Noise in hospital intensive care units—a critical review of a critical topic
Introduction
A hospital intensive care unit (ICU) is designed to treat critically ill patients who need special care and treatment, sometimes at nearly the same extreme level required in an operating room. Thus, although ICUs may be less complex than an operating room, they have become quite sophisticated, with a panoply of medical devices that support an array of physician-specialists, nurses, technicians, and other staff. Noise in ICUs has increased dramatically as a consequence of these changes, and the effect of noise on patients and staff has become an important issue. After all, excessive noise is not only annoying, but can also interfere with the proper performance of medical care. Studies have shown that noise has cardiovascular and physiologic effects that can also affect mental health. Moreover, noise causes sleep disturbances for patients who are vitally in need of sleep; it can also have long-term effects on hearing [1].
A recent review by Choiniere [2], “The Effects of Hospital Noise,” affirms these findings, noting that “research has indicated that there is a positive correlation between hospital noise and physiological responses experienced by patients, the most significant being an increased risk of hypertension and ischemic heart disease.” Another important review by Morrison et al [3] concluded that noise is potentially a significant contributor to higher heart rates, tachycardia, stress, and annoyance in nurses.
It is helpful at this point to take a step back and see what sound levels are thought to be appropriate in a hospital setting. Three key organizations—the World Health Organization (WHO), the International Noise Council, and the Environmental Protection Agency (EPA)—have set standards in this area. Unfortunately, as shown in Table 1, the 3 have established different standards as far as what they recommend for maximum allowable noise for hospital patient room settings [1], [4], [5]. To make sense of the varying nature of the limits recommended by differing agencies and to learn whether and how hospitals might reach those recommended limits, we conducted a literature review of extant research involving noise in hospital ICU environments, as described below. The main thrust of this review is to better understand the different sources of noise in ICU settings and the most effective methods to reduce such noise.
As Table 2 indicates, a noise level of 40 dBA may cause interruption in activities that need concentration. This is a key limiting factor. Nurses must be able to concentrate during their patient caregiving activities, yet if they are working where noise levels are above 40 dBA, there is a higher potential for error. Supporting this concept is the “Levels Document” by the EPA, which states that “the highest noise level that permits relaxed conversation with 100% sentence intelligibility throughout the room is 45 dBA. People tend to raise their voices when the background noise exceeds 45-50 dBA” [7]. Moreover, the “Guidelines for Community Noise” by the WHO, published some quarter century after the EPA standards, states that “for complete sentence intelligibility in listeners with normal hearing, the signal-to-noise ratio (i.e. the difference between the speech level and the sound pressure level of the interfering noise) should be 15–18 dBA. Thus, with a speech level of 50 dBA, (at 1 m distance this level corresponds to a casual speech level of both women and men), the sound pressure level of interfering noise should not exceed 35 dBA” [1]. These are the primary reasons that noise levels must be kept to those recommended by the WHO, the EPA, or the International Noise Council.
Section snippets
Methods
A systematic literature search was done on PubMed and ISI Web of Knowledge during the study to obtain English-language research articles related to the characterization of noise levels in hospital ICUs through mid May 2011. The following keywords were used: ICU, noise and hospital, noise. Abstracts of the original research articles were searched, and only those related to ICU noise analysis were selected for this study. Research articles with the purpose of studying the sources of noise levels,
Results
The literature search found 29 articles related to noise in ICUs. These studies had 3 different foci:
- 1.
studies that simply measured noise amplitude in decibels (15 studies) [2], [3], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20];
- 2.
more complex studies that measured noise amplitude using frequency analysis (4 studies) [21], [22], [23], [24]; and
- 3.
studies that first measured noise levels, then performed a subsequent salutary intervention and, finally, again measured noise
Discussion
No study found that the noise level in the ICU was within the recommended levels by the WHO and/or the EPA. In fact, 1 perceptive study, “How Noisy is Intensive Care?” notes that “background sounds levels were measured in four units and found to be comparable to the hospital cafeteria at noon and only somewhat less noisy than a boiler room” [17]. There was also no consistency in the measurement of noise levels in hospitals with respect to the parameters measured and the duration for which these
Acknowledgments
The authors thank Philip W. Oakley for his support and assistance.
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