pH and concentrations of pepsin and trypsin in feeding tube aspirates as predictors of tube placement

Complication rates associated with nasoesophageal versus nasogastric feeding tube placement in dogs and cats: a randomised controlled trial

OBJECTIVES

To determine the rate of accidental placement of nasoenteric tubes into the respiratory tract. To compare the methods of checking correct tube placement. To compare the complication rates between nasoesophageal and nasogastric tubes.

MATERIALS AND METHODS

Animals requiring nasoenteric feeding tubes were prospectively randomised to have either nasoesophageal or nasogastric tube placement. Various techniques for assessing tube position were compared with thoracic radiographic findings. Complications during placement and use were recorded.

RESULTS

Ninety-seven animals (82 dogs and 15 cats) were studied. The tube was misplaced into the respiratory tract in three (3.1%) cases. No technique for checking placement was completely concordant with radiography but the presence of negative pressure at the thoracic inlet during placement was consistent with the presence of the tube in the oesophagus in 86.2% cases, while capnography can be considered to confirm tracheal placement. The overall rate of complications during tube placement was 25.8%, with mostly minor clinical complications reported. There was no significant difference in the new-onset regurgitation/vomiting rate, or complications while the tube was in situ between the nasoesophageal and nasogastric groups.

CLINICAL SIGNIFICANCE

Misplacement of nasoenteric tubes is uncommon but a consistent alternative test to radiography for checking correct nasoenteric tube placement was not demonstrated. The choice of placement of either a nasoesophageal or nasogastric tube should be guided by clinician preference, and clients should be warned about possible complications during placement and while the nasoenteric tube is in situ.

Purine nucleosidase (PNase) activity, probiotics potential, and food applicability of a newly-isolated Levilactobacillus brevis LAB42

Hyperuricemia, a condition characterized by elevated levels of uric acid in the blood, is known as a risk factor for gout disease. In this study, we isolated a total of 72 MRS-grown colonies and evaluated their purine nucleosidase (PNase) activity. Among the isolated bacteria, Levilactobacillus (L.) brevis LAB42 displayed the highest PNase activity. Our findings also indicate that PNase activity can vary among lactic acid bacterial strains and during different growth phases. Based on the kinetics study, LAB42 consistently exhibits the highest PNase activity. Due to its ability to attach to Caco-2 cells and its resistance to acidic environments and bile exposure, L. brevis LAB42 was chosen for further studies and showed that with the right combination of additives, it has the potential to be an appropriate starter for milk fermentation.

Microfluidic-Assisted Production of Gastro-Resistant Active-Targeted Diatomite Nanoparticles for the Local Release of Galunisertib in Metastatic Colorectal Cancer Cells

The oral route is highly desirable for colorectal cancer (CRC) treatment because it allows concentrating the drug in the colon and achieving a localized effect. However, orally administered drugs are often metabolized in the liver, resulting in reduced efficacy and the need for higher doses. Nanoparticle-based drug delivery systems can be engineered to prevent the diffusion of the drug in the stomach, addressing the release at the target site, and enhancing the efficacy of the delivered drug. Here, an orally administrable galunisertib delivery system is developed with gelatin-covered diatomite nanoparticles targeting the ligand 1-cell adhesion molecule (L1-CAM) on metastatic cells, and further encapsulated in an enteric matrix by microfluidics. The gastro-resistant polymer protects the nanoparticles from the action of the digestive enzymes and allows for a sustained release of galunisertib at the intestinal pH. The efficacy of antibody-antigen interactions to drive the internalization of nanoparticles in the targeted cells is investigated in CRC cells expressing abnormal (SW620) or basal levels (Caco-2, HT29-MTX) of L1-CAM. The combination of local drug release and active targeting enhances the effect of the delivered galunisertib, which inhibits the migration of the SW620 cells with greater efficiency compared to the free drug.

RAGE-Dependent Effect of Exogenous Methylglyoxal Intake on Lung Biomechanics in Mice

Methylglyoxal (MG) is a known highly reactive dicarbonyl and precursor to free radicals and advanced glycation end-products (AGEs). It is discussed to be involved in tissue aging and in the pathogenesis of different degenerative diseases. The effect of long-term oral administration of MG, simulating dietary MG intake, on the lung biomechanics of wild type (WT) and receptor for advanced glycation end-products knockout (RAGE-KO) mice was studied using an ex vivo ventilation system starting at the age of 6 months and after feeding for 6 and 12 months with MG. Our results showed that MG was taken up in the circulation and efficiently excreted with urine. The amount of free urinary MG measured after 12 months of feeding was lowered. After 12 months feeding, a significant airway resistance increase accompanied by a decrease of the maximal inspiratory airflow was observed in WT animals. No effect of MG in lung function of RAGE-KO mice could be detected. Despite the evidence that MG entered the systemic circulation, no MG-derived AGE accumulation was detected in the lung lysates in dependency on MG-feeding. Our data indicate that the short-term feeding of MG has little effect in vivo. Only after long-term treatment was MG secretion reduced, leading to tissue impairment.

