Adequate nutritional support plays a significant role in the outcome of critically ill patients 1. Furthermore, it is generally accepted that enteral feeding is preferable to parenteral feeding 234. Benefits of enteral feeding may include improvements in intestinal structure and function, prevention of bacterial translocation and infective complications with lower morbidity and cost 567. There is also evidence that early enteral feeding is beneficial and is recommended in a number of guidelines 138.

Delivery of nutrition via the nasogastric route may be problematic because a significant percentage of intensive care unit (ICU) patients suffer from bowel motility disorders leading to high gastric residual volumes (GRV) and under nutrition 9. Furthermore, there is a concern that gastric feeding may lead to pulmonary aspiration 1011. One potential solution to this problem is the insertion of transpyloric feeding tubes. Small bowel (SB) feeding has the theoretical benefit of improved nutrition and lower aspiration and pneumonia rates 810. However, complications such as misplacement of the small bore feeding tube into the lung with resultant pneumothorax are not rare 121314. In addition, insertion of post-pyloric tubes can be time-consuming and costly leading to delays in the initiation of feeds.

A number of post-pyloric insertion techniques have been described. The use of endoscopy or fluoroscopy has a relatively high success rate but is limited by availability, cost and often the need to transfer patients out of the ICU 1516171819. Furthermore, regional ICUs may not have ready access to endoscopy. In fact, Heyland and colleagues recommended post-pyloric feeding as a routine only in those institutions where it could be conveniently and hastily established 20. Several bedside techniques have been trialled with varying success 212223. Some studies have used dedicated physicians or dieticians to place post-pyloric tubes; however, providing 24-hour service may be unachievable. Training ICU nurses to insert SB tubes can overcome delays in feeding and potentially improve overall patient nutrition.

The aim of our study was to compare early gastric with post-pyloric feeding in ventilated, critically ill patients in a regional ICU. Our primary end-points included: the success rate of nurse initiated insertion of post-pyloric tubes, the time taken to insert the tube, time to reach goal feeds and total nutrition received over ICU stay as a proportion of the calculated ideal. As part of the secondary analysis, we compared complication rates between groups including incidence of ventilator associated pneumonia (VAP), GRV and mortality.

A single-site, prospective, randomised, controlled trial was conducted over a period of 12 months to compare gastric with post-pyloric feeding in ventilated, critically ill patients. The study setting was an eight-bed regional ICU. The Princess Alexandra Hospital Human Research Ethics Committee gave approval to conduct the investigation. Each patient or their next of kin provided written informed consent to participate.

All patients over 18 years of age admitted to ICU and expected to require mechanical ventilation for more then 24 hours were considered for inclusion. Exclusion criteria included ischaemic bowel, bowel obstruction, exacerbation of inflammatory bowel disease, acute variceal bleeding and patients deemed to be at high risk for anastomotic leak. Patients remained in the study until enteral feeding was ceased or they were discharged from the ICU.

Ventilated patients were randomly assigned to receive enteral feed via a nasogastric or a post-pyloric tube. Randomisation was achieved using a computer-generated random number sequence and a sealed opaque envelope technique. Patients were managed by a number of physicians, most of who were not involved in the study.

All enteric feeding tubes were placed by the bedside nurse. All participants irrespective of allocated group received a nasogastric tube (size 12, 14 or 16) positioned into the stomach. The post-pyloric group received a Corflo^®-Ultra Lite unweighted feeding tube (VIASYS MedSystems, Wheeling, IL, USA) - 10 FR 109 cm for patients less than 80 kg, or 10 FR 140 cm for patients greater than 80 kg inserted into either the duodenum or jejunum.

All patients received their feeding tubes as soon as possible. ICU nursing staff were trained by the principle researchers or the ICU clinical facilitator to insert the post-pyloric tubes using a blind insertion technique and were required to pass a competency test 24.

A total of 108 patients were randomised, 57 in the gastric group and 51 in the post-pyloric group (Table 1). Of the 108 participants randomised, four were randomised in error and were excluded and two required total parenteral nutrition (TPN) support. Data from 104 patients was analysed. There were 10 patients in the post-pyloric group who did not receive a post-pyloric tube and four patients in the gastric group that did receive a post-pyloric tube. Of the patients in the post-pyloric group who did not receive a post-pyloric tube, 10 were attempted without success, giving an overall success rate of 80%. APACHE II scores for the successful and unsuccessful groups were similar. However, there was a significant difference between the GRV of the group where a post-pyloric tube could not be passed, ie 297 (232 to 442) ml/day compared with 126 (42 to 284) ml/day in the successful group (P = 0.027).

On intent-to-treat analysis, there was no difference in the length of stay or ventilator days between groups (Table 2). In terms of the primary outcomes the gastric group was quicker to initiate feed as compared with post-pyloric group. The time to reach target feeds from admission was also faster in the gastric group although time to goal from initiation of feeds was similar suggesting the difference is related to the procedure itself rather than feeding intolerance. The average daily energy deficit was lower in the gastric group. There was evidence that a delay in initiation of feeding contributed to this result because the deficits on day one were higher in the post-pyloric group but not significantly so.

