Three-component model of pulmonary mechanical activity

Abstract

The article provides a review of key studies of the hypothesis about an independent pulmonary mechanical activity: from phylogenic analysis of respiratory movements in amphibians and mammals to respiratory mechanics research. The airflow interruption method revealed negative elastic lung hysteresis. Given the basic physical laws (the first and the second laws of thermodynamics), this paradox was considered as evidence of the independent mechanical activity of the lungs. Predominance of breathing-related pressure fluctuations in an obstructed bronchus over the intrathoracic pressure amplitude was considered as a manifestation of the regional pulmonary mechanical activity. Experimental studies of respiratory mechanics allowed formulation a hypothesis about three levels of pulmonary mechanical activity. The integral pulmonary mechanical activity provides inspiratory and expiratory movements. Smooth muscles of the bronchial wall keep the bronchial lumen during expiration and preclude valvular obstruction of the bronchus (the second level of the mechanical activity). The inspiratory action of the smooth muscles in distal parts of the lungs is a functional component along with surfactant that provides the consistency of alveoli during expirations (the third component).