551966

research-article2014

PENXXX10.1177/0148607114551966Journal of Parenteral and Enteral NutritionSilk and Quinn

Original Communication

Dual-Purpose Gastric Decompression and Enteral Feeding Tubes Rationale and Design of Novel Nasogastric and Nasogastrojejunal Tubes

Journal of Parenteral and Enteral Nutrition Volume XX Number X Month 201X 1­–13 © 2014 American Society for Parenteral and Enteral Nutrition DOI: 10.1177/0148607114551966 jpen.sagepub.com hosted at online.sagepub.com

David B. A. Silk, MD1; and David G. Quinn, MBA2

Abstract Background: The importance of early postoperative nutrition in surgical patients and early institution of enteral nutrition in intensive care unit (ICU) patients have recently been highlighted. Unfortunately, institution of enteral feeding in both groups of patients often has to be postponed due to delayed gastric emptying and the need for gastric decompression. The design of current polyvinylchloride (PVC) gastric decompression tubes (Salem Sump [Covidien, Mansfield, MA] in the United States; Ryles [Penine Health Care Ltd, Derby, UK] in the United Kingdom and Europe) make them unsuitable for their subsequent use as either nasogastric enteral feeding tubes or for continued gastric decompression during postpyloric enteral feeding. To overcome these problems, we have designed a range of polyurethane (PU) dual-purpose gastric decompression and enteral feeding tubes that include 2 nasogastric tubes (double lumen to replace Salem Sump; single lumen to replace Ryles). Two novel multilumen nasogastrojejunal tubes (triple lumen for the United States; double lumen for the United Kingdom and Europe) complete the range. By using PU, a given internal diameter (ID) and flow area can be incorporated into a lower outside diameter (OD) compared with that achieved with PVC. The ID and lumen and flow area of an 18Fr (OD 6.7 mm) PVC Salem Sump can be incorporated into a 14Fr (OD 4.7 mm) PU tube. The design of aspiration/infusion ports of current PVC and PU tubes invites occlusion by gastrointestinal mucosa and clogging by mucus and enteral feed. To overcome this, we have designed long, single, widened, smooth, and curved edge ports with no “dead space” to trap mucus or curdled diet. Involving up to 214° of the circumference, these ports have up to 11 times the flow areas of the aspiration ports of current PVC tubes. Conclusion: The proposed designs will lead to the development of dual-purpose nasogastric and nasojejunal tubes that will significantly improve the clinical and nutrition care of postoperative and ICU patients. (JPEN J Parenter Enteral Nutr. XXXX;xx:xx-xx)

Keywords gastric decompression; postoperative; critically ill patient; enteral nutrition; dual-purpose gastric decompression; enteral feeding tubes

Clinical Relevancy Statement

Introduction

The importance of early postoperative nutrition in surgical patients and early institution of enteral nutrition in critically ill patients has now been highlighted. Unfortunately, in both groups of patients, the efficacy of nasogastric enteral feeding is often limited by delayed gastric emptying and the need for gastric decompression. The design features of current gastric decompression tubes (Salem Sump [Covidien, Mansfield, MA] in the United States; Ryles [Penine Health Care Ltd, Derby, UK] in the United Kingdom and Europe) mitigate against their usefulness as a means of doubling up as enteral feeding tubes when improved gastric function returns. The use of the alternative post–ligament of Treitz nasojejunal route is currently restricted to only 12% of patients who have this need. This situation persists mainly because of delays and difficulties in obtaining small bowel access. Our study presents the designs of a new range of dual-purpose gastric decompression and enteral feeding tubes to overcome all 3 problems. Their development will lead to improved nutrition management of postoperative and critically ill patients.

The early institution of nasogastric enteral feeding in critically ill patients may improve outcome, in terms of incidence of infection, low complication rates, and mortality.1-5 Unfortunately, From the 1Department of Academic Surgery, Imperial College London, United Kingdom, and 2Research & Development, Radius International LP, Grayslake, Illinois. Conflicts of interest: DGQ is president & CEO of Radius International, Inc. Radius International, Inc. will benefit financially when the tubes described herein are developed and marketed. DBAS is currently unpaid ad hoc medical adviser to Radius International, Inc. It is likely that he will benefit financially when the tubes described herein are developed and marketed. Received for publication May 15, 2014; accepted for publication August 18, 2014. Corresponding Author: David B. A. Silk, MD, Department of Academic Surgery, Imperial College London, St Mary’s Hospital Campus, 110 Harley St, London W1G 7JG, UK. Email: [email protected]

