Bronchoalveolar lavage in stable asthmatics does not cause pulmonary inflammation

Bronchial brushings for investigating airway inflammation and remodelling

Asthma is the commonest medical cause for hospital admission for children in Australia, affects more than 300 million people worldwide, and is incurable, severe in large number and refractory to treatment in many. However, there have been no new significant treatments despite intense research and billions of dollars. The advancement in our understanding in this disease has been limited due to its heterogeneity, genetic complexity and has severely been hampered particularly in children by the difficulty in obtaining relevant target organ tissue. This review attempts to provide an overview of the currently used and recently developed/adapted techniques used to obtain lung tissue with specific reference to the airway epithelium.

A randomized, placebo-controlled trial of bronchodilators for bronchoscopy in patients with COPD

BACKGROUND

In contrast to asthma, the indication for bronchodilators prior to bronchoscopy in patients with COPD has not been properly investigated. We therefore performed a randomized, double-blind, placebo-controlled trial to determine whether use of a short-acting bronchodilator provides a protective effect in patients with COPD undergoing bronchoscopy.

METHODS

One hundred twenty patients undergoing bronchoscopy were included. Patients with COPD were randomized to receive either 200 mug of salbutamol (n = 40) or placebo (n = 40) before bronchoscopy. Control patients (n = 40) did not receive any inhaled medication. Spirometry was performed before and 2 h after bronchoscopy in all patients. Sedative drug requirements and hemodynamic parameters were recorded.

RESULTS

Hemodynamic findings before, during, and after bronchoscopy were similar in patients with COPD randomized to either salbutamol or placebo (p = not significant for all). Compared to prebronchoscopy values, postbronchoscopy percentage of predicted FEV(1) decreased significantly in all three groups: salbutamol (median, - 4.7%; interquartile range [IQR], - 13.3 to 6.6); placebo (median, - 4.8%; IQR, - 19.9 to 8.4); and control subjects (median, - 10.0%; IQR, - 20.2 to - 3.3) [p = 0.023]. The decrease in FEV(1) was similar in all three patient groups (p = 0.432). The relative change in FEV(1) was inversely correlated to the increasing severity of COPD as expressed by Global Initiative for Chronic Obstructive Lung Disease stages (p = 0.01).

CONCLUSIONS

Premedication with an inhaled short-acting beta-agonist cannot be recommended in patients with COPD undergoing bronchoscopy.

Functional implications of BAL in the presence of restrictive or obstructive lung disease

Most of the complications associated to bronchoscopy are related to changes of the respiratory function during or after its performance. Prevention of complications should be achieved by understanding the effects of bronchoscopic procedures and their relation to the pulmonary function deterioration. Previous studies regarding the functional impairment caused by bronchoalveolar lavage (BAL) were mostly limited by the presence of interferent factors such as sedative drugs. Furthermore, it is not clear whether or not patients with different ventilatory disturbances present the same functional response to bronchoscopy and BAL. The aim of this study was to determine the additional effects of BAL over the respiratory function deterioration related to bronchoscopy in patients with different respiratory function profiles (normal, restrictive and obstructive). Forty patients submitted to bronchoscopy without premedication were divided into four groups: group I-normal pulmonary function submitted to basic bronchoscopy; group II-bronchoscopy in combination with BAL, subdivided according to pulmonary function: group IIa (normal function), group IIb (restrictive ventilatory disturbances) and group IIc (obstructive ventilatory disturbances). Spirometry was made before and after the bronchoscopic procedure. Baseline hemoglobin saturation was compared to the lowest level during the procedure. Functional worsening caused by the procedure was observed with a decrease in forced vital capacity (FVC), forced expiratory volume in the first second (FEV(1)) and Hemoglobin saturation in all groups. Comparison between groups showed no significant difference regarding the changes in FVC (P=0.8324), FEV(1) (P=0.6952) and hemoglobin saturation (P=0.5044). We conclude that standardized BAL, like the one used in our study, does not result in an increased risk for ventilatory impairment compared to bronchoscopy itself, independently of the presence of previous respiratory disease.

Role of bronchoscopy in asthma research

Over the past 15 years, much has been learned about the presence of airway inflammation in asthma through the use of investigative bronchoscopy. It has become quite clear that inflammation is present even in mild asthma. In addition to the eosinophils, T-lymphocytes and a variety of cytokines have been identified to play a prominent role in asthmatic inflammation. The concept of delayed asthmatic response after allergen exposure and its relationship to cellular inflammation and airway hyper-reactivity has become more clearly established. Our understanding of asthmatic airway inflammation, however, is incomplete. As interesting as the database has been so far, investigative FB has not defined a unique profile for patients with asthma. Specifically, lavage or endobronchial biopsy has not identified parameters that help in the diagnosis, assessment of disease severity, prognosis, or likelihood to respond to specific therapies. Also, the exact relationship between parameters in lavage compared with mucosal biopsy and how these are related to airway hyper-reactivity and the clinical syndrome of asthma remains poorly understood. In this regard, it must be confessed that currently FB with lavage and biopsy in asthmatics needs to be considered as a research tool for specimen retrieval to help characterize and express inflammation. Although these techniques have contributed immensely to our understanding of asthma pathogenesis, presently these techniques do not have any practical role or clinical usefulness.

Intrapulmonary cytokine accumulation following BAL and the role of endotoxin contamination

STUDY OBJECTIVES

BAL induces alveolar inflammation, but its effects on intrapulmonary cytokines and the mechanisms causing inflammation are uncertain. The objectives of this study were: (1) to characterize cytokine response in the lungs to BAL, and (2) to determine whether endotoxin is introduced into the lungs during BAL, which could promote BAL-induced inflammation.

