Pleural Elastance Research Articles

Model-based Estimation of Neonatal Pleural Pressure

Spontaneous breathing during mechanical ventilation is common in the neonatal intensive care unit. The breathing efforts in spontaneous breaths generate negative pressures in the pleural space, complicating model-based analysis due to unknown parameter tradeoff. This paper estimates the pleural pressure and elastance in a single compartment model applied to data from a neonate undergoing synchronous intermittent mandatory ventilation. Two sets of 60 breaths were analysed. Resistance is empirically modelled based on endotracheal tube dimensions. Breath-to-breath elastance is estimated from expiration data, assuming passive expiration, and inspiratory pleural pressure is modelled using B-spline functions. Typical breathing trends were observed, patient-triggered inspiration was apparent, and the work of breathing was significantly decreased in ventilator supported breaths compared to unsupported breaths. Additionally, examples of ventilator-patient asynchrony were observed when comparing pleural pressure to airway pressure. This study contributes to the development of computational models for respiration mechanics. The fundamental aim is to provide clinicians with more physiological insight and tools to improve neonatal ventilation support.

The impact of spontaneous cough on pleural pressure changes during therapeutic thoracentesis

Cough during therapeutic thoracentesis (TT) is considered an adverse effect. The study was aimed to evaluate the relationship between cough during TT and pleural pressure (Ppl) changes (∆P). Instantaneous Ppl was measured after withdrawal of predetermined volumes of pleural fluid. Fluid withdrawal (FW) and Ppl measurement (PplM) periods were analyzed separately using the two sample Kolmogorov–Smirnov test and the nonparametric skew to assess differences between ∆P distributions in periods with and without cough. The study involved 59 patients, median age 66 years, median withdrawn fluid volume 1800 mL (1330 ÷ 2400 mL). In total, 1265 cough episodes were recorded in 52 patients, in 24% of FW and 19% of PplM periods, respectively. Cough was associated with significant changes in ∆P distribution (p < 0.001), decreasing the left tail of ∆P distribution for FW periods (the skew = − 0.033 vs. − 0.182) and increasing the right tail for PplM periods (the skew = 0.182 vs. 0.088). Although cough was more frequent in 46 patients with normal pleural elastance (p < 0.0001), it was associated with significantly higher ∆P in patients with elevated elastance (median Ppl increase 2.9 vs. 0.2 cmH2O, respectively). Cough during TT is associated with small but beneficial trend in Ppl changes, particularly in patients with elevated pleural elastance, and should not be considered solely as an adverse event.

Association between terminal pleural elastance and radiographic lung re-expansion after therapeutic thoracentesis in patients with symptomatic pleural effusion: a post-hoc analysis of a randomised trial

ObjectivesRecurrent symptomatic effusions can be durably managed with pleurodesis or placement of indwelling pleural catheters. Recent pleurodesis trials have largely relied on lung re-expansion on post-thoracentesis radiograph as an inclusion...

Impact of therapeutic thoracentesis and pleural pressure changes on breathing pattern, dyspnea, lung function, and arterial blood gases.

Therapeutic thoracentesis is highly effective in providing symptomatic improvement in patients with large volume pleural effusion (PE). However, some physiological effects of pleural fluid (PF) withdrawal are still not fully elucidated. The study aimed to evaluate alterations in the breathing pattern, pulmonary function, and arterial blood gases (ABG) in relation to both withdrawn PF volume and pleural pressure (Ppl) changes in patients undergoing therapeutic thoracentesis. This prospective, observational, cross‑sectional study included 37 patients with large volume PE. Respiratory rate (RR), dyspnea, pulmonary function, and ABG were assessed before the thoracentesis, at the termination of the PF withdrawal and 1, 3, and 24 hours after the procedure. The volume of PF drained, Ppl, and tidal volume (TV) were monitored during the thoracentesis. Thoracentesis resulted in a transient but significant increase in RR directly after the procedure, and a transient decrease, followed by subsequent increase in TV. There was a significant and constant increase in forced vital capacity up to 24 hours after thoracentesis (P = 0.001). Oxygen partial pressure (PaO2) significantly improved directly after PF withdrawal (P = 0.01) and returned to baseline values after 24 hours. Thoracentesis was invariably associated with a significant increase in the amplitude of Ppl (Ppl_ampl) changes during the respiratory cycle (P <0.001). Therapeutic thoracentesis results in a modest improvement in pulmonary function, tran-sient increase in PaO2 and increase in Ppl_ampl. The improvement in pulmonary function and ABG is closely related to the volume of PF drained and pleural elastance. The increase in Ppl_ampl probably represents a more efficient work of the respiratory muscles.

