A potential mechanism by which aspiration of duodenogastric fluid augments the risk for bronchiolitis obliterans syndrome after lung transplantation.

OBJECTIVE: Aspiration of duodenogastric refluxate may damage the respiratory epithelium of lung allografts in transplant recipients. We sought to define a mechanism by which aspiration of duodenogastric fluid augments the risk of bronchiolitis obliterans syndrome after lung transplant in a murine model. METHODS: We analyzed the immunological effects of acute aspiration of duodenogastric fluid (0.5 mL/kg) on transplant naive (strain DBA/2J) and transplanted mice (strain B6D2F1/J to strain DBA/2J). Serum antibodies to the lung self-antigens (SAgs) K-alpha1 tubulin and collagen-V were determined by enzyme-linked immunosorbent assay. Exosomes were isolated from serum, and immunoblot membranes were probed for antibodies to lung SAgs. Lung sections were assessed for fibrotic burden and obliterative bronchiolitis lesions by histologic and immunohistochemical analyses, including trichrome staining. RESULTS: Transplanted mice that received duodenogastric fluid developed higher levels of antibodies to the lung SAgs K-alpha1 tubulin and collagen-V and exosomes with lung SAgs on posttransplant days 14 and 28 than transplanted mice with sham aspiration or transplant naive mice (with and without aspiration). All lung allografts demonstrated severe grade A4 rejection on posttransplant day 14, with the highest mean fibrotic burden and mean number of obliterative bronchiolitis-like lesions per microscopic field on day 28 in recipients with aspiration. CONCLUSIONS: This study links aspiration of duodenogastric fluid after lung transplant to higher autoimmune responses to lung SAgs and the release of circulating exosomes with lung SAgs, which together promote sustained immune responses leading to extensive lung parenchymal damage and, ultimately, severe obliterative bronchiolitis-the histologic hallmark of bronchiolitis obliterans syndrome.

The profibrotic effects of chronic microaspiration of bile acids on lungs of rats at different stages.

This study aimed to explore the profibrotic effects of chronic microaspiration of two major bile acids, including chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA), on lungs of rats at different stages, as well as the underlying mechanisms in vivo. A rat model was induced by weekly intratracheal instillation of DCA and CDCA. Our results showed that chronic microaspiration of bile acids resulted in alveolar structure disorder, and inflammatory cells infiltration in the pulmonary interstitium at the early stage. Subsequently, numerous fibroblasts were proliferated, and collagen deposition was profoundly increased over the interstitium of the airways and vessels. Compared with control group, the expression of α-smooth muscle actin, type I collagen, hydroxyproline, transforming growth factor-ß1 (TGF-ß1), and matrix metalloproteinase-9 in the lung tissues were remarkably elevated at the 2nd week, reached the highest level at the 6th week, and maintained high at the 8th week in both DCA- and CDCA-treated groups (P < 0.05). Furthermore, chronic microaspiration of bile acids led to higher levels of glutathione and malondialdehyde, while lower level of superoxide dismutase in lung tissues compared with controls (P < 0.05), thereby resulting in the oxidant/antioxidant enzyme imbalance in the formation of fibrosis. In addition, we also found a consistent growth in the expression of farnesoid X receptor (FXR) in both DCA- and CDCA-treated groups. Our findings suggested that chronic microaspiration of bile acids could initiate the process of pulmonary fibrosis from the early phase and promote its progression in a time-dependent manner, which likely involved the TGF-ß1, oxidative stress, and FXR-related pathways.

Duración del ayuno preoperatorio en pacientes con cirugía programada / Duration of preoperative fasting in patients with scheduled surgery

