Acoustic Noise Analysis and Management in Intensive Care Units

The initial aim of this project is to accurately measure and assess the levels and characteristics of noise in intensive care units (ICUs) in hospitals. Those levels are in general perceived to be too high and in most cases far above the prescribed levels. This situation is expected to negatively affect both staff and patients in the units.

A second aim of the project is to design, develop and implement strategies and techniques to tackle and reduce the noise in ICUs in order to maintain it below the recommended levels. The methods to be implemented and tested include creating awareness and triggering changes in staff behaviour and operation of equipment in the units, designing and implementing passive means of noise control and developing novel, state of the art active noise control methods and systems.

Lastly, at the final stage of the project, the objective is to assess the impact of the implemented methods and to evaluate the effects on patients and staff in the ICUs.

Noise levels in intensive care units (ICUs) are known to be high. World Health Organisation (WHO) guidelines suggest hospital noise levels should average 35 dBA during the day and 30 dBA at night. Preliminary measurements conducted at Queen Alexandra Hospital in Portsmouth recorded levels just under 60 dBA during the day with peaks above 90 dBA more than 20 times every hour. Although it was quieter at night, peak sounds above 80 dBA were identified up to a 15 times in one hour. Staff activities and alarms are primary sources of disturbance in intensive care units, but noises from other patients and infrastructure also contribute.

Staff and patients may be in a chronic state of alertness when alarms are constantly sounding. Alarms share characteristics with the human scream and tend to activate areas of the brain that recognise danger. Raised sound levels have been associated with increased stress for staff, and non-clinical studies show that noise adversely affects physiology, motivation and general health.
The brain has a limited resource for processing information, and sensory overload caused by high noise levels and complex patient needs can lead to fixation bias and loss of situation awareness among staff. The cognitive cost associated with the subconscious processing of distractor noises limits the brain’s ability to process auditory and visual information. Desensitisation to background noise may reduce staff alertness. Up to 75% of alarms are false alerts, require no immediate action, or are simply ignored. It is also difficult to distinguish serious problems from minor ones as all machine alerts sound urgent to the untrained ear. Alarm fatigue has been cited as a leading hazard faced by hospitals in United States and the Royal College of Anaesthetists’ safe anaesthesia liaison group has prioritised this as an area for improvement in the United Kingdom.

Volunteers exposed to a simulated intensive care environment show disturbed sleep and biochemical markers of stress. A review of intensive care and postoperative sleep studies found that patient’s sleep in intensive care is highly variable, and in two observational studies in Australia and the UK patients had three to five hours of sleep in any 24 hours, with a median duration of unbroken sleep of just three minutes or less.

Disrupted sleep could be a trigger for intensive care unit delirium. Links between psychological disturbances and poor sleep are recognised, and paranoia symptoms can be reduced in psychiatric patients simply by improving sleep. Descriptions of patient experience in intensive care make a harrowing reading. Between 30% and 75% of patients experience at least one delirious episode while in intensive care. These patients tend to have longer hospital stays and long-term health problems after they have been discharged home.
A recent meta-analysis confirms the link between patient exposure to high noise levels and delirium. Ear plugs may be a simple solution. However, ear protection is not suitable for all patients and does not tackle problems of communication, staff wellbeing, or the potential for clinical error. Side rooms offer some protection from disturbances caused by other patients, but patients remain at risk of noise from their own physiological monitoring.

The aim of the proposed project is to tackle the problem and help reduce the levels of noise in ICUs through an approach combining educating staff in ICUs, acoustical modelling and analysis of sources of sound and environment which will lead to development and implementation of both passive and active noise control methods. Noise level measurements will be performed at the start of the project and compared with the results and noise levels achieved following the implementation of the proposed noise reduction methods towards the conclusion of the project. Achieved results will be evaluated and final recommendations made.

Active noise control is the process of reducing the existing sound in the environment by producing and injecting the sound of the same wave shape but opposite phase. This sound mixes and eventually reduces the total sound pressure level in the controlled area. Active noise control and associated control algorithms have been a long-standing research interest of the applicant. It is his firm belief that the problem of noise pollution is only likely to increase and affect human life in even more ways. Finding solution to this problem is therefore essential and will become even more prominent issue in the future. This work can potentially result in an innovative solution and working “zone of silence” prototype that can be modified and applied elsewhere in industry and other areas of human activity thus alleviating the problem of noise in many areas of human life and activity.

The project is ongoing but has been badly affected by the current pandemic. No exchange visits have been possible and measurements planned to take place in the hospitals have been stopped. However, some measurements have been performed in pre-pandemic period and the main findings regarding the nature of the noise reported in the published paper.