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Counterpoint: Should Pleural Manometry Be Performed Routinely During Thoracentesis? No

2012; Elsevier BV; Volume: 141; Issue: 4 Linguagem: Inglês

10.1378/chest.11-3233

1931-3543

Fabien Maldonado, John J. Mullon,

Lung Cancer Diagnosis and Treatment

The recent explosion of diagnostic and therapeutic techniques available to pulmonologists is credited for the development of the subspecialization of interventional pulmonary medicine. It has also led many to revisit the way common pulmonary procedures, such as thoracentesis, have been performed historically. Although the benefit of using thoracic ultrasonography in improving the safety of thoracentesis have become evident only recently, pleural manometry was described more than a century ago.1Feller-Kopman D Therapeutic thoracentesis: the role of ultrasound and pleural manometry.Curr Opin Pulm Med. 2007; 13: 312-318Crossref PubMed Scopus (58) Google Scholar Out of favor for decades, it has in the past few years been the object of many publications highlighting its potential role in the diagnosis of unexpandable lung, as a safeguard against reexpansion pulmonary edema (REPE), and, perhaps, as a predictor of successful pleurodesis. The various techniques used to measure pleural pressures during thoracentesis have been described in detail elsewhere.2Doelken P Huggins JT Pastis NJ Sahn SA Pleural manometry: technique and clinical implications.Chest. 2004; 126: 1764-1769Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar They are relatively simple and could be available to most pulmonologists. That only a minority of pulmonologists has adopted manometry, in contrast to ultrasound guidance, begs the question of whether it should be done routinely as suggested by some. We do use manometry during thoracentesis, although not routinely, and do acknowledge its valuable contribution to a better understanding of the pathophysiology of pleural effusions. However, suggesting that manometry should be performed routinely implies that patient outcomes will be positively affected and will outweigh the downsides of the procedure. We review the limitations of the available evidence supporting its use and the pitfalls that may hamper its widespread use. This statement is arguably the least controversial regarding manometry. The concept seems straightforward: At the resting condition (ie, at functional residual capacity), the pleural pressure is slightly subatmospheric, a function of the lung elastic recoil and the tendency of the chest wall to expand outward. Disruptions in capillary homeostasis, as described by Starling, result in an accumulation of pleural fluid and an increase in pleural pressure.3Light RW Jenkinson SG Minh VD George RB Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis.Am Rev Respir Dis. 1980; 121: 799-804PubMed Google Scholar Conversely, thoracentesis should lead to a measurable gradual decrease in pleural pressure back to a more physiologic level if the entirety of the fluid is drained. In some situations (thick visceral pleural peel, endobronchial obstruction, or decreased lung compliance), the lung may reexpand only partially or not at all and may result in different elastance curves, as described in Figure 1. It is hypothesized that continued drainage when the lung cannot reexpand further will drive an increase in transpulmonary pressures that could result in complications such as chest pain, pneumothorax ex vacuo, or, rarely, REPE (see the "Pleural Manometry Helps Prevent REPE" section).4Feller-Kopman D Berkowitz D Boiselle P Ernst A Large-volume thoracentesis and the risk of reexpansion pulmonary edema.Ann Thorac Surg. 2007; 84: 1656-1661Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar, 5Feller-Kopman D Walkey A Berkowitz D Ernst A The relationship of pleural pressure to symptom development during therapeutic thoracentesis.Chest. 2006; 129: 1556-1560Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar, 6Heidecker J Huggins JT Sahn SA Doelken P Pathophysiology of pneumothorax following ultrasound-guided thoracentesis.Chest. 2006; 130: 1173-1184Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar, 7Huggins JT Sahn SA Heidecker J Ravenel JG Doelken P Characteristics of trapped lung: pleural fluid analysis, manometry, and air-contrast chest CT.Chest. 