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    Improve your suctioning technique

    RN/DREXEL Home Study Program

    Improve your suctioning technique

    CE credit is no longer available for this article. (Expired May 2005)

    Originally posted May 2003


    PATRICIA CARROLL, a member of the RN editorial board, is an independent nurse consultant and health care coordinator at Shelter NOW, a facility for the homeless in Meriden, Conn.

    KEY WORD: suction, vacuum, pressure gradient, flow rate, negative pressure

    Here are a few simple steps you can take to make the most of your suctioning equipment and improve your technique.

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    Yes, suctioning is often a routine procedure, but it's potentially a life-saving one—and therefore not a technique to take for granted. While many nursing textbooks, procedure manuals, and online resources tell you how to carry out these procedures, few explain what you can do to use your suctioning equipment more safely and efficiently. That's what I'll review here.

    There are three main types of suction apparatus: electric or battery-operated devices like those commonly used in home care and the Gomco device commonly used for nasogastric drainage; venturi systems that use compressed gas to create vacuum and are most often found on tank-equipped infant warmers; and wall systems that bring vacuum through pipes to all parts of a hospital for use when and where it's needed. This article will focus on the hospital-wide system that is connected to a wall outlet at the bedside.

    The highs and lows of suctioning

    Fluids and gases move from areas of higher pressure to areas of lower pressure across what's called the pressure gradient. Vacuum is a space in which the pressure is significantly lower than the surrounding pressure.

    If a device (in this case, the hospital's piped vacuum system) is used to create a zone of pressure that's lower than that of the patient, gases and fluids will be drawn out of the patient into this area of lower pressure. The clinical application of vacuum to create this pressure gradient is called suction.1

    When you perform a procedure such as clearing a patient's airway with a Yankauer rigid tip or with a flexible catheter, you're suctioning the airway. When the procedure is to empty a patient's stomach, you're applying suction to the nasogastric tube. While the device you use to control the amount of negative pressure used for those procedures is commonly referred to as a suction regulator, "vacuum regulator" is a more accurate term.

    The vacuum provided by a hospital's piped system can fluctuate. In an acute care hospital, there will be a greater draw on the building's system during the peak times for surgery in the OR, potentially making the vacuum weaker in other patient care areas. When the OR is closed (typically at night), there will be less demand on the system, so the vacuum in other areas will be stronger.

    At the bedside, the vacuum can fluctuate when the material being suctioned changes, or if the tubing becomes occluded.

    Factors that can affect the flow rate

    Flow rate is the "horsepower" behind suctioning; it describes how fast air, fluid, or secretions are removed from the patient and is a key element to suctioning efficiency. Ideally, you want the highest flow rate with the lowest negative pressure. Negative pressure is the pressure below atmospheric pressure that's created by the suction system. Three main factors affect your suction system's flow rate.

    • The amount of negative pressure,
    • The resistance of the suction system (anything related to the equipment that impedes flow), and
    • The viscosity (thickness) of the matter you're suctioning.

    The level of negative pressure is displayed on a gauge and is set by turning a knob on the vacuum regulator. Zero on the gauge is equivalent to atmospheric pressure; the numbers indicate increments of pressure below atmospheric pressure. Generally, the higher the negative pressure, the higher the flow.

    The maximum amount of negative pressure you should use is limited by what is safe for the type of suctioning you're doing. For instance, high negative pressure applied to mucosa can cause tissue damage.2 How to determine how much negative pressure you need for a suctioning procedure—and how to limit the maximum amount of negative pressure—is discussed further below.

    Several factors affect the degree of resistance in the suction system, including the inner diameter of the suction catheter used.3 You can increase flow more by increasing the catheter diameter than you can by increasing the negative pressure or shortening the length of the catheter. In most clinical applications, however, the size of the patient will be the determining factor for catheter size.

