Comparison of Wound Debridement Pressures With Updated Tests

Wound care and wound debridement are crucial in the treatment of chronic diseases and poorly healing tissue. This medical knowledge has been applied for hundreds of years; today, the use of pressurized saline for necrotic tissue debridement is considered the most effective method of treating poor wound healing.¹ Research evidence of the positive impact of this treatment on wound healing and the removal of diseased tissue has been well documented for the past several decades.^2-4 Specifically, research has found a reduction of bacteria by half or more as well as improved granulation of the healing tissue and cells.^5-9 
Various tools are used to perform wound debridement¹⁰, but the force applied to tissue by these different instruments has been poorly documented in past research, and research results have been inconsistent.¹¹ The question of which pressures are safe to use is of major concern when treating a patient. High-pressure lavage is often cited for initial debridement, with pressures reported from 35 to 70 pounds per square inch (psi),^5-7,12 but pressures this high cannot be used for chronic wounds. Some studies recommend a pressure of 5 to 15 psi^10,13 or 1 to 15 psi,^1,13 while another study specifies a narrower range of 8 to 12 psi¹⁵ when treating healing tissue on chronic wounds.² 

Several studies have reported the specific pressure produced by various debridement tools, but these studies focus on only a handful of instruments.² Another issue in several studies is a lack of detail in the description of methods used for pinpointing the distance between the tool and the tissue to ensure replication of the result. In addition, when this distance is noted, it varies widely between studies, from “as close as possible”³ to several centimeters^8,16 to several feet.^17,18 Given this vague and conflicting information, it is understandable that health care professionals are unsure about the definitive treatment for wound debridement. The need for a standardized protocol detailing recommended equipment and treatment procedure is missing from the current research and requires further study and clarification.^5,17,19 

The purpose of this study is to measure the force of fluid expulsed from various debridement instruments in a controlled environment. This study will identify the appropriate reported pressures from past literature and indicate the variations in syringe and catheter size equipment to use to replicate those pressures.

Many of the debridement instruments tested in this experiment were the same tools used in past literature or are very similar in function. This included the use of 25-, 35-, and 50-mL syringes in combination with 18-, 19-, 20-, 21-, 22-, and 25-gauge catheters. The catheters were standardized to a 1-inch length to maintain consistent parameters. A 50-mL bulb syringe was also measured. Two jet lavage systems (PulsaVac Plus, Stryker [PV]; and Waterpik Waterflosser, Waterpik [WP]) were used to measure the force exerted by the more powerful debridement tools.8 Also, commercial brand saline sprays (Neilcleanse Wound Wash, NeilMed [NMS]; and Walgreens Wound Wash, Walgreens [WWS]) were tested, which are common products used in the home and in hospitals. All other tools were tested using tap water for convenience. Finally, instruments that use oxygen to propel the irrigate solution in 3 form factors were also tested: bottle delivery (IRIG-8, Centurion Medical Products [IRG]); intravenous (IV) bag/wand delivery (DeRoyal JetOX, Global Medical Manufacturer [JTO]), and atomizer delivery (DeVilbiss Atomizer 163 RD Drive/DeVilbiss Healthcare, [ATO]). 

To measure the force produced by the different instruments, a 4-strain gauge force transducer was used, two on the top and two on the bottom, arranged like a Wheatstone bridge. The force transducer measured the pressure when the fluid hit the surface of the transducer. This transducer was connected to an analog-digital converter (MP150BIOPAC Systems, BIOPACK [BP]). An analog signal from the force transducer was connected to the BP and then amplified and conditioned with a DA100C amplifier and digitized through a 24-bit analog-digital converter at a speed of 2000 samples per second. The BP system was set at a gain of 1000, a low-pass filter of 10 Hz, and a high-pass filter of 300 Hz. Only 2 of 48 channels were used in the experiment; one channel was used to display the raw data, and the second was the calculation channel, which smoothed out the raw data. The data were recorded in grams and converted to pounds per square inch. AcqKnowledge v3.9.1 (BIOPAC) software was used to record and process these data. The assembly, calibration, and utilization of the BP system were performed by Dr Jerrold Petrofsky at Touro University Nevada in Henderson, Nevada.

