Response of Pulmonary Venous Admixture*
نویسنده
چکیده
T he efficacy of various types of pulmonary therapy is often questioned. This may stem from investigative methods. Evaluation of pulmonary gas exchange usually involves the determination of arterial oxygen tension (Pa02) and the calculation of the alveolar-to-arterial oxygen tension difference (P[Aa]O2), or pulmonary venous admixture, while pure oxygen is administered. Evaluation performed with a fractional concentration of inspired oxygen (F1o2) of 1.0 allows right-to-left intrapulmonary shunting of blood to be measured; however, the contribution of such hypoxemia-producing derangements such as abnormalities of oxygen diffusion and pulmonary areas with low but finite ventilation-to-perfusion ratios cannot be appreciated. Since different treatments can affect each of these derangements uniquely, comparisons of various therapies may be difficult and incomplete if performed only at elevated F1o2. In addition, because the administration of oxygen can affect each of these derangements differently, therapeutic efficacy may be difficult to determine with a single F1o2. We previously determined that patients with pulmonary venous admixture respond by an initial decrease and then an increase in venous admixture as the Fbi is increased.1 This biphasic response of the venous admixture represents the interactions of the various sources of venous admixtur6 in increasing F1o2. Because therapies can affect the sources of venous admixture differently, the evaluation of therapies may be better performed by examining the biphasic response of venous admixture to incre-
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تاریخ انتشار 2005