Time course of lipid-laden pulmonary macrophages with acute and recurrent milk aspiration in rabbits

Lipid-laden macrophage index as a marker of aspiration in children, is it reliable? A scoping review

INTRODUCTION

A diagnostic pathway to detect aspiration is challenging and usually requires a multidisciplinary approach and a variety of tests. Lipid-laden macrophage index (LLMI) was first described in 1985 by Corwin and Irwin as a promising tool to detect aspiration. Information in the literature as well as physicians' opinions about the clinical value of the LLMI remains controversial.

OBJECTIVES

To assess the clinical value and possible limitations of LLMI as a diagnostic marker for detecting aspiration in children.

METHODS

Based on the available literature we thought to answer the following questions: 1. Is there a reliable cutoff value of LLMI to detect aspiration? 2. What are the limitations of LLMI? We queried 8 electronic databases: Medline, Embase, CINAHL, Cochrane, Global Health, Web of Science, Africa Wide Information, and Global Index Medicus. Studies were selected based on established study criteria. Search was limited to publications in English language including human and animal studies. Authors reviewed 2900 articles and identified 21 relevant to the studied subject.

RESULTS

Research reveals different proposed cutoff values for aspirators ranging from 85 to 200 macrophages. LLMI reliability has several limitations including: inter- and intraobserver variability among pathologists scores, inability to differentiate between exogenous and endogenous lipid content, inconsistencies in the definition of the term "aspiration" in various publications. Also, studies in animal models have shown that the nature of the disease, frequency of aspiration, and the time frame when bronchoalveolar lavage (BAL) is performed, could all contribute to the overlap in LLMI in aspirators versus non-aspirators.

DISCUSSION

Our research demonstrates the limitations of LLMI in distinguishing between aspirators and non-aspirators. We believe based on these findings that airway teams should audit their local data as to the value of BAL in detecting aspiration in their patient population.

Utilization of Oil Red O staining for assessing aspiration risk in lung transplant patients: A multidisciplinary prospective study with clinical practice insights

BACKGROUND

Gastroesophageal reflux disease with microaspiration has been associated with graft dysfunction in lung transplant patients. Identifying patients with aspiration is clinically important because it enables implementation of appropriate interventions like antireflux therapy. Oil Red O (ORO) staining with determination of the lipid-laden macrophage index (LLMI) has been proposed as a noninvasive surrogate marker in the detection of aspiration. The aim of this study was to prospectively evaluate clinical utilization of ORO staining in the assessment of aspiration risk.

METHODS

All transbronchial surgical pathology biopsies obtained in lung transplant patients undergoing routine surveillance from August 2020 through November 2021 were included in this study. Clinical team members prospectively ascertained the aspiration risk category (ARC) of each patient both before and after biopsy findings and recorded reasons for change in ARC.

RESULTS

A total of 132 transbronchial biopsies with concurrent LLMI were included in the study. LLMI was low in 51 cases (38.6%), including 21 of the 54 cases (38.9%) where aspiration was suggested based on the transbronchial biopsy findings. In total, 19 cases (14.4%) underwent a change in ARC post-biopsy including 10 that were upgraded and nine cases that were downgraded. Transbronchial biopsy findings were noted as the reason for change in ARC in the majority (15/19; 79%) of cases; only a minority (2/19; 10.5%) were due to the LLMI. Notably, 16 cases (12.1%) had a low LLMI with high-risk post-biopsy ARC and nine cases (6.8%) had a high LLMI with low-risk post-biopsy ARC.

CONCLUSIONS

This study observed that clinical evaluation for aspiration relied more heavily on transbronchial biopsy findings. Although LLMI may retain clinical utility in some scenarios, reevaluation of the clinical value of ORO testing would be prudent.

Bronchiectasis in chronic pulmonary aspiration: risk factors and clinical implications

INTRODUCTION

Bronchiectasis is a well-known sequela of chronic pulmonary aspiration (CPA) that can result in significant respiratory morbidity and death. However, its true prevalence is unknown because diagnosis requires high resolution computed tomography which is not routinely utilized in this population. This study describes the prevalence, time course for development, and risk factors for bronchiectasis in children with CPA.

MATERIALS AND METHODS

Using a cross-sectional design, medical records were reviewed for all patients with swallow study or airway endoscopy-confirmed aspiration in our airway center over a 21 month period. All patients underwent rigid and flexible bronchoscopy, and high resolution chest computed tomography. Prevalence, distribution, and risk factors for bronchiectasis were identified.