Assessing protein digestibility in allergenicity risk assessment: A comparison of in silico and high throughput in vitro gastric digestion assays

The susceptibility of a novel food protein to digestion in the pepsin resistance test is widely used to inform the allergenicity risk assessment process. However, it does not model the variation in the intragastric environment found in vivo. Consequently a 96-well plate format in vitro gastric digestion protocol has been developed with a high and low pepsin activity test executed at pH 1.2, 2.5, 5.5 and 6.5. It was used to analyse seven allergens (from milk, egg, peach and peanut) and two non-allergens (cytochrome c and zein). Digestion was monitored using SDS-PAGE and densitometry. In silico predictions were not confirmed experimentally for most of the proteins studied. Proteins were ranked according to half-life and showed susceptibility to digestion was related to the stability of protein structure and protein solubility rather than allergenicity per se. Highly digestible proteins, such as β-casein and Ara h 1, generated abundant resistant fragments Mr > 3.5 kDa in the low pepsin activity test which could be immunologically significant within the context of allergenicity risk assessment for susceptible groups such as infants. The high- and low pepsin activity tests used in this study provided complementary data to support allergenicity risk assessment and used only 10 mg protein.

Nasogastric tube in mechanical ventilated patients: ETCO2 and pH measuring to confirm correct placement. A pilot study

Introduction

Nasogastric tube (NGT) placement is a procedure commonly performed in mechanically ventilated (MV) patients. Chest X-Ray is the diagnostic gold-standard to confirm its correct placement, with the downsides of requiring MV patients’ mobilization and of intrinsic actinic risk. Other potential methods to confirm NGT placement have shown lower accuracy compared to chest X-ray; end-tidal CO₂ (ETCO₂) and pH analysis have already been singularly investigated as an alternative to the gold standard. Aim of this study was to determine threshold values in ETCO₂ and pH measurement at which correct NGT positioning can be confirmed with the highest accuracy.

Materials & methods

This was a prospective, multicenter, observational trial; a continuous cohort of eligible patients was allocated with site into two arms. Patients underwent general anesthesia, orotracheal intubation and MV; in the first and second group we respectively assessed the difference between tracheal and esophageal ETCO₂ and between esophageal and gastric pH values.

Results

From November 2020 to March 2021, 85 consecutive patients were enrolled: 40 in the ETCO₂group and 45 in the pH group. The ETCO₂ ROC analysis for predicting NGT tracheal misplacement demonstrated an optimal ETCO₂ cutoff value of 25.5 mmHg, with both sensitivity and specificity reaching 1.0 (AUC 1.0, p < 0.001). The pH ROC analysis for predicting NGT correct gastric placement resulted in an optimal pH cutoff value of 4.25, with mild diagnostic accuracy (AUC 0.79, p < 0.001).

Discussion

In patients receiving MV, ETCO₂ and pH measurements respectively identified incorrect and correct NGT placement, allowing the identification of threshold values potentially able to improve correct NGT positioning.

Trial registration

NCT03934515 (www.clinicaltrials.gov).

Placement of Nasogastric Feeding Tube and Postinsertion Care Review

Insertion and postinsertion care of enteral nasogastric feeding tubes are common procedures in the United States, with more than 1.2 million temporary nasogastric feeding tubes inserted annually. Although there are some evidence-based practice guidelines and recommendations for care of these tubes, variation in practice still exists. Additional research is needed to determine the best methodology for insertion and confirmation of nasogastric feeding tubes. Routine competency and training on feeding tube insertion, enteral nutrition, and postinsertion care is crucial to prevent patient safety events. Variable results have been reported with different technologies; however, radiographic confirmation remains the criterion standard. It is important that health care institutions develop standardized procedures for insertion and confirmation on the basis of evidence-based practices to minimize risks and complications from temporary nasogastric feeding tubes.

Nurse-performed ultrasound assessment of gastric residual volume and enteral nasogastric tube placement in the general intensive care unit

OBJECTIVE

Ultrasonography is an essential imaging modality in the critical care population and has been increasingly utilized to check gastric residual volume . Various studies have shown that intensive care unit nurses untrained in ultrasound can easily be trained in its accurate interpretation. We prospectively analyzed nurse-performed repeated measurements of gastric residual volume and nasogastric tube positioning via an ultrasound technique in the intensive care unit.

DESIGN

This was a single-center, cross-sectional prospective study. Four intensive care unit nurses, evenly divided into two groups (teams A and B), underwent four hours of formal ultrasound training by three critical care staff physicians. The trained nurses provided bedside ultrasound assessments of gastric residual volume and nasogastric tube positioning which were compared to a standard protocol of syringe aspiration.

