Knowledge of pleural liquid pressure (P(liq)) and composition is crucial for studies concerning intrapleural fluid dynamics, and pleural fluid turnover. We measured P(liq) at intercostal and costal levels in anaesthetized spontaneously breathing rabbits using a minimally invasive method that assures a long-lasting hydraulic continuity between the pleural liquid and the recording system. Polyethylene tubes were glued either to the exposed endothoracic fascia or inserted into a rib to provide a sealed connection to the recording system. After inducing a pneumothorax with nitrous oxide (N2O) via an intrapleural cannula, a hole (≃ 0.7 mm2) was pierced in the parietal pleura through the tube lumen. The tubes were then connected to pressure transducers and the whole system was filled with heparinized saline to the level of the parietal pleura; finally the pneumothorax was removed after N2O washout and P(liq) recordings were performed. A different kind of tube was used to obtain microsamples of pleural fluid (2.5-3 μl) during spontaneous breathing; colloid osmotic pressure of the microsamples (II(liq)) was measured with an osmometer, and averaged 9.3 ± 1.5 cmH2O (n = 70 samples). When pooled and plotted against lung height endexpiratory intercostal and costal P(liq) data scattered along a single regression line with a slope of -0.83 and -0.90 cmH2O cm-1 in supine and prone animals, respectively. End-inspiratory costal P(liq) was significantly more subatmospheric than intercostal in the ventral region of the chest (P <0.05), and less subatmospheric in the dorsal region, regardless of posture. The techniques presented here could be helpful in gaining a greater insight into the physiology and pathophysiology of the pleural space in terms of pleural fluid dynamics and turnover.
|Number of pages||14|
|Publication status||Published - Jul 1998|
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