Table of Contents
Pre-requisites for Vac Dressing
- Thorough debridement
- Adequate hemostasis
Components of Vac Dressing
1. Pump for Negative Pressure:
- A wall suction or a portable suction unit
- A plastic bellows pump is also an option e.g. hemovac, romovac
- Optimum pressure:
- Acute traumatic wounds – negative pressure of 125 mm Hg
- Chronic non healing venous ulcer – negative pressure of 50 mm Hg
- Intermittent negative pressure (cycle of 5 min on and 2 min off phase) is recommended as it generates more blood flow during vacuum “off” phase
- Pressure in VAC dressing gradually reduces over 2 days therefore, dressings should be changed after 48 hr
In a study, 3 closed suction drainage systems were studied – Davol Reliavac 400 Evacuator, Jackson-Pratt Closed Wound Suction Drainage System, and Snyder Hemovac 400. In all three systems, maximal negative pressures (-71 to -175 mm Hg) were generated with the reservoirs empty of fluid. Pressure generation by all drains decreased as the volume of fluid in the reservoir increased.
2. Dressing: Usually changed on 3rd day
a. Porous packing material (interface between vacuum source and wound bed):
- Black (Polyurethane ether, lighter, hydrophobic with a pore size of 400–600 mm): for thoracic and abdominal cavity wounds
- White (Polyvinyl alcohol, dense, hydrophilic with a pore size of 250 mm): for superficial surface wounds
- Gauze dressings are also a cost-effective option
b. Occlusive cover:
- Provides a protective cover over the wound cavity and gauze packing material and remains airtight for its entire dressing period
- Should cover at least 3–5 cm of surrounding healthy tissue to ensure a watertight/airtight seal
3. Connection mechanism: Air tight connection between vacuum unit and dressing unit is important
Mechanism of Action of Negative Pressure Wound Therapy
a. Macrostrain: Visible contraction which occurs when negative pressure is applied
- Draws wound edges together
- Provides direct and complete wound bed contact
- Removes exudate
b. Microstrain: Micro-deformation at cellular level
- Reduces edema
- Promotes granulation tissue formation by facilitating cell migration and proliferation
- Wound is covered with one layer of paraffin gauze
- A sterile polyvinyl-alcohol sponge, slightly smaller in diameter than the wound is then placed over the paraffin gauze
- An evacuation tube is placed above the sponge, after making a few holes at the distal end with scissors
- A second sponge layer then covers the tube, and the whole area is sealed with adhesive drape extending approximately 5 cm beyond the margins of the wound, thus creating an airtight seal
- Proximal end of the tube is connected to a wall-suction container, and the system is then placed under negative pressure at 75–125 mmHg continuously for 1 to 3 days
- A piece of pre-sterilized foam of about 1 cm thickness is cut to the size of the wound and is placed on it
- A perforated drainage tube (e.g. Romovac suction drain tube) is put on it
- Again a piece of foam is placed on the underlying foam and tube.
- The whole foam with tube is covered with a sterile transparent dressing (Opsite)
- The tube is connected to a common suction apparatus with pressure gradient.
- Suction is applied with a negative pressure of 100 to 125 mmHg for 10 mins hourly for 12 consecutive hours. Rest of the time, this drainage tube is connected to the Romovac suction apparatus.
- Perforated end of the Romovac drainage tube is placed on the wound surface and its other end, placed 10 cm away from the wound margin and connected to the bellow
- Sterilized foam is trimmed according to the size and geometry of the wound and placed on top as a cover
- Opsite then coveres the wound and the adjoining healthy skin with an airtight seal
- Romovac bellow is charged to obtain appropriate cyclical negative pressure
- Patients can be taught how to charge the Romovac and their attendants can be advised to charge it every 5–6 hours. A mean pressure of −80 mmHg (range −60 to −120 mm Hg) can be obtained on full charging. The pressure was measured by a pressure-measuring device
- In this method, dressing was changed every week, or earlier if there is a soakage/leakage
- Agarwal P, Kukrele R, Sharma D. Vacuum assisted closure (VAC)/negative pressure wound therapy (NPWT) for difficult wounds: A review. J Clin Orthop Trauma. 2019 Sep-Oct;10(5):845-848. doi: 10.1016/j.jcot.2019.06.015. Epub 2019 Jun 20. PMID: 31528055; PMCID: PMC6739293.
- Zurovcik, Danielle R., Gita N. Mody, Robert Riviello, and Alex Slocum. “Simplified Negative Pressure Wound Therapy Device for Application in Low-Resource Settings.” Journal of Orthopaedic
Trauma 29 (October): S33–S36. doi:10.1097/bot.0000000000000410.
- Shalom A, Eran H, Westreich M, Friedman T. Our experience with a “homemade” vacuum-assisted closure system. Isr Med Assoc J. 2008 Aug-Sep;10(8-9):613-6. PMID: 18847164.
- A. Anandi, Captain S. Nedunchezhian,R. Karthikeyan. A study of vacuum assisted closure in chronic non-healing diabetic ulcers. IAIM, 2020; 7(3): 47-52.
He is the section editor of Orthopedics in Epomedicine. He searches for and share simpler ways to make complicated medical topics simple. He also loves writing poetry, listening and playing music.