RESULTS

One hundred subjects age 6 months to 19 years were identified. Overall, 66% had bronchiectasis, including 51% of those less than 2 years old. The youngest was 8 months old. Severe neurological impairment (OR 9.45, P<0.004) and history of gastroesophageal reflux (OR 3.36, P=0.036) were identified as risk factors. Clinical history, exam, and other co-morbidities did not predict bronchiectasis. Sixteen subjects with bronchiectasis had repeat chest computed tomography with 44% demonstrating improvement or resolution.

DISCUSSION

Bronchiectasis is highly prevalent in children with CPA and its presence in young children demonstrates that it can develop rapidly. Early identification of bronchiectasis, along with interventions aimed at preventing further airway damage, may minimize morbidity and mortality in patients with CPA.

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.

Reflux aspiration in children with neurodisability--a significant problem, but can we measure it?

Recurrent respiratory problems are common in children with severe neurodisability, and respiratory deterioration is a leading cause of premature death in this group. Although the etiology is multifactorial, recurrent pulmonary aspiration is thought to play a significant role. Gastroesophageal reflux is known to be common, as is oral-motor discoordination. Differentiating direct aspiration of food and saliva and gastric reflux aspiration is difficult and presents a challenge in managing patients and assessing their suitability for surgical antireflux procedures. This is particularly the case when children present with predominantly respiratory symptoms, where there may be direct aspiration, reflux aspiration, neither, or both. A clinical biomarker to identify and quantify reflux aspiration would therefore be useful in surgical assessment and may also be applicable as an outcome measure for clinical trials of antireflux surgery. In this review, we discuss the evidence base behind existing and potentially novel biomarkers of aspiration in bronchoalveolar lavage fluid. We highlight the limitations of the lipid-laden macrophage index, particularly with regard to its specificity and interrater/intrarater reliability. We discuss the laboratory methods available to measure promising new biomarkers (pepsin and bile acids) and highlight their potential advantages and disadvantages. Finally, to understand how aspiration causes clinical signs and symptoms in our patients, we need to study the effect of aspirated substances on the lung, and here we review the available in vivo and in vitro literature.

Lipid-laden macrophage index in healthy canines

BACKGROUND

The quantity of lipids in alveolar macrophages is used clinically as an indicator of aspiration, which is associated with increased lung inflammation. This is determined in the macrophages obtained from bronchoalveolar lavage (BAL) and is expressed as lipid-laden macrophage index (LLMI). Although there is ample data on LLMI in human subjects, there is no published data pertaining to the baseline measures of the LLMI in canines, which are extensively used for experimental studies on gastroesophageal reflex (GER) and airway diseases. Primary aim of the present study was to collect data pertaining to the cytology and LLMI in BAL fluids obtained from healthy dogs.

MATERIALS AND METHODS

Eight dogs underwent a bronchoscopy with BAL collection, and esophageal pH monitoring to determine the reflux index (RI). The BAL fluid was processed and reviewed under a microscope to determine the proportions of the various cell types and the LLMI.

RESULTS

The median RI among the subjects was found to be 0.6 (0.0, 1.2). The BAL cytology analysis showed 77.5% (71.0, 83.5) macrophages, 21.0 (13.0, 24.5) lymphocytes and 2.5 (1.5, 5.0) neutrophils. The median LLMI was found to be 156 (111, 208).

CONCLUSIONS

Although the differential cell counts in the dogs' BAL fluid was comparable to that of other experimental animals and humans, the LLMI was distinctly higher than the corresponding value reported for other species. As LLMI is a valuable modality for evaluation of intrapulmonary pathophysiology, these data on LLMI can be used as a species-specific standard for canine subjects used for experimental studies on GER and airway diseases.

Microaspiration in Infants with Laryngomalacia

OBJECTIVES/HYPOTHESIS

Laryngomalacia is the most common congenital laryngeal anomaly and the most frequent cause of stridor in infants. Infants with laryngomalacia may have associated respiratory symptoms other than stridor. In this study, we evaluated whether infants with laryngomalacia have episodes of microaspiration by calculating the amount of lipids present in the alveolar macrophages.

STUDY DESIGN

We reviewed bronchoalveolar lavage (BAL) findings obtained in 14 infants with laryngomalacia and in 11 control children.

