[Confocal endomicroscopy of the lung: from the bronchus to the alveolus]

Fibred confocal fluorescence microscopy, also named probe based confocal laser endomicroscopy (pCLE), is a new endoscopic technique that can be applied for in-vivo microscopic imaging of both upper airways and distal lung structures during bronchoscopy.

Two recent in-vivo human studies using pCLE at 488nm light excitation have described the normal fluorescence endomicroscopic features of the bronchial wall and the elastic framework of the alveolus. These studies have demonstrated that elastin, a major component of the bronchial basement membrane and of the acinar elastic framework, is the main endogenous fluorophore in the non-smoking population. In smoking subjects, the tobacco tar itself is highly fluorescent and, thereby, acts as an additional fluorophore, allowing study of the macrophage alveolitis associated with smoking. These studies have also confirmed the safety of this endoscopic procedure.

In the near future, confocal endomicroscopy of the airways should make it possible to investigate the semiology of focal and diffuse distal lung diseases, to characterize cancerous and precancerous lesions of both upper and distal airways and to study the lung microcirculation. These studies may also use exogenous molecular fluorescent probes, which will enable functional imaging of the lung structures in-vivo.

Confocal endomicroscopy has the potential to explore accurately the peripheral lung in-vivo and may become a useful tool to improve endoscopic diagnosis of many lung diseases.