DESIGN AND METHODS

We performed two BAL procedures in healthy volunteers separated by 4 (n=6), 24 (n=5), or 72 h (n=3). The initial BAL was performed in the right middle lobe (RML) and the second BAL was performed in the same location and the lingula. Concentrations of interleukin-8 (IL-8), interleukin-1 (IL-1beta), and transforming growth factor-beta were measured by enzyme-linked immunosorbent assay and tumor necrosis factor-alpha (TNF-alpha) bioactivity was determined. Endotoxin contents of saline (10 and 20 mL) infused through bronchoscopes as well as BAL fluids recovered from six subjects were assessed by limulus amebocyte assay.

RESULTS

At 4 h after the initial lavage, but not at later times, BAL fluid recovered from the RML contained increased concentrations of IL-8 and IL-1beta, and increased TNF-alpha bioactivity. BAL fluid recovered from the lingula contained increased concentrations of TNF-alpha only at 4 h. All BAL samples tested contained detectable endotoxin as did all saline aliquots instilled through bronchoscopes.

CONCLUSIONS

There is intrapulmonary accumulation of the cytokines TNF-alpha, IL-8, and IL-1beta in the lavaged lung within 4 h after BAL; this accumulation resolves by 24 h. Endotoxin contamination of the lungs during bronchoscopy may contribute to BAL-induced lung inflammation.

Investigative use of bronchoscopy in asthma

The incorporation of bronchoscopy and bronchoscopic procedures into the investigation of asthma mechanisms, treatment, and in particular, the role of airway inflammation has contributed significantly to the enhanced understanding of this disease. Carefully drafted guidelines have allowed the gradual inclusion of subjects with more severe disease in studies utilizing bronchoscopic investigative tools. Many more questions remained unanswered, including the importance of persistence of airway inflammation in asymptomatic asthma, the specific antiinflammatory effects of new (and old) asthma therapies, the contribution of airway structural changes (subepithelial fibrosis) to nonreversible obstruction, the role of antiinflammatory versus proinflammatory cytokines in the pathogenesis of airway inflammation and the heterogeneity of disease expression in various groups of subjects. We are confident that current and future meticulously designed and executed research studies utilizing bronchoscopic techniques will significantly add to our knowledge of disease mechanisms and lead us to new and improved treatments for asthma.

Late allergic airway response to segmental bronchopulmonary provocation in allergic subjects is related to peripheral blood basophil histamine release

BACKGROUND

Basophil histamine release has been found to correlate with the presence and severity of allergic disease. However, it remains to be established whether airway response to antigen is related to basophil involvement and its release of histamine.

OBJECTIVE

The purpose of this study was to investigate whether the intensity of airway response to an inhaled antigen challenge in allergic subjects is related to IgE-dependent peripheral blood basophil histamine release.

METHODS

The response to segmental bronchoprovocation with antigen was examined in 34 subjects with allergic rhinitis. Bronchoalveolar lavage samples were obtained 5 minutes (immediate response) and 48 hours (late response) after allergen challenge. Peripheral blood maximal basophil histamine release (MBHR) in response to in vitro antigen stimulation was determined in each subject before segmental bronchoprovocation.

RESULTS

Bronchoalveolar lavage samples obtained during immediate response showed an increase in histamine, whereas the late response was noted for a marked enhancement in airway cells, particularly eosinophils. Interestingly, a significant correlation (r = 0.73, p < 0.0001, Spearman Rank test) was noted between MBHR and intensity of bronchoalveolar lavage eosinophilia at 48 hours. Furthermore, subjects with high (> or = 20%) MBHR had significantly higher total cells and eosinophils in bronchoalveolar lavage fluid 48 hours after antigen segmental bronchoprovocation when compared with subjects with low (< 20%) MBHR.

CONCLUSION

Our data suggest that the intensity of airway eosinophilia in response to antigen challenge is correlated with the magnitude of basophil mediator release in allergic subjects.

Cells and mediators in bronchoalveolar lavage of asthmatic patients: the example of eosinophilic inflammation

Bronchoalveolar lavage (BAL) greatly improved our understanding of asthma allowing to demonstrate the key role of inflammation in the pathogenesis of the disease. BAL is a safe procedure, even in severe patients when properly performed. BAL samples large and small airways and alveoli. Cells and mediators may be measured in BALF but they only represent an indirect estimation of the bronchial inflammation. Before performing BAL, the clinical status of the patients should be ascertained and drugs taken may have to be withdrawn. BALF markers should follow some requirements: (1) markers should be released by cells that are pertinent to airways inflammation (and reparation) in asthma, and, if possible they should be specific of a single cell type, (2) the enumeration of cells or titration of the marker or of its metabolites should be specific and sensitive, (3) if possible the titration should not be modified by the sampling procedure, (4) pilot studies should have demonstrated that the cell is increased or the secretory product is released during challenge in asthmatic subjects, (5) studies in a large number of patients should have demonstrated that the levels of the marker are increased in chronic asthmatics, that these levels are correlated with the severity of the disease and are decreased during effective anti-inflammatory treatment, and (6) if possible the cell or marker should be specific to asthma (but at present there is no such cell or marker). Eosinophils and granule secretory products follow most of these requirements. BAL represents an important research tool to assess the effects of therapeutic interventions.