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Do nasogastric feeding tubes cause gastro-oesophageal reflux in healthy subjects?
CLINICAL NUTRITION(1990)9:347-349 GroupUK Ltd1990
QLon@mn
Do Nasogastric Feeding Tubes Cause GastroOesophageal Reflux in Healthy Subjects? J. H. Anderson, 0. J. Garden* and J. R. Anderson University Department of Surgery, The Royal Infirmary, Glasgow G31 ZER, UK (*Present address: University Department of Surgery, The Royal Infirmary, Edinburgh EH3 9YW, UK)
(Reprint requests to J.R.A.)
ABSTRACT The potential relationship between nasogastric intubation and acid gastro-oesophageal reflux was investigated. Ten healthy volunteers underwent 24h oesophageal pH monitoring following intubation with (i) a pH monitor alone, (ii) a pH monitor plus a Ryles nasogastric tube and (in) a pH monitor plus a fine-bore nasogastric feeding tube. Neither of the nasogastric intubations were associated with signihcant reflux.
INTRODUCTION
Fine-bore nasogastric tubes have an established role in the delivery of enteral nutrition [ 11.However, this technique is not without its complications. Inadvertent tube removal is commonplace, despite the addition of weighted tips [2]. Furthermore, misplacement of the tubes may result in aspiration pneumonia and can have disastrous consequences with potential complications being pneumothorax, hydrothorax, empyema, mediastinitis, and oesophageal perforation [3]. Prior to the introduction of liner feeding tubes, largebore Ryles tubes were employed. Their use was discontinued because of patient discomfort and reports of oesophageal erosions, haemorrhage and strictures [4]. Unfortunately, the pathophysiology underlying these complications was never adequately investigated and hypotheses including local irritation and gastrooesophageal reflux remain not proven. The superiority of fine-bore over large-bore nasogastric tubes has not been challenged, despite the absence of controlled comparative studies. The aim of the present study, therefore, was to compare the degree of gastrooesophageal reflux associated with fine-bore and Ryles nasogastric tubes.
MATERIALS
15 s intervals for 24 h on a data logger (SQS with averaging, Grant instruments, Cambridge). Volunteers abstained from alcohol and any medication during pH monitoring but otherwise continued their normal daily routine and diet. Subjects spent a similar proportion of each study day supine. Acid gastro-oesophageal reflux events were defined as: (i) beginning when the pH dropped below 4 for at least 1 min and (ii) ending when the pH rose above 4 for at least 1 mm. The total number and duration of reflux events were calculated. Volunteers underwent two further 24h pH recording periods after passage of a wide-bore (12 Fr, Vygon, Belgium) or fine-bore (8 Fr, Corsafe, 090120005, E. Merck Ltd., UK) nasogastric tube. The nasogastric tubes were passed in random order to a distance of 6Ocm from the nares. Satisfactory positioning in the stomach was confirmed by injecting air through the tubes and auscultating in the epigastrium. Recordings were not performed on consecutive days therefore any ‘carry over’ effects resulting from oesophageai irritation, from either the pH monitor or nasogastric tubes, did not influence the results. The data were analysed to compare the degree of reflux associated with each tube. The Wilcoxon signed-rank test was used to compare the three days’ recordings in pairs and no adjustment was made to allow for the multiple comparisons involved.