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gastric emptying is impaired in critically ill patients,6-10 and the complications that arise from this (high residual gastric aspirate, volumes of regurgitation, and aspiration) limit the overall efficacy of nasogastric enteral feeding, so, on average, critically ill patients receive only about half of their nutrition requirements when fed via the nasogastric route.11-13 Although North American guidelines do not recommend the routine use of small bowel enteral feeding in critically ill patients, they do recommend its use in those patients who are intolerant of nasogastric enteral feeding.14,15 The authors of the recently updated Canadian Critical Care Nutrition guidelines found that only 12% of 183 intensive care units (ICUs) from 27 counties employed small bowel feeding when nasogastric feeding was partly tolerated.16 Subsequent enquiry revealed that the commonest barrier to the implementation of small bowel feeding in these patients was the delay and difficulty in obtaining small bowel access.16 We believe that this is, at least in the past, due to inadequate design of small bowel feeding tubes.17 When gastric emptying is severely impaired in critically ill patients, they may require formal gastric decompression, as do surgical patients undergoing major upper gastrointestinal (GI) surgery.18,19 As is the case with critically ill patients, the newly developing early recovery after surgery (ERAS) protocols have incorporated early postoperative feeding as an integral part.20-26 Gastric decompression in the United States is most commonly achieved by intubation with a dual-lumen Salem Sump (Covidien, Mansfield, MA) tube and use of a constant or intermittent suction technique.27 On occasion, single-lumen tubes such as the Levine (Bard Medical, Covington, GA) tube are used. In the United Kingdom and Europe, gastric decompression is achieved by simple syphonage following intubation with a Ryles (Penine Health Care Ltd, Derby, UK) single-lumen tube. It is not uncommon for some patients requiring nasogastric decompression to require nasogastric enteral feeding when gastric function improves. Unfortunately, the design characteristics of the Salem Sump, Levine, and Ryles tubes mitigate against those being able to routinely double up as feeding tubes. The aim of the present communication is to describe the design of a range of dual-purpose gastric aspiration and enteral feeding tubes and to compare their design properties with existing and currently available tubes. The first 2 are dual-purpose nasogastric tubes that fulfill the criteria for use as gastric decompression tubes as well as nasogastric feeding tubes. Two novel multilumen nasogastrojejunal tubes that have the capability of simultaneously providing gastric decompression and delivering post–ligament of Treitz enteral feeding complete the range.

Existing Nasogastric Decompression Tubes

Figure 1.  Drawings of a Salem Sump tube 18Fr (outside diameter 6.7 mm) purchased by the authors: A is a side view of the tube. The tube incorporates a radiopaque strip running through its full length. Cross section A1 shows the aspiration lumen (flow area 6.03 mm2) and the smaller elliptical air vent (area 1.96 mm2). Cross section A2 is the proximal aspiration port punched through 1 wall of the tube (area 6.0 mm2). Cross section A3 shows 1 of the middle 8 aspiration ports that are formed by punching completely through the tube (area 6.0 mm2). Cross section A4 shows the 2 distal aspiration ports (area 9.5 mm2) formed by punching through the tube wall and cutting through both the air vent lumen and aspiration lumen. Because the distal aspiration ports are almost cut through the entire tube circumference, the ports are punched at an angle to minimize kinking during intubation. Cross section A5 shows the tip of the tube distal to the 2 distal aspiration ports. B is a top view of the tube. B1 to B4 are the equivalent cross-sectional views of the aspiration ports, and B5 is a cross-sectional view of the tip of the tube.

(PVC). The most commonly used tube has an outside diameter (OD) of 6.7 mm (18Fr). The Salem Sump tube is dual lumen and contains an air vent to facilitate constant or intermittent suction of gastric contents. Figure 1 shows a side view (A) and top view (B) of the tube and illustrates that the tube incorporates a radiopaque strip running through its full length and how multiple aspiration ports are punched through either one wall (A2, B2) or two walls of the tube (A3, B3). Figures 2 and 3 show schematic representations of Salem Sump gastric decompression function. The directions of air flow in and out of the system, together with the direction of the flow of aspirated gastric contents, are depicted in Figure 2. Figure 3 shows the position of the vented air exit in relationship to the distal aspiration port and how much of the air entering the aspiration port at this level travels back up the aspiration lumen by simple flotation aided by intermittent or constant suction. Despite their presence, there is little aspiration occurring from the 6 middle aspiration ports (Figure 3, A2). Actual aspiration of gastric contents takes place via the 2 proximal ports (Figure 3, A3, A4).

Salem Sump Gastric Decompression System

Ryles Tube

The Salem Sump gastric decompression system widely used in the United States is manufactured from polyvinylchloride

The simpler Ryles tube gastric aspiration system widely used in the United Kingdom and Europe is based on the

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Figure 2.  Schematic representation of the Salem Sump gastric decompression system function: top view of the Salem Sump tube showing flow of air into and out of the system, together with the direction of flow of aspirated gastric contents. A1 to A5 as described in Figure 1.

Figure 4.  Drawings of a Ryles tube, 122 cm long (outer diameter 5.3 mm; 16Fr) purchased by the authors. The tube has 4 aspiration ports punched through 1 wall (area 9.26 mm2). The aspiration ports are staggered on opposite walls. (A [side view]; B [top view]) Radiopacity is achieved by virtue of a radiopaque cylinder inserted into the tip at the distal end of the tube. Crosssectional views of the aspiration ports are shown, and the black arrow depicts the direction of flow of aspirated gastric contents.

punched through one wall, and their position is staggered on opposite walls.

