Enhancing the safety of medical suction through innovative technology | february 2008 | rt for decision makers in respiratory care
Enhancing the Safety of Medical
Suction Through Innovative
by Patricia Carroll, RN, BC, CEN, RRT, MS
Vacuum regulators sold in North America require occlusion of the tube before setting or changing
vacuum levels, but clinicians often are not aware of this requirement or skip this step when pressed
Medical suction is an essential part of clinical practice. Since the 1920s, ithas been used to empty the stomach, and in the 1950s, airway suctionlevels were first regulated for safety. Today, medical suction is used forneonates and seniors—and for patients weighing between 500 grams and500 pounds. Medical suction clears the airway, empties the stomach,decompresses the chest, and keeps the operative field clear. It is essentialthat clinicians have reliable equipment that is accurate and easy to use.
Why a Safety Mindset Is Important
The current focus on patient safety extends to suction procedures and routines. When suction pressures aretoo high, mucosal damage occurs, both in the airway1 and in the stomach. If too much negative pressure isapplied through a chest tube, lung tissue can be drawn into the eyelets of the thoracic catheter.2Researchers are examining the connection between airway mucosal damage and ventilator-associatedpneumonia. In pediatrics, airway suction catheters are inserted to a premeasured length that avoids lettingthe suction catheter come in contact with the tracheal mucosa distal to the endotracheal tube.3 Mucosaldamage can also be mitigated with appropriate suction techniques, and every effort should be made toreduce this insult to the immune system of patients who are already compromised. Damaged airwaymucosa releases nutrients that support bacterial growth,4 and Pseudomonas aeruginosa
and otherorganisms are drawn to damaged epithelium.5,6 Mucosal damage in the stomach can result in bleeding andanemia as well as formation of scar tissue.
Physics of Suction
Flow rate is the term used to describe how fast air, fluid, or secretions are removed from the patient.
Ideally, clinicians need the best flow rate out of a vacuum system at the lowest negative pressure. Threemain factors affect the flow rate of a suction system:
The amount of negative pressure (vacuum)The resistance of the suction systemThe viscosity of the matter being removed
The negative pressure used establishes the pressure gradient that will move air, fluid, or secretions.
Material will move from an area of higher pressure in the patient to an area of lower pressure in thesuction apparatus. The resistance of the system is determined primarily by the most narrow part of the
system—typically, a tubing connector—but the length of tubing in the system can increase resistance aswell. Watery fluids such as blood will move through the suction system much more quickly than will thicksubstances such as sputum. At one time, it was thought that instilling normal saline into an artificial airwaywould thin secretions, enhancing the flow of secretions out of the airway, but research shows that nothinning occurs and that patients' oxygenation drops with saline installation. Thus, the practice should beabandoned.7,8
Set a Safe Level
A nurse passing the bedside of an infant in the ICU saw blood inside the tube used for airway suction.
After checking the child's condition, it was evident that bleeding was not expected.
Further investigation determined the maximum level of negative pressure set on the wall regulator was -200 mm Hg, far more than recommended suction levels for infants. The nurse performing the suctioningdid not occlude the tubing to set a safe maximum level of negative pressure (personal communication toOhio Medical Corporation).
Increasing the internal diameter of suction tubing or catheters will increase flow better than will increasingthe negative pressure or shortening the length of the tube. In most clinical applications, however, the sizeof the patient will be the key factor determining what size catheter can be safely used. Researchers at theMadigan Army Medical Center explored factors affecting evacuation of the oropharynx for emergencyairway management. They tested three substances—90 mL of water, activated charcoal, and vegetablesoup—with three different suction systems, progressing from a standard 0.25-inch internal diameter to a0.625-inch internal diameter at its most restrictive point. All systems evacuated water in 3 seconds. Thelarger diameter tubing removed the soup 10 seconds faster and the charcoal mixture 40 seconds faster thanthe traditional systems. The researchers note that this advantage in removing particulate material can speedairway management and reduce the risk or minimize the complications from aspiration.9-11
Occlude to Set for Safety
Vacuum regulators are ever-present in the hospital setting. Clinicians use them daily and may not be asattentive to this equipment, what with the demands of monitors and devices alarming and competing forthe clinician's attention and time. Few clinicians learn the finer points of setting up suction systems. Anursing fundamentals text published in 200712 does not specify critical elements except to tell the nurse tofollow manufacturers' instructions. The text leaves out the critical, universal "occlude to set" steprecommended by all North American manufacturers of vacuum regulators.