Pleural Space Elastance and Its Relation to Success Rates of Pleurodesis in Malignant Pleural Effusion.

BackgroundPleurodesis fails in 10%–40% of patients with recurrent malignant pleural effusions malignant pleural effusion and dyspnea. This study aimed to assess the values of pleural elastance (PEL) after the aspiration of 500 mL of pleural fluid and their relation to the pleurodesis outcome, and to compare the pleurodesis outcome with the chemical characteristics of pleural fluid.MethodsA prospective study was conducted in Kasr El-Aini Hospital, Cairo University, during the period from March 2019 to January 2020. The study population consisted of 40 patients with malignant pleural effusion. The measurement of PEL after the aspiration of 500 mL of fluid was done with “PEL 0.5” (cm H2O/L), and the characteristics of the pleural fluid were chemically and cytologically analyzed. Pleurodesis was done and the patients were evaluated one month later. The PEL values were compared with pleurodesis outcomes.ResultsAfter 4-week of follow-up, the success rate of pleurodesis was 65%. The PEL 0.5 was significantly higher in failed pleurodesis than it was in successful pleurodesis. A cutoff point of PEL 0.5 >14.5 cm H2O/L was associated with pleurodesis failure with a sensitivity and specificity of 93% and 100%, respectively. The patients with failed pleurodesis had significantly lower pH levels in fluid than those in the successful group (p<0.001).ConclusionPEL measurement was a significant predictor in differentiating between failed and successful pleurodesis. The increase in acidity of the malignant pleural fluid can be used as a predictor for pleurodesis failure in patients with malignant pleural effusion.

Manometry performed at indwelling pleural catheter insertion to predict unexpandable lung.

BackgroundThe finding of unexpandable lung (UL) at an early timepoint is of increasing importance in guiding treatment decisions in patients with malignant pleural effusion (MPE). Pleural manometry is the most common technique to delineate UL, however it has never been measured via an indwelling pleural catheter (IPC). To further the evidence base we analysed all patients in the IPC-PLUS study who had manometry performed during IPC insertion for the ability to predict substantial UL using manometry.MethodsAll patients enrolled in IPC-PLUS who had manometry performed at IPC insertion and radiographic assessment of UL at day 10 were included. Elastance curves were visually inspected for each patient. Initial pleural pressure, closing pleural pressure, and terminal elastance were analysed for their differences and predictive ability in those with substantial UL, defined as ≥25% entrapment on chest radiography.ResultsA total of 89 patients had manometry performed at IPC insertion with subsequent radiographic assessment of UL and interpretable elastance curves. Those with substantial UL had a significantly lower median closing pleural pressure (−15.00 vs. 0.00 cmH2O, P=0.012) and higher terminal elastance (12.03 vs. 8.59 cmH2O/L, P=0.021) compared to a combined group with no or partial UL. However, the predictive ability of these factors to discriminate substantial UL was poor, with areas under the receiver operating characteristic curves of 0.695 and 0.680 for closing pleural pressure and elastance respectively.ConclusionsOur results suggest that manometry is not useful in accurately predicting substantial UL when used via an IPC at the time of insertion.