Antecedentes y objetivo: el ayuno preoperatorio disminuye el riesgo de aspiración del contenido gástrico y sus complicaciones. Sin embargo, si es excesivo, favorece la regurgitación y el riesgo de broncoaspiración tras la inducción anestésica, así como alteraciones metabólicas e hidroelectrolíticas. Analizamos su duración, en pacientes con cirugías programadas en un hospital público de agudos. Material y métodos: se encuestó a todos los pacientes mayores de 18 años con cirugías programadas. Se recolectaron datos sobre la prescripción médica de ayuno, la hora de inducción anestésica y personales. El ayuno prescripto se comparó con las recomendaciones de las guías de la AAARBA (Asociación de Anestesia, Analgesia y Reanimación de Buenos Aires). Resultados: se reclutaron 139 pacientes, con una mediana de edad de 48 años (30; 64), 53% femeninos. La mediana del ayuno prescripto fue de 12,5 horas tanto para sólidos como para líquidos. El ayuno para sólidos que realizaron los pacientes tuvo una mediana de 14 horas, la cual resultó significativamente mayor que la prescripción (p < 0,001). En cambio, el ayuno para líquidos tuvo una mediana de 12 horas, no hallándose una diferencia significativa (p = 0,452) con lo prescripto. En comparación con la guía de la AAARBA, el ayuno prescripto excedió la recomendación para sólidos (4,5 h) y para líquidos (10,5 h). El ayuno realizado por el paciente excedió lo prescripto para sólidos (1,5 h), mientras que para líquidos fue inferior (0,5 h). Conclusión: el ayuno preoperatorio prescripto no se adecuó a las recomendaciones actuales. Las horas de ayuno realizadas por el paciente resultaron excesivas. (AU)

Background and objective: preoperative fasting reduces the risk of aspiration of gastric contents and its complications. However, if fasting is excessive, it favours regurgitation and the risk of pulmonary aspiration in patients undergoing general anaesthetic, such as metabolic and electrolyte disorders. We analysed its duration in patients with elective surgeries in public acute care hospital. Material and methodologies: patients over 18 years old with elective surgeries were surveyed. Data about medical fasting indication, time of induction of anaesthesia and personal information was collected. The prescribed fast was compared with the recommendations of the AAARBA (Association of Anaesthesia, Analgesia and Reanimation of Buenos Aires) guidelines. Results: 139 patients were gathered with a median of 48 years old (30; 64), 53% of them were female. Fasting indication median was of 12.5 h for solids and liquids. The fasting made by the patient for solids had a median of 14 h which resulted to be significantly higher to the indication (p < 0.001). By contrast, the fasting for liquids had a median of 12 h which it did not show a significant difference (p = 0.452) with the indication. In comparison with the AAARBA guideline, the fasting indication exceeded the recommendation for solids (4.5 h) and for liquids (10.5 h). The fasting made by the patient exceeded to what was indicated for solids (1.5 h) while for liquids, it was inferior (0.5 h). Conclusion: the indicated preoperative fasting was not adequate to the current recommendations. The hours of fasting made by patient were excessive. (AU)

Regeneration of severely damaged lungs using an interventional cross-circulation platform.

The number of available donor organs limits lung transplantation, the only lifesaving therapy for the increasing population of patients with end-stage lung disease. A prevalent etiology of injury that renders lungs unacceptable for transplantation is gastric aspiration, a deleterious insult to the pulmonary epithelium. Currently, severely damaged donor lungs cannot be salvaged with existing devices or methods. Here we report the regeneration of severely damaged lungs repaired to meet transplantation criteria by utilizing an interventional cross-circulation platform in a clinically relevant swine model of gastric aspiration injury. Enabled by cross-circulation with a living swine, prolonged extracorporeal support of damaged lungs results in significant improvements in lung function, cellular regeneration, and the development of diagnostic tools for non-invasive organ evaluation and repair. We therefore propose that the use of an interventional cross-circulation platform could enable recovery of otherwise unsalvageable lungs and thus expand the donor organ pool.

Effect of aspiration on the lungs in children: a comparison using chest computed tomography findings.

BACKGROUND: Detecting and addressing aspiration early in children with dysphagia, such as those with cerebral palsy, is important for preventing aspiration pneumonia. The current gold standards for assessing aspiration are swallowing function tests, such as fiberoptic endoscopic evaluation of swallowing (FEES) and videofluorographic swallowing study; however, the relationship between aspiration of secretion vs aspiration of foodstuff and pulmonary injury is unclear. To clarify this relationship, we examined the correlations between pneumonia findings from chest computed tomography (CT) and the presence or absence of aspiration detected by FEES. METHODS: Eighty-five children (11 years 2 months ±7 years 2 months) underwent FEES and chest CT. Based on the FEES findings, the participants were divided into groups: with and without food aspiration, and with and without saliva aspiration. Correlations between chest CT findings of pneumonia and the presence or absence of each type of aspiration were then examined. RESULTS: No significant correlations were observed between food aspiration and chest CT findings of pneumonia, whereas saliva aspiration and chest CT findings of pneumonia were significantly correlated. In addition, saliva aspiration was significantly associated with bronchial wall thickening (p < 0.01) and atelectasis (p < 0.05). CONCLUSIONS: Our findings in children suggest that: (1) the presence or absence of food aspiration detected by FEES evaluation has little correlation with pneumonia, and (2) the presence or absence of saliva aspiration may be an indicator of aspiration pneumonia risk.

