Electrostatic filters to reduce COVID-19 spread in bubble CPAP: an in vitro study of safety and efficacy

  1. Jonathan W Davis
  2. J Jane Pillow
  3. Matt N Cooper
  4. Mar Janna Dahl

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Abstract

Background

Bubble CPAP may be used in infants with suspected or confirmed COVID-19. Electrostatic filters may reduce cross-infection. This study aims to determine if including a filter in the bubble CPAP circuit impacts stability of pressure delivery.

Methods

A new electrostatic filter was placed before (pre) or after (post) the bubble CPAP generator, or with no filter (control) in an in vitro study. Pressure was recorded at the nasal interface for 18 h (6 L/min; 7 cmH 2 O) on three occasions for each configuration. Filter failure was defined as pressure >9 cmH 2 0 for 60 continuous minutes. The filter was weighed before and after each experiment.

Results

Mean (SD) time to reach the fail-point was 257 (116) min and 525 (566) min for filter placement pre- and post-CPAP generator, respectively. Mean pressure was higher throughout in the pre-generator position compared to control. The filter weight was heavier at study end in the pre-compared to the post-generator position.

Conclusions

Placement of the filter at the pre-generator position in a bubble CPAP circuit should be avoided due to unstable mean pressure. Filters are likely to become saturated with water over time. The post-generator position may accommodate a filter, but regular pressure monitoring and early replacement are required.

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  1. ScreenIT

    SciScore for 10.1101/2020.09.23.20200485: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    P-values were assessed at a 0.05 significance level by SigmaPlot (Systat, Inc., Santa Clara, CA)
    SigmaPlot
    suggested: (SigmaPlot, RRID:SCR_003210)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Although the in-vitro nature of this study may be considered a limitation, such models are used widely for describing the performance of respiratory support devices, including neonatal respiratory support modalities [15, 17, 19-22]. Our in-vitro experimental set-up was a sealed circuit, measuring the stability of pressure without considering leak. Clinically, bubble CPAP pressure delivery is determined by the bias flow and degree of leak at the nares, as well as the degree of mouth closure [15]. Many neonatal units aim to minimise leak by using chin straps (to keep the mouth closed) and colloid dressings over the nares that not only reduce nasal trauma but also markedly reduce leak at the nasal interface. The instability of the delivered pressure over time should concern clinicians considering the use of such filters when treating premature infants with bubble CPAP, particularly when positioning the filter immediately before the bubble CPAP generator chamber. The transmission of SARS-CoV-2 to health-care workers is a major concern in the current pandemic [23]. Neonates are at risk of COVID-19, although evidence of infection is sparse. Newborns of mothers with confirmed or suspected COVID-19 require precautions as recommended in recent published international guidelines [24]. Filters reduced the expired viral load from ventilator circuits when tested in previous pandemics [25, 26] and are recommended by several international societies [27, 28]. However, it is essential to cons...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2020.09.23.20200485v1 on medRxiv
  3. Version published to 10.1159/000512146