The Relationship of Pleural Manometry With Postthoracentesis Chest Radiographic Findings in Malignant Pleural Effusion

Both elevated pleural elastance (E-PEL) and radiographic evidence of incomplete lung expansion following thoracentesis have been used to exclude patients with a malignant pleural effusion (MPE) from undergoing pleurodesis. This article reports on a cohort of patients with MPE in whom complete drainage was attempted with pleural manometry to determine the frequency of E-PEL and its relation with postthoracentesis radiographic findings. Seventy consecutive patients with MPE who underwent therapeutic pleural drainage with pleural manometry were identified. The pressure/volume curves were constructed and analyzed to determine the frequency of E-PEL and the relation of PEL to the postthoracentesis chest radiographic findings. E-PEL and incomplete lung expansion were identified in 36 of 70 (51.4%) and 38 of 70 (54%) patients, respectively. Patients with normal PEL had an OR of 6.3 of having complete lung expansion compared with those with E-PEL (P= .0006). However, 20 of 70 (29%) patients exhibited discordance between postprocedural chest radiographic findings and the pleural manometry results. Among patients who achieved complete lung expansion on the postdrainage chest radiograph, 9 of 32 (28%) had an E-PEL. In addition, PEL was normal in 11 of 38 (34%) patients who had incomplete lung expansion as detected according to the postthoracentesis chest radiograph. E-PEL and incomplete lung expansion postthoracentesis are frequently observed in patients with MPE. Nearly one-third of the cohort exhibited discordance between the postprocedural chest radiographic findings and pleural manometry results. These findings suggest that a prospective randomized trial should be performed to compare both modalities (chest radiograph and pleural manometry) in predicting pleurodesis outcome.

Assessment of Diaphragm Function and Pleural Pressures During Thoracentesis

This prospective observational study reports on diaphragm excursion, velocity of diaphragm contraction, and changes in pleural pressure that occur with thoracentesis. Twenty-eight patients with pleural effusion underwent therapeutic thoracentesis. Diaphragm excursion and velocity of diaphragm contraction were measured with M-mode ultrasonography of the affected hemidiaphragm. Pleural pressure was measured at each aliquot of 250mL of fluid removal. Fluid removal was continued until no more fluid could be withdrawn, unless there was evidence of nonexpandable lung defined as a pleural elastance greater > 14.5cm H2O/L and/or ipsilateral anterior chest discomfort. Twenty-three patients had expandable lung, and five patients had nonexpandable lung. Velocity of diaphragm contraction (mean ± SD) increased from 1.5 ± 0.4cm/s to 2.8 ± 0.4cm/s pre-thoracentesis and post-thoracentesis, respectively (CI, 0.93-1.61; P< .001) in subjects with expandable lung. Velocity of diaphragm contraction (mean ± SD) increased from 2.0 ± 0.4cm/s to 2.3 ± 0.4cm/s pre-thoracentesis and post-thoracentesis (P= .45) in subjects with nonexpandable lung. Diaphragm excursion was significantly increased in subjects with expandable lung at the end of thoracentesis; diaphragm excursion did not increase to a significant extent in patients with nonexpandable lung. The velocity of diaphragm contraction and diaphragm excursion increased in association with fluid removal with thoracentesis in patients with expandable lung, whereas it did not significantly change in patients with nonexpandable lung. This may derive from improvement in loading conditions of the diaphragm in patients with expandable lung related to its preload and length-tension characteristics.

Pre-EDIT: A Randomized Feasibility Trial of Elastance-Directed Intrapleural Catheter or Talc Pleurodesis in Malignant Pleural Effusion

