Comparison of Negative Pressure Wound Therapy (NPWT) Systems With Wound Pressure-Regulating-Technology (PRT): Incidence of Blockage Alarms When Dressing System Contains a Blockage Condition


Blockages occurring in NPWT systems can prevent deliverance of target negative pressure to the wound site. Blockage indication in NPWT systems is important in mitigating factors that can lead to poor outcomes such as maceration1 and infection2 associated with pooled fluids. Appropriate engineering/design elements are required to ensure blockage alarms are triggered under clinically relevant conditions.

Evaluate the ability of NPWT systems to trigger blockage alarms when the dressing system contains a blockage condition.

Three PRT-based NPWT systems (NPWT-A◊, NPWT-B◊◊, NPWT-C◊◊◊) were tested (3 units x 3 dressings each). Units were set to a clinically relevant target pressure in a simulated wound environment. Two separate blockage conditions were intentionally created; one that simulated a clot stuck at the dressing/tubing interface (wound site) and one that simulated clamping/pinching of the dressing tubing. NPWT systems were tested until the earlier of 60 minutes or occurrence of blockage alarm. Standard statistical methods were utilized.

NPWT-A◊ and NPWT-B◊◊ systems consistently presented blockage alarms for both blockage conditions; NPWT-C◊◊◊ systems did not consistently trigger a blockage alarm during the simulated clamping/pinching of the dressing tubing and did not trigger a blockage alarm at all during the simulated clot blockage condition. Following application of each blockage condition, negative pressure (NP) at the wound site was ~0 mmHg for all groups, consistent with a complete blockage situation. Average time to trigger blockage alarm for the simulated clamping/pinching blockage condition was 82.3 seconds for NPWT-A◊ ,85.2 seconds for NPWT-B◊◊, and 2123.7 seconds for NPWT-C◊◊◊. These times proved to be significantly different when comparing NPWT-A◊ to NPWT-C◊◊◊ (p<0.001) and NPWT-B◊◊ to NPWT-C◊◊◊ (p<0.001).

PRT-based NPWT systems are not equivalent in performance. NPWT-A◊ and NPWT-B◊◊ systems consistently presented alarms when there were obvious blockage conditions. NPWT-C◊◊◊ systems were not capable of doing so.

◊ ACTIV.A.C™ Therapy System, ◊◊ V.A.C.ULTA™ Therapy System (KCI, now part of 3M Company, San Antonio, TX); ◊◊◊ Cardinal Health™ NPWT Ally™ Therapy System (Cardinal Health, Waukegan, IL)

1. Cutting, K.F., White, R.J. (2002). Maceration of the skin and wound bed. 1: Its nature and causes. Journal of Wound Care, 11(7), 275-278.
2. Wolfson, J.S., Sober, A.J., Rubin, A.H. (1983). Dermatologic manifestations of infection in the compromised host. Annual Review of Medicine, 34, 205-217.

Important Notice: The contents of the website such as text, graphics, images, and other materials contained on the website ("Content") are for informational purposes only. The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. The content is not intended to substitute manufacturer instructions. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or product usage. Refer to the Legal Notice for express terms of use.