RESULTS

Ninety patients were recruited to the study. Four measurements per patient were performed, for a total of 360 assessments. The ultrasound gastric residual volume assessments were correlated with the syringe aspiration protocol and demonstrated high Intraclass Correlation Coefficient rates of 0.814 (0.61-0.92) for team A and 0.85 (0.58-0.91) for team B. Nasogastric tube placement was successfully and independently verified by ultrasound in most of the critically ill patients (78% of team A and 70% of team B). The comparative ultrasound assessments of tube positioning demonstrated good correlation of 0.733 (0.51-0.88) between each team's two independent observers.

CONCLUSION

Our study demonstrated a strong correlation between US utilization for assessment of gastric residual volume and nasogastric tube positioning and standard protocol methods, suggesting it is a safe, simple and effective practice for intensive care unit nurses.

Pepsin A in Tracheal Secretions From Patients Receiving Mechanical Ventilation

BACKGROUND

In patients in the intensive care unit (ICU) receiving mechanical ventilation, aspiration of gastric contents may lead to ventilator-associated events and other adverse outcomes. Pepsin in pulmonary secretions is a biomarker of microaspiration of gastric contents.

OBJECTIVES

To evaluate the association between tracheal pepsin A and clinical outcomes related to ventilator use.

METHODS

A subset of 297 patients from a larger clinical trial on aspiration of oral secretions in adults receiving mechanical ventilation consented to have pepsin A measured in their tracheal aspirate samples. A concentration ≥6.25 ng/mL indicated a positive result. Abundant microaspiration was defined as pepsin A in ≥30% of samples. Statistical analyses included analysis of variance, analysis of covariance, and χ2 tests.

RESULTS

Most patients were White men, mean age 59.7 (SD, 18.8) years. Microaspiration was found in 43.8% of patients (n = 130), with abundant microaspiration detected in 17.5% (n = 52). After acuity was controlled for, patients with tracheal pepsin A had a longer mechanical ventilation duration (155 vs 104 hours, P < .001) and ICU stay (9.9 vs 8.2 days, P = .04), but not a longer hospital stay.

CONCLUSIONS

Microaspiration of gastric contents occurred in nearly half of patients and was associated with a longer duration of mechanical ventilation and a longer stay in the ICU. Additional preventative interventions beyond backrest elevation, oropharyngeal suctioning, and management of endotracheal tube cuff pressure may be needed. Also, the timing of pepsin measurements to capture all microaspiration events requires additional exploration.

Outer Membrane Vesicles of Vibrio cholerae Protect and Deliver Active Cholera Toxin to Host Cells via Porin-Dependent Uptake

Outer membrane vesicles (OMVs) are an emerging research field due to their multifactorial composition and involvement in interspecies and intraspecies communication. Recent studies indicate that vesicle release by Gram-negative bacterial pathogens is increased during in vivo colonization, as exemplified by the facultative human pathogen Vibrio cholerae upon oral ingestion by the host. In this study, we investigate the fate of OMVs produced by the Gram-negative facultative pathogen V. cholerae. We show that vesicles produced by the clinically relevant El Tor biotype are readily taken up by human intestinal cell lines. We identify outer membrane porins of V. cholerae, i.e., OmpU and OmpT, as the required surface effectors on OMVs for cellular uptake, and we pinpoint the uptake mechanism as caveolin-mediated endocytosis. Furthermore, we show that OMVs derived from V. cholerae grown under virulence-inducing conditions act as potent vehicles for delivery of bioactive cholera toxin to intestinal epithelial cells. In contrast to free cholera toxin secreted via the type II secretion system, OMV-associated cholera toxin is protected from degradation by intestinal proteases. Taken together, these data show that OMV-associated cholera toxin can sustain longer periods in the intestinal tract and preserve toxin effects, as indicated by a prolonged increase of cAMP levels in the intestinal tissue. IMPORTANCE Cholera is still a massive global health burden because it causes large outbreaks with millions of infections and thousands of deaths every year. Several studies have contributed to the knowledge of this pathogen, although key parts are still missing. We aim to broaden our understanding of Vibrio cholerae infections, virulence, and toxicity by drawing attention to the involvement of OMVs in these core processes. Upon host entry, V. cholerae increases secretion of OMVs, which can carry the main virulence factor, cholera toxin, to distant host intestinal cells. We show that specific outer membrane porins on the vesicle surface mediate endocytosis of the vesicles into intestinal cells. With protection by the vesicles, cholera toxin activity endures even in the presence of intestinal proteases. It is tempting to hypothesize that the extended half-life of vesicle-associated cholera toxin allows it to target host cells distant from the primary colonization sites.

Nasogastric Tube Feeding in Older Patients: A Review of Current Practice and Challenges Faced

Nasogastric tube feeding is an essential way of delivering enteral nutrition when the oral route is insufficient or unsafe. Malnutrition is recognised as a reversible factor for sarcopenia and frailty. It is therefore crucial that malnutrition is treated in older inpatients who have dysphagia and require enteral nutrition. Despite five National Patient Safety Alerts since 2005, “Never Events” related to nasogastric feeding persist. In addition to placement errors, current practice often leads to delays in feeding, which subsequently result in worse patient outcomes. It is crucial that tube placement is confirmed accurately and in a timely way. Medical advancements in this area have been slow to find a solution which meets this need. In this paper, we provide an updated review on the current use of feeding nasogastric tubes in the older population, the issues associated with confirming correct placement, and innovative solutions for improving safety and outcomes in older patients.

