Noise Produced by Neonatal Ventilators Inside and Outside of the Incubators

Abstract

Background: Insufficient data are available about the noise produced by modern neonatal ventilators. We aimed to measure their noise under different ventilatory modes and parameters.

Methods: This was a bench study measuring the noise produced by 9 neonatal ventilators set in conventional or high-frequency oscillatory ventilation (HFOV), nasal mask-delivered CPAP with variable- or continuous-flow configuration, or bi-level positive airway pressure (considered as noninvasive ventilation [NIV]). Conventional ventilation and HFOV were tested in 2 distinct settings with moderate or higher parameters. Sound measurements were performed inside and outside an incubator mimicking the clinical setting and using a high-end meter meeting the international ISO 226:2003 standard.

Results: Four ventilators remained below the internationally recommended safety threshold but only for measurements outside the incubator. Conventional ventilation (49.1 [3.4] dBA) and HFOV (56.3 [5.2] dBA) were the least and most noisy respiratory support technique, respectively. Noise was greater inside than outside the incubators (P < .0001) and different between the ventilators (P < .0001); better results were achieved by Servo-u and Fabian family devices for conventional ventilation; by fabian HFO for HFOV; and by Servo-u, VN500, and fabian family devices for CPAP and NIV. Noise levels were similar when using moderate or higher parameters in conventional ventilation (P = .81) and in HFOV (P = .45).

Conclusions: Modern ventilators often produce relevant noise, independent of the respiratory support modality, with acceptable noise levels being measured only outside the incubator. Better results were achieved with Servo-u, VN500, and Fabian family devices.

Keywords: NICU; neonate; respiratory support; safety; sound; ventilation.

Fig. 1.

Noise produced during conventional ventilation. Panel A-B and C-D represent the sound measured with moderate and strong ventilatory parameters, respectively. Panel A and C represent the sound level measured within the incubator (with closed doors), whereas panel B and D show the level measured in the room between the ventilator and the incubator (more measurement details are available in the main text). Ventilators are represented by dots of different colors; short horizontal lines and T-bars represent means and SD (not always visible as superposed to dots). Arrows indicate the maximum noise threshold recommended (more details in the text). Data are compared with one-way analysis of variance, and overall P values are shown.

Fig. 2.

Noise produced during high-frequency oscillatory ventilation. Panel A-B and C-D represent the sound measured with moderate and strong ventilatory parameters, respectively. Panel A and C represent the sound level measured within the incubator (with closed doors), whereas panel B and D show the level measured in the room between the ventilator and the incubator (more measurement details are available in the main text). Ventilators are represented by dots of different colors; short horizontal lines and T-bars represent means and SD (not always visible as superposed to dots). Arrows indicate the maximum noise threshold recommended (more details in the text). Data are compared with one-way analysis of variance, and overall P values are shown.

Fig. 3.

Noise produced during nasal mask–delivered respiratory support. Panel A-B and C-D represent the sound measured with CPAP and NIV, respectively. Panel A and C represent the sound level measured within the incubator (with closed doors), whereas panel B and D show the level measured in the room between the ventilator and the incubator (more measurement details are available in the main text). Ventilators are represented by dots of different colors; short horizontal lines and T-bars represent means and SD (not always visible as superposed to dots). For the experiments on CPAP, fabian HFO and EVO ventilators were tested both in the continuous- and variable-flow (VF) configurations (this latter is indicated as VF); experiments on NIV were all performed in VF configuration. Arrows indicate the maximum noise threshold recommended (more details in the text). Data are compared with one-way analysis of variance, and overall P values are shown. IF = Infant Flow.