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Re: Noise levels during neonatal helmet CPAP

High noise levels during nCPAP reported by Karam et al. demonstrate the presence of a continuous exposition to audio trauma by the developing ears of preterm infants.1 These levels were directly related to the flow through the circuits, but not to the pressure generated, neither to the type of nCPAP device used. To improve the patient-ventilator interface we developed a new device (neonatal helmet CPAP) to administer CPAP in preterm infants.2 In a short- term physiological study, neonatal helmet CPAP appeared to be a feasible method of supporting the breathing of preterm infants with a better tolerability compared with conventional nCPAP.2 Furthermore, this new device allows the delivery of accurate nitric oxide levels avoiding NO2 accumulation.3 In a bench study, we measured the noise levels generated by the neonatal helmet CPAP. Measurements were performed on the C scale (using a C- weighting filter). The phonometer (MK 5350, Mitek Industries, Inc, Phoenix, AZ, USA) was positioned in the pressure chamber of the device corresponding to the ear of the neonate (“ear zone”). The noise levels were detected at different flow rates (8, 10 and 12 l/min), maintaining the level of CPAP constant at 5 cmH2O. Measurements for each flow rate lasted 15 minutes; the noise level was calculated every 20 seconds. All measurements were obtained in the Neonatal Intensive Care Unit (NICU) in the afternoon (3.00-5-00 p.m.). In the neonatal helmet CPAP system, the mean (SD) noise levels were significantly higher in comparison with those measured in the NICU (60.4+0.7 dB) and within the baby compartment of the incubator (62.3+0.5 dB). Noise levels significantly changed with increasing flow rates in the system: 8 l/min (69.9+0.5 dB); 10 l/min (71.5+0.2 dB); 12 l/min (73.5+0.3 dB). (Figure)

In agreement with Karam et al.,1 our results show that the CPAP systems produce potentially dangerous noise levels for the developing ear of a preterm infant. They are directly related to the flow rate through the system, instead of the pressure level. The new CPAP devices need to take into account this crucial aspect.

REFERENCES

1. Karam O, Donatiello C, Van Lancker E, Chritin V, Pfister RE, Rimensberger PC. Noise levels during nCPAP are flow-dependent but not device-dependent. Arch Dis Child Fetal Neonatal Ed 2008;93:F132-F134.

2. Trevisanuto D, Grazzina N, Doglioni N, Marzari F, Zanardo V. A new device for administration of continuous positive airway pressure in preterm infants: comparison with a standard nasal CPAP continuous positive airway pressure system. Intensive Care Med. 2005;31:859-64.