PMC

Pleural fluid pH stability over time. Change in pH from baseline is shown at different time points. Mean and 95% confidence intervals are shown (95% CI). P values represent the paired t test compared with pleural fluid pH at Time 0.

Effect of the addition of heparin on pleural fluid pH. Change in pH from baseline is shown. Mean and 95% confidence intervals (95% CI) are shown. P values represent the paired t test compared with pH of pleural fluid at baseline with heparin added.

(A–D) Effect of variables on pleural fluid glucose. The graph represents change in individual samples. P values represent the paired t test compared with baseline pleural fluid glucose at Time 0. A single result has been removed from the 0.2-ml 2% lidocaine graph due to aberrant values.

Effect of the addition of air on pleural fluid pH. Change in pH from baseline is shown. Mean and 95% confidence intervals (95% CI) are shown. P values represent the paired t test compared with pH of pleural fluid at baseline without added air.

Effect of the addition of 2% lidocaine on pleural fluid pH. Change in pH from baseline is shown with increasing volumes of lidocaine. Mean and 95% confidence intervals (95% CI) are shown. P values represent the paired t test compared with pH of pleural fluid pH at baseline with no lidocaine added.