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ONLINE FIRST This is an Online First, unedited version of this article. The final, edited version will appear in a numbered issue of CHEST and may contain substantive changes. We encourage readers to check back for the final article. Online First papers are indexed in PubMed and by search engines, but the information, including the final title and author list, may be updated on final publication. http://journal.publications.chestnet.org/

       

 

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Ver 3.0 Word Count: 1,982 Abstract: 240 Comparison of Pleural Pressure Measuring Instruments Lee HJ1*, Yarmus L1* Kidd D1, Ortiz R1, Akulian J3, Gilbert C4, Hughes A1, Thompson RE2, Arias S1, Feller-Kopman D1 1

Johns Hopkins University, Division Pulmonary/ Critical Care, Section of Interventional Pulmonology, 2Department of Biostatistics at the Johns Hopkins Bloomberg School of Public, 3 University of North Carolina, Division of Pulmonary/ Critical Care, 4Pennsylvania State University, Pulmonary/ Critical Care *Primary Co-authors

Corresponding Author: Hans J. Lee, MD Johns Hopkins Hospital 1800 Orleans Street, Zayed Building 7125L Baltimore, MD 21287 Email: [email protected] Hans J. Lee, MD Lonny Yarmus, DO David Kidd Ricardo Ortiz Jason Akulian, MD Christopher Gilbert, MD Andrew Hughes, MD Richard E. Thompson, PhD David Feller-Kopman, MD

Conflict of Interest Disclosures: None of the other authors have conflicts or disclosures Key Words: Pleural Pressure, Manometry, Thoracentesis Funding: None 1

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Ver 3.0 used a ‘damped water manometer’ to reduce this respiratory variation and showed excellent correlation with an electronic transducer system (ET)10. The benefits of the ET are continuous Ppl readings and a graphic display allowing for the accurate measurements throughout the respiratory cycle; however, this method requires additional equipment such as an arterial-line set-up (transducer, tubing, pressure bag) and hemodynamic monitor. Recently, an electronic handheld digital manometer (DM) became commercially available which can be easily attached in-line to a standard thoracentesis catheter. The purpose of this study was to validate the use of the DM by comparison to the currently available techniques of UT and ET.

Methods: The study was approved by the Johns Hopkins University Institutional Review Board (NA0006941 ). All thoracentesis procedures were conducted in an endoscopy suite at the Johns Hopkins Hospital. All patients presenting for thoracentesis (inpatient and outpatient) were included in the study. Data were collected prospectively and informed consent was obtained from all patients prior to inclusion into the study. Thoracic ultrasonography was performed to identify a safe site for pleural entry11 12. Thoracentesis was performed in an upright sitting position, using an 8 French thoracentesis catheter (Arrow-Clarke Pleura-Seal, Teleflex, Research Triangle Park, NC). After thoracentesis catheter was inserted, a 3-way stopcock was attached to the catheter. The 3-way stop cock allowed for the attachment to the ET and DM. A column of fluid was aspirated through the system (approximately 5 cc) and opening end-expiratory pleural pressure was measured using the ET, followed by the DM and UT, after at least three stable respiratory cycles were observed.

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Ver 3.0 Running Head: Comparison of Pleural Pressure Measuring Instruments Abbreviations: ET Electronic transducer DM Digital Manaomter UT U-tube Ppl pleural pressure

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Ver 3.0 Introduction Pleural effusions are commonly encountered by chest physicians and is estimated to affect 1.5 million patients per year in the United States1;2. Pleural manometry has been used since the 1800’s to better understand pleural physiology and more recently, to identify patients with nonexpandable lung3. Identifying these patients is clinically important and can help predict the success of chemical pleurodesis4. In addition, monitoring pleural (Ppl) during large volume thoracentesis may allow for optimal evacuation of pleural effusion by continuing aspiration until an excessive negative pleural pressure is reached5 6. Excessive negative pleural pressures have been associated with re-expansion pulmonary edema in animal models although it remains unknown if there is a threshold pressure for humans7.

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Despite the techniques and potential advantages of pleural manometry that have been previously described, the routine use of manometry has not been widely adopted8. A possible reason for this may be the belief that it is difficult and or time consuming. Until recently, there has not been a compact, digital, pre-packaged sterile, and commercially available pleural manometer. The potential of an easier and uniform method of measuring Ppl may lead to the development of stronger evidence to support or refute pleural manometry in clinical practice.In 1980, Light et al. described the use of an Abrams needle connected to plastic tubing for use as a U-tube shaped manometer (UT)9. Lan et al. used a slightly different system, one more similar to the manometer available with many lumbar puncture kits.3 Although, one can easily use the tubing that is part of a standard thoracentesis kit as a U-shaped manometer, it may be difficult to obtain an accurate pressure measurement due to the oscillating height of the water column with respiration as well as the presence of valves / filters in the tubing that may affect the measured pressure. Doelken 4

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Ver 3.0 used a ‘damped water manometer’ to reduce this respiratory variation and showed excellent correlation with an electronic transducer system (ET)10. The benefits of the ET are continuous Ppl readings and a graphic display allowing for the accurate measurements throughout the respiratory cycle; however, this method requires additional equipment such as an arterial-line set-up (transducer, tubing, pressure bag) and hemodynamic monitor. Recently, an electronic handheld digital manometer (DM) became commercially available which can be easily attached in-line to a standard thoracentesis catheter. The purpose of this study was to validate the use of the DM by comparison to the currently available techniques of UT and ET.