¿El reflujo gastroesofágico y la aspiración de contenido gástrico están implicados en la etiopatogenia y la progresión de la fibrosis pulmonar idiopática? / Does gastroesophageal reflux and gastric content aspiration have some role in the pathogenesis and progression of Idiopathic Pulmonary Fibrosis?

Resumen El reflujo gastroesofágico (RGE) y la aspiración oculta de contenido digestivo están probablemente implicados en la etiopatogenia y progresión de la fibrosis pulmonar idiopática (FPI). Los mecanismos patogénicos involucrados son la disminución de la distensibilidad pulmonar y el consiguiente aumento de la presión negativa intratorácica durante la inspiración, así como la disminución de los mecanismos de control de la motilidad esofágica o del tono del esfínter esofágico inferior. La prevalencia de RGE y anomalías de la motilidad esofágica están aumentadas en los pacientes con FPI comparado con la población general. Entre los pacientes con FPI, el 67-76% demostraron exposición anormal al contenido ácido en el esófago. Sin embargo, no hubo relación entre la gravedad del RGE y la gravedad de la FPI. Los estudios que han examinado el tratamiento antirreflujo en esta población han sido escasos. Incluso, algunos datos sugieren que el tratamiento antiácido puede ser perjudicial en algunos pacientes con esta condición. Después de analizar toda la evidencia relevante encontrada hasta la fecha, concluimos que no se puede establecer una relación causal entre el RGE, la aspiración del contenido gástrico y la patogénesis de la FPI. Además, existe escasa evidencia clínica que haya examinado el tratamiento antirreflujo en pacientes con fibrosis pulmonar idiopática.

ABSTRACT Gastroesophageal reflux (GERD) and hidden aspiration of gastric contents are probably involved in the pathogenesis and progression of idiopathic pulmonary fibrosis (IPF). The pathological mechanisms involved are decreased pulmonary distensibility and consequent increase of intrathoracic negative pressure during inspiration, as well as decreased control mechanisms of esophageal motility or lower esophageal sphincter. The prevalence of GERD and oesophageal dysmotility was higher in patients with IPF as compared with general population. Among patients with IPF, 67-76% demonstrated abnormal oesophageal acid exposure. However, no relationship was demonstrated between severity of GERD and severity of IPF. Data are scant on outcomes of antireflux treatment in patients with IPF. Actually, some data suggests that antacid treatment may be deleterious in some IPF patients. After analyzing all the relevant evidence found to date, a causal relationship between GERD, gastric content aspiration and IPF pathogenesis cannot be established. There is scant evidence examining antireflux treatment in idiopathic pulmonary fibrosis patients.

Acute lung injury induced by whole gastric fluid: hepatic acute phase response contributes to increase lung antiprotease protection.

