Most chest drains need no suction yet more confusion is caused by suction for chest drains than most issues in thoracic surgery.

A patient who is free from pain, to the degree that an effective cough can be produced, will generate a much higher pressure than can safely be produced with suction.

Suction should be seen as the exception rather than the rule.

Reasons for using suction.

1. •If a patient cannot re-inflate his own lung, due to pain, debilitation, laryngeal nerve palsy etc.
   

2. •Immediate postoperative period - usually the patient is somewhat drowsy, uncooperative and full pain control has not been established. Therefore the cough is usually ineffectual. I usually start suction for the first 12-24 hours after which it can be stopped.
   

3. •Patients on mechanical ventilators cannot produce an effective cough (sedation, lack of an effective glottis when intubated) and therefore suction is advised.
   

4. •Excessive air leak - ideally excessive air leak should be controlled surgically before a thoracotomy is closed. However, where there is an excessive air leak, suction can maintain lung expansion.
   

5. •Major surgical emphysema indicates a major air leak with the air preferentially tracking into the tissues on coughing. Suction can control this situation.
   

6. •Badly positioned drain - again the treatment is to insert a well positioned drain. However, sometimes the situation arises where a drain is fairly well positioned and a few days suction may be seen as better than the discomfort and potential contamination of a further drain.
   

Suction should not be used as an alternative to good surgical technique which includes release of diaphragmatic adhesions, surgical control of major air leaks and accurate placement of chest drains.

Thoracic suction - high volume, low pressure

When thoracic suction is needed, it has to handle large volumes of air. However, if it is at high pressure, it can suck lung or other tissue into the tubing, blocking it. Air may leak elsewhere even causing tension.

Therefore thoracic suction is high volume (litres per minute) at low pressure (in the range of 15 - 25 cm of water).

Historically this was achieved by using a series of rotating pumps called “Roberts”. More recently high volume The Ohmeda wall suction units (Ohmeda Thoracic suction kit and wall mount - reference code: 1520151) are generally the most reliable

One of the main differences in the available drainage systems is the method used to manage suction:

1. •must have no obstruction throughout whole system i.e. the tubing, the valve, the air outlet on the bottle, the suction unit itself.
   

2. •Thoracic suction should only be used on wards where the staff are familiar with chest drain suction.
   

3. •A drain is safer with no suction than suction which is not working correctly.
   

4. •Close surveillance is therefore required by nursing staff trained to recognise faults in the drainage and suction system. It is better to remove suction than to use a faulty device.
   

General surgical suction

Standard surgical suction is used for:

1. •Aspirating an airway
   

2. •Intra-operative suction
   

3. •Aspirating a sump nasogastric tube - Thoracic suction is inappropriate for nasogastric tubes. High pressure suction general surgical suction should be used and an underwater seal is not required. It is working adequately if there is a continuous flow of air or fluid through the air inlet and back through the drain. If there is gastric fluid leaking out the air inlet tubing, the suction is not set high enough. There should be no need to elevate or spiggot the air inlet tubing. (High grade suction on a non-sump nasogastric will suck the mucosa into the holes, blocking them. The sump tubes have a double lumen to prevent this happenning.