Abstract
BackgroundIn common with the majority of personal protective equipment and healthcare products, the ability for long-lasting insecticidal nets (LLINs) to remain in good physical condition during use is a key factor governing fitness for purpose and serviceability. The inherent ability of a product to resist physical deterioration should be known in advance of it being used to ensure it has maximum value to both the end-user and procurer. The objective of this study was to develop a single performance metric of resistance to damage (RD) that can be applied to any LLIN product prior to distribution.MethodsAlgorithms to calculate RD values were developed based on consideration of both human factors and laboratory testing data. Quantitative reference forces applied to LLINs by users during normal use were determined so that aspirational performance levels could be established. The ability of LLINs to resist mechanical damage was assessed based on a new suite of textile tests, reflecting actual mechanisms of physical deterioration during normal household use. These tests quantified the snag strength, bursting strength, abrasion resistance and resistance to hole enlargement. Sixteen different unused LLINs were included in the analysis. The calculated RD values for all LLINs and the corresponding physical integrity data for the same nets retrieved from the field (up to 3 years of use) were then compared.ResultsOn a RD scale of 0 (lowest resistance) – 100 (highest resistance), only six of the sixteen LLINs achieved an RD value above 50. No current LLIN achieved the aspirational level of resistance to damage (RD = 100), suggesting that product innovation is urgently required to increase the RD of LLINs. LLINs with higher RD values were associated with lower hole damage (PHI) in the field when adjusted for normal use conditions.ConclusionsThe RD value of any LLIN product can be determined prior to distribution based on the developed algorithms and laboratory textile testing data. Generally, LLINs need to achieve higher RD values to improve their ability to resist hole formation during normal use. Innovation in LLIN product design focused on the textile material should be actively encouraged and is urgently needed to close the performance gap.
Highlights
In common with the majority of personal protective equipment and healthcare products, the ability for long-lasting insecticidal nets (LLINs) to remain in good physical condition during use is a key factor governing fitness for purpose and serviceability
Forms of mechanical damage are recurrent across different geographical settings and are found in all knitted LLINs regardless of whether they are made of polyester (PET) or polyethylene (PE) [10, 11]
The maximum explosive force a male of 21–60 years weighing an average of 80 kg can exert in an overhand pulling motion is reported to be 308 N [17] and it is unlikely that a LLIN with snag strength of > 300 N would be readily damaged by snagging during normal use
Summary
In common with the majority of personal protective equipment and healthcare products, the ability for long-lasting insecticidal nets (LLINs) to remain in good physical condition during use is a key factor governing fitness for purpose and serviceability. In terms of reliability engineering, long-lasting insecticidal nets (LLINs) should be capable of functioning under field conditions for 3 or more years, and resist failure during normal use by remaining in good physical condition [1]. Mechanical damage is the primary contributor to LLIN deterioration in normal use, both in terms of hole frequency and area. Of these mechanical damage mechanisms, snagging is responsible for the initiation of the largest proportion of holes. Tearing, abrasion and seam failure are responsible for a large proportion of the hole area, and their underlying mechanisms of damage would be practically difficult to avoid during normal use of a LLIN product. Forms of mechanical damage are recurrent across different geographical settings and are found in all knitted LLINs regardless of whether they are made of polyester (PET) or polyethylene (PE) [10, 11]
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