We aimed to determine how the placement and position of an electrostatic filter in a bubble CPAP circuit impacts the magnitude and stability of the delivered pressure in an in vitro model. We hypothesized that progressive moisture saturation of an electrostatic filter placed in humidified bias flow would result in increased circuit pressure. One reason for these recommendations is the possibility of moisture saturation of the electrostatic filter which would increase resistance to airflow, increasing circuit pressure and work of breathing. Manufacturers of electrostatic filters recommend electrostatic filter replacement every 24 h. Electrostatic filters remove viruses from expired gas, offering protection to health care staff and are recommended in international guidelines. ĬPAP generates aerosols and therefore may promote transmission of viral particles. These pressure oscillations (frequency) may improve acute respiratory mechanics compared to constant delivery pressure consequent to recruitment of atelectatic alveoli. The resulting pressure oscillations are transmitted back to the nares and to the lung hence, the bubbling delivers a variable rather than constant pressure. The expiratory limb of the bubble CPAP circuit vents through an underwater seal, creating bubbles. Bubble CPAP is a popular means of providing respiratory support in these infants. CPAP use has extended in recent years to include infants with viral respiratory disease. The need for respiratory support in infants with COVID-19 is uncertain.Ĭontinuous positive airway pressure (CPAP) has been a cornerstone treatment of neonatal respiratory distress syndrome for >40 years. Data on neonatal infection with SARS-CoV-2 are limited. The clinical disease, COVID-19, was declared a global pandemic by WHO in March 2020. SARS-CoV-2 originated in Wuhan, China, in November 2020. The post-generator position may accommodate a filter, but regular pressure monitoring and early replacement are required. Filters are likely to become saturated with water over time. Conclusions: Placement of the filter at the pre-generator position in a bubble CPAP circuit should be avoided due to unstable mean pressure. The filter weight was heavier at end study in the pre- compared to the post-generator position. Mean pressure was higher throughout in the pre-generator position compared to control. 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. ![]() The filter was weighed before and after each experiment. Filter failure was defined as pressure >9 cm H 2O for 60 continuous minutes. Pressure was recorded at the nasal interface for 18 h (6 L/min 7 cm H 2O) on 3 occasions for each configuration. 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. This study aims to determine if including a filter in the bubble CPAP circuit impacts stability of pressure delivery. Electrostatic filters may reduce cross infection. Background: Bubble CPAP may be used in infants with suspected or confirmed COVID-19.
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