2007; 131: 206-213Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, 8Villena 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: 1534-1538Crossref PubMed Scopus (73) Google Scholar Hence, monitoring pleural pressures during thoracentesis should be the gold standard a priori for the diagnosis of unexpandable lung. Several caveats regarding this assertion, however, should temper our enthusiasm. First and foremost, it should be obvious to most that perhaps the best way to diagnose unexpandable lung is to show that the lung has not entirely reexpanded after maximal fluid removal. Routine chest radiographs after thoracentesis are not warranted,9Petersen WG Zimmerman R Limited utility of chest radiograph after thoracentesis.Chest. 2000; 117: 1038-1042Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar but we typically perform an ultrasound at the end of each procedure to assess for the presence of remaining fluid, as well as to rule out postthoracentesis pneumothorax. Second, chest discomfort may be a more reliable indicator of unexpandable lung. One study suggests a positive correlation between the development of chest discomfort and lower closing pleural pressures, supporting this assertion.5Feller-Kopman D Walkey A Berkowitz D Ernst A The relationship of pleural pressure to symptom development during therapeutic thoracentesis.Chest. 2006; 129: 1556-1560Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar That the correlation is not perfect does not necessarily argue for manometry as a better indicator for discontinuation of the procedure over the patient's symptoms. As is the case for opening pleural pressures,3Light RW Jenkinson SG Minh VD George RB Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis.Am Rev Respir Dis. 1980; 121: 799-804PubMed Google Scholar "dangerously low" pleural pressures may also vary across individuals,3Light RW Jenkinson SG Minh VD George RB Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis.Am Rev Respir Dis. 1980; 121: 799-804PubMed Google Scholar and, as well described in the case of ventilator-induced lung injury, heterogeneous lung disease may result in a spectrum of pulmonary strain for a given change in overall pleural pressure, potentially exposing less compliant areas to unpredictable regional complications. The observation that pleural manometry does not seem to help prevent pneumothorax ex vacuo would support this hypothesis.4Feller-Kopman D Berkowitz D Boiselle P Ernst A Large-volume thoracentesis and the risk of reexpansion pulmonary edema.Ann Thorac Surg. 2007; 84: 1656-1661Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar, 6Heidecker J Huggins JT Sahn SA Doelken P Pathophysiology of pneumothorax following ultrasound-guided thoracentesis.Chest. 2006; 130: 1173-1184Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar Finally, we would like to emphasize that reliance on arbitrarily defined cutoffs for pleural pressure or elastance cannot be recommended. First, there is no validated method of defining normal pleural elastance at the individual level.6Heidecker J Huggins JT Sahn SA Doelken P Pathophysiology of pneumothorax following ultrasound-guided thoracentesis.Chest. 2006; 130: 1173-1184Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar, 7Huggins JT Sahn SA Heidecker J Ravenel JG Doelken P Characteristics of trapped lung: pleural fluid analysis, manometry, and air-contrast chest CT.Chest. 2007; 131: 206-213Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar Second, the relationship of pleural pressure to removed volume may change during the procedure (ie, estimates of overall pleural elastance may be misleading) (Fig 2). Perhaps plotting the elastance curve and looking for an "inflection point" beyond which the lung cannot continue to expand would be a more valid approach. Whether doing so would eventually result in meaningful improvement in patient management and outcome remains to be proven. No single discreet measure, whether it be elastance, inflection point, or absolute pressure, has been validated adequately as a clinically accurate and reproducible threshold beyond which fluid removal should not continue. Experts suggest that fluid removal should not exceed 1 L to avoid REPE, unless pleural pressure is monitored, in which case fluid can be removed until end-expiratory pleural pressures drop below −20 cm H2O or chest discomfort develops. The pathophysiology of REPE is still to be elucidated. However, animal models suggest that the development of REPE correlates with the duration of lung collapse and excessively negative pleural pressures,10Miller WC Toon R Palat H Lacroix J Experimental pulmonary edema following re-expansion of pneumothorax.Am Rev Respir Dis. 1973; 108: 654-656PubMed Google Scholar, 11Pavlin J Cheney Jr, FW Unilateral pulmonary edema in rabbits after reexpansion of collapsed lung.J Appl Physiol. 