Assessment of the alveolar clearance: a critical review

Abstract

Respiratory homeostasis is fine-tuned system largely dependent on the clearance of inhaled substances from both upper and lower airways. The least studied is alveolar clearance, which, however, is crucial for the proper lung function and requires a detailed examination in order to improve the accuracy of diagnosis and treatment of lung diseases. Here, I analysed relevant literature from publicly available databases (Index Medicus, PubMed, Embase, Cochrane Library, ClinicalTrials.gov, Google Patents) to compare various methods for determining alveolar clearance, their advantages and shortcomings, their applicability in routine clinical practice and prospects for their use. The most accessible, informative, and inexpensive method to assess the alveolar clearance is bronchoalveolar lavage and the study of bronchoalveolar lavage fluid. Confocal laser endomicroscopy, a new and powerful imaging modality, has not been widely implemented hitherto. A non-invasive inhalation of a radioaerosol tracer for studying alveolar clearance in vivo seems to be promising but still requires adaptation for the broad use.