Sublobar atelectasis and regional pulmonary blood flow

Abstract

We studied the effects of sublobar atelectasis on regional blood flow in anesthetized paralyzed pigs. Following the washout of nitrogen from the lung with oxygen, a sublobar airway was obstructed and a peripheral segment of lung allowed to collapse. Blood flow to the atelectatic region fell from a control of 140.0 +/- 20.5 to 16.6 +/- 2.9 ml/(min . g). Basilar regions that became atelectatic spontaneously during the course of the studies had similar decreases in blood flow. Inflation of the surrounding lung by the application of positive end-expiratory pressure failed to increase blood flow and vascular conductance within the atelectatic regions. These results indicate that mechanical and hypoxic effects on vessels perfusing sublobar atelectatic regions limit the effects of interdependence from the surrounding lung. Furthermore, with inflation of the surrounding lung, increases in pulmonary shunting of blood are small.

Effects of Altered Patterns of Ventilation and of Increased Cardiac Output on Blood Flow to a Collapsed Lung in Anaesthetized, Closed-Chest Dogs

“…The adverse response to PEEP seen in patients with predominantly unilateral disease is less obvious in those with diffuse disease [6]. Enjeti and associates [33] have shown that there is a greater reduction in regional blood flow when collapse is restricted to a segment of lung instead of a lobe in closed-chest pigs, and that the application of PEEP does not increase flow to the collapsed segment [34]. On the other hand, Hasan and colleagues [35] found that an increase in Qs/Qt in acid aspiration injury in dogs occurred at lower PEEP values when the injury was more diffuse than when it was confined to one lung.…”

Proteomics of lung tissue reveals differences in inflammation and alveolar-capillary barrier response between atelectasis and aerated regions

“…Yet, depressed phagocytic activity of alveolar macrophages has also been reported indicating the impairment of immune function during atelectasis 10 . Additionally, reduced blood flow in atelectatic regions could further decrease local load of inflammatory cells and circulating mediators 15 .…”