Assessment of Noise in the Intensive Care Unit Using Apple Watch

Alarms from monitors, medical devices and staff activities contribute to high noise levels in the Intensive Care Unit (ICU). Excessive levels of noise disrupt sleep patterns in patients admitted to the ICU and may contribute to the development of delirium and post-intensive care syndrome (PICS).

The World Health Organization (WHO) recommends that hospital noise levels should not exceed 35 A-weighted decibels (dBA) during the day and 30 dBA at night. However, daytime noise levels in ICU were found to be above acceptable levels, around 60 dBA. Although polysomnography is the standard for assessing sleep, it is time-consuming and challenging to interpret.

More recent versions of the Apple Watch (Series 4 and 5) take advantage of the internal microphone to regularly sample and track sound levels in the environment. These devices might therefore play a role in monitoring noise levels in the ICU, thanks to their simplicity and popularity. We investigated the feasibility of collecting and analysing data from an Apple Watch to measure noise levels in the ICU.

Accordingly, we exported Health data from the personal Apple Watch of a nurse working in a referral cardiothoracic ICU managing patients after cardiac surgery and those with cardiogenic shock, refractory cardiac arrest, and respiratory failure. The ICU was composed of 14 beds organized in four rooms with two, four, six and two patients. Click here to learn more and to replicate our work. An open-source Jupyter notebook is available on GitHub with a step-by-step guide to analyse data from other ICUs and repeat our experience.

Sound levels were measured in A-weighted decibels (dBA), a widely adopted standard for environmental noise measurement. The A-weighting curve adjusts the sound levels to match the perception of the human ear, less sensitive to low audio frequencies. This technique effectively cuts off the lower and higher frequencies that the average person cannot hear.

The analysis of noise levels in the ICU using an Apple Watch is feasible and easy to perform. We found that overall, noise levels were almost always above the WHO recommended values, consistent with previously published studies. The role of wearable devices to measure noise levels deserves to be further investigated. Apart from healthcare professionals, such devices (provided or personal) might also be worn by patients to more accurately quantify noise levels and compare with the quality of sleep and recovery after ICU discharge. Effective interventions to reduce noise pollution and improve sleep during ICU stay are highly needed.

Our work was published in Critical Care journal in 2020.