Talc slurry pleurodesis (TSP) prevents recurrence of symptomatic malignant pleural effusion (MPE) in 71%to 78%patients. Nonexpansile lung (NEL) frequently accounts for TSP failure but is often occult predrainage, impairing selection of patients. NEL is associated with high pleural elastance (PEL), but technical limitations have hampered the development of PEL as a predictive NEL marker. We performed a single-center, randomized, controlled, open-label feasibility trial of EDIT (elastance-directed indwelling pleural catheter or TSP) management, using a novel digital manometer and a new definition of high PEL. Patients with symptomatic MPE were randomized 1:1 between EDIT and standard care (TSP). EDIT involved PEL assessment during large-volume thoracentesis; patients with high PEL (maximum PEL sustained over 250mL [MaxPEL250]≥ 14.5cm H2O/L) were allocated to immediately receive an indwelling pleural catheter; the remainder underwent immediate drain placement for TSP. The primary outcome measure was recruitment feasibility, defined a priori as 30 patients over 12months. Secondary outcomes included safety, technical reliability, and the aspiration volume required to detect high PEL. The accuracy of the PEL definition for NEL was analyzed post hoc. Thirty-one patients were randomized (one allocation failure) over 12months. PEL assessment (mean duration, 33 minutes) was successful in 13 of 15 patients (87%). No directly attributable serious adverse events occurred. High PEL was detected in seven of 13 patients (54%), associated with 100%sensitivity and 67%specificity for NEL, and was first detected at a median volume of 325mL (range, 250-800mL). A phase 3 trial testing the effect of EDIT management on symptomatic MPE recurrence following TSP is feasible. ClinicalTrials.gov; No.: NCT03319186; URL: www.clinicaltrials.gov.

What happens to the pleural space affected by malignant effusion after bedside pleurodesis?

Evaluate radiological characteristics of postpleurodesis pleural space of patients with recurrent malignant pleural effusion(RMPE). Prospective cohort study including patients with RPME treated with bedside pleurodesis. We used CT scans to calculate pleural cavity volume immediately before pleurodesis(iCT) and 30 days after(CT30). Radiological evolution was calculated by the difference between pleural volumes on CT30 and iCT(Δvolume). We categorized initial pleural volume as small(<500 mL) or large space(≥500 mL) and Δvolume as positive(>254.49 mL), unchanged(≥-268.77-≤ 254.49 mL), or negative(<-268.77 mL). Futhermore, we analyzed clinical effectiveness, pleural elastance, and adverse events. A total of 87 patients were analyzed. Pleural volume varied from 35-2750 mL in iCT and from 0-2995 mL in CT30(P = 0.753). A total of 54 patients had initial small pleural space(62.06%) and 33 large(37.93%). Clinical failure occurred in 7.4% of small space group and in 24.6% of large(P = 0.051, OR4.0(CI:1.098-14.570)). In small space group, 27.77% evolved with positive, 66.66% with unchanged and 5.55% with negative Δvolume. In the large space group these numbers were respectively 21.21%, 27.27%, and 51.51%. There is significant variability on pleural space volume. However, pleural volume remains unchanged in many cases. Besides that, more than half patients with initial large space coursed with relevant reduction. Finally, patients with initial small space presented a greater chance of clinical success.

Pleural manometry in patients with pleural diseases - the usefulness in clinical practice.

Although pleural manometry is a relatively simple medical procedure it is only occasionally used to follow pleural pressure (Ppl) changes during a therapeutic thoracentesis and pneumothorax drainage. As some studies showed that pleural pressure monitoring might be associated with significant advantages, pleural manometry has been increasingly evaluated in the last decade. The major clinical applications of pleural pressure measurements include: the prevention of complications associated with large volume thoracentesis, diagnosis and differentiation between various types of an unexpandable lung and a possible prediction of the efficacy of chest tube drainage in patients with spontaneous pneumothorax. It is well known that the therapeutic thoracentesis might be complicated by cough, chest discomfort, and rarely, by a life threatening condition called reexpansion pulmonary edema (RPE). The serious adverse events of thoracentesis are related to pleural pressure drop rather than to the volume of removed pleural effusion. The use of pleural manometry during pleural fluid withdrawal enables the evaluation of the relationship between withdrawn pleural fluid volume, pleural pressure changes and procedure related complications. Pleural pressure measurement is also an important tool to study the different mechanism of pneumothorax complicating the thoracentesis. Pleural manometry is critical for measurement of pleural elastance, diagnosis of an unexpandable lung and differentiation between trapped lung and lung entrapment. This usually has significant clinical implications in terms of further management of patients with pleural effusion. The paper is a comprehensive review presenting different aspects of pleural pressure measurement in clinical practice.

