Psychoacoustic analysis of noise and the application of earplugs in an ICU: A randomised controlled clinical trial.

Abstract

Patients and medical staff are exposed to high noise levels in ICUs, which may have a negative impact on their health. Due to the diversity of noise sources present, including the operating noise of medical devices, staff conversations and the unwrapping of disposables, noise profiles are varied. Psychoacoustics deals with the analysis of sound, focusing on its effects on physiological perception and stress. The aim of our study was to examine and to classify noise and its psychoacoustic properties in different locations in our ICU at different times. The impact of noise on subjective parameters and stress-related physiological data was also assessed with and without interventional methods. A randomised, controlled, single-blinded clinical trial. University Hospital, from November 2010 to May 2011. One hundred and forty-four patients in the ICU. In the first part, multidisciplinary psychoacoustic measurement was performed on the patients in our ICU. In the subsequent clinical trial, patients were equipped with effective earplugs, less effective earplugs and no earplugs. Thereafter, active noise cancellation headphones with or without sound masking were employed on a third patient population. Cortisol and α-amylase in saliva, skin conductance measures, vital signs, psychoacoustic analyses and two standardised questionnaires [State-Trait Anxiety Inventory (STAI) and Hospital Anxiety and Depression Scale (HADS)] were assessed. In the first part, the mean ± standard deviation (SD) subjective loudness was 9.2 ± 4.0 sone. Although absolute sound pressure level and loudness were lower during the night, the number of loud events increased significantly. Skin conductance in the earplug groups was significantly reduced in comparison to that in the control population but not the active noise reduction groups. Nevertheless, noise reduction was found to be comfortable for most patients. Noise in the ICU is of high clinical relevance. Diverse noise reduction methods, such as earplugs and active noise cancellation, are available. The avoidance of unnecessary noise, however, should be the primary focus. German Clinical Trials Register (DRKS00000534).