Pores of Kohn: forgotten alveolar structures and potential source of aerosols in exhaled breath.

Analysis of human and animal exhaled breath has identified numerous compounds including proteins and surfactant constituents from the deep lung. Some mechanisms such as coughing, breaking of surfactant/mucus plugs, or 'bronchiole film bursting' have been proposed to explain the presence of these proteins from the deep lung but do not include possible contributions from Pores of Kohn. A re-examination of the change in diameter as well as forces exerted by surfactant film in the Pores of Kohn during normal inspiration, demonstrates that these channels should open following rupture of the surfactant film; which could generate aerosols of surfactant film constituents. Generation, of such deep-lung aerosols, is predicted to begin during inhalation when lung tissue surface area has increased by at least a factor of 2.