Protease-stable DARPins as promising oral therapeutics

Clostridioides difficile is an enteric bacterium whose exotoxins, TcdA and TcdB, inactivate small GTPases within the host cells, leading to bloody diarrhea. In prior work, our group engineered a panel of potent TcdB-neutralizing designed ankyrin repeat proteins (DARPin) as oral therapeutics against C. difficile infection. However, all these DARPins are highly susceptible to digestion by gut-resident proteases, i.e. trypsin and chymotrypsin. Close evaluation of the protein sequence revealed a large abundance of positively charged and aromatic residues in the DARPin scaffold. In this study, we significantly improved the protease stability of one of the DARPins, 1.4E, via protein engineering. Unlike 1.4E, whose anti-TcdB EC50 increased >83-fold after 1-hour incubation with trypsin (1 mg/ml) or chymotrypsin (0.5 mg/ml), the best progenies-T10-2 and T10b-exhibit similar anti-TcdB potency as their parent in PBS regardless of protease treatment. The superior protease stability of T10-2 and T10b is attributed to the removal of nearly all positively charged and aromatic residues except those directly engaged in target binding. Furthermore, T10-2 was found to retain significant toxin-neutralization ability in ex vivo cecum fluid and can be easily detected in mouse fecal samples upon oral administration. Both T10-2 and T10b enjoy a high thermo- and chemo-stability and can be expressed very efficiently in Escherichia coli (>100 mg/l in shaker flasks). We believe that, in additional to their potential as oral therapeutics against C. difficile infection, T10-2 and T10b can also serve as a new generation DARPin scaffold with superior protease stability.

How a Fragment Draws Attention to Selectivity Discriminating Features between the Related Proteases Trypsin and Thrombin

In the S₁ pocket, the serine proteases thrombin and trypsin commonly feature Asp189 and a Ala190Ser and Glu192Gln exchange. Nevertheless, thrombin cleaves peptide chains solely after Arg, and trypsin after Lys and Arg. Thrombin exhibits a Na+-binding site next to Asp189, which is missing in trypsin. The fragment benzylamine shows direct H-bonding to Asp189 in trypsin, while in thrombin, it forms an H-bond to Glu192. A series of fragments and expanded ligands were studied against both enzymes and mutated variants by crystallography and ITC. The selectivity-determining features of both S₁ pockets are difficult to assign to one dominating factor. The Ala190Ser and Glu192Gln replacements may be regarded as highly conserved as no structural and affinity changes are observed between both proteases. With respect to charge distribution, Glu192, together with the thrombin-specific sodium ion, helps in creating an electrostatic gradient across the S₁ pocket. This feature is definitely absent in trypsin but important for selectivity along with solvation-pattern differences in the S₁ pocket.

Pneumothorax from Intrapleural Placement of a Nasogastric Tube

Nasogastric tube insertion is a commonly performed procedure that can be associated with significant morbidity and even mortality. There is no universally accepted technique to confirm correct placement. Most confirmatory methods are performed after placement, therefore misplacement and potential complications may have already occurred. We report a case where a commonly used bedside confirmatory test gave false reassurance that the nasogastric tube was properly positioned, but a plain chest X-ray revealed a massive pneumothorax due to inadvertent intrapleural placement of the tube. Due to the deficiencies of traditional confirmatory bedside techniques, and the limitations of modern and more sophisticated confirmatory methods, the plain chest X-ray remains the gold standard test to confirm correct nasogastric tube placement. We appraise the methods commonly employed to confirm nasogastric tube placement, and discuss factors that may increase the risk of misplacement.

Comparison of Neonatal Nursing Practices for Determining Feeding Tube Insertion Length and Verifying Gastric Placement With Current Best Evidence

BACKGROUND

Oral-nasogastric feeding tubes (FTs) are often malpositioned, placing infants at risk for complications. Confusion exists regarding the accuracy of methods to determine FT insertion length and verify gastric FT placement, and it is unknown whether evidence-based methods are used by neonatal nurses.

PURPOSE

To compare individual and unit-based neonatal nursing practices regarding methods used to determine FT insertion length and verify gastric FT placement.

METHODS

Neonatal nurses were surveyed about individual and unit-based practices regarding methods used to determine FT insertion length and verify gastric FT placement in infants in the neonatal intensive care unit.

RESULTS

Sixty neonatal nurses completed the survey, with 63% utilizing the nose-ear-midway to the umbilicus method, which was included in 50% of protocols and is associated with up to a 90% accuracy rate. Although it has an unacceptably high inaccuracy rate, the nose-to-ear-to-xiphoid method was used by 32% of nurses and recommended in 30% of protocols. To verify gastric FT placement, 98% of nurses used auscultation of a whoosh sound and 83% used aspiration of gastric contents. Neither verification method is supported by evidence or recommended for use.