METHODS

BAL was performed during flexible fiberoptic bronchoscopy (FFB) to diagnose persistent stridor. The presence of microaspiration was determined by evaluating the amount of lipid per single macrophage, assigning each cell a score from 0 to 4 according to the amount of lipid in the cytoplasm.

RESULTS

The lipid-laden macrophage index was similar in patients and controls (31.5, range 12-177 vs. 45, range 35-106). In 5 of the 14 (36%) patients the index exceeded 100, and more than 25% of the cells were graded 3 and 4, indicating the presence of microaspiration. The lipid-laden macrophage index correlated significantly with the number and percentage of BAL neutrophils (Pearson correlation test, r = 0.83, P < .001 and r = 0.925, P < .001) as a marker of lung inflammation.

CONCLUSIONS

Infants with laryngomalacia may have episodes of microaspiration. BAL performed during FFB to evaluate stridor may add helpful therapeutic information without increasing the risks of the procedure.

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.

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.

Bronchoalveolar lavage and esophageal pH monitoring data in children with "difficult to treat" respiratory symptoms

Gastroesophageal reflux (GER) may be associated with chronic or recurrent asthma-like symptoms secondary to bronchoconstrictor reflexes and/or inhalation of gastric content. The presence of lipid-laden alveolar macrophages has been proposed as an index to establish the degree of gastric aspiration. We evaluated 20 children with "difficult to treat" respiratory symptoms and a clinical history suggestive of GER. All children underwent 24-hr esophageal pH monitoring (pHm) and fiberoptic bronchoscopy with bronchoalveolar lavage (BAL). The amount of lipid per single macrophage was determined by a semiquantitative method, using fluorescence microscopy to detect Nile-Red-stained BAL cells and calculating a lipid-laden macrophage index (LLMI). Eleven children had positive pHm recordings, suggesting the presence of GER (pH-positive patients), and 9 had negative pHm records (pH-negative patients). The pH-positive patients had higher percentages of neutrophils and higher LLMI than the pH-negative children (P < 0.05). There were no correlations between the pHm records and either % BAL neutrophils or LLMI in pH-positive or pH-negative patients (P > 0.05; each correlation). In contrast, a single correlation was found between % BAL neuytrophils and LLMI, both in the pH-positive and in the pH-negative patients (r = 0.72, P = 0.02 and r = 0.71, P = 0.04, respectively). These data demonstrate that a significant proportion of pH-positive patients with respiratory symptoms have BAL abnormalities that suggest airway inflammation and gastric content aspiration. However, the intensity of GER as indicated by pH monitoring does not correspond with BAL data in all patients.

Airway reactivity following repeated milk aspiration in rabbits

Asthma and gastroesophageal reflux (GER) are commonly associated disorders. Microaspiration is one possible link between these processes. The purpose of this study was to assess methacholine reactivity following repeated small-volume aspiration such as may occur with GER. This was also correlated with airway cytology. Five weekly intratracheal instillations of either milk (N = 8) or saline sham controls (N = 7) in volumes of 0.25 mL/kg were performed in anesthetized rabbits. Transpulmonary pressure, flow, tidal volume, central airways resistance, and dynamic lung compliance were measured in anesthetized and paralyzed animals at baseline, after 2 and 5 weeks of instillation, and 3 weeks after the last instillation. Doubling concentrations of methacholine were given until a 50% or greater increase in resistance occurred (PC50R). Bronchial washings for cytological evaluation were performed after the physiologic measurements and before each instillation. There were no significant differences in airway reactivity between baseline and all subsequent observation points within each of the two groups. However, methacholine responsiveness was significantly higher in the milk group before the final instillation (PC50R = 5.84 vs. 12.97 mg/mL, P = 0.03) and at recovery (PC50R = 6.40 vs. 10.56 mg/mL, P = 0.047) when compared to saline controls. This was associated with a higher neutrophil percentage (P = 0.01) at 5 weeks, and eosinophil percentage (P = 0.05) at recovery in the bronchial wash specimens from the milk group. These results show that repeated small-volume aspiration of milk in rabbits causes persistent inflammation and is associated with greater airway reactivity when compared to sham controls. This inflammation was accompanied by either increased neutrophils or eosinophils in bronchial lavage specimens. These findings lend support to a possible role of microaspiration in association with increased airway reactivity in patients with GER.

