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.