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Original Research: Disorders of the Pleura |

Comparison of Pleural Pressure Measuring InstrumentsPleural Pressure Measuring Instruments FREE TO VIEW

Hans J. Lee, MD, FCCP; Lonny Yarmus, DO, FCCP; David Kidd; Ricardo Ortiz; Jason Akulian, MD; Christopher Gilbert, MD; Andrew Hughes, MD; Richard E. Thompson, PhD; Sixto Arias, MD; David Feller-Kopman, MD, FCCP
Author and Funding Information

From the Division Pulmonary/Critical Care (Drs Lee, Yarmus, Hughes, Arias, and Feller-Kopman and Messrs Kidd and Ortiz), Section of Interventional Pulmonology, and the Department of Biostatistics at the Johns Hopkins Bloomberg School of Public Health (Dr Thompson), Johns Hopkins University, Baltimore, MD; the Division of Pulmonary/Critical Care (Dr Akulian), University of North Carolina, Chapel Hill, NC; and the Department of Pulmonary/Critical Care (Dr Gilbert), Pennsylvania State University, Hershey, PA.

CORRESPONDENCE TO: Hans J. Lee, MD, FCCP, Johns Hopkins Hospital, 1800 Orleans St, Zayed Bldg 7125L, Baltimore, MD 21287; e-mail: hlee171@jhmi.edu


Drs Lee and Yarmus are primary coauthors.

FUNDING/SUPPORT: The authors have reported to CHEST that no funding was received for this study.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;146(4):1007-1012. doi:10.1378/chest.13-3004
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OBJECTIVE:  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.

METHODS:  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.

RESULTS:  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.

CONCLUSIONS:  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.

Figures in this Article

Pleural effusions are commonly encountered by chest physicians and are estimated to affect 1.5 million patients per year in the United States.1,2 Pleural manometry has been used since the 1800s to better understand pleural physiology and, more recently, to identify patients with nonexpandable lung.3 Identifying these patients is clinically important and can help predict the success of chemical pleurodesis.4 In addition, monitoring pleural pressure (Ppl) during large-volume thoracentesis may allow for optimal evacuation of pleural effusion by continuing aspiration until an excessive negative Ppl is reached.5,6 Excessive negative Ppls have been associated with reexpansion pulmonary edema in animal models, although it remains unknown if there is a threshold pressure for humans.7

Despite the techniques and potential advantages of pleural manometry that have been previously described, the routine use of manometry has not been widely adopted.8 A possible reason for this may be the belief that it is difficult, time-consuming, or both. Until recently, there has not been a compact, digital, prepackaged, 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 al9 described the use of an Abrams needle connected to plastic tubing for use as a U-tube (UT) manometer. Lan et al4 used a slightly different system, one more similar to the manometer available with many lumbar puncture kits. 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 because of 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 et al10 used a “damped water manometer” to reduce this respiratory variation and showed excellent correlation with an electronic transducer (ET) system. 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 setup (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 with the currently available techniques of UT and ET.

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 entry.11,12 Thoracentesis was performed in an upright sitting position, using an 8F thoracentesis catheter (Arrow-Clarke Pleura-Seal; Teleflex Inc). After the thoracentesis catheter was inserted, a three-way stopcock was attached to the catheter. The three-way stopcock allowed for the attachment to the ET and DM. A column of fluid was aspirated through the system (approximately 5 mL), and opening end-expiratory Ppl was measured using the ET, followed by the DM and UT, after at least three stable respiratory cycles were observed. The system was allowed to stabilize for at least three respiratory cycles prior to recording a measurement with another measurement device.

Electronic Transducer

The ET (Transpac; ICU Medical, Inc) was flushed with sterile saline to purge the system of all air. The ET was connected to the three-way stopcock by a 122-cm 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.

UT Manometer

A disposable sterile measuring tape was affixed vertically to the patient’s sterile drape for UT measurements (Fig 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; if this occurred below catheter insertion site, the pressure was negative.5 As the ET measures in mm Hg, these numbers were converted to cm H2O. All measuring devices reported their pressure measurements in whole numbers.

Figure Jump LinkFigure 1 –  Images of pleural manometry devices. A, Electronic transducer monitor. B, U-tube manometer (undamped). C, Compass digital manometer.Grahic Jump Location
Digital Manometer

The DM (Compass; Mirador Biomedical) takes 16 measurements per second and reports a numeric display every 0.5 s (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 three-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.

Each patient had Ppl measurements with all three instruments at catheter insertion (opening Ppl), after the removal of every 240-mL aliquot (individual aspiration was performed with a 60-mL 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 radiograph following the procedure to evaluate for nonexpandable lung or pneumothorax. The cutoff for −20 cm H2O was determined based on prior investigations arbitrarily using −20 cm H2O as a threshold value.7 Patients’ symptoms of chest pain, cough, or both were 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 (ie, intracranial pressure, BP, intraabdominal 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, SDs, percentages, and so forth) 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 estimated at the predetermined aspirated volumes. All patients with measured Ppl data at a given aspirated volume were included in the correlation estimate for this 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 P values 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 (StataCorp LP).

