Airway and lung parenchyma
The smallest airways are surrounded by alveoil. The diameter of these very flaccid airways is highly determined by the fact that the alveoli act as springs which distend lung airways. (In pathological conditions obviously thickening of the airway wall by inflammatory processes, and accumulation of secretions, also play a role). When the lung is inflated the alveolar pull applied to the airways increases, and consequently they become wider. The less elastic the lung, and the lower lung volume, the less the elastic traction applied to peripheral airways. In this respect the neonate's position is disadvantageous, as we learned earlier from the pressure-volume curve of the lung. We need to study the study the pressure-volume curve of the lung in greater detail to put this disadvantage into a clearer perspective.