Neonatal Noise Exposure and Noise Reduction During Transport

Inter-hospital transport of sick neonates for specialist care is often necessary, but older studies suggest it may expose them to high levels of noise that may cause distress, autonomic instability and even noise induced hearing loss (NIHL). There have been advances in transport equipment standards, but little effort to address this issue. There is paucity of data on the effects of noise levels experienced by neonates undergoing inter-hospital nor on the effects it may have on infant stability or behaviour. MRI scans, which are known to generate potentially hazardous noise levels, are not performed without conventional noise protection headphones, and newer active noise cancelling equipment that is available may provide additional protection. Standard neonatal transport clinical care does not include noise protection as such for patients during road transfers, and minimal protection is provided for air transport.

This research quantified the noise levels experienced by neonates undergoing interhospital transport by both air and ground ambulance, with the national neonatal transport service. Baseline noise levels were obtained to ascertain feasibility of research equipment prior to demonstrating the physiological effects of noise among neonates during transport in an observational patient cohort. The research subsequently evaluated the effect of the application of noise protective equipment during neonatal interhospital ground and air transport by demonstrating differences in noise exposure and the effect on the neonatal heart rate, oxygen saturations and behavioural responses. A convenience sample of neonates who underwent clinically indicated inter-hospital transfer was recruited following parental consent. A multichannel noise meter recorded noise levels at the infant external auditory meatus (EAM), within the incubator and in the ambulance cabin concurrently. Simultaneous recording of infant heart and oxygen saturations was obtained and video footage was taken for behavioural analysis by 4 separate examiners. Demographic and routine transport monitoring data was documented. The patient observational study to determine the extent of noise exposure and its physiological effects during standard neonatal ground transport care i.e. without noise protection was followed by a sequence if intervention studies which included a crossover design that compared the application of noise protective devices with standard care. The noise protective devices that was used in the interventional patient studies were MRI grade noise protective earmuffs and an electronic active noise cancelling headphones. Two patient studies are still on-going due to paucity of suitable cases during the research period. One is randomized controlled trial of stable infants undergoing elective repatriation transfers was carried out to compare standard care with active noise cancelling headphones. The other is an observational study to compare the effectiveness of noise protective earmuffs versus active noise cancellation headphones in single journey neonatal air transfers.

Noise levels was measured underneath the noise protective equipment near the patients ear along with concurrent heart rate, oxygen saturation and infant behaviour recording. All the data was downloaded to a password protected computer and analysed using specialist software for analysis. Statistical analysis was performed using SPSS version 26.

This research demonstrated the quantity of neonatal noise level exposure in the NICU, but more pertinently during neonatal transport. Results of noise levels in baseline studies in NICU, ground ambulance transport and air transport can reach above 80 decibel-A and occasionally stretch near to and above 100 decibel-A. This surpasses international recommended limits of which should not exceed 60 decibel-A during transport. The degree of noise reduction offered by the selected noise protective modalities evaluated, indicate the need for foreseeable improvement in delivery of care to the vulnerable neonate undergoing transport. While various analysis throughout the research demonstrated changes in physiology and behaviour moreover, with the application of noise protection; there is still huge variability within small population groups that was studied.