There were a total of 594 Ppl measurements performed in 30 patients using the three different manometers. Thirty of 33 patients had a sufficient amount of effusion and underwent a successful thoracentesis with adequate pleural fluid removal to measure Ppl at two volumes, allowing for measurement of pleural elastance. The mean age was 65.7 years, and the most common cause was malignant effusions (Table 1).

Table Graphic Jump Location
TABLE 1 ]  Demographics

CABG = coronary artery bypass graft; CHF = congestive heart failure.

There was a strong correlation between Ppl random effects for slope for DM and ET (R2 = 0.9582, P < .001) (Table 2). In contrast, the correlation of the individual slopes from the random effects model was poor for UT and ET (R2 = 0.0448, P = .82). The fixed-effect slopes (population average) from the random-effects models for ET and DM were nearly identical (ET = −0.00527 vs DM = −0.00544, P = .006) (Fig 2), whereas there was a significant difference between the slopes from the ET and UT measurements (UT slope, −0.00285; P = .032).

Table Graphic Jump Location
TABLE 2 ]  Linear Regression Results
Figure Jump LinkFigure 2 –  Estimated slopes for all three instruments.Grahic Jump Location

Nine patients developed chest discomfort during pleural fluid aspiration, 15 of 30 patients developed coughing during aspiration, and four patients reported coughing and chest discomfort. Among the 15 patients who developed cough, recorded ET Ppl at the time of symptom development ranged from −9 to +9 cm H2O, with a mean (SD, 95% CI) of −2.93 cm H2O (4.89, −12.71 to 6.82), whereas the nine patients who developed chest discomfort had recorded ET Ppl that ranged from −26 to +6 cm H2O, with a mean (SD, 95% CI) of −7.89 cm H2O (9.97, −17.86 to 2.08).

Chest radiograph suggested nonexpandable lung in five patients by a pneumothorax ex vacuo. Measurements were highly concordant for DM and ET in the same five patients with radiographically nonexpandable lung (concordance 100%); one patient with radiographically nonexpandable lung did not have adequate volume of effusion to perform UT. UT suggested expandable lung by pleural elastance in two of five with radiographically expandable lungs.

Analysis with linear regression on the association between ET and DM measurements among those patients with cough suggests a nonsignificant low correlation between these measurements based on an R2 = 0.104 (P = .24 from the regression F statistic). In contrast, the correlation for these two measurements was highly significant for patients with chest discomfort (R2 = 0.824, P < .001). When we considered the association between manometer pressure measurements and the UT and ET, there was a statistically significant correlation between these two methods of pressure measurement, but the correlation was low among patients with cough (R2 = 0.33, P = .026), and there was a nonsignificant association when we considered the pressure data for patients with chest discomfort (R2 = 0.26, P = .14).

Despite the arguable benefits of pleural manometry, its widespread adoption has not occurred.8 A potential reason is the perceived additional time requirement and difficulty in setup of an ET manometer and no studies demonstrating a direct correlation for the benefits of pleural manometry to predict reexpansion pulmonary edema. Using an undamped UT is easily accessible since the tubing required is a part of most standard thoracentesis kits, but because of various techniques it has not been well studied.4,9,14 Only recently has a prepackaged disposable DM become available in the United States. Our data suggest that a simple, easy-to-use DM correlated well with the more complicated ET system. In contrast, the measurements from the UT did not correlate with either the DM or the ET.

The UT elastance curve did not correlate well with the ET, nor was the UT able to predict radiographic evidence of nonexpandable lung. Although the correlation pressure between the UT and ET were similar and even better at some volume points (Table 2), it was unpredictable as to when the UT manometer would correlate with the ET or DM. These differences may be partially explained by the difficulty of measuring the fluid column consistently at end expiration with respiratory oscillation of the fluid column and is the reason Doelken et al10 used an overdamped system for assessing mean pressures. The reason for testing our UT technique (undamped) was the accessibility and lack of assembly required, which would be comparable to a prepackaged DM.

Symptoms during thoracentesis are reported to be a predictor of expandable and nonexpandable lung.15 Specifically, coughing is believed to result from lung reexpansion, whereas chest discomfort is associated with excessive negative Ppls (< −20 cm H2O) and nonexpandable lung. A concern with using the DM is that the correlation significantly decreased for patients with symptoms of cough. It is unclear if these differences would be clinically significant when interpreting Ppl measurements; this would need to be assessed in a separate study with relation to meaningful clinical outcomes, which was beyond the scope of this study. In addition, our patient sample size was too small to draw any meaningful conclusion regarding specific symptoms, as we could not possibly account for false positives (chest discomfort with Ppl > −20 cm H2O), which was seen in a larger study addressing specifically symptoms.

