Before considering the significance of the pleural pressures, one must understand how the measurements are made and how pleural pressures arise; lack of knowledge of the physiology of the pleural space can lead to misinterpretation of the values obtained. Pleural pressure can be measured with several techniques, including a U-shaped water manometer,9 an overdamped water manometer,10 or sophisticated electronic transducer systems that allow sampling frequencies of several hertz and provide the ability to store data for further analysis. A benefit of the U-shaped manometer is that it is relatively inexpensive. A disadvantage, however, is that it may be difficult to accurately record values because of the pleural pressure swings associated with inspiration and expiration. Doelken et al10 described their use of an overdamped water manometer, which uses a 22-gauge needle as a resistor, and showed excellent correlation to the electronic system (r = 0.97). The benefits of this system are that it is relatively easy to set up and provides real-time mean pleural pressure without the large respiratory-related swings encountered by systems that are not damped. Electronic transducer systems can be configured for standard ICU monitors. Because these monitors are not calibrated to measure negative pressure, one must calibrate an offset, or an adjustment in the actual height of the transducer relative to the zero reference level such that negative numbers can be recorded. Additionally, ICU hemodynamic transducers report data in millimeters of mercury, as compared to the standard centimeters of water typically used for pleural pressure measurements. This problem is resolved easily by using the conversion factor of 1 mm Hg = 1.36 cm H2O. A clear advantage of using an electronic transducer system is that it provides the capability to review the pleural pressure curves after the data have been collected, thereby enabling the analysis of pressure anywhere in the respiratory cycle (ie, at end inspiration and end expiration) as well as the opportunity to calculate mean pleural pressure. We typically report mean or end-expiratory (ie, at FRC) pleural pressure. It may be, however, that end-inspiratory pressure is most relevant as a possible risk factor for the development of pressure-related complications, such as reexpansion pulmonary edema. At this time, it is impossible to recommend one method of measuring pleural pressure over another, but we strongly suggest becoming familiar with a system that can be used easily and replicated on each patient at one's local institution.