The short answer
This page helps readers prepare for negative-pressure wound therapy alarms, dressings, power, mobility, and after-hours support. It cannot set a personal emergency threshold or replace an action plan.
The goal is to prepare for negative-pressure wound therapy alarms, dressings, power, mobility, and after-hours support.
Ask which alarms you may troubleshoot and which require a call.
Keep the dressing seal and tubing arranged as taught.
Know how long the device may safely be off under the written plan.
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What a wound vac actually is
This page is for people going home after cancer surgery with a wound vac, and for the family helping them. A wound vac is a pump that applies gentle suction to a wound through a sealed dressing. Its formal name is negative pressure wound therapy, shortened to NPWT. You may also hear vacuum-assisted closure, or VAC.
An AHRQ technology assessment quotes the definition used by the Centers for Medicare and Medicaid Services: "the application of subatmospheric pressure to a wound to remove exudate and debris, via an integrated system consisting of a suction pump, separate exudate collection chamber, and dressing, over specific wounds." Exudate is the fluid a wound weeps.
Four parts make up the system. A foam or gauze dressing sits in the wound. A clear adhesive film seals over it and onto the surrounding skin. Tubing runs from the dressing to a pump. A canister catches what comes out.
The seal is not packaging. It is the therapy. Without an airtight seal there is no negative pressure.
Get help now: bleeding is the emergency
Call 911 for bright red blood filling the tubing or canister, or blood soaking through the dressing. Do not drive yourself. Then follow the written bleeding instructions your wound team gave you. The exact steps belong to your device and your wound team, so use theirs. If you were never given any written instructions, ask for them today.
This is not a remote risk. FDA lists "uncontrolled bleeding" among the risks to health for these devices, and says labeling should address "bleeding and hemorrhage." The AHRQ report cites FDA data of "174 reports of injury and 12 deaths that have occurred since 2007." It notes that infection was the most common adverse event and bleeding the most severe.
Call your wound team or surgeon right away, at any hour, for:
- A temperature of 100.4°F (38°C) or higher — call immediately. CDC's instruction for people having cancer treatment is to "call your doctor immediately if you have a temperature of 100.4ºF (38ºC) or higher." MedlinePlus uses 100.5°F (38°C) for surgical wounds. Use the lower number. CDC adds that "fever may be the only sign that you have an infection, and an infection during chemotherapy can be life-threatening."
- Drainage that "increases or becomes thick, tan, green, or yellow, or smells bad," which MedlinePlus says indicates pus.
- "More redness, pain, swelling, or bleeding at the wound site," in MedlinePlus's wording.
- A wound that "is larger or deeper, or it looks dried out or dark."
- A seal you cannot restore. If the pump keeps alarming and the dressing will not hold suction, that is a call, not a wait.
- Foam that cannot be accounted for. More on this below.
Ask your team for one specific number: how long the pump can safely be off. Then write it on the device. You do not want to be working that out during a power cut at 2am.
A question worth asking
If you know or suspect cancer remains in or near the wound, raise it with your wound team and get a clear answer about whether a wound vac is right for that wound.
The settings, and why you must not touch them
Suction may be continuous, meaning constant, or intermittent, cycling on and off. Which one you are on, and at what pressure, is set by the wound team for your wound and your device. The settings differ between systems. Those numbers are on your own prescription and in the instructions that came with the pump.
The foam itself is chosen by the wound team too.
Do not change the pressure, do not switch foam types, and do not remove foam unless your wound team has told you to.
The foam count
Retained foam is a known problem. FDA's special-controls guidance says device labeling should address "dressing being retained in wound."
The protection is simple arithmetic. At every dressing change, know how many pieces of foam went in. Confirm the same number comes out. Ask whoever changes the dressing to say the count out loud, and write it down. If a piece is unaccounted for, say so before the new dressing goes on.
Living with the seal
A leak in the seal can set off the pump alarm.
