCPCH, DCH, is specialist registrar, paediatrics, Royal London Hospital; Philip C.H. Ng, MD, FRCS, is consultant surgeon, University Hospital Lewisham. 

 

Learning objectives

  1. Know the correct technique for inserting nasogastric tubes.
  2. Understand the principles behind various methods of verifying the correct intragastric position of the tubes.

 

Introduction

A nasogastric (NG) tube is a long polyurethane or silicone tube that is passed through the nasal passages via the oesophagus into the stomach. They are commonly inserted in surgical practice for various reasons.

According to the National Patient Safety Agency (2005a), 11 deaths and one case of serious harm occurred over a two-year period because NG feeding tubes had been misplaced.

Nasogastric tubes are inserted by nurses, junior doctors and sometimes by anaesthetists in theatre. It is vital that staff inserting them know the correct insertion technique as well as the procedure for verifying their correct positioning. This article reviews the indications for NG tubes and the benefits and risks associated with their use, and explains the correct method of insertion, as well as how to verify their correct intragastric positioning.

 

Indications

There are only two main indications for NG tube insertion – to empty the upper gastrointestinal tract or for feeding. Insertion may be for prophylactic or therapeutic reasons.

Care should be taken in cases where there may be:

  • Ear, nose and throat abnormalities or infections;
  • Possible strictures of the oesophagus;
  • Oesophageal varices;
  • Anatomical abnormalities (oesophageal diverticulae);
  • Risk of aspiration.

 

Gaining consent

Practitioners should give patients a reassuring, detailed explanation of the insertion procedure, together with the reasons why the tube is necessary. Verbal consent should then be obtained.

 

Sizes

Nasogastric tubes come in various sizes (8, 10, 12, 14, 16 and 18 Fr). Stiff tubes are easier to insert, and putting them in a refrigerator or filling them with saline helps to stiffen them. Some fine-bore tubes come with a guide wire to aid placement. The tube has markings and a radio-opaque marker at the tip to check its position on X-ray.

 

Preparation

After washing hands, prepare a trolley including gloves, local anaesthetic jelly or spray, a 60ml syringe, pH strip, kidney tray, sticky tape and a bag to collect secretions. Placing a glass of drinking water nearby is useful.

 

Insertion technique

Tubes are usually inserted by nurses or junior doctors by the bedside or by anaesthetists in theatre before or during surgery.

External measurement from the tip of the nose to a point halfway between the xiphoid and the umbilicus distance gives a rough idea of the required length.

The patient should sit up, without any head tilt (chin up). An appropriately sized tube is chosen and the tip is lubricated by smearing aqua gel or local anaesthetic gel. Anaesthetic gel is a drug so if it is used it must be prescribed, and precautions taken such as checking for allergies.

The wider nostril is chosen and the tube slid down along the floor of the nasal cavity. Patients often gag when the tube reaches the pharynx. Asking them to swallow their saliva or a small amount of water may help to direct the tube into the oesophagus. Once in the oesophagus, it may be easy to push it down into the stomach.

The correct intragastric position is then verified (see below). The tube is fixed to the nose and forehead using adhesive tapes. The stomach is decompressed by attaching a 60ml syringe and aspirating its contents. Blocked tubes can be flushed open with saline or air.

 

Verifying correct intragastric positioning

The intragastric position of the tube must be confirmed after its initial insertion, and this must be documented in the patient’s notes. There are two ways of confirming the tube’s position currently recommended. These are by pH test (Stock et al, 2008; NPSA, 2005a; 2005b) and X-ray. Other methods can be inaccurate and should not be used.

pH test

The NG tube is aspirated and the contents are checked using pH paper, not litmus paper (Earley, 2005). The NPSA (2005b) recommended that it is safe to feed patients (infants, children and adults) if the pH is 5.5 or below. This advice does not apply to neonates (preterm to 28 days). See the NPSA’s (2005b) advice and the update (2007) for more information.