Baseline characteristics demonstrated that the post-pyloric group were sicker compared with the gastric group (Table 1). The APACHE II scores were higher and there was an increased incidence of diabetes three (6%) compared with six (12%), acute renal failure nine (17%) compared with 12 (24%) and vasopressor use 20 (37%) compared with 27 (54%) in the post-pyloric group. Higher APACHE II scores were associated with higher energy and protein deficits. Adjusting for these discrepancies led to a non-significant difference in energy deficit between the two groups (Table 3).

Complication rates were similar between groups. Average daily GRV were similar although there was a trend toward higher residuals in the post-pyloric group: 190 (55 to 301) ml compared with 111 (43 to 275)ml (P = 0.3) in the gastric group. There was also evidence that higher APACHE II score was associated with increased daily average nasogastric aspirate (by 3% for each unit increase in APACHE II score). A comparison of average daily GRV by position of tube (duodenum versus jejunum) showed no difference (P = 0.96). In terms of VAP, there were 16 events in total, 5 in the post-pyloric group and 11 in the gastric group (P = 0.18).

Drugs that affect gastric motility were recorded. Number of days on fentanyl, morphine, metaclopramide or erythromycin was similar in the two groups: 2 (0 to 5.5) days in the gastric group; 2 (0 to 4) days in post-pyloric group (P = 0.7). Number of days on either metaclopramide or erythromycin was similar in the two groups: 0 (0 to 4.5) days in the gastric group; 0 (0 to 2) days in the post-pyloric group (P = 0.6). The number of deaths were 5 in the gastric group versus 11 in the pyloric group giving an odds ratio of 2.86 (95% confidence interval (CI) = 0.92 to 8.89, P = 0.069). When adjusted for apache score the odds ratio is 2.15 (95% CI = 0.65 to 7.07, P = 0.20).

A per-protocol analysis was performed in order to correct for failure of insertion of post-pyloric tube (Tables 4 and 5). Patients who actually received a post-pyloric tube (n = 44) were compared with patients who did not (n = 60). Nutritional differences demonstrated during the intent-to-treat analysis disappeared when examined on a per-protocol basis although gastric feeding still showed a trend toward higher average nutritional intake.

The effectiveness of post-pyloric as compared with gastric feeding has been examined in a number of studies. In general, the results have largely been equivocal. Both Ho and colleagues and Marik and colleagues confirmed this in two meta-analyses 3031. Individual studies have produced varying results. Montejo and colleagues found calorie intake to be similar between the nasogastric and nasojejunal group 11. On the other hand, Kearns and colleagues found the post-pyloric route supplied more calories while Neumann and colleagues found the opposite 3233. With the high incidence of gastroparesis present in ICU patients (up to 50%) it seems counterintuitive that gastric feeding can be as successful if not more than post-pyloric feeding 3435. Several reasons have been proposed to explain this observation including the longer time taken to insertion of post-pyloric tubes and therefore, later onset of feeding, the potential for more frequent tube related complications in patients fed via the SB (occlusion, dislodgment, accidental withdrawal) and tube position (i.e. duodenal versus jejunal).

We found that patients fed via a nasogastric tube had a shorter time to initiation of feed and time to reach goal feed and lower average daily energy deficit as compared with the post-pyloric group. Although statistically significant, the difference in energy deficit in absolute terms was only 6%, which may not be clinically significant. Our findings compared favourably to other studies where percentage of daily nutritional targets delivered varied from 56 to 80% and time to achieve full nutritional targets varied from 23 to 43 hours in the post-pyloric group 113233363738. This was despite the fact that the APACHE II scores in our study were higher than in previous studies.

There are several possible explanations for the observed differences. Firstly, in 20% of cases, post-pyloric tube insertion was unsuccessful and these patients were fed via the nasogastric route (see below). As analysis was by intent to treat, they were analysed in the post-pyloric group. To adjust for these cases, we performed a protocol-based analysis, which found the groups to be equivalent (although the trend favoured the gastric fed patients). Secondly, there was a delay in reaching goal feeds in the post-pyloric compared with the gastric group, which although not statistically significant may have influenced total nutritional intake. Thirdly, previous studies have noted a greater incidence of tube displacement in post-pyloric fed patients leading to frequent interruption of feeding.

Lastly, the effect of severity of illness on the gastrointestinal system is variable 3439. Although we know of no prospective studies linking severity of illness to the ability to absorb feeds, Nguyen and colleagues found that APACHE II score was associated with delayed gastric emptying 39. The APACHE II scores of our patients were higher then most prior studies suggesting that they were sicker. We also found a significant difference in APACHE II scores between the groups (Table 1). Once results were adjusted for APACHE II score, the difference in nutritional outcomes was not apparent.

