This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
Where the pleural effusion is serous it is usually drawn off by an aspirating needle or trocar.
For diagnostic purposes a hypodermic syringe needle is often used, as the chest-walls are usually thin enough to allow this to be done, particularly if a suitable spot is chosen and the patient is a child. Care should be exercised not to strike a rib. The spot chosen for puncture may be indicated by dulness on percussion. It may be anywhere, but when a choice is permissible the puncture should be made in the sixth interspace about in the middle or postaxillary line. Another preferred spot is in the eighth interspace, below the angle of the scapula. The sixth interspace may be determined in several ways, viz.:
1. Begin at the angulus sterni (angle of Ludwig) and follow out the second rib to the parasternal or midclavicular line, thence count down to the sixth rib and follow it to the midaxillary line.
2. The nipple is in the fourth interspace, follow it to the axillary line and count two spaces down.
4. Find the last rib that articulates with the sternum - it is the seventh; follow it around and take the space above.
5. With the arm to the side the inferior angle of the scapula marks the seventh interspace; take the interspace next above.
6. A horizontal line at the level of the nipple cuts the midaxillary line in about the sixth interspace.
7. The lower edge of the pectoralis major touches the side of the chest at the fifth rib. Follow it to the axillary line and go two spaces lower.
8. By raising the arm the serrations of the serratus anterior muscle attached to the fifth, sixth, seventh, and eighth ribs become visible; that attached to the sixth rib is the most prominent and is attached farthest forward.
When the pleural effusion is purulent, tapping is not sufficient, and drainage is resorted to. It is not considered necessary to open the pleural cavity at its lowest part but the sites chosen are usually the sixth or seventh interspace in the mid- or postaxillary line. The movements of the scapula are apt to interfere with drainage immediately below its angle, hence the opening is usually made farther forward. The surgeon may or may not resect a rib.
The ribs may lie so close together as to compress the drainage-tube; in such case a resection is done if the patient's condition permits.
In certain cases the condition of the patient may demand that as little as possible be done, and that quickly. The point of operation is selected by one of the guides already given, perhaps the level of the nipple.
While the finger of one hand marks the interspace, an incision 4 cm. (1 1/2 in.) long is made along the upper edge of the rib, this is deepened by a couple of strokes which detach the intercostal muscles and carefully penetrate the pleura. As the pus makes its appearance the knife is withdrawn and the finger is laid on the opening. A drainage-tube held in a curved forceps is then slid along the finger into the chest. Sometimes a rubber tracheotomy tube is used for drainage purposes. Any bleeding will be from the small intercostal branches and can readily be stopped by gauze packing.
The incision is made along the upper edge of the rib because the intercostal artery running along the lower edge of the rib is the larger.