"On paracentesis of the thorax"

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PDF from photocopy; Taubman Medical Library, University of Michigan.

By John Snow, M.R.C.S.

(For the London Medical Gazette.)

Read at the Westminster Medical Society on December 18, 1841.

In the normal condition there is no vacant space within the thorax. The pleura on each side of the chest is an empty bag, merely lubricated on its inner surface with serum; and the pulmonary and costal portions glide gently over each other during respiration. Whenever any fluid, whether a liquid or a gas, accumulates within the pleura, it is desirable that we should get rid of it. Tapping the thorax, however, is the means adopted only in those cases in which the fluid is known or presumed to be pus, or where there is serum or air in one pleural sac in such quantity that one lung is rendered useless, and the mediastinum is pushed aside, and the function of the opposite lung so interrupted, that life is endangered. Under other circumstances than these, the ordinary modes of performing paracentesis of the chest, whether by the trocar or the bistoury, would not diminish the existing evils.

The tissue of the lungs possesses an elasticity which would enable these organs to expel the greater part of the [705/706] air they contain, provided the atmospheric pressure were exactly equal on their internal and external surfaces; but so long as the thorax remains intact the atmosphere can only press on the exterior of the lungs through the walls and floor of the chest, and the muscles of respiration being more powerful than the elasticity of the lungs, the atmospheric pressure on the interior of the latter compels them to be obedient to every motion of the chest. But so soon as an artificial opening is made into the pleura, the atmospheric pressure is at once equal on the inner and outer surfaces of the lung on that side; it collapses in accordance with its own elasticity, and remains unaffected by the motions of the ribs and diaphragm; and whether the air press immediately on the surface of the lung, or through the medium of a liquid effusion, the effect will be the same. It follows from this, that at the conclusion of paracentesis, performed in the ordinary way, the lung must be collapsed, and the space between it and the ribs occupied by air, provided all the liquid has been removed. And, in fact, with the stethoscope applied to the chest during the operation, the air can be heard passing in by bubbles as the liquid flows out.

The introduction of air into the pleura will most likely be injurious whenever that membrane is in a state of inflammation; but the greatest evils arising from the admission of air, are occasioned by its mechanical resistance to the expansion of the lung, which can only be brought into perfect use in proportion as the air contained in its pleura is absorbed; and the complete absorption of it must occupy several days. During this time, not only does the patient suffer from limited respiration, but time is allowed for the lung to become bound down by the consolidation of the coagulable lymph, which may be effused, and thus permanently detained within its shrivelled dimensions. The removal of serum whilst in moderate quantity, and recently effused from pleurisy, would prevent the diminished lung and contracted chest which often follows that complaint, provided the serum could be removed without being replaced by air, otherwise the operation would obviously not be of much avail. When from pneumothorax or effusion of serum, the lung is pressed close to the spine, the mediastinum pushed to one side, and the ribs and intercostal spaces distended, the common operation of paracentesis gives great relief, because it allows the thorax to return to a state of equilibrium, and relieves the other lung; the patient being brought to the condition a healthy person would be in after having an opening made into the pleura and then closed again, the air being allowed to remain. But even in these cases, or where purulent matter is effused, it would be a great advantage to leave the patient with the pleura empty, and the lung expanded and filling the chest.

To make an opening into each pleura, and allow both lungs to collapse, would be to cause instant death by asphyxia; accordingly, the two sides of the chest cannot be tapped by the ordinary method on the same day. And when dyspnœa exists from liquid in both pleuræ, the patient cannot dispense with one of his embarrassed lungs; he evidently could not live with half the respiration he has got; accordingly paracentesis is not performed in hydrothorax, a disease which nearly always occupies both sides of the chest. Idiopathic hydrothorax is believed to be very rare, if it exist at all. If there be such a complaint, it will probably, like hydrocele, be generally single, and occupy but one side. Hydrothorax, however, arising from some other affection, such as obstructed circulation through the lungs or heart, or disease of the kidneys, is a frequent complaint, and one which, if not relieved by medicine, soon proves fatal. It is sometimes but a symptom of the approaching dissolution which would take place independently of the dropsical effusion; but at other times it cuts off the patient much sooner than would the original affection of the heart or other organ. The dropsy arising from granular degeneration of the kidneys may occur in any stage of the disease; it generally involves nearly all parts of the body, but it may predominate in one situation, as in the cellular tissue, in the abdomen, or the thorax; and when in the latter situation may soon be fatal; and this may occur either in an advanced stage of the disease, or when there is merely a state of inflammation or congestion of the kidneys, which might lead to granular disease if not removed by [706/707] remedies. In a case of renal dropsy followed by scarlet fever, which occurred to me two years ago, the child was cut off by hydrothorax, although it was not worse in other respects than some who recovered.

Now, provided the serum can be removed without making a communication between the external air and the pleura, I do not see why tapping may not be performed on the thorax with the same safety and success as on the abdomen. I find from a recent number of the "London and Edinburgh Monthly Journal," that Dr. Davidson, of Glasgow, has been applying cupping-glasses over the canula introduced for empyema, in order to withdraw the fluid and prevent the ingress of air. This is certainly an improvement, but still leaves the operation far from a state of perfection; for, not to mention other objections, it is obvious that on the removal of the cupping-glass, air must rush into the chest before the canula can be withdrawn, or other means taken to stop the opening; and many cubic inches of air will rush through a very small orifice in half a second. Accordingly, in a case Dr. Davidson relates, the splashing of fluid was heard on performing the Hyppocratic test of succussion, three days after the operation, and we know this splashing can only take place when there is both air and liquid in the thorax.

The chief object of this paper is to lay before the Society the drawing of an instrument, which any member can get made by his own instrument maker.* By its means any fluid can be withdrawn from the chest, without making a direct communication between that cavity and the external air. It consists of trocar and canula with a stop-cock in it, the trocar to pass through the open valve of the stop-cock. A portion of the trocar must be made perfectly cylindrical, and to fit accurately the whole length of the canula. In withdrawing the trocar from the canula after their joint introduction, it must be brought so far as to be clear of the stop-cock, which point is indicated by a mark on the trocar, and then the stop-cock must be turned before the complete removal of the trocar. The portion of elastic tube must now be screwed to the canula; and to this tube must be screwed a double action syringe, with two distinct valves, like a stomach-pump. The valve of the stop-cock can now be reopened, and by working the pump, the contents of the pleura, whether gaseous or liquid, will be withdrawn. It is evident that not a particle of air can enter the pleura, and that the integrity of the chest as a pneumatic apparatus is not impaired during the operation. Before introducing the trocar, the skin must be drawn a little from its situation, and then by withdrawing the canula slowly at the end of the operation, the correspondence between the superficial and deeper wounds will be lost before air can enter the pleura.

If the lung be already firmly bound down before resorting to the operation, in a case of effusion, it will not be practicable to draw off the whole of the liquid. In such a case the resistance to using the pump, and the sense of uneasiness in the patient, will indicate when to stop, as in using the enema pump; and if the liquid be serum, it will be preferable to leave a little in the thorax; if, however, it be pus, the pump can be removed, and air admitted to allow of its complete removal.

This instrument must possess great advantages in the cases in which paracentesis is at present performed, and it will extend the occasions on which the operation may be resorted to with safety and advantage.

54 Frith Street, Soho Square.

*It has since been manufactured, under my directions, with great accuracy, by Mr. Read, of Regent Circus.

[A drawing of the instrument was forwarded to us with the paper, but the description is so distinct, that we have not thought it necessary to have an engraving made. - ED. Gaz.]