The particle separation ability of the D-Fend Pro water trap

The D-Fend™ Pro is a water trap used with the single-width CARESCAPE™ respiratory modules.

Summary

The D-Fend™ Pro is a water trap used with the single-width CARESCAPE™ respiratory modules, see figures 1 and 2. With its special polytetrafluoroethylene (PTFE) membrane, the water trap is designed to protect the modules from moisture, humidity and contaminants, which can harm the gas bench and affect measurement accuracy. A study was conducted by an independent research facility to test the water trap’s particle separation ability, using particles of different sizes. Results showed that the D-Fend Pro water trap separated at least 99.98% of the particles with a particle size as small as 0.15 μm. Bacteria typically has a particle size of 0.5 μm to 5 μm.¹

Figure 1. The D-Fend Pro and D-Fend Pro+ water traps

Introduction

With side-stream respiratory airway gas monitoring, sampled gases are transported from the patient into the gas bench for analysis. However, sometimes there is moisture and contaminants in the sampled gas, and these can cause damage to the gas analysis system and affect the module’s performance. To remove the moisture and contaminants before it enters the system, the sampled gas passes through a water trap.

The D-Fend Pro water trap protects the gas bench and enables seamless operation of the CARESCAPE respiratory module. The gas flow channels in the D-Fend Pro water trap are streamlined to ensure fast rise times of the gas measurements, even at 120 ml/min sample gas flow. In addition, the lower sampling flow rate helps to address problems of moisture and humidity associated with airway gas monitoring. During the measurement, the gas is sampled through the channels, where the filter membrane inhibits humidity, contamination and secretions from passing through the water trap

Figure 3. The inner design of D-Fend Pro water trap’s air channels (grey) and filter membrane (black)

Study Method

Diethylhexyl sebacate (DEHS) particles were pumped through the D-Fend Pro water trap at a constant rate of 100ml/min. The particle proportion was measured both from the inlet and the outlet of the water trap with a particle size analyzer (PMS LAS-X II). The particle measurement range was from 0.15 μm to 2 μm. The membrane’s resistance, E, to permeation of particles with a particle size, d, is defined by the equation:

E(d) = Ci(d) / Co(d)

where Ci(d) and Co(d) are the proportion of particles with size d in the inlet and outlet, respectively. The test was conducted for 10 individual D-Fend Pro water trap units

Study Results

The results of the resistance to permeation of the D-Fend Pro water trap for particles with a size from 0.15 μm to 1 μm are presented in figure 4. The D-Fend Pro’s resistance to permeation was 99.98% for particles with a size from 0.15 μm to 0.3 μm and 99.99% for particles with a size from 0.3 μm to 2 μm.

Figure 4. Results of the D-Fend Pro’s ability to separate particles.

Conclusion

In a test conducted by an independent research facility, the PTFE membrane of the D-Fend Pro water trap inhibited at least 99.98% of particles with a size of 0.15 μm or larger from passing through the water trap. This separation ability exceeds the requirements to separate particles with a size comparable to bacteria and a share of viruses, as bacteria have typically a particle size from 0.5 μm to 5 μm, and viruses from 0.02 μm to 0.25 μm. The study shows that the water trap design helps protect the modules from particles on the sizes of some of the main contaminants found in the sampling system.

References

1. Gillen, Alan L. The Genesis of Germs. New Leaf Publishing Group, 2007.

Study documentation

This paper is based on the following internal GE HealthCare's documentations:

Results of the D-Fend Pro Water Trap’s particle separation ability tests in VNV−REPORT: Kaasumittausmodulin suodattimen erotuskykymittaus. 14.12.2011 (M1243549), and Verification Report for D-Fend Pro Membrane Material Change (DOC1556930 rev 1)

Additional resources

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JB26949XX 12/2023