Study Limitations

Although this study was able to prove excellent correlation between the DM and ET, testing was performed at a single center, and thus results should be validated in other centers. The DM correlated well with the ET, and the correlation remained strong in the presence of chest discomfort but became less reliable when patients developed cough. The reason for this may be the rapid pressure swings associated with coughing and difficulty for the physician to consistently identify the end-expiratory measurement. We attempted to decrease any measurement bias by waiting until cough subsided prior to taking any measurements as well as allowing three breaths in a relatively stable state. However, the reported values from the DM may have included the changes from coughing, since the measurements are made 16 measurements per second and reported every 0.5 s. If the measurements were made too soon after coughing, some of the pressure wings may have been averaged into the digital reading. The DM correlated well with radiographic nonexpandable lung in five of five cases. One proposed advantage of using DM is that it is sterile, preassembled, disposable, and commercially available in the United States. The cost of the DM is approximately US $40. Future studies are required to determine if information obtained by this method of assessing pleural elastance will be cost effective. On the other hand, there is no Current Procedural Terminology code for the additional use of manometry, and its use will add to the cost of the procedure.

This study did not specifically address the clinical relevance of pleural manometry. Instead, it provides only data for a more accessible device to measure Ppl. Our hopes is that through this, larger studies of Ppl measurement can be performed to assess its potential clinical relevance and whether there is enough value in manometry to warrant its more generalized use. Only when such relevance is proven will manometry likely be accepted in general clinical practice.

The DM provided a valid method to measure Ppl during thoracentesis. Future studies are needed to assess the usefulness of this device in selecting appropriate patients for pleurodesis and in preventing complications of thoracentesis, such as reexpansion pulmonary edema.

Author contributions: H. J. L. is the guarantor of the entire manuscript. H. J. L., D. K., J. A., C. G., and D. F.-K. contributed to the planning, data collection/analysis, and manuscript preparation; L. Y. contributed to the planning, data analysis, and manuscript preparation; R. E. T. contributed to the data analysis and manuscript preparation; R. O. and S. A. contributed to data collection and manuscript preparation; and A. H. contributed to planning, data collection, and manuscript preparation.

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

DM

digital manometer

ET

electronic transducer

Ppl

pleural pressure

UT

U-tube

Light RW. Pleural diseases. Dis Mon. 1992;38(5):266-331. [CrossRef] [PubMed]
 
Maskell N; British Thoracic Society Pleural Disease Guideline Group. British Thoracic Society pleural disease guidelines—2010 update. Thorax. 2010;65(8):667-669. [CrossRef] [PubMed]
 
Feller-Kopman D. Therapeutic thoracentesis: the role of ultrasound and pleural manometry. Curr Opin Pulm Med. 2007;13(4):312-318. [CrossRef] [PubMed]
 
Lan RS, Lo SK, Chuang ML, Yang CT, Tsao TC, Lee CH. Elastance of the pleural space: a predictor for the outcome of pleurodesis in patients with malignant pleural effusion. Ann Intern Med. 1997;126(10):768-774. [CrossRef] [PubMed]
 
Feller-Kopman D, Berkowitz D, Boiselle P, Ernst A. Large-volume thoracentesis and the risk of reexpansion pulmonary edema. Ann Thorac Surg. 2007;84(5):1656-1661. [CrossRef] [PubMed]
 
Feller-Kopman D, Parker MJ, Schwartzstein RM. Assessment of pleural pressure in the evaluation of pleural effusions. Chest. 2009;135(1):201-209. [CrossRef] [PubMed]
 
Pavlin J, Chenney F.W. Unilateral pulmonary edema in rabbits after reexpansion of collapsed lung. J Appl Physiol Respir Environ Exerc Physiol. 1979;46(1):31-35. [PubMed]
 
Maldonado F, Mullon JJ. Counterpoint: should pleural manometry be performed routinely during thoracentesis? No. Chest. 2012;141(4):846-848. [CrossRef] [PubMed]
 
Light RW, Jenkinson SG, Minh VD, George RB. Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis. Am Rev Respir Dis. 1980;121(5):799-804. [PubMed]
 
Doelken P, Huggins JT, Pastis NJ, Sahn SA. Pleural manometry: technique and clinical implications. Chest. 2004;126(6):1764-1769. [CrossRef] [PubMed]
 
Gordon CE, Feller-Kopman D, Balk EM, Smetana GW. Pneumothorax following thoracentesis: a systematic review and meta-analysis. Arch Intern Med. 2010;170(4):332-339. [CrossRef] [PubMed]
 
