Lipid-laden macrophages in the tracheal aspirate of ventilated neonates receiving Intralipid: A pilot study

Gastroesophageal reflux in cystic fibrosis: current understandings of mechanisms and management

Cystic fibrosis (CF) is an inherited disease that affects both the lungs and the digestive system in children and adults. Thick mucus fills the gut and blocks lumens of the pancreas and hepatobiliary systems, creating insufficient pancreas function and liver disease. Chronic gastrointestinal (GI) complications, including intestinal obstruction, occur in neonates, and poor digestion and gastroesophageal reflux disease (GERD) in children. Although GI symptoms tend to improve with age, CF and associated GERD eventually create respiratory insufficiency; the only available treatment option at this stage is a bilateral lung transplant, which carries considerable morbidity and mortality. While GERD may reoccur as a complication of lung transplantation, GERD symptoms are often reduced following a fundoplication.

Dysphagia and aspiration in children

Aspiration is a significant cause of respiratory morbidity and sometimes mortality in children. It occurs when airway protective reflexes fail, especially, when dysphagia is also present. Clinical symptoms and physical findings of aspiration can be nonspecific. Advances in technology can lead to early diagnosis of dysphagia and aspiration, and, new therapeutic advances can significantly improve outcome and prognosis. This report first reviews the anatomy and physiology involved in the normal process of swallowing. Next, the protective reflexes that help to prevent aspiration are discussed followed by the pathophysiologic events that occur after an aspiration event. Various disease processes that can result in dysphagia and aspiration in children are discussed. Finally, the various methods for diagnosis and treatment of dysphagia in children are reviewed.

Lipid-Laden Alveolar Macrophages and pH Monitoring in Gastroesophageal Reflux-Related Respiratory Symptoms

Lipid-laden alveolar macrophages and pH monitoring have been used in the diagnosis of chronic aspiration in children with gastroesophageal reflux (GER). This study was conducted to prove a correlation between the detection of alimentary pulmonary fat phagocytosis and an increasing amount of proximal gastroesophageal reflux. It was assumed that proximal gastroesophageal reflux better correlates with aspiration than distal GER. Patients from 6 months to 16 years with unexplained recurrent wheezy bronchitis and bronchial hyperreactivity, or recurrent pneumonia with chronic cough underwent 24-hour double-channel pH monitoring and bronchoscopy with bronchoalveolar lavage (BAL). Aspiration of gastric content was determined by counting lipid laden alveolar macrophages from BAL specimens. There were no correlations between any pH-monitoring parameters and counts of lipid-laden macrophages in the whole study population, even when restricting analysis to those with abnormal reflux index expressing clinically significant GER. Quantifying lipid-laden alveolar macrophages from BAL in children with gastroesophageal-related respiratory disorders does not have an acceptable specificity to prove chronic aspiration as an underlying etiology. Therefore, research for other markers of pulmonary aspiration is needed.

Biomarkers in the diagnosis of aspiration syndromes

Recognizing and managing the different types of aspiration events remain a challenging task due to the lack of distinguishing clinical or laboratory characteristics. Numerous biomarkers in serum, sputum and bronchoalveolar lavage have been studied, and their role in the recognition of aspiration remains controversial at this time. Recent animal investigations using an array of biomarkers based on distinct pathogenic features of each aspiration event have produced promising results; however, they have not been validated in humans. Newer markers are being introduced as diagnostic and prognostic tools in conditions such as community-acquired pneumonia and sepsis, but they have not been examined in aspiration. The present review summarizes the different biomarkers that have been studied in aspiration and those who might have a potential clinical use in the future.

Pepsin, a reliable marker of gastric aspiration, is frequently detected in tracheal aspirates from premature ventilated neonates: relationship with feeding and methylxanthine therapy

OBJECTIVES

To determine the frequency of pepsin detection in tracheal aspirate (TA) samples of mechanically ventilated premature neonates and its association with feedings and methylxanthine therapy.

PATIENTS AND METHODS

Serial TA samples (days 1, 3, 5, 7, 14, 21, 28 and >28 days) were collected from premature neonates receiving ventilatory support. An enzymatic assay with a fluorescent substrate was used to detect pepsin. Pepsin was also measured in 10 serum samples collected in conjunction with the TA samples from 8 neonates.

RESULTS

A total of 239 TA samples was collected from 45 premature neonates (mean birth weight, 762 +/- 166 g; mean gestational age, 25.5 +/- 1.5 wk). Pepsin was detectable in 222 of 239 TA samples (92.8%) and in none of the serum samples. Pepsin was significantly lower on day 1 (mean, 170 +/- 216 ng/mL) when compared with all other time points (P < 0.05). Mean concentration of pepsin was significantly lower when infants were unfed (265 +/- 209 ng/mL) compared with levels during feeding (390 +/- 260 ng/mL, P = 0.02). The mean level of pepsin was significantly higher in infants during xanthine therapy (419 +/- 370 ng/mL) compared with no xanthine therapy (295 +/- 231 ng/mL, P = 0.037).