IMPLICATIONS FOR PRACTICE

A lack of consistency exists between nursing practice and evidence-based methods.

IMPLICATIONS FOR RESEARCH

Research is needed to determine more accurate and reliable ways to determine FT insertion depth and verify gastric FT placement in neonates.

Study to determine the likely accuracy of pH testing to confirm nasogastric tube placement

Objective

To establish the likely accuracy of pH testing to identify gastric aspirates at different pH cut-offs to confirm nasogastric tube placement.

Methods

This prospective observational study included a convenience sample of adult patients who had two (one fresh and one frozen) gastric and oesophageal samples taken during gastroscopy or two bronchial and saliva samples taken during bronchoscopy. The degree of observer agreement for the pH of fresh and frozen samples was indicted by kappa (k) statistics. The sensitivities and specificities at pH ≤5.5 and the area under the receiver operating characteristics (ROC) curve at different pH cut-offs were calculated to identify gastric and non-gastric aspirates.

Results

Ninety-seven patients had a gastroscopy, 106 a bronchoscopy. There was complete agreement between observers in 57/92 (62%) of the paired fresh and frozen gastric samples (k=0.496, 95% CI 0.364 to 0.627). The sensitivity of a pH ≤5.5 to correctly identify gastric samples was 68% (95% CI 57 to 77) and the specificity was 79% (95% CI 74 to 84). The overall accuracy to correctly classify samples was between 76% and 77%, regardless of whether patients were taking antacids or not. The area under the ROC curve at different pH cut-offs was 0.74.

Conclusion

The diagnostic accuracy of pH ≤5.5 to differentiate gastric from non-gastric samples was low, regardless of whether patients were taking antacids or not. Due to the limited accuracy of the pH sticks and the operators’ ability to differentiate colorimetric results, there is an urgent need to identify more accurate and safer methods to confirm correct placement of nasogastric tubes.

The Fate of Major Royal Jelly Proteins during Proteolytic Digestion in the Human Gastrointestinal Tract

Royal jelly (RJ) is a beehive product with a complex composition, major royal jelly proteins (MRJPs) being the most abundant proteins. Cell culture and animal studies suggest various biological activities for the full-length/native MRJPs. In the field of apitherapy, it is assumed that MRJPs can positively affect human health. However, whenever RJ is administered orally, the availability for assimilation in the gastrointestinal tract is a prerequisite for MRJPs to have any effect on humans. We here show that MRJPs vary in resistance to pepsin digestion with MRJP2 being most stable and still present as full-length protein after 24 h of digestion. In the intestinal phase, using trypsin and chymotrypsin, MRJPs are rapidly digested with MRJP2 again showing longest stability (40 min), suggesting that MRJPs can reach the small intestine as full-length proteins but then have to be resorbed quickly if full-length proteins are to fulfill any biological activity.

Nasogastric tube insertion in anaesthetised, intubated adult patients: A comparison between three techniques

Background and Aims:

The existence of several methods for proper placement of nasogastric tube (NGT) and introduction of various novel methods day-by-day indicates that no method is perfect or universally accepted. However, the quest for the best is still on. Application of cold in various forms to stiffen the NGT has been tested inconsistently over the last three decades. In the recent past, frozen NGT has been compared only with conventional methods. Hence, the present study was designed to evaluate the efficacy of the frozen technique in comparison with conventional and reverse Sellick's manoeuvre.

Methods:

A total of 195 adult patients undergoing abdominal surgeries in anaesthetised and intubated state requiring NGT insertion were allocated to three groups to have their NGT placement using either the conventional method (Group A) or using frozen NGT (Group B) or applying reverse Sellick's manoeuvre (Group C). The number of successful placements of NGT within two attempts, procedure time, and incidences of adverse events were noted.

Results:

The highest success rate regarding the successful placement of NGT was observed using reverse Sellick's manoeuvre (95.2%), closely followed by the frozen NGT technique (84.6%) in comparison with conventional method (69.2%). The procedure time was the least with reverse Sellick's manoeuvre (31.5 ± 9.5 s) compared with conventional (42.2 ± 21.4 s) and frozen technique (42.1 ± 13.2 s).

Conclusion:

Nasogastric tube insertion using reverse Sellick's manoeuvre shows the highest success rate and having the least adverse events among the compared three methods in anaesthetised, intubated adult patients.

