clinical focus
Nasogastric tube depth: the ‘NEX’ guideline is incorrect Stephen J Taylor, Kaylee Allan, Helen McWilliam and Deirdre Toher
Abstract
Misplacing 17–23% of nasogastric (NG) tubes above the stomach (Rollins et al, 2012; Rayner, 2013) represents a serious risk in terms of aspiration, further invasive (tube) procedures, irradiation from failed X-ray confirmation, delay to feed and medication. One causal factor is that in the National Patient Safety Agency (NPSA) guidance to place a tube, length is measured from nose to ear to xiphisternum (NEX) (NSPA, 2011); NEX is incorrect because it only approximates the nose to gastro-oesophageal junction (GOJ) distance and is therefore too short. To overcome this and because the xiphisternum is more difficult to locate, local policy is to measure in the opposite direction; xiphisternum to ear to nose (XEN), then add 10 cm. The authors determined whether external body measurements can be used to estimate the NG tube length to safely reach the gastric body. This involved testing the statistical association of body length, age, sex and XEN in consecutive critically ill patients against internal anatomical landmarks determined from an electromagnetic (EM) trace of the tube path. XEN averaged 50 cm in 71 critically ill patients aged 53±20 years. Tube marking and the EM trace were used to determine mean insertion distances at pre-gastro-oesophageal junction (GOJ) (48 cm), where the tube first turns left towards the stomach and becomes shallow on the trace; gastric body (62 cm), where the tube reaches the left-most part of the stomach; and gastric antrum (73 cm) at the midline on the EM trace. Using body length, age, sex and XEN in a linear regression model, only 25% of variability was predicted, showing that external measurements cannot reliably predict the length of tube required to reach the stomach. A tube length of XEN (or NEX) is too short to guarantee gastric placement and is unsafe. XEN+10 cm or more complex measurements will reach the gastric body (mid-stomach) in most patients, but because of wide variation, external measurements often fail to predict a safe distance. Only the EM trace or possibly direct vision can show in real time whether the tip has safely reached the gastric body. Key words: Cortrak ■ Misplacement ■ Nasogastric tube ■ Nose-ear-xiphisternum (NEX)
B © 2014 MA Healthcare Ltd
lind tube placement commonly results in lung misplacement (1.5%), complications such as pneumothorax and/or pneumonia (0.5%), and even death (0.27%) (Taylor, 2014). Reviews consistently cite similar risk (Krenitsky, Stephen J Taylor is Research Dietitian; Kaylee Allan and Helen McWilliam are Nutrition Support Dietitians; Department of Nutrition & Dietetics, Brunel Building, Southmead Hospital; and Deirdre Toher is Statistician, Department of Engineering Design and Mathematics, University of the West of England Accepted for publication: June 2014
British Journal of Nursing, 2014, Vol 23, No 12
2011; Sparks et al, 2011), yet compared with 271 000 tubes used in a year (National Patient Safety Agency (NPSA), 2008), 2005–2010 UK reports of undetected misplacements leading to serious harm (classed as a ‘never event’) averaged only 20 per year (NPSA, 2011). This suggests both underreporting and that misplacement itself represents a 20–30 fold greater risk than never events (Taylor, 2014). Therefore, UK figures may, in reality, be nearer 3989 misplacements, 1353 pneumonias and/ or pneumothoraces and 732 deaths per year (Taylor, 2014). Mandatory pH or X-ray confirmation (NHS England, 2013) can, at best, detect misplacement, but not pre-empt it or prevent
the complications. However, an even bigger problem is that tubes are often initially misplaced in the nasopharynx, oesophagus or hiatus hernia (adults: 16.8%; children: 22.5%), with attendant aspiration risk and delays to feed and medication-related issues (Rollins et al, 2012; Rayner, 2013). To ensure enough tube is inserted to reach the stomach, but not an excess that might cause kinking and blockage, the NPSA (2011) has advised estimating the required length by measuring from nose-ear-xiphoid process (or xiphisternum). In contrast, policy for North Bristol NHS Trust is to measure the xiphisternum-ear-nose (XEN, pronounced ‘ZEN’) distance and add 10 cm because: ■■ It is more practical and accurate to locate the most difficult anatomical point first ■■ XEN approximates the distance from nose to gastro-oesophageal junction (GOJ) and therefore requires an extra 10 cm to ensure gastric placement (Figure 1). Placing a tube to the XEN distance risks feeding into the oesophagus and consequent aspiration. Even where the tube is initially confirmed as gastric, minor slippage risks displacement into the oesophagus. In addition, multi-port tubes may be confirmed as ‘gastric’ when gastric juice is aspirated from the distal ports, but feed may enter the oesophagus from the more proximal ports, above the stomach. The authors of this study measured the length of tube inserted against XEN and gastric position in intensive care unit (ICU) patients requiring routine NG or nasointestinal (NI) tube placement NI feeding was used when patient hadn’t tolerated NG feeding because of delayed gastric emptying.
