Delivering on the Potential of Intermittent NPWT and Lower Negative Pressures

Background

Despite  evidence in favor of intermittent and lower negative pressures, continuous and higher negative pressures have remained predominate.   NPWT practices have not evolved to take advantage of the full therapeutic potential described in research, old and new. 

Aims    
Review research spanning 20 years relevant to intermittent NPWT and/or the use of lower negative pressures.  The resulting research is intended not only to document the history of these aspects of NPWT development, but also to improve current practices immediately and help frame important new studies.

Methods    
Clinical and animal wound model studies of NPWT are summarized, with an emphasis on NPWT mechanisms of action, patient factors, and system factors that have influenced the evolution of care.

Results
Results were obtained in the late 1980s with the first closed NPWT system using pressures in the range of -60 to -80 mmHg.

The 1990s showed intermittent therapy produced 63.5% more granulation tissue than continuous therapy.  Pain issues and system limitations thwarted adoption of intermittent therapy at that time. 

Studies of microvascular blood flow in porcine models using laser Doppler have highlighted the need to carefully select negative pressures to match tissue type  and location, while minimizing hypoperfusion at the wound edge and potential ischemia associated with higher negative pressures.  Intermittent NPWT results in better and more effective overall blood flow than continuous therapy.

No statistically significant differences were seen in wound volume reduction between -125, -75 and -50 mmHg.  Additional porcine studies have been conducted comparing gauze and open cell foam, with respect to blood flow, pressure transduction, and wound contraction.  Similar responses and effectiveness were found. 

Conclusions
Benefits to wound healing have long been associated with intermittent NPWT. Pain and system issues discouraged use of intermittent therapy.  Today, the benefits are much better understood and can actually be put into practice using customizable NPWT systems and techniques.  Lower negative pressure levels, less than recommended in recent years, in addition to offering pain reduction and less tissue disruption, have now been shown to offer additional benefits, especially in softer tissue, and in avoiding potential ischemia at the wound edge.

There is a large, unmet need to educate caregivers on the optimal use of NPWT.