Optimized conditions for the in vitro excystment of Calicophoron daubneyi metacercariae

Paramphistomosis, caused by Calicophoron daubneyi, is an emerging infection of ruminants throughout Western Europe. Despite its prevalence, many questions remain regarding the basic biology of this parasite and how it interacts with its host. Consequently, there is a need to develop methods to study C. daubneyi in vitro to improve our understanding of rumen fluke biology. Towards this, we aimed to identify a suitable protocol for in vitro excystment of C. daubneyi metacercariae. Six methods that have been used to excyst metacercariae from a number of trematode species were tested with C. daubneyi metacercariae. Three of these achieved an average of >50% excystment whilst one method, which included an acid-pepsin treatment, incubation in reducing conditions and an alkaline/bile salt solution to activate the larvae, consistently gave >80% excystment. The latter protocol also showed no detrimental effect on the motility of newly excysted juvenile (NEJ) parasites when observed for up to 24 h in RPMI 1640 medium post-excystment. The successful production of C. daubneyi NEJs in vitro is a significant step forward, and will enable the discovery of infective stage-specific parasite antigens and facilitate drug screening trials, to aid the development of much needed diagnostic and therapeutic options for paramphistomosis.

Testing Placement of Gastric Feeding Tubes in Infants

BACKGROUND

Inadvertent positioning of a nasogastric tube in the lung can cause serious complications, so identifying methods to detect improperly inserted tubes is imperative.

OBJECTIVES

To compare the sensitivity, specificity, and negative and positive predictive values of 4 pH cut points (< 4.0, < 4.5, < 5.0, and < 5.5) in differentiating gastric and tracheal aspirates under various treatment conditions and to explore the utility of a pepsin assay for distinguishing between gastric and tracheal aspirates.

METHODS

Gastric and tracheal aspirates were collected from critically ill infants undergoing mechanical ventilation who had nasogastric or orogastric feeding tubes. Aspirates were tested with colorimetric pH indicators and a rapid pepsin assay. Information about treatment conditions was obtained from medical records.

RESULTS

Two hundred twelve gastric aspirates and 60 tracheal aspirates were collected from 212 patients. Sensitivity was highest and specificity was lowest at the gastric aspirate pH cut point of less than 5.5. Positive predictive values were 100% at all pH cut points less than 5.0. Negative predictive values were higher at the pH cut point of less than 5.0 than at cut points less than 4.5. A higher percentage of pepsin-positive readings was found in gastric aspirates (88.3%) than in tracheal aspirates (5.4%).

CONCLUSION

For a desired positive predictive value of 100%, a pH cut point of less than 5.0 provides the best negative predictive values, regardless of gastric acid inhibitor administration and feeding status. The pepsin assay is promising as an additional marker to distinguish gastric from tracheal aspirates.

Nasogastric tube placement confirmation: where we are and where we should be heading

Background:

Insertion of a tube via the nasal passage is a common procedure which has been practiced for many years. There are various ways to assess the position of the nasogastric tube (NGT).

Objectives:

The objective of this study was to discuss the advantages and limitations of each method of NGT placement confirmation, to identify gaps in literature, and provide suggestions for future research.

Methods:

A search was performed with Pubmed, CINAHL, and Embase. The following keywords were used: “nasogastric,” “tube,” “placement,” “insertion,” and “measurement.” The results were narrowed down to those with full text available, published in the English language, those published within the last 10 years, and those studies done in the adult population. The reference lists of those articles were also referred to and relevant articles were retrieved. A final 26 relevant articles were included in this review, including six that were published more than 10 years ago but still relevant in this review.

Results:

A method to confirm NGT placement that is accurate, affordable, does not require gastric aspirates, and is able to be used not only upon insertion but also at regular intervals is lacking.

Conclusions:

This article provides a summary of the different methods of NGT placement confirmation and discusses their advantages and limitations. Gaps in literature and suggestions for future research were also deliberated.

Determining Feeding Tube Location by Gastric and Intestinal pH Values

BACKGROUND

The purpose of this study was to evaluate a series of pH values of aspirates from feeding tubes to differentiate between gastric and intestinal tube placement.

METHODS

One hundred ventilator-supported subjects, with an order for nasoduodenal feeding tube placement were randomly selected. The feeding tube was placed into the stomach, verified by auscultation, and 2 pH measurements were obtained. After the pH measurements were taken, tube location was then verified by fluoroscopy. When the tube was advanced into the small intestine, location was verified by fluoroscopy, and 2 additional pH measurements were obtained.

RESULTS

From the selected subjects, both a gastric and intestinal aspirate were obtained from 82 subjects. For the 82 subjects, the mean gastric and intestinal pH values were 4.8 +/- 2.3 and 7.1 +/- 1.0, respectively. For patients receiving acid-suppressing agents, these values were 5.0 +/- 2.3 and 7.2 +/- 1.0, respectively. For subjects not receiving acid-suppressing agents, these pH values were 4.0 +/- 2.5 and 6.7 +/- 1.1, respectively. For all patients, using a pH value of 6.5 as a predictor of feeding tube location, the sensitivity and specificity were 0.66 and 0.90. In addition, when an increase in pH > or = 1.0 was used as a predictor of location change for all patients, the sensitivity was 0.58.

CONCLUSIONS

The pH value was a reliable predictor of nasoduodenal tube placement. However, radiographic confirmation of location could not be excluded because of the low sensitivity using pH measurements alone. An increase of > or = 1.0 in gastric vs intestinal pH specimens could be useful to determine use of radiography confirmation of tube placement.