Note that taking proton pump inhibitors or H2 receptor antagonists may alter the pH. Similarly, intake of milk can neutralise the acid.

Chest X-ray

When in doubt, it is best practice to use X-ray to check the tube’s location (Stock et al, 2008). Patients who have swallowing problems, confused patients and those in ICU should all be given an X-ray to verify the tube’s intragastric position. This involves taking a chest X-ray including the upper half of the abdomen. The tip of the tube can be seen as a white radio-opaque line and should be below the diaphragm on the left side.

Syringe test

This test is mentioned here for historic interest only. Also known as the whoosh test, it has been shown to be an unreliable method of checking tube placement, and the NPSA (2007; 2005a; 2005b) has said that it must no longer be used.

 

Confirming position

Correct intragastric positioning should be confirmed:

  • Immediately after initial placement;
  • Before each feed;
  • Following vomiting/coughing and after observing decreased oxygen saturation;
  • If the tube is accidentally dislodged or the patient complains of discomfort.
  • Never insert the guide wire while the nasogastric tube is in the patient.

 

Advantages

There are several advantages associated with the use of NG tubes. They will decompress the stomach by releasing air and liquid contents. This is important for patients with ileus, intestinal and gastric outlet obstruction. These conditions can cause vomiting, and patients are at risk of aspirating their stomach contents, which can lead to potentially lethal pneumonitis.

Nasogastric tubes may also be useful for feeding patients who have dysphagia, for example after experiencing a stroke, and also for those being who have undergone a tracheostomy.

Nasojejunal tubes are longer versions of NG tubes. They are inserted under endoscopic guidance to lie further in the jejunum and may be useful in feeding patients with pancreatitis.

  • Part 2 of this unit, to be published next week, looks at complications and guidance on using nasogastric tubes.

 

For the Portfolio Pages corresponding to this unit see the document above

Portfolio Pages contain activities that correspond to the learning objectives in the unit. They are presented in a convenient format for you to print out or work through on screen and can be filed in your professional portfolio as evidence of your learning and professional development.

Readers' comments (9)

  • Unfortunately, the advice in this article concerning the methods to confirm that the NG tube is correctly placed in the stomach does not deal with the everyday problems which arise in clinical settings. Certainly, checking that the aspirate is acidic with pH paper offers the most satisfactory method since it can be performed at the bed side, it can be repeated frequently to check position after insertion and between bags of feed as recommended. However, what should one do if an aspirate cannot be obtained, despite changing the patient's position and waiting? Also if the patient is on acid suppressing drugs (PPI or H2 antagonist) the measurement of pH will be uninformative. In this situation are we to X ray the patient each time the bag is changed?- the only alternative if one follows the NPSA advice. Surely, even if immediately available (which it often is not in community settings) this would lead to unacceptable doses of radiation, costs and disruption for the patient. We are then left with the dilemma whether to use the whoosh test (which the NPSA has effectively banned) to ensure that patients essential medication, hydration and nutrition are not seriously interrupted. The advice from the NPSA unfortunately does not allow for this common scenario. The research evidence showing that the whoosh test was unreliable was of poor quality and did not specify how the test should be performed. I would argue that if: 1) it is carried out by an experienced person using an adequate stethoscope (unlike many available on hospital wards) who is familiar with the variation in normal bowel sounds 2) large volumes of air are used and injected in short bursts to give a characteristic pattern which won't be confused with bowel sounds 3) the stethoscope is placed well down over the abdomen, then mistakes will be infrequent. The risk of complications of feeding a patient down a tube checked with this method (when no other method is practical) may well be less than the risks arising from missed medications (e.g. antiepileptics), fluids and feed. My patients are often put at considerable risk by delays in confirming the position of their NG tubes.
    The advice from the NPSA also misses a fundemental point that by looking for agreement between two tests (e.g. aspirate AND whoosh) each with different strengths and weaknesses (or reasons for false postives and negatives) one will get a more reliable answer than if one uses either test in isolation. I would argue that the whoosh test should be standardised, re-evaluated and if shown to be reasonably accurate it should be introduced back into clinical practice. Proper testing of competencies in its use would be essential.