While a number of organizations have published guidelines, ultimately the clinician must determine themaximum allowable level of negative pressure that can be applied to the patient. This is determined by anumber of factors: where the suction pressure is applied (airway, stomach, oropharynx, pleural space,operative field), the age and size of the patient, the susceptibility for mucosal or other tissue damage, andthe risks associated with removing air during the suction procedure.
Once the maximum level has been determined, the vacuum regulator must be adjusted so that themaximum pressure is locked in; that is, the regulator must be set correctly so it will not permit a higherpressure to be transmitted to the patient. With traditional technology, the clinician must actively occludethe system by either pinching the suction tubing closed, or occluding the nipple adaptor (where the tubingis attached) with a finger. Once the system is occluded, the regulator is set to the maximum desiredpressure; then the occlusion is released. If the system is not occluded during setup, the maximum pressureis then unregulated and can spike to harmful levels (see Figures 1,2).
Suctioning is a dynamic process. As catheters are used to remove substances from the body, the degree ofopen flow continually changes based on the fill of the catheter and the viscosity of the substance beingremoved. Under these dynamic conditions, the regulator continually compensates by adjusting flow ratewithin the device and the tubing to maintain the desired negative pressure. Periodically, mucus plugs orparticulate matter will occlude the patient tube. If the system was not occluded to establish the maximumsafe pressure at setup, pressure will spike to clear the occlusion, and once the occlusion passes, the patientwill be subjected to potentially dangerous, unregulated vacuum pressures (see Figure 1).
Suction System Setup
Vacuum regulator12-inch connecting tube1500 cc (empty) collection bottle6-foot standard connecting tubing 14 Fr. Suction catheter
Figure 1 illustrates results of a bench test of two suction systems. The systems were set up identically asnoted in Figure 2. The desired maximum level of suction is 100 mm Hg (A). One system was set at 100mm Hg with the system open to flow (red line); the other was set by occluding the system to set 100 mmHg (green line). During open flow, the "occlude to set" system will have a lower pressure than the desiredmaximum pressure because there are no occlusions in the system (B). Once suctioning begins, a dynamicflow condition occurs with varying levels of obstruction, and pressure rises in both systems. The point ofmaximum suction is key. In the "occlude to set" system, the pressure never rises above the desiredmaximum pressure of 100 mm Hg. In the other system, pressure in this bench test spiked to 125 mm Hg of
unregulated suction. Without "occlude to set," the pressure can rise to 25% higher than the desiredmaximum level or more, exposing the patient to a safety hazard when regulated suction is needed.
Higher negative pressure is a particular hazard for patients with friable mucosa in the airway or stomach,making it more susceptible to traumatic tears. It is also a hazard for infants who have small lung volumes.
When all other variables are stable, a 25% increase in negative pressure will increase the amount of airpulled through the system by 25%. That increase could result in a significant loss of lung volume inintubated neonates and infants.13
New Technologies Enhance Safety
An ideal patient safety device removes clinician variables as much as possible by providing the addedsafety passively while the clinician carries out the procedure. Traditionally, the optimal safety of regulatedvacuum pressure has depended on the clinician's action to occlude the system to set maximum pressure.
New technology, an intermittent suction unit (ISU), occludes the system automatically when the clinicianadjusts the pressure level. This creates an effective, passive safety system that removes the clinicianvariable and protects the patient from unintended, unregulated pressure spikes during suction procedures.
The "push to set" option assures the clinician that the patient will not be subjected to pressure higher thanthat set on the regulator. Another key safety aspect of any vacuum regulator is the ability to quickly adjustto full vacuum mode when emergency strikes and rapid evacuation is essential. A dual-spring design ofthe regulating module contained within the vacuum regulator provides the clinician with the ability tocontrol vacuum levels more precisely in the clinical range of 0-200 mm Hg as well as the ability toachieve full vacuum when needed with only two turns of the knob on the regulator. In other regulators, sixor more knob turns are needed to achieve "full vacuum," and "full vacuum" capability may be limited tothe clinical range. Since full vacuum is needed in emergency conditions, this enhanced responsivenesssaves time when seconds are critical. While vacuum regulators are often considered basic equipment in thehospital, research and innovation has shown vacuum regulators do have a role in enhancing patient safetyin clinical settings. Clinicians should advocate for technology that provides passive safety protection,enhanced control of vacuum pressures, rapid response, and ease of use—all of which contribute to aculture of safety around the patient.
Patricia Carroll, RN, BC, CEN, RRT, MS, is the quality management coordinator at Franciscan HomeCare and Hospice Care in Meriden, Conn. For further information, contact.
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