Monitoring Feeding Tube Placement

The purpose of this literature review is to describe currently available bedside methods to determine feeding tube placement. Described first are methods used at the time of blind insertion to distinguish between gastric and respiratory placement and gastric and small-bowel placement. Discussed next are methods used after feedings are initiated to determine if the tube has remained in the desired position in the gastrointestinal tract. Some of the methods are research-based, whereas others are opinion-based. The level of accuracy of the methods discussed in the review varies widely. No sure non-radiographic method exists to differentiate between respiratory, esophageal, gastric, and small bowel placement of blindly inserted feeding tubes in the fed or unfed state. However, a combination of some of the simpler and more accurate methods may be used to guide feeding tube placement during insertion and help identify the point at which an abdominal radiograph is most likely to confirm the desired location. In addition, methods described in this review can help determine when a radiograph is needed to confirm that a feeding tube has remained in the correct position after the initiation of feedings. Minimizing the number of radiographs taken to assure correct tube placement is important, especially in young children and in the critical care setting where the need for radiographs for other reasons is common.

Effect of Feeding-Tube Properties on Residual Volume Measurements in Tube-Fed Patients

BACKGROUND

The effect of feeding tube size and port configuration on the ability to measure gastric residual volume (GRV) is poorly understood. In addition, there is confusion about the need to measure GRVs during feedings into the small bowel. This study sought to (1) compare the volume of gastric contents obtained from small-diameter feeding tubes and large-diameter sump tubes concurrently positioned in the stomach and (2) describe the distribution of GRVs during small-bowel feedings.

METHODS

For the first objective, GRV measurements were made from 10-Fr tubes (n = 645) and 14-Fr or 18-Fr sump tubes (n = 645) concurrently present in 62 critically ill patients. Sixty-milliliter syringes were used to measure GRVs from the 10-Fr tubes; the fluid was returned to the stomach and measurements were repeated from the large-diameter sump tubes. To address the second research objective, 890 GRV measurements were made from 14-Fr or 18-Fr gastric sump tubes (not connected to suction) in 75 critically ill patients who were receiving small-bowel feedings.

RESULTS

When GRVs were >50 mL, a linear regression equation indicated that volumes obtained from the large-diameter sump tubes were about 1.5 times greater than those obtained from the small-diameter tubes concurrently present in the stomach, p < .001. Gastric volumes > or =100 mL were found in 11.6% of the 890 measurements made in patients receiving small-bowel feedings; volumes > or =150 mL were found in 5.4% of the measurements.

CONCLUSIONS

The findings suggest that GRVs obtained from large-diameter sump tubes are about 1.5 times greater than those obtained from 10-Fr tubes. Large GRVs occur in at least 5% of patients receiving postpyloric feedings.

Methods used by critical care nurses to verify feeding tube placement in clinical practice

BACKGROUND

The American Association of Critical-Care Nurses practice alert on verification of feeding tube placement makes evidence-based practice recommendations to guide nursing management of adult patients with blindly inserted feeding tubes. Many bedside verification methods do not allow detection of improper positioning of a feeding tube within the gastrointestinal tract, thereby increasing aspiration risk.

OBJECTIVES

To determine how the expected practices from the American Association of Critical-Care Nurses practice alert were implemented by critical care nurses.

METHODS

This study was part of a larger national, online survey that was completed by 370 critical care nurses. Descriptive statistics were used to analyze the data.

RESULTS

Seventy-eight percent of nurses used a variety of methods to verify initial placement of feeding tubes, although 14% were unaware that tube position should be confirmed every 4 hours. Despite the inaccuracy of auscultation methods, only 12% of nurses avoided this practice all of the time.

CONCLUSIONS

Implementation of expected clinical practices from this guideline varied. Nurses are encouraged to implement expected practices from this evidence-based, peer reviewed practice alert to minimize risk for patient harm.

Development and validation of a lipase nasogastric tube position test

Background

Nasogastric tube position should be checked every day by either aspirate pH or chest radiography to prevent fatal misplaced feeding into the lungs. Many patients do not have acidic gastric aspirates and require daily chest radiographs. We developed and validated a lipase test that was compatible with non-acidic gastric aspirates.

Methods

We conducted evaluations of diagnostic test accuracy at a teaching hospital in development and validation stages. Development: We collected gastric and lung aspirates from 34 consecutive patients. We measured pH and human gastric lipase activity in the laboratory. These data helped us develop the lipase test. Ingenza Ltd (Roslin, Scotland) created tributyrin-coated pH test paper, which human gastric lipase converted into butyric acid, thus correcting false negatives. Validation: We tested nasogastric feeding tube aspirates from 36 consecutive patients with pH and lipase tests, using chest radiography or trial by use as the reference standard.

Results

Development: We demonstrated human gastric lipase activity in the non-acidic stomach aspirates. Validation: The accuracy of the lipase test (sensitivity 97.2%, specificity 100%) was significantly better than pH (sensitivity 65.7%, specificity 100%, p<0.05).