Novel Use of Pleural Ultrasound Can Identify Malignant Entrapped Lung Prior to Effusion Drainage

The presence of entrapped lung changes the appropriate management of malignant pleural effusion from pleurodesis to insertion of an indwelling pleural catheter. No methods currently exist to identify entrapped lung prior to effusion drainage. Our objectives were to develop a method to identify entrapped lung using tissue movement and deformation (strain) analysis with ultrasonography and compare it to the existing technique of pleural elastance (PEL). Prior to drainage, 81 patients with suspected malignant pleural effusion underwent thoracic ultrasound using an echocardiogram machine. Images of the atelectatic lower lobe were acquired during breath hold, allowing motion and strain related to the cardiac impulse to be analyzed using motion mode (M mode) and speckle-tracking imaging, respectively. PEL was measured during effusion drainage. The gold-standard diagnosis of entrapped lung was the consensus opinion of two interventional pulmonologists according to postdrainage imaging. Participants were randomly divided into development and validation sets. Both total movement and strain were significantly reduced in entrapped lung. Using data from the development set, the area under the receiver-operating curves for the diagnosis of entrapped lung was 0.86 (speckle tracking), 0.79 (M mode), and 0.69 (PEL). Using respective cutoffs of 6%, 1 mm, and 19 cm H2O on the validation set, the sensitivity/specificity was 71%/85% (speckle tracking), 50%/85% (M mode), and 40%/100% (PEL). This novel ultrasound technique can identify entrapped lung prior to effusion drainage, which could allow appropriate choice of definitive management (pleurodesis vs indwelling catheter), reducing the number of interventions required to treat malignant pleural effusion.

Comparison of Pleural Pressure Measuring Instruments

The objective of this study was to compare the accuracy of a handheld digital manometer (DM) and U-tube (UT) manometer with an electronic transducer (ET) manometer during thoracentesis. Thirty-three consecutive patients undergoing thoracentesis were enrolled in the study. Pleural pressure (Ppl) measurements were made using a handheld DM (Compass; Mirador Biomedical), a UT water manometer, and an ET (reference instrument). End-expiratory Ppl was recorded after catheter insertion, after each aspiration of 240 mL, and prior to catheter removal. Volume of fluid removed, symptoms during thoracentesis, pleural elastance, and pleural fluid chemistry were also evaluated. A total of 594 Ppl measurements were made in 30 patients during their thoracenteses. There was a strong linear correlation coefficient between elastance for the DM and ET (r = 0.9582, P < .001). Correlation was poor between the UT and ET (r = 0.0448, P = .84). Among the 15 patients who developed cough, recorded ET pressures ranged from -9 to +9 cm H2O at the time of symptom development, with a mean (SD) of -2.93 (4.89) cm H2O. ET and DM measurements among those patients with cough had a low correlation between these measurements (R2 = 0.104, P = .24). Nine patients developed chest discomfort and had ET pressures that ranged from -26 to +6 cm H2O, with a mean (SD) of -7.89 (9.97) cm H2O. The handheld DM provided a valid and easy-to-use method to measure Ppl during thoracentesis. Future studies are needed to investigate its usefulness in predicting clinically meaningful outcomes.

Relationship Between the Success of Bedside Pleurodesis and Pleural Elastance in Recurrent Malignant Pleural Effusion

SESSION TITLE: Malignant Pleural Disease Posters

A New Method for Performing Continuous Manometry during Pleural Effusion Drainage

Background: Pleural manometry can predict the presence of trapped lung and guide large-volume thoracentesis. The current technique for pleural manometry transduces pressure from the needle or intercostal catheter, necessitating intermittent cessation of fluid drainage at the time of pressure recordings. Objectives: To develop and validate a technique for performing continuous pleural manometry, where pressure is transduced from an epidural catheter that is passed through the drainage tube to sit within the pleural space. Methods: Pleural manometry was performed on 10 patients undergoing thoracentesis of at least 500 ml, using the traditional intermittent and new continuous technique simultaneously, and pleural pressures were recorded after each drainage of 100 ml. The pleural elastance (PEL) curves and their 95% confidence intervals (CIs), derived using measurements from each technique, were compared using the analysis of covariance and Student's paired t test, respectively. Results: There was no significant difference in PEL calculated using each method (p > 0.1); however, there was a trend towards the CI for the PEL derived from the continuous method being narrower (p = 0.08). Fully automated measurement of drainage volume and pleural pressure, with real-time calculation and display of PEL, was achieved by connecting the system to a urodynamics machine. Conclusions: Pleural manometry can be transduced from an epidural catheter passed through the drainage tube into the pleural space, which gives continuous recording of the pleural pressure throughout the procedure. This allows for automated calculation and display of the pleural pressure and PEL in real time, if the system is connected to a computer with appropriate software.