    In general, for tracheostomy and endotracheal suctioning, the outer diameter of the suction catheter should be no greater than one-half the inner diameter of the artificial airway.4 To determine the correct suction catheter size (measured in French), simply double the size of the artificial airway (measured in mm). For example, a pediatric patient with a 5 mm endotracheal tube should be suctioned with a size 10 French catheter (that's only 3.33 mm in diameter) or smaller. An adult with an 8 mm endotracheal tube could be safely suctioned with a size 16 French catheter.

    The design of the vacuum regulator and related equipment such as the overflow trap, collection bottle, and connecting tubing can also affect resistance.

    Finally, flow rate is affected by the thickness, or viscosity, of the material being suctioned. Watery fluids such as blood will move through the suction system much more quickly than thick substances such as sputum. Previously, it was believed that instilling normal saline into an artificial airway would thin secretions, which would make them easier to suction and enhance flow rate. But nursing research has shown that this is not the case, and the practice should be abandoned.5,6

    How to ensure optimal flow rate

    There are several steps you can take to enhance flow rate.

    First, check that the vacuum wall outlets and pipe system are clean and free flowing. Examine the wall outlet. Outlets are more likely to become clogged when they aren't being used (whether or not a regulator is attached) or when the air contains particulates such as lint, dust, or the residue of powder from gloves taken off throughout the day as a routine part of patient care. You should be able to feel a pull from the vacuum if you put your finger across the outlet.

    Be sure to use an overflow trap between the regulator and the collection bottle. This safety device collects any suctioned material that accidentally overflows from the collection bottle and prevents it from being pulled into the regulator, wall outlet, or pipe system. Such overflows can significantly decrease flow and will contaminate the system.

    Does your suction system contain a filter? A filter designed to clean the air that passes through it can restrict airflow if it becomes filled with dust or particles. Some suction systems use disposable canisters and liners with filters that are also disposable. However, if your hospital's system uses a separate filter between the bottle and the vacuum regulator, it must be changed frequently or flow will be impeded.

    In addition, the regulators themselves need to be carefully checked for clogging. Check with biomedical engineering to make sure there's a maintenance schedule for the regulators you use so that they remain at their peak efficiency. Don't forget any regulators that are kept on crash carts—they should be checked regularly, too, since you may need to depend on them in an emergency.

    If you notice a problem with your suction system, particularly if it doesn't seem to pull out fluid, air, or secretions as effectively as it should, check with the biomedical department. A device called a vacuum system flow rate tester can be used to measure the flow rate at the vacuum outlet and help detect clogged outlets. Outlets become clogged easily, and regular monitoring with this tester will help optimize your suction efficiency.

    Shorter lengths of connecting tubing can also enhance flow. If you have extra tubing draped around the regulator at the bedside, consider cutting it.

    Use the largest diameter equipment you can without causing tissue damage during the particular suctioning procedure you're performing. A study in emergency medicine evaluated the effect of increasing equipment diameter on suctioning 90 ml of simulated vomitus. The use of 3/4-inch suction tubing evacuated the substance 10 times faster than did 1/4-inch tubing.7

    Connectors, for instance, those used between lengths of tubing or between connecting tubing and the nasogastric tube, can also decrease the flow rate. Sometimes these connectors are unnecessarily small and may be the narrowest part of the entire suction system. Don't sacrifice flow if you don't have to—use the largest connectors you can.

    Finally, you can maximize flow by not using Y connectors, which create two vacuum outlets from one wall outlet. This reduces your flow rate, potentially in half.

    If your hospital is undergoing renovations and you don't have enough vacuum outlets in your practice area, ask for more to be installed as part of the renovation. Additional wall outlets will make it unnecessary to use Y connectors. If those outlets are planned during construction, the building's entire vacuum system will be upgraded to be powerful enough to serve the additional outlets, and your suction system will run much more efficiently.

