In unilateral lung disease, it is well known that good lung dependent position has higher Pao2 than bad lung dependent lateral decubitus position, Usually the lung base is more perfused and more ventilated than the apex because of gravity and
lung
weight. But infants have the floppier chest wall than adults and the resting pleural pressure in infants in more positive than that of adult. In infants, peripheral airways on dependent lung regions may be easily closed and therefore infants have
large
closing volume. In fact, it is well known that infants have higher Pao2 at bad lung dependent position than at good lung dependent position in unilateral lung disease.
We assumed that in adult if closing volume is increased, bad lung dependent position could have higher Pao2 than good lung dependent position.
In 39 patients with unilateral parenchymal lung disease, we analysed chages of blood gas status in various body position (supine, right and left decubitus). Spirometry and closing volume were measured in 18 patients.
@ES the results are as follows.
@EN 1) In patients with higher Pao2 at good lung dependent position, eman Pao2 was 88.5?5.1 mmHg at good lung dependent position and 78.6?3.3 mmHg at bad lung dependent position(P<0.001).
2) In patients with higher Pao2 at bad lung dependent position, mean Pao2 was 79.4?.3 mmHg at good lung dependent position and 87.9?.2 mmHg at bad lung dependent position(P<0.001).
3) Closing volumes were significantly different between patients with higher Pao2 at good lung dependent position and patients with higher Pao2 at bad lung dependent position(87.8?3.6 vs, 12?8.8%, p<0.05)
From these results, we observed that patients with increased closing volume could have higher Pao2 at bad lung dependent position than at good lung dependent position.
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