Bronchoalveolar lavage and other methods to define the human respiratory tract milieu in health and disease

During fiber-optic bronchoscopy (FOB), surface sampling of the human respiratory airways and alveolar unit can be done with bronchoalveolar lavage (BAL), plus selective sites can be brushed for cells and transbronchial biopsies made in adjacent tissue. This permits analysis of the respiratory tract's milieu in healthy normals, in those with disease, and in control subjects. These combined procedures have been an established approach for obtaining specimens for research and for clinical assessment for over four decades. However, now new less invasive sampling methods are emerging. This review emphasizes BAL and the cellular and noncellular components recovered in fluid that have contributed to improving knowledge of how the respiratory tree's innate immunity can protect, and how airway structures can become deranged and manifest disease. After a discussion of training for FOB and procedural issues, a spectrum of respiratory diseases studied with BAL is presented, including airway illness (asthma and chronic obstructive pulmonary disease), diffuse interstitial lung diseases [idiopathic pulmonary fibrosis, rheumatoid interstitial lung disease (ILD), granulomatous ILDs], lung infections, lung malignancy, and upper and lower tract airway problems. Some recent studies with exhaled breath condensate analyses are given.