Rationale Behind the Need for Redesign of Gastric Aspiration Tubes

Figure 3.  Schematic representation of the Salem Sump gastric decompression system function: cross section A1 is the only port for the vented air and is positioned immediately adjacent to the open aspiration port (both the air vent lumen and aspiration lumen terminate just proximal to the aspiration port). Much of the air entering the aspiration port at this point travels back up the aspiration lumen by simple flotation. Despite their presence, there is little aspiration taking place via the 6 middle ports (A2). Actual aspiration of contents begins via dual-port A3. Aspiration also takes place via the proximal aspiration port A4. This port is placed 90° from port A3 to help prevent mucosal suction from occluding the aspiration lumen. A5 shows the approximate 50/50 mix of the fluid and air finally aspirated from the patients.

employment of a single-lumen tube and aspiration of gastric contents by the process of simple syphonage. The commonly used tubes have an OD of 5.3 mm (16Fr) and a length of 122 cm. Like the Salem Sump tubes, the Ryles tubes are manufactured of PVC. As shown in Figure 4, the 4 aspiration ports are

The realization that the widespread practice of starving patients in the immediate period after GI surgery (“nil by mouth”) may not be beneficial was finally challenged by a systematic review and metanalysis.28 Subsequently, the benefits of early postoperative nutrition support on the outcome of both normally nourished and malnourished surgical patients have been shown.29-31 As outlined above, the demonstration of the benefits of early postoperative nutrition support has led to the inclusion of early postoperative nutrition as a modality in most ERAS protocols.20-26 In those patients requiring early postoperative gastric decompression or those needing gastric decompression (eg, small and large intestinal obstruction, paralytic ileus, and acute intestinal pseudo-obstruction), it follows that there could be advantages in administering enteral nutrition (EN) via their nasogastric tubes when it has been deemed clinically that gastric function has improved. There are a number of important reasons why it is impractical to assume this dual-purpose role for Salem Sump and Ryles tubes. The first relates to the fact that despite their widespread use, both the Salem Sump and Ryles tubes have inherent design flaws. Both tubes are manufactured of PVC. The properties of PVC are such that the ratio of internal flow lumen to the outside diameter is relatively low. This means that to achieve satisfactory flow properties, the tubes have to have a larger than ideal outside diameter32 (most Salem Sump tubes used are 18Fr). Consequently, the tubes are often very uncomfortable

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for the patient, and the desire for their removal is great, making it difficult to employ their use for longer periods for early postoperative nutrition support. Second, both tubes incorporate multiple side aspiration ports. When adhering to the wall of the stomach, the side ports can become blocked, giving rise to difficulties in aspiration.33,34 In many instances, the lumen of the tubes becomes obstructed by mucus (particularly in Salem Sump tubes during intermittent suction), and when the proximal side ports are involved, tube blockage will occur.35 This whole process of tube blockage can be exacerbated during enteral feeding due to the precipitation of the protein source of infused enteral diet at acid pH36 as well as by the administration of medication via the tubes.34,36,37 Clogging of enteral feeding tubes with side ports is thus a common phenomenon.35 Our design program has sought to overcome these problems and has led to the design of 4 novel dual-purpose gastric aspiration and enteral feeding tubes. The first 2 are nasogastric tubes, one to replace the Salem Sump tube and the second to replace the Ryles tube. The other 2 are novel dual-purpose gastric aspiration and post–ligament of Treitz nasojejunal feeding tubes suitable for early postoperative feeding and suitable as a means of optimizing the enteral feeding of the intensive care patient.

Design Principles Tube Material Our design program has focused on the use of aromatic polyurethane (PU) rather than PVC as the tube material33 since the basic chemical formulation of aromatic PU has a number of advantages over PVC (Figure 5). It is stronger, allowing thinner walls, resulting in an increased internal diameter (ID) and flow areas for a given OD.32-34 As a consequence of its strength, it does not kink as easily and is resistant to fracture (breakage). PU is biocompatible and affords a long life in situ. Aromatic PU does not react adversely with medication. Thus, for the same flow area, this enables a narrower diameter and a more comfortable tube to be employed. These principles are illustrated in Figure 5. In our experience, a satisfactory “kink” resistance is maintained, and insertion using an introducer wire is enhanced by the use of an internal water-activated lubricant.32-34

Extrusion Techniques Gastric and enteric feeding and aspiration tubes are manufactured by extruding tube material (eg, PVC, PU, or silicone) under pressure over purpose-designed solid steel models. In the novel designs described here, we have designed dual-purpose single-, dual-, and 3-lumen PU gastric aspiration and enteral feeding tubes. An important aim of our design program has been to maximize the ID and flow area of each lumen to minimize the OD of the tubes to reduce patient discomfort.

Figure 5.  Relationships between internal diameter (ID), outer diameter (OD), and flow areas for single-lumen polyvinyl chloride (PVC) and polyurethane tubes. Note that for the same OD (A), the ID for a 16Fr OD tube is 18.2% greater for the polyurethane tube compared with the PVC tube, and the flow area 41.3% greater. For the same ID (B), the OD of the polyurethane tube is 4.7 mm, which is 12.8% less than that (OD = 5.3 mm) of the equivalent PVC tube.

Figure 6 compares cross sections of a Salem Sump tube (Figure 6A) with those of our proposed designs of a Radius dual-lumen tube (Figure 6B) and triple-lumen tube (Figure 6C). Note that the Salem Sump tube (labeled 18Fr but actually 19Fr and ovoid in shape) has a lumen flow area of only 6.03 mm2, whereas our 14Fr dual-lumen and our 16Fr triple-lumen tubes will have lumen flow areas of 7.08 mm2. Both of our tubes have greater air vent areas than the 18Fr Salem Sump tube.

