Description of leak
Objectively measured data
Therapeutic consequence
Not tolerable
≥3000 ml/min
Immediately postop
“Normal”lung: sudden reexploration
Emphysematous lung: wait for 1–2 days
then revision if no trend towards healing
Very large
1500–3000 ml/min
Wait if trend towards healing is observed, otherwise quick revision
Large
500–1500 ml/min
>500 ml/min constantly over more than 7 days: revision
Small leak
50–500 ml/min
Correction of the tube
If necessary: Heimlich-Valve
No leak
≤40 ml/min constantly over 6 h
Pull the drain
The interpretation of data and the subsequent conclusions made must always be done in the context of the underlying disease, the condition of the lung (“normal”; emphysematous, fibrotic), surgery or intervention performed, and the duration of therapy so far. Remember that healing is a dynamic process!
Another advantage of electronic system, besides the generation of objective data, is the capability to recall previous data on the screens (Fig. 9.1) allowing for evaluation over time at a glance. This is compared to traditional systems where decisions are made “statically” during morning or evening rounds.
Figure 9.1
Display flow (grey: subatmospheric pressure, blue: flow, yellow: fluid production)
Figure 9.2
Display fluid
The interpretation of data acquired from an electronic drainage system should be placed in the context of the underlying disease, condition of the lung, procedure, and duration of therapy.
The author is well aware that this proposal of how to interpret objective data consists of haziness and conclusions drawn that are due to clinical experience and not based on evidence. At the end of the day every physician has to make decisions based on his/her own experience (see below).
9.4 Antiquated Procedures: Milking, Clamping, Cough Test
9.4.1 Milking or Stripping
This is a widely done procedure to prevent clogging of the intrathoracic tube which is not visible and thus cannot be observed. In times of modern electronic drainage systems that are able to show patency of the tube on the screen (one manufacturer), prophylactic milking and stripping is obsolete. Additionally there is no proven benefit with regard to patency rates. Several authors have shown this inefficacy [6, 17]. The latter conducted a Cochrane analysis including only studies from centers that perform cardiac surgery. In cardiac surgery the problem of tube clogging is much more evident as compared to thoracic surgery. In addition, unpredictable high pressure of up to −400 cm of water can be provoked during the milking process which could lead to parenchymal injury.
Prophylactic milking or stripping of chest drains is ineffective and can be dangerous, and thus it is obsolete.
9.4.2 Clamping
Clamping of the chest tube, up to 24 h, is also a widely used procedure, This is performed to increase the success of the chest drain therapy ending and therefore bringing the decision to pull the drain to a solid base.
This is dangerous! Clamping a chest drain is simulating a clinical setting with no tube. Doing so there is no chance to control and observe what is going on inside the chest cavity and the pleural space respectively. In particular, such a procedure can induce significant clinical problems especially if the patients are not monitored very closely. In addition clamping leads to a delay in removal.
With the help of electronic systems all relevant data needed for the decision process for pulling the tube is provided.
Clamping of the chest drain prior to removal is redundant and may be dangerous. In addition it leads to unneeded delay of the removal of the chest tube as well as to an increase in length of stay.
9.4.3 Cough Test
A cough test is performed to assess adequate that an adequate seal has formed in the lung parenchyma. The patient is asked, when using a classic drainage system with water seal, to cough firmly. If bubbles are observed in the collection chamber of the system this is taken as “confirmation” of an ongoing leak.
Again this procedure is as widely used and senseless! It is almost always possible to mobilize some bubble when coughing. These bubble are “responsible” for the chest tube not being pulled. Additionally in patients with severe emphysema this procedure may be problematic.
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