Effect of Filters on the Noise Generated by Continuous Positive Airway Pressure Delivered via a Helmet.
BACKGROUND
One of the problems that the delivery of continuous positive airway pressure (CPAP) via a helmet poses is the generation of noise. The objective of our study was to assess the effect that the use of filter has on sound pressure levels generated by the delivery of positive airway pressure at different gas flow rates.


METHODS
Sound pressure levels generated by neonatal helmet CPAP delivery were measured at different gas flows (20, 30, and 40 l/min) with and without a breathing filter. Noise intensity was measured by installing microphones in the inner ear of dummy heads wearing helmets.


RESULTS
The sound pressure level increased by 38% at a gas flow of 40 l/min, as compared to a gas flow of 20 l/min {74 dBA [interquartile range (IQR) 2,2] vs 52 dBA (IQR 5,9), respectively}. Using the breathing filter as a diffuser has a variety of effects on sound pressure levels according to the gas flow rate.


CONCLUSIONS
The intensity of the noise generated by helmet delivery of positive airway pressure depends on the type of helmet used, gas flow, and use or not of a diffuser filter. Breathing filters with gas flows over 30 l/min might not be recommended since they would not attenuate but will rather amplify sound pressure.
Acoustic Engineering Laboratory, CASEM, University of Cádiz, Cádiz, Spain.
Ricardo
R
Hernández-Molina
Acoustic Engineering Laboratory, CASEM, University of Cádiz, Cádiz, Spain.
Francisco
F
Fernández-Zacarías
Neonatal Unit, Puerta del Mar University Hospital, Cádiz, Spain.
Isabel
I
Benavente-Fernández
Research Unit, Puerta del Mar University Hospital, Cádiz, Spain.
Gema
G
Jiménez-Gómez
Neonatal Unit, Puerta del Mar University Hospital, Cádiz, Spain.
Simón
S
Lubián-López
D045422:Continuous Positive Airway Pressure / Q000009:adverse effects* / Q000379:methods*; D004867:Equipment Design; D006260:Head Protective Devices; D006801:Humans; D007231:Infant, Newborn; D009622:Noise / Q000009:adverse effects* / Q000517:prevention & control*