A principle motivation for the use of SB feeding is the high incidence of gastroparesis in ICU populations (50% ventilated and 80% head injured) 3540. There are numerous potential reasons for this including abdominal surgery, haemodynamic instability, burns, electrolyte abnormalities, fluid overload and the use of vasoactive drugs or analgo-sedation and it is thought that by bypassing the stomach, feeding tolerance can be improved 4142. Most ICU feeding studies use GRV as a surrogate for gastric emptying and motility. The utility and significance of this measurement is controversial and depends on a number of factors. Indeed, the relation between GRV and gastric emptying is weak 4344. The level of aspirate considered excessive is largely arbitrary and can vary between 150 and 400 ml 45. Furthermore, up to 25% of patients with GRV more than 150 ml have a normal gastric emptying and can continue on prokinetics.

Neither Ho and colleagues nor Marik and colleagues reported on GRV in their analyses 3031. Many individual studies report the number of episodes of high GRV rather than the absolute amount. Montejo and colleagues found that up to 50% of patients had high GRV in the gastric group compared with 2% in the post-pyloric group 11. Neumann and colleagues, however, found similar results between groups 33. Differences in definitions of high GRV limit comparison between studies. Montejo and colleagues considered a GRV of 300 ml significant whereas, Neumann and colleagues used 200 ml as a cut off. A high incidence of GRV is considered important because it may increase the risk of aspiration and VAP. In our study we reported on average GRV and found no significant difference, although the GRV in the post-pyloric group was higher. This may partially be explained by the higher APACHE II score and therefore, increased likelihood of gastroparesis in that group. Furthermore, some tubes in the post-pyloric group were in the duodenum rather then jejunum. However, when stratified by tube position, there was no difference in GRV. These findings were in keeping with Heyland and colleagues who similarly failed to find a relation between SB tube position and amount of reflux 10. Dysmotility in critically ill patients is known to affect the small bowel, and may lead to significant reflux.

Although not statistically significant the mortality rate was higher in the post-pyloric group. The reasons for this are not obvious. As noted, the APACHE II scores were higher in post-pyloric group but even correcting for this, the odds ratio for death was 2.15. All deaths were reviewed and reported to the ethics review committee. No evidence could be found to link the insertion of post-pyloric tubes to the deaths. Furthermore, the mortality rate of 20% in the post-pyloric group was not unexpected given their high APACHE II scores. We therefore do not believe there is any evidence that the insertion of post-pyloric tubes contributed to the deaths of any patient.

Other major complications from post-pyloric tube insertion were rare and we had no significant episodes. We examined the incidence of VAP because there is some evidence that SB feeding may be beneficial. Although this seems a reasonable assumption, there is little strong evidence from the literature to support it 10303246. We found a similar incidence of VAP between the groups although there was a trend toward a lower incidence in the post-pyloric group. Our numbers were insufficient to reach statistical significance. The diagnosis of VAP is controversial and diagnostic criteria vary between studies. We did not examine the incidence of aspiration.

Endoscopic guided post-pyloric tube insertion is costly, is not universally available and can lead to significant delays in initiation of feeds. In fact, delays of more then 24 hours are the rule 113347. The mean time to reach goal feed in the studies reviewed by Ho and colleagues ranged between 23 and 43 hours 30. We demonstrated that by employing a nurse-initiated bedside insertion method and an aggressive approach to enteral feeding, the time to reach goal feeds can be reduced, as compared with other studies. Our success rate of 80% compares well with other techniques although some have reported higher insertion rates 244849. Other non-invasive methods have similar outcomes 50515253. In most instances, the post-pyloric tube was inserted on the first attempt. Despite reports of a high incidence of malposition, there were no episodes of lung insertion.

This study has several limitations. Firstly, doctors were not blinded to treatment group. Secondly, nurses with varying experience were responsible for insertion of post-pyloric tubes. This was intentionally done to reflect the day to day practice of the ICU. Thirdly, there was a 20% failure for insertion of post-pyloric tubes. The blind insertion technique was chosen because access to endoscopic insertion is limited and would have significantly delayed initiation of feeds. This reflects our current practice in the ICU. Fourthly, difference in APACHE II scores suggest the post-pyloric group contained sicker patients, which may have influenced feeding and outcome. And finally, our patient population is largely medical and therefore, may not represent findings in a surgical group of patients.

Our data largely support the findings of previous meta-analyses, that early post-pyloric feeding is not superior to gastric feeding in the medical ICU population. Whether post-pyloric feeding can be effective in selected patients such as those unable to tolerate gastric feeding is unclear. We also demonstrated that bedside nursing staff can successfully and safely place post-pyloric tubes in the majority of patients, potentially reducing delays in the initiation of feeds.

• Early post-pyloric feeding is no more effective than early gastric feeding.

• Blind insertion of naso-jejunal feeding tubes by bedside nursing staff is highly effective.

APACHE II: Acute Physiology and Chronic Health Evaluation II; CI: confidence interval; GRV: gastric residual volumes; ICU: intensive care unit; SB: small bowel; TPN: total parenteral nutrition; VAP: ventilator associated pneumonia.

The authors declare that they have no competing interests.

HW and KS conceived, managed study and drafted manuscript. AR supplied nutritional data and contributed to manuscript. KT participated in its design and coordination and helped to draft the manuscript. MJ participated in the design of the study and performed the statistical analysis. All authors read and approved the final manuscript.