Havelock T, Teoh R, Laws D, Gleeson F; BTS Pleural Disease Guideline Group. Pleural procedures and thoracic ultrasound: British Thoracic Society pleural disease guideline 2010. Thorax. 2010;65(suppl 2):ii61-ii76. [CrossRef] [PubMed]
 
Sahu D, Bhaskaran M. Palpatory method of measuring diastolic blood pressure. J Anaesthesiol Clin Pharmacol. 2010;26(4):528-530. [PubMed]
 
Villena V, López-Encuentra A, Pozo F, De-Pablo A, Martín-Escribano P. Measurement of pleural pressure during therapeutic thoracentesis. Am J Respir Crit Care Med. 2000;162(4 pt 1):1534-1538. [CrossRef] [PubMed]
 
Feller-Kopman D, Walkey A, Berkowitz D, Ernst A. The relationship of pleural pressure to symptom development during therapeutic thoracentesis. Chest. 2006;129(6):1556-1560. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  Images of pleural manometry devices. A, Electronic transducer monitor. B, U-tube manometer (undamped). C, Compass digital manometer.Grahic Jump Location
Figure Jump LinkFigure 2 –  Estimated slopes for all three instruments.Grahic Jump Location

Tables

Table Graphic Jump Location
TABLE 1 ]  Demographics

CABG = coronary artery bypass graft; CHF = congestive heart failure.

Table Graphic Jump Location
TABLE 2 ]  Linear Regression Results

References

Light RW. Pleural diseases. Dis Mon. 1992;38(5):266-331. [CrossRef] [PubMed]
 
Maskell N; British Thoracic Society Pleural Disease Guideline Group. British Thoracic Society pleural disease guidelines—2010 update. Thorax. 2010;65(8):667-669. [CrossRef] [PubMed]
 
Feller-Kopman D. Therapeutic thoracentesis: the role of ultrasound and pleural manometry. Curr Opin Pulm Med. 2007;13(4):312-318. [CrossRef] [PubMed]
 
Lan RS, Lo SK, Chuang ML, Yang CT, Tsao TC, Lee CH. Elastance of the pleural space: a predictor for the outcome of pleurodesis in patients with malignant pleural effusion. Ann Intern Med. 1997;126(10):768-774. [CrossRef] [PubMed]
 
Feller-Kopman D, Berkowitz D, Boiselle P, Ernst A. Large-volume thoracentesis and the risk of reexpansion pulmonary edema. Ann Thorac Surg. 2007;84(5):1656-1661. [CrossRef] [PubMed]
 
Feller-Kopman D, Parker MJ, Schwartzstein RM. Assessment of pleural pressure in the evaluation of pleural effusions. Chest. 2009;135(1):201-209. [CrossRef] [PubMed]
 
Pavlin J, Chenney F.W. Unilateral pulmonary edema in rabbits after reexpansion of collapsed lung. J Appl Physiol Respir Environ Exerc Physiol. 1979;46(1):31-35. [PubMed]
 
Maldonado F, Mullon JJ. Counterpoint: should pleural manometry be performed routinely during thoracentesis? No. Chest. 2012;141(4):846-848. [CrossRef] [PubMed]
 
Light RW, Jenkinson SG, Minh VD, George RB. Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis. Am Rev Respir Dis. 1980;121(5):799-804. [PubMed]
 
Doelken P, Huggins JT, Pastis NJ, Sahn SA. Pleural manometry: technique and clinical implications. Chest. 2004;126(6):1764-1769. [CrossRef] [PubMed]
 
Gordon CE, Feller-Kopman D, Balk EM, Smetana GW. Pneumothorax following thoracentesis: a systematic review and meta-analysis. Arch Intern Med. 2010;170(4):332-339. [CrossRef] [PubMed]
 
Havelock T, Teoh R, Laws D, Gleeson F; BTS Pleural Disease Guideline Group. Pleural procedures and thoracic ultrasound: British Thoracic Society pleural disease guideline 2010. Thorax. 2010;65(suppl 2):ii61-ii76. [CrossRef] [PubMed]
 
Sahu D, Bhaskaran M. Palpatory method of measuring diastolic blood pressure. J Anaesthesiol Clin Pharmacol. 2010;26(4):528-530. [PubMed]
 
Villena V, López-Encuentra A, Pozo F, De-Pablo A, Martín-Escribano P. Measurement of pleural pressure during therapeutic thoracentesis. Am J Respir Crit Care Med. 2000;162(4 pt 1):1534-1538. [CrossRef] [PubMed]
 
Feller-Kopman D, Walkey A, Berkowitz D, Ernst A. The relationship of pleural pressure to symptom development during therapeutic thoracentesis. Chest. 2006;129(6):1556-1560. [CrossRef] [PubMed]
 
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