    Setting a maximum negative pressure

    Suction is a dynamic process; pressures and flow rates will continually fluctuate as the demands on the system or contents of the tubing change. Most vacuum regulators are designed with a module that compensates for these changes to maintain a preset maximum negative pressure.

    When you prepare to suction, you usually need to first establish a limit of maximum negative pressure for the specific procedure you're about to perform. In situations where your suction catheter won't be in a closed space or touching tissue, such as suctioning irrigation fluid from a patient's operative field in the OR, it may be acceptable to use a free-flow system with no preset maximum pressure. However, when suctioning an airway or applying suction to a nasogastric tube, the mucosa can be easily damaged, and an upper limit of pressure should be established for patient safety.

    Before setting the maximum negative pressure, you need to determine how much negative pressure is appropriate. The maximum negative pressure should be set as low as possible and yet still allow you to effectively clear pulmonary secretions or empty the stomach.

    There is little research to guide nurses' choice of an appropriate level of negative pressure for various suctioning procedures. For example, a review of published (but not referenced) guidelines for airway suctioning found suggested levels of 50 to 100 mm Hg for infants, 80 to 120 mm Hg for children, and 100 to 150 mm Hg for adults.4,8,9

    However, none of these recommendations are evidence-based. Ultimately you should consult your facility's guidelines and use your own clinical judgment to weigh the maximum amount of negative pressure you use against the risk of tissue damage.

    Occluding the tubing is a key step

    To properly set the maximum negative pressure, completely occlude the tubing (usually by folding the connecting tubing below the regulator in half) while setting the regulator dial to the level of pressure you determine is safe for your patient and the procedure you're performing. If you don't occlude the tubing, you can set a pressure level, but you'll have no way of knowing what the maximum could be if the tubing became filled with thick material from the airway or the stomach, or if the catheter tip is otherwise occluded.

    Having the right suction device set up properly at the right moment can save a patient's life. But even when you are carrying out routine suction procedures, keep in mind the steps you can take to maximize the effectiveness of your equipment and to provide your patients with the safety of an appropriate negative pressure limit. This will minimize the risks of suctioning while enhancing your care. You may not think about suctioning as an exciting topic, but it is clearly an essential foundation for safe and effective daily nursing practice.


    1. Carroll, P. (1995). The principles of vacuum and its use in the hospital environment. Laurel, MD: Ohmeda Medical, Inc.

    2. Czarnik, R. E., Stone, K. S., et al. (1991). Differential effects of continuous versus intermittent suction on tracheal tissue. Heart Lung, 20(2), 144.

    3. American Society for Testing and Materials. (1986). Standard specification for medical and surgical suction and drainage systems. Publication F 960-86. Philadelphia: American Society for Testing and Materials.

    4. Berman, A., Snyder, S., et al. (Eds.). (2002). Kozier & Erb's techniques in clinical nursing (5th ed.). Upper Saddle River, NJ: Prentice Hall.

    5. Ackerman, M. H., Ecklund, M. M., & Abu-Jumah, M. (1996). A review of normal saline instillation: Implications for practice. Dimens Crit Care Nurs, 15(1), 31.

    6. Raymond, S. J. (1995). Normal saline instillation before suctioning: Helpful or harmful? A review of the literature. Am J Crit Care, 4(4), 267.

    7. Vandenberg, J. T., Rudman, N. T., et al. (1998). Large-diameter suction tubing significantly improves evacuation time of simulated vomitus. Am J Emerg Med, 16(3), 242.

    8. American Association for Respiratory Care. (1993). AARC clinical practice guideline: Endotracheal suctioning of mechanically ventilated adults and children with artificial airways. Respir Care, 38(5), 500.

    9. Whitaker, K. B. (2001). Comprehensive perinatal and pediatric respiratory care. Albany, NY: Delmar Thomson Learning.


    Emil Vernarec, ed. Patricia Carroll. Improve your suctioning technique. RN May 1, 2003;66:30ac2.

    Published in RN Magazine.