Uncertainties in the current understanding of gas exchange in spontaneous pneumothorax: effective lung ventilation may persist in a smaller-sized pneumothorax

On the other hand, our clinical observation that patients with SP of greater size frequently differ in the severity of dyspnoea suggested the need of a more detailed analysis of the causes of hypoxaemia in these patients. The fact that hypoxaemia in these patients usually cannot be abolished by the existing hyperventilation, means that in SP of greater size, despite minimal lung volume, circulation in the pulmonary artery system still exists, causing right to left blood shunting. The fact that the severity of dyspnoea is not equal in all patients with complete SP means that hypoxic vasoconstriction exists only in some of them, following a still unknown pattern. Literature data and our measurements suggest that without further studies of hypoxic vasoconstriction in the acute phase of SP, the exact answer is not possible.