| TRADITIONAL CHEST DRAINAGE In 1967, Deknatel introduced the first integrated disposable chest drainage unit based on the threebottle system. Now that we have reviewed normal anatomy, physiology, and pathophysiology, let’s discuss each of the three chambers in detail. COLLECTION CHAMBER At the right side of the unit is the collection chamber (figure 13, D). The patient tubing connects the drainage unit directly to the chest tube. Any drainage from the chest flows into this chamber. The collection chamber is calibrated and has a write-on surface to allow for easy measurement and recording of the time, date, and amount of drainage. WATER SEAL CHAMBER The middle chamber of a traditional chest drainage system is the water seal. The main purpose of the water seal is to allow air to exit from the pleural space on exhalation and prevent air from entering the pleural cavity or mediastinum on inhalation. When the water seal chamber is filled with sterile fluid up to the 2 cm line, a 2 cm water seal is established (figure 14). To maintain an effective seal, it is important to keep the chest drainage unit upright at all times and to monitor the water level in the water seal to check for evaporation. Bubbling in the water seal chamber indicates an air leak. The patient air leak meter indicates the approximate degree of air leak from the chest cavity (figure 14). The meter is made up of numbered columns, labeled from 1 (low) to 7 (high). The higher the numbered column through which bubbling occurs, the greater the degree of air leak. By documenting the number, the clinician can monitor air leak increase or decrease. The water seal chamber also has a calibrated manometer to measure the amount of negative pressure within the pleural cavity (figure 13, F). The water level in the small arm of the water seal rises as intrapleural pressure becomes more negative. If there is no air leak, the water level should rise and fall with the patient’s respirations, reflecting normal pressure changes in the pleural cavity. During spontaneous respirations, the water level should rise during inhalation and fall during exhalation. If the patient is receiving positive pressure ventilation, the oscillation will be just the opposite — the water level should fall with inhalation and rise with exhalation. This oscillation is called tidaling and is one indicator of a patent pleural chest tube. At the top of the water seal chamber is a high negativity float valve and high negativity relief chamber (figure 13, C). These safety features maintain the water seal in the event of high negative pressures. Three situations can cause high negative pressure: 1. The patient in respiratory distress, coughing vigorously, or crying; 2. Chest tube stripping; 3. Decreasing or disconnecting suction . High negativity is indicated by rising water in the small arm of the water seal chamber. If the water rises beyond –20 cm, the high negativity float valve will rise and impede the flow of water, allowing the patient to develop as much negativity as needed for inspiration. In instances of falsely imposed high negative pressure, such as stripping chest tubes, water will continue to rise, filling the high negativity relief chamber. The relief chamber automatically vents excessive negative pressure, thus preventing respiratory compromise from accumulated negativity. Vigorous milking or stripping can create dangerously high negative pressures. Research has documented negative pressures as high as –450 cm H2O. Pleurevac prevents accumulation of excessive high negative pressure as discussed above; however, the transient high negative pressures created by vigorous stripping can put the patient at risk for mediastinal trauma and graft trauma. Use extreme caution and follow your hospital policy. A manual high negativity relief valve is located on top of chest drainage systems (figure 15). Depressing the high negativity relief valve allows filtered air into the system, relieving negativity and allowing the water level to return to baseline in the water seal. Use the high negativity relief valve with caution. If suction is not operative, or if operating on gravity drainage, depressing the high negativity relief valve can reduce negative pressure within the collection chamber to zero (atmosphere) with the resulting possibility of a pneumothorax. WET SUCTION CONTROL The chamber on the left side of the unit is the suction control chamber (figure 13, H). Traditional chest drainage units regulate the amount of suction by the height of a column of water in the suction control chamber. Note: it’s the height of water, not the setting of the suction source, that actually limits the amount of suction transmitted to the pleural cavity. A suction pressure of –20 cm H2O is commonly recommended. Lower levels may be indicated for infants and for patients with friable lung tissue, or if ordered by the physician. In a wet suction control system such as the Pleur-evac A-7000/A-8000 series, fill the suction control chamber to the desired height with sterile fluid. Connect the short suction tubing to a suction source, and adjust the source suction to produce gentle bubbling in the suction control chamber. Increasing suction at the suction source will increase airflow through the system, but will have minimal effect on the amount of suction imposed on the chest cavity. Excessive source suction not only causes loud bubbling (which can disturb patients and caregivers), but also hastens evaporation of water from the suction control chamber. This results in a lower amount of suction applied to the patient as the level of water decreases. Self-sealing diaphragms are provided to adjust the water level in this chamber. NEW GENERATION CHEST DRAINS DRY SUCTION The next step in the evolution of chest drainage units was the development of dry suction control chambers. Dry suction control systems provide many advantages: higher suction pressure levels can be achieved, set-up is easy, no continuous bubbling provides for quiet operation, and there is no fluid to evaporate which would decrease the amount of suction