Aspiration/Infusion Port Design The punched-out side ports of the Salem Sump and the Ryles tubes present a narrow flat surface approximating to less than 75° of the circumference of the OD of the tubes (Figure 7A). As can be seen, these ports can easily be occluded by gastric mucosa, making it difficult to aspirate gastric contents. Figure 7 also shows the evolving designs of our aspiration/infusion ports. The aspiration/infusion port was employed in the design of our first nasogastric feeding tube (Figure 7B). This was a long, single, widened, smooth, and curved edged port with no “dead space” distal to the outflow port to trap mucus or curdled

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Figure 6.  Cross-sectional views of the 18Fr Salem Sump tubes comparing aspiration lumens and the new tube designs. (A) Cross-sectional view of the 18Fr Salem Sump tube showing the aspiration lumen (flow area 6.03 mm2) and air vent lumen (1.96 mm2). (B) Cross-sectional view of the newly designed 14Fr dual-lumen tube showing the aspiration lumen (flow area 7.08 mm2) and air vent lumen (flow area 2.72 mm2) and air vent lumen (flow area 2.72 mm2). Note that that for comparable lumen flow areas, the outer diameter (OD) of the 14Fr tube is substantially less than that of the Salem Sump tube. (C) Crosssectional drawing of our newly designed triple-lumen tube. Straight horizontal and vertical segments separate the lumens. The superior lumen has a flow area of 7.20 mm2, which is greater than the aspiration lumen of the 18Fr Salem Sump tube (6.03 mm2). Each of the other 2 lumens has flow areas of 3.13 mm2. Note how it has been possible to incorporate 3 lumens into a tube of narrower OD (16Fr, 5.3 mm) than the double-lumen 18Fr Salem Sump tube.

diet.32,33 Gastric contents could be aspirated in 60% of occasions after tube insertion.32 In the second design (Figure 7C) that formed the basis of our second nasogastric feeding tube,34 sidewalls were lowered to 186° of the lumen diameter, increasing the outflow area by 65.9% compared with the equivalent tube in Figure 7B. Clinical studies showed this resulted in an aspiration rate of 72% on the first attempt.34 In the present design, we have further extended the diameter of the aspiration/infusion ports to 214° of the OD circumference (Figure 7D). This results in a further increase in outflow area of 41.1% compared with the second design, and we hope to achieve aspiration rates of 95%–100% as a consequence. Note in Figure 7E

Figure 7.  Comparative aspiration/infusion port areas for 9Fr (outer diameter [OD] 3 mm) nasogastric feeding/aspiration tubes. (A) The punched-out side ports of a polyvinyl chloride (PVC) tube present a narrow flat surface approximating to less than 75° of the circumference of the OD of the tubes. Note the area of the aspiration port of 2.8 mm2 for a 9Fr (OD 3.0 mm) tube. Note also how easily these ports can be occluded by gastric mucosa. (B) The evolving designs of our novel aspiration/infusion ports and cross-sectional and side views of the aspiration port of our first 9Fr polyurethane nasogastric enteral feeding tube. By lowering the sidewall, the aspiration/infusion port now incorporates 106° of the circumference of the OD of the tube.21,22 (C) Cross-sectional and side views of the aspiration/infusion port of our second 9Fr nasogastric enteral feeding tube design.26 The sidewalls were lowered further and the port now incorporates 186° of the circumference of the OD of the tube, and importantly, the area of the port has been increased from 12.6 mm2 to 20.9 mm2 (65.9% increase). (D) The present proposed design where we have further lowered the sidewalls of the port so that the port now incorporates 214° of the circumference of the OD of the tube. This has allowed a further increase in the area of the port to 29.5 mm2 (41.1% increase compared with Figure 7C). All these aspiration/infusion port designs present long, widened smooth and curved edge ports with no “dead space” distal to outflow/inflow to trap mucus or curdled diet, and the ports cannot be occluded by gastric mucosa.

that the further lowering of the sidewalls is assisted by the center alignments of the central port wall radius and by the reinforced inferior segment of the tubes.

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Figure 8.  Comparisons of aspiration port sizes and areas. (A) The aspiration port area of an 16Fr (outer diameter [OD] 5.3 mm) Ryles tube is 9.2 mm2, which is larger than the aspiration port of an 18Fr (OD 6.0 mm) double-lumen Salem Sump tube (6.0 mm2). (B) Drawing shows how the aspiration port of our proposed dual-purpose double-lumen 14Fr (OD 4.7 mm) nasogastric tube will involve 180° of the circumference of the tube and will have an area of 54.8 mm2. Note how the gastric mucosa cannot occlude the port. (C) The gastric aspiration port of our proposed triple-lumen dual-purpose nasogastrojejunal tubes involving 164° of the circumference of the tube; the aspiration port will have an area of 64.7 mm2. Again, note how the gastric mucosa cannot occlude the port.

Our basic port design growth shown in Figure 7 has been further developed to improve the performance of our new dualpurpose dual-lumen gastric aspiration feeding tube and the triple-lumen nasogastrojejunal tube. These new design concepts are illustrated in Figure 8. As a comparison, Figure 8A shows the effective 9.2-mm2 port area of the 16Fr Ryles tube and the 6.0-mm2 port area of the 18Fr Salem Sump tube. Note that the port area of the smaller 16Fr Ryles tube is larger than the port area of the larger 18Fr Salem Sump tube. This differential is caused by the requirement for the inclusion of 2 lumens in the Salem Sump vs 1 lumen in the Ryles. Figure 8B also illustrates our 14Fr dual-lumen gastric tube with an effective port area extending approximately 180° around the circumference of the tube that results in an effective port area of 54.8 mm2 (6 times that of the 16Fr Ryles tube and 9 times that of the 18Fr Salem

Figure 9.  Views of the dual-lumen gastric aspiration and enteral feeding tube. (A) The superior aspiration lumen transitioning into the purpose-designed aspiration port and the inferior air lumen transitioning into the air lumen port. (B, C) Lateral views of the tube tip showing the relationship between the aspiration/ infusion port and the air vent exit port. (D) Superior view of the aspiration/infusion port and (E) an inferior view of the air vent exit port.

