Reducing morbidity from chest drains

Knowledge of basic principles and use of appropriate equipment would help

The insertion of an intercostal chest drain to relieve the pleural cavity of unwanted air or liquid is a common procedure. It is simple to perform and should be associated with a low mortality and morbidity. However, unnecessary problems are often encountered, both during and after the procedure.

Most hospital doctors will, at some stage, insert a chest drain, either urgently in cases of trauma or electively for a pneumothorax or pleural effusion. An adequate understanding of the anatomy and pathophysiology of the pleural space is vital, as is proper teaching of the technique of insertion and subsequent management of chest drains.1 2 3

The aim of drain insertion is to restore and maintain the negative intrathoracic pressure necessary for lung expansion and drainage of the pleural cavity.4 The physiological mechanisms maintaining full expansion depend on removal of excess liquid and gas from this space. The basic principle of chest drainage is to ensure this by re-establishing the negative intrapleural pressure. When at rest (that is, at functional residual capacity), the elastic forces of the chest wall and lung try to separate the visceral and parietal pleural layers, and create a negative intrapleural pressure of -2 to -5 cm of water. During inspiration, the negative intrapleural pressure increases to about -35 cm of water. Full expansion of the lung will also allow reactivation of the surface forces that hold the visceral and parietal pleuras together.

Pneumothoraces are caused by a breach in the continuity of the pleural sac (either via the lung or chest wall), allowing positive pressure air into the cavity from the alveoli or the atmosphere. The negative intrapleural pressure is lost, causing the lung to collapse and fall away from the chest wall. A one way airflow mechanism, usually via an underwater seal drainage system, is necessary for managing a chest drain.

The addition of suction (10-20 cm of water) to this system increases the negative intrapleural pressure. If suction is to be used it must be at high volume and low pressure. A low volume pump (such as a Roberts) should not be used as it will not be able to handle a large air leak and will allow air to accumulate, worsening the pneumothorax.5 Suction should be instituted according to individual need, but, on the whole, the more the patient can comfortably tolerate, the sooner re-expansion will occur.

There is no virtue in siting a “low” drain, even for liquid. A drain of appropriate size in any position in the pleural cavity will restore negative pressure and re-expansion of the lung, expelling excess pleural contents. Accurate placement of the tip of the drain, once inserted, will expedite the process but is not essential. Insertion in the fifth intercostal space in the anterior axillary line is safe and should avoid the risk of abdominal penetration. As for size, a 28 French gauge or larger drain should be used for blood to minimise blockage. However, a 24 French gauge is adequate for air or low viscosity effusions.

A major subject of concern is the standard of equipment with which medical staff are expected to insert a drain safely and efficiently. What is provided, even in cardiothoracic wards or accident and emergency departments, is almost universally inadequate. This is a correctable contributor to the morbidity associated with chest drainage. Few items are needed to establish safe, efficient chest drainage, but they are seldom provided. Usually, a “trolley” is set up containing some local anaesthetic, skin antiseptic, and drapes, a small dressings set containing plastic forceps, a scalpel, a chest drain with trocar, a 2/0 (or smaller) suture, and the underwater drainage system. These items alone do not allow safe access to the pleural cavity and will cause undue discomfort for the patient. The trocar is often wrongly used to gain access to the pleural cavity, making this a dangerous procedure.6

These problems can be avoided by providing appropriate equipment. We recommend that a trocar should never be used and that access to the pleural cavity must be attained by blunt dissection. To achieve this, metal instruments are needed (such as a pair of artery forceps), with which the incision through the intercostal muscles can be widened to allow passage of a finger. The finger should then be used to establish access to the pleural cavity. The artery forceps should be applied to the inside tip of the chest drain in parallel, thus creating a firm, blunt tip. This rigid arrangement can safely be passed into the pleural cavity via the previous breach in the parietal pleura and directed either apically for air or basally for liquid. It should then be connected to the underwater drainage system. To secure the drain, a suture of number 1 or greater (silk or nylon) should be used to allow firm tying and avoid breakage. The tube should then be taped to the side of the patient, avoiding the large quantities of strapping often seen.

Perhaps the most commonly encountered error in chest drain management is clamping of the tube. There is no definite indication for clamping a chest drain, and it may be highly dangerous, potentially converting simple pneumothoraces to life threatening tension pneumothoraces.7 Unfortunately, drains continue to be clamped, even on “specialist” units. This usually occurs during transfer to the radiology department or between units by nursing staff. It must be discouraged.

As a result of our observations, we have designed a prepacked chest drain set for our hospital containing the basic items needed for the safe insertion of chest drains (see box). We advocate the application of the principles of advanced training in life support1 and encourage inexperienced practitioners to seek help early. Standardised methods of inserting and managing chest drains would be of benefit to both patients and medical staff.