Each instrument to be tested was placed 1 inch horizontally from the vertically held force transducer. When applying pressure to the syringe plungers, the tester made a measured effort to produce 10 pounds of pressure for several seconds across all tests to maintain a relatively perpendicular constant stream for each. Figure 1 shows the force applied on the syringe and measured on the pressure gauge (DuraChoice, Irving, TX). The inner diameter and cross-sectional area of each catheter or nozzle were measured for each instrument to calculate the pounds per square inch from the raw data. The equation used to calculate the area was A = πr². The data were input and analyzed in Microsoft Excel. The force was measured in grams and then multiplied by gravity to create force in Newtons, which was then calculated to force in millimeters by dividing the Newtons by the area of the diameter calculated. This number was finally multiplied by 145.038 to calculate to pounds per square inch. These numbers were rounded to the hundredths decimal place for reporting purposes.

The 3 types of tools (syringes, pulsative tools, and oxygen-propelled tools) delivered different ranges of pressures. Figures 2-5 detail the average pressures produced by each tool.

As the catheter gauge with syringes was increased from 14 to 21, the resulting pressure applied increased. However, in all 3 syringe volumes, there was a slight decrease in the pressure applied from the 19-gauge to the 20-gauge catheters. There was a similar decrease in pressure from the 14-gauge to the 16-gauge catheters, but only in the 35-mL syringe catheter.  Interestingly, in all volumes of syringes, the applied pressure decreased from the 21-gauge to the 22-gauge catheters, remained the same from the 22-gauge to 24-gauge catheters, and increased from the 24-gauge to 25-gauge catheters. The BP measured the pressure applied by various syringes with different volumes and catheter gauges, as shown in Figure 1. Table 1 shows the catheter gauge cross-sectional areas.

Figure 2 presents the pressure applied by various wound irrigation instruments and products, including a bulb syringe, a pulse wound debridement tool, a water flosser with distilled water, and a commercial saline solution. Table 2 provides a summary of the cross sections of every nozzle or opening of the non-syringe instruments tested. Figures 3, 4, and 5 show the pressure applied by the oxygen-propelled instruments using the pressure settings according to the manufacturer’s instructions for each device, except for the ATO. The pressure settings used for this instrument paralleled those of the JTO because both instruments provide “mist-like” irrigation at the wound site.

The WP at middle-pulse and high-pulse applied the greatest amount of pressure at 117.53 psi and 129.80 psi, respectively, and the JVP at low-pulse and high-pulse recorded 21.14 psi and 17.94 psi, respectively. The commercial saline sprays, WSO and NMO, applied the least amount of pressure at 13.94 psi and 3.72 psi, respectively.

An interesting result was the high pressure recorded by the bulb syringe. This may be attributed to the initial burst of saline spray that occurs with a hard squeeze on the bulb, and then a more constant, less powerful, stream can be seen for several seconds. Also of note was the difference between the 2 commercial pressurized saline spray brands. A difference of over 10 psi was seen between these 2 sprays, which is a sizable difference. This may be due to a faulty cannister for the NMO spray, which as a retail item, may be subject to occasional manufacturing variances.

Taking each of these observed values and comparing them with those documented in previous research shows some variation in how the tools perform. Edlich and Thacker recommended a pressure of 7 to 8 psi using a 35-mL syringe with a 19-gauge catheter as the most effective for wound irrigation.² However, the study results using the 35-mL syringe with a 19-gauge catheter showed an applied pressure of 11.6 psi, which is higher but still falls within the safe pressures identified for tissue debridement. Specifically, pressures between 4 and 15 psi do not destroy tissue based on clinical practice guidelines for wound care.¹⁵ Additionally, the dramatic decrease and rise in observed pressures between 21-gauge and 25-gauge catheters also raise some concern about consistency of applied pressure during clinical use.