Sump tube). Finally, Figure 8C shows an 18Fr nasogastrojejunal tube. The aspiration port area is 67.7 mm2 or 7 times larger than the 16Fr Ryles tube and 11 times larger than the 18Fr Salem Sump tube.

Proposed Designs of the New DualPurpose Gastric Aspiration and Enteral Feeding Tubes Dual-Lumen Nasogastric Aspiration and Enteral Feeding Tube Designed to replace the Salem Sump decompression system, the 14Fr (OD 4.7 mm) dual-lumen tube incorporates an air vent lumen to conform to the practice of current clinical protocols of the Salem Sump decompression system (Figure 9). Figure 9A also shows how the interior lumen acts as the air vent, with air exiting below the aspiration/infusion port. Aided by intermittent or constant suction, gastric contents are aspirated via the larger diameter superior lumen. When enteral feeding is required, the enteral diet is infused via the larger

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Figure 10.  Lateral and cross-sectional views of the tip of the dual-lumen gastric aspiration and enteral feeding tube showing the relationship between the purpose-designed aspiration/infusion port and the inferior air vent exit port. (A) Schematic lateral view of the dual-lumen gastric aspiration and enteral feeding tube. (B1–10) Cross-sectional views highlighting the transitioning of the superior aspiration/infusion lumen (B1) into its purposedesigned port (B5–B8) and the interior air vent lumen (B1) into its exit port (B2–B5). Note also the reinforcing extrusion commencing at cross-sectional level 3 and transitioning from this level through levels 4 and 5 to be incorporated into the molded tip of the tube (B5–B10).

superior lumen and then exits via the aspiration port. Figure 9B,C also shows side views of the aspiration/infusion port and its relationship to the air vent exit port. Finally, Figure 9D shows a superior view of the aspiration/infusion port, and Figure 9E demonstrates an inferior view of the air vent exit port. Figure 10A shows a schematic lateral view of the tip of the tube, again showing the relationship between the aspiration/ infusion port and the air vent exit port. Figure 10B also shows cross-sectional views of the tip of the tube, demonstrating how the 2 lumens of the tube transition into the aspiration/infusion port and the air vent ports. Figure 10B1–5 shows the transition of the air vent lumen into the air vent exit port, and Figure 10B5–8 shows the transition of the aspiration lumen into the aspiration/infusion port. Figure 10C shows the lateral cross section of Figure 10A. As discussed above and shown in Figure 8, the diameter of the aspiration/infusion port has been extended to 180° of the OD circumference to further aid aspiration and further optimize the anticlogging features of the port. Also, as shown in Figure 7 and cross-sectional Figure 10B3–7, the inferior aspect of the tip distal to the air vent port has been reinforced by an added extrusion to maximize flexing and prevent kinking.

Figure 11.  Single-lumen gastric aspiration and enteral feeding tube. (A) Drawings of the proximal and distal ends of the tube. (B) Lateral, oblique, and superior views of the tip of the tube, highlighting the design of the aspiration/infusion port.

Single-Lumen Dual-Purpose Nasogastric Aspiration and Enteral Feeding Tube This single-lumen tube is designed to replace the Ryles tube. Figure 11A shows drawings of the tube, and Figure 11B shows side, oblique, and superior views of the tip of the tube with its aspiration/infusion port. Figure 12A shows a further side view of the tip and the aspiration/infusion port design. Figure 12B shows a cross-sectional view of the single-lumen tube transitioning into the aspiration/ infusion port. Note how the port arc extends approximately 214° around the circumference of the internal lumen. The height of the midpoint of the radial arc (Figure 12B5) is approximately 25% of the height of the internal lumen. As also shown in Figure 11Bi, there are no sidewalls on the distal 50% of the radial arc. The novel design features of the aspiration/infusion port further improve its anticlogging properties, and as with the dual-lumen tube, we anticipate aspiration rates of 95%–100%.

Comparisons of Nasogastric Tube Designs Table 1 shows comparisons of the design properties of the proposed dual-purpose double- and single-lumen nasogastric aspiration and enteral feeding tubes with those of the Salem Sump dual-lumen gastric decompression tube and the Ryles singlelumen gastric decompression tube. The substitution of PU for PVC as the tube material permits, for a given OD, higher IDs

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Figure 12.  Lateral and cross-sectional views of the singlelumen, dual-purpose gastric aspiration and enteral feeding tube. (A) Lateral view of the tip of the tube. (B) Cross-sectional views showing transitioning of the single lumen into its purposedesigned aspiration infusion port (C). Note that in the design of this tube, the sidewalls of the aspiration/infusion port have been lowered further than was the case in the dual-lumen tube, so the aspiration/infusion port now incorporates 214° of the circumference of the outer diameter (OD) of the tube, thereby maximizing the flow area of the aspiration/infusion port.

and flow areas for the internal lumens. Thus, to achieve at least similar IDs and flow areas of an 18Fr (OD 6.7 mm) dual-lumen Salem Sump tube, our designs show that these can be incorporated into a 14Fr (OD 4.7 mm) PU tube. Note the substantial differences in aspiration/infusion port areas of the 2 tubes. To achieve at least similar IDs and lumen flow areas of a 16Fr single-lumen gastric decompression tube (Ryles), our designs show that these can be incorporated into a 14Fr (OD 4.7 mm) PU tube. Note again the substantial differences in aspiration/ infusion port areas of these 2 tubes. The advantages to the patient of using lower OD nasogastric tubes are obvious.