A novel diagnostic method for pulmonary aspiration in a murine model. Immunocytochemical staining of milk proteins in alveolar macrophages

Aspiration of foreign material into the lungs has been implicated in the etiology of a variety of pulmonary disorders. Although aspiration is a common clinical problem, its diagnosis represents a major challenge due to the lack of sensitive and/or specific tests. In this study, we evaluated the sensitivity and specificity of a novel diagnostic method in a murine model of milk aspiration. Under light anesthesia, BALB/c mice received either single or repeated intranasal instillation of milk. Control animals received sterile physiologic saline or were infected with respiratory pathogens in a similar manner. After isolation and cannulation of the trachea, mouse lungs were lavaged with PBS at various time points after the last aspiration event. Cells were recovered for Oil Red O (ORO) staining as well as immunocytochemistry for milk proteins: alpha-lactalbumin and beta-lactoglobulin. After single aspiration of milk, a large number of alveolar macrophages displayed a strong immunoreactivity for alpha-lactalbumin for 2-96 h. After single and repeated aspiration, the percentage of positive cells for alpha-lactalbumin was significantly higher when compared with ORO staining at 24, 48, and 72 h (p < 0.05). No immunoreactivity for milk proteins was found in alveolar macrophages obtained from our control groups. These findings demonstrate that immunocytochemical staining of milk proteins within alveolar macrophages represents a novel, sensitive, and specific test for the diagnosis of aspiration in a murine model.

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

Lipid-laden macrophages (LLM) in tracheal aspirates are reported to be pathognomonic findings in exo- and endogenous lipoid pneumonia in adults. A pilot study was carried out to evaluate the effect of lipid infusion on the LLM index of the tracheal aspirates from ventilated neonates. All intubated infants were eligible for the study. Infants receiving parenteral nutrition had intravenous (IV) lipid introduced by 4-7 days of age; most samples after 7 days were from infants receiving IV lipid. Four infants received minimal gastric feeding; none had evidence of aspiration pneumonia. Tracheal aspirates from 28 infants were analyzed for the LLM index. Alveolar macrophages were graded 0-4 in direct relation to the amount of lipid per cell. One hundred macrophages were graded; the maximum possible LLM index was 400. Two hundred forty-five of 387 tracheal aspirate samples were acceptable for analysis. LLM indices increased during the first week after birth; the mean LLM index then continued in the same range, but with a wide distribution of individual values. The mean LLM index from infants receiving an IV lipid infusion during days 4-7 was 87.9 (SD = 44.8), and was significantly higher compared to 58.7 (SD = 40.8) in infants receiving no IV lipid (P < 0. 003). Tracheal aspirates from infants with and without IV lipid infusion yielded many LLM index values >100. These observations invalidate the use of the LLM index >100 as proof of aspiration pneumonia in this group of infants.

Lipid-laden alveolar macrophages (LLAM): a useful marker of silent aspiration in children

At present there is no test available which identifies children suffering from silent aspiration due to gastroesophageal reflux (GER). The purpose of this study was to determine whether lipid-laden alveolar macrophage (LLAM) scoring is a useful method to arrive at the diagnosis. We evaluated bronchoalveolar lavage fluid (BALF) from 68 children aged 6 months to 14 years (median 3.75 years) for the presence of lipid-laden alveolar macrophages. We compared children with chronic chest disease (CCD) and GER to healthy surgical controls without known lung disease, and to children with recurrent pneumonia without GER. By grading the amount of intracellular Sudan Red-positive material, we determined a semiquantitative lipid-laden macrophage (LLAM) score for each patient. Patients with chronic chest disease suspected to be caused by silent aspiration secondary to GER had a significantly higher LLAM score (median, 117; range, 10-956) than children with recurrent pneumonia due to other reasons (median, 29; range, 5-127; P < 0.01) and healthy controls (median, 37; range, 5-188; P < 0.01). We believe that simply observing lipid-laden macrophages is nonspecific, but quantitation of these cells is a useful method for diagnosing silent aspiration in children, especially when the score exceeds 200.

