Volume 130, Issue 4, Pages 1173-1184 (October 2006) Pathophysiology of Pneumothorax Following Ultrasound-Guided Thoracentesis  Heidecker Jay , MD, Huggins John T. , MD, Sahn Steven A. , MD, FCCP, Doelken Peter , MD, FCCP  CHEST  Volume 130, Issue 4, Pages 1173-1184 (October 2006) DOI: 10.1016/S0012-3692(15)51155-0 Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 1 Pressure/volume curves in patients receiving pleural manometry. Top, A: Monophasic pressure/volume curves of uniform slope resulting in an E1 elastance only. These curves are from two different patients, one with normal elastance, and the other with abnormal elastance. Center, B: Biphasic pressure/volume curve with a distinct inflection point after 1,000 mL of volume removed. Note the two distinct portions of the curve, E1 and E2. Patients with biphasic curves usually have an E1 with normal elastance and have an abnormal E2. Bottom, C: Biphasic pressure/volume curve with a distinct inflection point after 250 mL removed. Note the initial steep portion of the curve, termed E0 followed by a more flat curve, E1 with normal elastance. We have observed curves with an initial steep portion followed by a more shallow section in patients with large hepatic hydrothoraces. The initial steep portion is likely be due to tension from the hydrothorax that is relieved with drainage. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 2 Flow diagram of thoracenteses in this series and postprocedural pneumothoraces. There were no pneumothoraces in patients with diagnostic thoracenteses. Of the patients with therapeutic thoracenteses, there were patients in whom intentional pneumothoraces were induced for relief of chest pain or to radiographically document unexpandable lung in patients with markedly abnormal pleural manometry findings. Postprocedure unintentional pneumothoraces were either due to direct needle trauma or due to other factors. PTX = pneumothorax; CXR = chest radiograph; CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 3 Flow diagram of patients with pleural manometry. A subset of cases with the following characteristics was isolated: biphasic curves, monophasic curves with elastances > 15.5 cm H2O/L, and radiographic evidence of unexpandable lung. The remaining 124 patients are considered to represent a sample of patients with normal pleural space physiology. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 4 Histogram of the 124 patients with normal pleural physiology. There were 124 patients without unexpandable lung by radiography, without an E2 or with an E1 < 15.5 cm H2O/L. These patients, then, have normal pleural space physiology. Patients with normal physiology have a normal distribution. The mean ± SD of this sample is 7.5 ± 3.5 cm H2O/L. Based on this finding, we defined the normal range of pleural elastance as 0.5 to 14.5 cm H2O/L (mean ± SD × 2). Thus, a pleural elastance value > 14.5 cm H2O/L is considered to represent evidence for unexpandable lung. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 5 Top, A: In the semierect chest radiograph, there is a basilar pneumothorax. In addition, note the presence of ipsilateral volume loss on the side of the pneumothorax. Center, B: Note the presence of a thick visceral pleural peel covering the lung in the hemithorax with a pneumothorax shown by CT. This peel was the most common cause of an unexpandable lung in our series. Bottom, C: Complete lobar atelectasis is also shown by CT. This patient required treatment for the pneumothorax. A tear likely developed during drainage in the severely emphysematous upper lobe. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 6 Biphasic pressure/volume curve of a patient with an unintentional postthoracentesis pneumothorax and unexpandable lung. Note biphasic pressure/volume relationship. Also note the rise in pressure at the end of the procedure (arrow). This rise is due to the unexpected pneumothorax that relieved the tension across the lung. With continued drainage, pleural pressure fell and then rose back to the same level, suggesting the pneumothorax was due to a pressure-dependent transient peripheral bronchopleural fistula. UEL = unexpandable lung. See Figure 2 legend for expansion of abbreviation. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions

Figure 7 Box plots of elastances of cases with monophasic curves with normal E, monophasic curves with abnormal E1, biphasic curves E1, biphasic curves E2, cases with cough, and cases with chest pain. The histograms show the distribution of elastances in each group. Outliers, tenth percentile, 25th percentile, median, 75th percentile, and 90th percentiles are shown. The mean and SD of each group as well as the CI of the means (in parentheses) in each group are above each box. The distribution with monophasic curves normal E1, the biphasic curves E1, and elastance in cases with cough are essentially identical; the CIs of the mean for the monophasic curves abnormal E1, as well as the biphasic curves E2, do not overlap with the patients with monophasic curve normal E1, biphasic curves E1, or cases with cough, indicating that these groups are different. The distribution of cases with chest pain is widely scattered. CHEST 2006 130, 1173-1184DOI: (10.1016/S0012-3692(15)51155-0) Copyright © 2006 The American College of Chest Physicians Terms and Conditions