Revision of the anatomy and physiology of the respiratory system

The lungs are covered by the visceral pleura, the inner chest wall being lined by the parietal pleura. Between these pleura lies a thin layer of serous fluid the surface tension of which holds the two pleural linings together. As a result, the lung follows the movement of the chest wall, the lung volume being determined by the size of the thorax.

An increase in the amount of fluid in the space upsets this mechanism. Chest aspiration involves the introduction of a needle into the pleural cavity between the visceral and parietal pleura. It may be performed for the following reasons:

Using an aseptic technique, the medical practitioner washes and dries his or her hands, cleanses the patient’s skin over the selected site of entry of the aspiration needle, injects a local anaesthetic and waits for it to take effect. The aspiration needle is then inserted into the cavity between the visceral and parietal layers of the pleura. After withdrawing the stilette from the needle, specimens of fluid can be obtained from the cavity for laboratory investigation, and the remaining fluid can be allowed to drain out. Should there be a large amount of fluid to be aspirated, it may be necessary to interrupt the drainage process for 2–3 hours before recommencing. If the fluid is purulent, it may have to be aspirated by attaching a large syringe to the needle. A patient with a large pleural effusion may require the insertion of an indwelling catheter to facilitate ongoing drainage (Grodzin& Baik 1997).

At the end of the procedure, the aspirating needle is withdrawn, a sterile plastic spray is applied to the wound puncture, and an adhesive dressing is placed over it.