CONCLUSION

Pepsin, a marker of gastric contents, was detected in more than 92% of TA samples from premature infants on mechanical ventilation. The level of pepsin was higher in fed infants when compared with unfed infants. Xanthine therapy was also associated with increased pepsin in TA samples. Chronic aspiration of gastric contents may worsen lung disease in premature infants.

Poly-lactic-glycolic acid microspheres: a biodegradable marker for the diagnosis of aspiration in hamsters

Aspiration is a major cause of lung disease in infants and young children. As the symptoms and signs of aspiration are not specific, the diagnosis is delayed due to a low index of suspicion and low sensitivity and specificity of the available diagnostic tests. In the present study, we evaluated the utility of microspheres composed of a degradable polymer, polylactic glycolic acid (PLGA), as a marker to diagnose aspiration in hamsters. Thirty hamsters underwent direct tracheal instillation of 0.1 mL of a suspension of PLGA. Eighteen other animals served as controls and underwent tracheal instillation of 0.1 mL of saline. Three animals served as naive controls and had no tracheal instillation. Five animals from the PLGA group and three from the saline group underwent whole-lung lavage (WLL) on days 1, 8, 15, 29, 43, and 58. PLGA microspheres were easily identified under light microscopy inside the alveolar macrophages obtained from WLL in all PLGA-instilled animals during all studied days. The number and size of PLGA microspheres within the alveolar macrophages decreased gradually with time with a 90% rate of disappearance of about 36 d. There was a marked neutrophilic response in lung lavage and a mild peribronchial neutrophil infiltration on the first day after tracheal instillation of PLGA which subsequently disappeared. We conclude that PLGA microspheres are a sensitive and specific marker for aspiration in hamsters. The usefulness of this test in diagnosing aspiration in humans should be further evaluated in clinical studies.

Immunocytochemical detection of milk proteins in tracheal aspirates of ventilated infants: a pilot study

In this study, we evaluated immunocytochemical staining for milk proteins (alpha-lactalbumin and beta-lactoglobulin) in tracheal aspirates of mechanically ventilated infants, and assessed whether this staining technique supported a clinical diagnosis of aspiration in infants receiving orogastric feedings. All newborns requiring mechanical ventilation in the neonatal intensive care unit of a major tertiary care hospital were potential subjects for this study. Tracheal aspirates were obtained prior to the introduction of enteral feeding and at various time points thereafter in newborns requiring mechanical ventilation. Cells were obtained and processed for immunocytochemical staining of alpha-lactalbumin and beta-lactoglobulin. In total, 88 specimens recovered from 34 infants were adequate for staining. Alveolar macrophages recovered from most of the infants who were never fed (true negative controls) did not display immunoreactivity for milk proteins: 4/34 or 12% of infants' aspirates demonstrated presence of milk proteins before enteral feeding was commenced. Tracheal aspirates obtained from 12 infants after introduction of enteral feedings appeared to support clinical and radiological findings suggestive of aspiration events, with positive immunostaining on several occasions. These observations support our work in a murine model and demonstrate that immunocytochemical staining of tracheal aspirates for milk proteins may enhance the ability to diagnose pulmonary aspiration. Further studies are needed to define the clinical significance of our findings and the effects of single and repeated aspiration events on respiratory status.

Limited reliability of lipid-laden macrophage index restricts its use as a test for pulmonary aspiration: comparison with a simple semiquantitative assay

The lipid-laden macrophage index (LLMI) is a semiquantitative evaluation of alveolar macrophage lipid content used in diagnosis of pulmonary aspiration. To date, there are no published reports regarding the reliability of LLMI. We sought to evaluate the interobserver and intraobserver variability and validity of LLMI and to compare it to a simpler macrophage lipid content index (LCI). To evaluate reliability we compared both the LLMI and LCI of 26 bronchoalveolar lavage (BAL) specimens from 14 aspirators and 12 non-aspirators on 10 separate occasions by two observers. The ranges of means and standard deviations (SD) of LLMI for observer 1 (Obs 1) were 19-160 (5-31) for aspirators, and 0-48 (0-15) for non-aspirators; and those of observer 2 (Obs 2) were 77-249 (13-33) for aspirators and 47-170 (8-37) for non-aspirators. The ranges of means and SD of LCI for Obs 1 were 2-8 (0-2) for aspirators and 0-4 (0-1) for non-aspirators, compared with 2-9 (0-2) for aspirators and 1-6 (0-2) for non-aspirators for Obs 2. No statistical significance was found between LLMI and LCI by comparing coefficients of variation (CV) in either groups or observers. Poor agreement between the two observers was found using a Bland Altman analysis, with the difference of the two observations mostly exceeding zero and becoming larger as the average of the two observations became bigger. The combined sensitivity, specificity, and positive and negative predictive value (PPV and NPV) for both observers of the LLMI were 57%, 75%, 84%, and 69% and those of LCI were 58%, 92%, 93%, and 69%. We conclude that there is poor reliability for both methods. The LCI is simpler and appears to be at least as good as the LLMI.