Plasminogen Activator Inhibitor-1 Deficiency Augments Visceral Mesothelial Organization, Intrapleural Coagulation, and Lung Restriction in Mice with Carbon Black/Bleomycin–Induced Pleural Injury

Local derangements of fibrin turnover and plasminogen activator inhibitor (PAI)-1 have been implicated in the pathogenesis of pleural injury. However, their role in the control of pleural organization has been unclear. We found that a C57Bl/6j mouse model of carbon black/bleomycin (CBB) injury demonstrates pleural organization resulting in pleural rind formation (14 d). In transgenic mice overexpressing human PAI-1, intrapleural fibrin deposition was increased, but visceral pleural thickness, lung volumes, and compliance were comparable to wild type. CBB injury in PAI-1(-/-) mice significantly increased visceral pleural thickness (P < 0.001), elastance (P < 0.05), and total lung resistance (P < 0.05), while decreasing lung compliance (P < 0.01) and lung volumes (P < 0.05). Collagen, α-smooth muscle actin, and tissue factor were increased in the thickened visceral pleura of PAI-1(-/-) mice. Colocalization of α-smooth muscle actin and calretinin within pleural mesothelial cells was increased in CBB-injured PAI-1(-/-) mice. Thrombin, factor Xa, plasmin, and urokinase induced mesothelial-mesenchymal transition, tissue factor expression, and activity in primary human pleural mesothelial cells. In PAI-1(-/-) mice, D-dimer and thrombin-antithrombin complex concentrations were increased in pleural lavage fluids. The results demonstrate that PAI-1 regulates CBB-induced pleural injury severity via unrestricted fibrinolysis and cross-talk with coagulation proteases. Whereas overexpression of PAI-1 augments intrapleural fibrin deposition, PAI-1 deficiency promotes profibrogenic alterations of the mesothelium that exacerbate pleural organization and lung restriction.

Pleural Pressure Swing and Lung Expansion After Malignant Pleural Effusion Drainage

Malignant pleural effusion is a common complication in end-stage cancer patients and can cause severe dyspnea. Therapeutic thoracentesis is often limited to 1 to 1.5 L. Pleural manometry can be used to recognize a not-expanded lung. Interval pleural pressure measurements with a high temporal resolution were performed after each removal of 200 mL of fluid to observe pleural pressure swings. Pleural elastance was defined as the difference in pleural pressure divided by the change in volume. Chest x-rays were performed to evaluate lung expansion, reexpansion pulmonary edema, and fluid residue. Thirty-four procedures in 30 patients were eligible for analysis. Four patients had incomplete lung expansion after drainage. No reexpansion pulmonary edema was observed. Pleural pressure swing after 200 mL drainage was higher when the lung did not expand. Pleural elastance after removal of 500 mL was higher in the not-expanded subgroup. We demonstrated that a high pleural pressure swing after removal of only 200 mL was related to incomplete lung expansion. We confirmed the association between pleural elastance and lung expansion.