1979; 46: 31-35Crossref PubMed Scopus (73) Google Scholar which would suggest that the REPE may also be regarded as another "stretch injury" that could potentially be avoided by monitoring pleural pressures during thoracentesis. It should be emphasized that the −20 cm H2O cutoff was chosen arbitrarily, based on two animal studies using a pneumothorax model, which showed a risk of REPE at pressure levels below −40 mm Hg (equivalent to −54 cm H2O).3Light RW Jenkinson SG Minh VD George RB Observations on pleural fluid pressures as fluid is withdrawn during thoracentesis.Am Rev Respir Dis. 1980; 121: 799-804PubMed Google Scholar, 10Miller WC Toon R Palat H Lacroix J Experimental pulmonary edema following re-expansion of pneumothorax.Am Rev Respir Dis. 1973; 108: 654-656PubMed Google Scholar, 11Pavlin J Cheney Jr, FW Unilateral pulmonary edema in rabbits after reexpansion of collapsed lung.J Appl Physiol. 1979; 46: 31-35Crossref PubMed Scopus (73) Google Scholar Beyond the obvious shortcoming of extrapolating these limited data to clinical practice, it should be noted that the largest study on large-volume thoracentesis did not find any correlation between incidence of REPE and measures of pleural pressure or elastance. Although this association may have been obscured by the limited power of the study (only five of 185 patients developed REPE), we would tend to concur with the invited commentator that neither a 1-L nor a −20-cm H2O cutoff appears to be supported by strong evidence.4Feller-Kopman D Berkowitz D Boiselle P Ernst A Large-volume thoracentesis and the risk of reexpansion pulmonary edema.Ann Thorac Surg. 2007; 84: 1656-1661Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar It is self-evident that for pleurodesis to be successful, there should be adequate apposition of parietal and visceral pleura after lung reexpansion. It should also make sense intuitively that high pleural elastance may interfere with pleurodesis because higher elastance represents a higher likelihood of the two pleural layers being pulled apart. This was elegantly demonstrated by Lan et al,12Lan 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: 768-774Crossref PubMed Scopus (117) Google Scholar who showed that a decrease in pleural pressure in excess of 19 cm H2O after removal of the initial 500 mL was a predictor of unsuccessful pleurodesis. However, in addition to the limitations of elastance calculations mentioned above, it is difficult to believe that an excessively negative pressure, regardless of the calculated elastance, would be compatible with successful pleurodesis. As such, absolute closing pressure may be a more relevant variable to consider. Certainly, a "biphasic" elastance curve (curve 2 on Fig 1) would suggest that an indwelling pleural catheter may be an appropriate palliative intervention in symptomatic patients.1Feller-Kopman D Therapeutic thoracentesis: the role of ultrasound and pleural manometry.Curr Opin Pulm Med. 2007; 13: 312-318Crossref PubMed Scopus (58) Google Scholar One may argue that a similar conclusion could be drawn from patients with incomplete lung reexpansion who have shown symptomatic improvement from therapeutic thoracentesis and in whom fluid reaccumulation is noted. Lessons learned from the ongoing controversy surrounding the use of Swan-Ganz catheters in critically ill patients remind us that diagnostic tools can help only if the information provided is accurate and correctly interpreted and leads to appropriate interventions resulting in improved patient outcomes. Pleural manometry takes time, requires additional training, and may lead to inappropriate decisions. Given the present state of knowledge, it would be difficult to justify withholding chemical pleurodesis or additional fluid removal in an asymptomatic patient based solely on manometry data. Pleural manometry is an interesting research tool that offers some insights into the pathophysiology of pleural effusions and may help guide management in selected situations, but available data do not support its routine use during thoracentesis.