Methods This study is classified as research, however because it involves collection of routine clinical data and did not involve any intervention or disclosure of patient identification, it did not require research ethics committee approval according to the Medical Research Council (NHS Health Research Authority, 2014). In ICU patients requiring placement of NG or NI tubes, XEN was measured using the
641
British Journal of Nursing.Downloaded from magonlinelibrary.com by 130.113.086.233 on February 11, 2015. For personal use only. No other uses without permission. . All rights reserved.
3. Nose
tube or a tape (Figure 1). Tube placement was guided with an EM trace using a previously published technique (Taylor et al, 2010), in conjunction with Cortrak™ tubes (NG: 92 cm, 12 F; NI: 140 cm, 10 F). As the tube enters the patient, the EM ‘signal’ from the guide-wire tip is detected by a receiver on the patient’s chest. The position of the guide-wire is calculated by a computer and the path taken by the tube is shown, in real time, as an EM trace on the computer screen. The tube has safely entered the oesophagus (Figure 2: point 1) as seen by a vertical anterior trace; significant left or right deviation above the horizontal line would indicate possible lung misplacement. The ‘lateral’ or ‘crosssection’ screens show increased depth in the oesophagus. Tube distance was noted at anatomical points that approximate specific patterns on the EM trace (Figure 2): ■■ Pre-GOJ: Just before the GOJ, the trace deflects left and from deep to shallow as it moves from oesophagus to stomach
2. Ear
1. Xiphisternum
+ 10 cm
Figure 1. Estimation of nasogastric tube distance: ‘XEN + 10’ Source: Taylor, 2014
■■ Gastric body:The trace becomes increasingly
shallow and is at the left-most position (3 o’clock) before deflecting right, towards the antrum and pylorus ■■ Gastric antrum: The trace reaches the midline, approximating the shallowest point on the trace before it again goes deeper and moves to the right in an anticlockwise circle around the duodenum. Measurements were noted in centimetres. Statistically, each series was tested for normal distribution using the Shapiro-Wilk test. Differences between the length to the gastric body and measurements were tested using a paired t-test or, if distribution was not normal, Wilcox rank sum test. Distances were analysed using linear regression for statistical difference and interaction with patient age, height (measured or reported) and weight (reported or estimated). Confirmation that the tube had attained at least gastric position was done by X-ray, pH
Nasogastric tube depth: the ‘NEX’ guideline is incorrect Stephen J Taylor, Kaylee Allan, Helen McWilliam and Deirdre Toher
Abstract
Misplacing 17–23% of nasogastric (NG) tubes above the stomach (Rollins et al, 2012; Rayner, 2013) represents a serious risk in terms of aspiration, further invasive (tube) procedures, irradiation from failed X-ray confirmation, delay to feed and medication. One causal factor is that in the National Patient Safety Agency (NPSA) guidance to place a tube, length is measured from nose to ear to xiphisternum (NEX) (NSPA, 2011); NEX is incorrect because it only approximates the nose to gastro-oesophageal junction (GOJ) distance and is therefore too short. To overcome this and because the xiphisternum is more difficult to locate, local policy is to measure in the opposite direction; xiphisternum to ear to nose (XEN), then add 10 cm. The authors determined whether external body measurements can be used to estimate the NG tube length to safely reach the gastric body. This involved testing the statistical association of body length, age, sex and XEN in consecutive critically ill patients against internal anatomical landmarks determined from an electromagnetic (EM) trace of the tube path. XEN averaged 50 cm in 71 critically ill patients aged 53±20 years. Tube marking and the EM trace were used to determine mean insertion distances at pre-gastro-oesophageal junction (GOJ) (48 cm), where the tube first turns left towards the stomach and becomes shallow on the trace; gastric body (62 cm), where the tube reaches the left-most part of the stomach; and gastric antrum (73 cm) at the midline on the EM trace. Using body length, age, sex and XEN in a linear regression model, only 25% of variability was predicted, showing that external measurements cannot reliably predict the length of tube required to reach the stomach. A tube length of XEN (or NEX) is too short to guarantee gastric placement and is unsafe. XEN+10 cm or more complex measurements will reach the gastric body (mid-stomach) in most patients, but because of wide variation, external measurements often fail to predict a safe distance. Only the EM trace or possibly direct vision can show in real time whether the tip has safely reached the gastric body. Key words: Cortrak ■ Misplacement ■ Nasogastric tube ■ Nose-ear-xiphisternum (NEX)
B © 2014 MA Healthcare Ltd
