Sound levels inside incubators and oxygen hoods used with nebulizers and humidifiers

Degree of hearing loss in the infant is related to high-intensity or high-frequency sound (noise). We measured sound levels of 6 models of pneumatic nebulizers and 8 models of humidifiers at various flowrates, FIO2 settings, and water levels, when they were attached to incubators and oxygen hoods; we also evaluated sound levels from 2 models of ultrasonic nebulizers at various output settings. Among the pneumatic nebulizers, the recommended 58-dbA maximum sound level was exceeded by the Aquapak 621, Ohio Deluxe, and Puritan All-Purpose devices. The Bard Parker, Foregger, and Inspiron pneumatic nebulizers' sound levels were 58 dbA or below except during the dry water-level condition. Among the humidifiers, all produced sound levels below the recommended 58-dbA maximum except the Travenol humidifier; the Bennett Cascade, Conchapak, Foregger, and Hudson humidifiers produced mean sound levels in the 43.0- to 43.5-dbA range. Sound levels increased under all conditions when the devices were used with oxygen hoods. The ultrasonic nebulizers produced low sound levels, but the high-frequency ultrasound they also produce may be undesirable for infants; this question requires further investigation.