AND METHODS RESULTS
Healthy volunteers, with no history of upper gastrointestinal disease, were recruited. Each subject underwent oesophageal manometry, using the station pull-through technique in order to establish the position of the lower oesophageal sphincter [5]. Thereafter, a glass pH electrode (GK2801C, Radiometer, Denmark) was passed through the nose and placed 5cm proximal to the lower oesophageal sphincter. Oesophageal pH was recorded at 347
Ten volunteers took part in the study. There were 7 males and 3 females. The average age was 29 years (range 20-46 years). Four of the subjects were smokers (volunteers no. 2,4,5,6). The number and duration of reflux events for each day of the study are shown for each patient in Tables 1 and 2. During the baseline pH recording nine of the volunteers
NASOGASTRIC FEEDING TUBES AND GASTRO-OESOPHAGEAL
348
REFLUX
Table 1 Number of acid gastro-oesophageal reflux events associated with each day of the study (t = total, e = erect, s = supine)
Volunteer
t
1 2 3 4 S 6 7 8 9 10
4 15 S 3s 0 24 39 8 8 2
PH alone e 4 1s S 34 0 24 39 8 8 2
Number of reflux events PH + fine-bore S
t
e
0
6 8 13 20 4 21 13 3 21 3
6 8 11 20 4 19 13 3 8 3
exhibited some reflux whilst erect but only one subject demonstrated supine reflux. There were no statistically significant differences in the number or duration of reflux events when comparing the two nasogastric tubes to the baseline pH recording or comparing the line-bore and wide-bore nasogastric tubes with each other. These findings applied to both the erect and supine positions.
DISCUSSION The present study fails to provide any evidence to support the theory that nasogastric tubes may cause gastrooesophageal reflux. These findings must be confirmed in patients who will differ from normal controls in several vital respects, namely: (i) the period of nasogastric intubation will often be much longer than 24h, (ii) feeding solutions will be administered through the tubes, (iii) a greater proportion of time will be spent supine and (iv) their general health will be poorer.
Table 2
1 2 3 4 5 6 7 8 9 10
S
0 0
2 0 0 2 0 0 13 0
t 10 16 0 2s 4 56 19 3 1 0
9 1s 0 2s 5; 17 3 1 0
S
1 1 0 0 0 4 2 0 0 0
Despite the cross-over design of the present study, the large variability between each volunteer’s three sets of pH monitoring recordings may have resulted in small differences between the three study days failing to reach statistical significance. Previous studies of the reproducibility of ambulatory oesophageal pH monitoring revealed 77% concordance between the amount of acid reflux during two 24 h periods in 20 patients [6]. The small number of subjects studied possibly resulted in a type two statistical error and failure to fmd a significant difference between the groups. If a narrower fine-bore tube and a wider Ryles tube had been employed, more subtle differences in reflux associated with either tube may have been detected. Furthermore, it is not known whether oesophageal irritation may result from the width of the tube or the nature of the material from which it is made. It could be argued that tubes manufactured from equivalent materials and different diameters or vice versa would have reduced the number of variables in the study. However, the 12 Fr, PVC Ryles tube and 8 Fr, polyurethane fine-bore tube
Duration of acid gastro-oesophageal reflux events associated with each day of the study (t = total, e = erect, s = supine) Duration of
Volunteer
PH +
wide-bore e
t 7 22 11 101 0 47 148 11 15 7
PH alone e 7 22 11 98 0 47 148 11 1s 7
reflux events(minutes)
PH + fine-bore
PH f wide-bore
S
t
e
S
t
e
S
0 0 0 3 0 0 0 0 0 0
11 12 74 59 20 42 1s 7 452 6
11 12 30 59 20 38 1s 7 187 6
0 0 44 0 0 4 0 0 256 0
27 32 0 64 9 134 53 3 1 0
14 22 0 64 9 111 31 3 1 0
13 10 0 0 0 23 22 0 0 0
CLINICAL NUTRITION
were chosen since these were the tubes ,which are used in our patients for enteral feeding therefore making the results relevant to our clinical practice. Another variable would have been eliminated in the study if the volunteers had been recumbent throughout the 24h period. However, it has been shown that the majority of reflux episodes experienced by oesophagitis patients occur when the patient is upright [7]. The threshold of reflux required to produce oesophageal mucosal damage is not known and this may vary between individuals. However, pH monitoring in patients with endoscopic evidence of oesophagitis produces much higher reflux scores compared with the results obtained from our healthy volunteers during any of the three study days [8]. Despite some recent changes in design, the ideal nasogastric feeding tube has yet to be found and further investigation of tube technology is required. Wide-bore feeding tubes were abandoned due to oesophageal complications which were presumed to result from gastrooesophageal reflux [4]. However, oesophageal erosions and strictures may have been caused by local irritation or trauma rather than acid reflux. Comparative studies are required to investigate the relative importance of enteric feeding tube materials and diameter in order to minimise complications.