BACKGROUND: Gastric contents aspiration in humans is a risk factor for severe respiratory failure with elevated mortality. Although aspiration-induced local lung inflammation has been studied in animal models, little is known about extrapulmonary effects of aspiration. We investigated whether a single orotracheal instillation of whole gastric fluid elicits a liver acute phase response and if this response contributes to enrich the alveolar spaces with proteins having antiprotease activity. METHODS: In anesthetized Sprague-Dawley rats receiving whole gastric fluid, we studied at different times after instillation (4 h -7 days): changes in blood cytokines and acute phase proteins (fibrinogen and the antiproteases alpha1-antitrypsin and alpha2-macroglobulin) as well as liver mRNA expression of the two antiproteases. The impact of the systemic changes on lung antiprotease defense was evaluated by measuring levels and bioactivity of antiproteases in broncho-alveolar lavage fluid (BALF). Markers of alveolar-capillary barrier derangement were also studied. Non-parametric ANOVA (Kruskall-Wallis) and linear regression analysis were used. RESULTS: Severe peribronchiolar injury involving edema, intra-alveolar proteinaceous debris, hemorrhage and PMNn cell infiltration was seen in the first 24 h and later resolved. Despite a large increase in several lung cytokines, only IL-6 was found elevated in blood, preceding increased liver expression and blood concentration of both antiproteases. These changes, with an acute phase response profile, were significantly larger for alpha2-macroglobulin (40-fold increment in expression with 12-fold elevation in blood protein concentration) than for alpha1-antitrypsin (2-3 fold increment in expression with 0.5-fold elevation in blood protein concentration). Both the increment in capillary-alveolar antiprotease concentration gradient due to increased antiprotease liver synthesis and a timely-associated derangement of the alveolar-capillary barrier induced by aspiration, contributed a 58-fold and a 190-fold increase in BALF alpha1-antitrypsin and alpha2-macroglobulin levels respectively (p < 0.001). CONCLUSIONS: Gastric contents-induced acute lung injury elicits a liver acute phase response characterized by increased mRNA expression of antiproteases and elevation of blood antiprotease concentrations. Hepatic changes act in concert with derangement of the alveolar capillary barrier to enrich alveolar spaces with antiproteases. These findings may have significant implications decreasing protease burden, limiting injury in this and other models of acute lung injury and likely, in recurrent aspiration.

The Intersection of GERD, Aspiration, and Lung Transplantation.

Lung transplantation is a radical but life-saving treatment option for patients with end-stage lung diseases, such as idiopathic pulmonary fibrosis (IPF) and scleroderma. In light of the proposed association and controversy linking gastroesophageal reflux disease (GERD) to IPF and lung transplant outcome, the American Gastroenterological Association convened during the DDW in Washington in May 2015 a multidisciplinary group of experts in the field of GERD and lung transplantation to make considerations about the care of these patients based on available data and subsequent expert panel discussion at this symposium. The following topics were discussed: (1) pathophysiology of GERD-induced pulmonary symptoms, (2) GERD evaluation before and after lung transplantation, (3) outcome of lung transplantation for IPF and scleroderma, and (4) role of laparoscopic fundoplication before or after lung transplantation.

Exhaled Breath Condensate Pepsin: Potential Noninvasive Test for Gastroesophageal Reflux in COPD and Bronchiectasis.

BACKGROUND: Acid gastroesophageal reflux is a common problem in non-cystic fibrosis bronchiectasis and COPD. Invasive methods are used to diagnose gastroesophageal reflux, but the ability to detect pulmonary microaspiration of gastric contents using this method is unclear. A noninvasive option to detect pulmonary microaspiration is to measure pepsin in exhaled breath condensate (EBC), but this has not been related to esophageal pH monitoring in these lung conditions. This study aimed to measure pepsin concentrations and pH in EBC and to determine the relationship to gastroesophageal reflux in bronchiectasis or COPD. METHODS: Subjects with bronchiectasis (n=10) or COPD (n=10) and control subjects (n=10) completed 24-h esophageal pH monitoring for detection of acid gastroesophageal reflux, measuring the percentage of reflux time in the proximal esophagus and the DeMeester score (DMS). Concurrently, 3 samples of EBC were collected from each subject, and pH was measured and pepsin concentrations were analyzed by enzyme-linked immunosorbent assay. RESULTS: EBC pepsin was detected in subjects with bronchiectasis (44%) or COPD (56%) and in control subjects (10%). A diagnosis of gastroesophageal reflux was not associated with a higher concentration of EBC pepsin in bronchiectasis (P=.21) or COPD (P=.11). EBC pepsin concentration did not correlate with DMS (rs=0.36) or proximal reflux index (rs=0.25) in subjects with bronchiectasis or with DMS (rs=0.28) or proximal reflux index (rs=0.21) in patients with COPD. EBC and sputum pepsin concentrations were moderately correlated in bronchiectasis (rs=0.56) and in COPD (rs=0.43). CONCLUSIONS: Pepsin is detectable in EBC samples in bronchiectasis and COPD. Although no association was found between pepsin concentrations and a diagnosis of gastroesophageal reflux, a moderate relationship between sputum and EBC pepsin concentrations suggests that EBC pepsin may be a useful noninvasive marker of pulmonary microaspiration.

