ReviewDoes Chronic Microaspiration Cause Idiopathic Pulmonary Fibrosis?
Section snippets
Silent Microaspiration and Lung Disease
Aspiration is defined as the inhalation of oropharyngeal or gastric contents into the larynx and lower respiratory tract.6 The clinical syndrome due to aspiration (eg, aspiration pneumonitis, aspiration pneumonia) depends on the nature and volume of aspirated material, the frequency of aspiration, and the host's response to the aspirated material.
The term “silent” microaspiration is used when patients have asymptomatic aspiration of small volumes of oropharyngeal secretions or gastric fluid
Silent Microaspiration and Pulmonary Fibrosis
Evidence from experimental models in animals and descriptive studies in humans support the concept of microaspiration as a potential cause of pulmonary fibrosis.
Silent Microaspiration and Idiopathic Pulmonary Fibrosis
The above animal and human data support the concept of silent microaspiration leading to pulmonary fibrosis, but many questions remain. Perhaps the most significant is how to reconcile the observed histopathology of aspiration-related lung injury (ie, airways injury and granulomatous inflammation) with that of idiopathic pulmonary fibrosis (ie, usual interstitial pneumonia pattern).
Usual interstitial pneumonia pattern is characterized by histologic heterogeneity of fibrosis, with alternating
Making the Diagnosis of Microaspiration
Several approaches for diagnosing microaspiration have been suggested, each having its own set of advantages and disadvantages (Table). We describe a few of these methods below.
Clinical Management
Until further evidence is available, we cannot recommend a specific screening, diagnostic, or management algorithm for microaspiration in idiopathic pulmonary fibrosis. Much has been written about the need to screen and treat gastroesophageal reflux in this population.59, 60 However, there is equipoise in the idiopathic pulmonary fibrosis community as to how aggressively to pursue this diagnosis. Even within this group of authors, there are differences in practice patterns. This is primarily
Gaps in Knowledge
One possible mechanism of microaspiration leading to pulmonary fibrosis is illustrated in the Figure. However, many questions need to be addressed in future studies to clarify the role of silent microaspiration in patients with idiopathic pulmonary fibrosis:
What is the true prevalence of microaspiration in patients with idiopathic pulmonary fibrosis? The finding of gastroesophageal reflux does not imply microaspiration, and there is no consensus on a gold standard for the diagnosis of
Conclusion
The data summarized in this review are provocative and implicate a potential role for microaspiration in the etiology and natural history of idiopathic pulmonary fibrosis. We firmly believe that defining the precise relationship between microaspiration and idiopathic pulmonary fibrosis is critically important because of its potential pathobiological and therapeutic implications. In general, current treatment strategies in idiopathic pulmonary fibrosis have focused on modulating the fibrotic
Acknowledgment
The authors wish to thank Simon Kimm, MD, for illustrating the Figure.
References (69)
- et al.
Quantitative aspiration during sleep in normal subjects
Chest
(1997) - et al.
Extraesophageal manifestations of GERD
Am J Med Sci
(2003) - et al.
Diffuse bronchiolar disease due to chronic occult aspiration
Mayo Clin Proc
(2006) - et al.
Bile acid aspiration and the development of bronchiolitis obliterans after lung transplantation
J Thorac Cardiovasc Surg
(2005) - et al.
J. Maxwell Chamberlain Memorial PaperEarly fundoplication prevents chronic allograft dysfunction in patients with gastroesophageal reflux disease
Ann Thorac Surg
(2004) - et al.
Improved lung allograft function after fundoplication in patients with gastroesophageal reflux disease undergoing lung transplantation
J Thorac Cardiovasc Surg
(2003) - et al.
Exposure of airway epithelium to bile acids associated with gastroesophageal reflux symptoms: a relation to transforming growth factor-beta1 production and fibroblast proliferation
Chest
(2007) - et al.
Pulmonary fibrosis associated with tracheobronchial aspirationA study of the frequency of hiatal hernia and gastroesophageal reflux in interstitial pulmonary fibrosis of obscure etiology
Chest
(1976) - et al.
Gastro-oesophageal reflux and interstitial lung disease
Dig Liver Dis
(2006) - et al.