Before you go home, get answers to four things:
- Which alarms you may troubleshoot yourself
- Which alarms mean you call
- How the tubing should be routed
- How long the battery lasts
FDA lists "reflux of waste exudate to wound" among improper-function risks. That is fluid running backwards into the wound. It is why the canister and tubing have to sit where you were shown, not tucked wherever is convenient.
Two device facts worth carrying
FDA lists device incompatibility with MRI, hyperbaric chambers and defibrillation among the risks. Tell any team about to scan you that you have a wound vac. Put it on the same card as your allergies.
Second, ask how often your dressing will be changed. Ask for it in writing, with the name and number of who does it.
What progress looks like
Watch three things and record them.
The canister: how much fluid, and what it looks like. Thick tan, green or yellow fluid that smells bad is pus, and MedlinePlus says to report it.
The wound: it should be getting smaller and shallower, with healthy pink tissue filling in. MedlinePlus names the opposite as a warning sign — a wound that is "larger or deeper, or it looks dried out or dark."
The skin around the seal: the adhesive film covers healthy skin. Report skin that becomes sore or breaks down under the film rather than trying to re-tape around it.
Sources
- FDA — Non-powered Suction Apparatus Device Intended for Negative Pressure Wound Therapy (NPWT): Class II Special Controls Guidance — note that this FDA guidance covers non-powered NPWT devices; most wound vacs used after cancer surgery are powered systems, and the manufacturer's instructions for your exact pump are the document that governs your care.
- AHRQ (NCBI Bookshelf) — Negative Pressure Wound Therapy Technologies for Chronic Wound Care in the Home Setting
- MedlinePlus — Surgical wound care: open
- CDC — Watch Out for Fever (Preventing Infections in Cancer Patients)
Common questions
Can I change the settings or take the foam out?
No, unless the wound team directs you to. The page says not to remove foam or alter pressure settings on your own. Ask them to write down what you are allowed to adjust.
What should I do when the device alarms at home?
Find out in advance which alarms you may troubleshoot and which ones need a call. The page also asks you to keep the dressing seal and tubing arranged as you were taught, since that is often part of what an alarm is about.
How long can the wound vac be switched off?
There is a limit, and your written plan should state it. The page says to know that number before you need it rather than working it out during a power cut.
What should be sorted before I go home with a wound vac?
Which alarms you handle, how the seal and tubing should sit, how long the device can be off, and who to contact after hours. The page also asks for three levels of urgency with the exact phone number for each.
Questions to ask your doctor
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Your next step
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
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Where to get help with this, by name
A hospital social worker or financial navigator is the best first call if you have one. If you do not, these organisations help at no cost to you.
- Patient Advocate Foundation — (800) 532-5274. Case managers take on insurance appeals, denials and medical debt with you. Free.
- TotalAssist (Patient Advocate Foundation's copay programme, merged with the PAN Foundation in 2026) — 866-512-3861. Help with medication copays, coinsurance and deductibles, insurance premiums, and office-visit and administration charges on the day of treatment, across nearly 150 conditions.
- CancerCare — 800-813-HOPE (4673). Oncology social workers, free counselling and support groups. Limited financial help with transport, home care, child care and lodging for people in active treatment who meet their income guidelines — funding is first-come, first-served, so call to ask what is open.
- Triage Cancer — 424-258-4628. Free legal and financial navigation: insurance, employment rights, disability.
- Blood Cancer United (formerly the Leukemia & Lymphoma Society) — (800) 955-4572. Information Specialists answer questions on treatment, insurance and financial problems.
- HealthCare.gov — 1-800-318-2596. For questions about the external review process — the independent review your insurer is required by law to accept.
Your state Department of Insurance regulates insurers and takes consumer complaints. On Medicare, your State Health Insurance Assistance Program (SHIP) gives free one-to-one counselling. If a specific drug is the problem, ask the manufacturer about its patient assistance programme.
Phone numbers checked 31 July 2026. Programmes and eligibility change — if a number has moved, please tell us.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Sources last checked: 2026-08-11 what this meansLast updated: 2026-10-01Next planned review: 2027-01-22
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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