Dual-Purpose Gastric Aspiration and Post–Ligament of Treitz Jejunal Enteral Feeding Tubes The development of a nasoenteral tube that would simultaneously provide a means of early postoperative gastric decompression as

well as post–ligament of Treitz jejunal enteral feeding would not only satisfy the requirements of current ERAS protocols in patients undergoing major upper gastroesophageal18 hepatobiliary and pancreatic surgery19 but would also play an important role in the feeding of patients in the ICU who are not able to tolerate nasogastric feeding.38 North American guidelines recommend small bowel feeding of ICU patients who are not able to tolerate nasogastric feeding.16 The reason that we propose the post–ligament of Treitz nasojejunal route is that we believe the abnormal proximal small bowel motility that has now been demonstrated to occur in critically ill patients39,40 is the cause of the high rate of retroperistalsis of nasoduodenal sited tubes into the stomach.41 An added advantage of the post–ligament of Treitz nasojejunal route is that “downstream” enteral feeding should reduce the incidence of aspiration and associated pneumonia in these patients.12,42,43 In the ICU patient, the abnormal proximal small bowel motility with retrograde peristalsis also leads to duodenogastric bile reflux.39,40 Post–ligament of Treitz nasojejunal feeding in ICU patients is associated with increased gastric secretion volumes.44 These, together with duodenogastric biliary reflux, result in the development of biliary esophagitis in those patients.45,46 It is therefore important when considering the post–ligament of Treitz jejunal feeding of ICU patients as well as those who have undergone major upper GI surgery and have developed delayed gastric emptying that a dual-purpose nasoenteral tube should incorporate a means of gastric aspiration as well as a distal port for enteral feeding from which it is possible to aspirate proximal small intestinal contents.38 Our new tube designs incorporate all these features. Manufactured of PU and using our novel extrusion techniques together with our port designs, we describe here the design of 2 tubes. The first is a triple-lumen tube incorporating a gastric aspiration lumen and aspiration port together with an assisted air vent lumen and an exit port along with a jejunal infusion lumen and port. This tube will conform to current U.S. clinical protocols for air-vented assisted gastric aspiration. The second tube is a simpler dual-lumen tube incorporating a gastric aspiration lumen and aspiration port together with a second jejunal infusion port. This tube will be applicable for use in the United Kingdom, Europe, and worldwide, where clinical practice is based on aspiration of gastric contents by simple syphonage.

Triple-Lumen Dual-Purpose Tube Figure 13A shows our 3-lumen dual-purpose air-vented assisted gastric aspiration and post–ligament of Treitz enteral feeding tube in situ. Note how the gastric aspiration port and the air vent exit port are positioned in the antral region of the stomach and the enteral feeding infusion port in the proximal jejunum, well distal to the ligament of Treitz. The tube can be introduced using a novel double-stylet introducer system, with the longer stylet being introduced into the enteral feeding infusion port following activation of the internal water-activated lubricant. The second, shorter introducer stylet is introduced via the gastric aspiration port, again following activation of the internal water activated lubricant.

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Table 1.  Comparison of Design Features of Nasogastric Tubes.

Characteristic Material Length, cm Outside diameter Aspiration/infusion lumen area, mm2 Aspiration/infusion port flow area, mm2

Salem Sumpa Gastric Dual-Lumen Gastric Decompression Tube

Dual-Purpose Dual-Lumen Gastric Decompression and Enteral Feeding Tube

Dual-Purpose Single-Lumen Rylesb SingleLumen Gastric Gastric Decompression and Decompression Tube Enteral Feeding Tube

Polyvinylchloride 122 19Fr 6.7 mm 6.0

Polyurethane 122 14Fr 4.7 mm 27.1

Polyvinylchloride 122 16Fr 5.3 mm 9.3

Polyurethane 122 14Fr 4.7 mm 9.3

6.0

54.8

9.3

263.0

a

Covidien (Mansfield, MA). Penine Health Care Ltd (Derby, UK).

b

Figure 14.  Side view of the dual-purpose double-lumen gastric aspiration and post–ligament of Treitz enteral feeding tube.

gastric aspiration port and the air vent exit port and their spatial relationships is similar to that described for our dual-purpose double-lumen nasogastric aspiration and enteral feeding tube described in Figures 9 and 10. The design of the enteral diet infusion port is similar to that of the aspiration/infusion port of our dual-purpose single-lumen nasogastric aspiration and enteral feeding tube depicted in Figure 11.

