Hi
Heterogeneity almost normally, is resulted from parenchymal stiffening and parallel ventilation in small airways because of altered time constant due to inappropriate association between R and C. PEEP also induce heterogeneity because of inherent effect of gas pressure on critical collapse statue. Selection of a specific PEEP level is important, so that moderate PEEP could insuflate some area, leaving collapsed the others. So maximal (Non dangerous) PEEP should be implemented for least effect on PFTs.
Yes probably this is the way how pneumonia starts resolving during positive pressure ventilation in patients of ARDS. Pneumothorax is the extreme of the condition and certainly not related to bursting of over distended alveoli as commonly perceived.
Aside from the the effect of heterogeneity resulted from collapse inside the airways, moderate inhomogeneity is associated to surfactant deficit which allows uneven ventilation and shunting occurred due to altered collapse "pressure" and the most powerful factors are intrinsic PEEP and air-trapping which worsen the condition.
Other than air leak syndrome I will also worry about the V/Q mismatch. Inhomogenous lung disease can easily lead to this problem and the oxygenation can spiral down precipitously.
Yes! surely this is precisely one of the mechanism for the resistant hypoxaemia.
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