Gastroesophageal reflux in patients with idiopathic pulmonary fibrosis referred for lung transplantation
J Thorac Cardiovasc Surg
(2007)
Sole treatment of acid gastroesophageal reflux in idiopathic pulmonary fibrosis: a case series
Chest
Laparoscopic fundoplication in patients with end-stage lung disease awaiting transplantation
J Thorac Cardiovasc Surg
Diagnosis of usual interstitial pneumonia and distinction from other fibrosing interstitial lung diseases
Hum Pathol
Role of surgical lung biopsy in separating chronic hypersensitivity pneumonia from usual interstitial pneumonia/idiopathic pulmonary fibrosis: analysis of 31 biopsies from 15 patients
Chest
Pulmonary aspiration shown by scintigraphy in gastroesophageal reflux-related respiratory disease
Chest
Aspiration of solid food particles into lungs of patients with gastroesophageal reflux and chronic bronchial disease
Chest
Typical GERD symptoms and esophageal pH monitoring are not enough to diagnose pharyngeal reflux
J Surg Res
High-resolution manometry and impedance-pH/manometry: valuable tools in clinical and investigational esophagology
Gastroenterology
A new pepsin assay to detect pulmonary aspiration of gastric contents among newly intubated patients
Am J Emerg Med
Pepsin in bronchoalveolar lavage fluid: a specific and sensitive method of diagnosing gastro-oesophageal reflux-related pulmonary aspiration
J Pediatr Surg
Bronchoalveolar pepsin, bile acids, oxidation, and inflammation in children with gastroesophageal reflux disease
Chest
Exhaled breath condensate: an overview
Immunol Allergy Clin North Am
Esophageal manometry and 24-hour pH monitoring in the diagnosis of pulmonary aspiration secondary to gastroesophageal reflux
Am J Surg
Current medical management of gastroesophageal reflux disease
Thorac Surg Clin
Idiopathic pulmonary fibrosis: diagnosis and treatmentInternational consensus statement
Am J Respir Crit Care Med
Prognostic significance of histopathologic subsets in idiopathic pulmonary fibrosis
Am J Respir Crit Care Med
Adult-onset pulmonary fibrosis caused by mutations in telomerase
Proc Natl Acad Sci U S A
Telomerase mutations in families with idiopathic pulmonary fibrosis
N Engl J Med
Acute exacerbations of idiopathic pulmonary fibrosis
Am J Respir Crit Care Med
Aspiration pneumonitis and aspiration pneumonia
N Engl J Med
Esophageal disease in scleroderma
J Clin Gastroenterol
Gastroesophageal reflux and pulmonary fibrosis in scleroderma: a study using pH-impedance monitoring
Am J Respir Crit Care Med
Lipoid pneumonia and chronic fibrosis
Clinical significance of pulmonary aspiration during the perioperative period
Anesthesiology
Cited by (0)
Funding: NHLBI HL086516.
Conflict of Interest: Dr. Lee has no conflicts of interest to disclose. Dr. Collard has provided consulting services to Actelion, Amira, InterMune, Gilead Science, Genzyme, CV Therapeutics, Nektar Therapeutics, and Roche, has served on an advisory committee for InterMune, and speaks regularly about idiopathic pulmonary fibrosis. Dr. Raghu has given lectures on the diagnosis and management of interstitial lung diseases and has discussed the potential role of chronic silent microaspiration in the pathogenesis of idiopathic pulmonary fibrosis. Dr. Sweet has no conflicts of interest to disclose. Dr. Hays has no conflicts of interest to disclose. Dr. Campos has no conflicts of interest to disclose. Dr. Golden has no conflicts of interest to disclose. Dr. King has given lectures on the diagnosis and management of interstitial lung diseases and has discussed the recent papers that have discussed the potential role of chronic silent microaspiration in the pathogenesis of idiopathic pulmonary fibrosis and as a potential cause of the acute respiratory decompensation manifested by some patients with idiopathic pulmonary fibrosis. In 2007, Dr. King provided expert testimony that a patient's diffuse parenchymal lung disease (lung fibrosis) was, more likely than not, caused by chronic aspiration.
Authorship: This manuscript represents original work, and all authors meet the criteria for authorship.