Large-Volume Thoracentesis and the Risk of Reexpansion Pulmonary Edema

To avoid reexpansion pulmonary edema (RPE), thoracenteses are often limited to draining no more than 1 L. There are, however, significant clinical benefits to removing more than 1 L of fluid. The purpose of this study was to define the incidence of RPE among patients undergoing large-volume (> or = 1 L) thoracentesis. One hundred eighty-five patients undergoing large-volume thoracentesis were included in this study. The volume of fluid removed, absolute pleural pressure, pleural elastance, and symptoms during thoracentesis were compared in patients who did and did not experience RPE. Of the 185 patients, 98 (53%) had between 1 L and 1.5 L withdrawn, 40 (22%) had between 1.5 L and 2 L withdrawn, 38 (20%) had between 2 L and 3 L withdrawn, and 9 (5%) had more than 3 L withdrawn. Only 1 patient (0.5%, 95% confidence interval: 0.01% to 3%) experienced clinical RPE. Four patients (2.2%, 95% confidence interval: 0.06% to 5.4%) had radiographic RPE (diagnosed only on postprocedure imaging without clinical symptoms). The incidence of RPE was not associated with the absolute change in pleural pressure, pleural elastance, or symptoms during thoracentesis. Clinical and radiographic RPE after large-volume thoracentesis is rare and independent of the volume of fluid removed, pleural pressures, and pleural elastance. The recommendation to terminate thoracentesis after removing 1 L of fluid needs to be reconsidered: large effusions can, and should, be drained completely as long as chest discomfort or end-expiratory pleural pressure less than -20 cm H2O does not develop.

The Relationship of Pleural Pressure to Symptom Development During Therapeutic Thoracentesis

To describe the relationship of patients' symptoms during therapeutic thoracentesis to pleural pressure (Ppl). Review of prospectively collected data during 169 therapeutic thoracentesis procedures. University Hospital in Boston, MA. One hundred sixty-nine patients who had Ppl measured during therapeutic thoracentesis were included in this study. End-expiratory pressures were measured after the withdrawal of 5 mL of fluid and every 240 mL thereafter until the pressure was lower than -20 cm H(2)O, chest discomfort developed in the patient, or no more fluid could be removed. Patients' symptoms, including chest pain, chest discomfort, and cough were recorded simultaneously. There was no correlation between the amount of pleural fluid removed and the development of symptoms. The closing pressures and the total change in Ppl (see the "Materials and Methods" section for definitions), however, were significantly lower in the group of patients who experienced chest discomfort compared to patients who developed cough or were asymptomatic. There was also a trend toward a significantly lower pleural elastance in patients who developed cough compared to that in the other two groups. Additionally, only 22% of patients in whom chest discomfort developed, and 8.6% of patients in whom symptoms did not develop, had potentially dangerous Ppl values (ie, lower than -20 cm H(2)O). The development of chest discomfort is associated with a potentially unsafe drop in Ppl values and should be a sign to terminate thoracentesis. It is not necessary to terminate thoracentesis solely because of the development of cough. Without attention to pleural manometry, a significant percentage of patients may develop potentially dangerous Ppl. Although we recommend pleural manometry with all thoracenteses, when it is not used attention to symptoms remains a valuable surrogate.

Measurement of pleural pressure during therapeutic thoracentesis.

The aim of therapeutic thoracentesis (TT) is to aspirate as much pleural fluid as possible. Monitoring pleural pressure (PlP) during TT has been proposed to avoid the adverse effects due to an unintended sharp drop in PlP. The objectives of this study are to ascertain the diagnostic value of the PlP measurement, to find a predictive variable of the amount of fluid that can be removed, to obtain insight into the characteristics of the PlP curve and pleural elastance (PE) during TT, and to describe the complications of TT. Sixty-one unselected patients were studied. Only the four patients with suspected trapped lung had an initial PlP lower than -4 cm H(2)O and a PE higher than 33 cm H(2)O/L. There was a weak correlation (r = 0.52) between PE during the first 0.5 L aspirated and the total amount of fluid aspirated. Partial PE values were 10, 7.5, and 14 cm H(2)O/L at the early, intermediate, and late phases of TT. No complications were found except for nine pneumothoraces. In conclusion, the technique was clinically helpful because large amounts of pleural fluid could be aspirated with few and mild complications, and because it allows clinicians to support the preliminary diagnosis of trapped lung. None of the studied variables was found to predict the suitability of aspirating more than 1.5 L. Rather than being monotonically descendent, the PlP curve shows a three-part line with the deepest slopes at the first and last phases of the thoracentesis.