The method for assessment of blood penetration and splash re
In the current outbreak of COVID-19, healthcare facilities are hit by a shortage of supply of Personal Protective Equipments (PPE) owing to extensive local and global demands and restrictions on their import or export. To circumvent this, trials with several indigenous materials suitable to qualify for PPEs and sterilisation techniques for their reuse are being carried out. Prior to their commercialisation or reuse,it is imperative to evaluate the resistance of the PPE-fabrics against penetration of synthetic blood under applied pressure in the range of 40 - 300 mmHg as per test standards. Generally, two types of tests are recommended, namely, the Penetration Test and Splash Resistance Test, the former being more stringent.
While the nal certication of PPEs is carried out by authorised agencies, a rst impression quick estimate of the choice of fabric can be made by using a simple laboratory set up. This study describes set ups developed in the laboratory to carry out these tests. Evaluation of the fabrics, post-gamma irradiation, was also carried out. Microscopic examinations were performed to investigate radiation induced structural changes in fabrics showing degraded performance. The developed set ups are useful for selection of fabrics and to assess the feasibility of reuse of PPEs, which is the need of the hour in this pandemic situation.
This study includes, development of test set-up with existing laboratory equipments to evaluate performances of 11 PPE-fabrics against penetration of Synthetic Blood Equivalent (SB) at various pressures ranging from 40-300 mm Hg applied uid pressure, before and after radiation sterilization (30 kGy, gamma radiation). Of the 11 fabrics, three were subjected to splash resistance test. As a mechanistic approach, radiation induced structural changes in the fabrics were examined under uorescence and bright eld microscope.
Limited commercial information about composition of the material used in these fabrics was available to us; the maximum fraction of most fabrics is Polyethylene/Polystyrene/Polypropylene. All the fabrics were non-woven type with multiple internal layers and hot-spot press patterns. However, fractions and densities of Polyethylene/Polystyrene/Polypropylene were not same in all fabrics. Some samples of fabrics irradiated using gamma radiation to a dose of 30 kGy were also received to study the effect of gamma sterilisation on the PPE material.
Simulation of Test Set-up for SBPRT:
We have put together a working set-up with existing laboratory instruments while following the guidelines of ISO 16603 ASTM F1670 and JIST 8060 and 8122 with minor modications without compromising on physical parameters of the test standards. The set-up was built with a conventional biological media ltration assembly, as shown in gure -1. It included two vented cylindrical chambers, which could be sealed airtight to sustain planned pressure levels. These two chambers were connected at the middle region of the assembly (which was designed to hold the lter) through a gauge. The circular piece of fabric, of diameter ~ 5 cm of the test material was placed over this lter holder. The upper surface of the fabric was layered with 20 ml of SB and this chamber was connected with a pressure unit of the sphygmomanometer to create and measure air pressure in the chamber. It was ensured that uid column height of SB was very small (~1cm) so that its gravitation pressure is negligible compared to the applied pressure. SB was prepared in the lab, having physical attributes similar to Synthetic blood (mixture of polysaccharide, buffer and dye, without preservative). The whole set-up was kept in a 2.5-litre beaker to support it and collect the dripping uid.
Simulation of Test Set-up for Splash Resistance Test:
This test set-up comprised of a circular fabric holder and an injector placed at a distance of 30 cm as shown in gure-2. The fabric holder was mounted on a lead block for stability and placed in a beaker to collect the dripping liquid. The injector was placed at an appropriate height with the help of a height adjustable stand. In one run, 8 ml of SB uid was injected on the fabric sample and the penetrated uid was detected on the other side of the fabric.
Detection of Synthetic Blood Penetrating through the Fabric For both the above-mentioned tests, the penetrated SB was detected at 3 levels; 1) visual detection, 2) detection by absorbent paper - after applying the planned uid pressure, absorbent paper was swiped on to the downstream surface, SB spot created if any, was examined visually and 3) detection by magnifying lens - third level of detection was carried out with magnifying hand lens (for both penetrated droplets and spots created on absorbent paper).
Microscopic Examinations of Radiation Induced Structural Changes in Fabrics:
Fabrics were cut into pieces of 2 cm x1 cm dimensions, sandwiched between the glass slide and a cover glass and ends were sealed with rubber cement (gure-3) to prepare them for examination under a microscope. Total 6 samples were observed and analysed, 3 before and 3 after radiation sterilization (30 kGy). Structural changes/examination of voids, were carried out at 100X and 400X magnications.