A number of options exist when choosing bed pads for incontinence management. Consideration for patient comfort is a key criteria when comparing such options. One such aspect of patient comfort relates to breathability and the bed pad’s function in keeping the patient cool and dry. It is therefore desirable to understand the relationship between bed pad construction and breathability and if certain bed pads outperform others in this regard. Pressure mapping tools are also important when determining relative performance of the variety of options available in the market today. This paper sheds light on all of these aspects in order for the end user to make an informed decision.
Breathability is often considered to be related to moisture vapor transmission which describes a material’s ability to allow water vapor to pass through it. A quantitative assessment of this characteristic can be made with reference to the moisture vapour transmission rate (MVTR) which is a measure of the passage of water vapor through a substance. The higher the MVTR the more “breathable” the fabric.
There are various methods to measure moisture vapour transmission rate (MVTR) which employ gravimetric techniques to measure the gain or loss of moisture by mass (g/m²/day). Test Method ASTM E96 calculates the amount of water vapor that can cross one square meter of fabric in 24 hours. (Figure 1)
Using this test method, the graph below compares the relative MVTR levels between disposable and reusable bed pads . A material with higher levels of MVTR is often considered to be more breathable (Figure 2), with fabrics having a value of > 10,000 g/m2/24hrs possessing a good level of breathability.
Although reusable bed pads have over double the MVTR than disposables, neither option noted above is considered breathable.
A bed pad is functionally designed to transfer moisture into the face/soaker combination and move moisture away from the body. It then preferentially transfers moisture laterally while the barrier membrane layer remains impervious for linen protection. The primary purpose of the bed pad is to prevent moisture from passing through it. Therefore a bed pad’s moisture permeability is not the best indicator of functional performance when it comes to patient care or comfort.
In the case of reusable bed pads, it is appropriate to consider the effect of the required, repeated laundering on moisture vapor transfer. All pad configurations exhibit reduced MVTR after laundering. Detergent and laundry products contribute to obstructing microscopic pores in the barrier membrane while pad shrinkage after laundering may also close or contract these barrier pores and hence reduce MVTR.
MVTR, which is a measure of moisture permeability, should not be confused with air permeability which is a measure of the transmission of air through a fabric. The standardized test method CAN CGSB-4.2 No 36 measures air permeability in terms of the volume (cm³) of air passing through 1cm² of fabric per second with an average value obtained from 10 measurements. Considering that all bed pads are specifically designed to provide a liquid impermeable barrier in order to keep bed linens dry, they are by nature not considered air permeable. Functional testing demonstrates that airflow through both disposable and reusable bed pads are equivalently negligible and below the detection limit of less than 0.30 cm³/ cm².
Pressure mapping is also a way to assess comfort by determining the therapeutic interface between the patient and the bed surface. A comparative test on a variety of bed pad designs and styles, to measure the influence on pressure points, indicates that only minor differences exist across all options. The properties of a therapeutic mattress are not adversely effected by adding any type of single bed pad.
All bed pads have comparable performance in moisture permeability, air permeability and pressure mapping results; however claims that certain bed pad construction technologies are preferred for patient comfort have not been substantiated by independent testing with these standardized test methods.
Technical Manager, Textile Development