Submission date: 23 March 1990. Accepted afier revision: 25 June 1
349
ACKNOWLEDGEMENTS We are grateful to Dr Gordon Murray for statistical assistanceand to E. Merck Ltd., Alton, Hampshire, GU34 SHG, UK, for their support of this study.
REFERENCES [l] Silk D B A 1983 Nutritional support in clinical practice. Blackwell Scientific Publications, Oxford [2] Keohane P P, Attrill H, Jones B J M, Silk D B A 1983 Limitations and drawbacks of “fine bore” nasogastric feeding tubes. Clinical Nutrition 2: 85-86 [3] McWey R E, Curry N S, Schabel S I, Reines H D 1988 Complications of nasoenteric feeding tubes. American Journal of Surgery 155: 253-257 [4] Jones B J M 1986 Enteral feeding: techniques of administration. Gut 27(Sl): 47-50 [5] Welch R W, Drake S T 1980 Normal lower oesophageal sphincter pressure; a comparison of rapid versus slow pull-through techniques. Gastroenterology 78: 1446-1451 [6] Johnsson F, Joelsson B 1988 Reproducibility of ambulatory oesophageal pH monitoring. Gut 29: 886-889 [7] De Caestecker J S, Blackwell J N, Pryde A, Heading R C 1987 Daytime gastro-cesophageal reflux is important in oesophagitis. Gut 28: 519-526 [8] Branicki F J, Evans D F, Ogilvie A L, Atkinson M, Hardcastle J D 1982 Ambulatory monitoring of oesophageal pH in reflux oesophagitis using a portable radiotelemetry system. Gut 23: 992-998
QLon@mn
Do Nasogastric Feeding Tubes Cause GastroOesophageal Reflux in Healthy Subjects? J. H. Anderson, 0. J. Garden* and J. R. Anderson University Department of Surgery, The Royal Infirmary, Glasgow G31 ZER, UK (*Present address: University Department of Surgery, The Royal Infirmary, Edinburgh EH3 9YW, UK)
(Reprint requests to J.R.A.)
ABSTRACT The potential relationship between nasogastric intubation and acid gastro-oesophageal reflux was investigated. Ten healthy volunteers underwent 24h oesophageal pH monitoring following intubation with (i) a pH monitor alone, (ii) a pH monitor plus a Ryles nasogastric tube and (in) a pH monitor plus a fine-bore nasogastric feeding tube. Neither of the nasogastric intubations were associated with signihcant reflux.
INTRODUCTION
Fine-bore nasogastric tubes have an established role in the delivery of enteral nutrition [ 11.However, this technique is not without its complications. Inadvertent tube removal is commonplace, despite the addition of weighted tips [2]. Furthermore, misplacement of the tubes may result in aspiration pneumonia and can have disastrous consequences with potential complications being pneumothorax, hydrothorax, empyema, mediastinitis, and oesophageal perforation [3]. Prior to the introduction of liner feeding tubes, largebore Ryles tubes were employed. Their use was discontinued because of patient discomfort and reports of oesophageal erosions, haemorrhage and strictures [4]. Unfortunately, the pathophysiology underlying these complications was never adequately investigated and hypotheses including local irritation and gastrooesophageal reflux remain not proven. The superiority of fine-bore over large-bore nasogastric tubes has not been challenged, despite the absence of controlled comparative studies. The aim of the present study, therefore, was to compare the degree of gastrooesophageal reflux associated with fine-bore and Ryles nasogastric tubes.
