Suction versus no suction for chest drain management

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: In any age group or pathology requiring an intrathoracic chest drain does the addition of suction improve clinical outcomes? In draining the pleural space using underwater seal, one-way valve (or any other type of drain identified from the search) is the use of suction compared to without suction safer or more effective at evacuating either air, blood, fluid or pus? In draining the mediastinal space using underwater seal, one-way valve (or any other type of drain identified from the search) is the use of suction compared to without suction safer and more effective from evacuating air, blood and fluids? If suction is found to be beneficial when applied to chest drains (pleural and or mediastinal), what are the optimum pressures that should be used for adults, children and neonates?.