Double-Lumen Dual-Purpose Tube

Figure 13.  Triple-lumen dual-purpose gastric aspiration and post–ligament of Treitz jejunal enteral feeding tube. (A) A triplelumen tube in situ with the gastric aspiration and air vent exit ports sited within the antrum of the stomach. The enteral diet infusion port is situated in the proximal jejunum (J) distal to ligament of Treitz (LT) and pylorus (P). (B) A side view of the tube.

Figure 13B shows a side view of the triple-lumen dual-purpose tube. The superior lumen is the gastric aspiration lumen; one of the smaller inferior lumens is the air vent lumen, and the other is the enteral diet infusion lumen. The design of the

This tube is similar in design to the triple-lumen tube, except that it does not use an air vent lumen. The design of the gastric aspiration port and the enteral diet infusion port is exactly as depicted in Figures 11 and 12, which show the designs of the dual-purpose single-lumen gastric aspiration and enteral feeding tube. Figure 14 shows a side view of the tube. By virtue of being a dual-lumen tube, gastric aspiration and post–ligament of Treitz feeding can be achieved with a lower OD than can be achieved with the triple-lumen tube. Figure 15 shows drawings of a 16Fr Freka Trelumina dualpurpose gastric aspiration and jejunal feeding tube (Fresenius Kabi, Borkenberg, Germany). The successful use of this tube in ICU patients has been described.47 Note the presence of multiple small gastric aspiration ports and the very small distal jejunal infusion port. Table 2 compares the design features of the 16Fr Freka Trelumina dual-purpose tube with those of our proposed dual-purpose triple-lumen gastric decompression and jejunal enteral feeding tube. Note that for the same OD (16Fr), our tube will have a greater aspiration lumen area (7.7 vs

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Figure 15.  Drawing of the 16 Fr Freka Trelumina tube. Note the presence of multiple but small gastric aspiration ports and a tiny jejunal infusion port.

7.2 mm2) and feeding lumen area (4.1 vs 2.4 mm2). The gastric aspiration port area of our tube is over 6 times greater (72.7 vs 11.4 mm2) than that of the Freka Trelumina tube. Similarly, the jejunal infusion port area of our proposed tube will be substantially greater (101.0 vs 3.3 mm2) than that of the Freka Trelumina tube.

Discussion There have been a number of very important recent advances in the field of clinical nutrition support as far as patient care and outcomes are concerned. The first relates to the inclusion of early postoperative nutrition support as an essential modality in the multimodal ERAS protocols.20-26 The second is the realization that nutrition support is an important therapeutic intervention in ICU patients,48 particularly early after admission.1-5 The third relates to the widespread acceptance that wherever possible, the enteral route is preferred to the parenteral route.48 In postoperative surgical patients, there is often a period of delayed gastric emptying that requires gastric decompression. This is particularly so after major upper GI surgery. Delayed gastric emptying is also a common problem in ICU patients.6-10 Unless these patients are fed via postpylorically (and preferably post–ligament of Treitz)38 sited feeding tubes, nutrition support will be delayed while patients undergo gastric

decompression. Moreover, patients will often face a “tube change” as the design of current gastric decompression tubes (Salem Sump and Ryles) is not ideally suited to double up as nasogastric enteral feeding tubes. The current designs of our range of dual-purpose gastric decompression and enteral feeding tubes presented here will overcome many of these existing problems. All the tubes will be manufactured of PU. As discussed, this material has significant advantages over PVC. While “antikink” properties are maintained, for a given ID, significantly lower ODs can be achieved compared with PVC tubes, permitting greater patient comfort. Since the 1960s, it has been thought that multiple aspiration ports was the optimal design, and this has certainly been reflected in the designs of PVC nasogastric tubes (including Salem Sump and Ryles tubes) and also many PVC surgical drains. It was the polyurethane Dobbhoff (Covidien, Mansfield, MA) nasogastric feeding tube that was the first to successfully incorporate a single rather than multiple gastric aspiration ports. In our efforts to improve the design of nasogastric enteral feeding tubes,32-34 we took note of not only this but also the design of the Mahurkar (Covidien, Mansfield, MA) duallumen polyurethane intravenous (IV) hemodialysis catheter. This, in our view, was the first catheter to show that a single port was effective for inflow/outflow even in high-flow situations. Moreover, the inflow/outflow ports of this tube were “recessed,” thereby resisting occlusion during aspiration, and had no dead space to interfere with outflow. These admirable design properties were developed further, and long single, widened, smooth and curved edge ports with no dead space distal to the outflow port to trap mucus or curdled enteral diet were incorporated into the design of our nasogastric enteral feeding tube.32-34 In the first design,32,33 the sidewall was lowered and the aspiration/infusion port incorporated 106° of the circumference of the OD of the tube (Figure 7). As a consequence, gastric contents could be aspirated in 60% of occasions after tube insertion.32 Subsequently, in our second nasogastric feeding tube,34 the sidewalls were lowered further to incorporate 186° of the circumference of the OD of the tube, thereby increasing its area by (66.7%) (Figure 7). This increased the aspiration rate to 72%.34 In the port designs incorporated into the present range of dual-purpose nasogastric decompression and enteral feeding tubes, we anticipate that the ports that incorporate 214° of the circumference of the OD of the tube, thereby increasing port area by a further 41.1%, will result in aspiration rates approaching 100% (Figure 7). We believe that the 2 proposed dual-purpose gastric decompression and nasogastric feeding tubes should replace the existing Salem Sump (double-lumen) and Ryles (single-lumen) tubes. As far as the design of the 2 dual-purpose gastric decompression and post–ligament of Treitz jejunal feeding tubes is concerned, we have discussed the basic physiological

