Pleural effusion is an extremely common problem with multiple causes; its subsequent investigation with thoracocentesis and treatment with drainage represent two of the most frequently performed diagnostic and therapeutic medical procedures. The role of thoracic ultrasonography in the management of pleural effusion is a modern and rapidly expanding one, having become effectively mandatory and part of the "gold standard" over the past decade due to its diagnostic and patient safety benefits. By contrast, the measurement of intra-pleural pressure using sequential manometry has failed to convincingly demonstrate its clinical value beyond physiological studies despite its availability for over a century. Previous work has shown a potential role for pleural manometry in predicting the presence of un-expandable lung and success of talc pleurodesis but these studies have not been replicated or clinically validated.