MATERIALS
15 s intervals for 24 h on a data logger (SQS with averaging, Grant instruments, Cambridge). Volunteers abstained from alcohol and any medication during pH monitoring but otherwise continued their normal daily routine and diet. Subjects spent a similar proportion of each study day supine. Acid gastro-oesophageal reflux events were defined as: (i) beginning when the pH dropped below 4 for at least 1 min and (ii) ending when the pH rose above 4 for at least 1 mm. The total number and duration of reflux events were calculated. Volunteers underwent two further 24h pH recording periods after passage of a wide-bore (12 Fr, Vygon, Belgium) or fine-bore (8 Fr, Corsafe, 090120005, E. Merck Ltd., UK) nasogastric tube. The nasogastric tubes were passed in random order to a distance of 6Ocm from the nares. Satisfactory positioning in the stomach was confirmed by injecting air through the tubes and auscultating in the epigastrium. Recordings were not performed on consecutive days therefore any ‘carry over’ effects resulting from oesophageai irritation, from either the pH monitor or nasogastric tubes, did not influence the results. The data were analysed to compare the degree of reflux associated with each tube. The Wilcoxon signed-rank test was used to compare the three days’ recordings in pairs and no adjustment was made to allow for the multiple comparisons involved.
AND METHODS RESULTS
Healthy volunteers, with no history of upper gastrointestinal disease, were recruited. Each subject underwent oesophageal manometry, using the station pull-through technique in order to establish the position of the lower oesophageal sphincter [5]. Thereafter, a glass pH electrode (GK2801C, Radiometer, Denmark) was passed through the nose and placed 5cm proximal to the lower oesophageal sphincter. Oesophageal pH was recorded at 347
Ten volunteers took part in the study. There were 7 males and 3 females. The average age was 29 years (range 20-46 years). Four of the subjects were smokers (volunteers no. 2,4,5,6). The number and duration of reflux events for each day of the study are shown for each patient in Tables 1 and 2. During the baseline pH recording nine of the volunteers
NASOGASTRIC FEEDING TUBES AND GASTRO-OESOPHAGEAL
348
REFLUX
Table 1 Number of acid gastro-oesophageal reflux events associated with each day of the study (t = total, e = erect, s = supine)
Volunteer
t
1 2 3 4 S 6 7 8 9 10
4 15 S 3s 0 24 39 8 8 2
PH alone e 4 1s S 34 0 24 39 8 8 2
Number of reflux events PH + fine-bore S
t
e
0
6 8 13 20 4 21 13 3 21 3
6 8 11 20 4 19 13 3 8 3
exhibited some reflux whilst erect but only one subject demonstrated supine reflux. There were no statistically significant differences in the number or duration of reflux events when comparing the two nasogastric tubes to the baseline pH recording or comparing the line-bore and wide-bore nasogastric tubes with each other. These findings applied to both the erect and supine positions.
DISCUSSION The present study fails to provide any evidence to support the theory that nasogastric tubes may cause gastrooesophageal reflux. These findings must be confirmed in patients who will differ from normal controls in several vital respects, namely: (i) the period of nasogastric intubation will often be much longer than 24h, (ii) feeding solutions will be administered through the tubes, (iii) a greater proportion of time will be spent supine and (iv) their general health will be poorer.