Lipid-laden macrophages in bronchoalveolar lavage fluid as a marker for pulmonary aspiration

An increased lipid content in alveolar macrophages of bronchoalveolar lavage (BAL) fluid is thought to be a useful indicator for recurrent pulmonary aspiration. To assess whether pulmonary diseases unrelated to aspiration can raise the lipid content in alveolar macrophages, we evaluated Oil-Red-O-stained smears of BAL fluid in 18 children aged 3-15 years undergoing elective surgery for nonpulmonary illnesses under general anesthesia and in 18 children aged 1-16 years who had pulmonary diseases without clinical evidence of aspiration (pneumonia, exogenous allergic alveolitis, or cystic fibrosis). A semiquantitative lipid-laden macrophage (LLM) index was determined for each patient. LLM indices in children without pulmonary disease were higher than those published for healthy adults. In children with pulmonary diseases but without evidence of aspiration, a significantly higher LLM index was observed compared to controls. The LLM indices of children with pulmonary diseases were similar to those published by other authors for children with pulmonary aspiration. We conclude that an elevated LLM index in alveolar macrophages of BAL can be found in a variety of pulmonary diseases in which there is no clinical evidence of aspiration and is therefore unlikely to be a specific parameter for silent pulmonary aspiration.

Effect of aspiration of milk on mechanisms of neural control in the airways of developing rabbits

We studied the effects of recurrent aspiration of milk on neural control of airways in young developing rabbits. Beginning at 1 week of age, rabbits received 0.5 ml/kg of whole milk or sterile physiologic saline intranasally while under light methoxyflourane anesthesia 5 days a week for a period of 3 weeks. At 4 and 8 weeks of age, in vitro studies of contractile and relaxant responses of tracheal smooth muscle (TSM) segments were evaluated. To assess the neurally mediated contractile responses, frequency response curves to electrical field stimulation (EFS) were performed with results expressed in terms of frequency of EFS causing 50% of the maximal contractile response (ES50) values. In addition, the contractile responsiveness of TSM to methacholine (MCh) as reflected by the concentration causing 50% of the maximal contractile response (EC50) values was also determined to evaluate the underlying cholinergic reactivity of this segment of airway. To assess nonadrenergic noncholinergic inhibitory (NANCi) responses, experiments were performed on TSM contracted with neurokinin A in the presence of atropine, propranolol, and indomethacin. EFS was delivered to the contracted tissue at stimulation frequencies ranging from 5 to 30 Hz with results expressed as mean percent relaxation. Recurrent aspiration of milk but not saline increased EFS-induced contractile responses, as shown by significantly lower ES50 values compared with the control group: P = 0.02 and P = 0.001 at 4 and 8 weeks of age, respectively. TSM responsiveness to MCh was no different between the two groups, suggesting that alterations in prejunctional mechanisms of neural control were most likely responsible for the increased contractile response to EFS. The NANCi responses were significantly decreased by milk aspiration at both 4 and 8 weeks of age, with the abnormalities less pronounced at the later time point. These findings demonstrate that repeated aspiration of milk leads to abnormal mechanisms of neural control within airways of developing rabbits. While aspiration of milk altered both contractile and relaxant responses to EFS, the former abnormalities became more pronounced with time while the latter appeared to be resolving. These observations suggest that injury to an airway early in development does not necessarily resolve with time but may persist, with functional abnormalities becoming more pronounced even after the airway insult has ceased.

The diagnostic value of bronchoalveolar lavage in immunocompetent children with chronic diffuse pulmonary infiltrates

We have investigated the diagnostic value of (BAL) in 29 immunocompetent children (ages 1 month to 18 years) with chronic diffuse pulmonary infiltrates on chest radiograph who presented for evaluation over a 3-year period. The median age at the time of the BAL was 20 months with a range of 1-210 months. Positive results (1) diagnostic of a primary disorder; (2) consistent with a diagnosis; or (3) diagnostic of a secondary disorder, were obtained in 20/29 patients (13 with a single positive BAL finding and 7 with more than one finding). BAL was diagnostic of a primary disorder in only 5 patients (17%) with aspiration detected in 3 and infection in 2. The differential diagnosis was narrowed in 15 patients by the presence of lymphocytosis, neutrophilia, or eosinophilia. A secondary disorder was uncovered in 8 patients. Negative results were obtained in 9 additional patients. We conclude that BAL provided useful information in children with chronic diffuse infiltrates, but its ability to determine the primary cause was limited.

Respiratory manifestations of gastroesophageal reflux disease in pediatric patients

Respiratory manifestations of gastroesophageal reflux disease (GERD) are being recognized with increasing frequency. We present the evaluation and management of four infants and children with unusual respiratory symptoms attributed to GERD. The advantages and disadvantages of diagnostic studies of GERD are discussed, and an evaluation and treatment protocol is presented. Treatment must be tailored to the nature and severity of the patient's presenting symptoms and includes conservative, pharmacologic, and/or surgical management.