Brown et al,⁵ Bhaskar et al,⁶ and Stewart et al²⁰ measured the applied pressure from a pulsatile jet and found it to be between 50 and 70 psi, while the present experiment found that the PV had a pressure of 17.94 psi at low pulse and 21.14 psi at high pressure. This discrepancy is likely due to a difference between the products used in the present experiment and those used in past research. Another explanation for the discrepancy is the fact that the size of the force transducer used in this study was unable to account for the wide pulsatile spray of the PV.

Overall, the observed values for the pressure applied by these tools were inconsistent with those found in previous studies. One of the major factors that must be considered is the role of human error and variability in this experimental approach. Health care workers performing wound debridement may have the issue of human variability as well and could benefit greatly from knowing which tools apply the correct pressure and how to gauge the pressure applied with a syringe. It is apparent that standardization of pressure applied and further testing of commonly used tools is desirable. 

Several of these instruments are safe to use for irrigation and safe debridement at bedside.^1,9,10,13,15 Keeping with recommendations from prior studies and guidelines, the standard pressures should range from 4 to 15 psi in steady increments for safe debridement and from 1 to 15 psi in steady increments for wound irrigation.¹ Easily located items, such as syringes and various sizes of catheters, are economical and prudent, and most clinicians know how to use these instruments. Commercial sprays purchased with pressurized saline are safe and easy to use, even when held upside down. Also, the JTO and ATO at the lower oxygen pressures are also safe instruments.

However, the JPV and IRG instruments are too forceful and would cause more tissue damage to the healing wound and would debride away more than just debris from the wound. These higher-pressure instruments should be reserved for other areas that require nonselective debridement due to known or suspected contamination.

During this study, it became evident that the amount of pressure applied to the syringe plunger had an effect on the overall pressure of the debridement stream. After identifying the need for consistent application of pressure at the plunger between treatments and personnel, we developed and deployed a device to aid in applying constant pressure. By using a pressure gauge attached to the syringe and catheter setup, the individual applying force to the plunger could see exactly how much pressure was being manually applied to the syringe contents. 

Our results demonstrate the ability to consistently apply and monitor the debridement force used with this device and any syringe and catheter combination. A simple addition of a T-bar stop valve with inexpensive tubing and pressure gauge allows nearly any syringe and catheter combinations to deliver a pressure within a safe and desired range. Future studies can be performed using this apparatus to measure consistency of delivered pressures between applications and operators. Further animal and human trials can also be conducted to measure healing rates and outcomes with this new experimental method to confirm the recommended pressure ranges mentioned in previous experiments.

Limitations to this study include the use of tap water versus normal saline in testing. The molecular weights are different: normal saline is 58.44 g/mol, and tap water is 18.02 g/mol. Additionally, portable oxygen tanks were used, and the oxygen regulators were not verified for calibration. Hospitals use wall oxygen or wall air which can have different pressures.

This study was intended to examine the applied pressures produced by various wound-cleaning tools and compare those values with those reported in the literature. Several types of tools were tested, including syringe and catheter combinations, pulsative irrigation tools, and oxygen-propulsion irrigation tools. Values observed were different from those reported in the literature, but most instruments produced pressures that were safe for bedside use. However, certain tools produced higher pressures that were not suitable for routine wound care. Findings from this study can be used by clinicians to choose appropriate tools and to monitor pressure when they use various common irrigation tools.

¹Associate Professor, School of Physical Therapy, Touro University Nevada, Henderson, NV

Address all correspondence to: Stacy J. Fisher, DPT, DBA, 874 American Pacific Drive, Henderson, NV 89014; email: sfisher@touro.edu

None disclosed