KOSA Medical · Application Engineering
Underpad Absorbency & Size Selection Guide
A procurement-focused guide to disposable underpads and bed protection sheets — how to read absorbency claims, match size to use case, choose backing and core construction, and set a defensible change-frequency policy.
Key Takeaways
- Specify absorbency as measured total capacity and retention under load, not as a marketing tier.
- Match size to use case: chair/bed protection, procedure underpad and full-bed formats are not interchangeable.
- Backing choice drives slip resistance and breathability — a common complaint source in long-term care.
- Evaluate retention under pressure, not just uptake speed; rewet is what causes linen changes.
- Set change frequency from observed saturation, then convert to a per-patient-day consumption figure.
What a disposable underpad is — and what actually matters
A disposable underpad is a layered absorbent sheet — typically a soft nonwoven topsheet, a fluff-pulp (often with superabsorbent polymer) core and a waterproof backing — used to protect bedding, chairs and procedure surfaces from fluids.
For procurement, the two numbers that matter are total absorbent capacity and retention under load. Uptake speed gets attention because it is visible; retention is what actually determines whether linen stays dry. Specify both, and ask for the test method behind the claim so bids are comparable.
Reading absorbency claims
| Claim type | What it tells you | Limitation |
|---|---|---|
| Total absorbent capacity | Overall fluid volume held | Does not describe behaviour under pressure |
| Retention under load | Fluid held when body weight is applied | More predictive of real rewet performance |
| Acquisition / strike-through time | How fast surface dries | Fast uptake alone does not prevent rewet |
| Rewet value | Fluid returning to surface under load | Closely tied to skin-maceration risk |
Request the test method and conditions with any absorbency figure. Capacity measured freely versus under load can differ substantially, and unqualified claims make tenders impossible to compare.
Size and format selection
| Format | Typical placement | Best for |
|---|---|---|
| Chair / small protector | Seating, wheelchairs | Day use, outpatient, short procedures |
| Standard bed protector | Centre of bed, under patient torso | General ward and long-term care |
| Full-bed / large format | Whole mattress coverage | High-output cases, bariatric, night use |
| Procedure underpad | Under sterile field | Procedure rooms, minor surgery |
Backing and construction
- Polyethylene film backing: strongest fluid barrier; check slip resistance and breathability.
- Non-slip / textured backing: reduces pad migration — a frequent complaint in long-term care.
- Breathable backsheets: improve comfort on long dwell; verify barrier integrity for your output level.
- Core construction: fluff pulp alone suits lower output; SAP-blended cores hold more under compression.
- Sealed vs cut edges: sealed edges reduce core leakage at the perimeter.
Procurement checklist
1. What is the measured capacity and the test method?
Insist on both, or bids are not comparable.
2. Is retention under load stated?
This predicts rewet better than uptake speed.
3. Which size formats do you actually need?
Standardise on the smallest set that covers ward, chair and procedure use.
4. Does the backing stay put?
Non-slip backing reduces pad migration and staff repositioning time.
5. Have you converted trials into per-patient-day consumption?
Set change frequency from observed saturation, then price the full consumption, not the unit.
How we evaluated these recommendations
Guidance reflects KOSA Medical's disposable hygiene range and common procurement criteria in hospital, clinic and long-term-care settings, structured around measurable absorbency, format fit and total consumption cost. Final selection should be confirmed against your own process conditions and applicable standards.
Building an underpad specification?
Share your required sizes, absorbency targets and monthly volumes — KOSA Medical will return a matched specification and quote.
Request a quoteRelated: Technical bulletins · Product range · Medical disposable guide · Gown material guide
Frequently asked questions
How should underpad absorbency be specified?
Specify measured total absorbent capacity together with retention under load, and require the test method and conditions with any claim. Capacity measured freely versus under load can differ substantially, and unqualified claims make tenders impossible to compare.
Which predicts real performance better: uptake speed or retention?
Retention under load. Fast strike-through is visible and often marketed, but retention is what determines whether fluid returns to the surface under body weight and whether linen stays dry.
What backing should be chosen for long-term care?
A non-slip or textured backing is usually preferred because pad migration is a frequent complaint and increases staff repositioning time. Where long dwell comfort matters, consider breathable backsheets but verify barrier integrity for the expected output level.
What is the difference between fluff pulp and SAP-blended cores?
Fluff pulp alone suits lower-output applications, while cores blended with superabsorbent polymer hold more fluid under compression, which improves retention under load.
How should change frequency be set?
Start from observed saturation in a trial rather than a fixed schedule, then convert the resulting pattern into a per-patient-day consumption figure so that total cost, not unit price, drives the purchasing decision.