Gavaging the infant lung

An 8-month-old female infant was hospitalized for persistent bilateral infiltrates, failure to thrive, and tachypnea. An extensive diagnostic workup was negative, except for strong oil-red O staining of the white-turbid bronchoalveolar lavage fluid and borderline esophageal pH monitoring. Conservative treatment failed, and she was scheduled for gastrostomy and Nissen-fundoplication until the family physician found that the anxious mother was feeding the child forcibly, which caused chronic aspiration pneumonitis. The mother was given psychological support and was supervised, and the child recovered completely.

Charcoal is a sensitive, specific, and stable marker for the diagnosis of aspiration in hamsters

The diagnosis of recurrent aspiration in young children is a perpetual challenge because there is no specific gold standard test to be used. The finding of lipid-laden alveolar macrophages in bronchoalveolar lavage (BAL) is a sensitive but nonspecific marker for the diagnosis of aspiration. We conducted a short-term study comparing tracheal instillation of saline, milk, or a milk-charcoal mixture in hamsters. BAL cytology, lipid-laden alveolar macrophage index, charcoal alveolar macrophage index, and lung histology were monitored for 10 d. A long-term study was performed, and hamsters were monitored for 92 d after milk-charcoal tracheal instillation. Baseline animals (n = 4) had no tracheal instillation. Saline- and milk-instilled animals had BAL performed after 1 (n = 4), 3 (n = 4), and 10 (n = 4) d. Milk-charcoal-instilled animals had BAL performed after 1 (n = 4), 3 (n = 4), 10 (n = 4), 30 (n = 2), 58 (n = 2), and 92 (n = 2) d after tracheal instillation. Total cell counts and percent neutrophils in BAL fluid increased significantly and similarly after milk and milk-charcoal instillation on d 1 compared with baseline and saline-instilled animals. Lipid-laden alveolar macrophage index increased significantly only on d 3 after milk and milk-charcoal instillation compared with all days in the saline-instillation group. Charcoal alveolar macrophage index increased significantly after milk-charcoal instillation (d 1-58) from baseline or all days in the saline-instillation group. We conclude that charcoal particles instilled in tracheas of hamsters can be easily identified in BAL fluid and in lung parenchyma for as long as 3 mo after a single instillation and could potentially be used as a sensitive, specific, and stable marker for the diagnosis of aspiration, although the issue of its applicability to humans is still unsolved.

Aspiration: a factor in rapidly deteriorating bronchiolitis in previously healthy infants?

The objective of this study was to evaluate the presence of indicators of aspiration in previously healthy infants with respiratory syncytial viral (RSV) bronchiolitis who experienced rapid deterioration in their respiratory status. Lipid-laden macrophage index (LLMI) was assessed in 6 previously healthy infants with RSV bronchiolitis and no prior history of aspiration, who had a rapid deterioration of their respiratory status requiring mechanical ventilation. Five of 6 infants had a LLMI of more than 100, a level that is very suggestive of aspiration. We conclude that aspiration is likely to play a role when rapid deterioration occurs in infants with RSV bronchiolitis.

Pediatric bronchoscopy

Diagnostic flexible endoscopy for pediatric respiratory diseases is performed in many centers. Technical advances have resulted in performance of interventional bronchoscopies, and new diagnostic indications are being explored. Indications with documented clinical benefit include congenital or acquired progressive or unexplained airway obstruction. Pulmonary infections in immunodeficient children who do not respond to empirical antibiotic treatment may be diagnosed by bronchoscopy and bronchoalveolar lavage (BAL). The potential usefulness of bronchoscopy and BAL for managing chronic cough, wheeze, or selected cases with asthma or cystic fibrosis requires further study. The use of transbronchial biopsies (TBB) is established in pediatric lung transplantation. The role of TBB in the diagnosis of chronic interstitial lung disease in children remains to be determined. For a number of interventional applications, rigid endoscopy is required, and pediatric bronchoscopists should be trained in its use. Complications in pediatric bronchoscopy are rare, but severe nosocomial infection or overdosing with local anesthetics has occurred. The issues of quality control, video documentation, interobserver variability of findings, and educational standards will have to be addressed in the future as bronchoscopy use becomes less restricted to only large pediatric pulmonary units.