Table 2
1 2 3 4 5 6 7 8 9 10
S
0 0
2 0 0 2 0 0 13 0
t 10 16 0 2s 4 56 19 3 1 0
9 1s 0 2s 5; 17 3 1 0
S
1 1 0 0 0 4 2 0 0 0
Despite the cross-over design of the present study, the large variability between each volunteer’s three sets of pH monitoring recordings may have resulted in small differences between the three study days failing to reach statistical significance. Previous studies of the reproducibility of ambulatory oesophageal pH monitoring revealed 77% concordance between the amount of acid reflux during two 24 h periods in 20 patients [6]. The small number of subjects studied possibly resulted in a type two statistical error and failure to fmd a significant difference between the groups. If a narrower fine-bore tube and a wider Ryles tube had been employed, more subtle differences in reflux associated with either tube may have been detected. Furthermore, it is not known whether oesophageal irritation may result from the width of the tube or the nature of the material from which it is made. It could be argued that tubes manufactured from equivalent materials and different diameters or vice versa would have reduced the number of variables in the study. However, the 12 Fr, PVC Ryles tube and 8 Fr, polyurethane fine-bore tube
Duration of acid gastro-oesophageal reflux events associated with each day of the study (t = total, e = erect, s = supine) Duration of
Volunteer
PH +
wide-bore e
t 7 22 11 101 0 47 148 11 15 7
PH alone e 7 22 11 98 0 47 148 11 1s 7
reflux events(minutes)
PH + fine-bore
PH f wide-bore
S
t
e
S
t
e
S
0 0 0 3 0 0 0 0 0 0
11 12 74 59 20 42 1s 7 452 6
11 12 30 59 20 38 1s 7 187 6
0 0 44 0 0 4 0 0 256 0
27 32 0 64 9 134 53 3 1 0
14 22 0 64 9 111 31 3 1 0
13 10 0 0 0 23 22 0 0 0
CLINICAL NUTRITION
were chosen since these were the tubes ,which are used in our patients for enteral feeding therefore making the results relevant to our clinical practice. Another variable would have been eliminated in the study if the volunteers had been recumbent throughout the 24h period. However, it has been shown that the majority of reflux episodes experienced by oesophagitis patients occur when the patient is upright [7]. The threshold of reflux required to produce oesophageal mucosal damage is not known and this may vary between individuals. However, pH monitoring in patients with endoscopic evidence of oesophagitis produces much higher reflux scores compared with the results obtained from our healthy volunteers during any of the three study days [8]. Despite some recent changes in design, the ideal nasogastric feeding tube has yet to be found and further investigation of tube technology is required. Wide-bore feeding tubes were abandoned due to oesophageal complications which were presumed to result from gastrooesophageal reflux [4]. However, oesophageal erosions and strictures may have been caused by local irritation or trauma rather than acid reflux. Comparative studies are required to investigate the relative importance of enteric feeding tube materials and diameter in order to minimise complications.
Submission date: 23 March 1990. Accepted afier revision: 25 June 1
349
ACKNOWLEDGEMENTS We are grateful to Dr Gordon Murray for statistical assistanceand to E. Merck Ltd., Alton, Hampshire, GU34 SHG, UK, for their support of this study.
REFERENCES [l] Silk D B A 1983 Nutritional support in clinical practice. Blackwell Scientific Publications, Oxford [2] Keohane P P, Attrill H, Jones B J M, Silk D B A 1983 Limitations and drawbacks of “fine bore” nasogastric feeding tubes. Clinical Nutrition 2: 85-86 [3] McWey R E, Curry N S, Schabel S I, Reines H D 1988 Complications of nasoenteric feeding tubes. American Journal of Surgery 155: 253-257 [4] Jones B J M 1986 Enteral feeding: techniques of administration. Gut 27(Sl): 47-50 [5] Welch R W, Drake S T 1980 Normal lower oesophageal sphincter pressure; a comparison of rapid versus slow pull-through techniques. Gastroenterology 78: 1446-1451 [6] Johnsson F, Joelsson B 1988 Reproducibility of ambulatory oesophageal pH monitoring. Gut 29: 886-889 [7] De Caestecker J S, Blackwell J N, Pryde A, Heading R C 1987 Daytime gastro-cesophageal reflux is important in oesophagitis. Gut 28: 519-526 [8] Branicki F J, Evans D F, Ogilvie A L, Atkinson M, Hardcastle J D 1982 Ambulatory monitoring of oesophageal pH in reflux oesophagitis using a portable radiotelemetry system. Gut 23: 992-998