applied to the patient. Instead of regulating the level of suction with a column of water, the dry suction units are controlled by a self-compensating regulator. A dial to set the suction control setting is located on the upper left side of each unit. To set the suction setting, rotate the dial until the red stripe appears in the semi-circular window at the prescribed suction level and clicks into place. Suction can be set at –10, –15, –20, –30, or –40 cm of water. The unit is pre-set at –20 cm of water when opened (figure 16). Connect the short suction tubing or suction port to the suction source. Source suction must be capable of delivering a minimum of 16 liters per minute (LPM) air flow. Increase suction source until the orange float appears in the suction control indicator window. The unique design of the Pleur-evac dry suction control immediately responds to changes in patient pressure (patient air leak) or changes in suction pressure (surge/decrease at the suction source). The setting of the suction control dial determines the approximate amount of suction imposed regardless of the amount of source suction — as long as the orange float appears in the indicator window. Patient situations that may require higher suction pressures of –30 or –40 cm H2O include: a large air leak from the lung surface, empyema or viscous pleural effusion, a reduction in pulmonary compliance, or anticipated difficulty in expansion of the pulmonary tissue to fill the hemithorax. In the presence of a large air leak, air flow through the Pleur-evac may be increased by increasing source suction, WITHOUT increasing imposed negativity. It is not necessary to change the suction setting on the Pleur-evac unit to accommodate high air flows. The suction control level can be changed at any time as prescribed by simply rotating the dial to the new suction setting. Confirm that the orange float remains in the suction control indicator window at the new suction setting. If suction setting is changed from a HIGHER to a LOWER level, the patient negativity may remain at the higher level unless the negativity is relieved. Use the manual high negativity relief valve to reduce negativity to desired level. Both the wet suction and dry suction series of Pleurevac have a positive pressure relief valve that opens with increases in positive pressure, preventing pressure accumulation (figure 15). Normally, air exits through the suction port. Obstruction of this route (i.e. a bed wheel rolls on top of the suction tube, or the suction port is capped after suction discontinued) could cause accumulation of air in the system leading to tension pneumothorax. This safety feature allows venting of the positive pressure automatically, thus minimizing the risk of tension pneumothorax. ONE-WAY VALVE In the Pleur-evac Sahara™, (figure 17) a one-way valve replaces the traditional water seal. No water is required to establish the one-way seal. Just connect the patient tube to the patient’s thoracic catheter and the patient seal is established for patient protection. The one-way valve maintains the patient seal even if the unit is tipped over. Unlike a water seal system in which the seal may be lost when the unit is tipped, the Sahara dry seal protects the patient from atmospheric air. If air leak diagnostics are desired, the patient air leak meter must be filled to the “Fill” line. The fluid in the patient air leak meter is used for air leak detection as described earlier and is not a water seal. In the Pleur-evac Sahara, negative pressure exists in the collection chamber when the YES can be seen in the indicator window (figure 18). During gravity drainage before normal negative pressure has been re-established in the pleural cavity, the indicator may intermittently indicate negative pressure with patient respiration. During suction drainage, the pressure indicator should indicate a negative pressure continuously. The negative pressure indicator does not confirm drainage tube patency. Routinely check the drainage tube patency. The Pleur-evac Sahara system also has an automatic high negative pressure relief valve to limit the negative pressure to approximately –50 cm of H2O. A manual high negativity relief valve is also provided to vent excessive negativity as described earlier. GRAVITY DRAINAGE Not all patients require suction. Suction may be discontinued to transport a patient; it may also be discontinued 24 hours before chest tube removal. Consult hospital policy to determine if an order is needed to institute or discontinue suction. If suction is discontinued, the suction tube or port should remain UNCAPPED and free of OBSTRUCTIONS to allow air to exit and minimize the possibility of tension pneumothorax. TO CLAMP OR NOT TO CLAMP? The decision whether to clamp a chest tube when the drainage system has been knocked over and disconnected or otherwise disrupted is based on your initial assessment of the water seal chamber and air leak meter. If there has been no bubbling in the water seal, you can deduce there is no air leak from the lung. Therefore, the tube may be clamped for the short time it takes to reestablish drainage. If there has been bubbling and your assessment has determined there is an air leak from the lung, you MUST NOT clamp the chest tube. Doing so will cause air to accumulate in the pleural cavity since the air has no means of escape. This can rapidly lead to tension pneumothorax. The few times you should clamp a chest tube are when: 1) You are performing a physician-ordered procedure such as sclerosing, 2) Assessing for a leak, or 3) Prior to removing the chest tube to determine if the patient can do without the chest tube (with a physician order). You should never clamp a chest tube during patient transport unless the chest drainage system becomes disrupted during patient movement, and then only if there is no air leak. |
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CHEST DRAINAGE AS A THERAPEUTIC INTERVENTION
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Chest Drainage Systems
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