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Pleural Manometry

Ready for Prime Time

Folch, Erik MD, MSc; Mahajan, Amit MD; Majid, Adnan MD, FCCP

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Journal of Bronchology & Interventional Pulmonology: October 2013 - Volume 20 - Issue 4 - p 297-298
doi: 10.1097/LBR.0000000000000019
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Pleural manometry is not a novel technique. In fact, the use of water manometers to measure pleural pressure changes as fluid is drained out during thoracentesis has been described for decades. The elastance curves derived from the measurements of pleural manometry enable physicians to distinguish “trapped lung physiology” from normal lung reexpansion.1 Unfortunately, the application of this valuable diagnostic technique has failed to be integrated into everyday practice. The cause of this delay is multifactorial but is primarily related to the lack of training in pleural disease in most fellowship programs, the difficulty in accurately recording pleural pressure, and the lack of a simple technique of measurement during pressure swings resulting from inspiration and exhalation. Fortunately, this gap in knowledge appears to be closing. Objectively, the number of papers in Medline under the search term “pleural pressure” and “pleural manometry” has significantly increased over the past decade. Also at an all-time high is the number of abstracts presented at international conferences. These findings represent translation of physiologic research to bedside practice.

So, what are the reasons for measuring pleural pressure and why should we be interested?

Pleural pressure measurement can identify patients who are likely to benefit from pleurodesis. Recognition of this patient population is essential, as pleurodesis requires apposition of the visceral and parietal pleura for symphysis to occur.2 A low elastance (<14.5 cm H2O) measured by pleural manometry allows us to identify patients who are likely to gain full lung reexpansion following thoracentesis. Similarly, other studies have proven that patients with high elastance and trapped-lung physiology derive a clinical benefit when treated with tunneled pleural catheter drainage.3 Numerous studies have also described the use of pleural manometry to minimize pressure-related complications of pleural fluid removal, such as reexpansion pulmonary edema.4 Finally, safe removal of large amounts of pleural fluid (>1.5 L) may improve symptoms, decrease the interval for repeated procedures, and allow visualization of the underlying lung parenchyma, which in itself is an excellent reason to perform pleural manometry.1,5

Riding on this wave of increased interest in measuring pleural pressure, the paper of Boshuizen et al6 has been published with opportune timing. They describe serial measurement of pleural pressure in 30 patients after sequential removal of 200 mL of pleural fluid while measuring pleural pressure with an electronic pressure transducer and customized software to record pressure signals with a temporal resolution of <100 ms. They measured pleural pressure 40 times per second for 13 seconds. The result is a real-time curve of pressure swings that can be studied in inspiration and expiration. These precise measurements can also be used to calculate elastance by dividing the pressure by the volume removed. The authors were able to better calculate the mean pleural pressure using high-frequency recordings and minimize the distortion created by the respiratory variation in pleural pressure. Finally, they were also able to control the background negative pressure at a constant rate of 40 cm H2O. This step prevented sudden pressure shifts as those seen with the use of manual syringe pumping that can be around −350 cm H2O or those from vacuum bottles that exceed −500 cm H2O.

Interestingly, this study also suggests that relying only on patient-reported chest pain would merely complement the use of pleural manometry, whether intermittent or through high-temporal resolution methods. These findings have been supported by other reports describing patients who remain asymptomatic despite dangerously low pleural pressure levels during thoracentesis. Such findings reinforce the idea that neither the operator nor the patient is aware of the development of dangerously low negative pressure levels during thoracentesis.5,7 Some studies identify patients with significantly negative (very low) pleural pressure and no symptoms, whereas others identify symptoms that herald a complication, such as pneumothorax or an unexpandable lung. It seems as though we were measuring 2 different aspects of the same phenomenon. Both, extremely low pleural pressure and symptoms such as chest tightness, are phenomena indicating an ongoing harmful pleural environment in which continued suction and fluid removal could result in pneumothorax or reexpansion pulmonary edema. We see this as a discussion of “precision versus accuracy.” Precision reflects the exactitude with which one can express something, whereas accuracy is a measure of whether a conclusion is consistent with the truth. Both symptoms and intermittent pleural manometry are accurate measures of an abnormal pleural elastance. However, manometry likely identifies the phenomenon earlier and in an objective manner, thus adding precision. Through their study, Boshuizen et al6 have contributed to the precision of pleural manometry.

In conclusion, we believe pleural manometry is a necessary tool that must be utilized in the treatment of pleural diseases. Pleural manometry is safe, inexpensive, and reproducible. Furthermore, it is readily available and provides clinicians with valuable information that can positively affect patient care with no additional risks. The ongoing debate on using pleural manometry on every thoracentesis or only on selected ones is complicated by a type of selection bias.8,9 How do we predict those patients for whom pleural manometry is beneficial? Actually, we argue that pleural manometry is most useful in those patients at risk for a trapped lung based on initial radiographic imaging and the presence of recurrent and moderate-to-large effusions, as it would help us guide therapy and prevent potential complications. We hope that the growth in interest revolving around pleural manometry will continue to increase both in accuracy and precision, thus providing insight into the pathophysiology of pleural effusions and aiding in patient care.

Erik Folch, MD, MSc

Amit Mahajan, MD

Adnan Majid, MD, FCCP

Division of Thoracic Surgery and Interventional Pulmonology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston MA

REFERENCES

1. Light RW, Jenkinson SG, Minh VD, et al..Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis.Am Rev Respir Dis.1980;121:799–804.
2. Lan RS, Lo SK, Chuang ML, et al..Elastance of the pleural space: a predictor for the outcome of pleurodesis in patients with malignant pleural effusion.Ann Intern Med.1997;126:768–774.
3. Pien GW, Gant MJ, Washam CL, et al..Use of an implantable pleural catheter for trapped lung syndrome in patients with malignant pleural effusion.Chest.2001;119:1641–1646.
4. Feller-Kopman D, Berkowitz D, Boiselle P, et al..Large-volume thoracentesis and the risk of reexpansion pulmonary edema.Ann Thorac Surg.2007;84:1656–1661.
5. Villena V, Lopez-Encuentra A, Pozo F, et al..Measurement of pleural pressure during therapeutic thoracentesis.Am J Respir Crit Care Med.2000;162:1534–1538.
6. Boshuizen RC, Sinaasappel M, Vincent AD, et al..Pleural pressure swing and lung expansion after malignant pleural effusion drainage: the benefits of high-temporal resolution pleural manometry.J Bronchol Interv Pulmonol.2013;20:200–205.
7. Doelken P, Huggins JT, Pastis NJ, et al..Pleural manometry: technique and clinical implications.Chest.2004;126:1764–1769.
8. Feller-Kopman D.Point: should pleural manometry be performed routinely during thoracentesis? Yes.Chest.2012;141:844–845.
9. Maldonado F, Mullon JJ.Counterpoint: should pleural manometry be performed routinely during thoracentesis? No.Chest.2012;141:846–848discussion 8-9.
© 2013 by Lippincott Williams & Wilkins.