Conclusions

When nasogastric tube stomach aspirates were not acidic and pH was falsely negative, the lipase test showed a true positive and was significantly more accurate.

Naso-enteric Tube Placement: A Review of Methods to Confirm Tip Location, Global Applicability and Requirements

BACKGROUND

The insertion of a tube through the nose and into the stomach or beyond is a common clinical procedure for feeding and decompression. The safety, accuracy and reliability of tube insertion and methods used to confirm the location of the naso-enteric tube (NET) tip have not been systematically reviewed. The aim of this study is to review and compare these methods and determine their global applicability by end-user engagement.

METHODS

A systematic literature review of four major databases was performed to identify all relevant studies. The methods for NET tip localization were then compared for their accuracy with reference to a gold standard method (radiography or endoscopy). The global applicability of the different methods was analysed using a house of quality matrix.

RESULTS

After applying the inclusion and exclusion criteria, 76 articles were selected. Limitations were found to be associated with the 20 different methods described for NET tip localization. The method with the best combined sensitivity and specificity (where n > 1) was ultrasound/sonography, followed by external magnetic guidance, electromagnetic methods and then capnography/capnometry. The top three performance criteria that were considered most important for global applicability were cost per tube/disposable, success rate and cost for non-disposable components.

CONCLUSION

There is no ideal method for confirming NET tip localisation. While radiography (the gold standard used for comparison) and ultrasound were the most accurate methods, they are costly and not universally available. There remains the need to develop a low-cost, easy-use, accurate and reliable method for NET tip localization.

Examining the evidence to guide practice: challenging practice habits

Nurses are the largest segment of the nation's health care workforce, which makes nurses vital to the translation of evidence-based practice as a practice norm. Critical care nurses are in a position to critically appraise and apply best evidence in daily practice to improve patients' outcomes. It is important for critical care nurses to continually evaluate their current practice to ensure that they are applying the current best evidence rather than practicing on the basis of tradition. This article is based on a presentation at the 2013 National Teaching Institute of the American Association of Critical-Care Nurses. Four practice interventions that are within the realm of nursing are critiqued on the basis of current best evidence: (1) turning critically ill patients, (2) sleep promotion in the intensive care unit, (3) feeding tube management in infants and children, and (4) prevention of venothromboembolism…again. The related beliefs, current evidence, and implications for practice associated with each topic are described.

Potential risk of malposition of nasogastric tube using nose-ear-xiphoid measurement

BACKGROUND

Correct placement of nasogastric tubes provide proper functionality and maximize benefit and minimize risk. The Nose-Ear-Xiphoid (NEX) body surface estimate method is a long-lasting technique, and this study was conducted to evaluate the correlation between NEX method and the secure insertion depth of nasogastric tube.

MATERIALS AND METHODS

Thirty patients with nasogastric tube insertion who received whole body positron emission tomography with computerized tomography scan (PET-CT) were recruited. All data were gathered in the image center, which included Nose-Ear (NE), Ear-Xiphoid (EX), Nose-Ear-Xiphoid (NEX), glabella-xiphoid (GX) and glabella-umbilicus (GU) lengths. The distances of the inserted portion of the nasogastric tube between the cardiac and the nostril were measured by multiplanar reconstruction algorithm.

RESULTS

Only one patient successfully placed all side-holes into the stomach while using NEX method to estimate inserting depth. Twenty-nine patients (96.7%) failed to place correctly. Fourteen participants had one or more side-holes in both the esophagus and the stomach sides. Fifteen patients could not pass through any side-hole across the gastroesophageal junction. They had shorter EX distances (p = 0.02), but no difference among the NE distances. Body height had the highest statistical correlation with nasogastric tube length (adjusted R(2) = 0.459), as compared with the NEX, GX and GU body surface methods.

CONCLUSION

This study suggests that NEX method is inappropriate for adult patients to estimate the ideal inserting length of nasogastric tube. Physicians should realize these underinsertions with any side-hole above the gastroesophageal junctions may increase the potential risk of complications.

Zein-based oral drug delivery system targeting activated macrophages

Reactive oxygen species (ROS) play an important role in the pathogenesis of rheumatoid arthritis (RA). ROS such as hydrogen peroxide and superoxide are overproduced by activated macrophages in RA. As scavengers of ROS, enzymatic proteins such as catalase and superoxide dismutase (SOD) have a great therapeutic potential; however, in vivo application is limited especially when they are orally administered. Although, the oral route is the most convenient for drug administration, therapeutic proteins are easily degraded in vivo by the harsh conditions of gastrointestinal (GI) tract. Here, we introduce a novel drug delivery system composed of zein, a plant storage protein derived from maize. We demonstrate that zein nanoparticles can protect therapeutic proteins, catalase and SOD, from the harsh conditions of GI tract. Folate-conjugated catalase or SOD in zein nanoparticles can target the activated macrophages and scavenge the ROS generated by macrophages in vitro. This novel drug delivery system will be applicable to other orally administered treatments based on the protective property in the harsh conditions of GI tract.