    Unsuitable or offensive?

  • Thank you for your comment. It highlights a number of issues that many nurses will relate to and we are interested to hear other readers views.

    Eileen Shepherd
    Assistant Practice Editor

  • Do we have evidence to show that it is best practice to test gastrostomy tube position with pH paper? Is it necessary to test them?

    Unsuitable or offensive?

  • I believe we need to use evidence based practice on which to base our clinical guidelines. I am yet to be convinced that litmus paper is insufficient as a means of testing Nasogastric tube placement in the clinical setting and home setting as there is no substantiated evidence to support a change in practice. It much easier to determine one colour change that to identify subtle colour changes and challenge which would be safer if a risk assessment were undertaken.

    The NHS alert (2004) has been used internationally to inform practice, however there continues to remain question about the evidence which supports this practice change. In my organisation we use in excess of 7,000 fine bore feeding tubes per year and have yet to report an incident where litmus paper was not successfully used to determine placement. We have a "no-blame" reporting system so I feel confident that we have all available information.

    I continue to be challenged by the issue of confirming tube placement and continue to challenge the current literature which condemns the use of litmus paper in favour of pH paper. If litmus paper reads a pH of <4.5 and if the challenge is around tube misplacement into bronchus - bronchial secretions (pH 7.0) then shouldn't litmus paper be safe - in fact even safer than pH paper as the colour change is very distinct.

    Unsuitable or offensive?

  • Sadly the words 'best practice' have been applied to the use of pH paper. there is no research basis to support that this indeed 'best practice' and in many ways we are moving away from EBM and towards nursing ritual again. The NPSA has huge powers - bbut less knowledge imho....

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  • I have been inserting NG tubes for many years in ICU and have never had a problem. We inject air into the end of the tube and listening at the stomach with a stethoscope (whoosh test) to confirm placement. This is done frequently at the start of the shift and whenever a medication is given. I am not always able to aspirate stomach contents and we do not use the ph test in my institution. If the tube is used for feeding or medication administration then an initial xray is taken and the level where the tube sits at the nose is documented and the tube is secured well. Placement is checked thereafter by auscultation. If there is any doubt an xray is taken and read by a doctor. When a patient is turned or the head of the bed is lowered the feeds are held to prevent aspiration. Intubated patient receive an oral gastric tubes to prevent the incidence of VAP (Ventilator assisted pneumonia).

    Unsuitable or offensive?

  • Lets imagin a semi concious patient who can not co-operate at all,so can not be asked to swallow on insertion how then do we manage this.Please help

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  • "Before each feed"

    I have never been in a clinical environment where the NG tube was checked before every feed/medication administration and that includes ICU, by pH paper or any other means.

    "Never insert the guide wire while the nasogastric tube is in the patient."

    Now we have just had our NG insertion update and were told that if the tube is in the wrong place we are to feed the guide wire back into the tube to make it easier to place rather than pulling the whole tube out when you have got it past the worst part of insertion for the patient, the back of their throat.

    ?

    Unsuitable or offensive?

  • There are feeding tubes available on the market that do not require guide wires for insertion of NG tubes. Problem solved!
    Additionally with these tubes, dipping in water lubricates the tube, so no need for messy gel., which also reduces risk of infection.

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  • I cant believe we are no further on with this topic, trust and national policy is not in keeping with clinical issues faced by nurses in confirming position of tubes.pH testing is flawed because of PPI use but this is ignored by all policy makers who refuse to change guidelines.aspirate is not always obtainable so patients may have delays in feeding or medication.In the hands of an expert practitioner I believe the whoosh test can provide valuable information to help assess patency/position,although my orgaisation has banned it.Use all info -length of tube,aspirate ,check if coiled up in patients mouth,aspirate and if suspicious
    get an x ray.Never put a guide wire back in once removed you can cause peforation.

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