Effects of acute pleural effusion on respiratory system mechanics in dogs

Abstract

We determined regional (Vr) and overall lung volumes in six head-up anesthetized dogs before and after the stepwise introduction of saline into the right pleural space. Functional residual capacity (FRC), as determined by He dilution, and total lung capacity (TLC) decreased by one-third and chest wall volume increased by two-thirds the saline volume added. Pressure-volume curves showed an apparent increase in lung elastic recoil and a decrease in chest wall elastic recoil with added saline, but the validity of esophageal pressure measurements in these head-up dogs is questionable. Vr was determined from the positions of intraparenchymal markers. Lower lobe TLC and FRC decreased with added saline. The decrease in upper lobe volume was less than that of lower lobe volume at FRC and was minimal at TLC. Saline increased the normal Vr gradient at FRC and created a gradient at TLC. During deflation from TLC to FRC before saline was added, the decrease in lung volume was accompanied by a shape change of the lung, with greatest distortion in the transverse (ribs to mediastinum) direction. After saline additions, deflation was associated with deformation of the lung in the cephalocaudal and transverse directions. The deformation with saline may be a result of upward displacement of the lungs into a smaller cross-sectional area of the thoracic cavity.

Mechanical and morphometrical changes in progressive bilateral pneumothorax and pleural effusion in normal rats

“…In spite of the high compliance of the rib cage in rats, the present results suggest that the diaphragm-abdomen is even more compliant, as indicated by the aforementioned configurational changes. Interestingly, in dogs Dcc was also found to increase in pleural effusion but Dap and Dl were not modified [7].…”

“…The infusion of saline solution to simulate pleural effusion in dogs allowed recovery of at least 90% of the injected amount [3,7]. In previous experiments, we introduced warm (37°C) 0.9% NaCl solution in the pleural space, and after 60 min only 50% of the amount used could be recovered.…”

“…Est,L was also found to increase in pneumothorax [5] and pleural effusion [3][4][5]. Conversely, KRELL and RODARTE [7] found that the slope of pulmonary pressure-volume (P-V) curve was not changed by pleural effusion. However, the highest volume injected into the pleural space in their experiment amounted to only 45% of control total lung capacity (TLC), whereas in the present work approximately 200% of TLC was used [27,28].…”

“…There are reports mentioning a few aspects of respiratory mechanics in the presence of pneumothorax (PN) or pleural effusion (PE) [1][2][3][4][5][6][7][8][9][10], but most of them deal with spirometry [2,[4][5][6][7][8]10], pleural pressure topography [1,9], and pressure-volume curves [4][5][6][7]. In pleural effusion, only airway resistive properties [2,4,8,10], and chest wall [10] and lung compliance [4,10] were determined.…”

“…Recently [3], the measurement of total resistive and elastic properties of lung and chest wall has provided results in disagreement with those reported previously [2,4,8,10]. By superimposing radiographs, the diaphragmatic position was evaluated in pleural effusion [7]. Distribution of ventilation was also measured in pneumothorax [11] and pleural effusion [12].…”