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Table 2.  Comparison of Design Features of 3-Lumen Proposed Gastric Aspiration and Jejunal Enteral Feeding Tube (Figure 12) and Freka Trelumina Tube (Figure 15). Feature

Dual Purpose Gastric Aspiration and Jejunal Enteral Feeding Tube

Material Gastric section proximal to gastric aspiration port   Length, cm  OD   Aspiration lumen area, mm2   Feeding lumen area, mm2   Aspiration port area, mm2 Jejunal lumen proximal to feeding port   Length, cm  OD   Feeding lumen area, mm2   Feeding lumen port area, mm2

Freka Trelumina Tube

Polyurethane

Polyurethane

90–106 (2 sizes) 18Fr (6.0 mm) 9.12 24.08 72.7

90 16Fr (5.3 mm) 7.15 2.411 11.4

40–120 9Fr (3.0 mm) 4.08 101.0

40 9Fr (3.0 mm) 2.411 3.3

OD, outer diameter.

principles on which there is a need to aspirate gastric contents during more distal “downstream” feeding.38,39,46 Both designs incorporate a gastric aspiration port, and one incorporates an air vent lumen and port to conform to U.S. “Salem Sump” protocols. The other is a double-lumen tube from which gastric contents will be aspirated by simple syphonage. It should be noted that we do not propose the design of a dual-purpose gastric decompression and postpyloric duodenal enteral feeding tube; both designs are based on the need for post–ligament of Treitz nasojejunal feeding. The reason for this is that while postpyloric tube feeding (almost certainly intraduodenal38) is capable of delivering higher proportions of estimated energy requirements in ICU patients compared with a gastric feeding and reduce gastric residual volumes,49 there is no evidence that mortality, incidence of new-onset pneumonia, or aspiration is reduced.49 ICU patients are known to exhibit proximal small bowel retroperistalsis.40 This is likely to be the reason why a significant proportion of postpyloric nasoduodenal sited feeding tubes spontaneously move back into the stomach.41 In contrast, properly sited post–ligament of Treitz nasojejunal tubes in ICU and postoperative patients have to be carefully taped in position to prevent caudal movement, indicating the likelihood that normal peristalsis is occurring at this site (D. B. A. Silk, personal communication 2014). We believe that it is only when patients are fed at this site and distal to the site of retroperistalsis that we will begin to see reductions in the incidence of aspiration, new pneumonia, and, it is hoped, mortality. As is the case with the dual-purpose gastric decompression and enteral feeding tubes, one of the jejunal tubes incorporates an air vent lumen and port to assist gastric aspiration, whereas the other is a doublelumen tube, with gastric aspiration performed by simple syphonage. All the design properties (OD, ID flow areas, and port areas) of the 2 tubes are superior to those of the available Freka Trelumina tube (Table 2). Recently, the Canadian Critical Care Nutrition guidelines have been updated.16 Aware that problems always exist in the

implementation of any guideline (D. B. A. Silk, personal communication 2014), the authors have conducted a biannual international audit of nutrition practices.50,51 In their most recent audit cycle involving 183 ICUs from 27 countries, it was found that only 12% of sites instituted small bowel feeding in patients not tolerating nasogastric feeding.16 Subsequently, a 26-item questionnaire was developed to define the barriers to implementation of the small bowel feeding recommendation. The top-ranked barrier was the delay and difficulties in obtaining small bowel access.16 Two design features of our post–ligament of Treitz nasojejunal feeding tubes will help to overcome these difficulties. The first relates to the proposal of the use of PU as the tube material that will lead to the production of relatively lower OD feeding tubes. The second relates to the proposed use of a double-stylet technique that we hope will facilitate the radiological positioning of the tubes. Currently, we are siting post–ligament of Treitz nasojejunal tubes by using combined endoscopic and radiological techniques (D. B. A. Silk, unpublished data, 2014). Certainly, our designs would be compatible with the use of this technique. Moreover, the designs could easily be adapted52,53 to the use of electromagnetic tracking techniques and the incorporation of the newly described IRIS technology.54 In summary, the application of our design technology adds a new dimension to dual-purpose gastric decompression and enteral feeding tubes. Not only do they have improved flow properties, but also the reduced ID to OD ratios will allow smaller OD tubes to be used that will be more comfortable for the patient. Moreover, their insertion will be more comfortable because of the use of water-activated lubricant.21,22,26 The novel outflow ports will aid aspiration and reduce the incidence of clogging (which is so time-consuming for the nursing staff). Furthermore, the employment of the novel aspiration/infusion ports will reduce the incidence of gastric mucosal suction injuries. We believe that, because of the problems that the use of the existing nasogastric decompression tubes leads to, surgeons are

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hesitating to employ the use until postoperative gastric problems occur. In turn, this requires the uncomfortable intubation of conscious patients. The use of the newly designed dual-purpose nasogastric tubes will not only overcome the above problems but will facilitate the use of early nutrition support that is becoming an accepted component of the new multimodal ERAS protocols, as well as in the management of the ICU patient. We need to mirror the advances in the nutrition management of our patients by including 21st-century gastric and gastrojejunal decompression and feeding tube design technology.

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