Association between tracheal pepsin, a reliable marker of gastric aspiration, and head of bed elevation among ventilated neonates.

OBJECTIVES: To determine the frequency of tracheal pepsin in ventilated neonates and whether the angle of head elevation was associated with tracheal pepsin. STUDY DESIGN: Serial trachael samples (at 3, 7, 14, 21 and 28 days of ventilation) were obtained from intubated, ventilated very low birth weight infants. Presence of tracheal pepsin was determined by Western blot analysis using a specific anti-human pepsin antibody. RESULTS: Tracheal pepsin was detected in 35/66 (53%) of the ventilated neonates (birthweight: 798 ± 268 grams [mean ± standard deviation]). Neonates whose head elevation was in the upper quartile (≥14 degrees) during the first sampling time (day 3) were less likely (4/16 vs 9/10, P = 0.0013) to have tracheal pepsin when compared to neonates whose head elevation was in the lowest quartile (≤8 degrees). CONCLUSIONS: Pepsin, a marker for gastric secretion aspiration, was detected in 53% of ventilated low birth weight neonates; early elevation of the head of the bed was associated with a lower rate of tracheal pepsin.

TRPV4: an exciting new target to promote alveolocapillary barrier function.

Transient receptor potential (TRP) channels are emerging as important players and drug targets in respiratory disease. Amongst the vanilloid-type TRP channels (which includes the six members of the TRPV family), target diseases include cough, asthma, cancer, and more recently, pulmonary edema associated with acute respiratory distress syndrome. Here, we critically evaluate a recent report that addresses TRPV4 as a candidate target for the management of acute lung injury that develops as a consequence of aspiration of gastric contents, or acute chlorine gas exposure. By use of two new TRPV4 inhibitors (GSK2220691 or GSK2337429A) and a trpv4(-/-) mouse strain, TRPV4 was implicated as a key mediator of pulmonary inflammation after direct chemical insult. Additionally, applied therapeutically, TRPV4 inhibitors exhibited vasculoprotective effects after chlorine gas exposure, inhibiting vascular leakage, and improving blood oxygenation. These observations underscore TRPV4 channels as candidate therapeutic targets in the management of lung injury, with the added need to balance these against the potential drawbacks of TRPV4 inhibition, such as the danger of limiting the immune response in settings of pathogen-provoked injury.

Gastro-oesophageal reflux and gastric aspiration in idiopathic pulmonary fibrosis patients.

The aim of the study was to characterise gastro-oesophageal reflux (GOR) in idiopathic pulmonary fibrosis (IPF). 40 consecutive IPF patients underwent pulmonary high-resolution computed tomography (HRCT) scan and impedance-pH monitoring while off antisecretory therapy. The presence of pulmonary fibrosis was assessed using validated HRCT scores. Reflux features included distal oesophageal acid exposure, number of acid/weakly acidic reflux episodes and their proximal migration. 40 consecutive patients with interstitial lung disease other than IPF (non-IPF patients) and 50 healthy volunteers were also enrolled. IPF patients had significantly higher (p<0.01) oesophageal acid exposure (median (interquartile range (IQR)) 9.25 (4.7-15.4)% versus 3.3 (1.4-7.4)% versus 0.7 (0.2-4.2)%, number of acid (median (IQR) 45 (23-55) versus 32 (19-44) versus 18 (10-31)), weakly acidic (median (IQR) 34 (19-43) versus 21 (11-33) versus 18 (15-28)) and proximal reflux (median (IQR) 51 (26.5-65.5) versus 20 (9.5-34.5) versus 9 (5-20)) events compared to non-IPF patients and healthy volunteers, respectively. Pulmonary fibrosis HRCT scores correlated well with reflux episodes in both the distal (r(2)=0.567) and proximal (r(2)=0.6323) oesophagus. Patients with IPF had more bile acids and pepsin (p<0.03) in bronchoalveolar lavage fluid (BALF) (62% and 67%, respectively) and saliva (61% and 68%, respectively) than non-IPF patients (25% and 25% in BALF, and 33% and 36%, respectively, in saliva) and controls (0% and 0% in BALF and saliva, respectively). Acid GOR is common in IPF, but weakly acidic GOR may also occur. Patients with IPF had a risk of pulmonary aspiration of gastric contents. Outcome studies with intense antireflux therapy are needed.