Methods: The study was approved by the Johns Hopkins University Institutional Review Board (NA0006941 ). All thoracentesis procedures were conducted in an endoscopy suite at the Johns Hopkins Hospital. All patients presenting for thoracentesis (inpatient and outpatient) were included in the study. Data were collected prospectively and informed consent was obtained from all patients prior to inclusion into the study. Thoracic ultrasonography was performed to identify a safe site for pleural entry11 12. Thoracentesis was performed in an upright sitting position, using an 8 French thoracentesis catheter (Arrow-Clarke Pleura-Seal, Teleflex, Research Triangle Park, NC). After thoracentesis catheter was inserted, a 3-way stopcock was attached to the catheter. The 3-way stop cock allowed for the attachment to the ET and DM. A column of fluid was aspirated through the system (approximately 5 cc) and opening end-expiratory pleural pressure was measured using the ET, followed by the DM and UT, after at least three stable respiratory cycles were observed.

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Ver 3.0 The system was allowed to stabilize for at least three respiratory cycles prior to recording a measurement with another measurement device.

Electronic Transducer The electronic transducer (Transpac, ICU Medical, San Clemente, CA) was flushed with sterile saline to purge the system of all air. The ET was connected to the 3-way stopcock by a 48 inch arterial monitoring line tubing. Using an IV pole with an adjustable clamp, the transducer was positioned level to the catheter insertion site and positioning was confirmed with a laser level. The transducer was then zeroed to atmospheric pressure. U-tube Manometer A disposable sterile measuring tape was affixed vertically to the patient's sterile drape for UT measurements (Figure 1). To measure pressure with the UT, the thoracentesis catheter/ tubing was held perpendicular to the measuring tape and its height adjusted until free flow of fluid at end expiration ceased draining from the tubing. If this occurred above the catheter insertion site, Ppl was positive, whereas if this occurred below catheter insertion site, the pressure was negative5. As the ET measures in mmHg, these numbers were converted to cmH2O. All measuring devices reported their pressure measurements in whole numbers. Digital Manometer The DM (Compass, Mirador Biomedical, Seattle, WA takes 16 measurements per second and reports a numeric display every 0.5 seconds (wave form scale for each individual measurement also displayed but not recorded). The male lure lock side of the DM device was also connected to the 3-way stopcock, at the port located 90 degrees from the ET connection. The syringe tubing was connected to the female side of the DM device.

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Ver 3.0

Each patient had Ppl measurements with all three instruments at catheter insertion (opening Ppl), after the removal of every 240mL aliquot (individual aspiration was performed with a 60mL syringe), and just prior to catheter removal (closing Ppl). Aspiration was terminated when 1) no additional fluid could be extracted, 2) the ET pressure dropped below -20 cm H2O, or 3) the patient complained of chest discomfort. All patients received a portable chest x-ray following the procedure to evaluate for non-expandable lung or pneumothorax. The cut off for -20 cmH20 was determined based on prior investigations arbitrarily using -20cmH20 as a threshold value7. Patient’s symptoms of chest pain and/or cough was recorded as well as their corresponding Ppl on all three instruments. The symptoms of cough and chest discomfort have been correlated with stable Ppl (coughing) and decrease in Ppl (chest discomfort). The ET manometer was used as the reference gold standard, as measurements of pressure by an ET has been the gold standard (i.e. intracranial pressure, blood pressure, intrabdominal pressure)13. . Because of the oscillation of pressure with respiration, objective monitoring of the respiratory phase for precise measurement was also used with ET as the reference gold standard.

Statistical Methods. Summary statistics (means, standard deviations, percentages, etc.) were used to describe the patient data in terms of the demographic, etiology, and Ppl observations. Next, all pairwise Pearson correlation coefficients for the Ppl measurements obtained by each of the three instruments were estimate at the predetermined aspirated volumes. All patients with measured Ppl data at a given aspirated volume were included in the correlation estimate for this

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Ver 3.0 aspiration value. Linear regressions models were then used to separately regress DM and UT Ppl values on ET Ppl values at the aspiration points where cough or chest pain occurred. These linear regression models provide an estimate of the correlation between DM and UT Ppl values, and between DM and ET, respectively, during coughing and pain events.

Finally, all the patient data were considered longitudinally by using random effect models that regressed the manometer pressure measures on aspiration volumes for all three instruments. The best linear unbiased predictions of the random effects for each person and instrument type were then estimated from these regression models, and pairwise correlations and corresponding pvalues were calculated on the random effects of slope (elastance) for the three instruments. Population average intercept and slope coefficients obtained by the fixed effects from these regression models were statistically compared by instrument type using both main effects and interaction terms in the random effects regression models. All statistical analyses were done using STATA 12.0.

Results There were a total of 594 Ppl measurements performed in 30 patients utilizing the three different manometers. Thirty of thirty-three patients had sufficient amount of effusion and underwent a successful thoracentesis with adequate pleural fluid removal to measure pleural pressure at two volumes, allowing for measurement of pleural elastance. The mean age was 65.7 years and the most common etiology was malignant effusions (Table 1). There was a strong correlation between Ppl random effects for slope for DM and ET (R2=0.9582, P