Postoperative thoracic surgery

Negative pressure may be applied to the chest drainage tube of the affected hemithorax in the following circumstances EXCEPT which one?

a) Post-pneumonectomy

b) Known bronchopleural fistula

c) Known haemothorax

d) Known empyema

e) Post-oesophagectomy

Answer: A

Explanation

Chest drainage tubes are sited intra-operatively or elsewhere to allowegress of fluid (such as air, blood, pus or effusion) from the intrapleural space. Often the pressure gradient between intrapleural space and atmospheric pressure are adequate to encourage outward flow. In cases where the gradient is insufficient, suctionmay be applied to the chest tube. Unlike ‘wall-suction’, chest tube suction is low-pressure (10 to 20cmH2O), high-flow suction. If a chest drain has been used for a pneumothorax and high-pressure, low-flow suction is applied (incorrectly), the rate of volume evacuation may not be sufficient thus allowing accumulation in the chest and potentially a tension pneumothorax.With bronchopleural fistula (BPF) there is no doubt that suction evacuation of the cavity may encourage further air leakage across the BPF causing increased volume of ‘wasted ventilation’. It is recommended that if it is necessary in cases of BPF, suction should be maintained at the minimumeffective level. The options quoted have caused controversy with respect to whether application of suction is appropriate. In cases of haemothorax, with potentially ongoing haemorrhage, might suction encourage bleeding? This is not thought to be the case. The role of chest tube suction with pleural infection is not agreed but it is not contraindicated. Following pneumonectomy the operative side fills withserous fluid. Although a chest tube is sited, it is usually left clamped and must not have negative pressure applied to it as doing this will evacuate the serous fluid, potentially disrupting the stump and shifting themediastinumenough to produce a similar effect to a tension pneumothorax. Post-oesophagectomy the use of facemask non-invasive ventilationis contraindicated as it could cause anastomotic strain/leak.