Drainage is introduced into the pleural cavity to aspirate air or fluid. Since the pressure in the pleural cavity is usually negative, at least during some part of the breathing cycle, various methods have been developed that allow to aspirate air and fluid from the pleural cavity and at the same time ensure its tightness. Using the methods of drainage in the treatment of patients, the doctor must understand the principle of action of various drainage systems.
Heimlich one-way valve
This drainage system is the simplest. Drainage is connected to a one-way valve, which is designed so that it closes, if the pressure inside the tube becomes below atmospheric, and opens, if the pressure
When the pressure in the pleural cavity and, consequently, inside the tube is negative (inhalation), the soft tube collapses because the pressure outside it is greater than inside (A). When the intrapleural pressure becomes positive (exhalation), the tube expands under the action of positive pressure, ensuring the release of air from the pleural cavity (B).
Thus, when the pressure in the pleural cavity and, accordingly, in the tube becomes negative (Fig. 60, A), the valve closes and air cannot enter the pleural cavity. If the intrapleural pressure becomes positive, then the valve opens and air can escape from the pleural cavity. This system is only suitable for patients with pneumothorax, as it is not intended for suction of fluid, blood or pus. Its main advantage is simplicity and small size.
Single can exudation evacuation system
This system consists of one tank (jars), which simultaneously serves as a vessel for collecting exudate and a hydraulic gate (Fig. 61). Drainage is connected to a rigid tube inserted through a stopper into a sterile jar. A sterile isotonic solution of sodium chloride is poured into the jar so that its level is 2 cm above the end of the tube in the jar. There should be a hole in the can lid, due to which there is no excessive pressure in it when air or liquid enters. Usually the hole has a lid, so it is important not to forget to remove it before connecting the can to the patient.
This system operates as follows. With a positive pressure in the pleural cavity, the pressure in the rigid tube also becomes positive, and if it becomes higher than the pressure at the depth to which the tube is introduced into the can, air (or liquid) will be collected in the can and released into the atmosphere. With a negative pressure in the pleural cavity, the liquid from the can will rise through the tube and air will not flow into the pleural cavity and into the tube. Undoubtedly, if the end of the tube is above the level of the liquid in the can, the system will not function, and the patient will develop extensive pneumothorax.
Such a system is convenient in cases of uncomplicated pneumothorax. However, when aspirating large quantities of fluid from the pleural cavity, the level of the liquid in the can rises and in order for the fluid and air to continue to flow from the pleural cavity, the pressure in the rigid tube must increase. Another disadvantage of this system is that if the jars are randomly placed above the level of the patient’s chest, the liquid from the jar can re-enter the pleural cavity.
Dual-bank exudate evacuation system
When aspirating a large amount of pleural fluid, this system is more preferable. With this system, one can is connected to the patient, collecting exudate, and the second serves as a hydraulic valve and air valve. This means that as fluid is aspirated from the pleural cavity, the amount of fluid in another canister that serves as a hydraulic valve will not increase. The principle of operation of this system (underwater drainage system) is the same as in the case of using one tank.
Three-bank exudate evacuation system and pump use
In some cases, it is necessary to create negative pressure in the pleural cavity in order to facilitate the smoothing of the lung and more rapid evacuation of air or fluid from the pleural cavity. Using an Emerson pump with constant pressure (from -15 to -20 cm of water. Art.), It is possible to aspirate both into a single can and two can systems. However, in many medical institutions
aspiration is carried out using pumps that cannot provide a constant level of pressure. Since the uncontrolled aspiration of a large amount of fluid is dangerous, ways should be found to control it.
This method of control is the connection to the system of a third bank, as shown. One of the holes in the third can is connected to the can opening, which serves as a hydraulic
The arrows indicate the direction of movement — the air escaping from the pleural cavity.
Equal shutter. This third bank has the same hardness.
The second hole of the third canister is connected to the pump. When the pump is turned on, air enters the can if more negative pressure is created in it than at the depth to which the rigid tube is immersed. Thus, the entry of air bubbles through a rigid tube means that the level of negative pressure in the system is equal to the level of pressure at the depth at which the rigid tube is immersed. On the example shown in fig. 63, the air enters this jar from the atmosphere, the rigid tube is immersed to a depth with a pressure of -20 cm of water. Art. This means that the pressure in this bank is also 20 cm of water. Art. The same pressure exists in the next canister, which serves as a hydraulic shutter, since there is a direct connection between them. The pressure in the canister that exudate is going to be less negative than in these two canals, due to the action of the hydraulic shutter. In our example, the depth of the water layer is two centimeters, which means that the pressure in the jar into which the exudate is collected and in the pleural cavity (if the drainage tube is not filled with liquid) is at a level of —18 cm of water. Art.
The level of negative pressure in the system can be adjusted by changing the position of the rigid tube in the can, connected to the pump, or the volume of liquid in it. The adequacy of suction can be judged by the continuous flow of bubbles through a rigid tube. The flow of bubbles should not be too intense, but should be continuous. Too intense entry of bubbles only creates noise and causes rapid evaporation of the brine.
Serial Drainage Systems
As can be seen from this system of three tanks is cumbersome and inconvenient to transport if, for example, there is a need for the patient to move. Therefore, serial production of various more compact and convenient systems for aspiration of pleural fluid has been established. Their main disadvantage is that they are more expensive than older systems. The most widespread are two systems: Pleur-evac and Argyle Double-Seal.
Pleur-evac system. This disposable plastic system consists of three chambers simulating the classic three-canal system (Fig. 64). The right camera serves to collect exudate, the middle one with a hydraulic shutter and the camera on the left control the suction level. The difference between the height of the water column in the chamber that controls suction and the height of the water column in the chamber that serves as a hydraulic shutter determines the amount of pressure used for aspiration from the pleural cavity. If the pressure in the system exceeds +2 cm of water. Art
Pleur-evac exudate evacuation system, similar to the three-canal system.
The right chamber (A) is calibrated and serves to collect exudate, the middle chamber (B) is a hydraulic lock, the left chamber (B) serves to control the suction. The arrows indicate the direction of movement of air leaving the pleural cavity. If the vent is left open, the system works on the principle of a two-tank system. When the pump is operating, atmospheric air flows through the chamber (B) and is discharged through the pump.
then excess air is discharged through the valve in the chamber, which serves as a hydraulic shutter.
The advantage of this system is that it is easy to use, the volume of liquid injected can be easily measured, and the level of negative pressure created can be easily controlled. If the aspiration rate is too high, the fluid in the suction control chamber is will evaporate, which is accompanied by considerable noise .. If you do not use the pump and open the left chamber for air, the system will operate on the principle of a two-canister. If the fluid is sucked out without: pump assistance, then the permeability of the tubes can be checked by observing fluctuations in the fluid corresponding to the breathing pattern. in the chamber serving as a hydraulic shutter. When performing aspiration without using a pump, the pressure created in the drainage can be calculated as the difference between the levels of the fluid in the two arms of the chamber, which serves as a hydraulic valve.