key: cord-0790595-xxynwk2t authors: Davis, J. W.; Pillow, J. J.; Cooper, M.; Dahl, M. J. title: Electrostatic filters to reduce COVID-19 spread in bubble CPAP: an in vitro study of safety and efficacy. date: 2020-09-25 journal: nan DOI: 10.1101/2020.09.23.20200485 sha: 9915118041b2cee562478d0c6d7d7b230bd9fba8 doc_id: 790595 cord_uid: xxynwk2t 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 cmH2O) on three occasions for each configuration. Filter failure was defined as pressure >9 cmH20 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. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. . https://doi.org/10.1101/2020.09.23.20200485 doi: medRxiv preprint SARS-CoV-2 originated in Wuhan, China, in November 2020 [1] . We hypothesised that an electrostatic filter placed in the humidified bias flow would become 66 moisture saturated, resulting in instability in pressure transmission during non-invasive 67 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. placed at one of two points in the breathing circuit: on the CPAP probe immediately before the 88 exit of the bias flow into the water column (pre-generator; Figure 1B ) or at the bias flow exit 89 point, normally used as the water inlet (post-generator; Figure 1C ). A new filter was used for 90 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The frequency oscillations, unique to bubble CPAP, were assessed by transforming the mean 107 pressure time series recording into the frequency domain using power spectral analysis. The 108 mean frequency at the maximum power signal of the three circuit configurations was compared 109 using a two-way repeated-measures ANOVA with Holm-Sidak posthoc correction. Filter weight 110 and water volume in the circuit and overflow were compared by an unpaired Student t-test and 111 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. . https://doi.org/10.1101/2020.09.23.20200485 doi: medRxiv preprint 7 Filter weights before and after use are reported in Table 1 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. . https://doi.org/10.1101/2020.09.23.20200485 doi: medRxiv preprint A B C . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. . https://doi.org/10.1101/2020.09.23.20200485 doi: medRxiv preprint Filter dry weight (g) -8.8 ± 0.1 8.9 ± 0.1 Filter weight (g) -11.9 ± 0.2 † 10.8 ± 0.1 † § Water removed from circuit (mL) 4.0 (3.0) 2.5 (3.5) 2.0 (1.5) Water removed from overflow (mL) 0 (10) 1 (6) 160 (20) * Median (range); † p <0.05 compared to dry weight (baseline) for same filter position; § p<0.05 compared to pre-generator at end study; * p< 0.05 compared to control and pregenerator; . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 25, 2020. . https://doi.org/10.1101/2020.09.23.20200485 doi: medRxiv preprint Perinatal aspects 237 on the covid-19 pandemic: a practical resource for perinatal-neonatal specialists Epidemiology, Pathogenesis, and 240 Control of COVID-19 COVID-19 in a 242 26-week preterm neonate CoV-2 in 33 Neonates Born to Mothers With COVID-19 in Wuhan, China COVID-19 in Children, Pregnancy and Neonates: A Review of 247 Epidemiologic and Clinical Features Respiratory support for infants with bronchiolitis, a narrative 249 review of the literature Bubble continuous positive 251 airway pressure enhances lung volume and gas exchange in preterm lambs Bubble CPAP: is the noise important? 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