lind tube placement commonly results in lung misplacement (1.5%), complications such as pneumothorax and/or pneumonia (0.5%), and even death (0.27%) (Taylor, 2014). Reviews consistently cite similar risk (Krenitsky, Stephen J Taylor is Research Dietitian; Kaylee Allan and Helen McWilliam are Nutrition Support Dietitians; Department of Nutrition & Dietetics, Brunel Building, Southmead Hospital; and Deirdre Toher is Statistician, Department of Engineering Design and Mathematics, University of the West of England Accepted for publication: June 2014
British Journal of Nursing, 2014, Vol 23, No 12
2011; Sparks et al, 2011), yet compared with 271 000 tubes used in a year (National Patient Safety Agency (NPSA), 2008), 2005–2010 UK reports of undetected misplacements leading to serious harm (classed as a ‘never event’) averaged only 20 per year (NPSA, 2011). This suggests both underreporting and that misplacement itself represents a 20–30 fold greater risk than never events (Taylor, 2014). Therefore, UK figures may, in reality, be nearer 3989 misplacements, 1353 pneumonias and/ or pneumothoraces and 732 deaths per year (Taylor, 2014). Mandatory pH or X-ray confirmation (NHS England, 2013) can, at best, detect misplacement, but not pre-empt it or prevent
the complications. However, an even bigger problem is that tubes are often initially misplaced in the nasopharynx, oesophagus or hiatus hernia (adults: 16.8%; children: 22.5%), with attendant aspiration risk and delays to feed and medication-related issues (Rollins et al, 2012; Rayner, 2013). To ensure enough tube is inserted to reach the stomach, but not an excess that might cause kinking and blockage, the NPSA (2011) has advised estimating the required length by measuring from nose-ear-xiphoid process (or xiphisternum). In contrast, policy for North Bristol NHS Trust is to measure the xiphisternum-ear-nose (XEN, pronounced ‘ZEN’) distance and add 10 cm because: ■■ It is more practical and accurate to locate the most difficult anatomical point first ■■ XEN approximates the distance from nose to gastro-oesophageal junction (GOJ) and therefore requires an extra 10 cm to ensure gastric placement (Figure 1). Placing a tube to the XEN distance risks feeding into the oesophagus and consequent aspiration. Even where the tube is initially confirmed as gastric, minor slippage risks displacement into the oesophagus. In addition, multi-port tubes may be confirmed as ‘gastric’ when gastric juice is aspirated from the distal ports, but feed may enter the oesophagus from the more proximal ports, above the stomach. The authors of this study measured the length of tube inserted against XEN and gastric position in intensive care unit (ICU) patients requiring routine NG or nasointestinal (NI) tube placement NI feeding was used when patient hadn’t tolerated NG feeding because of delayed gastric emptying.
Methods This study is classified as research, however because it involves collection of routine clinical data and did not involve any intervention or disclosure of patient identification, it did not require research ethics committee approval according to the Medical Research Council (NHS Health Research Authority, 2014). In ICU patients requiring placement of NG or NI tubes, XEN was measured using the
641
British Journal of Nursing.Downloaded from magonlinelibrary.com by 130.113.086.233 on February 11, 2015. For personal use only. No other uses without permission. . All rights reserved.
3. Nose
tube or a tape (Figure 1). Tube placement was guided with an EM trace using a previously published technique (Taylor et al, 2010), in conjunction with Cortrak™ tubes (NG: 92 cm, 12 F; NI: 140 cm, 10 F). As the tube enters the patient, the EM ‘signal’ from the guide-wire tip is detected by a receiver on the patient’s chest. The position of the guide-wire is calculated by a computer and the path taken by the tube is shown, in real time, as an EM trace on the computer screen. The tube has safely entered the oesophagus (Figure 2: point 1) as seen by a vertical anterior trace; significant left or right deviation above the horizontal line would indicate possible lung misplacement. The ‘lateral’ or ‘crosssection’ screens show increased depth in the oesophagus. Tube distance was noted at anatomical points that approximate specific patterns on the EM trace (Figure 2): ■■ Pre-GOJ: Just before the GOJ, the trace deflects left and from deep to shallow as it moves from oesophagus to stomach
2. Ear
1. Xiphisternum
+ 10 cm
Figure 1. Estimation of nasogastric tube distance: ‘XEN + 10’ Source: Taylor, 2014
■■ Gastric body:The trace becomes increasingly
shallow and is at the left-most position (3 o’clock) before deflecting right, towards the antrum and pylorus ■■ Gastric antrum: The trace reaches the midline, approximating the shallowest point on the trace before it again goes deeper and moves to the right in an anticlockwise circle around the duodenum. Measurements were noted in centimetres. Statistically, each series was tested for normal distribution using the Shapiro-Wilk test. Differences between the length to the gastric body and measurements were tested using a paired t-test or, if distribution was not normal, Wilcox rank sum test. Distances were analysed using linear regression for statistical difference and interaction with patient age, height (measured or reported) and weight (reported or estimated). Confirmation that the tube had attained at least gastric position was done by X-ray, pH
